Wnt10b-overexpressing umbilical cord mesenchymal stem cells promote critical size rat calvarial defect healing by enhanced osteogenesis and VEGF-mediated angiogenesis

Background/objectives: Accelerating the process of bone regeneration is of great interest for surgeons and basic scientists alike. Recently, umbilical cord mesenchymal stem cells (UCMSCs) are considered clinically applicable for tissue regeneration due to their noninvasive harvesting and better viability. Nonetheless, the bone regenerative ability of human UCMSCs (HUCMSCs) is largely unknown. This study aimed to investigate whether Wnt10b-overexpressing HUCMSCs have enhanced bone regeneration ability in a rat model. Method: A rat calvarial defect was performed on 8-week old male Sprague Dawley rats. Commercially purchased HUCMSCsEmp in hydrogel, HUCMSCsWnt10b in hydrogel and HUCMSCsWnt10b with IWR-1 were placed in the calvarial bone defect right after surgery on rats (N = 8 rats for each group). Calvaria were harvested for micro-CT analysis and histology four weeks after surgery. CFU-F and multi-differentiation assay by oil red staining, alizarin red staining and RT-PCR (real-time polymerase chain reaction) were performed on HUCMSCsEmp and HUCMSCsWnt10b in vitro. Conditioned media from HUCMSCsEmp and HUCMSCsWnt10b were collected and used to treat human umbilical cord vein endothelial cells in Matrigel to access vessel formation capacity by tube formation assay. Results: Alizarin red staining, oil red staining and RT-PCR results showed robust osteogenic differentiation but poor adipogenic differentiation ability of HUCMSCsWnt10b. Furthermore, HUCMSCsWnt10b could accelerate bone defect healing, which was likely due to enhanced angiogenesis after the HUCMSCsWnt10b treatment, because more CD31thorn vessels and increased vascular endothelial growth factor-A (VEGF-A) expression were observed, compared with the HUCMSCsEmp treatment. Conditioned media from HUCMSCsWnt10b also induced endothelial cells to form vessel tubes in a tube formation assay, which could be abolished by SU5416, an angiogenesis inhibitor. Conclusion: To our knowledge, this is the first study providing empirical evidence that HUCMSCsWnt10b can enhance their ability to heal calvarial bone defects via VEGF-mediated angiogenesis. The translational potential of this article: HUCMSCsWnt10b can accelerate critical size calvaria and are a new promising therapeutic cell source for fracture nonunion healing.