Absence of PAI-1 Results in Direct Podocyte Protection In Vivo
Hai-Chun Yang, Amanda Morden, Ira Pastan, Taiji Matsusaka, Iekuni Ichikawa, Agnes B Fogo. Vanderbilt University Medical Center, Nashville, TN; Florida State University, Tallahassee, FL; National Cancer Institute, Bethesda, MD; Tokai University Medical School, Isehara, Kanagawa, Japan
Background: Plasminogen activator inhibitor-1 (PAI-1) inhibits serine protease activity and directly modulates cell migration. Our previous data in vitro and in the 5/6 nephrectomy model suggests PAI-1 has direct impact on podocytes. To test our hypothesis that absence of PAI-1 protects against direct podocyte injury in vivo, we bred PAI-1-/- mice with NEP 25 mice, in which podocytes express human CD25 receptor under the nephrin promoter, and are selectively injured by injecting immunotoxin (LMB2) that binds to this receptor.
Design: PAI-1-/-/Nep 25 mice (n=10) and PAI-1+/+/ Nep 25 mice (n=8) were exposed to LMB2 toxin (mean dose 11 ng/g BW, i.p.). Mice were sacrificed at day 10 and glomeruli were isolated. Urine total protein/creatinine ratio, glomerulosclerosis index (0-4 scale), podocyte number and differentiation markers were measured.
Results: PAI-1 deficiency did not have any effect on blood pressure; however, kidney function was improved as indicated by the lower body weight (PAI-1-/- 25.78±0.94 vs. WT 30.63±0.10 g, p<0.05), which implied less edema. PAI-1-/- mice had initial increased proteinuria that then returned to WT level. Podocytes were preserved more in PAI-1-/- mice as indicated by increased WT-1 (PAI-1-/- 5.21±0.23 vs. WT 4.02±0.25 WT-1 positive cells/glom, p<0.05). This data and the increased expression of GLEPP-1 (PAI-1-/- 2.43±0.52 vs. WT 1.13±0.22, p<0.05) and synaptopodin (PAI-1-/- 2.23±0.30 vs. WT 1.28±0.30, p<0.05) in PAI-1-/- mice demonstrate that knocking out the PAI-1 gene provided increased podocyte protection against direct immunotoxic injury. The glomerulosclerosis index was also numerically lower, suggesting that PAI-1-/- protected against renal injury after direct podocyte injury (PAI-1-/- 2.12±0.14 vs. WT 2.42±0.15, p>0.05). The greater expression of glomerular collagen-I mRNA (PAI-1-/- 3.76±1.05 vs. WT 1.24±0.30, p<0.05), despite less glomerulosclerosis suggests degradation or post-transcriptional modification of the collagen protein.
Conclusions: Our data suggest that the absence of PAI-1 protects podocytes by preserving podocyte number and differentiation markers after toxic injury which leads to improved outcomes of progressive kidney disease.
Category: Kidney (does not include tumors)
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 264, Wednesday Afternoon