The role of LOXL1 in fibrosis via mediating ECM crosslinking and stabilization is well established; however, the role of hepatic stellate cells (HSCs)-specific LOXL1 in the development of fibrosis remains unknown. We generated HSCs-specific Loxl1-depleted mice (Loxl1^Gfap-cre mice) to investigate the HSCs-specific contribution of LOXL1 in the pathogenesis of fibrosis. Loxl1^fl/fl mice were used as the control. Furthermore, we used RNA sequencing to explore the underlying changes in the transcriptome. Results of the sirius red staining, type I collagen immunolabeling, and hydroxyproline content analysis, coupled with the reduced expression of profibrogenic genes revealed that Loxl1^Gfap-cre mice with CCl₄-induced fibrosis exhibited decreased hepatic fibrosis. In addition, Loxl1^Gfap-cre mice exhibited reduced macrophage tissue infiltration by CD68-positive cells and decreased expression of inflammatory genes compared with the controls. RNA sequencing identified integrin α8 (ITGA8) as a key modulator of LOXL1-mediated liver fibrosis. Functional analyses showed that siRNA silencing of Itga8 in cultured fibroblasts led to a decline in the LOXL1 expression and inhibition of fibroblast activation. Mechanistic analyses indicated that LOXL1 activated the FAK/PI3K/AKT/HIF1a signaling pathway, and the addition of inhibitors of FAK or PI3K reversed these results via downregulation of LOXL1. Furthermore, HIF1a directly interacted with LOXL1 and upregulated its expression, indicating that LOXL1 can positively self-regulate by forming a positive feedback loop with the FAK/PI3K/AKT/HIF1a pathway. We demonstrated that HSCs-specific Loxl1 deficiency prevented fibrosis, inflammation and that ITGA8/FAK/PI3K/AKT/HIF1a was essential for the function and expression of LOXL1. Knowledge of this approach can provide novel mechanisms and targets to treat fibrosis in the future.

中文翻译：

---

选择性消耗肝星状细胞特异性 LOXL1 可缓解肝纤维化

LOXL1 通过介导 ECM 交联和稳定在纤维化中的作用已得到充分证实；然而，肝星状细胞 (HSC) 特异性 LOXL1 在纤维化发展中的作用仍然未知。我们生成了 HSC 特异性Loxl1耗竭小鼠（Loxl1 ^Gfap-cre小鼠）以研究 LOXL1 在纤维化发病机制中的 HSC 特异性贡献。Loxl1 ^fl/fl小鼠用作对照。此外，我们使用 RNA 测序来探索转录组的潜在变化。天狼星红染色、I 型胶原免疫标记和羟脯氨酸含量分析的结果，再加上促^纤维化基因的表达降低表明Loxl1 ^Gfap-creCCl ₄诱导的纤维化小鼠表现出肝纤维化减少。此外，与对照组相比，Loxl1 ^Gfap-cre小鼠表现出 CD68 阳性细胞对巨噬细胞组织的浸润减少，炎症基因的表达减少。RNA 测序确定整合素 α8 (ITGA8) 是 LOXL1 介导的肝纤维化的关键调节剂。功能分析表明，Itga8 的siRNA 沉默在培养的成纤维细胞中导致 LOXL1 表达的下降和成纤维细胞活化的抑制。机制分析表明，LOXL1 激活了 FAK/PI3K/AKT/HIF1a 信号通路，添加 FAK 或 PI3K 抑制剂通过下调 LOXL1 逆转了这些结果。此外，HIF1a 直接与 LOXL1 相互作用并上调其表达，表明 LOXL1 可以通过与 FAK/PI3K/AKT/HIF1a 通路形成正反馈回路来积极自我调节。我们证明 HSC 特异性Loxl1缺陷可防止纤维化、炎症，并且 ITGA8/FAK/PI3K/AKT/HIF1a 对 LOXL1 的功能和表达至关重要。这种方法的知识可以为未来治疗纤维化提供新的机制和目标。