细胞因子IL-33调控巨噬细胞功能促进骨骼肌再生的分子机制研究

The unbalance of injury and regeneration in skeletal muscle leads to skeletal muscle atrophy. Inflammation response after muscle injury participates in muscle regeneration. Our preliminary studies suggested that cytokine interleukin-33 (IL-33) and receptor ST2 were up-regulated during the early stage of regeneration in young mouse, while the levels of IL-33 and ST2 were lower in elder mouse. ST2 knockout mouse exhibited impaired muscle regeneration and increased muscle fibrosis after injury, accompanied with less infiltration of macrophages. IL-33 could play a role of immune regulation by activating ST2 related signaling pathway. However, the role of IL-33 in muscle regeneration is still unknown. In this project, we hypothesis that after muscle injury, IL-33 was secreted from FAP in muscle under increased stretch stress, IL-33 activated ST2 of macrophages to produced cytokines to recruit more macrophages, which could promote the proliferation of myoblast and muscle regeneration. To verify this hypothesis, we will use ST2-/- mouse and IL-33 neutralization antibody in vivo, bone marrow transplantation, RNA-seq and cells co-culture in vitro to reveal the molecular mechanism of IL-33 in muscle regeneration. Our research will provide the new theoretical and experimental basis for intervention of muscle atrophy.

骨骼肌损伤后有效的再生可以避免骨骼肌萎缩的发生，炎症反应促进损伤后骨骼肌再生。课题组研究结果显示年轻小鼠损伤早期细胞因子IL-33及其受体ST2表达增加，而高龄小鼠的IL-33及ST2表达下调。IL-33受体ST2敲除小鼠骨骼肌再生能力受损，间质纤维化增加，巨噬细胞浸润减少。细胞因子IL-33通过ST2可发挥免疫炎症调控作用，但IL-33/ST2促进骨骼肌再生的具体作用机制尚不清楚。据此提出科学假设：肌纤维受损后，骨骼肌原位FAP受机械牵拉刺激分泌IL-33增加，激活巨噬细胞表面ST2促进招募巨噬细胞的细胞因子产生，促进肌母细胞增殖，最终促进骨骼肌再生。为了验证该假设，使用IL-33中和抗体及ST2敲除小鼠制作骨骼肌损伤再生模型，进行骨髓移植、转录组测序以及体外细胞共培养，从而明确调控IL-33表达的分子机制及其下游促进骨骼肌再生的分子机制，为寻找避免骨骼肌萎缩发生的靶点提供新思路。

骨骼肌损伤后有效的再生可以避免骨骼肌萎缩的发生，炎症反应促进损伤后骨骼肌再生。课题组研究结果显示年轻小鼠损伤早期细胞因子IL-33及其受体ST2表达增加，而高龄小鼠的IL-33及ST2表达下调。IL-33受体ST2敲除小鼠骨骼肌再生能力受损，间质纤维化增加，巨噬细胞浸润减少。细胞因子IL-33通过ST2可发挥免疫炎症调控作用，但IL-33/ST2促进骨骼肌再生的具体作用机制尚不清楚。本研究通过使用IL-33中和抗体及ST2 敲除小鼠制作骨骼肌损伤再生模型，进行骨髓移植、转录组测序以及体外细胞共培养等方法以明确调控IL-33表达的分子机制及其下游促进骨骼肌再生的信号通路。研究发现：1）ST2缺失小鼠骨骼肌再生能力下降，主要是由于招募分泌促再生性因子的巨噬细胞数量减少；2）在招募来的巨噬细胞细胞中鉴定出一类新亚型IFNRM，通过分泌CXCL10促进年轻和老年小鼠的骨骼肌再生；3）同时浸润的巨噬细胞通过miR-223抑制促炎性分子IL-6的过度表达，从而促进抗炎和促修复性巨噬细胞的分化，从而维持骨骼肌损伤再生时炎症微环境的平衡。我们的一系列发现将阐明骨骼肌损伤再生过程的分子调控机制，并为寻找延缓或避免骨骼肌萎缩发生的治疗靶点提供新思路。