肌纤维内源TGF-β信号促进急性损伤骨骼肌内巨噬细胞胞葬

Intrinsic transforming growth factor Beta signaling in myofiber promotes the role on macrophages efferocytosis in acute injured skeletal muscle

目的探究骨骼肌内源TGF-β信号对肌毒素诱导的小鼠急性损伤肌内巨噬细胞胞葬的影响。方法选择野生C57BL/6鼠(对照)、肌纤维条件性TGF-β受体Ⅱ敲除鼠(SM TGF-βr2^(-/-))。Cardiotoxin(CTX)胫骨前肌(TA)注射诱导小鼠急性肌损伤。比较两组动物损伤肌内巨噬细胞渗出及表型、凋亡细胞数目、巨噬细胞胞葬差异。紫外照射法体外诱导细胞凋亡。体外分化培养原代野生鼠(WT),或SM TGF-βr2^(-/-)-鼠成肌细胞(MPCs),与巨噬细胞、凋亡细胞共培养,对比分析巨噬细胞胞葬差异。结果较之WT鼠,SM TGF-βr2^(-/-)鼠损伤肌内炎性渗出显著,以单核/巨噬细胞为主。M1细胞比例增加(P<0.05),但M2细胞比例、胞葬作用显著下调(P<0.05)。体外炎性环境中,TGF-βr2^(-/-)-MPCs共培养体系中的巨噬细胞胞葬、M2巨噬细胞比例较之WT-MPCs均显著下调(P<0.05)。结论内源TGF-β信号活化肌纤维参与调控巨噬细胞表型,可促进损伤肌内巨噬细胞胞葬,有助于局部炎症舒缓,加快肌修复。

Objective To explore the role of skeletal muscle intrinsic transforming growth factor Beta(TGF-β)signaling on macrophages efferocytosis in inflamed muscle induced by Cardiotoxin(CTX)injection.Methods Wild C57BL/6 mice(control group)and mice with skeletal muscle-specific deficiency of TGF-βII(SM TGF-βr2^(-/-)group)were selected.Acute injured skeletal muscle was induced by CTX injection to the tibialis anterior muscle.After injection,the differences of the exudation of macrophages,macrophages phenotype,apoptotic cells and the role on macrophages efferocytosis in the inflamed muscle between the two groups were compared.Ultraviolet irradiation was taken to induce of apoptotic cells.In vitro,differentiation culture of primary WT,or SM TGF-βr2^(-/-)myoblasts(MPCs)were co-cultured with macrophages and apoptotic cells to compare and analyze the differences of the role on macrophages efferocytosis.Results Compared with the control group,the exudation of inflammatory cells in the injured muscle in SM TGF-βr2^(-/-)group significantly increased,mainly contained mononuclear cells/macrophages.The proportion of M1 macrophages significantly increased(P<0.05),but the proportion of M2 macrophages and the role on macrophages efferocytosis significantly decreased(P<0.05).In the co-cultured system in vitro,compared with the WTMPCs co-culture system,the role on macrophages efferocytosis and the proportion of M2 macrophages significantly decreased in TGF-βr2^(-/-)-MPCs co-culture system in the pro-inflammatory milieu(P<0.05).Conclusions Intrinsic TGF-βsignaling can promote the role on macrophages efferocytosis in the injured muscle by regulating macrophage phenotype,thus relieving local inflammation and accelerating muscle repair.