Department of Ophthalmology, University of Rochester, Rochester, New York, United States.
Center for Visual Science, University of Rochester, Rochester, New York, United States.
Invest Ophthalmol Vis Sci. 2022 Apr 1;63(4):2. doi: 10.1167/iovs.63.4.2.
Fibrosis caused by corneal wounding can lead to scar formation, impairing vision. Although preventing fibroblast-to-myofibroblast differentiation has therapeutic potential, effective mechanisms for doing so remain elusive. Recent work shows that mitochondria contribute to differentiation in several tissues. Here, we tested the hypothesis that mitochondrial dynamics, and specifically fission, are key for transforming growth factor (TGF)-β1-induced corneal myofibroblast differentiation.
Mitochondrial fission was inhibited pharmacologically in cultured primary cat corneal fibroblasts. We measured its impact on molecular markers of myofibroblast differentiation and assessed changes in mitochondrial morphology through fluorescence imaging. The phosphorylation status of established regulatory proteins, both of myofibroblast differentiation and mitochondrial fission, was assessed by Western analysis.
Pharmacological inhibition of mitochondrial fission suppressed TGF-β1-induced increases in alpha-smooth muscle actin, collagen 1, and fibronectin expression, and prevented phosphorylation of c-Jun N-terminal kinase (JNK), but not small mothers against decapentaplegic 3, p38 mitogen-activated protein kinase (p38), extracellular signal-regulated kinase 1 (ERK1), or protein kinase B (AKT). TGF-β1 increased phosphorylation of dynamin-related protein 1 (DRP1), a mitochondrial fission regulator, and caused fragmentation of the mitochondrial network. Although inhibition of JNK, ERK1, or AKT prevented phosphorylation of DRP1, none sufficed to independently suppress TGF-β1-induced fragmentation.
Mitochondrial dynamics play a key role in early corneal fibrogenesis, acting together with profibrotic signaling. This is consistent with mitochondria's role as signaling hubs that coordinate metabolic decision-making. This suggests a feed-forward cascade through which mitochondria, at least in part through fission, reinforce noncanonical TGF-β1 signaling to attain corneal myofibroblast differentiation.
角膜创伤引起的纤维化可导致瘢痕形成，损害视力。虽然阻止成纤维细胞向肌成纤维细胞分化具有治疗潜力，但有效的方法仍难以捉摸。最近的工作表明，线粒体在几种组织的分化中起作用。在这里，我们检验了这样一个假设，即线粒体动力学，特别是分裂，是转化生长因子（TGF）-β1诱导角膜肌成纤维细胞分化的关键。
在培养的原代猫角膜成纤维细胞中用药物抑制线粒体分裂。我们测量了它对肌成纤维细胞分化的分子标记的影响，并通过荧光成像评估了线粒体形态的变化。通过 Western 分析评估了已建立的调节蛋白（包括肌成纤维细胞分化和线粒体分裂）的磷酸化状态。
线粒体分裂的药理学抑制抑制了 TGF-β1诱导的α-平滑肌肌动蛋白、胶原蛋白 1 和纤维连接蛋白表达的增加，并阻止了 c-Jun N 端激酶（JNK）的磷酸化，但不是小的母体对抗 decapentaplegic 3、p38 丝裂原活化蛋白激酶（p38）、细胞外信号调节激酶 1（ERK1）或蛋白激酶 B（AKT）。TGF-β1增加了线粒体分裂调节因子 dynamin-related protein 1（DRP1）的磷酸化，并导致线粒体网络的碎片化。尽管抑制 JNK、ERK1 或 AKT 可阻止 DRP1 的磷酸化，但没有一种能独立抑制 TGF-β1 诱导的分裂。
线粒体动力学在早期角膜纤维化中起关键作用，与促纤维化信号一起作用。这与线粒体作为协调代谢决策的信号枢纽的作用一致。这表明了一个正反馈级联，通过该级联，线粒体至少部分通过分裂来增强非典型 TGF-β1 信号以获得角膜肌成纤维细胞分化。
