Tissue Engineering of Pulmonary Heart Valves on Allogenic Acellular Matrix Conduits : In Vivo Restoration of Valve Tissue

Abstract

Background-Tissue engineering using in vitro-cultivated autologous vascular wall cells is a new approach to biological heart valve replacement. In the present study, we analyzed a new concept to process allogenic acellular matrix scaffolds of pulmonary heart valves after in vitro seeding with the use of autologous cells in a sheep model. Methods and Results-Allogenic heart valve conduits were acellularized by a 48-hour trypsin/EDTA incubation to extract endothelial cells and myofibroblasts. The acellularization procedure resulted in an almost complete removal of cells.After that procedure, a static reseeding of the upper surface of the valve was performed sequentially with autologous myofibroblasts for 6 days and endothelial cells for 2 days, resulting in a patchy cellular restitution on the valve surface.The in vivo function was tested in a sheep model of orthotopic pulmonary valve conduit transplantation. Three of 4 unseeded control valves and 5 of 6 tissue-engineered valves showed normal function up to 3 months. Unseeded allogenic acellular control valves showed partial degeneration (2 of 4 valves) and no interstitial valve tissue reconstitution. Tissue-engineered valves showed complete histological restitution of valve tissue and confluent endothelial surface coverage in all cases. Immunohistological analysis revealed cellular reconstitution of endothelial cells (von Willebrand factor), myofibroblasts (␣-actin), and matrix synthesis (procollagen I). There were histological signs of inflammatory reactions to subvalvar muscle leading to calcifications, but these were not found in valve and pulmonary artery tissue. Conclusions-The in vitro tissue-engineering approach using acellular matrix conduits leads to the in vivo reconstitution of viable heart valve tissue.

Immunoproteomic identification of bovine pericardium xenoantigens

“…It has become increasingly clear that the assumption that xenoantigens are likely to be cell-associated is not valid. Our findings further emphasize that treatment of unfixed xenogeneic tissues for tissue engineering applications must shift from a paradigm of "decellularization" to one of "antigen removal" [9][10][11][12][14][15][16][17][18][19][20][21][22][23][24][25][26]. Current or future antigen removal or antigen masking treatments will need to account for both cellular and extracellular matrix antigens.…”

“…Because tissues are unfixed in this application, it is necessary to remove graft antigenicity prior to implantation. Numerous physical and chemical treatments designed to decrease the immunogenicity of unfixed xenogeneic biomaterials have been investigated [9,11,12,[14][15][16][17][18][19][20][21][22][23][24][25][26]. These treatments have generally been characterized as tissue "decellularization", based on the assumption that antigens mediating an immune response to the graft would likely be cell-associated.…”

Avaliação do comportamento biológico de homoenxertos valvares pulmonares descelularizados: estudo experimental em ovinos

“…The extracellular matrix intact, not antigenic and without residual cytotoxicity is a prerequisite for biocompatibility and longevity of allografts [24].…”

Comparação entre o pericárdio bovino decelularizado e o pericárdio bovino convencional utilizado na confecção de biopróteses valvares cardíacas

“…Thus, several strategies have been evaluated with the objective of eliminating or minimizing tissue degeneration induced by these factors, in particular by using the decellularization technique. Detergents have been used, as described by COURTMANN et al [26] and DOHMEN et al [27]; enzymatic extraction by means of tripsin as described by STEINHOFF et al [28], the Synergraft technique presented by O'BRIEN et al [13]; and even cellular extraction utilized by GOISSIS et al [16,29] in the Institute of Chemistry of USP, São Carlos which was the method employed in this study.…”