MiR-34a suppresses osteoblast differentiation through glycolysis inhibition by targeting lactate dehydrogenase-A (LDHA)

Bone formation (osteogenesis) is mediated through recruitment of bone marrow mesenchymal stem cells (MSCs) with capacity to differentiate into osteoblasts, a process which is regulated by transcriptional and post-transcriptional mechanisms. Multiple studies have suggested that miRNAs might have important roles in osteoblast differentiation. Expressions of miR-34a were detected by qRT-PCR. Cellular glucose metabolism was assessed by measurements of glucose uptake and lactate production. mRNA expressions of glycolysis enzymes were detected by qRT-PCR. Osteogenic differentiation of human MSCs (hMSCs) was analyzed by alkaline phosphatase (ALP) activity and Alizarin red staining. Here, we report that microRNA-34a is upregulated during the osteoblast differentiation from hMSCs. miR-34a overexpressing inhibited late osteoblast differentiation of hMSCs in vitro. The ALP activity and Alizarin red staining were significantly decreased by miR-34a in hMSCs. Target prediction analysis reveals that the lactate dehydrogenase-A (LDHA) is a potential target of miR-34a. We hypothesized that miR-34a inhibits osteoblast differentiation through targeting the LDHA-mediated cellular glycolysis. Results from Western blotting and luciferase assay validated that miR-34a could directly target 3 ' UTR of LDHA mRNA. In addition, we demonstrated that overexpression of miR-34a inhibits cellular anaerobic glycolysis through targeting LHDA. The protein and mRNA expressions of glycolysis enzymes, Hexokinase 2 (HK2), glucose transporter 1 (GLUT1), and LDHA were significantly downregulated by miR-34a overexpression in hMSCs. Furthermore, we showed that LDHA restoration in miR-34a overexpressing hMSCs successfully rescued the osteoblast differentiation of hMSCs. This study demonstrated the roles of miR-34a in regulating osteoblast differentiation, suggesting that miR-34a inhibition could be a new therapeutic strategy for improving bone formation.