Kuschel R, Yablonka-Reuveni Z, Bornemann A
Institute of Brain Research, University of Tübingen, Tübingen, Germany.
J Histochem Cytochem. 1999 Nov;47(11):1375-84. doi: 10.1177/002215549904701104.
Satellite cells (SCs) in normal adult muscle are quiescent. They can enter the mitotic program when stimulated with growth factors such as basic FGF. Short-term denervation stimulates SC to enter the mitotic cycle in vivo, whereas long-term denervation depletes the SC pool. The molecular basis for the neural influence on SCs has not been established. We studied the phenotype and the proliferative capacity of SCs from muscle that had been denervated before being cultured in vitro. The expression of PCNA, myogenin, and muscle (M)-cadherin in SCs of normal and denervated muscle fibers was examined at the single-cell level by immunolabeling in a culture system of isolated rat muscle fibers with attached SCs. Immediately after plating (Day 0), neither PCNA nor myogenin was present on normal muscle fibers, but we detected an average of 0.5 M-cadherin(+) SCs per muscle fiber. The number of these M-cadherin(+) cells (which are negative for PCNA and myogenin) increased over the time course examined. A larger fraction of cells negative for M-cadherin underwent mitosis and expressed PCNA, followed by myogenin. The kinetics of SCs from muscle fibers denervated for 4 days before culturing were similar to those of normal controls. Denervation from 1 to 32 weeks before plating, however, suppressed PCNA and myogenin expression almost completely. The fraction of M-cadherin(+) (PCNA(-)/myogenin(-)) SCs was decreased after 1 week of denervation, increased above normal after denervation for 4 or 8 weeks, and decreased again after denervation for 16 or 32 weeks. We suggest that the M-cadherin(+) cells are nondividing SCs because they co-express neither PCNA or myogenin, whereas the cells positive for PCNA or myogenin (and negative for M-cadherin) have entered the mitotic cycle. SCs from denervated muscle were different from normal controls when denervated for 1 week or longer. The effect of denervation on the phenotypic modulation of SCs includes resistance to recruitment into the mitotic cycle under the conditions studied here and a robust extension of the nonproliferative compartment. These characteristics of SCs deprived of neural influence may account for the failure of denervated muscle to fully regenerate. (J Histochem Cytochem 47:1375-1383, 1999)
正常成年肌肉中的卫星细胞（SCs）处于静止状态。当受到碱性成纤维细胞生长因子等生长因子刺激时，它们可进入有丝分裂程序。短期去神经支配可刺激卫星细胞在体内进入有丝分裂周期，而长期去神经支配则会耗尽卫星细胞池。神经对卫星细胞影响的分子基础尚未明确。我们研究了在体外培养前已去神经支配的肌肉中卫星细胞的表型和增殖能力。在分离的带有卫星细胞的大鼠肌肉纤维培养系统中，通过免疫标记在单细胞水平检测正常和去神经支配的肌肉纤维卫星细胞中增殖细胞核抗原（PCNA）、生肌调节因子和肌肉（M）-钙黏蛋白的表达。接种后立即（第0天），正常肌肉纤维上既没有PCNA也没有生肌调节因子，但我们检测到每条肌肉纤维平均有0.5个M-钙黏蛋白阳性卫星细胞。在整个检测的时间过程中，这些M-钙黏蛋白阳性细胞（对PCNA和生肌调节因子呈阴性）的数量增加。更多对M-钙黏蛋白呈阴性的细胞进入有丝分裂并表达PCNA，随后表达生肌调节因子。培养前已去神经支配4天的肌肉纤维中卫星细胞的动力学与正常对照相似。然而，接种前1至32周的去神经支配几乎完全抑制了PCNA和生肌调节因子的表达。去神经支配1周后，M-钙黏蛋白阳性（PCNA阴性/生肌调节因子阴性）卫星细胞的比例降低，去神经支配4周或8周后高于正常水平，而去神经支配16周或32周后又再次降低。我们认为M-钙黏蛋白阳性细胞是不分裂的卫星细胞，因为它们既不共表达PCNA也不共表达生肌调节因子，而对PCNA或生肌调节因子呈阳性（对M-钙黏蛋白呈阴性）的细胞已进入有丝分裂周期。当去神经支配1周或更长时间时，去神经支配肌肉中的卫星细胞与正常对照不同。去神经支配对卫星细胞表型调节的影响包括在此研究条件下对进入有丝分裂周期的募集产生抗性以及非增殖区室的显著扩展。这些缺乏神经影响的卫星细胞特征可能解释了去神经支配肌肉不能完全再生的原因。（《组织化学与细胞化学杂志》47:1375 - 1383，1999年）
