Mechanisms of functional skeletal muscle repair: critical role of matrix associated IL-33

摘要 骨骼肌在急性损伤后具有固有的再生能力。众所周知，时空 应答免疫细胞群体的动态是再生过程的关键决定因素。 具体地说，骨骼肌的免疫应答需要从I型免疫应答到II型免疫应答的适当定时转换。 肌肉损伤后的再生，这种自我再生能力是失去后，临界大小的体积 肌肉损失（VML）事件，如创伤或肿瘤切除。我们最近发现一种脱细胞生物支架 完全由细胞外基质（ECM）组成的细胞因子可以促进巨噬细胞表型转变， 下游部位适当的功能性组织沉积和肌生成作为体积肌的治疗 在临床前动物模型和13名人类患者中的损失。我们目前的目标是获得可翻译的 对急性创伤后正常骨骼肌再生背后的免疫生物学的机制见解 损伤和存在ECM生物支架的情况下，其广泛目的是开发治疗剂， 引导免疫细胞促进VML后的建设性功能重塑。拟议的研究将 研究新鉴定的ECM成分白细胞介素-33（IL-33）的能力和必要性， 影响骨骼肌损伤后的重塑。IL-33通常存在于基质细胞的细胞核中， 显示是骨骼肌、心肌、肺上皮和皮肤修复的有效介质， 涉及表达IL-33受体ST 2的免疫细胞的明确机制。的主题 本发明基于我们的发现，即IL-33通过包封稳定地整合到ECM中 在基质结合的纳米囊泡（MBV）内，从而保护IL-33免于快速氧化。以下ECM 当MBV降解时，MBV从基质中释放，被免疫细胞吸收，其中IL-33激活巨噬细胞 通过非经典ST 2依赖途径向促重塑表型转化。发现IL-33作为一种 ECM-MBV的组成部分代表不同的治疗靶点和组织标记物 重塑此外，我们的实验设计将允许第一次深入的分子表征， 由ST 2-非依赖性IL-33通路调节的基因和信号通路， 我们对ECM促进功能性重塑反应的分子机制的理解。 单独地，ECM疗法的使用（作为目前在I期临床试验中测试的水凝胶 用于心脏修复）或作为生物支架片（最近在13名患者中用作VML的治疗 队列研究）现在可以从一个新的角度进行研究，并将有助于指导下一代的设计 产品、诊断和治疗应用。

ABSTRACT Skeletal muscle is inherently regenerative following acute injury. It is well established that the spatiotemporal dynamics of the responding immune cell populations are critical determinants of the regenerative process. Specifically, an appropriately timed switch from a type-I to a type-II immune response is required for skeletal muscle regeneration following injury, and this self-regenerative capacity is lost after a critical size volumetric muscle loss (VML) event such as trauma or tumor excision. We recently showed that an acellular biologic scaffold composed entirely of extracellular matrix (ECM) can facilitate a macrophage phenotype transition that leads to downstream site-appropriate functional tissue deposition and myogenesis as a treatment for volumetric muscle loss in preclinical animal models and in 13 human patients. Our current objective is to gain translatable mechanistic insights into the immunobiology behind both normal skeletal muscle regeneration following acute injury and in the presence of an ECM bioscaffold with the broad aim of developing therapeutics that enable and direct immune cells to facilitate constructive, functional remodeling after VML. The proposed studies will investigate the ability and necessity of a newly identified component of the ECM, the interleukin-33 (IL-33), to influence remodeling after skeletal muscle injury. Typically found in the nucleus of stromal cells, IL-33 has been shown to be a potent mediator of skeletal muscle, cardiac muscle, lung epithelium, and dermal repair via poorly defined mechanisms involving immune cells expressing the IL-33 receptor, ST2. The subject matter of the present proposal is based upon our discovery that IL-33 is stably integrated into the ECM via encapsulation within matrix bound nanovesicles (MBV) thereby protecting IL-33 from rapid oxidation. Following ECM degradation, MBV are released from the matrix, taken up by immune cells wherein IL-33 activates macrophages towards a pro-remodeling phenotype via a non-canonical ST2-indendent pathway. The discovery of IL-33 as an integral component of ECM-MBV represents a distinct therapeutic target and marker of tissue remodeling. Furthermore, our experimental design will allow for the first in-depth molecular characterization of the genes and signaling pathways regulated by the ST2-independent IL-33 pathway and will greatly advance our understanding of the molecular mechanisms by which ECM facilitates the functional remodeling response. Separately, the use of ECM therapies (either as a hydrogel as is presently being tested in a Phase I clinical trial by Ventrix for cardiac repair) or as a bioscaffold sheet (recently used as a treatment for VML in a 13 patient cohort study) can now be studied from a new perspective, and will help guide the design of next generation products, diagnostics and therapeutic applications.