Hydrogel contained valproic acid accelerates bone-defect repair via activating Notch signaling pathway in ovariectomized rats

Zhou-Shan Tao,Hong-Guang Xu,Tian-Lin Li,Min Yang

doi:10.1007/s10856-021-06627-2

Abstract

The purpose was to observe whether valproic acid (VPA) has a positive effect on bone-defect repair via activating the Notch signaling pathway in an OVX rat model. The MC3T3-E1 cells were cocultured with VPA and induced to osteogenesis, and the osteogenic activity was observed by alkaline phosphatase (ALP) staining, Alizarin Red (RES) staining and Western blotting (WB). Then the hydrogel-containing VPA was implanted into the femoral epiphysis bone-defect model of ovariectomized (OVX) rats for 12 weeks. Micro-CT, biomechanical testing, histology, immunofluorescence, RT-qPCR, and WB analysis were used to observe the therapeutic effect and explore the possible mechanism. ALP and ARS staining and WB results show that the cell mineralization, osteogenic activity, and protein expression of ALP, OPN, RUNX-2, OC, Notch 1, HES1, HEY1, and JAG1 of VPA group is significantly higher than the control group. Micro-CT, biomechanical testing, histology, immunofluorescence, and RT-qPCR evaluation show that group VPA presented the stronger effect on bone strength, bone regeneration, bone mineralization, higher expression of VEGFA, BMP-2, ALP, OPN, RUNX-2, OC, Notch 1, HES1, HEY1, and JAG1 of VPA when compared with OVX group. Our current study demonstrated that local treatment with VPA could stimulate repair of femoral condyle defects, and these effects may be achieved by activating Notch signaling pathway and acceleration of blood vessel and bone formation.

Highlights

Osteoporosis is a health-concern metabolic bone skeletal disease characterized by increased bone loss and bonestructure deterioration, which will lead to reduced bone mineral density (BMD) and bone strength and increased risk of fragility fractures [1,2,3]
The osteogenic protein expressions including alkaline phosphatase (ALP), OPN, RUNX-2, and OC of valproic acid (VPA) group were significantly higher than that of the control group (P < 0.05). These results indicate that the treatment with VPA can significantly increase MC3T3-E1 cell function and related protein expression
At 12 weeks, the VPA group showed increased Notch 1, HES1, HEY1, and JAG1 than the OVX group (p < 0.05). These results indicate that the Notch pathway of VPA treatment is activated, and the expression of Notch 1, HES1, HEY1, and JAG1 is upregulated

Summary

Introduction

Osteoporosis is a health-concern metabolic bone skeletal disease characterized by increased bone loss and bonestructure deterioration, which will lead to reduced bone mineral density (BMD) and bone strength and increased risk of fragility fractures [1,2,3]. In the event of a bone fracture or defects, bone tissue has the unique regeneration ability to replace damaged tissue by constant remodeling with osteoclasts, osteoblasts, osteocytes, and bone-lining cells. When bone defect reaches a certain volume, it is difficult to complete bone-defect healing by its regeneration ability, especially combined with osteoporosis characterized by markedly impaired bone-repair ability [5, 6]. Over the last few decades, bone-substitute materials have received significant attention, and numerous bone biomaterials researches have been reported [7, 8]. While autologous bone graft is still considered to be the “Gold Standard” for bone-defect reconstruction, the complications such as extension of surgical time, increase of surgical sites, and infection chance and aggravation of patient pain may promote people to find and design new alternative drugs and biological materials [9]

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Methods

Conclusion