Development and characterization of tissue-engineered aortic valves

Tissue-engineered aortic valves, known as recellularized heart valves, were developed by seeding human neonatal fibroblasts onto decellularized, porci ne aortic valves. Recellularized heart valves were cultured up to 8 weeks i n a novel bioreactor that imposed dynamic pulsatile fluid flow to expose th e dermal fibroblasts to mechanical forces. Our data showed that, under stat ic or dynamic flow conditions, dermal fibroblasts attached to and migrated into the decellularized, porcine valve scaffolding. The human cells remaine d viable as indicated by MTT viability staining. Gradual colonization of th e decellularized porcine scaffolding by the human dermal fibroblasts was sh own histologically by hematoxylin & eosin staining, immunocytochemically us ing a monoclonal antibody directed against prolyl-4-hydroxylase (an intrace llular enzyme expressed by human fibroblasts synthesizing collagen), and qu antitative digital image analyses. Thymidine and proline radiolabeled analo g studies at 1, 2 and 4 weeks of individual leaflets cultured statically de monstrated that the human fibroblasts were mitotic and synthesized human ex tracellular matrix proteins, thereby supplementing the existing porcine mat rix. The overall approach results in a heart valve populated with viable hu man cells. In the development of valves that perform in a similar manner as natural biological structures, this approach may present some unique benef its over current medical therapies.