Effects of unfractionated heparin, low molecular weight heparin and r-hirudin on leukocyte adhesion in ischemia/reperfusion

Tissue Injury Protection: The Other Face of Anticoagulant Treatments in the Context of Ischemia and Reperfusion Injury with a Focus on Transplantation

Organ transplantation has enhanced the length and quality of life of patients suffering from life-threatening organ failure. Donors deceased after brain death (DBDDs) have been a primary source of organs for transplantation for a long time, but the need to find new strategies to face organ shortages has led to the broadening of the criteria for selecting DBDDs and advancing utilization of donors deceased after circulatory death. These new sources of organs come with an elevated risk of procuring organs of suboptimal quality. Whatever the source of organs for transplant, one constant issue is the occurrence of ischemia-reperfusion (IR) injury. The latter results from the variation of oxygen supply during the sequence of ischemia and reperfusion, from organ procurement to the restoration of blood circulation, triggering many deleterious interdependent processes involving biochemical, immune, vascular and coagulation systems. In this review, we focus on the roles of thrombo-inflammation and coagulation as part of IR injury, and we give an overview of the state of the art and perspectives on anticoagulant therapies in the field of transplantation, discussing benefits and risks and proposing a strategic guide to their use during transplantation procedures.

Fate of culture-expanded mesenchymal stem cells in the microvasculature: in vivo observations of cell kinetics

Vascular delivery of mesenchymal stem cells (MSCs) following myocardial infarction is under clinical investigation. Little is known about the microvascular fate of MSCs. We used intravital microscopy of rat cremaster muscle microcirculation to track intraarterially delivered MSCs. Rat MSCs (average diameter, 23 microm) were bolused into the ipsilateral common iliac artery. Interrogation of an arteriole-venule pair revealed that 92+/-7% (n=6) of MSCs arrest and interrupt flow during first pass at the precapillary level, resulting in decreased flow in the feeding arteriole (velocity decreased from 6.3+/-1.0 to 4.6+/-1.3 mm/sec; P<0.001). MSC deformability evaluated using filtration through polycarbonate membranes revealed that the cortical tension of MSCs (0.49+/-0.07 dyne/cm, n=9) was not different from that of circulating mononuclear cells (0.50+/-0.05 dyne/cm, n=7). When intravital microscopy was performed 3 days following injection, the number of MSCs in the cremaster further decreased to 14% of the initial number, because of cell death in situ. In vivo labeling of the basement membrane revealed that at 1 day, the surviving cells were spread out on the luminal side of the microvessel, whereas at 3 days, they integrated in the microvascular wall. Despite their deformability, intraarterially delivered MSCs entrap at the precapillary level because of their large size, with a small proportion of surviving MSCs integrating in a perivascular niche.