Fibroadipogenic progenitor cells as drivers of angiogenesis during muscle regeneration

摘要 骨骼肌占身体质量的近一半，易受创伤性损伤，特别是 四肢受损的肌肉质量和功能必须迅速恢复，以尽量减少身体变形， 预防长期残疾。此外，不良的结果会带来重大的情感和经济负担 受影响的个人及其家庭。NICHD的理想目标是提高再生能力 通过使用新兴技术来激活人体自身的生长途径和过程，下 在大多数情况下，受损的肌肉通过协调的多细胞反应有效地再生， 涉及肌肉干细胞（卫星细胞，SC）、内皮细胞（EC）和成纤维细胞或成纤维脂肪细胞， 前体细胞（FAP）以及其他驻留和浸润细胞类型。然而，在组织损失超过 临界阈值（肌肉体积损失，VML），组织再生不会发生， 功能恢复。阈下、阈下和阈下之间区别的分子和细胞机制， 再生性伤口与非再生性VML尚未得到充分理解， 翻译干预的发展。一种新的损伤和再生的穿刺活检模型， PI使用小鼠臀大肌的实验室强调了FAP，EC和 SC成功实现肌肉再生。一个关键的观察结果是，如果去除局部FAP， 并且肌生成不能发生，使得阈下损伤反而类似于VML。FAP是否会影响这一点 直接作用于EC、肌原细胞或两者的关系尚不清楚。因此，本研究项目 建议：1）确认FAP在允许亚临界VML损伤愈合方面的要求; 2）测试 一种候选分子，骨膜蛋白，拯救缺乏微血管和肌纤维再生的伤口的能力， FAP; 3）确定骨膜蛋白是否直接向EC、肌源性细胞或两者发出信号;以及4）进行无偏定量分析。 蛋白质组学筛选由FAP直接分泌或在EC中诱导的额外信号分子， FAP可以促进完整肌肉的再生。这些实验将利用 该团队在微血管成像、肌肉再生、FAPs生物学和生物材料方面的集体专业知识 识别，表征和功能测试区分肌肉和肌肉之间的关键细胞和分子因子， 成功治愈的伤和不能治愈的伤如果成功，该研究项目将确定 这些分子和方法有可能被转化为旨在改善临床症状的疗法， 结果为残疾人，从而解决了一个关键的未满足的需求，在基础和应用肌肉 生物学

ABSTRACT Skeletal muscle comprises nearly half of body mass and is subject to traumatic injuries, particularly of the extremities. Damaged muscle mass and function must be restored promptly to minimize physical distortion and prevent long-term disabilities. Furthermore, poor outcomes impose significant emotional and financial burdens on affected individuals and their families. An aspirational goal of the NICHD is to advance the ability to regenerate human limbs by using emerging technologies to activate the body’s own growth pathways and processes. Under most circumstances damaged muscle is efficiently regenerated through a coordinated multicellular response involving muscle stem cells (satellite cells, SCs), endothelial cells (ECs), and fibroblasts or fibroadipogenic precursor cells (FAPs) as well as other resident and infiltrating cell types. However, after the loss of tissue over a critical threshold (volumetric muscle loss, VML), tissue regeneration does not occur and neither mass nor function are regained. The molecular and cellular mechanisms underlying the distinction between subthreshold, regenerating wounds vs. nonregenerating VML are not yet sufficiently understood, posing a critical roadblock to development of translational interventions. A novel punch biopsy model of injury and regeneration developed in the PI’s laboratory using the mouse gluteus maximus muscle highlights the sequential activity of FAPs, ECs, and SCs in successful muscle regeneration. A key observation is that if local FAPs are removed, both angiogenesis and myogenesis fail to occur, making the subthreshold injury instead resemble VML. Whether FAPs effect this relationship by direct actions on ECs, myogenic cells, or both is unknown. Therefore, this research project proposes to: 1) confirm the requirement for FAPs in permitting healing of a subcritical VML injury; 2) test the ability of a candidate molecule, periostin, to rescue microvascular and myofiber regeneration in wounds lacking FAPs; 3) determine whether periostin signals directly to ECs, myogenic cells, or both; and 4) perform an unbiased proteomic screen for additional signaling molecules either secreted directly by FAPs or induced in ECs or myogenic cells by FAPs that may promote the regeneration of intact muscle. These experiments will leverage the team's collective expertise in microvascular imaging, muscle regeneration, FAPs biology, and biomaterials to identify, characterize, and functionally test key cellular and molecular factors differentiating between muscle injuries which heal successfully and those which cannot. If successful, this research project will identify molecules and methods which have the potential to be translated into therapies designed to improve clinical outcomes for disabled individuals, thereby addressing a key unmet need in both basic and applied muscle biology.