Suppression of Renal Tubulointerstitial Fibrosis by Small Interfering RNA Targeting Heat Shock Protein 47

Abstract

Background/Aim: Unilateral ureteral obstruction (UUO) is a well-established model for tubulointerstitial fibrosis. During the progression of tubulointerstitial fibrosis, upregulation of collagen synthesis and subsequent accumulation of collagen were observed in the tubulointerstitial area. Heat shock protein 47 (HSP47) is a collagen-specific molecular chaperone and plays an essential role in regulating collagen synthesis. We designed small interfering RNA (siRNA) sequences for HSP47 mRNA to examine whether HSP47 is involved in the progression of renal tubulointerstitial fibrosis in a mouse UUO model. Methods: The HSP47 siRNA was injected once via the ureter at the time of UUO preparation. We also applied a new gene delivery system for siRNA using cationized gelatin microspheres. The kidneys were harvested 7 and 14 days after UUO. The HSP47 and type I, III, and IV collagen expression levels were analyzed by immunohistochemistry and Western blotting. Results: Seven days after UUO, the expression levels of HSP47 and type I, III, and IV collagens were markedly upregulated in obstructed kidneys or green fluorescent protein siRNA treated obstructed kidneys. HSP47 siRNA injection significantly reduced the protein expression levels and significantly diminished the accompanying interstitial fibrosis. Moreover, cationized gelatin microspheres as a delivery system enhanced and lengthened the antifibrotic effect of HSP47 siRNA. Conclusions: Our results indicate that HSP47 is a candidate target for the prevention of tubulointerstitial fibrosis and that selective blockade of the HSP47 expression by using siRNA could be a potentially useful therapeutic approach for patients with renal disease.