Dexamethasone stimulates osteogenesis in chick periosteum in vitro.
Dexamethasone stimulates osteogenesis in chick periosteum in vitro.
复制标题
地塞米松在体外刺激鸡骨膜的成骨作用。
作者：
Howard C. Tenenbaum;J. Heersche
来自 16 天鸡胚颅骨的折叠骨膜外植体在化学成分确定、补充激素的培养基或血浆凝块上培养 6 天后会分化并形成骨骼。我们研究了地塞米松对此类培养物中具有成骨细胞表型的细胞生成的影响。通过测定碱性磷酸酶（AP）活性来评估骨细胞表型。通过测量鸟氨酸脱羧酶（ODC）活性、[3H]胸苷摄取以及掺入[3H]胸苷的培养物的放射自显影来评估细胞增殖。从培养开始或从培养的第二天或第四天开始，将培养物暴露于各种培养基浓度的地塞米松（10(-6) M、10(-7) M、10(-8) M）。在连续暴露于地塞米松并维持在化学成分确定的培养基或血浆凝块中的培养物中，地塞米松增加了第6天测量的AP活性。这种效果在10(-7)M地塞米松时达到最大。在培养第2天后暴露于地塞米松的培养物也显示出AP活性增加，但仅限于维持在血浆凝块上的培养物。当在任一培养基的培养第4天添加地塞米松时，没有刺激AP活性，因此表明糖皮质激素的作用取决于培养物的分化阶段。除了AP刺激之外，地塞米松还刺激ODC活性。由于 ODC 活性与间充质细胞增殖相关，这表明地塞米松刺激了培养的骨膜中类似细胞的增殖。测量对照培养物和用地塞米松处理的培养物中的[3H]胸苷摄取并进行放射自显影证实确实发生了增殖刺激，并将这种增殖定位在邻近骨表面的细胞层内。这些结果证明地塞米松刺激体外成骨，并且这种作用似乎是通过刺激祖细胞增殖来介导的。此外，我们的数据表明凝块培养基中的因子调节前体细胞群的反应性。
Folded periosteal explants derived from 16-day-old chick embryo calvariae differentiate and form bone when cultured for 6 days in chemically defined, hormone-supplemented medium or on plasma clots. We studied the effect of dexamethasone on generation of cells with osteoblastic phenotype in such cultures. Bone cell phenotype was evaluated by determination of alkaline phosphatase (AP) activity. Cellular proliferation was assessed by measuring ornithine decarboxylase (ODC) activity, [3H]thymidine uptake, and radioautography of cultures that had incorporated [3H]thymidine. Cultures were exposed to various medium concentrations of dexamethasone (10(-6) M, 10(-7) M, 10(-8) M) from the outset or from the second or fourth day of culture onwards. In cultures continuously exposed to dexamethasone and maintained in chemically defined media or on plasma clots, dexamethasone increased AP activity measured at day 6. This effect was maximal at 10(-7) M dexamethasone. Cultures exposed to dexamethasone after day 2 in culture also showed increased AP activity, but only in the cultures maintained on plasma clots. There was no stimulation of AP activity when dexamethasone was added at day 4 of culture with either medium, thus suggesting that the effect of glucocorticoids depends on the stage of differentiation of the cultures. In addition to AP stimulation, dexamethasone also stimulated ODC activity. Since ODC activity has been associated with mesenchymal cell proliferation, this suggested that dexamethasone stimulated the proliferation of similar cells in the cultured periostea. Measuring [3H]thymidine uptake in and performing autoradiography of control cultures and cultures treated with dexamethasone confirmed that stimulation of proliferation did occur and located this proliferation within the cell layer adjacent to the bone surface. These results demonstrate that dexamethasone stimulates in vitro osteogenesis, and that this effect appears to be mediated through stimulation of progenitor cell proliferation. In addition, our data indicate that factors in the clot medium modulate the responsiveness of the precursor cell population.