Tissue engineered heart valves: autologous cell seeding on biodegradable polymer scaffold

We previously reported on the successful creation of tissue-engineered valve leaflets and the implantation of these autologous tissue leaflets in the pulmonary valve position. Mixed cell populations of endothelial cells and fibroblasts were isolated from explanted ovine arteries. Endothelial cells were selectively labeled with an acetylated low-density lipoprotein marker and separated from fibroblasts using a fluorescent activated cell sorter. A synthetic biodegradable scaffold consisting of polyglycolic acid fibers was seeded first with fibroblasts then subsequently coated with endothelial cells. Using these methods, autologous cell/polymer constructs were implanted in 6 animals. In 2 additional control animals, a leaflet of polymer was implanted without prior cell seeding. In each animal, using cardiopulmonary bypass, the right-posterior leaflet of the pulmonary valve was resected completely and replaced with an engineered valve leaflet with (n = 6) or without (n = 2) prior cultured cell seeding. After 6 h and 1, 6, 7, 9, and 11 weeks, the animals were sacrificed and the implanted valve leaflets were examined histologically, biochemically, and biomechanically. Animals receiving leaflets made from polymer without cell seeding were sacrificed and examined in a similar fashion after 8 weeks. In the control animals, the acellular polymer leaflets were degraded completely leaving no residual leaflet tissue at 8 weeks. The tissue-engineered valve leaflet persisted in each animal in the experimental group; 4-hydroxyproline analysis of the constructs showed a progressive increase in collagen content. Immunohistochemical staining demonstrated elastin fibers in the matrix and factor VIII on the surface of the leaflet. The cell labeling experiments demonstrated that the cells on the leaflets had persisted from the in vitro seeding of the leaflets. In the tissue-engineered heart valve leaflet, transplanted autologous cells generated proper matrix on the polymer scaffold in a physiologic environment at a period of 8 weeks after implantation.