(P010) IMMUNE ANALYSIS OF TISSUE ENGINEERED PORCINE AORTIC VALVE LEAFLETS AFTER ALPHA-GALACTOSE CLEAVAGE

Background: Bioprosthetic heart valves are prone to structural valve deterioration (SVD) due to an inflammatory immune response resulting in calcification, stenosis, and ultimately valve failure. The antigenicity of xenografts is thought to underlie the immune response, with galactose-α-1,3-galactose (alpha-gal) the principal antigen of investigation. The objective of this study is to further characterize the role of alpha-gal in SVD and determine whether the addition of alpha-gal cleavage to tissue engineered porcine aortic valve (PAV) leaflets will attenuate the xenoreactive humoral immune response.

METHODS AND RESULTS: Samples of human pericardium, bone marrow, and whole blood were collected from patients undergoing elective cardiac surgery. PAV leaflets were excised from the hearts of female juvenile Yorkshire pigs, decellularized with or without alpha-gal cleavage via green coffee bean alpha-galactosidase, and recellularized with allogeneic human mesenchymal progenitor cells (hMSCs). These tissue-engineered constructs, as well as native PAV leaflets and autologous human pericardium, were exposed to human blood. At 1, 3, and 5 days proinflammatory cytokine production was quantified via enzyme-linked immunosorbent assays. On days 1, 3, and 5 there was a significant reduction in TNF-α and IL1-β concentration in the serum exposed to decellularized and recellularized PAV leaflets as compared to native PAV leaflets, as well as a significant reduction in the recellularized PAV tissue compared to the decellularized tissue. Compared to the decellularized tissue, the addition of alpha-gal cleavage reduced the TNF-α concentration on day 5. Similarly, as compared to the recellularized tissue, the addition of alpha-gal cleavage reduced the IL1-β concentration on day 3.

Conclusion: Allogenic recellularization of PAV tissue with hMSCs attenuates the xenoreactive immune response. Independent of the decellularization and recellularization processes, alpha-gal cleavage reduced the xenoreactive immune response to PAV tissue only at select time points. Therefore, other antigenic epitopes on xenogeneic tissue in addition to alpha-gal likely contribute to the immune-mediated SVD affecting bioprosthetic heart valves.