Urinary cystatin C and NGAL as early biomarkers for assessment of renal ischemia-reperfusion injury: a serum marker to replace creatinine?

PURPOSE: To assess application of cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) as biomarkers for renal ischemic injury. We also evaluated the use of allopurinol as a renoprotective agent. A second goal was to assess cystatin C as a biomarker in patients undergoing partial nephrectomy. METHODS: Using 58 Sprague-Dawley rats, we evaluated urinary cystatin C (n=26) and NGAL (n=32) as a biomarker for renal ischemia injury. Half of the rats were pretreated with allopurinol; the other cohort served as a control. The right renal hilum was ligated in all rats, thereby creating a solitary kidney model. After a 30-minute stabilization period, the left hilum was clamped for time periods of 15, 30, and 60 minutes. Urinary levels of cystatin C and NGAL were then measured at the following time points: Preclamp (after the 30-minute stabilization period) and postclamp (30, 45, and 60 minute periods after unclamping). For our clinical subjects, serum cystatin C levels (n=17) were obtained preoperatively, at the induction of anesthesia before robot-assisted partial nephrectomy, immediately postoperatively, and on postoperative days 1 and 2. Three of these patients had their tumors excised off clamp and served as controls. We then estimated glomerular filtration rate by using the Creatinine-Cystatin C Equation. RESULTS: Urinary levels of cystatin C and NGAL increased after renal clamping. The 30-minute period of ischemia demonstrated the greatest increase of these biomarkers. Allopurinol did appear to serve a renoprotective function in those animals undergoing 30-minute clamp times. In our clinical patients, the serum cystatin C levels did increase at each postoperative time point, but remained nonelevated in the control group. CONCLUSIONS: Cystatin C and NGAL both appear to be useful biomarkers of renal injury. Studies with larger numbers are needed, however. Also, allopurinol does exhibit renoprotective effects against ischemic injury.

Leukocyte inflammatory response in a rat urinary bladder regeneration model using porcine small intestinal submucosa scaffold.

Small intestinal submucosa (SIS) is a biodegradable scaffold that supports bladder regeneration after partial cystectomy. We sought to define the inflammatory response present in a rat bladder augmentation model using distal ileal SIS. Fifteen Sprague-Dawley rats underwent hemi-cystectomy followed by anastomosis of a bladder patch of SIS. Bladders were excised after days 2, 7, 14, 28, and 56. Tissue regeneration was evaluated by standard hematoxylin and eosin. Immunohistochemical staining was used to quantify neutrophils, macrophages, eosinophils, and mast cells. Total cell counts per unit area were compared between native and graft portions of the bladder for each cell type across the entire time course. Statistical analyses were conducted with the Wilcoxon Rank-Sum and Kruskal-Wallis tests. All tests were two-sided with significance set at p < 0.05. These inflammatory responses evolved consistently across all bladders over time. Neutrophil and eosinophil numbers were highest at day 2 and decreased over the 56-day period. In contrast, macrophage and mast cell numbers were low at days 2, 7, and 14; peaked at day 28; and decreased once again at day 56. Cell counts at native and graft sites were equivalent for all cell types, except neutrophils, which were more commonly found in the graft (124 vs. 24 cells/mm(2), p = 0.009). Thus, the inflammatory processes change over time during SIS-mediated bladder regeneration. Similar cell densities are present between the native and SIS portions of the bladder, but neutrophils predominate in the graft areas.