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 Transplantation

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 3

Transplant islet exosome purification and characterization of its intra-exosomal cargo.

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Transplant islet exosome purification and characterization of its intra-...
(A) Transmission electron microscopy of HLA-A antibody–bound content from xenoislet plasma exosomes showed that intact exosomes (range 40–100 nm; arrow) were being enriched. (B) NanoSight analysis of HLA-A–bound exosome fraction for coexpression of the β cell marker FXYD2 showed high expression only in N-xeno and human islet culture samples, but not in human plasma or naive mouse plasma HLA-A–bound fractions (P = 0.008; 1 of 5 experiments shown). (C and D) Western blot (C) and RT-PCR (D) analysis of HLA-A–bound exosomes showed presence of FXYD2 and islet endocrine hormones from xenoislet plasma and human islet culture supernatant samples, but not human plasma and naive mouse plasma (negative controls) samples (P = 0.008; 1 of 5 experiments shown). Islet graft served as positive control. (E and F) Plasma HLA-A–bound exosomes 14 days after islet graftectomy (n = 6) showed low surface coexpression of FXYD2 on NanoSight fluorescence (E). Western blot analysis showed absence of insulin and FXYD2 proteins in this fraction (F). One of six experiments is shown (P = 0.002). (G–I) HLA-A–bound exosomes from R-xeno plasma showed decreased coexpression of FXYD2 on NanoSight fluorescence (G). Western blot (H) and RT-PCR (I) analysis showed decreased levels of FXYD2 and insulin proteins and mRNAs compared with N-xeno sample (P = 0.002). Controls include naive mouse HLA-A–bound content and xenoislet graft tissue. One of six experiments is shown.