Hill Maria, Wernig A, Goldspink G
Basic Medical Sciences and Department of Surgery, Royal Free and University College Medical School, London University, UK.
J Anat. 2003 Jul;203(1):89-99. doi: 10.1046/j.1469-7580.2003.00195.x.
In post-mitotic tissues, damaged cells are not replaced by new cells and hence effective local tissue repair mechanisms are required. In skeletal muscle, which is a syncytium, additional nuclei are obtained from muscle satellite (stem) cells that multiply and then fuse with the damaged fibres. Although insulin-like growth factor-I (IGF-l) had been previously implicated, it is now clear that muscle expresses at least two splice variants of the IGF-I gene: a mechanosensitive, autocrine, growth factor (MGF) and one that is similar to the liver type (IGF-IEa). To investigate this activation mechanism, local damage was induced by stretch combined with electrical stimulation or injection of bupivacaine in the rat anterior tibialis muscle and the time course of regeneration followed morphologically. Satellite cell activation was studied by the distribution and levels of expression of M-cadherin (M-cad) and related to the expression of the two forms of IGF-I. It was found that the following local damage MGF expression preceded that of M-cad whereas IGF-IEa peaked later than M-cad. The evidence suggests therefore that an initial pulse of MGF expression following damage is what activates the satellite cells and that this is followed by the later expression of IGF-IEa to maintain protein synthesis to complete the repair.
在有丝分裂后的组织中，受损细胞不会被新细胞替代，因此需要有效的局部组织修复机制。在作为多核体的骨骼肌中，额外的细胞核来自肌肉卫星（干）细胞，这些细胞增殖后与受损纤维融合。尽管胰岛素样生长因子-I（IGF-I）此前就被认为与此有关，但现在清楚的是，肌肉表达IGF-I基因的至少两种剪接变体：一种机械敏感的自分泌生长因子（MGF）和一种与肝脏型相似的变体（IGF-IEa）。为了研究这种激活机制，通过拉伸联合电刺激或在大鼠胫前肌注射布比卡因诱导局部损伤，并从形态学上追踪再生的时间进程。通过M-钙黏蛋白（M-cad）的分布和表达水平研究卫星细胞的激活，并将其与两种形式的IGF-I的表达相关联。结果发现，在局部损伤后，MGF的表达先于M-cad，而IGF-IEa的峰值晚于M-cad。因此，有证据表明，损伤后MGF表达的初始脉冲激活了卫星细胞，随后IGF-IEa的后期表达维持蛋白质合成以完成修复。
