Satellite cells of the rat soleus muscle in the process of compensatory hypertrophy combined with denervation

Abstract

Compensatory hypertrophy was induced in the rat soleus muscle by sectioning the tendon of the ipsilateral gastrocnemius and plantaris muscle. Seven days after tenotomy of synergistic muscles, when soleus hypertrophy attains about 40%, the number of satellite cells (expressed as percentage of all muscle nuclei found in the same cross-sections) as revealed by electron microscopy, was increased from 5.8+/-0.06% in the normal soleus muscle to 16.6+/-1.26%. After four days' denervation of the soleus muscle the percentage of satellite cells was increased to 7.2+/-0.62%. In experiments where hypertrophy of the soleus muscle was combined with denervation three days after tenotomy of synergists, and examined after another four days (during which time it loses, as has previously been shown, over 40% of its predenervation weight), the number of satellite cells was greatly increased to 29.9+/-3.42%. This increase is apparently due to two independent processes which take place during the first postoperative period: a) mitotic division of satellite cells during the early stages of compensatory hypertrophy and b) pinching off of muscle nuclei from rapidly atrophying muscle fibres due to subsequent denervation. Activation of satellite cells was mainly manifested by expansion of smooth and especially of rough endoplasmic reticulum, a rich Golgi complex, high pinocytotic activity, increased number of ribosomes and by nuclear changes. Concomitantly with the increased number of satellite cells, proliferation of fibroblasts, macrophages and mast cells could be observed.

Aging of Skeletal Muscle Does Not Affect the Response of Satellite Cells to Denervation

“…However, these studies have generated some controversy concerning the timing of increases of the number of SCs in denervated muscles. Despite the fact that several authors reported a marked increase in the number of SCs during the first week following denervation (Hanzlikova et al 1975;McGeachie and Allbrook 1978), a few other studies demonstrated such increases between 2 and 4 weeks after nerve transection (Ontell 1974;Snow 1983). These findings are in contrast to those obtained in our laboratory.…”

“…Since skeletal muscle SCs were discovered, the standard and most precise method for quantitative detection of these cells has been to electron microscopy (Hanzlikova et al 1975;Snow 1977Snow ,1983 …”

Ultrastructural Analysis of Skeletal Muscle Development in the Fetal Pig

“…No morphological evidence of mitotic activity such as that reported in satellite cell nuclei [Shafiq et al, 1968;Moss and Leblond, 1971;Hanzlikova et al, 1975] was found in the myonuclei examined in this study. There also was no morphological evi dence to suggest that myonuclei budded off [Reznik, 1976], It is, therefore, postulated that the muscle fiber centrioles either repre sent remnants of mononucleated myogenic Fig-2.…”

Role of satellite cells in altering myosin expression during avian skeletal muscle hypertrophy

“…Embryonic myosin has been observed in regions remote from sites of focal injury leading to the suggestion that newly fused satellite cells, the myoblast-like cells in skeletal muscle (Mauro, 1961) that supply myofiber nuclei for muscle regeneration (Snow, 1977), might be responsible for altering myosin expression in these undamaged regions, as well as in sites of injury (Stewart et al, 1989). Satellite cells also supply hypertrophying fibers with additional nuclei (Schiaffino et al, 1972;Hanzlikova et al, 1975;Seiden, 1976;Snow, 1990;Winchester et al, 1991;Winchester and Gonyea, 19921, raising the possibility that satellite cells play a role in altering myosin isoform expression in hypertrophying fibers. We have examined this notion in the present study.…”