The Study of Cardiovascular Tissue Processing in the United Kingdom Name Jill Hughes Year 2008
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Title The Study of Cardiovascular Tissue Processing in the United Kingdom Name Jill Hughes Year 2008 This is a digitised version of a dissertation submitted to the University of Bedfordshire. It is available to view only. This item is subject to copyright. The Study of Cardiovascular Tissue Processing in the United Kingdom Jill Hughes MSc by Research University of Bedfordshire 2008 THE STUDY OF CARDIOVASCULAR TISSUE PROCESSING IN THE UNITED KINGDOM by Jill Hughes A THESIS SUBMITTED FOR THE DEGREE OF MASTER BY RESEARCH OF THE UNIVERSITY OF BEDFORDSHIRE LIRANS Institute of Research in the Applied Natural Sciences University of Bedfordshire 250 Butterfield Great Marlings Luton, LU2 8DL UK June 2008 CONTENTS ABSTRACT I CONTENTS II - VI LIST OF TABLES VII LIST OF FIGURES VIII - IX LIST OF APPENDICES X REFERENCES 161 - 191 PRESENTATIONS AND PUBLICATIONS 192 THE STUDY OF CARDIOVASCULAR TISSUE PROCESSING IN THE UNITED KINGDOM JILL HUGHES ABSTRACT The study of United Kingdom cardiovascular tissue banking practice has required research into areas of cardiovascular tissue banking that have previously not been clarified, explored in detail or reported. The pressures which have been the driving forces for change in tissue banking in recent years have been identified and the National shortage of cardiovascular tissue donors in relation to the increasing surgical demand has been quantified for the first time in the UK. An examination of the evolution of cardiovascular tissue banking enabled subsequent identification of the inconsistencies reported and the importance of recording small differences in processing details. A detailed overview of current UK cardiovascular tissue processing methodology was collated which, for the first time, established the differences in current practice. The study subsequently identified tissue bankers concerns. The study has identified areas where there may be a need for control, standardisation and improvement of methodology and has highlighted areas where it seems to be agreed that there is need for optimisation of processing technique. The study has also uncovered areas where there is a lack of understanding amongst tissue bankers regarding cryopreservation principles such as freezing and chilling injury and also confirmed the need for more careful control and measurement of techniques used such as cooling and warming rates which may or may not affect the quality of the tissue processed. The study confirmed that processing techniques were generally empirically based but despite this, the processed tissue seems to be effective. Further work has been suggested which includes recommendations for methods which could be used to monitoring tissue quality and subsequently for harmonisation of tissue banking procedures. I ACKNOWLEDGEMENTS I gratefully acknowledge the staff of the Oxford Heart Valve Bank for their support and patience. I appreciate them help and co-operation I have received from the BATB Cardiovascular Special Interest group members who participated in this study and the surgeons, in particular Donald Ross and Magdi Yacoub, and London tissue banker Robert Parker, who helped to establish the missing background information required which helped to clarify the inconsistencies in the published articles. The author would like to thank the Oxford University Nuffield Department of Clinical Laboratory Sciences for their help with the use of some of the experimental equipment used. The author would like to help Prof. Tiantian Zhang, Prof. David Rawson, Prof. Barry Fuller, Prof. Brian Grout, Mr Ravi Pillai for their help in this study and preparation of this submitted thesis. I would finally like to thank my family for their kindness and encouragement. CONTENTS CHAPTER 1.0 : INTRODUCTION 1 1.0. INTRODUCTION 1 1.1. PRINCIPLES OF CRYOBIOLOGY 1 1.2. CHILLING INJURY 2 1.2.1. ‘Direct Chilling Injury’ or ‘Cold Shock’ 3 1.2.2. ‘Indirect Chilling injury’ 4 1.3. FREEZING INJURY 5 1.3.1. Extracellular freezing injury 6 1.3.2. Intracellular freezing injury 7 1.4. THAWING INJURY 8 1.5. CRYOPROTECTANTS 9 1.6. APPROACHES USED IN CRYOPRESERVATION 11 1.6.1. Controlled Slow Cooling 11 1.6.2. Vitrification 12 1.7. CRYOPRESERVATION OF TISSUES 15 1.7.1. Introduction 15 1.7.2. Difficulties with tissue cryopreservation 15 1.7.3. Optimisation of tissue cryopreservation variables 16 1.7.4. Successfully Cryopreserved Human Tissues 18 1.7.5. General Cryopreservation methodology 18 1.7.6. New developments in tissue cryopreservation 19 1.8 PERSONAL HISTORY & EXPERIENCE 20 II CHAPTER 2:0 AIMS OF THE STUDY 23 2.1 MATERIALS AND METHODS 24 2.1.1 Establish National Status & Issues concerning UK Cardiovascular tissue banks 24 2.1.2 To investigate the introduction & application of cardiovascular tissue for transplantation & the evolution of processing methodology and emergence of tissue banks 24 2.1.3 To establish current UK cardiovascular tissue processing practice 25 2.1.4 To identify current concerns in UK Cardiovascular Tissue Banking 27 CHAPTER 3:0 RESULTS 29 3.1 Current Status of Cardiovascular Tissue Cryopreservation 29 3.1.1 UK & European Legislatory Requirements 29 3.1.2 National Shortage of Organs & Tissue 31 3.1.3 National Shortage of Cardiovascular Tissue 32 3.1.4 Delay in release of donor tissue for transplantation 38 3.1.5 National Tissue Banking Association 38 3.1.6 European Cardiovascular Tissue Working Groups 39 3.1.7 Requirement for Quality Assurance & Validation of special processes 39 3.1.8 Tissue Bank staff Professional Registration & Career Framework 40 3.2 Developments in Cardiovascular Tissue Processing 42 3.2.1 Introduction 42 3.2.2 Terminology 43 3.2.3 Historical Background 43 3.2.4 Advantages of using cardiovascular valve tissue 45 3.2.5 Disadvantages of Homografts 46 3.2.6 Evolution of homograft disinfection methodology 47 3.2.7 Evolution of preservation methodology 48 3.2.8 Introduction of ‘viable’ cryopreservation 51 III 3.3 UK Cardiovascular Tissue Banking Review – General Features` 54 3.3.1 Organisation of Tissue Banks 54 3.3.2 The role of UK Cardiovascular Tissue Banks 56 3.3.3 Inspection and Licensing Status of UK tissue banks 59 3.4 Tissue Processing Practice 62 3.4.1 Consent & Donor Selection 62 3.4.2 Procured donor tissue types 63 3.4.3 Time limits for Procurement 64 3.4.4 Donor Age limits 66 3.4.5 Procurement technique & infection risk 68 3.4.6 Procurement facility & conditions 69 3.4.7 Procurement and processing equipment 71 3.4.8 Packaging & Transport of procured tissue 71 3.4.9 Tissue bank facility air quality 72 3.4.10 Dissection, Quality Assessment, sizing and grading 73 3.4.11 Tissue Disinfection 74 3.4.12 Microbiology in-process testing of tissue segments 78 3.4.13 Donor Serology testing 81 3.4.14 Paediatric Donor serology testing 82 3.4.15 Additional serology testing 83 3.4.16 Other supplementary tests 83 3.4.17 Testing of thawed tissue samples 84 3.4.18 Interpretation of tissue sample results & rejection criteria 84 3.4.19 Summary of Similarities & Differences in UK Cardiovascular tissue banks 87 3.5 Review of UK Cardiovascular tissue banking – Cryopreservation issues 89 3.5.1 Cryoprotection time limits 90 3.5.2 Rinsing tissue prior to cryoprotection 90 3.5.3 Cryoprotection media 92 3.5.4 Cryoprotectant addition 92 3.5.5 Cryoprotectant total volume 93 3.5.6 Tissue packaging prior to cryopreservation 94 3.5.7 Cryopreservation equipment & dummy sachets 96 3.5.8 Cryopreservation programs 99 3.5.9 Preferred type of long term storage 103 3.5.10 Storage Maximum time limit 105 3.5.11 Packaging for distribution 108 3.5.12 Re-warming & Removal of Cryoprotectant 109 IV 3.5.13 Tissue Storage at the Surgical centre 113 3.5.14 Return of tissue to the tissue bank 115 3.5.15 Recall of tissue 117 3.5.16 Summary of similarities and differences in cryopreservation in UK banks 119 3.6 Review of UK Cardiovascular Tissue Banking – Quality Assessment Protocols 120 3.6.1 Types and ‘values’ of published quality assessment methods 120 3.6.2 Quality Assessment principles currently imposed in UK banks 122 3.6.3 Quality Assessment methods used routinely in Cardiovascular tissue banks 122 3.6.4 Histopathological examination of tissue samples 124 3.6.5 Mechanical activity testing 124 3.6.6 Tissue culture methods of quality assessment 125 3.6.7 Complete in vitro function studies 125 3.6.8 Study of explanted cardiovascular tissue 126 3.7 Review of UK Cardiovascular Tissue Banking – Validation protocols 128 3.7.1 Overview of UK Cardiovascular tissue banks’ Validation Protocols 128 3.7.2 Validation reports recently compiled in UK tissue banks 128 3.7.3 Validation of long term clinical performance of the tissue 130 3.8 UK Review of Cardiovascular Tissue Banks – Identification of issues of concern 132 3.8.1 Overview of issues of concern amongst UK tissue bankers 132 3.8.2 Examples of issues which currently concern UK Tissue bankers 132 3.8.3 Summary of issues that currently concern UK Cardiovascular tissue bankers 134 CHAPTER 4:0 DISCUSSION 135 4.1 Comparison of early processing techniques 135 4.2 The perceived need to maintain ‘viability’ 139 4.3 Early acute homograft ‘failure’ 141 4.4 Viability assessment assays 142 v CHAPTER 5:0 CONCLUSIONS 144 5.1 Overview 144 5.2 Summary 153 5.3 Future work 157 5.4 Reflective notes 160 VI LIST OF TABLES Table 1 Comparison of UK tissue banking processing time limits for procurement, dissection and fluids used for transport and rinsing 65 Table 2 Disinfection cocktail used 76 Table 3 Microbiology testing in UK Cardiovascular banks 79 Table 4 Cryoprotection, Packaging and cooling procedures 91 Table 5 Type and extent of low temperature storage method and packaging chosen by UK banks 107 Table 6 Recommended UK Cardiovascular bank procedures for rewarming and removal of cryoprotectant from cardiovascular tissue in operating theatre 110 Table 7 Storage and Return of Unused Tissue 114 VII LIST OF FIGURES Fig 1.