RESUMO
Skeletal muscles in mdx mice exhibit differential degrees of pathological changes and fibrosis. The purpose of this study was to examine differences in various indices of collagen metabolism in skeletal muscles with widely different functions and activity profiles in mdx mice, and to determine whether pirfenidone would attenuate the development of fibrosis. Mice in the pirfenidone group were orally fed pirfenidone (500 mg/kg) daily for 4 weeks. Marked differences were noted in hydroxyproline concentration between muscles, which could not be explained solely by the level of type I collagen and transforming growth factor-beta1 (TGF-beta1) mRNA. In normal mice, matrix metalloproteinase (MMP)-2 mRNA was significantly higher in the gastrocnemius than in the diaphragm or genioglossus muscles, suggesting that collagen degradation plays an important role in regulating collagen accretion in skeletal muscle. In mdx mice, the levels of both MMP-2 and MMP-9 mRNA were significantly elevated relative to control, although the response was muscle specific. Pirfenidone treatment resulted in a significant reduction in the level of hydroxyproline concentration across all muscles, although the effect was small. Results from this study reveal intrinsic dissimilarities in collagen metabolism between functionally different skeletal muscles. Moreover, the pharmacological use of pirfenidone may be beneficial in preventing fibrosis in muscular dystrophy.
Assuntos
Anti-Inflamatórios não Esteroides/uso terapêutico , Colágeno/metabolismo , Músculo Esquelético/metabolismo , Distrofia Muscular de Duchenne/tratamento farmacológico , Distrofia Muscular de Duchenne/patologia , Piridonas/uso terapêutico , Animais , Cromatografia Líquida de Alta Pressão/métodos , Modelos Animais de Doenças , Fibrose/etiologia , Fibrose/metabolismo , Fibrose/patologia , Técnicas In Vitro , Contração Isométrica/efeitos dos fármacos , Contração Isométrica/fisiologia , Masculino , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Distrofia Muscular de Duchenne/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Fator de Crescimento Transformador beta1/metabolismoRESUMO
Fibrosis is a common pathological feature observed in muscle from patients with Duchenne muscular dystrophy and in mdx diaphragm. The purpose of this study was to determine whether pentoxifylline (PTX) treatment for 4 weeks (16 mg/kg/day) could significantly attenuate the process of fibrosis in diaphragm muscle from mdx mice. PTX treatment had no impact on in vitro diaphragm muscle contractile function. In addition, diaphragm muscle hydroxyproline concentration and the level of type I and III collagen and TGF-beta1 mRNA were unaffected by PTX treatment. These findings do not support the use of PTX as an antifibrotic drug for the treatment of muscular dystrophy.
Assuntos
Diafragma/patologia , Inibidores Enzimáticos/farmacologia , Distrofia Muscular Animal/tratamento farmacológico , Distrofia Muscular de Duchenne/tratamento farmacológico , Pentoxifilina/farmacologia , Animais , Colágeno Tipo I/genética , Colágeno Tipo III/genética , Diafragma/fisiologia , Modelos Animais de Doenças , Fibrose , Hidroxiprolina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos mdx , Contração Muscular/efeitos dos fármacos , Distrofia Muscular Animal/patologia , Distrofia Muscular de Duchenne/patologia , RNA Mensageiro/análise , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta1 , Falha de TratamentoRESUMO
Fibrosis is a common pathological feature observed in muscle from patients with Duchenne muscular dystrophy (DMD). In the dystrophic (mdx) mouse model of DMD, the diaphragm is more severely affected than other skeletal muscles. The level of transforming growth factor-beta1 (TGF-beta1), an inflammatory cytokine, is significantly elevated in mdx diaphragm. However, little is known about the onset of TGF-beta1 messenger ribonucleic acid (mRNA) expression, or which cells express the mRNA. In this study, we characterized the location and time course of expression of TGF-beta1 mRNA in diaphragm from mdx mice. TGF-beta1 mRNA was significantly elevated in mdx diaphragm at 6 and 9 but not 12 weeks of age, and these changes corresponded with changes in type I collagen mRNA and hydroxyproline concentration. Mononucleated cells localized to areas of fiber necrosis highly expressed the TGF-beta1 transcript in mdx diaphragm. Neutralization of TGF-beta1 by decorin administration resulted in a 40% reduction in the level of diaphragm muscle type I collagen mRNA. These findings support a role for TGF-beta1 during the early stages of fibrogenesis in dystrophic diaphragm muscle. Therapeutic interventions aimed at neutralizing this cytokine may be beneficial in slowing the development of fibrosis in DMD.
