Effect of effective fraction of Radix Salviae Miltiorrhizae on procollagen gene expression in fracture healing

OBJECTIVE: To investigate effect of effective fraction of Radix Salviae Miltiorrhizae (RS9403) on procollagens and transforming growth factor beta 1(TGF beta 1) gene expression in fracture callus, and to explore the mechanism of RS9403 in enhancing fracture healing. METHODS: Standardized radial fractures were performed in 24 Wistar rats, which were randomized into three groups: the RS9403 group, the Sanhua Jiegu powder (SHJGP) group and the blank control model group. They were fed orally with RS9403, SHJGP and normal saline respectively, and were sacrificed on the 3rd day, 1st week, 2nd week and 4th week after fracture in batches. In situ localization of procollagens and TGF beta 1 gene expression were examined on the cryosection of rat fracture callus. RESULTS: On the 3rd day after fracture, the TGF beta 1 gene expression at the site of fracture in the RS9403 group and the SHJGP group was significantly higher than that in the blank control group, and type-III procollagen gene expression was observed in the two groups. At the end of 1st week after fracture, the pro alpha 1(III) expression in fibroblast and chondrocyte-like cells was dominant. The local type II and I procollagen gene expressions in the RS9403 and the SHJGP group were enhanced simultaneously with TGF beta 1 gene expression compared with those in the blank control group. At the end of 2nd week the RS9403 and the SHJGP group were characterized by a marked increase in the mRNA levels of type I procollagen, the numbers of hypertrophic chondrocytes was larger than that in the control group, and the type II procollagen expression declined markedly. The shared phenotype expression was confirmed at this stage, especially in the RS9403 and the SHJGP group. At the end of 4th week, the cartilagi nous callus was almost all replaced by the bone tissue. In the RS9403 and the SHJGP group, the replacement was nearly complete, few type I procollagen mRNA positive osteoblasts and hypertrophic chondrocytes were found scattering in the woven bone and remnants of cartilaginous callus. CONCLUSION: RS9403 could affect the procollagens expression to enhance the healing of bone fracture as SHJGP do, maybe, by modulating the TGF beta 1 expression.