Circulating Donor Lung-specific Exosome Profiles Enable Noninvasive Monitoring of Acute Rejection in a Rodent Orthotopic Lung Transplantation Model

Abstract

Original Basic Science-GeneralBackground. There is a critical need for development of biomarkers to noninvasively monitor for lung transplant rejection. We investigated the potential of circulating donor lung-specific exosome profiles for time-sensitive diagnosis of acute rejection in a rat orthotopic lung transplant model. Methods. Left lungs from Wistar transgenic rats expressing human CD63-GFP, an exosome marker, were transplanted into fully MHC-mismatched Lewis recipients or syngeneic controls. Recipient blood was collected between 4 h and 10 d after transplantation, and plasma was processed for exosome isolation by size exclusion column chromatography and ultracentrifugation. Circulating donor exosomes were profiled using antihuman CD63 antibody quantum dot on the nanoparticle detector and via GFP trigger on the nanoparticle flow cytometer. Results. In syngeneic controls, steady-state levels of circulating donor exosomes were detected at all posttransplant time points. Allogeneic grafts lost perfusion by day 8, consistent with acute rejection. Levels of circulating donor exosomes peaked on day 1, decreased significantly by day 2, and then reached baseline levels by day 3. Notably, decrease in peripheral donor exosome levels occurred before grafts had histological evidence of acute rejection. Conclusions. Circulating donor lung-specific exosome profiles enable an early detection of acute rejection before histologic manifestation of injury to the pulmonary allograft. As acute rejection episodes are a major risk factor for the development of chronic lung allograft dysfunction, this biomarker may provide a novel noninvasive diagnostic platform that can translate into earlier therapeutic intervention for lung transplant patients.

Extracellular Vesicles: Promising Candidates in Transplant Function Monitoring

“…In conclusion, the promising findings as reported in this issues study by Habertheuer et al 3 support the concept that small particles are released from donor cells after transplantation. Moreover, a decrease in this donor-specific signal precedes rejection.…”

“…Recent progress in imaging flow cytometry makes it now possible to quantify and characterize donor organ released EVs in a high throughput manner. 12 In conclusion, the promising findings as reported in this issues study by Habertheuer et al 3 support the concept that small particles are released from donor cells after transplantation. Moreover, a decrease in this donor-specific signal precedes rejection.…”

“…Over the years, multiple markers (eg, urinary chemokines and donor-derived cell-free DNA) are identified as promising candidates in discriminating transplant rejection. 1,2 Here, Habertheuer et al 3 add additional players, donor-specific exosomes, to this candidate list.…”

Donor extracellular vesicle trafficking via the pleural space represents a novel pathway for allorecognition after lung transplantation

“…EVs were isolated as previously described. [12][13][14][15] Lymph nodes and spleen were collected from rats 48 h following pleural injections. Studies were approved by the University of Pennsylvania Institutional Animal Care and Use Committee.…”

“…We have previously reported that donor-specific EVs can be detected in the recipient circulation within hours of engraftment after islet, 12 kidney, 12 heart 13 and lung transplantation. 14 Although these findings suggest that EVs can leave allografts via the bloodstream, it remains unknown whether they can subsequently enter lymphoid tissues from the circulation. If this was the case one would expect donor EVs to be equally distributed throughout all lymph nodes in the body rather than preferentially accumulating in graft-draining lymph nodes.…”