Niger Corinne, Geneau Graziello, Fiorini Céline, Defamie Norah, Pointis Georges, Mesnil Marc, Cronier Laurent
Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, USA.
J Cell Biochem. 2008 Jan 1;103(1):110-22. doi: 10.1002/jcb.21390.
Gap junctional intercellular communication (GJIC) permits coordinated cellular activities during developmental and differentiation processes. In bone, the involvement of the gap junctional protein, connexin-43 (Cx43), and of GJIC in osteoblastic differentiation and mineralization of the extracellular matrix has been previously demonstrated. Former studies have shown that endothelin-1 (ET-1) was also implicated in the control of osteoblastic proliferation and differentiation. However, depending on the cellular models, ET-1 has been shown to decrease or increase osteoblastic differentiation markers. As no data were available on the ET-1 effect on GJIC and Cx43 expression in osteoblastic cells, we analyzed here the possible crosstalk between Cx43 and ET-1 in a human cell line (hFOB 1.19) which displays different Cx43 expression levels and phenotypes when cultured at 33.5 or 39 degrees C. The presence of ET-1 (10(-8) M) for 2-12 days of culture did not significantly alter the proliferation rate of hFOB cells whatever their phenotype. In contrast, ET-1 induced a differential inhibitory effect on the biochemical differentiation markers (alkaline phosphatase activity and osteocalcin expression) with a significant reduction in the differentiated phenotype at 39 degrees C, whereas no effects were measured at 33.5 degrees C. The inhibitory effect was linked to a decrease of GJIC and of Cx43 both at transcriptional and protein levels. Altogether, our results suggest that Cx43 expression level could influence the action of ET-1 on human osteoblastic cell differentiation. Our data also indicate that the gap junctional protein could play a pivotal role in the response of osteoblasts to mitogenic factors implicated in bone pathologies.
缝隙连接细胞间通讯（GJIC）在发育和分化过程中允许细胞进行协调活动。在骨骼中，缝隙连接蛋白连接蛋白43（Cx43）以及GJIC参与成骨细胞分化和细胞外基质矿化的作用先前已得到证实。以往的研究表明，内皮素-1（ET-1）也参与成骨细胞增殖和分化的调控。然而，根据细胞模型的不同，ET-1已被证明可降低或增加成骨细胞分化标志物。由于尚无关于ET-1对成骨细胞中GJIC和Cx43表达影响的数据，我们在此分析了在人细胞系（hFOB 1.19）中Cx43与ET-1之间可能存在的相互作用，该细胞系在33.5℃或39℃培养时表现出不同的Cx43表达水平和表型。培养2 - 12天，ET-1（10⁻⁸ M）的存在并未显著改变hFOB细胞的增殖速率，无论其表型如何。相比之下，ET-1对生化分化标志物（碱性磷酸酶活性和骨钙素表达）具有不同的抑制作用，在39℃时分化表型显著降低，而在33.5℃时未检测到影响。这种抑制作用与转录和蛋白质水平上GJIC和Cx43的减少有关。总之，我们的结果表明Cx43表达水平可能影响ET-1对人成骨细胞分化作用。我们的数据还表明，缝隙连接蛋白可能在成骨细胞对涉及骨病理的有丝分裂原因子的反应中起关键作用。
