Prolonged cold preservation augments vascular injury independent of renal transplant immunogenicity and function

Background. While prolonged cold ischemia has detrimental effects on graft survival, the mechanisms remain unclear. We tested whether or not cold pres ervation enhances intragraft inflammatory responses and vascular injury. Methods. Rat renal grafts were cold preserved in University of Wisconsin so lution for 2, 4, 6, 12, 24, and 48 hours, and then transplanted into syngen eic recipients and harvested after 24 hours. Frozen sections were examined histologically and stained for vascular cellular adhesion molecule-1 (VCAM- 1), platelet-endothelial cell adhesion molecule-1 (PECAM-1), major histocom patibility complex (MHC) class II, tissue factor, leukocyte function associ ated molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for inflam matory cells. Results. Function did not differ between isografts preserved for shorter (2 to 6 hours) or longer times (12 to 24 hours). Neutrophil influx and that o f LFA-1-positive cells showed similar increases in all groups. Compared wit h short preservation groups, the long preserved grafts had more VLA-4-posit ive ED-1+ monocytic infiltrates adjacent to vessels expressing VCAM-1 (P le ss than or equal to 0.001). Increased preservation duration had no effect o n infiltration with recipient ED-2+ macrophages, MHC class II-positive cell s, or dendritic cells. Decreased color intensity and continuity of PECAM-1 staining indicated loss of endothelial integrity in grafts preserved for lo nger than six hours. Intensity in VCAM-1 staining increased progressively i n grafts preserved for more than six hours and was localized predominantly on the endothelium of elastic vessels. Endothelial cells, vascular smooth m uscle cells, and monocytes expressed increasingly more tissue factor in gra fts preserved for more than six hours, revealing enhanced intragraft procoa gulant capacity. Furthermore, grafts with preservation times of more than s ix hours developed more severe vascular endothelial injury and worse tubula r necrosis scores (P less than or equal to 0.001) compared with grafts with shorter preservation times. Conclusions. Because of the prominent vascular injury, strategies for endot helial protection should be attempted in grafts with long preservation time s in clinical renal transplantation.