Ang1 Reduces Ischemia-Reperfusion Injury-Induced Microvascular Dysfunction and Chronic Rejection in Rat Cardiac Allografts

Abstract

Introduction: Ischemia-reperfusion injury (IRI) is an inevitable factor in current clinical solid organ transplantations resulting in microvascular dysfunction, innate immunity activation and correlating with the later development of chronic rejection. Angiopoietin-1 (Ang1) is endothelial cell-specific growth factor having essential role in vascular development and in endothelial cell maintenance. We investigated the effects of preoperative ex vivo intracoronary perfusion with recombinant variant of native Ang1 (COMP-Ang1) on IRI-associated vascular leakage, no-reflow phenomenon, cardiomyocyte damage, innate immune activation and subsequent development of cardiac fibrosis and allograft vasculopathy. Methods: We performed fully MHC-mismatched cardiac allograft transplantations between DA donor and WF recipient rats. We perfused the donor hearts intracoronarily with COMP-Ang1 or control-PBS perioperatively and preserved the graft was in +4 °C PBS for 4h before transplantation. We analyzed vascular permeability and perfusion at 30 mins, IRI induced myocardial damage and inflammation at 6 h and chronic rejection at 8 weeks after transplantation. Results: COMP-Ang1 reduced IRI-induced microvascular dysfunction by reducing vascular permeability measured by Evans Blue absorbance and increasing the number of perfused vessels 30 min after reperfusion. COMP-Ang1 also significantly reduced endothelial activation, measured by VCAM1 immunoreactivity, ED1+ macrophage and MPO+ neutrophil influx and innate immune activation 6h after reperfusion. Furthermore, periopreative COMP-Ang1 treatment reduced cardiac fibrosis and allograft vasculopathy analyzed 8 weeks after transplantation. (Figure 1)[Figure 1]Conclusion: Here, we show that COMP-Ang1 protects cardiac allografts from IRI-induced microvascular dysfunction and from subsequent chronic allograft rejection. Such results suggest COMP-Ang1 as clinically feasible method for early allograft protection.