Mechanisms of adipogenic and fibrotic degeneration of muscle

肌肉脂肪形成和纤维变性的机制

• 批准号: 10259577
• 负责人: THOMAS A. RANDO
• 金额: --
• 依托单位: VETERANS ADMIN PALO ALTO HEALTH CARE SYS
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-10-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10259577
• 关键词: Activities of Daily Living; Address; Alleles; Attention; Cells; Chronic; Clinical; Data; Development; Diphtheria Toxin; Disease; Equilibrium; Exhibits; Fatty acid glycerol esters; Fibrosis; Functional disorder; Genetic Transcription; Glycerol; Goals; Health; Homeostasis; Human; Impairment; In Vitro; Infiltration; Injury; Intervention; Investigation; Label; Lead; Lesion; Limb structure; LoxP-flanked allele; Mediating; Mediator of activation protein; Mesenchymal; Mesenchymal Stem Cells; Metabolic Diseases; Methods; MicroRNAs; Mission; Modeling; Molecular; Mouse Strains; Mus; Muscle; Muscle Cells; Muscle function; Muscular Atrophy; Obesity; Pathway interactions; Platelet-Derived Growth Factor alpha Receptor; Population; Pre-Clinical Model; Prevalence; Prevention; Process; Quality of life; Recovery of Function; Regulation; Regulatory Pathway; Role; Series; Signal Transduction; Skeletal Muscle; Skeletal muscle injury; Soldier; Source; Tamoxifen; Technology; Testing; Therapeutic; Therapeutic Intervention; Tissues; Transplantation; Traumatic injury; Veterans; Work; aged; analog; base; bioinformatics pipeline; cell behavior; clinically relevant; efficacy testing; experience; functional decline; gain of function; improved; in vivo; injured; insight; interstitial; loss of function; mouse model; muscle degeneration; muscle regeneration; muscle stiffness; novel; prevent; progenitor; programs; reduced muscle strength; repaired; response; rotator cuff injury; stem cell biology; targeted treatment; therapeutic evaluation; therapeutic target; therapeutically effective; therapy development; tool; transcription factor; transcriptome sequencing; volumetric muscle loss

Fibrotic and adipogenic infiltration are hallmarks of injured, diseased, and aged skeletal muscle. This fibrofatty degeneration (“FFD”) results not only in functional decline of skeletal muscle but also to the increased prevalence of metabolic disorders. The origins of the major cellular contributors (fibrogenic and adipogenic progenitors) of this FFD remain to be definitively identified, but recent evidence (including Preliminary Studies included herein) suggest a population of mesenchymal progenitors termed “fibroadipogenic progenitors” (FAPs) are major sources. FAPs reside in the muscle interstitium and display robust fibrogenic and adipogenic potential in vitro and in vivo following transplantation. Studies in vivo to directly test whether endogenous FAPs are responsible for fibrosis and adiposity in the setting of injury and disease have been limited by the lack of specific tools to genetically label and target FAPs. We have recently developed such tools by taking advantage of the highly specific expression of PDGFRα in FAPs among the mononucleated cells of muscle. Our Preliminary Studies using a PDGFRαCreER strain that we developed to either genetically label or specifically deplete FAPs support the hypothesis that FAPs are sources of both fibrogenic and adipogenic cells in the setting of aberrant muscle regeneration associated with FFD. In Preliminary Studies, we also identified a microRNA, miR-206, as a candidate regulator of FAP adipogenic differentiation, and a transcription factor, Runx1, as a likely target of mIR-206 in this process. We have, in addition, identified candidate microRNAs involved in the regulation of FAP fibrogenic differentiation. In the studies of this proposal, we will explore the regulation of FAP adipogenic and fibrogenic differentiation, and the essential role of FAPs in FFD in two clinically relevant models. In the studies of Aim 1, we will examine the role of the miR-206/Runx1 axis in FAP adipogenic differentiation in vitro and in fatty infiltration in glycerol-induced muscle injury in vivo. In the studies of Aim 2, we will work collaboratively with our colleague, Dr. Brian Feeley, at UCSF to explore the role of FAPs in general, and of the miR-206/Runx1 axis in particular, in the fatty infiltration that occurs in the setting of rotator cuff injury (RCI). Dr. Feeley has developed a robust murine model of RCI that exhibits the kind of fatty infiltration and muscle atrophy seen in humans. We will use a novel tamoxifen analog delivery method we have developed to allow for the depletion of FAPs only in the region of the RCI. In the studies of Aim 3, we will examine the regulation of FAP fibrogenic differentiation, again focusing on the key role of miRNAs in such cell fate decisions. We will identify functional targets of candidate miRNAs using a recently developed pull-down technology combine with RNA sequencing (LAMP- seq). Furthermore, we will address the role of FAPs in the extensive fibrosis seen in the common extremity traumatic injury experience by soldiers and treated in Veterans, volumetric muscle loss (VML). We have extensive experience with a murine model of VML, and we will examine both the development of fibrosis and interventions to prevent fibrosis based on our understanding of FAP differentiation. Through our studies of FAPs and the regulatory processes that control their differentiation to adipogenic and fibrogenic cells, we aim to understand the mechanisms that give rise to FFD and the subsequent muscle dysfunction. Our investigation will both capitalize on new experimental tools to study this population and lend insight into therapeutic strategies to prevent FFD. This will have direct relevance to Veterans who have experienced skeletal muscle injuries, injuries that have limited their functional capacity and that, to date, have little hope of functional recovery. Our goal is to develop therapeutic approaches to enhance muscle repair and prevent muscle degeneration based upon a thorough understanding of the basic stem cell biology. These goals are based upon a firm commitment to a mission to improve the health and quality of life of Veterans whose function is limited by the lack of effective therapeutic options.

纤维化和脂肪浸润是骨骼肌受伤、患病和衰老的标志。 纤维脂肪变性（“FFD”）不仅会导致骨骼肌功能下降，还会导致骨骼肌功能增加。 主要细胞因素（纤维形成和脂肪形成）的流行。 该 FFD 的祖先）仍有待明确确定，但最近的证据（包括初步研究） 包括本文）提出了称为“纤维脂肪形成祖细胞”的间充质祖细胞群 (FAP) 是 FAP 的主要来源，存在于肌肉间质中，具有强大的纤维生成和脂肪生成作用。 移植后的体外和体内研究直接测试内源性 FAP 的潜力。 在受伤和疾病的情况下导致纤维化和肥胖的因素由于缺乏 我们最近利用这一优势开发了此类工具来对 FAP 进行基因标记和定位。 肌肉单核细胞中 FAP 中 PDGFRα 的高度特异性表达。 使用我们开发的 PDGFRαCreER 菌株进行的初步研究，该菌株可进行基因标记或特异性标记 耗尽的 FAP 支持以下假设：FAP 是纤维生成细胞和脂肪生成细胞的来源 在初步研究中，我们还发现了与 FFD 相关的异常肌肉再生的情况。 microRNA，miR-206，作为 FAP 脂肪形成分化的候选调节因子和转录因子， Runx1，作为此过程中 miR-206 的可能目标，我们还确定了候选 microRNA。 参与 FAP 纤维化分化的调节。 在本提案的研究中，我们将探讨FAP脂肪形成和纤维形成的调控 在两个临床相关模型的研究中，FAP 在 FFD 中的分化和重要作用。 我们将研究 miR-206/Runx1 轴在体外和脂肪细胞中 FAP 脂肪形成分化中的作用 在目标2的研究中，我们将与我们合作研究甘油引起的体内肌肉损伤。 加州大学旧金山分校的同事 Brian Feeley 博士探索了 FAP 的一般作用，以及 miR-206/Runx1 轴在 Feeley 博士发现，在肩袖损伤 (RCI) 时发生的脂肪浸润尤其重要。 一个强大的 RCI 小鼠模型，表现出人类中所见的脂肪浸润和肌肉萎缩。 将使用我们开发的新型他莫昔芬类似物递送方法，仅在 在目标 3 的研究中，我们将检查 FAP 纤维形成分化的调节， 我们将再次关注 miRNA 在此类细胞命运决定中的关键作用。 候选 miRNA 使用最近开发的 Pull-down 技术结合 RNA 测序（LAMP- 此外，我们将讨论 FAP 在常见四肢广泛纤维化中的作用。 士兵的创伤经历和退伍军人的治疗，体积肌肉损失（VML）。 我们在 VML 小鼠模型方面拥有丰富的经验，我们将检查纤维化的发展和 基于我们对 FAP 分化的理解，预防纤维化的干预措施。 通过我们对 FAP 和控制其分化成脂肪的调控过程的研究 和纤维形成细胞，我们的目标是了解引起 FFD 和随后的肌肉的机制 我们的调查将利用新的实验工具来研究这一人群并提供帮助。 深入了解预防 FFD 的治疗策略这将与患有 FFD 的退伍军人直接相关。 经历过骨骼肌损伤，这些损伤限制了他们的功能能力，并且迄今为止， 我们的目标是开发增强肌肉修复和恢复功能的治疗方法。 基于对基本干细胞生物学的透彻理解，预防肌肉退化。 目标基于对改善退伍军人健康和生活质量使命的坚定承诺 由于缺乏有效的治疗选择，其功能受到限制。