Inducible expression of Wnt7b promotes bone formation in aged mice and enhances fracture healing

There remain unmet clinical needs for safe and effective bone anabolic therapies to treat aging-related osteoporosis and to improve fracture healing in cases of nonunion or delayed union. Wnt signaling has emerged as a promising target pathway for developing novel bone anabolic drugs. Although neutralizing antibodies against the Wnt antagonist sclerostin have been tested,Wnt ligands themselves have not been fully explored as a potential therapy. Previous work has demonstrated Wnt7b as an endogenous ligand upregulated during osteoblast differentiation, and that Wnt7b overexpression potently stimulates bone accrual in the mouse. The earlier studies however did not address whether Wnt7b could promote bone formation when specifically applied to aged or fractured bones. Here we have developed a doxycycline-inducible strategy where Wnt7b is temporally induced in the bones of aged mice or during fracture healing. We report that forced expression of Wnt7b for 1 month starting at 15 months of age greatly stimulated trabecular and endosteal bone formation, resulting in a marked increase in bone mass. We further tested the effect of Wnt7b on bone healing in a murine closed femur fracture model. Induced expression of Wnt7b at the onset of fracture did not affect the initial cartilage formation but promoted mineralization of the subsequent bone callus. Thus, targeted delivery of Wnt7b to aged bones or fracture sites may be explored as a potential therapy.

Chondroitin Polymerizing Factor (CHPF) promotes cell proliferation and tumor growth in human osteosarcoma by inhibiting SKP2's ubiquitination while activating the AKT pathway

Osteosarcoma is a common malignant tumor occurring in children and young adults. Chondroitin sulfate (CS) participates in cell adhesion, cell division, and the formation of neural networks in the body, the biosynthesis of which requires the participation of glycosyltransferases. CHPF, a glycosyltransferase, plays a role in the extension of CS. Recently, CHPF's biological roles and functional importance in human diseases including malignant tumors have been widely discussed. However, whether CHPF is involved in osteosarcoma development and growth has not been revealed. The present work aimed to investigate the expression levels, functional significance and molecular mechanism of CHPF in osteosarcoma progression. Our results revealed that CHPF is strongly expressed in osteosarcoma tissues and cells. Furthermore, CHPF serves as a tumor promoter in the development and progression of osteosarcoma through enhancing cell proliferation and migration while suppressing apoptosis. Exploration of the mechanism by which CHPF promotes osteosarcoma indicated that CHPF promotes osteosarcoma through counteracting SKP2's ubiquitination and activating the Akt signaling pathway. For the first time, we clarified the roles of CHPF in osteosarcoma, and our results suggested that CHPF might be a novel therapeutic target in the treatment strategies for osteosarcoma.