Alterations of ovariectomized rat bone and impact of non-collagenous proteins on mineralization

Noncollagenous proteins (NCPs) play distinct and overlap roles in controlling the mineralization of bone, while the relationship between the NCPs and the mineral phase in osteoporotic bone is nebulous. Ovariectomized (OVX) rats, as an animal model for osteopenia, were used in this study to evaluate the impact of NCPs on mineral metabolism in osteopenia development.

Bone mineral was characterized with small-angle X-ray scattering study, extended X-ray absorption fine structure analysis, inductively coupled plasma mass spectroscopy, thermogravimetric and chemical analyses. NCPs were extracted from bone matrix, and analyzed with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). A constant composition titration system was used in the kinetic study of re-mineralization of bone residues after various extractions.

Bone density was reduced, whereas no significant changes were observed in the composition, crystal thickness and crystal structural parameters of minerals from OVX rat bone. The total content of NCPs in each extract decreased in the OVX group, but no selective loss of particular proteins was observed. The difference in mineralization kinetics between the OVX rat bone and the sham rat bone was resulted mainly from the mineral-bound NCPs.

The reduced quantity and unchanged quality of bone mineral seem to be positively associated with the total amount of NCPs and the proportions between some major NCPs in OVX rats, respectively.