Different Patterns of Renal Cell Killing After Warm and Cold Ischemia

Abstract

Kidneys preserved for transplantation surgery sustain injuries caused by cold ischemia during storage. Additionally, kidneys harvested from non-heart-beating donors encounter the stress of warm ischemia. The aim of this study was to determine the specific cell types losing viability after warm and cold ischemia. In warm ischemia studies, the pedicles of left kidneys of Lewis rats were cross-clamped for up to 90 min. In cold ischemia studies, kidneys were flushed with cold University of Wisconsin solution and stored up to 48h at 0-1 degrees C. After warm or cold ischemia, kidneys were perfused via the renal arteries with Krebs-Henseleit bicarbonate (KHB) buffer at 37 degrees C, followed by trypan blue to label the nuclei of nonviable cells. Warm ischemia for 90 min caused renal failure and led to injury of proximal tubular cells, e.g., loss of brush borders, cast formation and trypan blue labeling. Cold ischemia for 48 h also caused renal failure but, unlike warm ischemia, caused trypan blue labeling of glomerular podocytes and peritubular endothelial cells. In warm ischemia-induced injury, electron microscopy showed shedding of microvilli and marked swelling of proximal tubular cells, microvilli and mitochondria. In cold ischemia-induced injury, podocytes were blebbed and swollen, and their pedicels were detached from the basement membrane, but disruption in proximal tubules was milder. In conclusion, warm ischemia triggers injury primarily to proximal tubular cells, whereas cold ischemia damages glomerular podocytes and peritubular endothelial cells in addition to proximal tubules.

Prognostic value of intraoperative renal tissue oxygenation measurement on early renal transplant function

“…We speculate that tissue oxygenation and microvascular perfusion in the kidney medulla might even be lower than in the cortical areas we could monitor. Moreover, in renal function the cortical areas are those of most functional importance where tubular necrosis occurs [18]. This is supported by our finding of delayed function in grafts with low intraoperative lHbO 2 and microvascular perfusion.…”

Cold Preservation Mediated Renal Injury: Involvement of Mitochondrial Oxidative Stress

“…Cells exposed to cold storage have been shown to sustain mitochondrial injury and cell death. [14,17,34,36] Our data using a novel rodent model of short-term cold renal preservation demonstrate that cold I/R induces significant renal injury that is accompanied by elevations in oxidant production and mitochondrial dysfunction. This appears to be the first report showing that minimal cold preservation (i.e., 40 minutes) in vivo results in early renal and mitochondrial dysfunction.…”

“…The adverse effects of extended periods of cold renal preservation have been demonstrated using animal [16,17,32,33] and cellular [14,15,34,35] models. Cells exposed to cold storage have been shown to sustain mitochondrial injury and cell death.…”

“…Other studies using a more complex model whereby kidneys are isolated, exposed to longer periods of cold storage (48-72 hr), and then transplanted have demonstrated significant renal injury following 7-14 days post-transplantation. [17,37] Furthermore, numerous studies use recipient survival subsequent to renal transplantation as the index of renal damage following cold preservation. In order to determine mechanisms involved with renal dysfunction, our studies focused on earlier stages of renal damage following cold preservation.…”

“…Mitochondria appear to be a key target for injury during both cold preservation and warm renal ischemia. [14,17] In this regard, our laboratory has demonstrated that the major antioxidant in the mitochondria, manganese superoxide dismutase (MnSOD), is a target of tyrosine nitration and inactivation during renal transplantation (human and rodent) [18,19] and warm renal I/R. [10,20] In a recent review by Salahudeen et al, it was stated that few (if any) studies had been designed to explore and compare the mechanism of reperfusion injury in cold preserved organs versus the more commonly studied warm I/R injury.…”