Targeted inhibition of CTGF by RNA interference restrain renal fibrosis

Abstract

Objective To investigate the impact on renal fibrosis by inhibition of connective tissue growth factor( CTGF) by RNA interference in spontaneous hypertension rat( SHR) . Method Twenty SHR were randomly (random number) divided into SHR group ( n = 10) and RNAi group ( n = 10), eight Wistar-Kyoto rats were set as control. At the end of RNA interference procedure, all the rats were sacrificed and the kidneys were harvested. The mRNA and plasmosin of CTGF and fibronectin(FN) of renal tissue were extracted and measured by RT-PCR and Western Blotting. And the localization of CTGF and FN were analyzed with immunohistochernistry technique. The collagen deposition(shown as collagen volume traction, CVF) were evaluated with 0.1% sirius-picric staining, and the hydroxyproline of myocardium were detected by colorimetry. Results The mRNA and protein expression of CTGF decreased 66% and 62% in RNAi group (P < 0.01). The mRNA and protein expression of FN decreased 56% and 51% in RNAi group.The same inhibition effect was observed by hislological analysis. Immuno-histochemistry showed that CTGF localized both in renal parenchyma and renal interstitium, whereas FN majorly expressed in renal interstitium. Observation with light microscope showed that collagen deposition(CVF)decreased sharply in RNAi group versus SHR group. And the same effect was viewed in hydroxypnoline assay[SHR group: (0.596 ± 0.067) μg/mg, RNAi group: (0.368±0.084) μg/mg, P < 0.01 ] .Further study by polarized microscope displayed that RNA interference mainly suppressed type I collagen synthesis. Conclusions Targeted inhibition of CTGF by RNA interference leads significant decrease of extracellular matrix deposition in kidney. And the anti-fibrotic effect independent of lower the blood pressure. This study indicated CTGF take a key role in the development and progress of renal fibrosis. Key words: Connective tissue growth factor; Renal fibrosis; RNA interference; Extracellular matrix; Fi-bronectin; Collagen; Plasmid; Transfection