[Expression of connective tissue growth factor in progressive muscular dystrophy]

Abstract

Objective: Progressive muscular dystrophy (PMD) is characterized by muscle fiber necrosis, regeneration, and endomysial fibrosis. Although absence of dystrophin and subsarcolemmic protein has been known as the cause of muscle fiber degeneration, pathogenesis of interstitial fibrosis is still unknown. The aim of this study was to investigate the role of connective tissue growth factor (CTGF) in PMD and its relationship with muscular fibrosis.

Methods: Immunological localization of CTGF was examined in frozen muscle specimens obtained via biopsy from 8 patients with Duchenne muscular dystrophy (DMD), 2 patients with Becker muscular dystrophy (BMD), 6 patients with congenital muscular dystrophy (CMD) and 6 cases with normal muscle by immunohistochemistry, double immunofluorescence and Western blot analysis.

Results: The results of immunohistochemistry and double immunofluorescence showed that CTGF was positive only in vessels of normal muscle. Both immunohistochemistry and Western blot analysis showed that CTGF expression was distinctly increased in dystrophy muscles of PMD than that in normal muscles. In dystrophy muscle, marked immunostaining of CTGF was not only observed in vascular walls, but also strongly expressed in the cytoplasm and nuclei of regenerating muscle fibers, and also immunolocalized in the muscle fiber sarcolemma of non-regenerating fibers. Double labeling with antibodies against CTGF and CD68 demonstrated that CTGF was expressed in some macrophages and some macrophage infiltrated necrotic fibers. CTGF was strongly expressed in endomysial and perimysial connective tissues of dystrophy muscles of patients with DMD, CMD and FCMD. Double immunolabeling revealed that most activated fibroblasts in perimysium and endomysium were positive for CTGF, but not all of connective tissues were co-localized with CTGF. Older cases with FCMD showed poor or no expression of CTGF in advanced fibrosis.

Conclusion: CTGF may play a role in the pathogenetic process of muscular dystrophy, and CTGF may be important for muscle repair and fibrosis.