Objective

Meniscus injury and the hypoxia-inducible factor (HIF) pathway are independently linked to osteoarthritis pathogenesis, but the role of the meniscus HIF pathway remains unclear. We sought to identify and evaluate HIF pathway response in normal and osteoarthritic meniscus and to examine the effects of Epas1 (HIF-2α) insufficiency in mice on early osteoarthritis development.

Methods

Normal and osteoarthritic human meniscus specimens were obtained and used for immunohistochemical evaluation and cell culture studies for the HIF pathway. Meniscus cells were treated with pro-inflammatory stimuli, including interleukins (IL)-1β, IL-6, transforming growth factor (TGF)-α, and fibronectin fragments (FnF). Target genes were also evaluated with HIF-1α and HIF-2α (Epas1) overexpression and knockdown. Wild-type (n = 36) and Epas1^+/− (n = 30) heterozygous mice underwent destabilization of the medial meniscus (DMM) surgery and were evaluated at 2 and 4 weeks postoperatively for osteoarthritis development using histology.

Results

HIF-1α and HIF-2α immunostaining and gene expression did not differ between normal and osteoarthritic meniscus. While pro-inflammatory stimulation significantly increased both catabolic and anabolic gene expression in the meniscus, HIF-1α and Epas1 expression levels were not significantly altered. Epas1 overexpression significantly increased Col2a1 expression. Both wild-type and Epas1^+/− mice developed osteoarthritis following DMM surgery. There were no significant differences between genotypes at either time point.

Conclusion

The HIF pathway is likely not responsible for osteoarthritic changes in the human meniscus. Additionally, Epas1 insufficiency does not protect against osteoarthritis development in the mouse at early time points after DMM surgery. The HIF pathway may be more important for protection against catabolic stress.

中文翻译：

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缺氧诱导因子途径在正常和骨关节炎半月板以及内侧半月板不稳定后的小鼠中的作用。

客观的

半月板损伤和缺氧诱导因子 (HIF) 通路与骨关节炎发病机制独立相关，但半月板 HIF 通路的作用仍不清楚。我们试图识别和评估正常和骨关节炎半月板中的 HIF 通路反应，并检查小鼠 Epas1 (HIF-2α) 不足对早期骨关节炎发展的影响。

方法

获得正常和骨关节炎人类半月板标本，并用于 HIF 途径的免疫组织化学评估和细胞培养研究。半月板细胞用促炎刺激物处理，包括白细胞介素 (IL)-1β、IL-6、转化生长因子 (TGF)-α 和纤连蛋白片段 (FnF)。还用 HIF-1α 和 HIF-2α (Epas1) 过表达和敲低来评估靶基因。野生型 ( n = 36) 和 Epas1 ^+/- ( n = 30) 杂合小鼠接受内侧半月板 (DMM) 手术的不稳定，并在术后 2 周和 4 周使用组织学评估骨关节炎的发展。

结果

HIF-1α 和 HIF-2α 免疫染色和基因表达在正常和骨关节炎半月板之间没有差异。虽然促炎刺激显着增加了半月板中分解代谢和合成代谢基因的表达，但 HIF-1α 和 Epas1 的表达水平没有显着改变。Epas1 过表达显着增加了 Col2a1 的表达。野生型和 Epas1 ^+/-小鼠在 DMM 手术后均出现骨关节炎。在任一时间点，基因型之间没有显着差异。

结论

HIF 通路可能与人类半月板的骨关节炎变化无关。此外，在 DMM 手术后的早期时间点，Epas1 不足并不能防止小鼠发生骨关节炎。HIF 通路可能对防止分解代谢压力更重要。