Puerarin promotes the viability and differentiation of MC3T3-E1 cells by enhancing LC3B-mediated autophagy through downregulation of miR-204

Puerarin is a bioactive substance extracted from Pueraria lobata. It is known to promote the viability, differentiation and mineralization of osteoblasts. However, the molecular mechanisms involved in these activities are not well understood. The present study was conducted with the aim of elucidating the effect of puerarin on osteoblasts and to explore the underlying mechanism. CCK-8 analysis showed that puerarin (0.1, 1 and 10 µM) promoted the viability of osteoblastic MC3T3-E1 cells, with 1 µM of puerarin exhibiting the strongest effect. Moreover, 1 µM puerarin significantly increased the activity of alkaline phosphatase (ALP) and the formation of mineralized nodules in the MC3T3-E1 cells. Treatment with 1 µM puerarin for 72 h led to a significant upregulation in the expression level of microtubule-associated light chain 3 (LC3)B and Beclin1 proteins. This treatment was more effective in promoting LC3B expression than what was observed following treatment with rapamycin (overexpression for autophagy). The bilayer membrane structure of autophagosomes was observed by electron microscopy. Conversely, 3-methyladenine (3-MA, inhibitor of autophagy) reduced the cell viability as well as the activity of alkaline phosphatase (ALP) in MC3T3-E1 cells, although, there was no significant influence on mineralization. Prediction results of the biological information showed that LC3B could be a direct target of microRNA-204 (miR-204). In the present study, the expression level of miR-204 was decreased by puerarin. miR-204 mimics significantly decreased LC3B expression and inhibited auotophagosome formation, while the miR-204 inhibitor had the opposite effects. To conclude, the results of the present study suggest that puerarin promotes the viability and differentiation of MC3T3-E1 cells through autophagy, which is possibly associated with miR-204-regulated LC3B upregulation.