Mechanisms leading to restoration of muscle size with exercise and transplantation after spinal cord injury

被引:62
作者
Dupont-Versteegden, EE
Murphy, RJL
Houlé, JD
Gurley, CM
Peterson, CA
机构
[1] Univ Arkansas Med Sci, Reynolds Ctr Aging, Dept Geriatr, Little Rock, AR 72205 USA
[2] Univ Arkansas Med Sci, Dept Anat, Little Rock, AR 72205 USA
[3] Cent Arkansas Vet Hlth Care Syst, Little Rock, AR 72205 USA
来源
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY | 2000年 / 279卷 / 06期
关键词
muscle atrophy; satellite cells; insulin-like growth factor; myonuclear number;
D O I
10.1152/ajpcell.2000.279.6.C1677
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
We have shown that cycling exercise combined with fetal spinal cord transplantation restored muscle mass reduced as a result of complete transection of the spinal cord. In this study, mechanisms whereby this combined intervention increased the size of atrophied soleus and plantaris muscles were investigated. Rats were divided into five groups (n = 4, per group): control, nontransected; spinal cord transected at T10 for 8 wk (Tx); spinal cord transected for 8 wk and exercised for the last 4 wk (TxEx); spinal cord transected for 8 wk with transplantation of fetal spinal cord tissue into the lesion site 4 wk prior to death (TxTp); and spinal cord transected for 8 wk, exercised for the last 4 wk combined with transplantation 4 wk prior to death (TxExTp). Tx soleus and plantaris muscles were decreased in size compared with control. Exercise and transplantation alone did not restore muscle size in soleus, but exercise alone minimized atrophy in plantaris. However, the combination of exercise and transplantation resulted in a significant increase in muscle size in soleus and plantaris compared with transection alone. Furthermore, myofiber nuclear number of soleus was decreased by 40% in Tx and was not affected in TxEx or TxTp but was restored in TxExTp. A strong correlation (r = 0.85) between myofiber cross-sectional area and myofiber nuclear number was observed in soleus, but not in plantaris muscle, in which myonuclear number did not change with any of the experimental manipulations. 59-Bromo-29-deoxyuridine-positive nuclei inside the myofiber membrane were observed in TxExTp soleus muscles, indicating that satellite cells had divided and subsequently fused into myofibers, contributing to the increase in myonuclear number. The increase in satellite cell activity did not appear to be controlled by the insulin-like growth factors (IGF), as IGF-I and IGF-II mRNA abundance was decreased in Tx soleus and plantaris, and was not restored with the interventions. These results indicate that, following a relatively long postinjury interval, exercise and transplantation combined restore muscle size. Satellite cell fusion and restoration of myofiber nuclear number contributed to increased muscle size in the soleus, but not in plantaris, suggesting that cellular mechanisms regulating muscle size differ between muscles with different fiber type composition.
引用
收藏
页码:C1677 / C1684
页数:8
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