Abstract 700: Recellularization of Acellular Xenogenic Scaffold With Autologous Human Mesenchymal Stem Cells Rescues the Xenoreactive Immune Response

Abstract

Background: Pre-clinical evidence suggests that structural valve deterioration (SVD) of bioprosthetic xenogenic tissue heart valves (XTHV) is a result of chronic immune rejection. Recellularization of XTHVs with human autologous cells represents one potential strategy to prevent this xenoreactive immune response and mitigate SVD. Methods: Bone marrow, human pericardium and heparinized whole blood was collected from adult patients undergoing elective cardiac surgery. Decellularized bovine pericardium underwent recellularization with hMSCs, which were isolated and cultured from the bone marrow, via co-incubation to allow for cell seeding. To examine the cell mediated immune response, we performed immunofluorescent staining for CD68+ macrophages and CD3+ T-cells and performed a proliferation assay to quantify T-cell proliferation. To investigate the humoral immune response, we performed an enzyme linked immunosorbent assay for pro-inflammatory cytokines TNF-α and INF-γ. Serum and PBMCs were collected for subsequent biochemical and flow cytometric analysis. Results: We show that decellularized bovine pericardium, exposed to human serum, had significantly decreased T-cell activation, represented by TNF-αand INF-γexpression, as well as a significant decrease in T-cell proliferation, when compared to wild-type bovine pericardium (p<0.01). Moreover, when decellularized bovine pericardium was recellularized with autologous hMSCs and exposed to human serum, there was an additional decrease in TNF-α, INF-γexpression along with a further significant decrease in T-cell proliferation, when compared to both wild-type and decellularized bovine pericardium (p<0.01). Importantly, recellularized XTHVs exposed to human serum had an equivalent expression of TNF-α, INF-γ and T-cell proliferation when compared to native human pericardium exposed to autologous human serum. Conclusions: Taken together, our data suggest that autologous human MSC recellularization of decellularized bovine pericardium abrogates the xenoreactive immune response. As such, autologous hMSC recellularization of an acellular xenogenic scaffolds may be an effective approach to decrease the progression of bioprosthetic SVD.