Purpose: MicroRNA-151b (miR-151b) showed altered expression in ovariectomized rat model of osteoporosis. This study established an ovariectomy-induced osteoporotic rat model to investigate the role of miR-151b in osteoblasts.
Methods: Eighteen female Sprague-Dawley (SD) rats were divided randomly into Sham and OVX group (n = 9). The transfections with different miRNAs and expression vectors were confirmed by RT-qPCR. The protein expression of Msx2 was detected by Western blots. The interaction between miR-151b and Msx2D was evaluated by RNA pull-down and dual luciferase reporter assay.
Results: The expression of miR-151b was significantly increased in femoral tissues of ovariectomy-induced osteoporotic rats. The expression of osteogenesis marker genes including RUNX2, ALP, OCN, OSX, and Msx2 were all significantly increased in osteogenic medium (OM) incubated primary osteoblasts and MC3T3-E1 cells. The interaction between miR-151b and Msx2 was confirmed by luciferase reporter assay and RNA pull-down. Moreover, overexpression of miR-151b significantly inhibited Msx2 in both MC3T3-E1 cells and primary osteoblasts, while miR-151b inhibitor had the opposite effect on the expression of Msx2. In addition, in primary osteoblasts and MC3T3-E1 cells, miR-151b overexpression, or Msx2 silence significantly decreased the expression of OSX, ALP, RUNX2, and OCN.
Conclusion: MiR-151b could inhibit osteoblast proliferation, differentiation, and mineralization via downregulating Msx2 in both MC3T3-E1 cells and primary osteoblasts. MiR-151b might serve as a novel therapeutic target for osteoporosis.
Abbreviations: miR-151b: microRNA-151b; miRNAs: microRNAs; Msx2: Msh homeobox 2; MAPK: mitogen-activated protein kinase; STAT: signal transducer and activator of transcription; SD: Sprague-Dawley; BMD: bone mineral density; qRT-PCR: quantitative reverse transcription PCR; MTT: methyl thiazolyl tetrazolium; OVX: ovariectomy; ALP: alkaline phosphatase.
Keywords: MSX2; Osteoporosis; miR-151b; osteoblast differentiation.