The maturity of osteoblasts by proliferation and differentiation in preosteoblasts is essential for maintaining bone homeostasis. The beneficial effects of vitamin D on bone homeostasis in mammals have been demonstrated experimentally and clinically. However, the direct actions of vitamin D on preosteoblasts remain to be fully elucidated. In this study, we found that the functional activity of intermediate-conductance Ca²⁺-activated K⁺ channels (K_Ca3.1) positively regulated cell proliferation in MC3T3-E1 cells derived from mouse preosteoblasts by enhancing intracellular Ca²⁺ signaling. We examined the effects of treatment with vitamin D receptor (VDR) agonist on the expression and activity of K_Ca3.1 by real-time PCR examination, Western blotting, Ca²⁺ imaging, and patch clamp analyses in mouse MC3T3-E1 cells. Following the downregulation of K_Ca3.1 transcriptional modulators such as Fra-1 and HDAC2, K_Ca3.1 activity was suppressed in MC3T3-E1 cells treated with VDR agonists. Furthermore, application of the K_Ca3.1 activator DCEBIO attenuated the VDR agonist-evoked suppression of cell proliferation rate. These findings suggest that a decrease in K_Ca3.1 activity is involved in the suppression of cell proliferation rate in VDR agonist-treated preosteoblasts. Therefore, K_Ca3.1 plays an important role in bone formation by promoting osteoblastic proliferation under physiological conditions.

中文翻译：

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维生素D受体激动剂处理的小鼠成骨细胞中Ca2 +激活的K +通道KCa3.1的下调。

通过成骨细胞的增殖和分化，成骨细胞的成熟对于维持骨稳态是必不可少的。维生素D对哺乳动物骨稳态的有益作用已通过实验和临床证明。但是，维生素D对成骨细胞的直接作用仍有待充分阐明。在这项研究中，我们发现中等传导性Ca ²⁺激活的K ⁺通道（K _Ca 3.1）的功能活性通过增强细胞内Ca ²⁺信号传导来正调控源自小鼠前成骨细胞的MC3T3-E1细胞的细胞增殖。我们检查了维生素D受体（VDR）激动剂对K _Ca的表达和活性的影响3.1通过实时PCR检查，蛋白质印迹，Ca ²⁺成像和膜片钳分析对小鼠MC3T3-E1细胞进行分析。在下调K _Ca 3.1转录调节因子（例如Fra-1和HDAC2）后，在用VDR激动剂处理的MC3T3-E1细胞中，K _Ca 3.1活性受到抑制。此外，K _Ca 3.1激活剂DCEBIO的应用减弱了VDR激动剂引起的细胞增殖速率的抑制。这些发现表明，在VDR激动剂处理的成骨细胞中，K _Ca 3.1活性的降低与细胞增殖速率的抑制有关。因此，K _Ca3.1通过在生理条件下促进成骨细胞增殖在骨形成中起重要作用。