Conversion of pre-adipose cells into muscle cells

描述（由申请人提供）：肌营养不良症显示肌纤维逐渐丧失，最终无法再生肌肉组织。基于细胞的疗法可以恢复肌肉组织，而脂肪组织可以为这种疗法提供简单的细胞来源。我们一直在研究BMP或TGF-β信号传导可以重定向前脂肪细胞分化的机制，发现前脂肪细胞和原代脂肪基质细胞在移植到免疫缺陷小鼠体内时可以形成肌肉样组织。我们建议测试以下假设：前脂肪细胞和脂肪基质细胞可以改变其分化以在体内产生功能性肌肉，从而有助于组织修复，并且 BMP 信号传导调节这种分化。 Smads 是 TGF-β 和 BMP 信号传导的下游效应器，并作为间充质分化的细胞内在调节因子，这表明控制单个 Smads 的激活水平将深刻影响前脂肪细胞向肌肉细胞的分化。在目标 1 中，我们将表征由 3T3-F442A 细胞或人脂肪基质细胞产生的肌肉样细胞，并评估它们是否来自直接转化或与宿主肌纤维的细胞融合。在目标 2 中，我们将确定移植的脂肪形成细胞或脂肪细胞是否有助于肌营养不良蛋白缺陷裸鼠的肌肉修复，并确定植入是否改善肌肉修复。我们还将使用遗传方法来评估内源性（前）脂肪细胞是否可以响应损伤而分化为肌细胞并有助于肌肉（再生）生成。在目标 3 和未来的研究中，我们将研究 Smad1 和 Smad5（BMP 信号传导的效应器）以及 Smad3（TGF-β 和肌肉生长抑制素信号传导的效应器）作为肌原性分化的细胞内在调节因子的作用。这些实验应该向我们展示如何通过修改 Smad 信号传导来操纵生肌分化。我们的研究有望为使用自体前脂肪细胞和脂肪基质细胞（一种现成的细胞来源）进行肌肉再生和修复提供基础。公共卫生相关性。 患有肌营养不良或肌肉修复缺陷的患者将受益于注射细胞转化为肌肉组织的疗法。我们最近发现正在变成脂肪细胞的细胞可以被重新定向为肌肉细胞。我们建议使用小鼠模型来表征和增强这些细胞成为肌肉细胞的潜力，并探索它们如何帮助修复肌肉损伤并抵消与肌营养不良症相关的缺陷。这项研究可以为利用自身脂肪来改善肌肉修复和再生的治疗提供基础。

DESCRIPTION (provided by applicant): Muscular dystrophies show a progressive loss of muscle fibers and ultimate failure to regenerate muscle tissue. Cell-based therapy may restore muscle tissue, and adipose tissue may provide a facile source of cells for such therapy. We have been studying the mechanisms through which BMP or TGF-beta signaling can redirect pre-adipocyte differentiation and found that pre-adipocytes and primary adipose stromal cells can form muscle-like tissue when transplanted into immunodeficient mice. We propose to test the hypothesis that preadipocytes and adipose stromal cells can alter their differentiation to generate functional muscle in vivo, capable of contributing to tissue repair, and that BMP signaling regulates this differentiation. Smads are downstream effectors of signaling by TGF- beta and BMP and serve as cell-intrinsic regulators of mesenchymal differentiation, suggesting that manipulations of the activation levels of individual Smads will profoundly affect the differentiation of preadipocytes into muscle cells. In Aim 1 we will characterize the muscle-like cells generated from 3T3-F442A cells or human adipose stromal cells, and evaluate whether they arise from direct conversion or cell fusion with host myofibers. In Aim 2 we will determine whether transplanted adipogenic cells or adipocytes contribute to muscle repair in dystrophin-deficient nude mice, and determine whether engraftment improves muscle repair. We will also use a genetic approach to evaluate if endogenous (pre)adipocytes can differentiate into myocytes in response to injury and contribute to muscle (re)generation. In Aim 3 and future studies we will examine the role of Smad1 and Smad5, effectors of BMP signaling, and Smad3, effector of TGF-beta and myostatin signaling, as cell-intrinsic regulators of myogenic differentiation. These experiments should show us how to manipulate the myogenic differentiation by modifying Smad signaling. Our studies will hopefully provide the basis for the use of autologous preadipocytes and adipose stromal cells, a readily available cell source, for muscle regeneration and repair. PUBLIC HEALTH RELEVANCE. Patients with muscular dystrophy or defects in muscle repair would benefit from a therapy whereby injected cells would convert into muscle tissue. We recently found that cells that are becoming fat cells can be redirected to become muscle cells. We propose to characterize and to enhance the potential of these cells to become muscle cells, and to explore how they can help in the repair of muscle injury and to counteract the defects associated with muscular dystrophy, using mouse models. This research could provide a basis for the use of one's own fat in therapy to improve muscle repair and regeneration.