Metformin Promotes Osteogenic Differentiation of Adipose-Derived Stem Cells in Diabetic Osteoporosis by Regulating Autophagy

Patients with diabetic osteoporosis (DOP) face significant challenges in bone defect repair and regeneration. Adipose-derived stem cells (ASCs) have been widely used in bone tissue engineering due to their accessibility and multi-potency. However, DOP-ASCs exhibit lower capacity for osteogenic differentiation compared to control ASCs (CON-ASCs). In this study, we explored the effects of metformin (Met) on the autophagy and osteogenic capacity of DOP-ASCs. DOP mouse model was established with a high-fat and high-glucose diet combined with streptozotocin injection. After treating DOP-ASCs with Met and 3-methyladenine (3-MA), changes in autophagy levels and osteogenic differentiation capacity were observed by western blot analysis, real-time quantitative PCR (qPCR), immunofluorescence, alkaline phosphatase staining, alizarin red staining, and GFP-LC3 fluorescence labeling analysis. DOP-ASCs were cocultured with the Biphasic Calcium Phosphate (BCP), and implanted into the cranial defect area of DOP mice. The mice then received oral Met and intraperitoneal 3-MA injections for 3 months. The implanted BCP was assessed by micro-CT, HE and Masson staining. We observed a significantly reduced autophagic levels and capacity for osteogenic differentiation in DOP-ASCs, as compared to CON-ASCs. Met activated autophagy in DOP-ASCs and improved their osteogenic differentiation capacity. However, in the DOP + Met + 3MA group, both the autophagic level and the osteogenic differentiation capacity were suppressed. The results from the in vitro research and the in vivo outcomes agreed. Moreover, Met dramatically reduced p-PI3K and p-AKT expression. Met improves the osteogenic differentiation capacity by activating autophagy, an effect mediated through the PI3K/AKT signaling pathway.