Changes of type H vessel in bone from osteoporotic mice induced ovariectomy / 中华骨科杂志

ABSTRACT

Objective:To explore the changes of bone mineral density (BMD) and type H vessel, which was recently identified as strongly positive for CD31 and Endomucin (CD31 hiEmcn hi) in long bone from ovariectomized (OVX) mice compared withSham group. Methods:C57BL/6Jwild-type mice were used for experiments and bone tissuewas collected. Eight-week-old female mice were randomly divided into bilateral ovariectomy (OVX) and a sham operation (Sham). The bilateral ovaries were exposed and removed in the OVX group. In the sham group, the ovaries were only exposed but left intact. After 4weeks, these mice were killed for experiment and the femurs were collected for Micro CT scanning in order to observe the changes of bone mineral density (BMD) and trabecular indexes, including bone volume (BV), total volume of interest (TV), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N). The fresh tibia of each mouse was fixed, decalcified, dehydrated and embedded for immunostaining. All experimental data were analyzed with t-test. Results:Mouse femora from two groups were dissected at 4 week time points, and the attached soft tissue was completely removed for Micro CT scanning. BMD in OVX is 0.11±0.01 g/cm 3 and 0.21±0.01 g/cm 3 in Sham, which indicated the BMD in OVX significantly decreased. The results showed significant difference between the groups ( P=0.001). The microarchitecture in trabecular bone changed. BV/TV in OVX is 11.52%±1.77% and 25.87%±1.31% in Sham, which indicated the BV/TV in OVX significantly decreased. The results showed significant difference between the groups ( P<0.05). Tb.N in OVX is 1.67±0.33/mm and 2.95±0.82/mm in Sham, which indicated the Tb.N in OVX slightly decreased. The results showed no significant difference between the groups ( P=0.066). Tb.Th in OVX is 0.06±0.01 mm and 0.07±0.01 mm in Sham, which indicated the Tb.Th in OVX significantly thinned. The results showed significant difference between the groups ( P=0.021). Tb.Sp in OVX is 0.29±0.15 mm and 0.19±0.01 mm in Sham, which indicated the Tb.Sp in OVX significantly increased. The results showed significant difference between the groups ( P<0.05). In the groups BMD decreased and trabecular microstructure was broken. Both BMD and trabecular indexes (BV/TV, Tb. Th, Tb. Sp) showed significant changes in OVX group compared with Sham ( P<0.05) except Tb.N. We next examined the expression of CD31 and EMCN via immunostaining in order to observe the changes of type H vessel.By immunostaining, the percentage of HV/TV in OVX group was 9.14%±0.99% and 29.33%±1.22% in the sham-operated mice. Dramatically decreased type H vessels in the metaphysis of OVX mice were observed compared with that of Sham control mice. The results showed significant difference between the groups ( P<0.05). Conclusion:In this study, ovariectomized mice, a widely used model for postmenopausal osteoporosis, exhibited significantly reduced type H vessels accompanied by reduced BMD, which indicatedtype H vessel involved in the occurrence of postmenopausal osteoporosis.