Bioactive porcine matrices in heart valve tissue engineering

Background and aim of the study: Platelet gel (PG), a storage vehicle of growth factors, can be considered for the application of growth factors in combination with mesenchymal stem cells (MSCs) to accelerate tissue regeneration. Moreover, the addition of bioactive factors to porcine aortic valves could result in a more rapid repopulation. The study aim was to load acellular porcine aortic valve matrices with the PG-rich growth factors and to evaluate the effect on MSC repopulation. Methods: Ovine mesenchymal stem cells (oMSCs) were isolated from sheep bone marrow. Acellular porcine heart valve matrices (n = 3) were preloaded with heparin and incubated with the PG for 2 h. A quantitative sandwich enzyme immunoassay was used to examine the release of basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta) from the matrices. oMSC repopulation was stimulated by static and dynamic culture. Results: The immunoassays revealed that heparin-preloaded PG-incubated matrices showed a sustained release of 56.28 pg/ml bFGF and 30.66 ng/ml TGF-beta 1 after 24 h. Dynamic culture induced oMSC invasion in growth factor-loaded matrices. Cell density results showed that dynamic culture significantly enhanced the repopulation of growth factor-loaded matrices (75 +/- 21 cells/mm(2)) when compared to static culture (26 +/- 10 cells/mm(2)). Conclusion: The incubation of a porcine aortic valve matrix with a PG concentrate creates a bioactive matrix. However, further fine-tuning of the PG concentration is necessary to take full advantage of platelet growth factor interaction between cells and the extracellular matrix in order to optimize cellular repopulation