Walsh S, Jordan G R, Jefferiss C, Stewart K, Beresford J N
Bone Research Group, Department of Pharmacy and Pharmacology, 7 West, University of Bath, Claverton Down, Bath BA2 7AY, UK.
Rheumatology (Oxford). 2001 Jan;40(1):74-83. doi: 10.1093/rheumatology/40.1.74.
The use of glucocorticoids (GCs) in the treatment of RA is a frequent cause of bone loss. In vitro, however, this same class of steroids has been shown to promote the recruitment and/or maturation of primitive osteogenic precursors present in the colony forming unit-fibroblastic (CFU-F) fraction of human bone and marrow. In an effort to reconcile these conflicting observations, we investigated the effects of the synthetic GC dexamethasone (Dx) on parameters of growth and osteogenic differentiation in cultures of bone marrow stromal cells derived from a large cohort of adult human donors (n=30).
Marrow suspensions were cultured in the absence and presence of Dx at concentrations between 10 pm and 1 microm. After 28 days we determined the number and diameter of colonies formed, the total number of cells, the surface expression of receptors for selected growth factors and extracellular matrix proteins and, based on the expression of the developmental markers alkaline phosphatase (AP) and the antigen recognized by the STRO-1 monoclonal antibody, the proportion of cells undergoing osteogenic differentiation and their extent of maturation.
At a physiologically equivalent concentration, Dx had no effect on the adhesion of CFU-F or on their subsequent proliferation, but did promote their osteogenic differentiation and further maturation. These effects were independent of changes in the expression of the receptors for fibroblast growth factors, insulin-like growth factor 1, nerve growth factor, platelet-derived growth factors and parathyroid hormone/parathyroid hormone-related protein, but were associated with changes in the number of cells expressing the alpha(2) and alpha(4), but not beta(1), integrin subunits. At supraphysiological concentrations, the effects of Dx on the osteogenic recruitment and maturation of CFU-F and their progeny were maintained but at the expense of a decrease in cell number.
A decrease in the proliferation of osteogenic precursors, but not in their differentiation or maturation, is likely to be a key factor in the genesis of GC-induced bone loss.
糖皮质激素（GCs）用于治疗类风湿性关节炎（RA）是导致骨质流失的常见原因。然而在体外实验中，同一类甾体激素已被证明可促进人骨髓集落形成单位-成纤维细胞（CFU-F）部分中原始成骨前体细胞的募集和/或成熟。为了调和这些相互矛盾的观察结果，我们研究了合成糖皮质激素地塞米松（Dx）对来自大量成年人类供体（n = 30）的骨髓基质细胞培养物中生长和骨生成分化参数的影响。
骨髓悬液在不存在和存在浓度介于10皮摩尔和1微摩尔之间的Dx的情况下进行培养。28天后，我们测定形成的集落数量和直径、细胞总数、选定生长因子和细胞外基质蛋白受体的表面表达，并基于发育标志物碱性磷酸酶（AP）和STRO-1单克隆抗体识别的抗原的表达，确定发生成骨分化的细胞比例及其成熟程度。
在生理等效浓度下，Dx对CFU-F的黏附或其随后的增殖没有影响，但确实促进了它们的成骨分化和进一步成熟。这些作用与成纤维细胞生长因子、胰岛素样生长因子1、神经生长因子、血小板衍生生长因子和甲状旁腺激素/甲状旁腺激素相关蛋白受体表达的变化无关，但与表达α(2)和α(4)而非β(1)整合素亚基的细胞数量变化有关。在超生理浓度下，Dx对CFU-F及其后代的成骨募集和成熟的作用得以维持，但代价是细胞数量减少。
成骨前体细胞增殖减少而非其分化或成熟减少，可能是GC诱导骨质流失发生的关键因素。
