QUANTIFYING THE IMMUNE RESPONSE TO TISSUE ENGINEERED EXTRACELLULAR MATRIX

Abstract

Purpose: Tissue engineered heart valves have been created in order to reduce the xenoreactive immune response thought to be responsible for structural valve deterioration (SVD) of bioprosthetic heart valve replacements. Our study looks to elucidate whether tissue engineering a commercially available porcine extracellular matrix will significantly attenuate the xenoreactive immune response when compared to the wild-type matrix. Methods: Samples of whole blood, human pericardium, and bone marrow were collected from patients undergoing elective cardiac surgery. We decellularized the wild-type matrix using an established 3-day decellularization process. We then isolated human mesenchymal stem cells (hMSCs) from the collected human bone marrow that we used to recellularize the decellularized matrix. The wild-type, decellularized and recellularized matrix tissues, as well as autologous human pericardium as a control, were exposed to whole blood collected from each patient. On days 1, 3, and 5, samples of blood were collected, centrifuged and the serum stored. Enzyme Linked Immunosorbent Assay (ELISA) was performed to quantify proinflammatory cytokine production. Results: At days 1, 3, and 5, there was a significant reduction in the concentration of IL-1B cytokine production in each sample of serum exposed to decellularized and recellularized matrix when compared to the wild-type matrix, and a significant reduction in the recellularized matrix when compared to the decellularized tissue. There was a significant reduction in TNF-a concentration at days 1 and 3 for decellularized and days 3 and 5 for recellularized when compared to the wild-type matrix.Conclusion: Decllularization and recellularization with autologous hMSCs significantly attenuates the xenoreactive immune response when compared to the wild-type matrix. Therefore, tissue engineering a scaffold for bioprosthetic valve replacements may serve as an effective choice for patients to significantly reduce the xenoreactive immune response previously shown to be responsible for SVD, increasing the durability and longevity of a bioprosthetic heart valve made from this tissue engineered scaffold. University Hospital Foundation, University of Alberta. Edmonton Civic Employees Research Award.