Heart transplantation (HTx) remains an option for patients with cardiac diseases. However, humoral and cell mediated immune responses represent a major obstacle for long-term survival. The aim of the study is to determine the origin and role of exosomes that are induced following HTx in a murine model of heterotopic HTx.

Following syngeneic HTx (C57BL/6) rabbit anti-myosin (200[micro]g/ml) or control were administered (days 0,7,14). Sera was collected following cessation of heart beat and analyzed for Abs against cardiac self-antigens (SAgs) Myosin (Myo) and Vimentin (Vim) by ELISA. Cytokines were determined by ELISpot. Exosomes from sera were isolated and characterized by electron microscopy. qRT-PCR was performed for miR-155, miR-21 expression. Serum exosomes isolated from control or rejected mice (100ug/ml) were administered following syngeneic HTx (days 0,3,6,15). Sera from human cardiac allograft recipients with CAV (n=5) were analyzed for Abs to SAgs by ELISA and exosomes were isolated and characterized.

Syngeneic HTx administered with Abs to Myo were rejected on day 7. Sera from the rejected animals developed Abs to Vim and Myo and demonstrated increased frequency of T-cells secreting IFN-γ and IL-17. Exosomes were induced and released into sera in anti-Myo administered rejected mice and expressed Myo and Vim on surface. qRT-PCR demonstrated upregulation of miR-155, miR-2, and miR-31. Administration of exosomes isolated from rejected mice also induced rejection of syngeneic HTx. Sera developed Abs to Myo and Vim. Cardiac transplant recipients with CAV developed Abs to SAgs Myo and Vim and induced exosomes containg SAgs. In addition, immunoregulatory miRNAs, miR-155, miR-133b, miR-21, and miR-31 were significantly higher in CAV compared to stable.

Administration of Abs to cardiac Myo following heterotopic syngeneic HTx resulted in rejection of hearts by day 7. Sera from rejected animals developed immune responses to SAgs and induced exosomes expressing SAgs and immune-regulatory miRNA. Administration of exosomes also induced syngeneic cardiac rejection and developed immune response against SAgs. Exosomes isolated from sera from cardiac transplant recipients with CAV but not stable express SAgs and contained several immune-regulatory miRNAs. Therefore exosomes may play an important role in augmenting immune responses leading to rejection.

CITATION INFORMATION: Sharma M, Gunasekaran M, Xu Z, Steward N, Liu W, Benshoff N, Mohanakumar T. Exosomes Expressing Cardiac Self-Antigens (Myosin and Vimentin) and Immuno-Regulatory miRNA Induce Graft Rejection. Am J Transplant. 2016;16 (suppl 3).

« Back to 2016 American Transplant Congress