Effect Of Ovariectomized Surgery On The Bone Microstructure And Mechanical Properties Of Rats Of Different Months

The clinical features of osteoporosis are decreased on bone mass,deterioration of bone microstructure,weakened bone mechanical properties,and increased risk of fractures.The mst of patients with osteoporosis are the elderly,especially older women.This study aims to investigate the changes in bone microstructure and mechanical properties of women of different ages after menopause for different lengths of time.In this study,an ovariectomized surgery was made,and selected 5-month-old and 9-month-old SD rats as the research objects.The effects of ovariectomized surgery on the microstructure and mechanical properties of bones at different months of age from both the macroscopic and microscopic perspectives was studied.90 female SD rats was selected and divide them into 6 experimental groups equally: 5-month-old basic control group(5-CON);9-month-old basic control group(9-CON);5-monthold recovery group for 8 weeks after castration(5-OVX-8);9-month-old castration recovery for 8 weeks group(9-OVX-8);5-month-old castration recovery for 16-week group(5-OVX-16);9-month-old castration recovery group(5-OVX-16)recovery group for 16 weeks(9-OVX-16).After two weeks of acclimatization to the environment,the rats in the castrated group were castrated.The rats in the control group were sacrificed and the left and right tibias,femurs and serum were taken;at the 8th week,the rats of 5 months and 9 months old were sacrificed,and the left and right tibias,femurs and serum were taken;at the 16 th week,the rats of 5 and 9months old were sacrificed,and the left and right tibias,femurs and serum were taken.First,the left tibia and femur were scanned and the screenage was reconstructed by Micro-CT to obtain the microstructural parameters of the tibia and femur;secondly,the three-point bending test was performed on the right femur,and the mechanical compression test on the right tibia was performed to obtain the elastic modulus,stiffness and maximum load bearing capacity;then serum was tested,and the bone resorption marker type I collagen C-terminal peptide(CTX-I),tartrate-resistant acid phosphatase(TRACP)and bone formation marker osteocalcin(OC),Alkaline Phosphatase(ALP).The results of this study showed that the bone mineral density(BMD),trabecular volume fraction(BV/TV),and trabecular thickness(Tb.N)of the proximal tibia and distal femur in the5-CON group were significantly higher than 9-CON group(p<0.05);Tb.Sp of the proximal tibia and distal femur of the 5-CON group was significantly lower than that of the 9-CON group(p<0.05);all structures in the distal femur in the 5-CON group.The parameters were not significantly different from those in the 5-OVX-8 group(p>0.05).The Tb.Th of the proximal tibia in the 5-CON group was significantly lower than that in the 5-OVX-8 and 5-OVX-16groups(p<0.05).The Ct.Th of the cortical bone in the middle tibia of 5-month-old rats increased first and then decreased.The BMD,BV/TV and Tb.N of the proximal tibia and distal femur of the 9-CON group were significantly higher than those of the 9-OVX-8 and 9-OVX-16 groups(p<0.05).Compared with the 5-CON group,the elastic modulus and stiffness of the femur of the 9-CON group increased significantly(p<0.05).The elastic modulus of the femur and tibia of the 5-month-old and 9-month-old ovariectomized rats were higher than those of the same months of age(p<0.05),and the elastic modulus of the femur and tibia of rats in the 16-week recovery group after castration was significantly lower than that of the 8-week recovery group(p<0.05).Serum test results showed that the concentration of CTX-I in the 5-CON group was higher than that in the 9-CON group,and the OC content in the 5-OVX-8 and 5-OVX-16 groups were significantly higher than that in the 5-CON group(p<0.05).And the 5-OVX-16 group is higher than the 5-OVX-8 group.The conclusion can be drawn from the results of the study: the microstructure and mechanical properties of the tibia and femur of rats at the age of 5 and 9 months have undergone significant degeneration after castration,and the longer the time after castration,the more obvious the degeneration.And at the same time compared with 5-month-old rats,the microstructure and mechanical properties of tibia and femur of the 9-month-old rats are worse.It can be seen that the risk of osteoporosis in women after menopause is significantly increased;the longer a woman is after menopause,the higher the risk of osteoporosis,and the older the woman,the greater the risk of osteoporosis.