Effects of advanced glycation end-products, diabetes and metformin on the osteoblastic transdifferentiation capacity of vascular smooth muscle cells: In vivo and in vitro studies

Aims: Our objective was to study the vascular smooth muscle cells (VSMC) osteoblastic transdifferentiation in AGE exposed cells or those from diabetic animals, and its response to metformin treatment.Methods: VSMC were obtained from non-diabetic rats, grown with or without AGE; while VSMC of in vivo-ex vivo studies were obtained from non-diabetic control animals (C), diabetic (D), C treated with metformin (M) and D treated with metformin (D-M). We studied the osteoblastic differentiation by evaluating alkaline phosphatase (ALP), type I collagen (Col) and mineral deposit.Results: In vitro, AGE increased proliferation, migration, and osteoblastic differentiation of VSMC. Metformin cotreatment prevented the AGE induced proliferation and migration. Both AGE and metformin stimulated the expression of ALP and Col. AGE induced mineralization was prevented by metformin. VSMC from D expressed a higher production of Col and ALP. Those from D-M showed an ALP increase vs C and M, and a partial decrease vs D. Cultured in osteogenic medium, ALP, Col and mineralization increased in D vs C, remained unchanged in M, and were prevented in D-M animals.Conclusion: Both AGE and DM favor VSMC differentiation towards the osteogenic phenotype and this effect can be prevented by metformin.