GAGs were demonstrated to be preserved using NEN fixation, but the effects of their preservation were not investigated. Analysis of valve biomechanics with and without selective GAG removal could help reveal this. Any effects cause by longer storage periods should also be studied as valves may be stored clinically for up to three years. EDC and NHS utilize the carboxyl groups on GAGs to form the crosslinks that aid in preservation. However, these same groups are necessary to retain the hydrophilic properties of GAGs. Effects on tissue hydration should be studied along with any associated changes this my cause to tissue biomechanics.
Since formaldehyde is suspected in the calcification experienced by the NEN group, storage in an alternative reagent should be investigated. However, if formalin storage is still determined to be favored, the use of anti-calcification treatments could also be studied. Specific attention could also be paid to the areas in which calcification occur. As GAGs have been associated with possible prevention of calcification, specific tissue layers may be more resistant to calcification than others. Other segments of BHV tissue, such as the aortic wall, should also be tested for calcification potential.
Further exploration into the mechanisms for the reduced stiffness and increased extensibility is needed. Tissue dimensions should be measured before and after fixation to determine the legitimacy of the tissue shrinkage hypothesis. Further research into the effects of NEN fixation should also be performed including flexural testing, biaxial tensile testing, and cyclic mechanical fatigue testing. Changes to valve biomechanics that may occur during storage or fatigue should also be assessed. Lastly, these enhanced biomechanical studies should also include studies into the effects of GAG preservation.
8. REFERENCES
1. Guyton AC, Hall JE. Textbook of Medical Physiology 11th Ed. Philidelphia, PA:
Elsevier Saunders, 2006.
2. Shier D, Butler J, Lewis R. Hole’s Human Anatomy & Physiology 11th Ed. New
York, NY: McGraw Hill, 2007.
3. Cabin HS. The heart and how it works. The Heart and Circulation: Chapter 1, 3-9.
4. Sacks MS, Yoganathan AP. Heart valve function: a biomechanical perspective.
Phil. Trans. R. Soc. B 2007 362, 1369-1391.
5. Schoen FJ, Levy RJ. Tissue heart valves: Current challenges and future research
perspectives. J Biomed Mater Res, 47, 439-465, 1999.
6. Simionescu DT. Artificial heart valves. Wiley Encyclopedia of Biomedical
Engineering. John Wiley & Sons, Inc., 1-10, 2006.
7. Martini FH, Ober WC, Garrison CW, Welch K, Hutchings RT. Fundamentals of
Anatomy & Physiology 5th Ed. Upper Saddle River, NJ: Prentice Hall, 2001.
8. Cotran RS, Kumar V, Collins T. Robbins Pathologic Basis of Disease 6th Ed.
Philidelphia, PA: W.B. Saunders, 1999.
9. Eriksen HA, Satta J, Risteli J, Veijola M, Vare P, Soini Y. Type I and type III
collagen synthesis and composition in the valve matrix in aortic valve stenosis. Atherosclerosis 189: 91-98, 2006.
10. Scott M, Vesely I. Aortic valve cusp microstructure: the role of elastin. Ann Thorac Surg 60: S391-S394, 1995.
11. Schoen FJ. Cardiac valves and valvular pathology: update on function, disease,
repair, and replacement. Cardiovascular Pathology 14: 189-194, 2005.
12. Vyavahare N, Ogle M, Schoen FJ, Levy RJ. Elastin calcification and its
prevention with aluminum chloride pretreatment. American Journal of Patholgy 155, 3: 973-982, 1999.
13. Balguid A, Rubbens MP, Mol A, et al. The role of collagen cross-links in
biomechanical behavior of human aortic heart valve leaflets – relevance for tissue engineering. Tissue Engineering 13,7: 1501-1511, 2007.
14. Vesely I. The role of elastin in aortic valve mechanics. Journal of Biomechanics
15. Vyavahare N, Ogle M, Schoen FJ, Zand R, Gloeckner DC, Sacks M, Levy RJ. Mechanisms of bioprosthetic heart valve failure: fatigue causes collagen denaturation and glycosaminoglycan loss. J Biomed Mat Res 46: 44-50, 1999.
16. Ellis R, Green E, Winlove PC. Structural analysis of glycosaminoglycans and
proteoglycans by means of raman microspectrometry. Connective Tissue Research 50: 29-36, 2009.
17. Dudhia J. Aggrecan, aging and assembly in articular cartilage. Cell and Molecular
Life Sciences 62: 2241-2256, 2005.
18. Lovekamp J, Simionescu DT, Mercuri JJ, Zubiate B, Sacks MS, Vyavahare NR.
Stability and function of glycosaminoglycans in porcine bioprosthetic heart valves. Biomaterials 27: 1507-1518, 2006.
19. Grande-Alen KJ, Mako JW, Calabro A, Shi Yaling, Ratliff NB, Vesely I. Loss of
chondroitin 6-sulfate and hyaluronan from failed porcine bioprosthetic valves. Journal of Biomedical Material Research 65A: 251-259, 2003.
20. Rodriguez E, Roughley P. Link Protein can retard the degradation of hyaluronan
in proteoglycan aggregates. Osteoarthritis and cartilage 14: 823-829, 2006.
21. Heinegard D. Proteoglycans and more – from molecules to biology. Int. J. Exp.
Path. 90: 575-586, 2009.
22. Ng L, Grodzinksy AJ, Patwari P, Sandy J, Plaas A, Ortiz C. Individual cartilage
aggrecan macromolecules and their constituent glycosaminoglycans visualized via atomic force microscopy. Journal of Structural Biology 143: 242-257, 2003.
23. Meechai N, Jamieson AM, Blackwell J, Carrino DA. Nonlinear viscoelasticity of
concentrated solutions of aggrecan aggreagate. Biomacromolecules 2: 780-787, 2001.
24. Lehman S, Walther T, Kempfert J, Rastan A, Garbade J, Dhein S, Mohr FW.
Mechanical strain and the aortic valve: influence on fibroblasts, extracellular matrix, and potential stenosis. Ann Thorac Surg 88, 1476-1483, 2009.
25. Simionescu DT, Lovekamp JJ, Vyavahare NR. Glycosaminoglycan-degrading
enzymes in porcine aortic heart valves: implications for bioprosthetic heart valve degeneration. Journal of Heart Valve Disease 12, 2:217-225, 2003.
26. Flanagan TC, Pandit A. Living artificial heart valve alternatives: a review. European Cells and Materials 6: 28-45, 2003.
27. Sacks MS, Smith DB, Hiester ED. The aortic valve microstructure: effects of
28. Sacks MS, Stella JA. On the biaxial mechanicl properties of the layers of the aortic valve leaflet. Journal of Biomechanical Engineering 129: 757-766, 2007.
29. Sacks MS, Merryman DW, Schmidt DE. On the biomechanics of heart valve
function. Journal of Biomechanics 42: 1804-1824, 2009.
30. Raghavan D, Starcher BC, Vyavahare NR. Neomycin binding preserves
extracellular matrix in bioprosthetic heart valves during in vitro cyclic fatigue and storage. Acta Biomateriala 5:983-992, 2009.
31. Shah SR, Vyavahare NR. The effect of glycosaminoglycan stabilization on tissue
buckling in bioprosthetic heart valves. Biomaterials 29:1645-1653, 2008.
32. Cotran RS, Robbins SL, Collins T, Kumar V. Robbins Pathologic Basis of
Disease 6th Ed. Philadelphia, PA: W.B. Saunders Co., 1998.
33. Siu SC, Silversides CK. Bicuspid aortic valve disease. Journal of American
College of Cardiology 55(25): 2789-2800, 2010.
34. Olivier C. Rheumatic fever – is it still a problem? Journal of Antimicrobial
Chemotherapy 45:13-21, 2000.
35. Guilherme L, Ramasawmy R, Kalil J. Rheumatic fever and rheumatic heart
disease: genetics and pathogenesis. Scandinaian Journal of Immunology 66:199-207, 2007.
36. Moreillon P, Que Y. Infective endocarditis. The Lancet 363:139-149, 2004.
37. Becker AE. Acquired heart valve pathology: an update for the millennium. Herz
23:415-419, 1998.
38. Freeman RV, Otto CM. Spectrum of calcific aortic valve disease: pathogenesis,
disease progression, and treatment strategies. Circulation 111:3316-3326, 2005.
39. O’Brien KD. Pathogenesis of calcific aortic valve disease: a disease process
comes of age (and a good deal more). Arterioscler Thromb Vasc Biol 26:1721-1728, 2006.
40. Maganti K, Rigolin VH, Sarano ME, Bonow RO. Vascular heart disease:
diagnosis and management. Mayo Clin Proc 85(5):483-500, 2010.
41. Lloyd-Jones D et al. Heart disease and stroke statistics 2010 update: a report from
42. Liu AC, Joag VR, Gotlieb AI. The emerging role of valve interstitial cell phenotypes in regulating heart valve pathobiology. American Journal of Pathobiology 171:1407-1418, 2007.
43. Dasi LP, Simon HA, Sucosky P, Yoganathan AP. Fluid mechanics of artificial
heart valves. Clinical and Experimental Pharmacology and Physiology 36:225-237, 2009.
44. Harken DF, Taylor WJ, LeFemine AA, Lefemine AA, Lunzer S, Low HB, Cohen
ML, Jacobey JA. Aortic valve replacement with a caged ball valve. Am J Cardiol 9: 292– 299, 1962.
45. Ghanbari H, Viatge H, Kidane AG, Burriesci G, Tavakoli M, Seifalian AM.
Polymeric heart valves: new materials, emerging hopes. Trends in Biotechnology 27(6):359-367, 2009.
46. Kidane AG, Burriesci G, Cornejo P, Dooley A, Sarkar S, Bonhoeffer P,
Edirisinghe M, Seifalian AM. Current developments and future prospects for heart valve replacement therapy. Journal of Biomedical Material Research Part B: Applied Biomaterials 88B:290-303, 2009.
47. Venkatraman S, Boey F, Lao LL. Implanted cardiovascular polymers: natural,
synthetic and bio-inspired. Progress in Polymer Science 33:853-874, 2008.
48. Gott VL, Alejo DE, Cameron DE. Mechanical heart valves: 50 years of evolution.
Ann Thorac Surg 76:S2230-S2239, 2003.
49. Pibarot P, Dumesnil JG. Prosthetic heart valves: selection of the optimal
prosthesis and long-term management. Circulation 119:1034-1048, 2009.
50. Nair K, Muraleedharan CV, Bhuvaneshwar GS. Developments in mechanical
heart valve prosthesis. Sadhana 28(3-4):575-587, 2003.
51. DeWall RA, Qasim N, Carr L. Evolution of mechanical heart valves. Ann Thorac
Surg. 69:1612-1621, 2000.
52. Voet D, Voet JG, Pratt CW. Fundamentals of Biochemistry Upgrade Ed.
Hoboken, NJ: John Wiley & Sons, Inc., 2002.
53. Akhtar RP, Abid AR, Zafar H, Khan JS. Anticoagulation in patients following
prosthetic heart valve replacement. Ann Thorac Cardiovasc Surg 15:10-17, 2009.
54. Zilla P, Brink J, Human P, Bezuidenhout D. Prosthetic heart valves: catering for
the few. Biomaterials 29:385-406, 2008.
55. Dee KC, Puleo DA, Bizios R. An Introduction to Tissue-Biomaterial Interactions.
56. Jegatheeswaran A, Butany J. Pathology of infectious and inflammatory diseases in prosthetic heart valves. Cardiovascular Pathology 15:252-255, 2006.
57. Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient
mismatch in the aortic valve position and its prevention. Journal of the American College of Cardiology 36(4):1131-1141, 2000.
58. Van Nooten GJ, Belleghem YV, Caes F, Francois K, Van Overbeke H, Bove T,
Taeymans Y. Lower-intensity anticoagulation for mechanical heart valves: a new concept with the ATS bileaflet aortic valve. The Journal of Heart Valve Disease 12:495-502, 2003.
59. Lu P, Liu J, Huang R, Lo C, Lai H, Hwang N. The closing behavior of
mechanical aortic heart valve prosthesis. ASAIO Journal 50:294-300, 2004.
60. Gregoric I et al. Preclinical assessment of a trileaflet mechanical valve in the mitral position in a calf model. Ann Thorac Surg 77:196-202, 2004.
61. Johansen P. Mechanical heart valve cavitation. Expert Rev. Medical Devices
1(1):95-104, 2004.
62. Siddiqui RF, Abraham JR, Butany J. Bioprosthetic heart valves: modes of failure.
Histopathology 55:135-144, 2009.
63. Schenke-Layland K et al. Impact of cryopreservation on extracellular matrix
structures of heart valve leaflets. Ann Thorac Surg 82:918-927, 2006.
64. Gunatillake PA, Adhikari R. Biodegradable synthetic polymers for tissue
engineering. European Cells and Materials 5:1-16, 2003.
65. Simon P, Kasimir MT, Seebacher G, Weigel G, Ullrich R, Salzer-Muhar U,
Rieder E, Wolner E. Early failure of the tissue engineered porcine heart valve
SYNERGRAFTTM in pediatric patients. European Journal of Cardio-thoracic Surgery
23:1002-1006, 2003.
66. Elkins RC, Dawson PE, Goldstein S, Walsh SP, Black KS. Decellularized human
valve allografts. Ann Thorac Surg 71:S428-S432, 2001.
67. de Mel A, Jell G, Stevens MM, Seifalian AM. Biofunctionalization of
biomaterials for accelerated in situ endothelialization: a review. Biomacromolecules 9(11):2969-2979, 2008.
68. Hoerstrup SP, Sodian R, Daebritz S, Wang J, Bacha EA, Martin DP, Moran AM,
Guleserian KJ, Sperling JS, Kaushal S, Vacanti JP, Schoen FJ, Mayer JE Jr. Function trileaflet heart valves grown in vitro. Circulation 102;Suppl III:III-44-III-49, 2000.
69. Nagele H, Doring V, Rodiger W, Kalmar P. Aortenklappenersatz mit homografts. Herz 25:651-658, 2000.
70. Crick SJ, Sheppard MN, Ho SY, Gebstein L, Anderson RH. Anatomy of the pig
heart: comparisons with normal human cardiac structure. Journal of Anatomy 193:105- 119, 1998.
71. Vesely I, The evolution of bioprosthetic heart valve design and its impact on durability. Cardiovascular Pathology 12:277-286, 2003.
72. Butany J et al. Biological replacement heart valves identification and evaluation.
Cardiovascular Pathology 12:119-139, 2003.
73. Hoffmann G, Lutter G, Cremer J. Durability of bioprosthetic cardiac valves.
Dtsch Arztebl Int 105(8):143-148, 2008.
74. Vrandecic M et al. Retrospective clinical analysis of stented vs. stentless porcine
aortic bioprostheses. European Journal of Cardio-thoracic Surgery 18:46-53, 2000.
75. Simionescu DT, Lovekamp JJ, Vyavahare NR. Degeneration of bioprosthetic
heart valve cusp and wall tissues is initiated during tissue preparation: an ultrastructural study. The Journal of Heart Valve Disease 12:226-234, 2003.
76. Wells SM, Sellaro T, Sacks MS. Cyclic loading response of bioprosthetic heart
valves: effects of fixation stress state on the collagen fiber architecture. Biomaterials 26:2611-2619, 2005.
77. Mirnajafi A, Zubiate B, Sacks MS. Effects of cyclic flexural fatigue on porcine
bioprosthetic heart valve heterograft biomaterials. J Biomed Mater Res 94A:205-213, 2010.
78. Schoen FJ, Levy RJ. Calcification of tissue heart valve substitutes: progress
towards understanding and prevention. Ann Thorac Surg 79:1072-1080, 2005.
79. Weska RF et al. Natural and prosthetic heart valve calcification: morphology and
chemical composition characterization. Artificial Organs 34(4):311-318, 2010.
80. Clark JN, Ogle MF, Ashworth P, Bianco RW, Levy RJ. Prevention of
calcification of bioprosthetic heart valve cusp and aortic wall with ethanol and aluminum chloride. Ann Thorac Surg 79:897-904,2005.
81. Schoen FJ. Pathology of bioprostheses and other tissue heart valve replacements.
In: Silver MD, editor. Cardiovascular pathology, 2nd ed. New York: Churchill Livingstone;P 1547–1605, 1991.
82. Purinya B, Kasyanov V, Volkolakov J, Latisis R, Tetere G. Biomechanical and structural properties of the explanted bioprosthetic valve leaflets. J Biomech 27:1–11, 1994.
83. Simionescu DT, Lovekamp JJ, Vyavahare NR. Extracellular matrix degrading
enzymes are active in porcine stentless aortic bioprosthetic heart valves. J Biomed Mater Res 66A:775-763, 2003.
84. Schoen FJ. Aortic valve structure-function correlations: role of elastic fibers no longer a stretch of the imagination. J Heart Valve Dis 6:1–6, 1997.
85. Broom N, Christie GW. The structure/function relationship of fresh and
glutaraldehyde-fixed aortic valve leaflets. In: Cohn LH, Gallucci V, editors. Cardiac bioprostheses: proceedings of the Second International Symposium. New York: Yorke Medical Books; p 476–491, 1982.
86. Jorge-Herrero E, Fernandez P, Gutierrez M, Castillo-Olivares JL. Study of the calcification of bovine pericardium: Analysis of the implication of lipids and proteoglycans. Biomaterials 12:683 -689, 1991.
87. Strates B, Lian JB, Nimni ME. Calcification in cardiovascular tissues and
bioprostheses. In: Nimni ME (ed). Collagen 1989; Volume III, Biotechnology. CRC Press, Boca Rotan, FL:274-292, 1989.
88. Lovekamp J, Vyavahare N. Periodate-mediated glycosaminoglycan stabilization
in bioprosthetic heart valves. J Biomed Mater Res 56:478-486, 2001.
88. Lovekamp J, Vyavahare NR. Periodate-mediated glycosaminoglycan stabilization
in bioprosthetic heart valves. J Biomed Mater Res 56:478-486, 2001.
89. Zilla P, Human P, Bezuidenhout D. Bioprosthetic heart valves: the need for a quantum leap. Biotechnol Appl Biochem 40:57-66, 2004.
90. Human P, Zilla P. Characterization of the immune response to valve
bioprostheses and its role in primary tissue failure. Ann Thorac Surg 71: S385-S388, 2001.
91. Nimni M, Cheung D, Strates B, et al. Chemically modified collagen: a natural
biomaterial for tissue replacement. J Biomed Mater Res 21:741-771, 1987.
92. Ferrans V, Spray L, Billingham M, Roberts W. Structural changes in
glutaraldehyde treated porcine heterografts used as substitute cardiac valves – transmission and scanning electron microscopic observations in 12 patients. American Journal of Cardiology 41:1149-1184, 1978.
93. Nistal F, Garcia-Satue E, Artinana E, Duran C, Gallo I. Comparative study of primary tissue valve failure between ionescu-shirley pericardial and hancock porcine valves in the aortic position. American Journal of Cardiology 57:161-164, 1986.
94. Valente M, Bortolotti U, Thiene G. Ultrastructural substrates of dystrophic
calcification in porcine bioprosthetic valve failure. American Journal of Pathology 119,12-21, 1985.
95. Dahm M, Husmann M, Eckhard M, et al. Relevance of immunologic reactions for
tissue failure of bioprosthetic heart valves. Ann Thorac Surg 60:S348-S352, 1995.
96. Stein P, Wang C, Riddle J, Magilligan DJ. Leukocytes, platelets, and surface
microstructure of spontaneous degenerated porcine bioprosthetic valves. Journal of Cardiac Surgery 3:243-261, 1988.
97. Everts V, van DZE, Creemers L, Beertsen W. Phagocytosis and intracellular
digestion of collagen, its role in turnover and remodeling. The Histochemical Journal 28:229-245, 1996.
98. Human P, Zilla P. The possible role of immune response in bioprosthetic heart valve failure. Journal of Heart Valve Disease 10:460-466, 2001.
99. Vincentelli A, Latremouille C, Zegdi R, et al. Does glutaraldehyde induce
calcification of bioprosthetic tissues? Ann Thorac Surg 66:S255-S258, 1998.
100. Lila N et al. Gal knockout pig pericardium: new source of material for heart valve bioprosthesis. The Journal of Heart and Lung Transplantation 29:538-543, 2010.
101. Chiam PTL, Ruiz CE. Percutaneous transcatheter aortic valve implantation: evolution of the technology. Am Heart J 157:229-242, 2009.
102. Fann JI et al. Evolving strategies for the treatment of valvular heart disease: preclinical and clinical pathways for percutaneous aortic valve replacment. Catheterization and Cardiovascular Interventions 71:434-440, 2008.
103. Khor E. Methods for the treatment of collagenous tissues for bioprostheses. Biomaterials 18:95-105, 1997.
104. Zilla P, Weissenstein C, Human P, Dower T, von Oppell UO. High glutaraldehyde concentrations mitigate bioprosthetic root calcification in the sheep model. Ann Thorac Surg 70:2091-2095, 2000.
105. Connolly JM et al. Triglycidylamine crosslinking of porcine aortic valve cusps or bovine pericardium results in improved biocompatibility, biomechanics, and calcification resistance. American Journal of Pathology 166(1), 2005.
106. Pereira CA, Lee JM, Haberer S. Effect of alternative crosslinking methods on the strain rate viscoelastic properties of bovine pericardial bioprosthetic material. J Biomed Mater Res 1990;24:345– 61.
107. Sung H, Chen C, Liang H, Hong M. A natural compound (reuterin) produced by Lactobacillus reuteri for biological-tissue fixation. Biomaterials 2003; 24 (8):1335–47. 108. Sung H, Chang Y, Chiu C, Chen C, Liang H. Mechanical properties of a porcine aortic valve fixed with a naturally occurring crosslinking agent. Biomaterials 1999;20(19):1759–72.
109. Meuris B, Phillips R, Moore MA, Flameng W. Porcine stentless bioprosthesis: prevention of aortic wall calcification by dye-mediated photo-oxidation. Artificial Organs 27(6):537-543, 2003.
110. Moore MA, Phillips RE, McIlroy BK, Walley VM, Hendry PJ. Evaluation of porcine valves prepared by dye-mediated photooxidation. Ann Thorac Surg 66:S245- S248, 1998.
111. Moore MA, Adams AK. Calcification resistance, biostability, and low immunogenic potential of porcine heart valves modified by dye-mediated photooxidation. J Biomed Mater Res 56:24-30, 2001.
112. Kozma EM, Wisowski G, Poltorak AJ, Olczyk P, Olczyk K, Nawrat Z. The influence of physical and chemical agents on photooxidiation of porcine pericardial collagen. Bio-Medical Materials and Engineering 15:137-144, 2005.
113. Schoen FJ. Pathologic findings in explanted clinical bioprosthetic valves fabricated from photooxidized bovine pericardium. Journal of Heart Valve Disease 7(2): 174-179, 1998.
114. Everaerts F, Torrianni M, Hendriks M, Feijen J. Biomechanical properties of carbodiimide crosslinked collagen: influence of the formation of ester crosslinks. J Biomed Mater Res 85A:547-555, 2008.
115. Lee JM, Edwards HHL, Pereira CA, Samii SI. Crosslinking of tissue-derived biomaterials in 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). Journal of Materials Science 7:531-541, 1996.
116. Everaerts F, Gillissen M, Torrianni M, Zilla P, Human P, Hendriks M, Feijen J. Reduction of calcification of carbodiimide-processed heart valve tissue by prior blocking of amine groups with monoaldehydes. The Journal of Heart Valve Disease 15:269-277, 2006.
117. Girardot JMD, Girardot MN. Amide cross-linking: an alternative to glutaraldehyde fixation. The Journal of Heart Valve Disease 5:518-525, 1996.
118. Zilla P, Bezuidenhout D, Torrianni M, Hendriks M, Human P. Diamine-extended glutaraldehyde- and carbodiimide crosslinks act synergistically in mitigating bioprosthetic aortic wall calcification. The Journal of Heart Valve Disease 14(4):538- 545, 2005.
119. Everaerts F, Torrianni M, van Luyn M, van Wachem P, Feijen J, Hendriks M. Reduced calcification of bioprosthesis, cross-linked via an improved carbodiimide based method. Biomaterials 25:5523-5530, 2004.
120. Englert C, Blunk T, Muller R, von Glasser SS, Baumer J, Fierlbeck J, Heid IM, Nerlich M, Hammer J. Bonding of articular cartilage using a combination of biochemical degradation and surface crosslinking. Arthritis Research and Therapy 9(3):R47, 2007. 121. Herrick WC, Kingsbury HB, Lou DY. A study of the normal range of strain, strain rate, and stiffness of tendon. Journal of Biomaterial Research 12(6): 877-894, 1978. 122. Schoen FJ. Evolving concepts of cardiac valve dynamics: the continuum of development, functional structure, pathobiology, and tissue engineering. Circulation 118:1864-1880, 2008.
123. Wells SM, Sellaro T, Sacks MS. Cyclic loading response of bioprosthetic heart valves: effects of fixation stress state on the collagen fiber architecture. Biomaterials 26:2611-2619, 2005.
124. Sacks MS, Schoen FJ. Collagen fiber disruption occurs independent of calcification in clinically explanted bioprosthetic heart valves. J Biomed Mater Res 62:359-371, 2002.
125. Talman EA, Boughner DR. Internal shear properties of fresh porcine aortic valve cusps: Implications for normal valve function. The Journal of Heart Valve Disease 5: 152-159, 1996.
126. Vesely I, Boughner D, Song T. Tissue buckling as a mechanism of bioprosthetic heart valve failure. Ann Thorac Surg 46:302-308, 1988.
127. Broom N. An “in vitro” study of mechanical fatigue in glutaraldehyde-treated porcine aortic valve tissue. Biomaterials 1:3-8, 1980.
128. Mirnajafi A, Raymer JM, McClure LR, Sacks MS. The flexural rigidity of the aortic valve leaflet in the commissural region. Journal of Biomechanics 39:2966-2973, 2006.
129. Stella JA, Liao J, Sacks MS. Time-dependent biaxial mechanical behavior of the aortic heart valve leaflet. Journal of Biomechanics 40:3169-3177, 2007.
130. Nishimura M et al. Role of chondroitin sulfate-hyaluronan interactions in the viscoelastic properties of extracellular matrices and fluids. Biochimica et Biophysica Acta 1380:1-9, 1998.
131. Stephens EH, Chu CK, Grande-Allen JK. Valve proteoglycan content and glycosaminoglycan fine structure are unique to microstructure, mechanical load and age: relevance to an age-specific tissue-engineered heart valve. Acta Biomateriala 4:1148- 1160, 2008.
132. Mercuri JJ, Lovekamp JJ, Simionescu DT, Vyavahare NR. Glycosaminoglycan- targeted fixation for improved bioprosthetic heart valve stabilization. Biomaterials 28: 496-503, 2007.
133. Raghavan D, Simionescu DT, Vyavahare NR. Neomycin prevents enzyme- mediated glycosaminoglycan degradation in bioprosthetic heart valves. Biomaterials 28: 2861-2868, 2007.
134. Farndale RW, Buttle DJ, Barrett AJ. Improved quantitation and discrimination of sulphated glycosaminoglycans by use of dimethylmethylene blue. Biochim Biophys Acta 883:173-177, 1986.
135. Loke WK, Khor E. Validation of the shrinkage temperature of animal tissue for bioprosthetic heart valve application by differential scanning calorimetry. Biomaterials 16: 251-258, 1995.
136. Perumal S, Antipova O, Orgel JP. Collagen fibril architecture, domain organization, and triple-helical conformation govern its proteolysis. Proc Natl Acad Sci USA 105:2824-2829, 2008.
137. Golomb G, Schoen FJ, Smith MS, Linden J, Dixon M, Levy RJ. The role of glutaraldehyde-induced crosslinks in calcification of bovine pericardium used in cardiac valve bioprostheses. Am J Pathol 127:122–30, 1987.
138. Grabenwoger M, Sider J, Fitzal F, et al. Impact of glutaraldehyde on calcification of pericardial bioprosthetic heart valve material. Ann Thorac Surg 62:772–7, 1996. 139. Walley VM, Keon WJ. Patterns of failure in Ionescu– Shiley bovine pericardial bioprosthetic valves. J Thorac Cardiovasc Surg 93(6): 925–33, 1987.
140. Wight TN, Heinegard DK, Hascall VC. Proteoglycans. Structure and Function. In: Hay ED, editor. Cell biology of extracellular matrix. New York: Plenum Press; p 45– 78, 1991.
141. Reinboth B et al. Molecular interactions of biglycan and decorin with elastic fiber components: biglycan forms a ternary complex with tropoelastin and microfibril-