Wise C J, Watt D J, Jones G E
Randall Institute, King's College London, United Kingdom.
J Cell Biochem. 1996 Jun 1;61(3):363-74. doi: 10.1002/(SICI)1097-4644(19960601)61:3%3C363::AID-JCB4%3E3.0.CO;2-R.
The limb and axial skeletal muscles of mammals originate from somitic dermomyotome, which during early development separates to form two discrete structures, the dermatome and the myotome. The latter cell mass gives rise to the muscle-forming lineage while cells of the dermatome will form the skin dermal fibroblast population of the dorsal regions of the body. It has been generally accepted for some time that myotome-derived myoblasts were the sole source of muscle fibre nuclei, but evidence has recently been presented from several laboratories that fibroblasts can fuse with myoblasts to contribute active nuclei to the resulting myotubes. We report here an investigation into the myogenic capacity of fibroblasts. Confluent monocultures of mouse dermal fibroblasts, muscle fibroblasts, and C2C12 myoblasts each retain their individual phenotype when maintained for periods up to 7 days in culture. We also grew isolated colonies of fibroblasts and myoblasts in an arrangement which allowed free exchange of tissue culture medium between the 2 cell types. We found evidence of the conversion of dermal fibroblasts to a myogenic lineage as measured by the appearance of MyoD-positive cells expressing the muscle-specific intermediate filament desmin. In addition, dermal fibroblast cultures contained multinucleate syncytia positive for MyoD and containing sarcomeric myosin heavy chain. In contrast, muscle-derived fibroblasts showed no evidence of myogenic conversion when maintained in identical culture conditions. We prepared conditioned medium from confluent cultures of C2C12 myoblasts and added this material to confluent monocultures of either dermal or muscle fibroblasts. While muscle fibroblasts showed no phenotypic alterations, cultures of dermal fibroblasts responded to myoblast conditioned medium by converting to a myogenic lineage as judged by expression of MyoD and desmin. We conclude that a proportion of dermal fibroblasts retain a myogenic capacity into stages well beyond their early association with myoblasts in the dermomyotome.
哺乳动物的肢体和轴向骨骼肌起源于体节性皮肌节，在早期发育过程中，皮肌节分离形成两个独立的结构，即皮节和肌节。后者的细胞团产生形成肌肉的谱系，而皮节的细胞将形成身体背部区域的皮肤真皮成纤维细胞群体。一段时间以来，人们普遍认为肌节来源的成肌细胞是肌肉纤维细胞核的唯一来源，但最近几个实验室提供的证据表明，成纤维细胞可以与成肌细胞融合，为形成的肌管贡献活性细胞核。我们在此报告一项关于成纤维细胞成肌能力的研究。将小鼠真皮成纤维细胞、肌肉成纤维细胞和C2C12成肌细胞的汇合单培养物在培养中维持长达7天，每种培养物都保持其各自的表型。我们还以一种允许两种细胞类型之间自由交换组织培养基的方式培养了分离的成纤维细胞集落和成肌细胞集落。我们发现，通过表达肌肉特异性中间丝结蛋白的MyoD阳性细胞的出现，有证据表明真皮成纤维细胞已转化为成肌谱系。此外，真皮成纤维细胞培养物中含有对MyoD呈阳性且含有肌节肌球蛋白重链的多核合胞体。相比之下，在相同培养条件下培养时，肌肉来源的成纤维细胞没有成肌转化的证据。我们从C2C12成肌细胞的汇合培养物中制备了条件培养基，并将这种物质添加到真皮或肌肉成纤维细胞的汇合单培养物中。虽然肌肉成纤维细胞没有表现出表型改变，但真皮成纤维细胞培养物对成肌细胞条件培养基有反应，通过MyoD和结蛋白的表达判断，它们已转化为成肌谱系。我们得出结论，一部分真皮成纤维细胞在远远超出其在皮肌节中与成肌细胞早期关联的阶段仍保留成肌能力。
