| Background:The postmenopausal osteoporosis(PMO),also known as ? type osteoporosis,is a common systematic skeletal disease.Estrogen deficiency has been demonstrated to be an important pathogenesis of PMO.PMO is often accompanied with other diseases,of which chronic periodontitis is a common one.The chronic periodontitis characterized by periodontal attachment loss and alveolar bone resorption can bring the cure difficulty in orthodontics,oral implantology and prosthodontics.Bone marrow mesenchymal stem cells(BMMSCs)originating from mesoderm have the ability for self-renewal and multiple differentiation potential.BMMSCs,which can be differentiated into many cells in culture,such as osteocyte,chondrocyte,lipocyte and so on,play an important role in the balance of bone metabolism.The dysfunction of BMMSCs seems to play a significant role in the osteoporosis.The proliferation capacity and osteogenic potential of BMMSCs derived from osteoporosis were declined,while the adipogenic potential was increased.The bone mass reduces and fat increases in medullary cavity of PMO may be related with the function changes of BMMSCs.The parathyroid hormone(PTH)is an important hormone in mediating bone metabolism,which has double effects: continue and large dose use can induce bone resorption,however,intermittent and low dose use can promote osteogenesis.But the relative mechanisms are not clear limiting the clinical use of PTH.Moreover,most of past research focused on osteoblasts,leading to little knowledge of effect of PTH on BMMSCs.Objective:This study aims to investigate the effect of intermittent and low dose use of PTH on bone marrow microenvironment,particularly BMMSCs so that we can reveal the mechanism of PTH promoting bone formation from the view of cellular level,which can contribute to the clinical of PTH.Contents:(1)Research the impact of intermittent and low dose use of PTH on bone mass and bone histomorphometry in ovariectomized rats.(2)Research the impact of intermittent and low dose use of PTH on proliferation and apotosis of BMMSCs in ovariectomized rats.(3)Research the impact of intermittent and low dose use of PTH on multiple differentiation potential of BMMSCs in ovariectomized rats.Methods:(1)An animal osteoporosis model was set up through ovariectomy.A part of the animals were given subcutaneous injection of PTH1-34 six weeks after operation,which lasted for five weeks.We evaluate the animal mode by Micro-CT and histochemical stain,meanwhile we compare the bone mass and bone histomorphometry in Sham group,OVX group and the OVX +PTH1-34 group.(2)BMMSCs were isolated and cultured through the method of whole bone marrow adherent,and then identified by means of cell morphology and cell surface markers.(3)The biological characteristics of BMMSCs in three groups were compared by flow cytometry,growth curve and the differentiation trial vitro.Results:(1)We found that BV/TV,Tb.Th,BS/BV of rat femurs in OVX group were significantly lower than those of Sham group.And a serious fall in the number and a disordered arrangement of bone trabecula of rat femurs in OVX group were found.This suggest that we established the animal model successfully.In addition,BV/TV,Tb.Th,BS/BV of rat femurs in OVX+PTH1-34 group were significantly higher than those of OVX group.Moreover,the number of bone trabecula was increased and arranged more structured in OVX+PTH1-34 group when compared to the OVX group.These proved the promotion of PTH on bone formation.(2)The typical long spindle-shaped and swirling cells can be seen by an inverted phase contrast microscope.The cell morphology of BMMSCs in the OVX+PTH1-34 group was closed to the Sham group,however,the BMMSCs in the OVX group were larger and more rounded than the cells in OVX+PTH1-34 group.According to the flowcytometry results,high expression of surface markers of mesenchymal stem cells and faint expression of surface markers of hematopoietic cells suggest the acquisition of BMMSCs.(3)We also found that proliferation ability of BMMSCs in OVX+PTH1-34 group was significantly stronger than that of OVX group,and the apoptosis was decreasing by comparing the curve of cell growth,the cell rate at S phase and the apoptosis rate.And the osteogenic differentiation potential of BMMSCs in OVX+PTH1-34 group was found to be significantly higher when compared with OVX group by means of alkaline phosphatase staining,alizarin red staining and qRT-PCR.Besides,the adipogenic differentiation potential of BMMSCs in OVX+PTH1-34 group seemed to be depressed through oil red O staining and qRT-PCR.Conclusions:(1)The intermittent and low dose use of PTH can effectively improve bone mass and bone histomorphometry of ovariectomized rats.(2)The intermittent and low dose use of PTH can increase the proliferation ability of BMMSCs from ovariectomized rats,while can cause the inhibition of apoptosis.(3)The intermittent and low dose use of PTH can strengthen the osteogenic differentiation potential of BMMSCs from ovariectomized rats.But the adipogenic differentiation potential of BMMSCs from ovariectomized rats can be retrained by intermittent and low dose use of PTH. |
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