Objective      To determine the effect of miR-181a on the proliferation of mouse bone mesenchymal stem cells (MSCs) derived from mouse model of osteoporosis (OP).       Methods      Animal model of OP was established by bilateral ovariectomy (OVX) in 20 8-week-old healthy female C57BL/6 mice

and the mice undergoing sham operation served as control. In 2 months later

micro-CT scanning was employed to detect the parameters of trabecular microstructure and the indicators of the bone mineral density of both groups. The mice were then sacrificed to isolate MSCs

which were then identified by flow cytometry for their phenotypes and by Alizarin red staining and Oil red 0 staining for osteogenic and adipogenic capacities. MTT assay was used to measure the proliferation capacity of the MSCs derived from 2 groups of mice. The mRNA expression of miR-181a was measured by RT-PCR. The proliferation of MSCs after up-regulating/down-regulating the expression of miR-181a was detected by MTT assay.       Results      The results of micro-CT scanning showed significant differences in the parameters of trabecular microstructure and the indicators of the bone mineral density between 2 groups (P＜0.05). The proliferation capacity of MSCs was declined

and the expression of miR-181a was significantly increased in the cells from OVX group (P＜0.05). Up-regulation/down-regulation of miR-181a resulted in significantly decreased/increased proliferation in MSCs. And the adipogenic capacity of MSCs was stronger in OVX group than in sham group

whereas the osteogenic capacity was weaker (P＜0.05). MTT assay showed the proliferation capacity was better in the MSCs from sham operation group than from OVX group (P＜0.05).       Conclusion      In the process of osteoporosis induced by estrogen deficiency

the high expression of miR-181a inhibits the proliferation of MSCs

which may play an important role in the pathogenesis of postmenopausal osteoporosis.