Immune-mediated rejection of donor tissues is one of the largest challenges in transplant biology. While routine biopsy to monitor transplanted organs can be informative, this procedure is invasive and carries several risks. In this episode, Prashanth Vallabhajosyula and colleagues evaluated changes in transplant-derived exosomes in murine models and human transplant recipients. Their work indicates that changes in donor-derived exosomes can be used to noninvasively monitor transplant rejection.
In transplantation, there is a critical need for noninvasive biomarker platforms for monitoring immunologic rejection. We hypothesized that transplanted tissues release donor-specific exosomes into recipient circulation and that the quantitation and profiling of donor intra-exosomal cargoes may constitute a biomarker platform for monitoring rejection. Here, we have tested this hypothesis in a human-into-mouse xenogeneic islet transplant model and validated the concept in clinical settings of islet and renal transplantation. In the xenogeneic model, we quantified islet transplant exosomes in recipient blood over long-term follow-up using anti-HLA antibody, which was detectable only in xenoislet recipients of human islets. Transplant islet exosomes were purified using anti-HLA antibody–conjugated beads, and their cargoes contained the islet endocrine hormone markers insulin, glucagon, and somatostatin. Rejection led to a marked decrease in transplant islet exosome signal along with distinct changes in exosomal microRNA and proteomic profiles prior to appearance of hyperglycemia. In the clinical settings of islet and renal transplantation, donor exosomes with respective tissue specificity for islet β cells and renal epithelial cells were reliably characterized in recipient plasma over follow-up periods of up to 5 years. Collectively, these findings demonstrate the biomarker potential of transplant exosome characterization for providing a noninvasive window into the conditional state of transplant tissue.
Prashanth Vallabhajosyula, Laxminarayana Korutla, Andreas Habertheuer, Ming Yu, Susan Rostami, Chao-Xing Yuan, Sanjana Reddy, Chengyang Liu, Varun Korutla, Brigitte Koeberlein, Jennifer Trofe-Clark, Michael R. Rickels, Ali Naji