Mechanisms of Vascular Disease - The University of Adelaide

2

Mechanisms of Vascular
Disease



Mechanisms of Vascular Disease:

A Reference Book for Vascular Specialists

Robert Fitridge

The University of Adelaide, The Queen Elizabeth Hospital, Woodville, Australia

Matthew Thompson

St George’s Hospital Medical School, London, UK

Published in Adelaide by

The University of Adelaide, Barr Smith Press
Barr Smith Library
The University of Adelaide
South Australia 5005
[email protected]
www.adelaide.edu.au/press

The University of Adelaide Press publishes peer-reviewed scholarly works by staff via Open Access
online editions and print editions.

The Barr Smith Press is an imprint of the University of Adelaide Press, reserved for scholarly works
which are not available in Open Access, as well as titles of interest to the University and its associates.
The Barr Smith Press logo features a woodcut of the original Barr Smith Library entrance.

© The Contributors 2011

This book is copyright. Apart from any fair dealing for the purposes of private study, research,
criticism or review as permitted under the Copyright Act, no part may be reproduced, stored in a
retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise without the prior written permission. Address all inquiries to the Director at
the above address.

This CIP cataloguing for this work is as follows;

Mechanisms of vascular disease : a reference book for vascular surgeons / Robert Fitridge, Matthew
Thompson, [editors].

1. Blood vessels, Diseases.
2. Blood vessels‚ Surgery.

I. Fitridge, Robert
II. Thompson, M. M.

For the full Cataloguing-in-Publication data please contact National Library of Australia:
[email protected]

ISBN (paperback) 978-0-9871718-2-5

Book design: Midland Typesetters
Cover design: Emma Spoehr, based on a diagram by Dave Heinrich of the Medical Illustration and
Media Unit, Flinders Medical Centre
Paperback edition printed by Griffin Press, South Australia

Table of Contents

Contributors vii target  201
Detailed Contents xi Sandeep Prabhu, Rahul Sharma,

 1. Endothelium  1 Karlheinz Peter (Melbourne, Australia)
Paul Kerr, Raymond Tam, 12. Pathogenesis of aortic aneurysms   227
Jonathan Golledge, Guo-Ping Shi,
Frances Plane (Calgary, Canada)
  2. Vascular smooth muscle structure and Paul Norman (Townsville & Perth,
Australia; Boston, USA)
function  13 13. Pharmacological treatment of
David Wilson (Adelaide, Australia) aneurysms  247
 3. Atherosclerosis  25 Matthew Thompson, Janet Powell
Gillian Cockerill, Qingbo Xu (London, UK)
14. Aortic dissection and connective tissue
(London, UK) disorders  255
  4. Mechanisms of plaque rupture   43 Mark Hamilton (Adelaide, Australia)
Ian Loftus (London, UK) 15. Biomarkers in vascular disease   277
  5. Current and emerging therapies in Ian Nordon, Robert Hinchliffe
(London, UK)
atheroprotection  79 16. Pathophysiology and principles
Stephen Nicholls, Rishi Puri of management of vasculitis and
Raynaud’s phenomenon  295
(Cleveland, USA) Martin Veller (Johannesburg,
  6. Molecular approaches to South Africa)
17. SIRS, sepsis and multiorgan
revascularisation in peripheral vascular failure  315
disease  103 Vishwanath Biradar, John Moran
Greg McMahon, Mark McCarthy (Adelaide, Australia)
18. Pathophysiology of reperfusion
(Leicester, UK) injury  331
  7. Biology of restenosis and targets for Prue Cowled, Robert Fitridge
(Adelaide, Australia)
intervention  115 19. Compartment syndrome  351
Richard Kenagy (Seattle, USA) Edward Choke, Robert Sayers,
 8. Vascular arterial haemodynamics  153 Matthew Bown (Leicester, UK)
Michael Lawrence-Brown, Kurt 20. Pathophysiology of pain   375
Stephan Schug, Helen Daly,
Liffman, James Semmens, Ilija Kathryn Stannard (Perth, Australia)
Sutalo (Melbourne & Perth, Australia)
 9. Physiological haemostasis  177
Simon McRae (Adelaide, Australia)
10. Hypercoagulable states  189
Simon McRae (Adelaide, Australia)
11. Platelets in the pathogenesis of vascular
disease and their role as a therapeutic

v

vi Mechanisms of Vascular Disease

21. Postamputation pain  389 26. Pathophysiology and principles of
Stephan Schug, Gail Gillespie management of the diabetic foot  475

(Perth, Australia) David Armstrong, Timothy Fisher,
22. Treatment of neuropathic pain  401 Brian Lepow, Matthew White,
Stephan Schug, Kathryn Stannard Joseph Mills (Tucson, USA)

(Perth, Australia) 27. Lymphoedema – Principles, genetics
23. Principles of wound healing  423 and pathophysiology  497
Gregory Schultz, Gloria Chin,
Matt Waltham (London, UK)
Lyle Moldawer, Robert Diegelmann 28. Graft materials past and future  511
(Florida, USA) Mital Desai, George Hamilton
24. Pathophysiology and principles of
varicose veins  451 (London, UK)
Andrew Bradbury (Birmingham, UK) 29. Pathophysiology of vascular graft
25. Chronic venous insufficiency and leg
ulceration: Principles and vascular infections  537
biology  459 Mauro Vicaretti (Sydney, Australia)
Michael Stacey (Perth, Australia)
Index  549

List of Contributors

David G Armstrong Prue Cowled
The University of Arizona Department of Surgery
Southern Arizona Limb Salvage Alliance University of Adelaide
Tucson, AZ The Queen Elizabeth Hospital
USA Woodville, SA
Australia
Vishwanath Biradar
Intensive Care Unit Helen Daly
The Queen Elizabeth Hospital Royal Perth Hospital
Woodville, SA Perth, WA
Australia Australia

Matthew Bown Mital Desai
Department of Vascular Surgery University Department of Vascular Surgery
University of Leicester Royal Free Hospital
Leicester University College
UK London
UK
Andrew W Bradbury
University Department of Vascular Surgery Robert F Diegelmann
Birmingham Heartlands Hospital Department of Biochemistry
Birmingham Medical College of Virginia
UK Richmond, VA
USA
Edward Choke
Department of Vascular Surgery Timothy K Fisher
University of Leicester Rashid Centre for Diabetes and Research
Leicester Sheikh Khalifa Hospital
UK Ajmon
UAE

Gillian Cockerill Robert A Fitridge
Department of Clinical Sciences Department of Surgery
St George’s Hospital Medical School University of Adelaide
London The Queen Elizabeth Hospital
UK Woodville, SA

Australia

vii

viii Mechanisms of Vascular Disease

Gail Gillespie Michael MD Lawrence-Brown
Royal Perth Hospital Curtin Health Innovation Research
Perth, WA
Australia Institute
Curtin University
Jonathan Golledge Perth, WA
Vascular Biology Unit Australia
School of Medicine & Dentistry
James Cook University Brian Lepow
Townsville, QLD The University of Arizona
Australia Department of Surgery
Southern Arizona Limb Salvage Alliance
George Hamilton Tucson, AZ
University Department of Vascular Surgery USA
Royal Free Hospital
University College Kurt Liffman
London CSIRO Material Science & Engineering
UK
and School of Mathematical Sciences
Mark Hamilton Monash University
Department of Surgery Melbourne, Vic
University of Adelaide Australia
The Queen Elizabeth Hospital
Woodville, SA Ian Loftus
Australia Department of Vascular Surgery
St George’s Hospital
Robert J Hinchliffe London
St George’s Vascular Institiute UK
St George’s Hospital
London Mark J McCarthy
UK Department of Surgery and Cardiovascular

Richard D Kenagy Sciences
Department of Surgery University of Leicester
University of Washington Leicester
Seattle, WA UK
USA
Greg S McMahon
Paul Kerr Department of Surgery and Cardiovascular
Department of Pharmacology
University of Alberta Sciences
Alberta University of Leicester
Canada Leicester
UK

Simon McRae
Adult Haemophilia Treatment Centre
SA Pathology
Adelaide, SA
Australia

List of Contributors ix

Joseph L Mills Janet T Powell
The University of Arizona Imperial College
Southern Arizona Limb Salvage Alliance London
Tucson, AZ UK
USA
Sandeep Prabhu
Lyle Moldawer Baker IDI Heart & Diabetes Institute
Department of Surgery Alfred Hospital
University of Florida Melbourne, Vic
Gainesville, FL Australia
USA
Rishi Puri
John L Moran The Heart and Vascular Institute
Faculty of Health Sciences Cleveland Clinic
University of Adelaide Cleveland, OH
The Queen Elizabeth Hospital USA
Woodville, SA
Australia Stephan A Schug
Royal Perth Hospital
Stephen Nicholls Perth, WA
The Heart and Vascular Institute Australia
Cleveland Clinic
Cleveland, OH Gregory S Schultz
USA Department of Obstetrics and Gynaecology
University of Florida
Ian M Nordon Gainesville, FL
St George’s Vascular Institiute USA
St George’s Hospital
London Rahul Sharma
UK Baker IDI Heart & Diabetes Institute
Alfred Hospital
Paul E Norman Melbourne, Vic
School of Surgery Australia
University of WA
Fremantle, WA Guo-Ping Shi
Australia Department of Cardiovascular Medicine
Brigham & Women’s Hospital
Karlheinz Peter Harvard Medical School
Baker IDI Heart & Diabetes Institute Boston, MA
Melbourne, Vic USA
Australia
Michael Stacey
Frances Plane University Department of Surgery
Department of Pharmacology Fremantle Hospital
University of Alberta Fremantle, WA
Alberta Australia
Canada

x Mechanisms of Vascular Disease

Ilija D Sutalo Matt Waltham
CSIRO Material Science & Engineering Academic Department of Surgery
St Thomas’ Hospital
and Curtin Health Innovation London
Research Instutute UK
Curtin University
Highett, Vic Matthew L White
Vascular and Endovascular Surgery
Raymond Tam University of Arizona
Department of Pharmacology Tucson, AZ
University of Alberta USA
Alberta
Canada David P Wilson
School of Medical Sciences
Matthew Thompson Discipline of Physiology
St Georges Hospital Medical School University of Adelaide
London Adelaide SA
UK Australia

Martin Veller Qingbo Xu
Department of Surgery Department of Cardiology
University of Witwatersrand Kings College
Johannesburg University of London
South Africa UK

Mauro Vicaretti
Department of Vascular Surgery
Westmead Hospital
Westmead, NSW
Australia

Detailed Contents

Chapter 1 – Endothelium Smooth muscle proliferation and vascular
remodeling 20
Paul Kerr, Raymond Tam, Frances Plane
Summary 22
Introduction 1 References
Endothelium-dependent regulation of
Chapter 3 – Atherosclerosis
vascular tone 2
Angiogenesis 7 Gillian Cockerill, Qingbo Xu
Haemostasis 8
Inflammation 9 Introduction 25
Conclusions 10 Atherosclerotic lesions 26
References
Fatty streaks
Chapter 2 – Vascular Plaque or atheroma
Smooth Muscle Structure Hypercholesterolemia and oxidised-LDL
and Function
27
David Wilson High-density lipoproteins role in

Introduction 13 atheroprotection 28
Smooth muscle (vascular) structure Hypertension and biomechanical stress
Cytoskeleton 14
Contractile myofilament 29
Functional regulation of vascular smooth Biomechanical stress-induced cell death

muscle: Neuronal, hormonal, receptor 30
mediated 15 Biomechanical stress and inflammation
Smooth muscle function 17
Myofilament basis of smooth muscle 31
contraction and relaxation Biomechanical stress-induced smooth
Smooth muscle contraction and
muscle cell proliferation 32
relaxation 18 Infections and heat shock proteins
Ion channels important in the regulation
Infections
of smooth muscle function Heat shock proteins 33
Regulation of cellular Ca2+ Infections and HSP expression
Sources of cytosolic Ca2+ entry 19 Infections, sHSP and innate immuntiy
Potassium channels
Endothelial regulation of smooth muscle 34
Immune responses 36
vasodilatation 20
MHC class II antigens and T cells
Oxidised LDL as a candidate antigen
HSP60 as a candidate antigen 37
B2-gylcoprotein Ib as a candidate antigen
Inflammation

xi

xii Mechanisms of Vascular Disease

C-reactive protein 38 Stephen Nicholls, Rishi Puri
CD40/CD40L
Summary and perspectives 39 Background 79
References Pathology
Risk factor modification 80
Chapter 4 – Mechansims of
Plaque Rupture Statins, LDL lowering and C-reactive
protein
Ian Loftus
The complexity of HDL 84
Introduction 43 The controversy of trigylcerides 87
Evidence for the ‘plaque rupture theory’ Hypertension
Risk factor modification in the diabetic
44
Coronary circulation patient 89
Cerebral circulation Glycaemic control
The role of individual components of the Global risk factor reduction in diabetics

arterial wall 91
The endothelium 45 The metabolic syndrome 92
The lipid core 47 Future targets 93
The cap of the plaque 49 Conclusion
Smooth muscle cells and collagen References 94

production 50 Chapter 6 – Molecular
Macrophages and collagen degradation approaches to
revascularisation in
51 peripheral vascular disease
The vessel lumen 56
The role of angiogenesis in plaque rupture Greg S McMahon, Mark J McCarthy
The role of infectious agents in plaque
Introduction 103
rupture 57 Mechanisms of vascular growth
Risk prediction of plaque instability 58
Vasculogenesis
Imaging Angiogenesis 104
Blood markers 59 Neovessel maturation 105
Therapy aimed at plaque stabilisation Microvascular network maturation 106
HMG Co-A reductase inhibitors 60 Arteriogenesis
MMP inhibition Therapeutic induction of vascular growth
Tissue inhibitors of metalloproteinases
107
(TIMPs) 61 Delivery of molecular activators of
Synthetic MMP inhibitors
Doxycycline vascular growth
ACE inhibitors Angiogenic activators 108
Summary 62 Arteriogenic activators 109
References 63 Clinical trials for angiogenic therapy of

Chapter 5 – Current and peripheral vascular disease
emerging therapies in Conclusions 110
atheroprotection References

Detailed Contents xiii

Chapter 7 – Biology of Laplace’s law of wall of tension 154
restenosis and targets for Newtonian fluid 155
intervention Non-Newtonian fluid
Poiseuille flow 158
Richard Kenagy Bernoulli’s equation
Young’s modulus and pulsatile flow 159
Introduction 115 Mass conversion 161
Mechanisms of restenosis Reynold’s number
Arterial dissection, collateral circulation
Thrombosis 116
Remodelling and competing flows 163
Intimal hyperplasia 123 Shear stress and pressure 164
Forces on graft systems 165
Sequence of events after injury
Origin of intimal cells 125 Case 1 – The cylindrical graft 168
Inflammation 126 Case 2 – The windsock graft
Role of ECM production 127 Case 3 – The curved graft 169
The contribution of specific factors to Case 4 – The symmetric bifurcated graft
restenosis Computational modelling 170
Growth factors/cytokines Recent development and future directions
Inhibitors 128
Coagulation and fibrinolytic factors 129 171
Matrix metalloproteinases Conclusions 172
Extracellular matrix/receptors References 173
Targets for intervention 130
Intracellular signalling molecules Chapter 9 – Physiological
mTOR and microtubules haemostasis
Transcription factors
miRNA 131 Simon McRae
Inflammation targets
Brachytherapy Introduction 177
Extracellular targets and cell-based Primary haemostasis

therapies Platelets
Angiotensin pathway Platelet adhesion
Cell-based therapies 132 Platelet activation and shape change
Differential effects on endothelium and 179

SMCs Platelet aggregation 180
Delivery devices Interactions between primary and
Prevention versus reversal of restenosis
Conclusions 133 secondary haemostasis 181
References 134 Secondary haemostasis
The coagulation cascade 182
Chapter 8 – Vascular
arterial haemodynamics Initiation 183
Amplification
Michael Lawrence Brown, Kurt Liffman, Propagation 184
James Semmens, Ilija Sutalo Normal inhibitors of coagulation
Fibrinolysis 185
Introduction 153 Conclusions 186
References

xiv Mechanisms of Vascular Disease

Chapter 10 – vascular disease and their
Hypercoagulable states role as a therapeutic
target
Simon McRae
Sandeep Prabhu, Rahul Sharma,
Introduction 189 Karlheinz Peter
Classification of thrombophilia
Introduction 201
Inherited thrombophilia 190 Platelet function – Adhesion and
Type 1 conditions
Antithrombin deficiency activation
Protein C and Protein S deficiency Platelet adhesion 202
Type 2 conditions 191 Platelet activation 203
Factor V Leiden Mediators of platelet activation and
The prothrombin (G20210A) gene
mutation ‘outside in’ signalling
FVL/PGM compound heterozygotes Thrombin and collagen 204
Other inherited conditions Adenosine diphosphate (ADP)
Thromboxane A2 (TXA2)
Acquired thrombophilia 192 Adrenaline 206
Antiphospholipid antibodies Second messenger systems 207
Heparin induced thrombocytopenia Physiological consequences of platelet
Myeloproliferative disorders 193
activation
Potential reasons for performing The GP IIb/IIIa receptor and ‘inside-
thrombophilia testing
out’ signalling
Patients with venous thrombosis and Granule exocytosis 208
their relatives Activation-induced conformational

Providing an understanding of the change of platelets
aetiology of a thrombotic event Platelets and atherosclerosis 209

Determining risk of recurrence and Role of platelets in the initiation of the
therefore optimal duration of atherosclerosis
anticoagulation 194
Role of the platelets in the progression of
Determining the need for primary the atherosclerosis
prophylaxis in asymptomatic
family members 195 Role of platelets in vulnerable plaques and
plaque rupture
Making decisions regarding the use of
the oral contraceptive pill 196 Current and future anti-platelet agents
210
Determining the need for
thromboprophylaxis during Aspirin (salicylic acid)
pregnancy Thienopyridines 211

Patients with arterial thrombosis Clopidogrel
Potential detrimental effects of Prasugrel 213
Ticlopidine
thrombophilia testing 197 Ticagrelor
Conclusion GPIIb/IIIa Antagonists
References Other anti-platelet agents and promising

Chapter 11 – Platelets new deleopments 214
in the pathogenesis of Platelet function testing 215

Light-transmission aggregometry

Detailed Contents xv

Whole blood aggregometry 217 response 249
VerifyNow® Assay Non-steroidal anti-inflammatories
Flow cytometry 218 Matrix metalloproteinase (MMP)
References
inhibition
Chapter 12 – Pathogenesis Anti-chlamydial therapy 250
of aortic aneurysms Drugs acting on the renin/angiotensin axis
HMG Co-A reductase inhibitors 251
Jonathan Golledge, Guo-Ping Shi, The future – Data from recent
Paul E Norman
experimental studies
Introduction 227 References
Differences between thoracic and
Chapter 14 –
abdominal aortic aneurysms 228 Pathophysiology of Aortic
Summary of current theories and stages of Dissection and Connective
Tissue Disorders
AAA evolution
Atherosclerosis and AAA Mark Hamilton
Immune mechanisms in AAA 229
Extracellular matrix dysfunction 232 Introduction 255
Infection 233 Embryology of thoracic aorta and arch
Biomechanical forces vessels
Angiogenesis Haemodynamics of thoracic compared to
Intra-luminal thrombus abdominal aorta 257
Extracellular matrix proteolysis 234 Sizes of normal aorta
Genetics 236
AAA rupture 237 Classification of aortic syndromes
Acute/Chronic
Biomechanical factors in aneurysms DeBakey classification of class 1
rupture dissection – Type 1, 2, and 3
Stanford classification 258
The role of enzymes in AAA rupture European task force
Role of intraluminal thrombus in
Pathogenesis of thoracic aortic dissection
aneurysm rupture 238 Classical thoracic aortic dissection (class 1
Future research dissection) 260
References Intramural haematoma (class 2 aortic
dissection) 261
Chapter 13 – Penetrating aortic ulcer (class 4 aortic
Pharmacological dissection) 262
treatment of aneurysms
Complications of acute aortic syndromes
Matthew Thompson, Janet T Powell 263

Background 247 Visceral ischaemia /malperfusion
Screening programmes syndromes
Pathophysiology 248
Therapeutic strategies Fate of the false lumen
Aneurysmal degeneration and rupture
Beta blockade
Modification of the inflammatory 264
Connective tissue disorders and acute

aortic syndromes

xvi Mechanisms of Vascular Disease

Marfan syndrome Chapter 16 –
Fibrillin and Marfan syndrome 265 Pathophysiology and
The role of transforming growth factor principles of management
beta in development of the vascular of vasculitis and Raynaud’s
system in health and disease 266 phenomenon

Ehlers-Danlos syndrome 267 Martin Veller
Diagnosis of Ehlers-Danlos syndrome
268 Vasculitides 295
Introduction
Loeys-Deitz syndrome 270 Classification of vasculitides 296
Familial thoracic aortic aneurysm disease Clinical presentation of vasculitides
Investigations of vasculitides
271 Principles of treatment of vasculitides
Bicuspid aortic valve 273
Turners Syndrome 297
Summary 274 The vasculitides of specific interest to
Reference list
vascular surgeons 298
Chapter 15 – Biomarkers in Giant cell arteritis
vascular disease Takayasu’s arteritis 299
Thromboangitis obliterans (Buerger’s
Ian M Nordon, Robert J Hinchliffe
disease) 300
Introduction 277 Behcet’s disease 301
What is a biomarker? Polyarteritis nodosa 302
Types of biomarkers Vasculitides secondary to connective

A classical clinical example 278 tissue diseases 303
Potential value of biomarkers in vascular Systemic lupus erythematosus (SLE)
Antiphospholipid antibody syndrome
disease 279
Biomarker discovery steps 280 (APS) 304
AAA biomarkers Rheumatoid arthritis 305
Scleroderma
Circulating extracellular matrix markers Infective vasculitides 306
281 Human immunodeficiency virus (HIV)
Pathophysiology and principles of
Matrix-degrading enzymes 283 Raynaud’s phenomenon 307
Proteins associated with thrombosis Prevalence of Raynaud’s phenomenon
Markers of inflammation 284
Biomarkers of AAA rupture 285 308
Biomarkers following endovascular repair Clinical findings in Raynaud’s
Inflammation 287
Lipid accumulation phenomenon 309
Apoptosis Diagnosis of Raynaud’s phenomenon
Thrombosis Prognosis 310
Proteolysis 288 Treatment
Challenges in biomarkers discovery Recommendations 311
Future work References 312
Conclusion 289
References Chapter 17 – SIRS, sepsis and

Detailed Contents xvii

multiorgan failure Eicosanoids 334
Nitric Oxide 335
Vishwanath Biradar, John Moran Endothelin 336
Cytokines
Epidemiology 315 Neutrophil and endothelial interactions
Historical perspectives and definition 316
Risk factors for sepsis 317 338
Complement activation 340
Causative agents Tissue destruction 341
Pathophysiology of sepsis Proteases and metalloproteinases
Apoptotic cell death during ischaemia-
innate immunity and toll-like receptors
(TLRs) 319 reperfusion injury
No-reflow phenomenon 342
Proinflammatory response Therapeutic approaches to IRI
Coagulation cascade Ischaemic preconditioning
Multiorgan dysfunction syndrome Ischaemic post-conditioning 343
Conditioning effects of volatile
(MODS) 320
Epithelial and endothelial dysfunction anaesthetics
Immune suppression and apoptosis Pharmacological treatments 344
Sepsis, circulatory failure and organ Summary 345
References
dysfunction
Management 322 Chapter 19 – Compartment
Syndrome
Steroids 323
Recombinant human activated protein C Edward Choke, Robert Sayers, Matthew
Bown
(rhAPC) 324
Glucose control 325 Definition 351
Renal replacement therapy Acute limb compartment syndrome
3-hydroxy-3-methylglutaryl-coenzyme
Incidence
reductase inhibitors (HMG-CoA) Anatomy/physiology 352
326 Aetiology/pathophysiology
Other adjuvant therapies in sepsis Clinical presentation 354
Cytokines and anticytokine therapies Investigation 355
Pooled immunoglobulin (IVIG) Treatment 357
Acute respiratory distress syndrome Complication of LCS 359
(ARDS) 327 Outcome 360
References Acute abdominal compartment syndrome
Incidence 361
Chapter 18 – Aetiology
Pathophysiology of Pathological effects of raised intra-
reperfusion injury
abdominal pressure 362
Prue Cowled, Rob Fitridge Clinical presentation 363
Investigation
Introduction 331 Treatment 364
Ischaemia Complications of surgical decompression

ATP and mitochondrial function
Gene expression during ischaemia 332
Reperfusion 333
Reactive oxygen species

xviii Mechanisms of Vascular Disease

Outcome 367 Peripheral neuropathies
References 368 Central neuropathies 385
References
Chapter 20 –
Pathophysiology of Pain Chapter 21 –
Post-amputation pain
Stephan Schug, Helen Daly, Kathryn
Stannard Stephan Schug, Gail Gillespie

Introduction 375 Introduction 389
Peripheral mechanisms Classification and incidence of post-

Nociception/transduction amputation pain syndromes
Conduction 376 Stump pain
Spinal cord mechanisms Phantom sensation 390
Ascending systems 377 Phantom limb pain
Descending control Pathophysiology of post-amputation pain
Pain modulation 378
Peripheral sensation syndromes
Central sensitisation in the dorsal horn Peripheral factors
Neuropathic pain 379 Spinal factors 391
Mechanisms of neuropathic pain Supraspinal factors
Current pathophysiological model of post-
Peripheral mechanisms
Spontaneous ectopic discharge amputation pain syndromes 392
Altered gene expression Prevention of post-amputation pain
Spared sensory neurons
Involvement of the sympathetic nervous Perioperative lumbar epidural blockade
Peripheral nerve blockade 393
system 380 NMDA antagonists
Collateral sprouting Evaluation of the patient with post-
Effects of bradykinin
Central mechanisms amputation pain syndromes
Wind up Examination
Central sensitization 381 Therapy of post-amputation pain
Central disinhibition
Expansion in receptive field size syndromes 394
Calcitonin
(recuruitment) Ketamine
Immediate early gene expression Analgesic and Co-analgesic compounds
Anatomical re-organisation of the spinal
Opioids 395
cord Gabapentin
Contribution of glial cells to pain Clonazepam
Lidocaine
conditions 382 Carbamazepine
Symptoms of neuropathic pain Tricyclic antidepressants (TCA)
Selective serotonin reuptake inhibitors
Stimulus-dependent pain Baclofen
Stimulus-independent pain 383 Capsaicin
Sympathetically maintained pain (SMP) Symptomatic treatment of pain
Neuropathic pain syndromes
components 396
Neuropharmacological therapies

Detailed Contents xix

Invasive therapies Phenytoin
Electroconvulsive therapy (ECT) Lamotrigene
Nerve blockade Recommendations for clinical use of
Spinal cord stimulation
Implantable intrathecal delivery systems anticonvulsants as analgesics
Dorsal root entry zone (DREZ) lesions Local anaesthetics and antiarrhythmics
Psychological therapy 397
409
Future aims Mechanism of action
References Lignocaine
Mexiletine
Chapter 22 – Treatment of
neuropathic pain Recommendations for clinical use
of lignocaine and mexiletine in
Stephan Schug, Kathryn Stannard neuropathic pain

Introduction 401 N-methyl-D-aspartate-receptor
Principles of treatment antagonists (NMDA)
Pharmacological treatment 402
Ketamine 410
Opioids Other NMDA antagonists
Recommendations for clinical use of Miscellaneous compounds for systemic
opioids
use
Tramadol Clonidine
Mechanism of action
Efficacy 403 Efficacy
Adverse effects Baclofen
Recommendations for clinical use of Levodopa 411
tramadol in neuropathic pain Cannabinoids
Topical treatments
Antidepressants
Tricyclic antidepressants (TCAs) Lignocaine 5% medicated plaster
Mechanism of action 404 Capsaicin 412
Adverse effects
Selective serotonin re-uptake inhibitors Mechanism of action
(SSRIs) Efficacy
Serotonin/Noradrenaline reuptake Non-pharmacological therapy
inhibitors (SNRIs) 405 Transcutaneous electrical nerve
Recommendations for clinical use of stimulation (TENS)
antidepressants as analgesics Spinal cord stimulation (SCS) 413
Sympathetic nerve blocks
Anticonvulsants Neurosurgical destructive techniques
Mechanism of action 406 Cognitive behavious therapy
Individual medications References 414
Clonazepam
Gabapentin Chapter 23 – Principles of
Pregabalin 407 wound healing
Carbamazepine
Sodium valproate 408 Gregory Schultz, Gloria Chin,
Lyle Moldawer, Robert Diegelmann

Introduction 423
Phases of acute wound healing

Haemostasis

xx Mechanisms of Vascular Disease

Inflammation 426 Varicose veins 453
Neutrophils 427 Valvular abnormalities
Macrophages 428 Muscle pump failure 455
Venous recirculation
Proliferative phase 429 Recurrent varicose veins
Fibroblast migration 430
Collagen and extracellular matrix New varicose veins
production Persistent varicose veins
Angiogenesis 431 True recurrent varicose veins 456
Granulation 432 Cellular and molecular biology of varicose
Epithelialization
Remodelling 433 veins
Conclusion 457
Summary of acute wound healing 435 References
Comparison of acute and chronic wounds
Chapter 25 – Chronic
Normal and pathological responses to venous insufficiency and
injury leg ulceration: Principles
and vascular biology
Biochemical differences in the molecular
environments of healing and chronic Michael Stacey
wounds 436
Definitions 459
Biological differences in the response of Chronic venous insuffiency
chronic wound cells to growth factors Leg ulceration
439 Assessment of cause of leg ulceration
460
From bench to bedside Epidemiology 461
Role of endocrine hormones in the Pathophysiology
regulation of wound healing Venous abnormality
Molecular basis of chronic non-healing Effect of ambulatory venous hypertension
wounds on the tissues in the leg 463
Chronic venous stasis ulcers 441 Influence of venous disease on the wound
Pressure ulcers healing process 465
Genetic associations with venous
Future concepts for the treatment of ulceration 466
chronic wounds 442
Assessment of venous function 467
Bacterial biofilms in chronic wounds Treatment of venous ulceration
443
Compression therapy
Conclusion 445 Dressings 468
References Surgery
Prevention of venous ulcer recurrence
Chapter 24 –
Pathophysiology and 470
principles of management Sclerotherapy and other techniques to
of varicose veins
obliterate surface and perforating
Andrew Bradbury veins
Other therapies 471
Introduction 451 References
Anatomy
Histology 452
Physiology

Detailed Contents xxi

Chapter 26 – Chapter 27 – Lymphoedema
Pathophysiology and – Principles, genetics and
principles of management pathophysiology
of the diabetic foot
Matt Waltham
David Armstrong, Timothy Fisher, Brian
Lepow, Matthew White, Joseph Mills Introduction 497
Classification of lymphoedema
Introduction 475
Pathophysiology of the diabetic foot 476 Classification of primary lymphoedema
498
Neuropathy
Structural abnormalities/gait The genetics of lymphangiogensis in
primary lymphoedema 500
abnormalities
Angiopathy 478 Milroy’s disease
Diagnosis Lymphoedema – distichiasis syndrome
History and rapid visual screening
Neurological examination 479 501
Hypotrichosis – lymphoedema –
Monofilament testing
Vibration testing telangiectasia syndrome 502
Dermatologic examination 480 Meige disease (primary non-syndromic
Anatomy of occlusive disease – vascular
lymphoedema)
examination Other primary lymphoedema disorders
Prediction of wound healing: assessment
503
of perfusion 481 Structure and development of the
Arterial imaging
Soft tissue imaging 482 lymphatic circulation
Classification systems 483 Clinical aspects of lymphoedema 505
Diabetes mellitus foot risk classification Summary
University of Texas wound classification References

system Chapter 28 – Graft
Clinical problems and principles of materials past and future

management 484 Mital Desai, George Hamilton
Ulceration
The pathophysiology of graft healing 511
Epidemiology and risk factors The peri-anastomotic area
Offloading Healing of prosthetic grafts 512
Non-vascular surgical treatment 485 The healing process of the anastomosis
Class I – Elective 486 Graft porosity and permeability
Class II – Prophylactic
Class III – Curative Physical properties of prosthetic materials
Class IV – Emergency (urgent) 514
Post-operative management
Infections 487 Tubular compliance
Charcot arthopathy Anastomotic compliance mismatch
Prevention 490 The compliance hypothesis of graft failure
Conclusion 492 Synthetic grafts 515
References Newer developments of Dacron grafts
Modifications and newer developments of

PTFE grafts 517
Polyurethane grafts

xxii Mechanisms of Vascular Disease

Newer developments of polyurethane Chapter 29 –
vascular grafts 518 Pathophysiology of
vascular graft infections
Biological vascular grafts 519
Newer developments of biological Mauro Vicaretti
vascular grafts 520
Introduction 537
Prosthetic graft modifications Natural history of prosthetic vascular graft
Modifications to reduce graft infection
Modifications to improve patency 521 infections
Nanocomposite grafts Mechanism of graft contamination at

Endothelial cell seeding 522 operation 538
Single stage seeding Pathogenesis of graft infections
Two stage seeding Bacteriology of vascular graft infections
Investigations for detection of prosthetic
Vascular tissue engineering
Non-degradable polymer and cell seeding graft infections 539
523 History and physical examination
Bioresorbable and biodegradable polymers Laboratory investigations
Combined bioresorbable and tissue Diagnostic imaging 540
engineered grafts 524 Management of prosthetic graft infections
Mechanical conditioning of seeded Prevention
vascular cells Reduction of prosthetic vascular graft
Alternative scaffolds
Tissue-engineered grafts 525 infection with rifampicin bonded
gelatin sealed Dacron 541
Graft materials for aortic endografts 526 Established infection
The future Antibiotic therapy
References 527 Operative management
Conclusion 542
References

Acknowledgements

The Editors gratefully acknowledge the outstanding contributions of each Author involved
in this reference book. We would also like to acknowledge the invaluable efforts of
Ms Sheona Page who has worked tirelessly on this project. We would also like to thank
Prue Cowled PhD and Ms Cayley Wright for their assistance.

xxiii

Abbreviation List

a1-PI a1-protease inhibitor
5-HT 5-Hydroxytryptamine/Serotonin
AAA Abdominal aortic aneurysm
AAS Acute aortic syndrome
AAV Adeno-associated viruses
ACE Angiotensin converting enzyme
ACS Acute coronary syndrome
ACS Abdominal compartment syndrome
ACTH Adrenocorticotropic hormone
ADAMTS A disintegrin and metalloproteinase with thrombospondin motifs
ADP Adenosine diphosphate
AIDS Acquired immune deficiency syndrome
ALI Acute lung injury
AMP Adenosine monophosphate
AMPA α-amino-3 hydroxy-5-methylisoxazole
ANA Anti-nuclear antibody
ANCA Anti-neutrophil cytoplasmic antibody
AOD Aortic occlusive disease
AP1 Activated protein 1
APC Activated protein C
APC Antigen presenting cell
APLAS Antiphospholipid antibody syndrome
ApoAI Apolipoprotein AI
ApoE Apolipoprotein E
APS Antiphospholipid antibody syndrome
APTT Activated partial thromboplastin time

xxiv

Abbreviation List xxv

ARDS Acute respiratory distress syndrome
AT Antithrombin
ATP Adenosine triphosphate
AVP Ambulatory venous thrombosis
b2-GPI b2-glycoprotein Ib
bFGF Basic fibroblast growth factor
BKCa Large conductance calcium activated potassium channel
BMPs Bone morphogenetic proteins
BMS Bare metal stent
CAD Coronary artery disease
CaM Calmodulin
CAM Cell adhesion molecule
cAMP Cyclic adenosine monophosphate
CCK Cholecystokinin
cGMP Cyclic guanine monophosphate
CD Cluster of differentiation
CD40L Cluster of differentiation 40 ligand
CEA Carotid endarterectomy
CETP Cholesteryl ester transfer protein
CFD Computational fluid dynamics
CG Cationized gelatin
CGRP Calcitonic gene regulated peptide
CHD Coronary heart disease
CI Confidence interval
CIMT Carotid intimal-media thickness
c-JNK c-Jun N-terminal kinase
CK-MB Creatinine kinase (Myocardial specific)
CNCP Chronic noncancer pain
cNOS Constitutive nitric oxygen synthase enzyme
COX-1 Cyclooxygenase-1
COX-2 Cyclooxygenase-2
CROW Charcot restraint orthotic walker
CRRT Continuous renal replacement therapy

xxvi Mechanisms of Vascular Disease

CRP C-reactive protein
CRPS Complex regional pain syndromes
CT Computational tomography
CTA Computed tomographic angiography
CTD Connective tissue disorders
CTGF Connective tissue growth factor
CYP Cytochrome P450
CVD Cardiovascular disease
CVI Chronic venous insufficiency
DAG Diacylglycerol
DES Drug-eluting stent
DRG Dorsal root ganglion
DNA Deoxyribonucleic acid
DSA Digital subtraction arteriography
DTS Dense tubular system
DVT Deep vein thrombosis
EC Endothelial cell
ECM Extracellular matrix
EDCF Endothelium-derived contracting factor
EDH Endothelium-dependent hyperpolarisation
EDS Ehlers-Danlos syndrome
EET Epoxyeicosatrienoic acids
ELAM-1 Endothelial-leukocyte adhesion molecule-1
ELG Endoluminal grafts
ELISA Enzyme linked immunosorbent assay
EK Equilibrium potential
EM Membrane potential
eNOS Endothelial nitric oxide synthase enzyme
EPC Endothelial progenitor cells
EPCR Endothelial protein C receptor
ePTFE Expanded polytetrafluoroethylene
ERK Extracellular signal-regulated kinase
ESR Erythrocyte sedimentation rate

Abbreviation List xxvii

ET Essential thrombocytosis
ET-1 Endothelin 1
EVAR Endovascular aortic aneurysm repair
EVLA Endovenous LASER ablation
FDA Food and drug administration
FDPs Fibrin degradation products (soluble)
FGF Fibroblast growth factor
FGF-2 Fibroblast growth factor 2
FMN Flavin mononucleotide
FVL Factor V Leiden
GABA Gamma-aminobutyric acid
GABA B Gamma-aminobutyric acid subtype B
G-CSF Granulocyte colony stimulating factor
GMCSF Granulocyte-macrophage colony stimulating factor
GP Glycoprotein
GPCR G-protein coupled receptor
GSV Great saphenous vein
HDL High density lipoprotein
HDL-C High density lipoprotein cholesterol
HIF Hypoxia inducible factor
HIT Heparin induced thrombocytopenia
HIV Human immunodeficiency virus
HLA Human leukocyte antigen
HMG Co-A Hydroxymethylglutaryl coenzyme-A
HMW High molecular weight
HPETE Hydroperoxyeicosatetraenoic acid
HETE Hydroxyeicosatetraenoic acids
HR Hazard ratio
hsCRP High-sensitive C-reactive protein
HSP Heat shock protein
HUV Human umbilical vein
IAH Intra-abdominal hypertension

xxviii Mechanisms of Vascular Disease

IAP Intra-abdominal pressure
IAPP Intra-abdominal perfusion pressure
ICAM-1 Inter-cellular adhesion molecule-1
ICAM-2 Inter-cellular adhesion molecule-2
ICP Intra-compartmental pressure
ICU Intensive care unit
IFN Interferon
IGF-1 Insulin-like growth factor-1
IHD Ischemic heart disease
IL Interleukin
IL-1 Interleukin-1
IL-1α Interleukin-1 alpha
IL1-β Interleukin-1 beta
IL-6 Interleukin-6
IL-8 Interleukin-8
ILT Intraluminal thrombus
IKCa Intermediate conductance calcium-activated potassium channels
IMH Intramural haematoma
IMP Inosine monophosphate
iNOS Inducible nitric oxide synthase enzyme
IP(3) 1,4,5-inositol triphosphate
IRI Ischemia reperfusion injury
IVIG Intravenous pooled immunoglobulin
IVUS Intravascular ultrasound
KGF Keratinocyte growth factor
KGF-2 Keratinocyte growth factor-2
LAP Latency associated peptide
LCS Limb compartment syndrome
LDL Low density lipoprotein
LDS Loeys-Dietz syndrome
LLC Large latent complex
LEC Lymphatic endothelial cells

Abbreviation List xxix

LFA-1 Lymphocyte function-associated antigen-1
LO Lipoxygenase
LOX Lysyl oxidase
LOPS Loss of protective sensation
LPA Lysophosphatidic acid
LPS Lipopolysaccharide
LTA Lipoteichoic acid
LTGFBP Latent TGF binding protein
MAC-1 Macrophage-1 antigen
MAPK Mitogen activated protein kinase
MCP-1 Monocyte chemoattractant protein-1
M-CSF Macrophage-colony stimulating factor
MFS Marfan syndrome
MHC Major histocompatibility
MI Myocardial infarction
MIP-1 Macrophage inflammatory protein-1
MLC20 Myosin light chain20
MLCK Myosin light chain kinase
MLCP Myosin light chain phosphatase
MMP Matrix metalloproteinase
MODS Multiple organ dysfunction syndrome
MRA Magnetic resonance angiography
MRI Magnetic resonance imaging
mRNA Messenger RNA
MRSA Methicillin resistant Staphylococcus aureus
MRSE Methicillin resistant Staphylococcus epidermidis
MRTA Magnetic resonance tomographic angiography
MTHFR Methylenetetrahydrofolate reductase
MT-MMP Membrane-type MMP
MVPS Mitral valve prolapse syndrome
NADPH Nicotinamide adenine dinucleotide phosphate
NGF Nerve growth factor

xxx Mechanisms of Vascular Disease

NFκB Nuclear factor kappa B
NiTi Nitinol
NJP Non-junctional perforators
NMDA N-methyl-D-aspartate
NNH Number needed to harm
NNT Number needed to treat
NO Nitric oxide
NOS Nitric oxide synthase enzyme
NSAID Non-steroidal anti-inflammatory drug
NV Neovascularisation
OCP Oestrogen/progesterone contraceptive pill
OPN Osteopontin
OPG Osteoprotegerin
OR Odds ratio
OxLDL Oxidised low density lipoprotein
PAD Peripheral arterial disease
PAF Platelet activating factor
PAI Plasminogen activator inhibitor
PAI-1 Plasminogen activator inhibitor-1
PAR Protease activated receptor
PAR-1 Protease activated receptor-1
PAR-4 Protease activated receptor-4
PAU Penetrating aortic ulcer
PC Protein C
PCA Poly (carbonate-urea) urethane
PCI Percutaneous coronary intervention (angioplasty)
PCWP Pulmonary capillary wedge pressure
PDGF Platelet-derived growth factor
PDGFb Platelet-derived growth factor-b
PDS Polydioxanone
PECAM-1 Platelet-endothelial cell adhesion molecule-1
PEDF Pigment epithelium-derived factor
PES Paclitaxel-eluting stent

Abbreviation List xxxi

PET Positron emission tomography
PF4 Platelet factor 4
PGI2 Prostacyclin
PGG2 Prostaglandin G2
PGH2 Prostaglandin H2
PGEI2/PGI2 Prostaglandin I2
PGN Peptidoglycan
PHN Postherpetic neuropathy
PHZ Para-anastomotic hyper-compliant zone
PI3K Phosphatidylinositol 3-kinase
PIP2 Phosphatidylinositol 4,5-bisphosphate
PLC Phospholipase C
PLOD Procollagen lysyl hydroxylase
PMCA Plasma membrane Ca2+ APTases
PMN Polymorphonuclear leukocyte
POSS Polyhedral oligomeric silsesquioxanes
PPAR Peroxisomal proliferation activating receptor
PPI Proton pump inhibitor
PRV Polycythaemia rubra vera
PS Protein S
PSGL-1 P-selectin glycoprotein ligand-1
PT Prothombin time
PTCA Percutaneous coronary angioplasty
PTFE Polytetrafluoroethylene
PTS Post-thrombotic syndrome
PUFA Polyunsaturated fatty acid
PVI Primary valvular incompetence
rAAA Ruptured AAA
Rac Ras activated cell adhesion molecule
RANTES Regulated upon activation, normal T cell expressed and secreted
RAS Renin angiotensin system
RCT Randomised controlled trial

xxxii Mechanisms of Vascular Disease

RF Rheumatoid factor
RFA Radiofrequency ablation
rhAPC Recombinant human activated protein C
RNA Ribonucleic acid
ROS Reactive oxygen species
RR Relative risk
RSD Reflex sympathetic dystrophy
S1P Sphingosine-1-phosphate
SAPK Stress-activated protein kinase
SCF Stem cell factor
SCS Spinal cord stimulation
ScvO2 Superior vena cava venous oxygen saturation
SDF-1 Stromal-cell-derived factor-1
SERCA Sarco/endoplasmic reticulum CaATPases
SEP Serum elastin peptides
SES Sirolimus-eluting stent
SEPS Subfascial endoscopic perforator surgery
SFA Superficial femoral artery
SFJ Sapheno-femoral junction
SIRS Systemic inflammatory response syndrome
SKCa Small conductance calcium-activated potassium channels
SLE Systemic lupus erythematosus
SMA Smooth muscle alpha actin
SMC Smooth muscle cell
SMP Sympathetically maintained pain
SNARE Soluble N-ethylmaleimide-sensitive factor activating protein receptors
SNP Single nucleotide polymorphisms
SNRI Serotonin/Noradrenaline reuptake inhibitors
SPJ Sapheno-popliteal junction
SPP Skin perfusion pressure
SR Sarcoplasmic reticulum
SSRIs Selective serotonin re-uptake inhibitors
SSV Small saphenous vein

Abbreviation List xxxiii

SVT Superficial thrombophlebitis
STIM1 Stromal interacting molecule 1
TaCE TNFa converting enzyme
TAAD Thoracic aortic aneurysm disease
TAD Thoracic aortic dissection
TAFI Thrombin-activatable fibrinolysis inhibitor
Tc-99 MDP Technetium-99 methylene diphosphonate
TCA Tricyclic antidepressant
TCC Total contact cast
TCR T-cell receptor
TENS Transcutaneous electrical nerve stimulation
TF Tissue factor
TFPI Tissue factor pathway inhibitor
TGF Transforming growth factor
TGF-α Transforming growth factor-alpha
TGF-β Transforming growth factor-beta
TGL Triglycerides
Th T helper
TIA Transient ischemic attack
TIMP Tissue inhibitors of metalloproteinase
TLR Toll-like receptors
TNF Tumour necrosis factor
TNF-α Tumour necrosis factor-alpha
tPA Tissue-type plasminogen activator
TRP Transient receptor potential
TRPC Transmembrane receptor potential canonical
TRPV1 Transmembrane receptor potential Vanilloid-type
TXA2 Thromboxane A2
uPA Urokinase
UT University of Texas
VCAM Vascular cell adhesion molecule
VCAM-1 Vascular cell adhesion molecule-1
VEGF Vascular endothelial growth factor

xxxiv Mechanisms of Vascular Disease

VEGF-R Vascular endothelial growth factor receptor
VIP Vasoactive intestinal peptide
VLA-1 Very late activating antigen-1
VOCC Voltage operated calcium channels
VPT Vibratory perception threshold
VSMC Vascular smooth muscle cells
VTE Venous thromboembolism
VV Varicose veins
vWF von Willebrand factor
XO Xanthine oxidase

2  • Vascular Smooth Muscle Structure and
Function

David P Wilson

Molecular Physiology of Vascular Function Research Group,
Discipline of Physiology, University of Adelaide, South Australia

INTRODUCTION SMOOTH MUSCLE (VASCULAR)
STRUCTURE
Smooth muscle has an important role in
regulating the function of a variety of hollow Vascular smooth muscle cells have classically
organ systems including the: vasculature, been envisaged as fusiform cells, on average
airways, gastrointestinal tract, uterus and 200 microns long × 5 microns in diameter,
reproductive tract, bladder and urethra and with a large central nucleus surrounded by
several other systems. Smooth muscle has an abundant array of endoplasmic reticulum
two fundamental roles: 1) to alter the shape and golgi apparatus, with the cytosol and
of an organ and 2) to withstand the force of plasma membrane tapering toward the poles.
an internal load presented to that organ. In Although the dimensions of the vascular
order to achieve these fundamental objectives smooth muscle cell narrow toward their ends
smooth muscles have developed mechanisms there is clear evidence that the end-to-end
of mechanical coupling, which enable the junctions coupling smooth muscle cells are
development of powerful and coordinated complex and contain a significant number
contractions at a relatively low energy cost. For of membrane invaginations to provide
example,smooth muscleinthegastrointestinal increased surface area for both mechanical
tract must undergo intermittent but coordin­ tight junctions and electrical coupling via
ated phasic contractions to propel the bolus gap junctions (Figure 2.1). Vascular smooth
of food through the alimentary canal. muscle cells do not contain the complex
Whereas in the airways and vasculature the t-tubule/sarcoplasmic reticulum system
smooth muscle is more often in various states common to striated muscles, but rather they
of tonic contraction, but can be dynamically contain a significant number of invaginations
regulated to relax or contract in response to along the plasma membrane called caveolae,
specific neuro-hormonal and haemodynamic which serve a similar, albeit less developed role
signals. In keeping with the aims of this to increase the cellular surface: volume ratio.
text, this chapter will focus on the principle These specialized caveolae further provide
mechanisms through which vascular smooth a unique plasma membrane environment,
muscle functions. which enables clustering of specific groups

13

14 Mechanisms of Vascular Disease

Figure 2.1: Highlights the fusiform shape of typical smooth muscle cells and the patterned array of actin
myosin myofilaments across the cell. Smooth muscle cells have invaginations along their length to provide
increased surface area for mechanical coupling via tight junctions and electrical coupling through Gap
junctions. Dense bodies are thought to be similar to Z-disks found in striated muscle.

of ion channels and receptors important in that function to provide static support
cellular signal transduction. to the cell and to enable motor protein
mediated transport of cytosolic cargo and
In contractile vascular smooth muscle the for chromosomal segregation during mitosis.
endoplasmic reticulum has been modified The actin cytoskeleton and elements of
to enable Ca2+ release and reuptake and has the actin contractile myofilament are also
therefore been termed sarcoplasmic reticulum. generated from the polymerization of
In smooth muscle cells the sarcoplasmic globular monomeric actin to form polymeric
reticulum/endoplasmic reticulum (SR/ER) actin filaments. This process is dynamically
complex comprises about 5% of the total regulated even within the time scale of
cell volume, with a considerable amount contractile processes, i.e., as the smooth
of rough endoplasmic reticulum and golgi muscle slowly shortens it can actually
apparatus adjacent to the nucleus, which synthesise and extend the length of the actin
reflects the significant capacity that smooth filaments.
muscle has for protein synthesis and secretion.
The fact that vascular smooth muscle has a CONTRACTILE MYOFILAMENT
fundamental role in mediating pressure and
flow in the vasculature is reflected in the The structure of the smooth muscle acto­
abundance of cytoskeletal and contractile myosin array is similar to striated muscle
proteins expressed. with several important differences:

CYTOSKELETON 1. there is no troponin complex in smooth
muscle
As with all eukaryotic cells the cytoskeleton is
comprised of a network of many and various 2. contraction is regulated by Ca2+
filamentous proteins, often formed by the calmodulin-dependent myosin light
polymerization of monomeric subunits. chain kinase (MLCK) mediated
For example, monomers of alpha and beta phosphorylation of the regulatory light
tubulin self assemble into microtubules chains of myosin, which enables actin

Vascular Smooth Muscle Structure and Function 15

myosin interaction and cross bridge responsible for the Ca2+ calmodulin mediated
cycling phosphorylation of LC20 is actin associated
3. in the absence of Ca2+ and calmodulin while MLCP which removes the phosphoryl
(CaM), caldesmon interacts with groups from LC20 is associated with myosin.
actomyosin inhibiting the activity of (Figure 2.3)
myosin ATPase
4. the activity of myosin light chain FUNCTIONAL REGULATION OF
phosphatase (MLCP) directly causes VASCULAR SMOOTH MUSCLE:
the dephosphorylation of myosin LC20 NEURONAL, HORMONAL,
leading to relaxation RECEPTOR MEDIATED
5. the actin: myosin ratio is higher in
smooth muscle averaging 15:1 in Smooth muscle from all hollow organs
vascular smooth muscle in comparison including blood vessels have been somewhat
to 6:1 in skeletal or cardiac muscle. artificially categorized into either single
There are no intercalated disks or unit smooth muscle or multiunit smooth
z-disks, however, dense bodies in smooth muscle, when in reality they should likely be
muscle are thought to be analogous to considered as a combination of both types.
z-disks (Figure 2.2). Nevertheless, historically, multiunit smooth
muscle has been considered to be regulated
There are a variety of intermediate filament primarily through autonomic sympathetic
proteins but desmin and vimentin are innervations, which release neurotransmitters
particularly abundant in smooth muscle. In from varicosities along the axon, rather than
fact, desmin has been shown to be upregulated specifically coupling to individual cells.
in several myopathies and during smooth Consequently, neurotransmitters are required
muscle hypertrophy. As indicated once to diffuse anywhere from 5-100 nm to the
globular actin polymerizes into filaments adjacent smooth muscle membrane in order
they coil to form mature filamentous actin to activate their receptors. The activation
that then combines with tropomyosin to of sympathetic nerves therefore causes
form a large actin-tropomyosin filament membrane depolarization and activation of
which together is arranged in side polar voltage dependent ion channels, the most
arrays with myosin II filaments (Figure 2.1). prominent of which are the clinically relevant
The myosin II thick filaments are composed voltage operated Ca2+ channels (VOCC) of
of two 200kDa heavy chains, two 17kDa the Cav1.2 family, also known as the long
light chains and two phosphorylatable acting L-type Ca2+ channels. Due to the
regulatory myosin light chains (LC20). The mechanism of membrane depolarization, this
two heavy chains coil together forming a form of cellular activation has been termed
155nm rod, while the globular head contains electromechanical coupling. In contrast,
the motor domain consisting of light chains single unit smooth muscles have very little
and Mg2+ ATPase activity and the actin innervation and are primarily activated
binding domain. The myosin is arranged in by autocrine and paracrine hormones,
an anti parallel array that enables the myosin including noradrenalin, adrenalin, and
motors, on the heads of myosin molecules, angiotensin II, all of which function through
to draw actin polymers along its length and G-protein coupled membrane receptors.
effect shortening of the cell, so-called cross Receptor acti­vation either triggers sarcoplasmic
bridge cycling (Figure 2.2). MLCK, which is reticulum-mediated Ca2+ release or membrane

16 Mechanisms of Vascular Disease

Figure 2.2: Illustrates the patterned array of actin and myosin in smooth muscle in both cross section
and the longitudinal axis. Following phosphorylation of the light chains of myosin, actin and myosin interact
followed by the synchronous sliding of actin across the myosin. The movement of actin filaments toward the
center of the cell is driven by the Mg2+ ATPase activity in the myosin heads and results in cell shortening or
development of tension.

Figure 2.3: Illustrates the major pathways by which Ca2+ enters the cytosol, areas highlighted in blue
indicate mechanisms by which Ca2+ exits that cell. Ca2+ entry activates Ca2+ CaM-dependent myosin light
chain kinase leading to phosphorylation of myosin, leading to actin myosin interaction and contraction.
Myosin phosphatase dephosphorylates myosin uncoupling actin-myosin favouring vasorelaxation. Various
G-protein coupled receptors are capable of activating PKC/CPI-17 or RhoA/Rho kinases pathways which are
capable of inhibiting myosin phosphatase further favouring vasoconstriction.

Vascular Smooth Muscle Structure and Function 17

depolarization through the activation of relationship is considerably more variable
ion channels which may include VOCC. than that for skeletal or cardiac muscle, but
Consequently this form of activation has appears to be directly related to the degree
been termed pharmacomechanical coupling. of phosphorylation of the regulatory light
Experimental evidence also exists to suggest chains of myosin. The broader range of
that like striated muscle, extracellular Ca2+ optimal resting length amongst smooth
entry in smooth muscle can also activate SR muscle may reflect the dynamic changes in
Ca2+ release into the cytosol, so called Ca2+ load that exist within the vasculature and of
induced Ca2+ release, although this appears the high actin:myosin ratio in smooth muscle
to be a less common mechanism of Ca2+ relative to striated muscle. Interestingly, at
entry. Once activated, single unit smooth the onset of stretch or pressurization smooth
muscle cells tends to contract in synchrony muscle responds via activation of stretch
with neighbouring smooth cells, which are receptors (TREK and TRAK) that induce
coupled through gap junctions. Gap junctions Ca2+ entry and consequent smooth muscle
are composed of 6 connexin proteins, which shortening, which directly offsets increased
are transmembrane spanning proteins which vascular wall stress. This is the important
assemble to form a barrel-shaped connexon mechanism governing the phenomenon of
or hemichannel in the plasma membrane. autoregulation. It is important to note that
When two hemichannels from adjacent although gastrointestinal smooth muscle
cells assemble they form a functional gap appears relatively unaffected by significant
junction that enables the movement of ions stretch, more that 25% stretch often destroys
(electrical coupling) and small molecules the contractile properties of vascular smooth
between adjacent cells (Figure 2.1). Evidence muscle.
indicates that at least some of the vascular
smooth muscle cells in most vascular beds MYOFILAMENT BASIS OF
are electrically coupled via gap junctions and SMOOTH MUSCLE
may even be coupled to the endothelium in CONTRACTION AND
a similar manner. RELAXATION

SMOOTH MUSCLE FUNCTION Motility studies using isolated actin and
myosin proteins have identified that the duty
As with other muscle types smooth muscle cycle of the myosin head power stroke is
functions best when at its optimal resting 7-11 nm. Perhaps more important than the
length L0, which provides the ideal balance stroke length of the myosin is the activity of
of actin-myosin interaction and muscle the myosin ATPase, which along with Ca2+/
shortening. Vascular smooth muscle cells CaM and the activation state of myosin
that are stretched beyond L0 have less than light chain kinase and myosin light chain
optimal overlap of actomyosin crossbridges phosphatase, determines the extent and the
and thus are unable to maintain or generate rate of contraction of the vascular smooth
maximum force. In contrast, smooth muscle (Figure 2.3). Smooth muscle myosin
muscle that is over shortened experiences ATPase hydrolyses ATP at a rate of ~0.16
increased internal resistance due to internal moles ATP/mol myosin/second, which is
friction generated from having too many several orders of magnitude slower than
slowly cycling cross bridges. However, in the skeletal muscle myosin ATPase which
smooth muscle the optimal length tension hydrolyses ~10-20 moles ATP/mol myosin/

18 Mechanisms of Vascular Disease

second. In part the slower ATPase rate of vasodilatation. However, myosin associated,
the myosin head accounts for the vastly myosin light chain phosphatase (MLCP),
slower contraction rates of vascular smooth is responsible for the dephosphorylation
muscle compared with striated muscles. of myosin LC20 and the consequent loss
In addition, there are a variety of different of smooth muscle acto-myosin interaction
isoforms of smooth muscle myosin II which and the attenuation of cross bridge cycling
when differentially expressed will increase (Figure 2.3). It is important to recognize that,
or decrease the maximum rate of smooth simple removal of extracellular Ca2+ only
muscle contraction. For example, so called stops the phosphorylation of LC20 and does
foetal isoforms of smooth muscle myosin II not provide an explanation for subsequent
have a slower rate of contraction. In addition, smooth muscle relaxation since the LC20
these “foetal” isoforms have been shown to be remains phosphorylated. This also partially
upregulated during extended hypoxia, and explains why Ca2+ channel blockers are less
during phenotypic remodelling of smooth effective in attenuating pre-existing vascular
muscle from a contractile to synthetic or spasm as opposed to preventing spasm.
proliferative phenotype.

Smooth muscle contraction and ION CHANNELS IMPORTANT IN
relaxation THE REGULATION OF SMOOTH
MUSCLE FUNCTION
As mentioned, unlike cardiac and skeletal
muscle, smooth muscle does not contain Regulation of cellular Ca2+
troponin and therefore is not subject to
troponin mediated regulation of contraction. There are vast arrays of ion channels,
Smooth muscle contraction makes use pumps, transporters and exchangers that are
of another Ca2+ binding protein called important in regulating ionic balance and
calmodulin (CaM), which when bound smooth muscle membrane potential. Perhaps
with Ca2+ mediates the activation of the the best know are the electrogenic 3Na+/2K+
actin bound myofilament enzyme, myosin ATPase and the voltage gated L-type Ca2+
light chain kinase (MLCK), which in turn channels but includes: Na+/Ca2+ exchangers,
phosphorylates the regulatory light chains plasma membrane Ca2+ ATPases (PMCA),
of myosin (LC20). Phosphorylation of the which provide routes to extrude Ca2+ from
myosin LC20 is a critical step in smooth muscle the cytosol into the extracellular space,
contraction which causes a conformational whereas the sarcoplasmic reticulum Ca2+
change in the myosin head enabling the ATPases (SERCA) are important in removing
interaction of myosin with actin, cross bridge Ca2+ from the cytosol back into the SR. In
cycling, and contraction. Removal of cytosolic contrast, when the SR becomes depleted of
Ca2+ occurs through the activation of energy Ca2+, Ca2+ sensor proteins in the SR termed
dependent plasma membrane Ca2+ ATPases stromal interacting molecule 1 (STIM1)
(PMCA), Na+/Ca2+ exchangers and sarco/ translocate to the plasma membrane and
endoplasmic reticulum CaATPases (SERCA) activate an ion channel called Orai1 which
(Figure 2.3). However, since MLCK- enables refilling of SR Ca2+ stores. In addition,
mediated phosphorylation of the serine 19 a great deal of recent research has focused
of myosin LC20 generates a covalent bond, on the non-selective cation channels of the
simply removing Ca2+ does not directly cause transmembrane receptor potential canonical
(TRPC) family that are thought be involved

Vascular Smooth Muscle Structure and Function 19

in regulating Na+ and Ca2+ entry. Finally a variety of non-selective cation channels have
series of potassium channels are involved in the capacity to conduct a variety of ions
either re or hyperpolarisation of the plasma including Ca2+ and Na+ into the smooth
membrane and thereby have therapeutic muscle cell but due to their low conductance
potential in limiting extracellular Ca2+ entry are currently thought to be more important
through voltage operated Ca2+ channels and in regulating membrane potential and
thereby limiting vasoconstriction. subsequent activation of plasma membrane
VDCC (Figure 2.3).
Sources of cytosolic Ca2+ entry
Potassium channels
Within the smooth muscle cell, Ca2+ enters
the cytosol from the extracellular space The insulin-dependent electrogenic 3Na+/
or from the intracellular endoplasmic 2K+ ATPase is important in establishing
reticulum, which in muscle cells is termed the resting membrane potential (EM) of the
the sarcoplasmic reticulum (SR). Within vascular smooth muscle cell. However,
muscle the sarcoplasmic reticulum has the activation states of several types of K+
become variously modified to affect Ca2+ channels in smooth muscle are also important
release into the cytoplasm. Typically agents in effecting membrane depolarization and
that activate the ryanodyne receptor such as hyperpolarisation and consequent smooth
caffeine or phospholipase C (PLC) derived musclecontractionandrelaxation,respectively.
inositol 1, 4, 5 tris phosphate (IP3) which The inward rectifier KIR channels become
activates the IP3 receptors (which are ion activated when the membrane becomes
channels) in the SR cause Ca2+ to be released hyper­polarized and beyond the equilibrium
into the cytosol. Ca2+ entering the smooth potential for potassium (EK) they transport
muscle cell from the extracellular space does more K+ ions from the extracellular space into
so through non-selective cation channels or the cell thereby offsetting or rectifying the
selective Ca2+ channels, which may or may hyperpolarizing stimulus. However, there are
not be gated by voltage. To date the most few if any physiological conditions in which
important source of extracellular Ca2+ entry EM is more negative than EK, consequently,
in vascular smooth muscle is mediated by the even the KIR channels conduct a small outward
voltage dependent Ca2+ channels (VDCC). hyperpolarizing K+ current, and therefore
The primary VDCC are the long lasting Ca2+ along with the 3Na+/2K+ ATPase may be
channel, so called L-type or Cav1.2 channels, important in mediating smooth muscle tone.
which are the clinical targets of the L-type
channel blockers the dihydropryidines, The KV family of potassium channels as the
phenylalkamines, benzothiazapenes. More name suggests are activated by depolarization
recent evidence indicates that a second class and thus are thought to be an important
of VDCC, the transient or T-type Ca2+ control mechanism to hyperpolarize the
channels also known as the Cav3.X family smooth muscle cell following neural or
may be important in mediating Ca2+ entry in hormonal-mediated depolarization. Agonists
the microvasculature. As the name suggests including histamine acting through the
VDCC are activated by a depolarization H1 receptor have been shown to block the
of the plasma membrane, which increases 4-aminopyridine sensitive KV channels in
the open probability and overall Ca2+ coronary arteries.
conductance into the cell. In addition, a
Physiologically KATP channels are activated
by agents including, adenosine, calcitonin gene

20 Mechanisms of Vascular Disease

regulated peptide (CGRP) and vasoactive endothelin-1, serotonin and thromboxane A2.
intestinal peptide (VIP). The activation of Many GPCRs exhibit divergent subcellular
KATP channels and hyperpolarization medi­ signalling mechanisms and there is increasing
ated vasodilatation is thought to be due in evidence for diversity of subcellular signalling
part to activation of adenylyl cyclase and amongst vascular beds (Figure 2.3). For
subsequent cAMP dependent activation of example, angiotensin II can be generated
protein kinase A. More recent evidence has both locally within smooth muscle cells and
also indicated that KATP channels become systemically through the renin angiotensin
activated in a protein kinase C-dependent system (RAS). In smooth muscle the
manner. However, perhaps more important is type I AngII receptors are prototypical
the fact that cytosolic ATP and ADP function G-protein coupled receptors which couple
to close and open KATP channels, respectively. through Gq11. Similarly endothelin-1 can
This explains part of the mechanism be generated locally via endothelial cells,
underlying the finding that vasculature in inflammatory cells or renal sources. Like
ischemic tissue, containing high ADP: ATP Ang II, endothelin-1 makes use of Gq11 in
levels extrude K+ in an effort to hyperpolarize smooth muscle to activate PLC, releasing
the membrane and effect vasodilatation. diacylglycerol (DAG) activating non selective
Both experimentally and clinically the cation channels which facilitates membrane
so-called vasodilatory K+ channel openers depolarization and subsequent extracellular
including pinacidil, cromakalim, diazoxide, Ca2+ entry through VGCC. In addition,
and minoxidil activate KATP channels. the activation of PLC generates IP3 causing
Interestingly the antidiabetic sulfonylurea SR-mediated Ca2+ release. DAG can also
drugs, including glibenclamide actually activate PKC leading to the phosphorylation
inhibit KATP channels, enabling membrane of CPI-17 which specifically inhibits myosin
depolarization and activation of VOCC in phosphatase, favouring phosphorylation of
pancreatic beta cells enabling insulin release. the LC20 of myosin and vasoconstriction
Consequently overuse of sulfonourea drugs (Figure 2.3). However, in contrast to AngII,
may therefore interfere with the efficacy endothelin-1 also activates G13 coupled
of vascular K+ channel openers or directly receptors activating the RhoA/ Rho associated
contribute to vasoconstriction. kinase which leads to a direct inhibitory
phosphorylation of myosin phosphatase,
The large conductance Ca2+ activated again favouring contraction (Figure 2.3).
potassium channels (BKCa) channels are also
voltage sensitive but the smaller conductance ENDOTHELIAL REGULATION
smKCa channels are less sensitive to voltage. OF SMOOTH MUSCLE
This family of K+ channels are activated by VASODILATATION
increases in cytosolic Ca2+ which occurs after
agoniststimulation,membranedepolarization Nitric oxide is a potent vasodilator generated
or stretch/pressure-dependent activation of in the endothelium which has many and
Ca2+ entry and therefore is involved in that varied effects in the vasculature including
arm of the myogenic mechanism involved in attenuating: platelet adhesion and aggre­
hyperpolarization. gation,  cellular proliferation, and vaso­
constriction. A common theme underlying
G protein coupled receptors (GPCRs) the influence of nitric oxide is activation
transd­ uce signals from the autonomic nervous of guanylyl cyclase, formation of cGMP,
system and hormonal stimuli including brady­
kinin,noradrenalin,adrenaline, angiotensin II,