Cell Biological Investigation of Disturbances in Bone Cell Functions with their Application to the Treatment of Osteoporosis

为了阐明骨质疏松症的发病机制，寻找防治骨质疏松症的方法，本论文进行了以下研究：1.促钙激素刺激下的成骨细胞产生骨吸收刺激活性：1，25(OH)_2D刺激成骨细胞产生骨吸收刺激活性。S因子与细胞-基质表面结合，与肝素有亲和力。用反相高效液相色谱和凝胶过滤层析对BRSA进行纯化，得到两个峰。进一步的纯化工作正在进行中，以确定这一因素。成骨细胞在雌激素刺激下产生的骨吸收抑制活性(BRIA)：成骨细胞经雌激素处理后，BRIA的形成与细胞/基质表面有关，对肝素表现出亲和力。加热和胰酶处理使该因子失活，表明该因子是一种蛋白质。破骨细胞形成和功能的调节：24，25(OH)_2D抑制破骨细胞性骨吸收。由于24，25(OH)_2D既能抑制造血干细胞形成破骨细胞，又能抑制兔破骨细胞在牙本质片上形成的吸收陷窝，因此对破骨细胞的形成和功能均有抑制作用。并研究了细胞外钙对破骨细胞膜内向整流钾通道的影响。发现细胞外钙升高通过抑制内向整流钾通道而增强破骨细胞的去极化。成骨细胞中生长因子的产生和作用的调节：成骨细胞的长期培养促进分化。成骨细胞的分化与I型和II型转化生长因子-β受体的缺失以及转化生长因子-β对这些细胞的影响有关。

In order to clarify the underlying mechanism for the development of osteoporosis, as well as to search for the ways to prevent and treat osteoporosis, the following investigations were performed :1. Bone resorption-stimulating activity(BRSA) elaborated form osteoblasts under stimulation by calciotropic hormones : Treatment of osteoblastic cells with 1,25(OH)_2D stimulated the elaboration of BRSA.The factor(s) were associated with cell-matrix surface and showed an affinity for heparin. The BRSA was purified by reversed phase HPLC and gel filtration chromatography to obtain two peaks. Further purification is under way to identify this factor.2. Bone resorption-inhibitory activity(BRIA) elaborated from osteoblasts under stimulation by estrogen : Treatment of osteoblastic cells with estrogen caused the elaboration of BRIA.The BRIA was also associated with cell/matrix surface and exhibited affinity for heparin. The factor was inactivated by heat and trypsin treatment, suggesting that it was a protein.3. Regulation of osteoclast formation and function : Osteoclastic bone resorption was inhibited by 24,25(OH)_2D.Because 24,25(OH)_2D inhibited both the formation of osteoclastic cells from hemopoietic stem cells and the resorption pit formation by rabbit osteoclasts on dentine slices, it appeared to inhibit both the formation and function of osteoclasts. The effect of extracellular Ca on oeteoclast membrane inward rectifying K channel was also investigated. It was found that the elevation in extracellular Ca enhanced depolarization of osteoclasts by inhibiting the inward rectifying K channel.4. Regulation of the production and actions of growth factors in osteoblasts : Long-term cultures of osteoblastic cells enhance the differentiation. The differentiation of osteoblasts was associated with a loss of both types I and II TGF-beta receptors and the effect of TGF-beta on these cells.