Institute of Biomedical Sciences (Health Sciences), Nagasaki University, Nagasaki, Japan.
Department of Rehabilitation, Nagasaki University Hospital, Nagasaki, Japan.
PLoS One. 2021 May 13;16(5):e0244120. doi: 10.1371/journal.pone.0244120. eCollection 2021.
Macrophage accumulation in response to decreasing myonuclei may be the major mechanism underlying immobilization-induced muscle fibrosis in muscle contracture, an intervention strategy suppressing these lesions is necessary. Therefore, this research investigated the effect of belt electrode-skeletal muscle electrical stimulation (B-SES), a new electrical stimulation device, to the macrophage accumulation via myonuclei decrease in immobilization-induced muscle fibrosis.
18 Wistar male rats were divided into the control group, immobilization group (with plaster cast fixation to immobilize the soleus muscles in a shortened position for 2 weeks), and B-SES group (with muscle contractile exercise through B-SES during the immobilization period). B-SES stimulation was performed at a frequency of 50 Hz and an intensity of 4.7 mA, muscle contractile exercise by B-SES was applied to the lower limb muscles for 20 minutes/session (twice a day) for 2 weeks (6 times/week). The bilateral soleus muscles were used for histological, immunohistochemical, biochemical, and molecular biological analyses.
The number of myonuclei was significantly higher in the B-SES group than in the immobilization group, and there was no significant difference between the B-SES and control groups. The cross-sectional area of type I and II myofibers in the immobilization and B-SES groups was significantly lower than that in the control group, and the cross-sectional area of type I myofibers in the B-SES group was higher than that in the immobilization group. However, Atrogin-1 and MuRF-1 mRNA expression in the immobilization and B-SES groups was significantly higher than those in the control group. Additionally, the number of macrophages, IL-1β, TGF-β1, and α-SMA mRNA expression, and hydroxyproline expression was significantly lower in the control and B-SES groups than those in the immobilization group.
This research surmised that muscle contractile exercise through B-SES prevented immobilization-induced muscle fibrosis, and this alteration suppressed the development of muscle contracture.
肌纤维减少导致的肌核减少所引起的巨噬细胞聚集，可能是固定导致的肌肉纤维化的主要机制，因此，有必要寻找一种抑制这些病变的干预策略。本研究通过观察骨-电极-骨骼肌电刺激（B-SES）对固定诱导的肌肉纤维化中肌核减少导致的巨噬细胞聚集的影响，探讨一种新的电刺激装置。
将 18 只 Wistar 雄性大鼠分为对照组、固定组（用石膏固定将比目鱼肌置于缩短位置 2 周）和 B-SES 组（在固定期间通过 B-SES 进行肌肉收缩运动）。B-SES 刺激频率为 50 Hz，强度为 4.7 mA，通过 B-SES 进行肌肉收缩运动，每次 20 分钟/次（每天两次），共 2 周（每周 6 次）。用于组织学、免疫组织化学、生化和分子生物学分析的双侧比目鱼肌。
B-SES 组的肌核数量明显高于固定组，与对照组无显著差异。固定组和 B-SES 组的 I 型和 II 型肌纤维横截面积明显低于对照组，B-SES 组的 I 型肌纤维横截面积高于固定组。但是，固定组和 B-SES 组的 Atrogin-1 和 MuRF-1 mRNA 表达明显高于对照组。此外，与固定组相比，对照组和 B-SES 组的巨噬细胞数量、IL-1β、TGF-β1、α-SMA mRNA 表达和羟脯氨酸表达均显著降低。
本研究推测，通过 B-SES 进行肌肉收缩运动可预防固定引起的肌肉纤维化，从而抑制肌肉挛缩的发展。
