Estrogen receptor-α is developmentally regulated during osteoblast differentiation and contributes lo selective responsiveness of gene expression
Estrogen receptor-α is developmentally regulated during osteoblast differentiation and contributes lo selective responsiveness of gene expression
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DOI：
10.1210/en.139.4.2048
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发表时间：
1998-04-01
期刊：
影响因子：
4.8
通讯作者：
Komm, BS
中科院分区：
文献类型：
--
作者：
Bodine, PVN;Henderson, RA;Komm, BS
骨的雌激素反应性是骨稳态的基本调节机制。我们研究了雌激素受体-α（ER）信使RNA（mRNA）在培养的大鼠颅骨来源的成骨细胞的成骨细胞表型的渐进发展过程中的表达。ER信息的水平与传统的成骨细胞标记物的表达进行了比较，这些标记物已经在这些细胞的整个分化过程中被绘制出来。使用半定量BT-PCR分析测量的ER转录物在早期增殖成骨细胞中以低水平表达，并且在骨细胞表型基因初始表达后汇合时增加。ER mRNA表达的23倍上调与碱性磷酸酶活性的启动（第8天）相一致。ER mRNA水平逐渐增加70倍，在完全分化的成骨细胞中，当骨钙素表达达到峰值时，在第22-25天达到最大水平，但在骨细胞中，在第32天急剧下降。直接从大鼠颅骨分离的RNA的分析证实了这些体外结果，并证明ER信息水平在出生后随着骨变得更加矿化而变得更加丰富。我们还研究了成骨细胞对17 β-雌二醇（17 β-E-2）在两个成熟阶段的反应：结节形成阶段（第14天）和晚期矿化阶段（第30天）。在第14天，雌二醇抑制碱性磷酸酶、骨钙素、骨连接素和ER mRNA的水平，但在第30天上调这些信息。相反，17 β-E-2处理仅在矿化晚期调节转化生长因子β 1和I型前胶原mRNA的稳态水平，而组蛋白H4信息在分化的任一阶段均不受类固醇影响。因此，所观察到的ER mRNA的发育表达与成骨细胞的渐进性分化相关，并且可能是17 β-E-2对骨细胞基因表达的差异调节的一个促成因素。
Estrogen responsiveness of bone is a fundamental regulatory mechanism operative in skeletal homeostasis. We examined the expression of estrogen receptor-alpha (ER) messenger RNA (mRNA) in cultured rat calvarial-derived osteoblasts during progressive development of the osteoblast phenotype. Levels of ER message were compared with the expression of traditional osteoblastic markers that have been mapped throughout the differentiation process of these cells. ER transcripts, measured using semiquantitative BT-PCR analysis, were expressed at low levels in early stage proliferating osteoblasts and increased at confluence upon initial expression of bone cell phenotypic genes. A 23-fold up-regulation of ER mRNA expression coincided with the initiation of alkaline phosphatase activity (day 8). ER mRNA levels progressively increased 70-fold, reaching a maximum level on days 22-25 in fully differentiated osteoblasts when osteocalcin expression peaked, but declined precipitously by day 32 in osteocytic cells. Analysis of RNA isolated directly from rat calvaria confirmed these in vitro results and demonstrated that ER message levels become more abundant postnatally as bone becomes more mineralized. We also examined the responsiveness of osteoblasts to 17 beta-estradiol (17 beta-E-2) at two periods of maturation: the nodule-forming stage (day 14) and the late mineralization stage (day 30). Estradiol suppressed the levels of alkaline phosphatase, osteocalcin, osteonectin, and ER mRNAs on day 14, but up-regulated these messages on day 30. in contrast, 17 beta-E-2 treatment regulated the steady state levels of transforming growth factor-beta 1 and type I procollagen mRNAs only in the late mineralization stage, whereas histone H4 message was unaffected by the steroid at either stage of differentiation. Thus, the observed developmental expression of ER mRNA correlates with progressive osteoblast differentiation and may be a contributing factor to differential regulation of bone cell gene expression by 17 beta-E-2.