Establishment of Tree Shrew Osteoporosis Model by Bilateral Ovariectomy

［Abstract］Objective To establish the tree shrew osteoporotic model by bilateral ovariectomy．Methods　Sixty healthy female tree shrews（Tupaia belangeri chinensis）were divided into operation group（OVX，n＝30） and sham group （SHAM，n＝30）. The bilateral ovaries of the tree shrews in OVX group were operated to resect， while in SHAM omentum majus were removed with the same volume of the ovaries．The BMD on six animals randomly selected in two groups were detected on the day before operation and on 1st，2nd， 3rd，4th，5th and 6th month after operation respectively. Six tree shrews of each group were sacrificed respectively pre-operation and post-operation when there was a difference（P＜0.05）or a significant difference（P＜0.01）in BMD values between SHAM group and OVX group. Then the second lumbar vertebras were sectioned for histomorphometry. Results（1）No death occurred during experiment. （2）The BMD values of tree shrew's whole body in SHAM group at each time point had no difference（P≥0.05）；The trabecula in the second lumbar vertebras was complete， regular and closely arranged. The connection between bone trabecula was normal. Bone marrow cells were rich while fat vacuoles were few. （3）Three months after operation，the BMD value in the OVX group was obviously lower than that in the SHAM's（P<0.05）. The sections of the second lumbar vertebras in OVX group showed that the trabecular bone was broken，thinning and scattered，moreover the trabecular spacing was widened， irregular arranged and the connection between the trabecular meshwork became less while bone marrow cells were reduced and more fat vacuoles appeared. （4）After four months，the whole body BMD in OVX group was significantly lower than that in SHAM'S （P＜0.01）. The sections in OVX group showed the trabecular bone was sparser and thinner than that in the 3rd month， and the trabecular connection was rare while bone marrow cells were further reduced and fat vacuoles became larger.（5）Six months after operation， the whole body BMD value in OVX group declined by 31% with a significant BMD change（P＜0.01）compared with the value in pre-operation. The sections showed thinner trabecula， wider trabecular spacing，less bone marrow cells and more fat vacuoles. Conclusion　Bilateral ovariectomy on 6 month-old tree shrews could establish stable osteoporosis model after four months.