Stem cell therapy provides an attractive solution for intervertebral disc (IVD) degeneration. However, the degenerative microenvironment, characterized by excessive mechanical loading and hypoxia, remains an obstacle for the long-lasting survival of exogenous transplanted stem cells. Whether and how bone marrow mesenchymal stem cells (BMSCs) adapt to the hostile microenvironment remain unclear. In this study, CoCl₂ and mechanical compression were simultaneously used to simulate the hypoxic and overloaded microenvironment of IVDs in vitro. Compression had a proapoptotic effect through activation of the mitochondrial apoptotic pathway, while hypoxia exerted a prosurvival effect counteracting compression-induced apoptosis. Inhibiting the transcriptional activity of hypoxia inducible factor 1 subunit alpha (HIF-1α) by chetomin reversed the antiapoptotic effect of hypoxia. Furthermore, HIF-1α promoted dephosphorylation and activation of yes-associated protein (YAP) in hypoxic conditions. Conversely, both YAP inhibition and increased cell apoptosis were observed after inhibition through chetomin or YAP inhibitor verteporfin. Immunofluorescence staining and coimmunoprecipitation assays revealed that YAP could interact directly with HIF-1α and colocalize in the nucleus. Taken together, our results demonstrated that hypoxia protected BMSCs against compression-induced apoptosis in the degenerative disc microenvironment through activation of the HIF-1α/YAP signaling pathway. Thus, regulation of HIF-1α/YAP signaling might provide novel insights for promoting long-lasting BMSC survival and optimizing stem cell therapy for IVD degeneration.

中文翻译：

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缺氧通过激活 HIF-1α/YAP 信号通路保护大鼠骨髓间充质干细胞免受退行性椎间盘微环境中压缩诱导的细胞凋亡。

干细胞疗法为椎间盘 (IVD) 变性提供了一种有吸引力的解决方案。然而，以过度机械负荷和缺氧为特征的退化微环境仍然是外源移植干细胞长期存活的障碍。骨髓间充质干细胞 (BMSC) 是否以及如何适应恶劣的微环境尚不清楚。在本研究中，CoCl ₂和机械压缩同时用于模拟体外体外诊断IVD的缺氧和超负荷微环境。压缩通过激活线粒体凋亡途径具有促凋亡作用，而缺氧则发挥促生存作用，抵消压缩诱导的细胞凋亡。通过 chetomin 抑制缺氧诱导因子 1 亚基 α (HIF-1α) 的转录活性逆转缺氧的抗细胞凋亡作用。此外，HIF-1α 在缺氧条件下促进去磷酸化和 yes 相关蛋白 (YAP) 的激活。相反，在通过 chetomin 或 YAP 抑制剂维替泊芬抑制后，观察到 YAP 抑制和细胞凋亡增加。免疫荧光染色和共免疫沉淀分析表明，YAP 可以直接与 HIF-1α 相互作用并共定位于细胞核中。总之，我们的结果表明，缺氧通过激活 HIF-1α/YAP 信号通路保护 BMSCs 在退行性椎间盘微环境中免受压缩诱导的细胞凋亡。因此，调节 HIF-1α/YAP 信号可能为促进 BMSC 持久存活和优化干细胞治疗 IVD 退化提供新的见解。