| Objective:To investigate the effect of alendronate on microstructure and properties of hydroxyapatite and biomechanical strength in osteoporotic rats.Method:Eighty 3-months old female SD rats were divided into four groups (Control,Sham, ovariectomy, ovariectomya and Alendronate) with twenty animals in each group randomly. Group of sham exsect fat around the ovary during a double dorsal-lateral incision,Group of OVX and OVX+ALN exsect the ovary during a double dorsal-lateral incision.Rat were treated with alendronate for three months after three months after the surgery. Four groups of rats were raised at 9-months old. bone mineral density of lumbar and femur, bone metabolism(bone formation markers of PINP and bone resorption markers NTx) were compared between four groups during the 3-months old and 6-months old and 9-months old. Use the fifth lumbar vertebra and the right of femur to do the biomechanics and Micro-CT test. Use the fifth lumbar vertebra to test properties of hydroxyapatite with X-ray diffraction.Results:Compare with weight of control,OVX and OVA+ALN have increased remarkably(P<0.01).BMD of first to six lumbar vertebra,distal femur,femur neck and proximal tibia in OVX and OVX+ALN were significantly decreased compareed with control(P<0.01).After treatment of alendronate,BMD of aforementioned areas were significantly increased(P<0.01)。 Bone metabolism reserch show bone formation markers of PINP and bone resorption markers NTx both gradually increased with growth.After the ovariectomy, NTx increased remarkable compareed with control(P<0.01), NTx decreased significantly after treatment of alendronate(P<0.01).There is no different in four groups. Biomechanics of compression test in fifth lumbar revealed maximum load,maximum stress,elastic load,elastic stress and elastic modulus in both OVX and OVX+ALN are significantly reduced compared with control(P<0.05). Three-point bending test in right fumer show maximum load,maximum stress,elastic load,elastic stress and elastic modulus in both OVX and OVX+ALN are significantly reduced compared with control too(P<0.05). OVX and OVA+ALN micrt-ct parameters of bone volume/total volume (BV/TV), bone surface area/bone volume (BS/BV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and BMD in the trabecular region in fifth lumbar and distal femur were significantly decreased and trabecular separation (Tb.Sp) were significantly increased compareed with control(P<0.01).After the treatment of alendronate, aforementioned parameters improved notably.Parameters of Cortical of middle femur cortical thinkness, bone volume/total volume and BMD show no difference in four groups. X-ray diffraction revealed hydroxyapatite crystals became longer,ratio of crystal axis and crystallinity recuded after ovariectomy(P<0.05). After the treatment of alendronate, hydroxyapatite crystals became shorter,ratio of crystal axis and crystallinity increased appropriately after ovariectomy(P<0.05).Conclusion:Due to plunge of estrogen after ovariectomy to establish the rat model of osteoporosis,BMD of lumbar and fumer reduced obviously.Both bone absorption and the bone formation are increased,futhermore bone absorption increased significantly. The thin and porosity of trabecular leading to deterioration of the bone microarchitecture,which reduced the mechanical strength,futhermore,It cause the hydroxyapatite crystals became longer,ratio of crystal axis and crystallinity recuded.But after treatment of alendronate,which increased the BMD and mechanical strength notably,dreased the bone resorption,improved the mioroarchitecture.Also,it made hydroxyapatite crystals shorter and appropriately increased ratio of crystal axis and crystallinity... |
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