Conversion of pre-adipose cells into muscle cells

描述(申请人提供)：肌营养不良症表现为肌肉纤维的进行性丧失和肌肉组织再生的最终失败。基于细胞的治疗可能会恢复肌肉组织，而脂肪组织可能会为这种治疗提供一个简单的细胞来源。我们一直在研究BMP或转化生长因子-β信号重定向前脂肪细胞分化的机制，发现前脂肪细胞和初级脂肪基质细胞移植到免疫缺陷小鼠后可以形成肌样组织。我们建议验证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能够促进组织修复的功能肌肉的假设，以及BMP信号调节这种分化。Smads是转化生长因子-β和骨形态发生蛋白信号的下游效应者，是间充质分化的细胞内源性调节因子，提示对单个Smads激活水平的调控将深刻影响前脂肪细胞向肌肉细胞的分化。在目标1中，我们将对3T3-F442a细胞或人脂肪基质细胞产生的肌样细胞进行鉴定，并评估它们是来自直接转化还是来自细胞与宿主肌纤维的融合。在目标2中，我们将确定移植的成脂细胞或脂肪细胞是否有助于dystrophin缺陷裸鼠的肌肉修复，并确定植入是否改善肌肉修复。我们还将使用遗传学方法来评估内源性(前)脂肪细胞是否能够在损伤后分化为肌细胞，并有助于肌肉(重新)的生成。在目标3和未来的研究中，我们将研究BMP信号的效应者Smad1和Smad5，以及转化生长因子-β和肌肉生长抑素信号的效应者Smad3作为成肌细胞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信号来操纵肌源性分化。我们的研究有望为自体前脂肪细胞和脂肪基质细胞用于肌肉再生和修复提供基础，这是一种容易获得的细胞来源。与公共卫生相关。肌肉营养不良或肌肉修复缺陷的患者将受益于一种疗法，即注射的细胞将转化为肌肉组织。我们最近发现，正在成为脂肪细胞的细胞可以被重新定向为肌肉细胞。我们建议利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肌肉损伤的修复和抵消与肌肉营养不良相关的缺陷。这项研究可以为在治疗中使用自己的脂肪来改善肌肉修复和再生提供依据。

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.