Tibia bone properties at different time course of ovariectomized rats.

Background: The model of bilaterally ovariectomized rats mimics the accelerated bone loss observed in postmenopausal women due to estrogen deficiency. Although calcium is main mineral in bone, previous study in human showed there is hypermineralization and higher calcium level in hydroxyapatite crystal structure from osteoporosis patients. This study was aimed to investigate the effect of time course ovariectomized on tibia bone turn over markers, mineral elements, hydroxyapatite crystale, mesostructure, and histomorphometry.

Methods: A total of 30 Wistar female rats were randomly assigned into three groups (n = 10 each): control group, ovariectomy group follow up for one month and two month. All animals procedures was according to Animal Ethics Guidelines and approval by ethic committee of the Medical Faculty, Lambung Mangkurat University which obtained prior the study. Expression of osteocalcin (OC) and C-telopeptyde collagen type I (CTX) was analyzed by ELISA method. Tibia bone mineral element was measured using X-Ray Fluorescence. Hydroxyapatite crystale structure was analyzed using X-Ray Diffracttion. Mesostructure was determined using Scanning Electron Microscope. Histomorphometry was analyzed using BoneJ software analyzer. ANOVA test was used to analyze the different level of serum bone turnover markers and bone mineral elements.

Results: Serum OC and CTX were significantly decrease in one month and two month after ovariectomized groups compared to sham-operated group (P < 0.05). The levels Ca, P, Fe, Cu, Zn, Ni, Ca/P, and Cu/Zn were not significantly different in all groups (P > 0.05). The structure of hydroxyapatite crystal in one month and two month after ovariectomized groups were different compared with sham-operated control group. Mesostructure of tibia bone after one and two month ovariectomized procedure significantly different than that in sham-operated rats. The level of trabecular volume were lower significantly on OVX-1 and OVX-2 groups compared with sham group (P < 0.05). The trabecular thickness and spacing were increase significantly on OVX-1 and OVX-2 groups compared with sham group (P < 0.05). The trabecular number were significantly decrease OVX-1 and OVX-2 groups than that sham group (P < 0.05).

Conclusion: We found that two month after ovariectomized decrease serum osteocalcin but not change bone mineral elements in rats. Also, we found the difference of lattice parameter of hydroxyapatite crystale structure and trabecular properties which determined bone mesostructure.