Tissue-engineered heart valve leaflets: An animal study

Background: Tissue-engineered heart valve leaflets are a promising way to o vercome the inherent limitations of current prosthetic valves. The aim of t his study was to compare the biological responses of an autologous cell see ded scaffold and an acellular scaffold implanted in the pulmonary valve lea flet in the same animal. Methods: Myofibroblasts and endothelial cells were isolated and cultured fr om an ovine artery. A synthetic biodegradable scaffold consisting of polygl ycolic acid and polylactic acid was initially seeded with the myofibroblast s, then coated with endothelial cells. Cells were seeded using a medium con taining collagen and cultured. A tissue-engineered construct and a plain sc affold were implanted as double pulmonary valve leaflet replacement in the same animal in an ovine model (n=3). Additionally, the tissue-engineered co nstruct (n=2) and the plain scaffold (n=2) were implanted as single valve l eaflet replacements for long-term analysis. After sacrifice, the implanted valve leaflet tissues were retrieved, analyzed visually and using light mic roscopy. Results: Three animals that underwent replacement of two valve leaflets wit h a tissue-engineered construct and a plain scaffold, survived only a short -time (12, 24, 36 hours). The death was attributed to heart failure caused by severe pulmonary insufficiency. Animals that underwent single valve leaf let replacement survived longer and were electively sacrificed at 6 and 9 w eeks after operation. The analysis of the leaflets from the short-term surv ivors showed that the tissue-engineered constructs contained less fibrins a nd protein exudates than the plain scaffold. In contrast, leaflets obtained from animals surviving 6 and 9 weeks showed similar well organized granula tion tissues in the tissue-engineered constructs and the plain scaffolds. Conclusion: This animal experiment demonstrates that in the early phase of implantation, the tissue-engineered construct shows a better biological res ponse in terms of antithrombogenicity than the plain scaffold, although bot h of them have similar results in the later reparative phase.