ABSTRACT

Purpose: Collagen IV is a component of the basement membrane (BM) that provides mechanical support for muscle fibers. In addition, transcription factor 4 (TCF4) is highly expressed in muscle connective tissue fibroblasts and regulates muscle regeneration. However, the expression of collagen IV and TCF4 (+) cells in response to exercise-induced muscle injury is not well known. Here, we investigated the expression and localization of collagen IV and TCF4 (+) cells during the recovery process after muscle injury induced by different exercise loads.

Materials and Methods: Muscle injury was observed in the soleus muscle of young Wistar rats after 12 or 18 sets—downhill running (DR) on a treadmill. After running, the rats were permitted to recover for a period of 0.5 days, 2 days, or 7 days.

Results: Ectopic localization of collagen IV in injured muscle fibers was observed after DR, and the number increased at 0.5 days after 18 sets DR and at 2 days after 12 or 18 sets DR as compared to the number observed at baseline. BM disruption was observed after DR. TCF4 (+) cells appeared in the inside and around injured muscle fibers at 0.5 day of recovery. After 18 sets DR, TCF4 (+) cells were more abundant for a longer period than that observed after 12 sets DR.

Conclusions: DR induces BM disruption accompanied by muscle fiber damage. It is possible that BM destruction may be accompanied by muscle damage and that TCF4 (+) cells contribute to muscle fiber and BM recovery.

摘要

目的：胶原蛋白 IV 是基底膜 (BM) 的一种成分，可为肌肉纤维提供机械支撑。此外，转录因子 4 (TCF4) 在肌肉结缔组织成纤维细胞中高度表达并调节肌肉再生。然而，胶原蛋白 IV 和 TCF4 (+) 细胞对运动引起的肌肉损伤的反应尚不清楚。在这里，我们研究了不同运动负荷引起的肌肉损伤后恢复过程中胶原蛋白 IV 和 TCF4 (+) 细胞的表达和定位。

材料和方法：在跑步机上进行 12 组或 18 组下坡跑步 (DR) 后，观察到年轻 Wistar 大鼠比目鱼肌的肌肉损伤。跑完后，让大鼠恢复0.5天、2天或7天的时间。

结果： DR 后观察到损伤肌肉纤维中胶原蛋白 IV 的异位定位，与基线观察到的数量相比，18 组 DR 后 0.5 天和 12 组或 18 组 DR 后 2 天的数量增加。DR 后观察到 BM 破坏。在恢复 0.5 天时，TCF4 (+) 细胞出现在受伤的肌肉纤维内部和周围。18 组 DR 后，TCF4 (+) 细胞比 12 组 DR 后观察到的更丰富的时间更长。

结论： DR 诱导 BM 破坏并伴有肌纤维损伤。BM 破坏可能伴随肌肉损伤，TCF4 (+) 细胞有助于肌肉纤维和 BM 恢复。