Circulating Tissue Specific Extracellular Vesicles for Noninvasive Monitoring of Acute Cellular Rejection in Clinical Heart Transplantation.

BACKGROUND

There remains a critical need for biomarkers of acute cellular rejection (ACR) in heart transplantation. We hypothesized that immunopathophysiology of ACR is reflected via dynamic changes in the protein and RNA cargoes of small extracellular vesicles (sEVs) released by cardiac allograft and T cells into circulation, thus enabling noninvasive window into ACR.

METHODS

T-cell sEVs were enriched using anti-CD3 antibody beads, and antidonor HLA I antibody beads for donor sEVs. Cargoes of donor sEVs (cardiac troponin T [cTnT] protein and mRNA) and T-cell sEVs (CD4, CD8, T-cell receptor proteins, miRNAs [miRs] let 7i, 101b, 21a) were compared with time-matched endomyocardial biopsy samples (n = 70) in 12 patients to postoperative day 120.

RESULTS

Six patients had 11 moderate ACR (15.7%) episodes, 1 had antibody-mediated rejection, and 5 had ≤ mild ACR. By Wilcoxon rank-sum tests, cTnT protein ( P  = 6.04 × 10 -5 ) and mRNA ( P  = 6.87 × 10 -7 ) were decreased with moderate ACR compared with grades 0/1 ACR. T-cell sEV CD4, CD8, and TCR protein cargoes ( P ≤ 3.92 × 10 -5 ) and miRs let 7i, 101b, and 21a ( P ≤ 9.05 × 10 -5 ) were increased with moderate ACR. Successful treatment of moderate ACR led to dynamic reversal in sEV profiles, especially donor heart sEV cTnT mRNA (Spearman coefficient 0.87) and miR 21a (coefficient 0.85).

CONCLUSIONS

Our first investigation in heart transplant patients demonstrated that circulating T cell-sEV and donor heart-sEV profiles enable diagnosis of moderate ACR with high diagnostic accuracy. A large sample cohort external validation study is warranted to better understand diagnostic potential of this platform for ACR monitoring in heart transplantation.