BACKGROUND AIMS The liver has a remarkable capacity to regenerate, which is sustained by the ability of hepatocytes to act as facultative stem cells that, while normally quiescent, re-enter the cell cycle after injury. Growth factor signaling is indispensable in rodents, whereas Wnt/β-catenin is not required for effective tissue repair. However, the molecular networks that control human liver regeneration remain unclear. METHODS Organotypic 3D spheroid cultures of primary human or murine hepatocytes were used to identify the signaling network underlying cell cycle re-entry. Furthermore, we performed chemogenomic screening of a library enriched for epigenetic regulators and modulators of immune function to determine the importance of epigenomic control for human hepatocyte regeneration. RESULTS Our results showed that, unlike in rodents, activation of Wnt/β-catenin signaling is the major mitogenic cue for adult primary human hepatocytes. Furthermore, we identified TGFβ inhibition and inflammatory signaling via NF-κB as essential steps for the quiescent-to-regenerative switch that allows Wnt/β-catenin-induced proliferation of human cells. In contrast, growth factors, but not Wnt/β-catenin signaling, triggered hyperplasia in murine hepatocytes. High-throughput screening in a human model confirmed the relevance of NFκB and revealed the critical roles of polycomb repressive complex 2 (PRC2), as well as of the bromodomain families I, II, and IV. CONCLUSIONS This study revealed a network of NFκB, TGFβ, and Wnt/β-catenin that controls human hepatocyte regeneration in the absence of exogenous growth factors, identified novel regulators of hepatocyte proliferation, and highlighted the potential of organotypic culture systems for chemogenomic interrogation of complex physiological processes.

中文翻译：

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Wnt/β-连环蛋白和 NFκB 信号协同作用，触发成人原代肝细胞的无生长因子再生。

背景目的肝脏具有显着的再生能力，这是由肝细胞充当兼性干细胞的能力所维持的，兼性干细胞虽然通常处于静止状态，但在损伤后重新进入细胞周期。生长因子信号传导在啮齿动物中是不可或缺的，而 Wnt/β-catenin 并不是有效组织修复所必需的。然而，控制人类肝脏再生的分子网络仍不清楚。方法 使用原代人或鼠肝细胞的器官型 3D 球体培养物来识别细胞周期重新进入的信号网络。此外，我们对富含表观遗传调节剂和免疫功能调节剂的文库进行了化学基因组筛选，以确定表观基因组控制对人类肝细胞再生的重要性。结果我们的结果表明，与啮齿类动物不同，Wnt/β-连环蛋白信号传导的激活是成年原代人肝细胞的主要有丝分裂线索。此外，我们发现 TGFβ 抑制和通过 NF-κB 的炎症信号传导是静止至再生转换的必要步骤，从而允许 Wnt/β-连环蛋白诱导人类细胞增殖。相比之下，生长因子而非 Wnt/β-连环蛋白信号传导引发了小鼠肝细胞的增生。人类模型中的高通量筛选证实了 NFκB 的相关性，并揭示了多梳抑制复合物 2 (PRC2) 以及溴结构域家族 I、II 和 IV 的关键作用。结论 这项研究揭示了在没有外源生长因子的情况下控制人肝细胞再生的 NFκB、TGFβ 和 Wnt/β-catenin 网络，确定了肝细胞增殖的新调节因子，并强调了器官型培养系统在复杂的化学基因组学研究中的潜力。生理过程。