Nagata Yuki, Kiyono Tohru, Okamura Kikuo, Goto Yu-Ichi, Matsuo Masafumi, Ikemoto-Uezumi Madoka, Hashimoto Naohiro
Department of Regenerative Medicine, National Center for Geriatrics and Gerontology, Morioka, Oobu, Aichi, Japan.
Division of Carcinogenesis and Cancer Prevention, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo, Japan.
PLoS One. 2017 Dec 1;12(12):e0188821. doi: 10.1371/journal.pone.0188821. eCollection 2017.
Duchenne muscular dystrophy (DMD) is a severe X-linked recessive muscle disorder caused by mutations in the dystrophin gene. Nonetheless, secondary processes involving perturbation of muscle regeneration probably exacerbate disease progression, resulting in the fatal loss of muscle in DMD patients. A dysfunction of undifferentiated myogenic cells is the most likely cause for the reduction of regenerative capacity of muscle. To clarify molecular mechanisms in perturbation of the regenerative capacity of DMD muscle, we have established several NCAM (CD56)-positive immortalized human dystrophic and non-dystrophic myogenic cell lines from DMD and healthy muscles. A pro-inflammatory cytokine, IL-1β, promoted cell cycle progression of non-dystrophic myogenic cells but not DMD myogenic cells. In contrast, IL-1β upregulated the Notch ligand Jagged1 gene in DMD myogenic cells but not in non-dystrophic myogenic cells. Knockdown of Jagged1 in DMD myogenic cells restored the IL-1β-promoted cell cycle progression. Conversely, enforced expression of Jagged1-blocked IL-1β promoted proliferation of non-dystrophic myogenic cells. In addition, IL-1β prevented myogenic differentiation of DMD myogenic cells depending on Jagged1 but not of non-dystrophic myogenic cells. These results demonstrate that Jagged1 induced by IL-1β in DMD myogenic cells modified the action of IL-1β and reduced the ability to proliferate and differentiate. IL-1β induced Jagged1 gene expression may be a feedback response to excess stimulation with this cytokine because high IL-1β (200-1000 pg/ml) induced Jagged1 gene expression even in non-dystrophic myogenic cells. DMD myogenic cells are likely to acquire the susceptibility of the Jagged1 gene to IL-1β under the microcircumstances in DMD muscles. The present results suggest that Jagged1 induced by IL-1β plays a crucial role in the loss of muscle regeneration capacity of DMD muscles. The IL-1β/Jagged1 pathway may be a new therapeutic target to ameliorate exacerbation of muscular dystrophy in a dystrophin-independent manner.
杜氏肌营养不良症（DMD）是一种严重的X连锁隐性肌肉疾病，由肌营养不良蛋白基因突变引起。尽管如此，涉及肌肉再生紊乱的继发过程可能会加剧疾病进展，导致DMD患者肌肉的致命性丧失。未分化的成肌细胞功能障碍最有可能是肌肉再生能力下降的原因。为了阐明DMD肌肉再生能力紊乱的分子机制，我们从DMD和健康肌肉中建立了几种NCAM（CD56）阳性的永生化人类营养不良性和非营养不良性成肌细胞系。促炎细胞因子IL-1β促进非营养不良性成肌细胞的细胞周期进程，但不促进DMD成肌细胞的细胞周期进程。相反，IL-1β上调DMD成肌细胞中Notch配体Jagged1基因的表达，但不上调非营养不良性成肌细胞中该基因的表达。在DMD成肌细胞中敲低Jagged1可恢复IL-1β促进的细胞周期进程。相反，Jagged1的强制表达阻断了IL-1β促进非营养不良性成肌细胞的增殖。此外，IL-1β依赖Jagged1阻止DMD成肌细胞的成肌分化，但不阻止非营养不良性成肌细胞的成肌分化。这些结果表明，IL-1β在DMD成肌细胞中诱导的Jagged1改变了IL-1β的作用，并降低了其增殖和分化能力。IL-1β诱导Jagged1基因表达可能是对该细胞因子过度刺激的一种反馈反应，因为高浓度的IL-1β（200-1000 pg/ml）即使在非营养不良性成肌细胞中也能诱导Jagged1基因表达。DMD成肌细胞可能在DMD肌肉的微环境下获得了Jagged1基因对IL-1β的敏感性。目前的结果表明，IL-1β诱导的Jagged1在DMD肌肉再生能力丧失中起关键作用。IL-1β/Jagged1途径可能是以不依赖肌营养不良蛋白的方式改善肌肉营养不良症恶化的新治疗靶点。
