背景:老化会对组织修复产生负面影响,特别是在骨骼肌中,其中肌肉干细胞(MuSC)的再生能力随着年龄的增长而降低。尽管已知有氧运动可以减轻骨骼肌萎缩,其对MuSCs再生和修复能力的具体影响尚不清楚.
方法:小鼠从9个月(年龄+Ex-9M)或20个月(年龄+Ex-20M)到25个月接受中等强度连续训练(MICT),具有年龄匹配(年龄)和成人对照。组织学检查和MuSC移植测定评估了有氧运动对MuSC功能和肌肉再生的影响。研究了MuSC中的CCN2/结缔组织生长因子调节(过表达和敲低)和AICAR补充效果。
结果:老年小鼠的跑步时间显着减少(65.33±4.32vs.161.9±1.29分钟,平均值±SD,P<0.001)和距离(659.17±103.64vs.3058.28±46.26米,P<0.001)与成人相比。这种减少伴随着骨骼肌体重减轻和肌纤维横截面积(CSA)的减少。然而,在9或20个月时开始的MICT导致运行时间显着增加(142.75±3.14和133.86±20.47分钟,分别,与老年小鼠相比,P<0.001)和距离(2347.58±145.11和2263±643.87m,分别,P<0.001)。此外,MICT导致骨骼肌重量增加和CSA增强。在肌肉损伤模型中,老年小鼠表现出较少的中央核纤维(CNFs;266.35±68.66/mm2),当成年人,年龄+Ex-9M组和年龄+Ex-20M组显着更高的CNF计数(分别为610.82±46.76、513.42±47.19和548.29±71.82/mm2;与老年小鼠相比P<0.001)。从老年小鼠中分离的MuSCs显示CCN2表达增加,这被MICT有效地压制了。将过表达CCN2的MuSC(Lenti-CCN2,Lenti-CON作为对照)移植到受损的胫骨前肌受损的再生能力,与Lenti-CON相比,Lenti-CCN2组的CNF明显减少(488.07±27.63vs.173.99±14.28/mm2,P<0.001)在损伤后7天(dpi)。相反,敲除CCN2(Lenti-CCN2shR,Lenti-NegsiR作为对照)在老化的MuSCs中提高了再生能力,CNF计数从254.5±26.36增加到560.39±48.71/mm2。Lenti-CCN2MuSCs也增加成纤维细胞增殖和加重骨骼肌纤维化,而老年MuSCs中CCN2的敲除减轻了这种模式。AICAR补充,模仿运动,通过减轻肌肉重量下降来复制有氧运动的有益效果,增强卫星细胞活性和减少纤维化。
结论:有氧运动可有效逆转老年小鼠耐力能力的下降并减轻肌肉萎缩。它抑制衰老MuSCs分泌CCN2,从而增强老年小鼠的骨骼肌再生和预防纤维化。AICAR补充模拟有氧运动的有益效果。
BACKGROUND: Aging negatively impacts tissue repair, particularly in skeletal muscle, where the regenerative capacity of muscle stem cells (MuSCs) diminishes with age. Although aerobic exercise is known to attenuate skeletal muscle atrophy, its specific impact on the regenerative and repair capacity of MuSCs remains unclear.
METHODS: Mice underwent moderate-intensity continuous training (MICT) from 9 months (aged + Ex-9M) or 20 months (aged + Ex-20M) to 25 months, with age-matched (aged) and adult controls. Histological examinations and MuSC transplantation assays assessed aerobic exercise effects on MuSC function and muscle regeneration. CCN2/connective tissue growth factor modulation (overexpression and knockdown) in MuSCs and AICAR supplementation effects were explored.
RESULTS: Aged mice displayed significantly reduced running duration (65.33 ± 4.32 vs. 161.9 ± 1.29 min, mean ± SD, P < 0.001) and distance (659.17 ± 103.64 vs. 3058.28 ± 46.26 m, P < 0.001) compared with adults. This reduction was accompanied by skeletal muscle weight loss and decreased myofiber cross-sectional area (CSA). However, MICT initiated at 9 or 20 months led to a marked increase in running duration (142.75 ± 3.14 and 133.86 ± 20.47 min, respectively, P < 0.001 compared with aged mice) and distance (2347.58 ± 145.11 and 2263 ± 643.87 m, respectively, P < 0.001). Additionally, MICT resulted in increased skeletal muscle weight and enhanced CSA. In a muscle injury model, aged mice exhibited fewer central nuclear fibres (CNFs; 266.35 ± 68.66/mm2), while adult, aged + Ex-9M and aged + Ex-20M groups showed significantly higher CNF counts (610.82 ± 46.76, 513.42 ± 47.19 and 548.29 ± 71.82/mm2, respectively; P < 0.001 compared with aged mice). MuSCs isolated from aged mice displayed increased CCN2 expression, which was effectively suppressed by MICT. Transplantation of MuSCs overexpressing CCN2 (Lenti-CCN2, Lenti-CON as control) into injured tibialis anterior muscle compromised regeneration capacity, resulting in significantly fewer CNFs in the Lenti-CCN2 group compared with Lenti-CON (488.07 ± 27.63 vs. 173.99 ± 14.28/mm2, P < 0.001) at 7 days post-injury (dpi). Conversely, knockdown of CCN2 (Lenti-CCN2shR, Lenti-NegsiR as control) in aged MuSCs improved regeneration capacity, significantly increasing the CNF count from 254.5 ± 26.36 to 560.39 ± 48.71/mm2. Lenti-CCN2 MuSCs also increased fibroblast proliferation and exacerbated skeletal muscle fibrosis, while knockdown of CCN2 in aged MuSCs mitigated this pattern. AICAR supplementation, mimicking exercise, replicated the beneficial effects of aerobic exercise by mitigating muscle weight decline, enhancing satellite cell activity and reducing fibrosis.
CONCLUSIONS: Aerobic exercise effectively reverses the decline in endurance capacity and mitigates muscle atrophy in aged mice. It inhibits CCN2 secretion from senescent MuSCs, thereby enhancing skeletal muscle regeneration and preventing fibrosis in aged mice. AICAR supplementation mimics the beneficial effects of aerobic exercise.