Effects Of Losartan On Endothelial Progenitor Cell And Glomerular Endothelial Cell In The Remnant Kidney Model

【Objective】The study investigated effects of Angiotension II(Ang II) receptor blocker(ARB) , losartan on peripheral blood endothelial progenitor cell(EPC) and glomerular microvascular injury's repair in the remnant kidney model. This study will provide new theoretical and experimental evidences for ARB in the treatment of chronic kidney disease.【Methods】Thirty-two Sprague-Dawley rats weighing 200-250g were randomized to three groups.The sham group underwent sham surgery consisting of laparotomy and manipulation of both kidneys before wound closure. The other 24 rats all underwent subtotal nephrectomy (STNx) performed by right subcapsular nephrectomy and infarction of approximately two-thirds of the left kidney by selective ligation of two of three to four extrarenal branches of the left renal artery. Animals were then randomly assigned to two groups: remnant kidney model group or losartan treated group (25mg/kg/d).Dissolvent was given to the rats in sham group and remnant kidney model group. 15 weeks later, urine was collected and 24h urine protein was tested before the rats were killed. Blood was drawn from heart and then serum albumn, urea nitrogen, creatinine, cholesterol and triglyeride were measured. Peripheral blood mononuclear cells (MNC) were isolated by a density-gradient centrifuge method. MNC were stained with a fluorescein isothiocyanate (FITC) conjugated anti-CD34 monoclonal antibody for flow cytometric analysis. MNC with CD34+ were assayed as tentative EPC.MNC were also cultured to assay EPC colony formation. EPC colonies were observed and numerated under low power microscope. EPC colonies were detected expression of endothelial marker CD31 by immunofluorescence technique. RECA-1 expression in kidneys was determined by immunohistochemistry and histological changes in kidneys were detected by periodic acid-silver masson stain.【Results】1. Compared with sham group, serum urea nitrogen,creatinine,cholesterol, triglyeride and 24h urine protein were markedly increased in remnant kidney model group (P<0.05).Compared with remnant kidney model group,serum urea nitrogen,creatinine,cholesterol,triglyeride and 24h urine protein were significantly ameliorated in losartan treated group(P<0.05). But serum albumn showed no significant difference among sham group, remnant kidney model group and losartan treated group (P>0.05).2. The percentage of CD34+ cell (%MNC)was significantly(P<0.05)lower in remnant kidney model group than in sham group (0.35±0.08% vs 1.29±0.21%).Losartan markedly(P<0.05) increased the percentage of CD34+ cell in remnant kidney model compared with that in untreated remnant kidney model group(1.03±0.28% vs 0.35±0.08%).3. MNC were cultured to EPC colony formation cells and assayed positive for CD31 by immunofluorescence.The number of EPC colonies was significantly (P<0.05)lower in remnant kidney model group than in sham group(2.50±0.65 vs 18.60±5.68).Losartan markedly(P<0.05)increased the number of EPC colony in remnant kidney model compared with that in untreated remnant kidney model group(14.60±3.65 vs 2.50±0.65).4. Kidney histopathology showed the glomerularsclerosis index(GSI)was higher in remnant kidney model group than in sham group(0.89±0.12 vs 0.29±0.05)(P<0.05), but losartan markedly(P<0.05)reduced the GSI in remnant kidney model(0.34±0.02 vs 0.89±0.12)(P<0.05). 5. Kidney immunohistochemistry showed glomerular capillary endothelial cell density was lower in remnant kidney model group than in sham group(1.99±0.31 vs7.21±0.57)(P<0.05), but losartan markedly(P<0.05)increased the glomerular capillary endothelial cell density in remnant kidney model(5.93±0.70 vs 1.99±0.31)(P<0.05).【Conclusion】1. Losartan markedly reduces the serum cholesterol, triglyeride and 24h urine protein excretion and improves renal function.2. Losartan treatment increases EPC number and enhances EPC colony formation.3. Losartan increases glomerular capillary endothelial cell density and attenuates glomerular fibrosis in remnant kidney model.4. Glomerular capillary endothelial cell repair may be related to the mobilization of EPC through Losartan treatment.