Hypoxia in the vicinity of bone defects triggers the osteogenic differentiation of precursor cells and promotes healing. The activation of STAT3 signaling in mesenchymal stem cells (MSCs) has similarly been reported to mediate bone regeneration. However, the interaction between hypoxia and STAT3 signaling in the osteogenic differentiation of precursor cells during bone defect healing is still unknown. In this study, we assessed the impact of different durations of CoCl2-induced cellular hypoxia on the osteogenic differentiation of MSCs. Role of STAT3 signaling on hypoxia induced osteogenic differentiation was analyzed both in vitro and in vivo. The interaction between cellular hypoxia and STAT3 signaling in vivo was investigated in a mouse femoral bone defect model. The peak osteogenic differentiation and expression of vascular endothelial growth factor (VEGF) occurred after 3 days of hypoxia. Inhibiting STAT3 reversed this effect. Hypoxia enhanced the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and STAT3 phosphorylation in MSCs. Histology and μ-CT results showed that CoCl2 treatment enhanced bone defect healing. Inhibiting STAT3 reduced this effect. Immunohistochemistry results showed that CoCl2 treatment enhanced Hif-1α, ALP and pSTAT3 expression in cells present in the bone defect area and that inhibiting STAT3 reduced this effect. The in vitro study revealed that the duration of hypoxia is crucial for osteogenic differentiation of precursor cells. The results from both the in vitro and in vivo studies show the role of STAT3 signaling in hypoxia-induced osteogenic differentiation of precursor cells and bone defect healing.

中文翻译：

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细胞缺氧通过 STAT3 信号促进间充质干细胞的成骨分化和骨缺损愈合。

骨缺损附近的缺氧会触发前体细胞的成骨分化并促进愈合。据报道，间充质干细胞 (MSCs) 中 STAT3 信号传导的激活可介导骨再生。然而，在骨缺损愈合过程中，前体细胞成骨分化中缺氧和 STAT3 信号传导之间的相互作用仍然未知。在这项研究中，我们评估了不同持续时间的 CoCl2 诱导的细胞缺氧对 MSCs 成骨分化的影响。在体外和体内分析了 STAT3 信号在缺氧诱导的成骨分化中的作用。在小鼠股骨缺损模型中研究了体内细胞缺氧和 STAT3 信号传导之间的相互作用。缺氧3天后，成骨分化和血管内皮生长因子（VEGF）的表达达到峰值。抑制 STAT3 可以逆转这种效应。缺氧增强了 MSCs 中缺氧诱导因子 1-α (HIF-1α) 和 STAT3 磷酸化的表达。组织学和 μ-CT 结果表明，CoCl2 治疗可促进骨缺损愈合。抑制 STAT3 降低了这种影响。免疫组织化学结果表明，CoCl2 处理增强了存在于骨缺损区域的细胞中 Hif-1α、ALP 和 pSTAT3 的表达，而抑制 STAT3 则降低了这种作用。体外研究表明，缺氧的持续时间对于前体细胞的成骨分化至关重要。