Department of Physiology, Medical School, National and Kapodistrian University of Athens, 75 Micras Asias, 115 27 Athens, Greece.
School of Biological Sciences, Deanery of Biomedical Sciences, Centre for Discovery Brain Sciences, Edinburgh EH8 9JZ, UK.
Cells. 2022 Dec 9;11(24):3979. doi: 10.3390/cells11243979.
During aging, muscle cell apoptosis increases and myogenesis gradually declines. The impaired myogenic and survival potential of the aged skeletal muscle can be ameliorated by its mechanical loading. However, the molecular responses of aged muscle cells to mechanical loading remain unclear. This study examined the effect of mechanical loading of aged, proliferating, and differentiated myoblasts on the gene expression and signaling responses associated with their myogenic lineage progression and survival.
Control and aged C2C12 cells were cultured on elastic membranes and underwent passive stretching for 12 h at a low frequency (0.25 Hz) and different elongations, varying the strain on days 0 and 10 of myoblast differentiation. Activation of ERK1/2 and Akt, and the expression of focal adhesion kinase (FAK) and key myogenic regulatory factors (MRFs), MyoD and Myogenin, were determined by immunoblotting of the cell lysates derived from stretched and non-stretched myoblasts. Changes in the expression levels of the MRFs, muscle growth, atrophy, and pro-apoptotic factors in response to mechanical loading of the aged and control cells were quantified by real-time qRT-PCR.
Mechanical stretching applied on myoblasts resulted in the upregulation of FAK both in proliferating (day 0) and differentiated (day 10) cells, as well as in increased phosphorylation of ERK1/2 in both control and aged cells. Moreover, Akt activation and the expression of early differentiation factor MyoD increased significantly after stretching only in the control myoblasts, while the late differentiation factor Myogenin was upregulated in both the control and aged myoblasts. At the transcriptional level, mechanical loading of the proliferating myoblasts led to an increased expression of IGF-1 isoforms and MRFs, and to downregulation of muscle atrophy factors mainly in control cells, as well as in the upregulation of pro-apoptotic factors both in control and aged cells. In differentiated cells, mechanical loading resulted in an increased expression of the IGF-1Ea isoform and Myogenin, and in the downregulation of atrophy and pro-apoptotic factors in both the control and aged cells.
This study revealed a diminished beneficial effect of mechanical loading on the myogenic and survival ability of the senescent muscle cells compared with the controls, with a low strain (2%) loading being most effective in upregulating myogenic/anabolic factors and downregulating atrophy and pro-apoptotic genes mainly in the aged myotubes.
随着年龄的增长，肌肉细胞凋亡增加，成肌作用逐渐下降。衰老骨骼肌的成肌和存活潜能可以通过机械加载得到改善。然而，衰老肌肉细胞对机械加载的分子反应仍不清楚。本研究检测了机械加载对增殖和分化的衰老成肌细胞的基因表达和信号转导的影响，这些基因表达和信号转导与它们的成肌谱系进展和存活有关。
将对照和衰老的 C2C12 细胞培养在弹性膜上，并在低频（0.25 Hz）和不同伸长率下进行 12 小时的被动拉伸，在成肌细胞分化的第 0 天和第 10 天改变应变。通过拉伸和未拉伸的成肌细胞的细胞裂解物的免疫印迹检测 ERK1/2 和 Akt 的激活以及粘着斑激酶（FAK）和关键成肌调节因子（MRFs）MyoD 和 Myogenin 的表达。通过实时 qRT-PCR 定量检测衰老和对照细胞对机械加载的 MRFs、肌肉生长、萎缩和促凋亡因子的表达水平变化。
成肌细胞的机械拉伸导致增殖（第 0 天）和分化（第 10 天）细胞中 FAK 的上调，以及对照和衰老细胞中 ERK1/2 的磷酸化增加。此外，仅在对照成肌细胞中，Akt 激活和早期分化因子 MyoD 的表达显著增加，而晚期分化因子 Myogenin 在对照和衰老的成肌细胞中均上调。在转录水平上，增殖的成肌细胞的机械加载导致 IGF-1 同工型和 MRFs 的表达增加，主要在对照细胞中肌肉萎缩因子的下调，以及对照和衰老细胞中促凋亡因子的上调。在分化细胞中，机械加载导致 IGF-1Ea 同工型和 Myogenin 的表达增加，以及对照和衰老细胞中萎缩和促凋亡因子的下调。
与对照相比，机械加载对衰老肌肉细胞的成肌和存活能力的有益影响减弱，低应变（2%）加载主要在衰老的肌管中上调成肌/合成代谢因子，下调萎缩和促凋亡基因。
Zotero 插件
