1. Institute of Orthopaedics and Traumatology, the First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang Province, China
2. First Clinical College of Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang Province, China
3. Department of Orthopaedics and Traumatology, Wangjiang Sub-District Community Health Service Centre, Hangzhou 310016, Zhejiang Province, China
4. Department of Orthopaedic Surgery, the First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou 310006, Zhejiang Province, China
5. Department of Traumatology, Beijing Jishuitan Hospital, 100035, Beijing, China
6. Department of Biochemistry, Rush University Medical Center, Chicago, IL 60612, USA
# These authors contributed equally to this work.
Osthole is a bioactive coumarin derivative and has been reported to be able to enhance bone formation and improve fracture healing. However, the molecular mechanism of Osthole in bone fracture healing has not been fully defined. In this study we determined if Osthole enhances bone fracture healing through activation of BMP2 signaling in mice. We performed unilateral open transverse tibial fracture procedure in 10-week-old C57BL/6 mice which were treated with or without Osthole. Our previous studies demonstrated that chondrocyte BMP signaling is required for bone fracture healing, in this study we also performed tibial fracture procedure in Cre-negative and Col2-Cre;Bmp2flox/flox conditional knockout (KO) mice (Bmp2Col2Cre) to determine if Osthole enhances fracture healing in a BMP2-dependent manner. Fracture callus tissues were collected and analyzed by X-ray, micro-CT (μCT), histology, histomorphometry, immunohistochemistry (IHC), biomechanical testing and quantitative gene expression analysis. In addition, mouse chondrogenic ATDC5 cells were cultured with or without Osthole and the expression levels of chondrogenic marker genes were examined. The results demonstrated that Osthole promotes bone fracture healing in wild-type (WT) or Cre- control mice. In contrast, Osthole failed to promote bone fracture healing in Bmp2Col2Cre conditional KO mice. In the mice receiving Osthole treatment, expression of cartilage marker genes was significantly increased. We conclude that Osthole could promote bone strength and enhance fracture healing by activation of BMP2 signaling. Osthole may be used as an alternative approach in the orthopaedic clinic for the treatment of fracture healing.
Keywords: Osthole, Fracture healing, BMP Signaling, Chondrocyte, Endochondral bone formation