Bone marrow contains a population of mesenchymal stem cells with the ability to differentiate into cells that form bone, cartilage, adipose, and other connective tissues. Stem cells can be isolated from bone marrow aspirates and expanded in vitro. Presently, most stem cells studies have been performed in cells obtained from ''healthy'' control subjects. The goal of this study was to compare the functional characteristics of mesenchymal stem cells derived from ''healthy'' control and osteoporotic postmenopausal women to better understand the mechanisms involved in the pathogenesis of this disease. Osteoporotic and control stem cells have similar morphology and size and express similar cell surface antigens as evidenced by their reactivity with cell specific monoclonal antibodies. Mesenchymal stem cells from osteoporotic women differ from controls in having a lower growth rate than control cells, being refractory to the mitogenic effect of IGF-1, and exhibiting a deficient ability to differentiate into the osteogenic linage as evidenced by the alkaline phosphatase activity and calcium phosphate deposition. We conclude that in osteoporosis stem cell growth, proliferative response and osteogenic differentiation are significantly affected. Also, the study of mesenchymal stem cells from osteoporotic postmenopausal women may provide a better understanding of the mechanisms involved in the pathogenesis of the osteoporosis. It may also serve to test in vitro in rapid manner novel new therapeutic strategies.

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The effects of progesterone on oophorectomy-induced bone loss in aged rats were evaluated. Female rats aged 12 months were divided into three groups: (1) sham-operated controls (SHAM); (2) oophorectomized (OVX); (3) OVX rats treated with progesterone (OVX + PROG). After 20 weeks the dry weight, bone ash, and calcium content of femur, tibia, and fourth lumbar vertebra were significantly lower in OVX than in sham rats. These reductions did not occur in OVX rats treated with PROG. There was no difference in the bone composition between the control and progesterone-treated rats. Vertebral bone histomorphometry showed increased bone resorption as well as increased bone formation parameters in OVX rats. Progesterone treatment inhibited the increased resorption indices, but the bone formation remained elevated. The results indicate that progesterone therapy prevents the postovariectomy bone loss in aged rats. The protective effect of progesterone is mediated by inhibition of bone resorption while maintaining the increased bone formation. These findings suggest that progesterone alone may be a valuable agent for management of postmenopausal osteoporosis.

The aim of the present study was to assess the impact of treatment with GH with or without LHRH analog (LHRH-A) on bone mineralization of GH-deficient adolescents. We studied 17 pubertal, treatment-naive, GH-deficient patients (10 girls and 7 boys) in a prospective, randomized trial. Mean chronological age and mean bone age were 14.1 +/- 0.4 and 11.3 +/- 0.3 yr, respectively, at the beginning of the study. Treatment with GH + LHRH-A (n = 7) or GH alone (n = 10) started simultaneously. Nutropin was administered at a dose of 0.1 U/kg per day sc until patients reached near final height (NFH), defined as a bone age of 14 yr in girls and 16 yr in boys. Mean time of GH therapy in the patients treated with GH+LHRH-A was 4.8 +/- 0.5 yr and in the patients treated with GH alone 2.9 +/- 0.7 yr. Lupron was administered at a dose of 300 microg/kg every 28 d im for 3 yr. Bone mineral density (BMD) was assessed yearly by dual-energy x-ray absorptiometry at the lumbar spine (L2-L4) and femoral neck at the beginning of the study, after 3 yr of hormonal therapy, and at NFH. Statistical analysis was performed by t test and ANOVA. We observed a significant increase in lumbar and femoral bone mineral content, BMD, SD score, and bone mineral apparent density, compared with baseline in both groups of patients, regardless of whether they were treated with GH alone or in combination with LHRH-A. The patients treated with GH + LHRH-A had a significantly lower bone mineral content after 3 yr of therapy. This difference, however, did not persist after both groups of patients reached NFH. These results indicate that delaying puberty with LHRH-A in GH-deficient patients treated with GH diminishes transient bone mineralization but does not appear to have a permanent impact on BMD.

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