Abstract 246: Transdifferentiation of Human Fibroblasts to Endothelial Cells: Role of Innate Immunity
Abstract 246: Transdifferentiation of Human Fibroblasts to Endothelial Cells: Role of Innate Immunity
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发表时间：
2013-08
影响因子：
20.1
通讯作者：
N. Sayed;W. Wong;J. Cooke
中科院分区：
文献类型：
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作者：
N. Sayed;W. Wong;J. Cooke
细胞的命运是不稳定的，在实验中可能会被介导细胞谱系的主调控因子的强制表达所改变。这种核重编程是利用病毒载体编码转录因子实现的。我们最近发现，病毒载体不仅仅是转录因子的被动载体，因为它们积极参与核重编程到多能性的过程。病毒载体通过激活先天免疫，导致表观遗传修饰因子表达的全局变化，有利于染色质开放状态（Cell, 151, 2012）。基于先天免疫激活增加表观遗传可塑性的认识，我们假设toll样受体3 （TLR3）的小分子激活剂，连同驱动EC规范的外部微环境线索，可能足以诱导成纤维细胞转分化为EC （iECs）。本研究表明，TLR3激动剂Poly I:C与外源性EC生长因子结合，可将人成纤维细胞转化为EC（在缺乏病毒载体或转录因子的情况下）。这些iec在免疫组织化学、遗传和功能分析方面与HMVEC相当，包括形成毛细血管样结构和纳入乙酰化ldl的能力。此外，与亲代成纤维细胞相比，iECs可显著改善小鼠缺血后肢的肢体灌注和新生血管形成。最后，通过基因敲低研究，我们发现人类成纤维细胞向内皮细胞的有效转分化需要先天免疫激活。这项研究表明，先天免疫信号的操纵可能通常用于改变细胞命运。我们的观察结果提出了一个问题，即表观遗传可塑性和细胞命运流动性是否普遍参与对病原体的免疫防御。由于类似的信号通路被损伤相关的分子模式激活，先天免疫诱导的表观遗传可塑性可能在伤口愈合和再生过程中的转分化中发挥了重要作用。最后，本研究是开发治疗性体内转分化小分子策略的第一步。
Cell fate is fluid, and may be altered experimentally by the forced expression of master regulators mediating cell lineage. Such nuclear reprogramming has been achieved using viral vectors encoding transcription factors. We recently discovered that the viral vectors are more than passive vehicles for transcription factors, as they participate actively in the process of nuclear reprogramming to pluripotency. Viral vectors, by activating innate immunity, cause global changes in the expression of epigenetic modifiers, favoring an open chromatin state (Cell, 151 2012). Based on the recognition that activation of innate immunity increases epigenetic plasticity, we hypothesized that small molecule activators of toll-like receptor 3 (TLR3), together with external microenvironmental cues that drive EC specification, might be sufficient to induce transdifferentiation of fibroblasts into ECs (iECs). Here we show that TLR3 agonist Poly I:C, combined with exogenous EC growth factors, transdifferentiated human fibroblasts into ECs (in the absence of viral vectors or transcription factors). These iECs were comparable to HMVEC in immunohistochemical, genetic and functional assays, including the ability to form capillary-like structures and to incorporate acetylated-LDL. Furthermore, iECs significantly improved limb perfusion and neovascularization in the murine ischemic hindlimb compared to parental fibroblasts. Finally, using genetic knockdown studies, we find that the effective transdifferentiation of human fibroblasts to endothelial cells requires innate immune activation. This study suggests that manipulation of innate immune signaling may be generally used to modify cell fate. Our observations raise the question as to whether epigenetic plasticity and cell fate fluidity generally participate in the immune defense against pathogens. Because similar signaling pathways are activated by damage associated molecular patterns, epigenetic plasticity induced by innate immunity may play a fundamental role in transdifferentiation during wound healing and regeneration. Finally, this study is a first step toward development of a small molecule strategy for therapeutic transdifferentiation in vivo.