Effects of human umbilical cord mesenchymal stem cells-derived exosomes on fracture healing in rats through the Wnt signaling pathway.

OBJECTIVE: To investigate the role of human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes in the Wnt signaling pathway and their effects on fracture healing in rats. MATERIALS AND METHODS: A total of 24 healthy male Sprague-Dawley (SD) rats were randomly divided into 3 groups, of which the experimental groups were injected with Phosphate-Buffered Saline (PBS) and hUCMSC-derived exosomes, respectively, at the fracture site, and a blank control group was set. At 2 and 3 w after treatment, respectively, the healing condition at the fracture site in the rats was detected by micro-computed tomography (CT). The protein expressions of ß-catenin and Wnt3a of the Wnt signaling pathway in the bone tissue were measured via Western blotting (WB) assay. Quantitative Real Time-fluorescence Polymerase Chain Reaction (qRT-PCR) was performed to determine the expressions of osteogenic marker genes [collagen type I (COL-1), osteopontin (OPN) and runt-related transcription factor 2 (RUNX2)]. RESULTS: The results of the micro-CT scan showed that the rats treated with exosomes had better apposition of the fracture site, and the appearance of cortical bone was continuous. The fracture sites in the blank control group and PBS injection group were not healed, and the appearance of cortical bone was discontinuous, with significant fracture lines. According to the WB results, the protein expression levels of ß-catenin and Wnt3a in exosome treatment group were significantly higher than those in the blank control group and PBS injection group (p<0.01). The qRT-PCR results indicated that the expression levels of COL-1, OPN and RUNX2 in exosome treatment group were increased evidently compared with those in the other two groups (p<0.01). CONCLUSIONS: HucMSC-derived exosomes are probably involved in the repair of fracture in rats through the Wnt signaling pathway.