| Postmenopausal osteoporosis is the most common systemic skeletal disease affecting elderly women, which is characterized by low bone mass and microarchitectural deterioration with a consequence increase in bone fragility with susceptibility to fracture. This disease threatens seriously the health and life of elderly women and results in huge human and economic burden for family and society. Postmenopausal osteoporosis is a international public healthcare problem. The pathogenesis of postmeno -pausal osteoporosis are not well understood. Osteoblasts and adipocytes are derived from a common precursor in bone marrow, the mesenchymal stem cells(MSCs). Capacity of MSCs differentiate down the two lineages plays important roles in determining bone density because it has been shown that bone volume loss associated with osteoporosis is accompanied by reduced osteoblastic bone formation and increased marrow adipose tissue. In the basis of ovariectomied animal model, we investigate the proliferation capacity of MSCs from ovariectomied rats; and the differential capacity of these MSCs to osteoblast and adipocyte. Also, the study of MSCs from ovariectomied rats may provide a better understanding of the mechanisms involved in the pathogenesis of postmenopausal osteoporosis. We established animal model of osteoporosis in 3 old-months and 6 old-months female Sprague-Dawley rats(SD) with ovariectomy. Animal experiments were divided into 4 groups: 3control group, 3ovx group, 6control group and 6ovx group. MSCs were isolated by means of the density-gradient centrifugation method from rats. CFU-Fs number, CFU-Fs size distribution and cell density in CFU-Fs of primary passage MSCs were determined at the inverted phase contrast microscope. The cell ultrastructure of MSCs was observed at the transmission electron microscopy(TEM). The cell surface antigens(CD44/CD45) of MSCs were detected by flow cytometry(FCM). The cell cycle and proliferation index (PI) of MSCs were detected by FCM. After osteogenic induction(OSI), calcium nodes of MSCs were marked by alizarin red staining(ARS); The expression level of alkaline phosphatase(ALP) was detected by dynamics method with substrate of phosphoric acid para-Nitro benzene; The content of osteocalcin(OCN) was detected with the isotope labelling method. After adipogenic induction(ADI), the mRNA level of lipoprotein lipase(LPL) was measured by RT-PCR. Our results showed: 1) The weight of rats increased significantly in 3ovx group and 6ovx group; The weight of uterus decreased significantly in 3ovx group and 6ovx group; The bone mass decreased and the microartitecture of bone was impaired in ovariectomied osteoporotic rats at the 3th month after ovariectomy. 2) MSCs were positive for CD44 and negative for CD45 by FCM; The cell ultrastructure of MSCs was high ratio of the nucleus to cytoplasm by TEM. 3) CFU-Fs number and cell density in CFU-Fs of primary passage MSCs in 6control group were significant lower than those in 3control group; CFU-Fs number, CFU-Fs size distribution and cell density in CFU-Fs of primary passage MSCs in 3ovx group were significant lower than those in 3control group; CFU-Fs number, CFU-Fs size distribution and cell density in CFU-Fs of primary passage MSCs in 6ovx group were significant lower than those in 6 control group; CFU-Fs number and cell density in CFU-Fs of primary passage MSCs in 6ovx group were significant lower than those in 3ovx group; 4) Compared with 3control group, PI of MSCs in 3ovx group decreased; PI of MSCs in 6ovx group was the lowest among four groups. 5) After osteogenic induction, the number and size of calcium nodes, theexpression level of ALP and the content of OCN of MSCs in 6control group were markedly lower than those in 3control group; The number and size of calcium nodes,the expression level of ALP and the content of OCN of MSCs in 3ovx group were markedly lower than those in 3control group; The number and size of calcium nodes,the expression level of ALP and the content of OCN of MSCs in 6ovx group were markedly lower than those in 6control group; The number and size of calcium nodes,the expression level of ALP and the content of OCN of MSCs in 6ovx group were markedly lower than those in 3ovx group. 6) After adipogenic induction, the mRNA level of LPL of MSCs in 6control group was markedly higher than that in 3control group; The mRNA level of LPL of MSCs in 3ovx group was markedly higher than that in 3control group; The mRNA level of LPL of MSCs in 6ovx group is markedly higher than that 6control group; The mRNA level of LPL of MSCs in 6ovx group is markedly higher than that in 3ovx group. Our results suggest: 1) The osteoporotic model that caused by ovariectomied in 3 old-months and 6 old-months female rats is similar to post-menopausal osteoporosis in women. 2) MSCs are positive for CD44 and negative for CD45 by FCM; The cell ultrastructure of MSCs is high ratio of the nucleus to cytoplasm by TEM. These results identify that our isolated cells are bone marrow mesenchymal stem cells distinct from the hemopoietic stem cell. 3) We can conclude it that the proliferative potential of MSCs derived from ovariectomied osteoporotic rats is decreased from the parameters of CFU-Fs number, CFU-Fs size distribution,cell density in CFU-Fs,cell ultrastructure and cell PI. 4) Osteogenic potential of MSCs from ovariectomied osteoporotic rats is decreased but adipogenic potential is increased.
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