Validation of downregulated microRNAs during osteoclast formation and osteoporosis progression.

Enhanced osteoclast formation and function have essential roles during post‑menopausal osteoporosis. A number of cytokines have been reported to regulate osteoclastogenesis and to be involved during the pathogenesis of osteoporosis. However, the regulation of osteolysis by microRNAs (miRNAs) has remained to be fully elucidated. The present study used a microarray analysis to identify a variety of miRNAs that are differentially expressed during osteoclast formation. Six down‑regulated miRNAs, miR‑21a‑5p, miR‑27a‑3p, let‑7i‑5p, miR‑22‑3p, miR‑340‑5p and miR‑23a‑5p, whose molecular mechanisms during osteoclast differentiation have not been reported previously, were further assessed. Using an osteoclast formation assay and a mouse model of progressive osteoporosis, the downregulation of these miRNAs was validated in vitro and in vivo. Of note, the expression patterns of these six miRNAs were associated with the progression of osteoporosis. Therefore, these miRNAs are of potential diagnostic and therapeutic value for osteolytic diseases.