Nakama S, Ooi Y, Mato M
Department of Orthopaedic Surgery, Jichi Medical School, Tochigi.
Nihon Seikeigeka Gakkai Zasshi. 1994 Jul;68(7):560-71.
The repair of injured muscle is completed by a proliferation and differentiation of myogenic cells and myotubes. However, little is known about the microenvironment in which the formation of myotubes can proceed in vivo. We employed the polyvinyl alcohol (PVA) sponge model to investigate the milieu in which myotubes could be differentiated. Small pieces of PVA sponge were implanted after immersion in physiological saline into the gastrocnemius of adult Wistar rats as controls. In the experimental groups, before implantation, PVA were treated with basic fibroblast growth factor (FGF), type IV collagen, laminin and hydrocortisone. Newly-formed tissues within the PVA were examined immuno- and histochemically under light- and electronmicroscopy after 7 to 10 days implantation. Particular attention was focused on the formation of myofilaments in the migrating cells. From this study, it became clear that FGF, collagen and laminin accelerated the migration of mesenchymal cells into the PVA compared with controls. However, myotube formation could not be detected in either the experimental or control groups. But in the specimen treated with 10mg/ml hydrocortisone, myotubes appeared frequently in the migrating cells of PVA. A small amount of fibroblasts, macrophages and eosinophils were scattered around the myotubes and not clustered. They were provided with undefined basal lamina. Fibronectin and collagen fibers were also detected surrounding the myotubes. These findings suggested that, although the migration of satellite cells and the appearance of fibronectin are prerequisites for myotube formation, the most promising condition for myotube formation involved a suppression in the migration of the fibroblasts, macrophages and eosinophils. A certain concentration of steroids can therefore prepare a favorable microenvironment for this process.
受损肌肉的修复是通过肌原细胞和肌管的增殖与分化来完成的。然而，关于肌管在体内形成的微环境却知之甚少。我们采用聚乙烯醇（PVA）海绵模型来研究肌管能够分化的环境。将小块PVA海绵浸入生理盐水中后植入成年Wistar大鼠的腓肠肌作为对照。在实验组中，植入前用碱性成纤维细胞生长因子（FGF）、IV型胶原、层粘连蛋白和氢化可的松处理PVA。植入7至10天后，对PVA内新形成的组织进行免疫和组织化学检查，分别在光学显微镜和电子显微镜下观察。特别关注迁移细胞中肌丝的形成。从这项研究中可以清楚地看出，与对照组相比，FGF、胶原和层粘连蛋白加速了间充质细胞向PVA的迁移。然而，在实验组和对照组中均未检测到肌管形成。但在经10mg/ml氢化可的松处理的标本中，PVA迁移细胞中频繁出现肌管。少量成纤维细胞、巨噬细胞和嗜酸性粒细胞散布在肌管周围，并未聚集。它们有不明确的基膜。在肌管周围也检测到纤连蛋白和胶原纤维。这些发现表明，尽管卫星细胞的迁移和纤连蛋白的出现是肌管形成的先决条件，但肌管形成最有利的条件涉及抑制成纤维细胞、巨噬细胞和嗜酸性粒细胞的迁移。因此，一定浓度的类固醇可为这一过程营造有利的微环境。
