Tissue regeneration patterns in acellular bovine pericardia implanted in a canine model as a vascular patch.

It was noted in our previous study that acellular tissues can provide a natural microenvironment for host cell migration and proliferation to accelerate tissue regeneration. The purpose of this study was to further investigate the tissue regeneration patterns in acellular bovine pericardia fixed with glutaraldehyde or genipin as a biological patch to repair a defect in the pulmonary trunk in a canine model. The implanted samples were retrieved at distinct durations postoperatively. The structural remodeling of retrieved samples was then examined. It was found that the degree of inflammatory reaction observed for the genipin-fixed acellular patch was significantly less than its glutaraldehyde-fixed counterpart. At 1 month postoperatively, intimal thickening was found on the inner surfaces of both studied groups. The intimal thickening observed on the glutaraldehyde-fixed acellular patch was significantly thicker than its genipin-fixed counterpart. An intact layer of endothelial cells was found on the intimal thickening of the genipin-fixed acellular patch, whereas endothelial cells did not universally and totally cover the entire surface of the glutaraldehyde-fixed acellular patch. Additionally, fibroblasts with neocollagen fibrils and myofibroblasts were observed in the acellular patches for both studied groups, an indication of tissue regeneration. This phenomenon was more prominent for the genipin-fixed acellular patch than its glutaraldehyde-fixed counterpart. At 6 months postoperatively, foci of chondroid and/or bony metaplasia were found in each retrieved sample for both studied groups. The observed adverse response of chondroid metaplasia may be attributed to a compliance mismatch at the implanted site of the canine pulmonary trunk after implantation or a lack of angiogenesis in the regenerated tissue observed at 1 month postoperatively. Bony metaplasia may then develop as in other chondroid tissues. It was reported that ischemia is a usual cause of metaplasia.