Suspension "hypokinesia/hypodynamia" may decrease bone mass by stimulatingosteoclast production in ovariectomized mice

This study was conducted to examine, in detail, the histological changes in the femurs of suspended ovariectomized (OVX) mice to assess the role of me chanical stress on bone remodeling. Suspended-OVX, suspended-sham-ope, nons uspended-OVX, and nonsuspended-sham-operated mice underwent operations 8 we eks after birth. Immediately after operation, hypokinesia/hypodynamia was c reated by a suspension harness for one week. Five specimens in each group w ere sacrificed 9 weeks after birth. The trabecular bone of the femurs in th e suspended-OVX mice was removed and replaced extensively by bone marrow. T he number of tartrate-resistant acid phosphatase (TRAP)positive cells was l arger in the suspended-OVX mice than in the remaining three groups. No sign ificant differences in the number of TRAP positive cells were found between the suspended-sham-ope. nonsuspended-OVX and nonsuspended-sham-ope mice. T he femurs of the OVX mouse with suspension "hypokinesia/hypodynamia" thus e xhibits extensive trabecular bone loss in association with an increase of o steoclasts.