Expression of connective tissue growth factor in renal tubulointerstitial fibrosis in rats and its pathogenic role

Abstract

In order to explore the role of connective tissue growth factor (CTGF) in the pathogenesis of renal tubulointerstitial fibrosis, 48 Wistar rats were randomly divided into sham-operated and unilateral ureteral obstruction (UUO) group. On the postoperative day 1, 3, 7 and 14, the rats were killed and the kidneys were removed. The renal tubulointerstitial injury index was evaluated according to the MASSON staining. The mRNA levels of CTGF, transforming growth factor-β1 (TGF-β1), collagen I (col I), and plasminogen activator inhibitor-1 (PAI-1) were detected using reverse transcriptional-polymerase chain reaction (RT-PCR). Immunohistochemistry was performed to evaluate the protein expression of the above factors, and the relations among them were analyzed. Quantitative expression of CTGF protein in the kidneys was also assessed using Western blot. The results showed that TGF-β1 mRNA level was increased at first day after UUO, followed by a marked elevation of CTGF mRNA level, which began to increase 3 days after UUO (P<0.01). With the progression of the disease, the mRNA expression of CTGF, col I and PAI-1 was increased progressively. Immunohistochemistry revealed that the CTGF protein expression was significantly increased in fibrotic areas and tubular epithelial cells 3 days after UUO. On the post-UUO day 7, the protein level of CTGF was positively related to the renal tubulointerstitial injury index (r=0.62,P<0.01), the expression of TGF-β1 (r=0.85,P<0.01), col I (r=0.78,P<0.01), and PAI-1 (r=0.76,P<0.01). Upon Western blot analysis, CTGF protein expression began to increase 3 days after UUO, and appeared progressively throughout the time course (P<0.01, as compared with sham-operated group). It is concluded that CTGF can be induced by TGF-β and mediate various profibrotic actions of this cytokine, such as increasing extracellular matrix (ECM) synthesis and decreasing ECM degradation. The increased expression of CTGF may play a crucial role in the development and progression of tubulointerstitial fibrosis.

Keywords

connective tissue growth factor / transforming growth factor-β1 / collagen I / plasminogen activator inhibitor-1 / renal tubulointerstitial fibrosis

References

[1] EddyA A. Molecular basis of renal fibrosis. Pediatric Nephrology, 2000, 15: 290-290

[2] ItoY, AtenJ, BendeR J, et al. . Expression of connective tissue growth factor in human renal fibrosis. Kidney Int, 1998, 53: 853-853

[3] GrotendorstG R, OkochiH, HayashiN. A novel transforming growth factor β response element controls the expression of connective tissue growth factor gene. Cell Growth Differ, 1996, 7: 469-469

[4] RadfordM G, DonadioJ V, BergstralhE J, et al. . Predicting renal outcome in IgA nephropathy. J Am Soc Nephrol, 1997, 8: 199-199

[5] KlahrS, MorrisseyJ. Obstructive nephropathy and renal fibrosis. Am J Physiol Renal Physiol, 2002, 283: F861-F861

[6] CoppoR, AmoreA. New perspectives in treatment of glomerulonephritis. Pediatr Nephrol, 2004, 19: 256-256

[7] WangS, HirschbergR. BMP7 antagonizes TGF-beta-dependent fibrogenesis in mesangial cells. Am J Physiol Renal Physiol, 2003, 284: F1006-F1006

[8] ZhangC, MengX F, ZhuZ H, et al. . Connective tissue growth factor regulates the key events in tubular epithelial to myofibroblast transitionin vitro. Cell Biol Int, 2004, 28: 863-863

[9] ZhangC, MengX F, ZhuZ H, et al. . Role of connective tissue growth factor in renal tubularepithelial-myofibroblast transdifferentiation and extracellular matrix accumulationin vitro. Life Sci, 2004, 75: 367-367

[10] YokoiH, MukoyamaM, SugawaraA, et al. . Role of connective tissue growth factor in fibronectin expression and tubulointerstitial fibrosis. Am J Physiol Renal Physiol, 2002, 282: F933-F933

[11] BalidC, VincentM, FouqueD, et al. . Myofibroblast: a prognostic marker and target cell in progressive renal disease. Ren Fail, 2001, 23: 543-543

[12] BaricosW H, CortezS L, el-DahrS S, et al. . ECM degradation by cultured human mesangial cells is mediated by a PA/plasmin/MMP-2 cascade. Kidney Int, 1995, 47: 1039-1039