RESUMO

INTRODUCTION: Stretching (St) has been used for treating denervated muscles. However, its effectiveness and safety claims require further study. METHODS: Rats were divided into: (1) those with denervated (D) muscles, evaluated 7 or 15 days after sciatic nerve crush injury; (2) those with D muscles submitted to St during 7 or 15 days; and (3) those with normal muscles. Muscle fiber cross-sectional area, serial sarcomere number, sarcomere length, and connective tissue density were measured. MMP-2, MMP-9, TIMP-1, TGF-ß1, and myostatin mRNAs were determined by real-time polymerase chain reaction. MMP-2 and MMP-9 activity was evaluated by zymography. Collagen I was localized using immunofluorescence. RESULTS: St did not prevent muscle atrophy due to denervation, but it increased fibrosis and collagen I deposition at day 15. St also upregulated MMP-9 and TGF-ß1 gene expressions at day 7, and myostatin at day 15. CONCLUSIONS: Stretching denervated muscle does not prevent atrophy, but it increases fibrosis via temporal modulation of TGF-ß1/myostatin and MMP-9 cascades.

Assuntos

Denervação Muscular , Fibras Musculares Esqueléticas/patologia , Exercícios de Alongamento Muscular/efeitos adversos , Atrofia Muscular/patologia , Atrofia Muscular/fisiopatologia , Animais , Modelos Animais de Doenças , Metaloproteinases da Matriz/genética , Metaloproteinases da Matriz/metabolismo , Miostatina/genética , Miostatina/metabolismo , RNA Mensageiro , Ratos , Sarcômeros/patologia , Estatísticas não Paramétricas , Inibidor Tecidual de Metaloproteinase-1/genética , Inibidor Tecidual de Metaloproteinase-1/metabolismo , Fator de Crescimento Transformador beta1/genética , Fator de Crescimento Transformador beta1/metabolismo