The independent role of cyclic flexure in the early in vitro development of an engineered heart valve tissue.

Tissue engineered heart valves (TEHV) are being investigated as an alternative to current non-viable prosthetic valves and valved conduits. Studies suggest that pulse duplicator bioreactors can stimulate TEHV development. In the current study, a model system was used to determine if cyclic flexure, a major mode of heart valve deformation, has independent effects on TEHV cell and extracellular matrix (ECM) development. Ovine vascular smooth muscle cells (SMC) were seeded for 30 h onto strips of non-woven 50:50 polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffold. After 4 days of incubation, SMC-seeded and unseeded scaffolds were either maintained under static conditions (static group), or subjected to unidirectional cyclic three-point flexure at a physiological frequency and amplitude in a bioreactor (flex group) for 3 weeks. After seeding or incubation, the effective stiffness (E) was measured, with SMC-seeded scaffolds further characterized by DNA, collagen, sulfated glycosaminoglycan (S-GAG), and elastin content, as well as by histology. The seeding period was over 90% efficient, with a significant accumulation of S-GAG, no significant change in E, and no collagen detected. Following 3 weeks of incubation, unseeded scaffolds exhibited no significant change in E in the flex or static groups. In contrast, E of SMC-seeded scaffolds increased 429% in the flex group (p<0.01) and 351% in the static group (p<0.01), with a trend of increased E, a 63% increase in collagen (p<0.05), increased vimentin expression, and a more homogenous transmural cell distribution in the flex versus static group. Moreover, a positive linear relationship (r2=0.996) was found between the mean E and mean collagen concentration. These results show that cyclic flexure can have independent effects on TEHV cell and ECM development, and may be useful in predicting the mechanical properties of TEHV constructed using novel scaffold materials.

[1]  Frederick J Schoen,et al.  Evolution of cell phenotype and extracellular matrix in tissue-engineered heart valves during in-vitro maturation and in-vivo remodeling. , 2002, The Journal of heart valve disease.

[2]  U A Stock,et al.  Tissue engineering of heart valves -- current aspects. , 2002, The Thoracic and cardiovascular surgeon.

[3]  W. Chan,et al.  Anticoagulation of pregnant women with mechanical heart valves: a systematic review of the literature. , 2000, Archives of internal medicine.

[4]  Dietmar W. Hutmacher,et al.  Scaffold design and fabrication technologies for engineering tissues — state of the art and future perspectives , 2001, Journal of biomaterials science. Polymer edition.

[5]  A. Grodzinsky,et al.  Fluorometric assay of DNA in cartilage explants using Hoechst 33258. , 1988, Analytical biochemistry.

[6]  M. Sacks,et al.  The biomechanical effects of fatigue on the porcine bioprosthetic heart valve. , 2001, Journal of long-term effects of medical implants.

[7]  D W Hutmacher,et al.  An introduction to biodegradable materials for tissue engineering applications. , 2001, Annals of the Academy of Medicine, Singapore.

[8]  J. Ralphs,et al.  Organisation of the chondrocyte cytoskeleton and its response to changing mechanical conditions in organ culture , 1999, Journal of anatomy.

[9]  Ralf Sodian,et al.  Living, autologous pulmonary artery conduits tissue engineered from human umbilical cord cells. , 2002, The Annals of thoracic surgery.

[10]  A. Ramamurthi,et al.  Towards tissue engineering of a composite aortic valve. , 2002, Biomedical sciences instrumentation.

[11]  Simon P. Hoerstrup,et al.  Cardiovascular tissue engineering: a new laminar flow chamber for in vitro improvement of mechanical tissue properties. , 2000 .

[12]  F J Schoen,et al.  Functional Living Trileaflet Heart Valves Grown In Vitro , 2000, Circulation.

[13]  C. McCulloch,et al.  Cadherins Mediate Intercellular Mechanical Signaling in Fibroblasts by Activation of Stretch-sensitive Calcium-permeable Channels* , 2001, The Journal of Biological Chemistry.

[14]  Michael S. Sacks,et al.  A novel bioreactor for the dynamic flexural stimulation of tissue engineered heart valve biomaterials. , 2003 .

[15]  B. Allen,et al.  Pericardial tissue valves and Gore-Tex conduits as an alternative for right ventricular outflow tract replacement in children. , 2002, The Annals of thoracic surgery.

[16]  Simon P. Hoerstrup,et al.  Tissue Engineering of Functional Trileaflet Heart Valves From Human Marrow Stromal Cells , 2002, Circulation.

[17]  J. Mayer.  Uses of homograft conduits for right ventricle to pulmonary artery connections in the neonatal period. , 1995, Seminars in thoracic and cardiovascular surgery.

[18]  K. McLeod,et al.  Integrin-Mediated Mechanotransduction in Vascular Smooth Muscle Cells: Frequency and Force Response Characteristics , 2001, Circulation research.

[19]  E. P. Moiseeva.  Adhesion receptors of vascular smooth muscle cells and their functions. , 2001, Cardiovascular research.

[20]  D. Mooney,et al.  Combining chondrocytes and smooth muscle cells to engineer hybrid soft tissue constructs. , 2000, Tissue engineering.

[21]  Stefan Fischer,et al.  Anticoagulant therapy in pregnant women with mechanical heart valves , 2003, Archives of Gynecology and Obstetrics.

[22]  F P T Baaijens,et al.  The relevance of large strains in functional tissue engineering of heart valves. , 2003, The Thoracic and cardiovascular surgeon.

[23]  Frederick J Schoen,et al.  Cardiovascular tissue engineering. , 2002, Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology.

[24]  David P. Martin,et al.  Quantitative evaluation of endothelial progenitors and cardiac valve endothelial cells: proliferation and differentiation on poly-glycolic acid/poly-4-hydroxybutyrate scaffold in response to vascular endothelial growth factor and transforming growth factor beta1. , 2003, Tissue engineering.

[25]  A Haverich,et al.  Tissue Engineering of Pulmonary Heart Valves on Allogenic Acellular Matrix Conduits: In Vivo Restoration of Valve Tissue , 2000, Circulation.

[26]  J E Mayer,et al.  New pulsatile bioreactor for in vitro formation of tissue engineered heart valves. , 2000, Tissue engineering.

[27]  R. Sodian,et al.  A New Approach to Completely Autologous Cardiovascular Tissue in Humans , 2002, ASAIO journal.

[28]  Ajit P. Yoganathan,et al.  Biosynthetic Activity in Heart Valve Leaflets in Response to In Vitro Flow Environments , 2001, Annals of Biomedical Engineering.

[29]  H. Schnittler,et al.  Correlation of endothelial vimentin content with hemodynamic parameters , 1998, Histochemistry and Cell Biology.

[30]  M. Sacks,et al.  Effects of mechanical fatigue on the bending properties of the porcine bioprosthetic heart valve. , 1999, ASAIO journal.

[31]  F J Schoen,et al.  Aortic valve structure-function correlations: role of elastic fibers no longer a stretch of the imagination. , 1997, The Journal of heart valve disease.

[32]  Payam Akhyari,et al.  Mechanical Stretch Regimen Enhances the Formation of Bioengineered Autologous Cardiac Muscle Grafts , 2002, Circulation.

[33]  E Wolner,et al.  Early failure of the tissue engineered porcine heart valve SYNERGRAFT in pediatric patients. , 2003, European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery.

[34]  D J Mooney,et al.  Smooth muscle cell adhesion to tissue engineering scaffolds. , 2000, Biomaterials.

[35]  David P. Martin,et al.  Advances in the Mechanisms of Cell Delivery to Cardiovascular Scaffolds: Comparison of Two Rotating Cell Culture Systems , 2001, ASAIO journal.

[36]  Gabriel Acevedo-Bolton,et al.  Intracardiac fluid forces are an essential epigenetic factor for embryonic cardiogenesis , 2003, Nature.

[37]  M. Sacks,et al.  Collagen fiber disruption occurs independent of calcification in clinically explanted bioprosthetic heart valves. , 2002, Journal of biomedical materials research.

[38]  D J Mooney,et al.  Optimizing seeding and culture methods to engineer smooth muscle tissue on biodegradable polymer matrices. , 1998, Biotechnology and bioengineering.

[39]  L A Taber,et al.  Biomechanics of cardiovascular development. , 2001, Annual review of biomedical engineering.

[40]  M. Thubrikar.  The Aortic Valve , 1990 .

[41]  David C. Lee,et al.  Form and function of developing heart valves: coordination by extracellular matrix and growth factor signaling , 2003, Journal of Molecular Medicine.

[42]  J. Mayer,et al.  Ethical and regulatory issues concerning engineered tissues for congenital heart repair. , 2003, Seminars in thoracic and cardiovascular surgery. Pediatric cardiac surgery annual.

[43]  David J. Mooney,et al.  Cyclic mechanical strain regulates the development of engineered smooth muscle tissue , 1999, Nature Biotechnology.

[44]  P. D. del Nido,et al.  Valved homograft conduit repair of the right heart in early infancy. , 1999, The Annals of thoracic surgery.

[45]  Michael S. Sacks,et al.  Dynamic In Vitro Quantification of Bioprosthetic Heart Valve Leaflet Motion Using Structured Light Projection , 2001, Annals of Biomedical Engineering.

[46]  D. Powell,et al.  Powell, D. W. et al. Myofibroblasts. I. Paracrine cells important in health and disease. Am. J. Physiol. 277, C1-C9 , 1999 .

[47]  D J Mooney,et al.  Scaffolds for engineering smooth muscle under cyclic mechanical strain conditions. , 2000, Journal of biomechanical engineering.

[48]  R Langer,et al.  Functional arteries grown in vitro. , 1999, Science.

[49]  Alexander Lembcke,et al.  Ross operation with a tissue-engineered heart valve. , 2002, The Annals of thoracic surgery.

[50]  Michael Sacks,et al.  Thoracic Surgery Directors Association Award. Bone marrow as a cell source for tissue engineering heart valves. , 2003, The Annals of thoracic surgery.

[51]  W. Chan,et al.  Anticoagulation of pregnant women with mechanical heart valves. , 2003, Archives of internal medicine.

[52]  Bart Meuris,et al.  Design of a new pulsatile bioreactor for tissue engineered aortic heart valve formation. , 2002, Artificial organs.

[53]  Joseph P Vacanti,et al.  Dynamic rotational seeding and cell culture system for vascular tube formation. , 2003, Tissue engineering.