Yablonka-Reuveni Zipora, Anderson Judy E
Department of Biological Structure, School of Medicine, University of Washington, Seattle, Washington, USA.
Dev Dyn. 2006 Jan;235(1):203-12. doi: 10.1002/dvdy.20602.
In the dystrophic (mdx) mouse, skeletal muscle undergoes cycles of degeneration and regeneration, and myogenic progenitors (satellite cells) show ongoing proliferation and differentiation at a time when counterpart cells in normal healthy muscle enter quiescence. However, it remains unclear whether this enhanced satellite cell activity is triggered solely by the muscle environment or is also governed by factors inherent in satellite cells. To obtain a better picture of myogenesis in dystrophic muscle, a direct cell-by-cell analysis was performed to compare satellite cell dynamics from mdx and normal (C57Bl/10) mice in two cell culture models. In one model, the kinetics of satellite cell differentiation was quantified in primary cell cultures from diaphragm and limb muscles by immunodetection of MyoD, myogenin, and MEF2. In mdx cell cultures, myogenin protein was expressed earlier than normal and was followed more rapidly by dual myogenin/MEF2A expression and myotube formation. In the second model, the dynamics of satellite cell myogenesis were investigated in cultured myofibers isolated from flexor digitorum brevis (FDB) muscle, which retain satellite cells in the native position. Consistent with primary cultures, satellite cells in mdx myofibers displayed earlier myogenin expression, as well as an enhanced number of myogenin-expressing satellite cells per myofiber compared to normal. The addition of fibroblast growth factor 2 (FGF2) led to an increase in the number of satellite cells expressing myogenin in normal and mdx myofibers. However, the extent of the FGF effect was more robust in mdx myofibers. Notably, many myonuclei in mdx myofibers were centralized, evidence of segmental regeneration; all central nuclei and many peripheral nuclei in mdx myofibers were positive for MEF2A. Results indicated that myogenic cells in dystrophic muscle display accelerated differentiation. Furthermore, the study demonstrated that FDB myofibers are an excellent model of the in vivo state of muscle, as they accurately represented the dystrophic phenotype.
在营养不良性（mdx）小鼠中，骨骼肌经历退化和再生循环，当正常健康肌肉中的对应细胞进入静止状态时，成肌祖细胞（卫星细胞）持续增殖和分化。然而，目前尚不清楚这种增强的卫星细胞活性是仅由肌肉环境触发，还是也受卫星细胞内在因素的调控。为了更好地了解营养不良性肌肉中的肌生成，我们进行了直接的逐个细胞分析，以比较mdx小鼠和正常（C57Bl/10）小鼠在两种细胞培养模型中的卫星细胞动态。在一种模型中，通过免疫检测MyoD、肌细胞生成素和MEF2，对来自膈肌和肢体肌肉的原代细胞培养物中卫星细胞分化的动力学进行了定量。在mdx细胞培养物中，肌细胞生成素蛋白的表达比正常情况更早，随后双肌细胞生成素/MEF2A表达和肌管形成的速度更快。在第二种模型中，研究了从短屈肌（FDB）肌肉分离的培养肌纤维中卫星细胞肌生成的动态，该肌肉在天然位置保留卫星细胞。与原代培养一致，mdx肌纤维中的卫星细胞显示出更早的肌细胞生成素表达，并且与正常情况相比，每个肌纤维中表达肌细胞生成素的卫星细胞数量增加。添加成纤维细胞生长因子2（FGF2）导致正常和mdx肌纤维中表达肌细胞生成素的卫星细胞数量增加。然而，FGF在mdx肌纤维中的作用程度更强。值得注意的是，mdx肌纤维中的许多肌核集中，这是节段性再生的证据；mdx肌纤维中的所有中央核和许多外周核MEF2A均呈阳性。结果表明，营养不良性肌肉中的成肌细胞显示出加速分化。此外，该研究表明，FDB肌纤维是肌肉体内状态的一个优秀模型，因为它们准确地呈现了营养不良表型。
