Heat shock protein 47 is up-regulated in conjunctival bleb scarring after filtration surgery in rats

Abstract

Heat shock protein 47 (HSP47), a collagen-specific molecular chaperone, is involved in the biosynthesis and secretion of procollagen. Recent studies have shown a close association between increased HSP47 and excessive accumulation of collagens in various fibrotic diseases. This study was conducted to evaluate whether HSP47 plays a role in conjunctival bleb scarring after filtration surgery in rats. Trabeculectomy of the right eye was performed in Sprague-Dawley (SD) rats. Eight rats were euthanized at 2, 5, 8 and 11 days after surgery. Four rats were used to extract mRNA and the other four were used to extract protein. Blebs and normal control conjunctival tissues were collected. Real-time PCR (RT-PCR) and Western blot methods were used to evaluate alterations in HSP47 levels and type I and type III collagen. Bleb formation was observed in all eyes. Both the expression of HSP47 mRNA and protein in conjunctival blebs increased at 2, 5, 8 and 11 days postoperatively compared with that in normal control conjunctival tissues. The differences of both the mean mRNA and protein levels of HSP47 in blebs at each time point and in the normal control conjunctiva were statistically significant (mRNA level: F = 175.811, p < 0.001; protein level: F = 68.356, p < 0.001). Type I and type III collagen levels in blebs were raised at different time points both at mRNA and at protein levels. The differences between mean mRNA and protein levels of both type I and type III collagen in blebs at 2, 5, 8 and 11 days after surgery and in the normal control conjunctiva were statistically significant (mRNA level: FI = 182.210, p I < 0.001; FIII = 125.490, p III < 0.001; protein level: FI = 160.092, p I < 0.001; FIII = 62.374, p III < 0.001 ). The amount of HSP47 in bleb positively correlated with that of both type I and type III collagens (mRNA level: rsI = 0.688, p I = 0.003; rsIII = 0.900, p III < 0.001; protein level: rsI = 0.688, p I = 0.003; rsIII = 0.832, p III < 0.001). HSP47 is likely to be involved in the pathogenesis of conjunctival bleb scarring and may play a role in the process of conjunctival bleb fibrosis.