Changes of MicroRNA Profile in Ovariectomy-Induced Bone Loss

Abstract

MicroRNAs (miRNAs) have emerged as important regulators in various developmental, physiological, and pathological condition, and growing evidence shows the possibility of role of miRNAs in regulating bone mass. We investigated the change of miRNAs and mRNA expression profiles in bone tissue in ovariectomized mice model, and evaluated regulatory mechanism of bone mass mediated by miRNAs in estrogen deficiency state. Eight-week old female C3H/HeJ mice were underwent ovariectomy (OVX) or sham operation (Sham-op), and their femur and tibia were harvested to extract total bone RNAs after 4 weeks for microarray analysis. Eight miRNAs (miR-127, -133a, -133a*, -133b, -136 -206, -378, -378*) were identified to be upregulated after OVX while one miRNA (miR-204) was downregulated. Concomitant analysis of mRNA microarray revealed that about 658 genes were differentially expressed between OVX and Sham-op mice. Target prediction of differentially expressed miRNAs using Target scan and PicTar software identified potential targets and integrative analysis based on the results from the concomitant mRNA microarray, we found that PPARγ and CREB pathways are activated in skeletal tissues after ovariectomy. Among the potential candidates of miRNA, we further studied the role of miR-127 in vitro, which exhibited the greatest changes after OVX. When C3H10T1/2 cells were transfected with miR-127 inhibitors, alkaline phosphatase activities and mRNA expression of osteoblast-specific genes, Col type 1, ALP, Runx2, and osteocalcin were significantly increased. Furthermore, transfection of miR-127 inhibitors enhanced the osteocyte-like morphological changes of MLO-Y4 cells and their survival in apoptosis assay, however, significantly inhibited osteoclastic differentiation of bone marrow macrophage. Taken together, these results suggest novel insight in the association between distinct miRNAs in bone cell metabolism and their possible role through regulatory network with mRNAs in the pathogenesis of estrogen deficiency induced osteoporosis.