Myonuclear apoptosis in dystrophic mdx muscle occurs by perforin-mediated cytotoxicity.

Abstract

Myonuclear apoptosis is an early event in the pathology of dystrophin-deficient muscular dystrophy in the mdx mouse. However, events that initiate apoptosis in muscular dystrophy are unknown, and whether elimination of apoptosis can ameliorate subsequent muscle wasting remains a major question. We have tested the hypothesis that cytotoxic T-lymphocytes initiate myonuclear apoptosis in dystrophic muscle, and examined whether perforin-mediated cytotoxicity plays a role in the pathophysiology of muscular dystrophy. Mdx mice showed muscle invasion by cytotoxic T cells and helper T cells at the onset of histologically detectable muscle fiber pathology. At this time, perforin-expressing cells were also present at elevated concentration. Mdx mice depleted of CD8 ϩ cells showed a significant reduction of apoptotic myonuclei concentration and a reduction in necrosis, judged by macrophage invasion of muscle fibers. Double-mutant mice, deficient in dystrophin and perforin, showed nearly complete absence of myonuclear apoptosis, and a significant reduction in the concentration of macrophages in the connective tissue surrounding muscle fibers. However, muscle fiber invasion by macrophages was not reduced significantly in double mutant mice. Thus, cytotoxic T-lymphocytes contribute significantly to apoptosis and necrosis in mdx dystrophy, and perforin-mediated killing is primarily responsible for myonuclear apoptosis. ( J. Clin. Invest. 1997. 99:2745-2751.)

Stable expression of calpain 3 from a muscle transgene in vivo : Immature muscle in transgenic mice suggests a role for calpain 3 in muscle maturation

“…Tissue preparation and immunohistochemistry were performed as described (13). Antibodies used for staining were rat anti-NCAM (Chemicon, mAB 310), rat anti-Mac 1 (PharMingen), anti-AchR␣ (Transduction Laboratories, Lexington, KY), and mouse anti-fast MHC (NovoCastra, Newcastle, U.K.).…”

Gene expression profiling of Duchenne muscular dystrophy reveals characteristics along disease progression

“…As shown in Figure 1, most of the deregulated pathways involved inflammatory/immune responses, including immune disease, immune system, and infectious disease. These immune/inflammatory pathways mainly indicated the infiltration of immune cells, such as T cells (McDouall et al, 1990;Spencer et al, 1997), macrophages (McDouall et al, 1990;Spencer et al, 1997), eosinophils (Cai et al, 2000), and mast cells (Granchelli et al, 1995;Nahirney et al, 1997), into muscles and elevated levels of various inflammatory cytokines. A previous study showed that in vivo depletions of CD4 or CD8 T cells or macrophages (Wehling et al, 2001) significantly reduced the pathology in mdx mice, and that the efficacy of the only drugs currently available for the treatment of DMD (glucocorticoids) in delaying DMD progression is mainly based on the suppression of inflammation (Serra et al, 2012), implicating the important roles of immune/ inflammation responses in aggravating the disease.…”

Partial least squares based identification of Duchenne muscular dystrophy specific genes

“…In addition, most of the pathways in which aberrantly regulated enriched genes were involved resulted in an inflammatory/immune response. This may result from the infiltration of immune cells into the muscles (Mcdouall et al, 1990;Spencer et al, 1997;Cai et al, 2000) and also in elevated levels of various inflammatory cytokines. For muscle regeneration, two genes which encode embryonic and perinatal myosin heavy chains (MYH3 and MYH8) were overexpressed, consistent with Haslett et al (2002).…”