Histologic Evaluation of Explanted Tissue-Engineered Bovine Pericardium (CardioCel).

CardioCel is a bovine pericardium that is subjected to a novel anticalcification tissue-engineering process. We present the histopathologic findings of human explants of CardioCel that were used in operations for congenital heart disease in children. Six explants were identified from 140 patients undergoing CardioCel implants from October 2012 to March 2015. CardioCel explants were evaluated histologically using hematoxylin and eosin, Masson trichrome, and immunohistochemical staining. A variable inflammatory response was seen in the surrounding native tissue, but not within the CardioCel graft in any of the explants. A neointimal layer of varying thickness developed on the visceral surface of 5 CardioCel explants with endothelialization of the longest duration explant. A granulation tissue layer developed on the parietal surface of the graft (consistently thicker than the neointima). Maintained collagen fiber architecture (laminated) and variable fibroblastic invasion (which increased with the age of the implant) were identified in all 6 cases. Scattered capillary vessels were noted in the majority of the explants with new collagen fibers in one, suggesting early remodeling. Calcium was seen in 1 explant at the interface of the graft and inflammatory response on its parietal surface. Evidence of graft remodeling was noted in the majority of the explants without inflammatory cells or calcification within the explanted graft material. A noticeable feature was the differential thickness of the host reaction to the parietal compared with the visceral surface of the graft. We will continue to evaluate CardioCel as a cardiovascular substitute for extracardiac and intracardiac reconstructions.