RESUMO
Stretching is a common method used to prevent muscle shortening and improve limited mobility. However, the effect of different time periods on stretching-induced adaptation of the extracellular matrix and its regulatory elements have yet to be investigated. We aimed to evaluate the expression of fibrillar collagens, sarcomerogenesis, metalloproteinase (MMP) activity and gene expression of the extracellular matrix (ECM) regulators in the soleus (SOL) muscle of rats submitted to different stretching periods. The soleus muscles were submitted to 10 sets of passive stretching over 10 (St 10d) or 15 days (St 15d) (1 min per set, with 30 seconds' rest between sets). Sarcomerogenesis, muscle cross-sectional area (CSA), and MMP activity and mRNA levels in collagen (type I, III and IV), connective tissue growth factor (CTGF), growth factor-beta (TGF-ß), and lysyl oxidase (LOX) were analyzed. Passive stretching over both time periods mitigated COL-I deposition in the SOL muscle of rats. Paradoxically, 10 days of passive stretching induced COL-I and COL-III synthesis, with concomitant upregulation of TGF-ß1 and CTGF at a transcriptional level. These responses may be associated with lower LOX mRNA levels in SOL muscles submitted to 10 passive stretching sessions. Moreover, sarcomerogenesis was observed after 15 days of stretching, suggesting that stretching-induced muscle adaptations are time-dependent responses.
Assuntos
Matriz Extracelular/metabolismo , Exercícios de Alongamento Muscular/métodos , Músculo Esquelético/fisiologia , Sarcômeros/metabolismo , Animais , Fator de Crescimento do Tecido Conjuntivo/genética , Fator de Crescimento do Tecido Conjuntivo/metabolismo , Colágenos Fibrilares/genética , Colágenos Fibrilares/metabolismo , Masculino , Metaloproteinase 2 da Matriz/metabolismo , Músculo Esquelético/metabolismo , Proteína-Lisina 6-Oxidase/genética , Proteína-Lisina 6-Oxidase/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos Wistar , Fatores de Tempo , Fator de Crescimento Transformador beta1/genética , Fator de Crescimento Transformador beta1/metabolismoRESUMO
INTRODUCTION: It is not clear if electrical stimulation (ES) can affect muscle reinnervation. This study aimed to verify if ES affects neuromuscular recovery after nerve crush injury in rats. METHODS: Denervated muscles were electrically stimulated daily for 6 or 14 days. Neuromuscular performance and excitability, and muscle morphology were determined. Muscle trophism markers (atrogin-1, MuRF-1, and myoD), as well as neuromuscular junction (NMJ) organization (muscle-specific receptor tyrosine kinase [MuSK], cytoplasmic protein downstream of kinase-7 [Dok-7], nicotinic ACh receptor [nAChR], and neural cell adhesion molecule [N-CAM]) were assessed. RESULTS: ES impaired neuromuscular recovery at day 14 postdenervation. Muscle hypoexcitability was accentuated by ES at 6 and 14 days postdenervation. Although ES reduced the accumulation of atrogin-1, MuRF1, and myoD mRNAs, it increased muscle atrophy. Gene expression of MuSK, Dok-7, nAChR, and the content of N-CAM protein were altered by ES. DISCUSSION: ES can delay the reinnervation process by modulating factors related to NMJ stability and organization, and inducing dysfunction, hypoexcitability, and muscle atrophy. Muscle Nerve 56: E108-E118, 2017.
