The small molecule DIPQUO promotes osteogenic differentiation via inhibition of glycogen synthase kinase 3-beta signaling

Bone fractures are common impact injuries typically resolved through natural processes of osteogenic regeneration and bone remodeling, restoring the biological and mechanical function. However, dysfunctionality in bone healing and repair often arises in the context of aging-related chronic disorders, such as Alzheimer's disease (AD). There is unmet need for effective pharmacological modulators of osteogenic differentiation and an opportunity to probe the complex links between bone biology and cognitive disorders. We previously discovered the small molecule DIPQUO, which promotes osteoblast differentiation and bone mineralization in mouse and human cell culture models, and in zebrafish developmental and regenerative models. Here, we examined the detailed function of this molecule. First, we used kinase profiling, cellular thermal shift assays, and functional studies to identify glycogen synthase kinase 3-beta (GSK3-β) inhibition as a mechanism of DIPQUO action. Treatment of mouse C2C12 myoblasts with DIPQUO promoted alkaline phosphatase expression and activity, which could be enhanced synergistically by treatment with other GSK3-β inhibitors. Suppression of the expression or function of GSK3-β attenuated DIPQUO-dependent osteogenic differentiation. In addition, DIPQUO synergized with GSK3-β inhibitors to stimulate expression of osteoblast genes in human multipotent progenitors. Accordingly, DIPQUO promoted accumulation and activation of β-catenin. Moreover, DIPQUO suppressed activation of tau microtubule-associated protein, an AD-related effector of GSK3-β signaling. Therefore, DIPQUO has potential as both a lead candidate for bone therapeutic development and a pharmacological modulator of GSK3-β signaling in cell culture and animal models of disorders including AD.