PPARγ inhibition promotes osteogenic differentiation of bone marrow mesenchymal stem cells and fracture healing

This study aimed to explore the effects of peroxisome proliferator-activated receptor gamma (PPAR gamma) inhibition on fracture healing of nonunion and the underlying mechanisms. Bone marrow mesenchymal stem cells (BMSCs) were treated with PPAR gamma antagonist GW9662 (5 mu M, 10 mu M). Alkaline phosphatase (ALP) staining and Alizarin Red S was used to assess early stage of osteogenesis and osteogenic differentiation. GW9662 (1 mg/kg/day) were administered intraperitoneally into the rats with bone fracture. Bone healing processes in the rat femur fracture model were recorded and assessed by radiographic methods on Weeks 8, 14, and 20 postoperation. Osteogenesis and angiogenesis at the fracture sites were evaluated by radiographic and histological methods on postoperative Week 20. GW9662 treatment increased ALP activity and Alp mRNA expression in rat BMSCs. Moreover, GW9662 administration increased matrix mineralization and mRNA and protein levels of Bmp2 and Runx2 in the BMSCs. In addition, GW9662 treatment improved radiographic score in the fracture rats and increased osteogenesis-related proteins, including type I collagen, osteopontin, and osteoglycin, in the bone tissues of the fracture sites. In conclusion, PPAR gamma inhibition promotes osteogenic differentiation of rat BMSCs, as well as improves the fracture healing of rats through Bmp2/Runx2 signaling pathway in the rat model of bone fracture.