Tissue-specific exosome biomarkers for noninvasively monitoring immunologic rejection of transplanted tissue
Prashanth Vallabhajosyula, … , Michael R. Rickels, Ali Naji
Prashanth Vallabhajosyula, … , Michael R. Rickels, Ali Naji
Published March 20, 2017
Citation Information: J Clin Invest. 2017;127(4):1375-1391. https://doi.org/10.1172/JCI87993.
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Research Article Immunology

Tissue-specific exosome biomarkers for noninvasively monitoring immunologic rejection of transplanted tissue

Abstract

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.

Authors

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

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Figure 2

Transplant islet exosome profiles herald early acute rejection.

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Transplant islet exosome profiles herald early acute rejection. (A) Kine...
(A) Kinetics of HLA exosome signal in xenoislet recipients during evolution of acute rejection is shown in scatter plot. Donor-sensitized syngeneic leukocytes were infused to induce rejection, and HLA exosome signal (red, y axis) was profiled at the following days: 0 (4 hours), 1, 2, 3, 5, and 7 (n = 8 animals per time point). The signal significantly decreased from day 0 to 1 (*P = 7.4 × 10–7), day 1 to 2 (**P = 0.045), day 2 to 5 (***P = 0.0008), and day 3 to 7 (****P = 1.7 × 10–6). Mean fasting blood glucose only increased on day 7 (blue line, secondary y axis). HLA exosome signal after placebo infusion (black; days 0–3) was similar between time points (n = 8 per time point, P = 0.588). Controls included athymic mouse, C57BL/6, and xenoislet (n = 8 for each). Summarized data (mean ± SD) from 2 independent experiments are shown. (B) Daily i.p. glucose tolerance tests are shown (mean values, n = 8 per time point). On day 6, 3 of 8 animals showed impairment in glucose clearance (bottom). (C) Receiver operating characteristic curves for HLA exosome signal (red), total plasma exosome quantity (blue), and median exosome size (green) are shown. (D) Representative islet graft histology (1 of 4) is shown for days 1, 2, 3, and 5. H&E and IHC for insulin (brown, red arrow) and T cells (CD3, pink, black arrow) are shown. On day 1, viable islet clusters with very minimal T cell infiltrate were seen. By day 5, dense T cell infiltration with islet destruction was seen, even though plasma glucose, glucose tolerance tests, and C-peptide levels were normal. (E) Plasma T cell exosome signal (CD3 signal) is shown (mean ± SD). Compared with xenoislet, Nu/J WT, and third-party C57BL/6 controls, samples from day 0 to 7 showed persistently elevated CD3 exosome signal (n = 8 per time point, P = 5.78 × 10–10).