Donor Heart Treatment With COMP-Ang1 Limits Ischemia-Reperfusion Injury and Rejection of Cardiac Allografts.

The major cause of death during the first year after heart transplantation is primary graft dysfunction due to preservation and ischemia-reperfusion injury (IRI). Angiopoietin-1 is a Tie2 receptor-binding paracrine growth factor with anti-inflammatory properties and indispensable roles in vascular development and stability. We used a stable variant of angiopoietin-1 (COMP-Ang1) to test whether ex vivo intracoronary treatment with a single dose of COMP-Ang1 in donor Dark Agouti rat heart subjected to 4-h cold ischemia would prevent microvascular dysfunction and inflammatory responses in the fully allogeneic recipient Wistar Furth rat. COMP-Ang1 reduced endothelial cell-cell junction disruption of the donor heart in transmission electron microscopy during 4-h cold ischemia, improved myocardial reflow, and reduced microvascular leakage and cardiomyocyte injury of transplanted allografts during IRI. Concurrently, the treatment reduced expression of danger signals, dendritic cell maturation markers, endothelial cell adhesion molecule VCAM-1 and RhoA/Rho-associated protein kinase activation and the influx of macrophages and neutrophils. Furthermore, COMP-Ang1 treatment provided sustained anti-inflammatory effects during acute rejection and prevented the development of cardiac fibrosis and allograft vasculopathy. These results suggest donor heart treatment with COMP-Ang1 having important clinical implications in the prevention of primary and subsequent long-term injury and dysfunction in cardiac allografts.

Angiopoietin-2 inhibition prevents transplant ischemia-reperfusion injury and chronic rejection in rat cardiac allografts.

Transplant ischemia-reperfusion injury (Tx-IRI) and allograft dysfunction remain as two of the major clinical challenges after heart transplantation. We investigated the role of angiopoietin-2 (Ang2) in Tx-IRI and rejection using fully MHC-mismatched rat cardiac allografts. We report that plasma levels of Ang2 were significantly enhanced in the human and rat recipients of cardiac allografts, but not in the rat recipients of syngrafts, during IRI. Ex vivo intracoronary treatment of rat cardiac allografts with anti-Ang2 antibody before 4-h cold preservation prevented microvascular dysfunction, endothelial cell (EC) adhesion molecule expression and leukocyte infiltration, myocardial injury and the development of cardiac fibrosis and allograft vasculopathy. Recipient preoperative and postoperative treatment with anti-Ang2 antibody produced otherwise similar effects without effecting microvascular dysfunction, and in additional experiments prolonged allograft survival. Recipient preoperative treatment alone failed to produce these effects. Moreover, ex vivo intracoronary treatment of allografts with recombinant Ang2 enhanced Tx-IRI and, in an add-back experiment, abolished the beneficial effect of the antibody. We demonstrate that neutralization of Ang2 prevents EC activation, leukocyte infiltration, Tx-IRI and the development of chronic rejection in rat cardiac allografts. Our results suggest that blocking Ang2 pathway is a novel, clinically feasible, T cell-independent strategy to protect cardiac allografts.

Donor simvastatin treatment prevents ischemia-reperfusion and acute kidney injury by preserving microvascular barrier function.

Ischemia-reperfusion injury (IRI) after kidney transplantation may result in delayed graft function. We used rat renal artery clamping and transplantation models to investigate cholesterol-independent effects of clinically relevant single-dose peroral simvastatin treatment 2 h before renal ischemia on microvascular injury. The expression of HMG-CoA reductase was abundant in glomerular and peritubular microvasculature of normal kidneys. In renal artery clamping model with 30-min warm ischemia, simvastatin treatment prevented peritubular microvascular permeability and perfusion disturbances, glomerular barrier disruption, tubular dysfunction and acute kidney injury. In fully MHC-mismatched kidney allografts with 16-h cold and 1-h warm ischemia, donor simvastatin treatment increased the expression of flow-regulated transcription factor KLF2 and vasculoprotective eNOS and HO-1, and preserved glomerular and peritubular capillary barrier integrity during preservation. In vitro EC Weibel-Palade body exocytosis assays showed that simvastatin inhibited ischemia-induced release of vasoactive angiopoietin-2 and endothelin-1. After reperfusion, donor simvastatin treatment prevented microvascular permeability, danger-associated ligand hyaluronan induction, tubulointerstitial injury marker Kim-1 immunoreactivity and serum creatinine and NGAL levels, and activation of innate and adaptive immune responses. In conclusion, donor simvastatin treatment prevented renal microvascular dysfunction and IRI with beneficial effects on adaptive immune and early fibroproliferative responses. Further studies may determine potential benefits in clinical cadaveric kidney transplantation.