The 4D nucleome of muscle regeneration in ischemia-induced tissue damage and repair

摘要： 由血流限制引起的局部缺血通常导致严重的组织损伤。严重肢体缺血（CLI） 是一种严重的疾病，其中外周动脉疾病（PAD）导致不可逆的肢体肌肉损伤。关于 40%的CLI患者在诊断后一年接受截肢，50%在五年后死亡。电流 治疗选择集中于改善肢体灌注，但这些治疗选择通常不能防止疾病进展， 这表明迫切需要更深入地理解调节人体肌肉的基本机制 再生以及它们如何被缺血性损伤破坏。从长远来看，这一信息可能导致 不依赖于肢体灌注的用于肢体挽救的新的再生治疗策略。最近的研究 提示骨骼肌再生失败是决定CLI中组织损失与修复的关键。 成功的肌肉再生需要协调的激活，增殖和分化的肌肉 干细胞（MuSCs，也称为卫星细胞），其通常是静止的。在我们初步分析 来自一个代表性CLI患者的MuSCs，我们发现对MuSCs重要的基因的转录 在缺血时再生失调，这些变化与3D重排有关 染色质组织。这些发现支持CLI在正常动态过程中发生故障的假设。 3D染色质结构的重组，其协调了MuSCs的再生。总体目标 本研究的目的是确定染色质结构（4D核组，4DN）的时空变化。 通常与再生性人MuSCs相关，并了解其功能性后果 CLI中肌肉损伤机制的缺陷。

ABSTRACT: Ischemia, caused by restriction of blood flow, often results in severe tissue damage. Critical limb ischemia (CLI) is a serious condition in which peripheral artery disease (PAD) leads to irreversible limb muscle damage. About 40% of CLI patients undergo limb amputation one year after diagnosis, and 50% die after five years. Current treatment options focus on improving limb perfusion but these often fail to prevent disease progression, pointing to a critical need for a deeper understanding of the basic mechanisms regulating human muscle regeneration and how they are disrupted by ischemic damage. In the long-term, this information may lead to new regenerative treatment strategies for limb salvage that are independent of limb perfusion. Recent studies suggest that failure of skeletal muscle regeneration is key to determining tissue loss in CLI versus repair. Successful muscle regeneration requires the orchestrated activation, proliferation and differentiation of muscle stem cells (MuSCs, also known as satellite cells) that are normally quiescent. In our preliminary analysis of MuSCs from one representative CLI patient, we found that the transcription of genes important for MuSC regeneration are dysregulated in ischemia, and that these changes are associated with rearrangements in 3D chromatin organization. These finding support the hypothesis that CLI involves a failure in the normal dynamic reorganization of 3D chromatin structure that orchestrates the regeneration of MuSCs. The overall objectives of this study are to identify the spatial-temporal changes of chromatin organization (the 4D nucleome, 4DN) normally associated with regenerative human MuSCs, and to understand the functional consequences of defects in this mechanism for muscle damage in CLI.