Tissue-Engineered Grafts Matured in the Right Ventricular Outflow Tract.

Autologous smooth muscle cell (SMC)-seeded biodegradable scaffolds could be a suitable material to repair some pediatric right ventricular outflow tract (RVOT) cardiac anomalies. Adult syngenic Lewis rat SMCs (2 × 106) were seeded onto a new biodegradable copolymer sponge made of ∊-caprolactone-co-L-lactide reinforced with poly-L-lactide fabric (PCLA). Two weeks after seeding, the patch was used to repair a surgically created RVOT defect in an adult rat. At 8 weeks after implantation the spongy copolymer component was biodegraded, and SM tissue and extracellular matrices containing elastin fibers were present in the scaffolds. By 22 weeks more fibroblasts and collagen were present (p < 0.05). The number of capillaries in the grafts also increased (p < 0.001) between 8 and 22 weeks. The fibrous poly-L-lactide component of the PCLA scaffold remained. The 22-week grafts maintained their thickness and surface area in the RVOT. The SMCs prior to implantation were in a synthetic phenotype and developed in vivo into a more contractile phenotype. By 8 weeks the patches were endothelialized on their endocardial surfaces. Future work to increase the SM tissue and elastin content in the patch will be necessary before implantation into a pediatric large-animal model is tested.