Role of Connective Tissue Growth Factor and Angiotensin II in Tubulointerstitial Fibrosis in Experimental Obstructive Nephropathy

Angiotensin II (Ang-II) and connective tissue growth factor (CTGF) are involved in various renal disorders that lead to end-stage renal disease. Here, we determined the role of Ang-II and CTGF in the progression of tubulointerstitial injury in the rat unilateral ureteral obstruction (UUO) model. Sprague-Dawley rats (n=16) were used; 10 rats underwent UUO, and 6 control rats underwent sham operation; and rats of both groups were sacrificed on days 7 or 14. Histomorphometric analysis was performed to quantitate tubulointerstitial injuries in the experimental group. Kidney sections were stained immunohistochemically for Ang-II, CTGF, transforming growth factor-β1 (TGF-β1), type III collagen and α-smooth muscle actin (α-SMA). Renal CTGF expression was studied using in situ hybridization and reverse transcriptase-polymerase chain reaction. Double staining for Ang-II with α-SMA and CTGF with α-SMA was performed to identify cells with enhanced expression of Ang-II and CTGF. Similar dual staining of Ang-II with type III collagen and CTGF with type III collagen was performed. The correlation between Ang-II and CTGF expression and tubulointerstitial injury was examined. In obstructed kidneys, there was a significant (p<0.001) increase in expression of Ang-II, CTGF, TGF-β1, type III collagen and α-SMA, compared with control kidneys. Tubular epithelial cells and interstitial cells were the main Ang-II- and CTGF-producing cells in the obstructed kidneys. A significantly (p<0.001) positive correlation was detected in obstructed kidneys between renal expression of CTGF and expression of TGF-β1 (r=0.91), type III collagen (r=0.87) or α-SMA (r=0.90). Similarly a significantly (p<0.001) positive correlation was found in obstructed kidneys between Ang-II expression and expression of TGF-β1 (r=0.88), type III collagen (r=0.79) and α-SMA (r=0.91). Finally, there were significantly positive correlations between CTGF /Ang-II expression and tubulointerstitial fibrosis in the obstructed kidneys (r=0.88, p<0.001). The results of our in vivo studies suggest that both Ang-II and CTGF, produced by intrarenal cells, coordinately regulate progression of renal tubulointerstitial injury, by facilitating increased accumulation of interstitial collagens in obstructed kidneys

Role of Connective Tissue Growth Factor and Angiotensin II in Tubulointerstitial Fibrosis in Experimental Obstructive Nephropathy

Angiotensin II (Ang-II) and connective tissue growth factor (CTGF) are involved in various renal disorders that lead to end-stage renal disease. Here, we determined the role of Ang-II and CTGF in the progression of tubulointerstitial injury in the rat unilateral ureteral obstruction (UUO) model. Sprague-Dawley rats (n=16) were used; 10 rats underwent UUO, and 6 control rats underwent sham operation; and rats of both groups were sacrificed on days 7 or 14. Histomorphometric analysis was performed to quantitate tubulointerstitial injuries in the experimental group. Kidney sections were stained immunohistochemically for Ang-II, CTGF, transforming growth factor-β1 (TGF-β1), type III collagen and α-smooth muscle actin (α-SMA). Renal CTGF expression was studied using in situ hybridization and reverse transcriptase-polymerase chain reaction. Double staining for Ang-II with α-SMA and CTGF with α-SMA was performed to identify cells with enhanced expression of Ang-II and CTGF. Similar dual staining of Ang-II with type III collagen and CTGF with type III collagen was performed. The correlation between Ang-II and CTGF expression and tubulointerstitial injury was examined. In obstructed kidneys, there was a significant (p<0.001) increase in expression of Ang-II, CTGF, TGF-β1, type III collagen and α-SMA, compared with control kidneys. Tubular epithelial cells and interstitial cells were the main Ang-II- and CTGF-producing cells in the obstructed kidneys. A significantly (p<0.001) positive correlation was detected in obstructed kidneys between renal expression of CTGF and expression of TGF-β1 (r=0.91), type III collagen (r=0.87) or α-SMA (r=0.90). Similarly a significantly (p<0.001) positive correlation was found in obstructed kidneys between Ang-II expression and expression of TGF-β1 (r=0.88), type III collagen (r=0.79) and α-SMA (r=0.91). Finally, there were significantly positive correlations between CTGF /Ang-II expression and tubulointerstitial fibrosis in the obstructed kidneys (r=0.88, p<0.001). The results of our in vivo studies suggest that both Ang-II and CTGF, produced by intrarenal cells, coordinately regulate progression of renal tubulointerstitial injury, by facilitating increased accumulation of interstitial collagens in obstructed kidneys