Kefir peptides promote osteogenic differentiation to enhance bone fracture healing in rats

Aims: Fractures are the result of fragile bone structures after trauma caused by direct or indirect external impact or strong muscular contraction. Most fracture patients undergo surgical fixation to accelerate the healing process and restore the function of mutilated bone. Promoting the healing process remains an important issue for the treatment of bone fractures. Our previous studies demonstrated the remarkable bone-protective effects of kefir peptides (KPs) in ovariectomized rats and mice. In this study, we further evaluate the efficacy of KPs on fracture healing using a rat model of femoral fracture.Main methods: Fifteen 8-week-old male Sprague Dawley (SD) rats were divided into the sham, mock, and KPs groups, in which the mock and the KPs groups underwent femur-fracture surgery with nail fixation, while the sham group underwent a sham operation. The next day, rats were orally administered with daily 400 mg/kg of KPs (KPs group) or distilled water (sham and mock groups) for four weeks. X-ray imaging, histochemical staining and serum osteogenic markers were applied for fracture healing evaluation. In vitro, mouse bone marrow mesenchymal stem cells (BMMSCs) and MC3T3-E1 line were subjected to osteoblast differentiation in the presence of KPs and compared with no KPs treatment.Key findings: The results demonstrated that KPs treatment improved the progression of the fracture healing process (p < 0.05) and significantly increased the expressions of Col1a1, Alp, Spp1, Vegfa and Cox2 mRNA in the femurs of the KPs-treated fractured rats compared to those of the mock-treated fracture rats. In vitro, KPs treatment promoted bone regeneration factor (Col1a1, Alp, M-csf and Phospho1) expression in MC3T3-E1-derived osteoblast cultures (on Day 3) and enhanced osteogenic differentiation and mineralization in BMMSC-derived osteoblast cultures (on Day 17 and Day 21). Significance: This is the first study to show that KPs can help with fracture healing by promoting osteogenic differentiation, and it also suggests that KPs can be used as a nutritional supplement to accelerate fracture healing.