Pathologic findings in preclinical and early clinical kidney xenotransplantation

PURPOSE OF REVIEW: After many decades of experimental studies and the advent of genetic engineering for pig organs, xenotransplantation has finally reached clinical application. Clinical trials are beginning, and a review of the recent preclinical and clinical studies is paramount. More specifically, reviewing the pathologic findings in biopsies and terminal samples of transplanted pig organs are integral to assessing xenograft acceptance and clinical success. RECENT FINDINGS: This review aims to summarize the current literature in xenotransplantation and enumerate both typical and novel pathological findings in xenografts. This holds an opportunity to identify both diagnostic clues and gaps that are critical to treatment protocol modifications and to improving xenograft survival. While thrombotic microangiopathy and antibody mediated rejection are known pathologic entities in xenograft pathology, we re-examine their occurrence in the context of other diagnostic parameters, and we revisit the importance of integrating clinical findings and molecular techniques to aid pathological diagnosis. We also describe the novel findings in xenografts from both nonhuman primate and human recipients. SUMMARY: With the recently observed pathological features, a structured approach to xenograft pathology diagnosis can be proposed for use in clinical practice and is an effort that can impact therapeutic and genetic modification strategies.