Inhibition of miR-22 promotes differentiation of osteoblasts and improves bone formation via the YWHAZ pathway in...

In senile osteoporosis countering the age-mediated bone loss, promotion of osteoblastogenesis and identification of responsible micro-RNA (miR) would be a successful strategy.

miR microarray screening was carried out to identify the suppressed miRs after real time polymerase chain reaction (RT-PCR) analysis in mesenchymal stem cells (MSCs) derived from adult bone marrow during the proliferation to the mineralization stage. The primary calvarial pre-osteoblasts (human) were harvested and received transfection of miR-22's antagomir or agomir in vitro. Bioinformatics study suggested YWHAZ as the favorable target gene. Next, YWHAZ knockdown was studied for its effect on differentiation of osteoblasts. For in vivo studies, ovariectomized or sham mice were injected with miR-22's antagomir for a period of 6 weeks. The stromal cells were isolated in the 6^th week for ex vivo experiments.

miR-22 was found to be down-regulated in bone marrow derived mesenchymal stem cells. miR-22's antagomir converted the pre-osteoblasts to a more differentiated and mineralized phenotype showing upregulated protein expression of COL1A1, ALP and CBFA1. The miR-22's antagomir suppressed YWHAZ, enhanced stability of CBFA1 and promoted the differentiation of osteoblasts. In vivo, miR-22's antagomir promoted mineralization and osteoblastogenesis, elevated bone strength and reversed the ovariectomy mediated bone loss in sham mice.

Inhibition of miR-22 may be a potential target for treating osteoporosis clinically. The findings hence suggest that inhibition of miR-22 may be an effective anabolic therapeutic approach in treating osteoporosis clinically.