Regulation of extracellular matrix elements and sarcomerogenesis in response to different periods of passive stretching in the soleus muscle of rats.

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.

Neuromuscular electrical stimulation alters gene expression and delays quadriceps muscle atrophy of rats after anterior cruciate ligament transection.

INTRODUCTION: Neuromuscular electrical stimulation (NMES) is used to improve quadriceps mass after anterior cruciate ligament (ACL) injury. We studied the effect of NMES on mRNA levels of atrophy genes in the quadriceps muscle of rats after ACL transection. METHODS: mRNA levels of atrogin-1, MuRF-1, and myostatin were assessed by quantitative PCR and the polyubiquitinated proteins by Western blot at 1, 2, 3, 7, and 15 days postinjury. RESULTS: NMES minimized the accumulation of atrogenes and myostatin according to time period. NMES also prevented reduction in muscle mass in all muscles of the ACLES group at 3 days. CONCLUSIONS: Use of NMES decreased the accumulation of atrogenes and myostatin mRNA in the quadriceps muscles, inhibiting early atrophy at 3 days, although it did not prevent atrophy at 7 and 15 days after ACL transection. This study highlights the importance of therapeutic NMES interventions in the acute phase after ACL transection.

Quadriceps muscle atrophy after anterior cruciate ligament transection involves increased mRNA levels of atrogin-1, muscle ring finger 1, and myostatin.

OBJECTIVE: The aim of this study was to assess the mRNA levels of atrogin-1, muscle ring finger 1, and myostatin in rat quadriceps after anterior cruciate ligament (ACL) transection. DESIGN: Wistar rats were randomized into three different groups: ACL (surgery and ACL transection), sham (surgery without ACL transection), and control. Vastus medialis, rectus femoris, and vastus lateralis muscles were harvested at 1, 2, 3, 7, and 15 days after ACL transection. The mRNA levels of atrogin-1, muscle ring finger 1, and myostatin, as well as the ubiquitinated protein content, muscle mass, and cross-sectional area of the muscle fibers, were evaluated. RESULTS: Elevated levels of atrogin-1, muscle ring finger 1, and myostatin mRNA were detected in all tested muscles at most time points. The ubiquitinated protein content was increased at 3 days in the ACL and sham groups. The muscle mass of the ACL group was reduced at 3, 7, and 15 days (vastus lateralis and vastus medialis) and at 7 and 15 days (rectus femoris), whereas it was reduced in the sham group at 3 and 7 days (vastus lateralis and vastus medialis) and at 7 days (rectus femoris). The cross-sectional area of vastus medialis was reduced at 3, 7, and 15 days in the ACL group and at 3 and 7 days in the sham group. The cross-sectional area of the vastus lateralis was reduced at 7 and 15 days in the ACL group and at 7 days in the sham group. Whereas muscle mass and cross-sectional area recovery was noted in the sham group, no recovery was observed in the ACL group. CONCLUSIONS: Quadriceps atrophy after ACL transection involves increased levels of myostatin, atrogin-1, and muscle ring finger 1 mRNA and the accumulation of ubiquitinated protein.

Proposal of non-invasive experimental model to induce scoliosis in rats / Proposta de modelo experimental não-invasivo para indução de escoliose em ratos

BACKGROUND: In the literature, there are several experimental models that induce scoliosis in rats; however, they make use of drugs or invasive interventions to generate a scoliotic curve. OBJECTIVES: To design and apply a non-invasive immobilization model to induce scoliosis in rats. METHODS: Four-week old male Wistar rats (85±3.3g) were divided into two groups: control (CG) and scoliosis (SG). The animals in the SG were immobilized by two vests (scapular and pelvic) made from polyvinyl chloride (PVC) and externally attached to each other by a retainer that regulated the scoliosis angle for twelve weeks with left convexity. After immobilization, the abdominal, intercostal, paravertebral, and pectoral muscles were collected for chemical and metabolic analyses. Radiographic reports were performed every 30 days over a 16-week period. RESULTS: The model was effective in the induction of scoliosis, even 30 days after immobilization, with a stable angle of 28±5º. The chemical and metabolic analyses showed a decrease (p<0.05) in the glycogenic reserves and in the relationship between DNA and total protein reserves of all the muscles analyzed in the scoliosis group, being lower (p<0.05) in the convex side. The values for the Homeostatic Model Assessment of Insulin Resistance indicated a resistance condition to insulin (p<0.05) in the scoliosis group (0.66±0.03), when compared to the control group (0.81±0.02). CONCLUSIONS: The scoliosis curvature remained stable 30 days after immobilization. The chemical and metabolic analyses suggest changes in muscular homeostasis during the induced scoliosis process.

CONTEXTUALIZAÇÃO: Encontram-se na literatura diversos modelos experimentais de indução de escoliose em ratos, porém evidencia-se o uso de drogas ou intervenções invasivas para a geração da curvatura escoliótica. OBJETIVOS: Projetar e aplicar um modelo de imobilização não-invasiva para a indução de escoliose em ratos. MÉTODOS: Ratos Wistar machos com idade inicial de quatro semanas (85±3,3g) foram divididos nos grupos controle (GC) e escoliose (GE). Os animais do GE foram imobilizados por dois cintos (escapular e pélvico) de policloreto de vinila (PVC), interligados externamente por um limitador que regulava o ângulo da escoliose durante 12 semanas, com convexidade à esquerda. Após a imobilização, os músculos abdominais, intercostais, paravertebrais e peitorais bilateralmente foram coletados para as análises químio-metabólicas. Os registros radiológicos foram realizados a cada 30 dias, num total de 16 semanas. RESULTADOS: O modelo foi eficiente e eficaz na indução da escoliose, mesmo após 30 dias da desmobilização, mantendo um ângulo estável de 28±5 graus. Quanto às análises químio-metabólicas, observou-se diminuição (p<0,05) nas reservas glicogênicas e na relação proteína total/DNA de todos os músculos analisados do GE, sendo menores (p<0,05) no lado da convexidade. Os valores do HOMA-IR indicaram um quadro de resistência à insulina (p<0,05) no GE (0,66±0,03) quando comparado ao GC (0,81±0,02). CONCLUSÕES: A curvatura escoliótica manteve-se estável após 30 dias da desmobilização, e as alterações químio-metabólicas sugeriram a ocorrência de modificações na homeostasia muscular durante o processo indutor da escoliose.

Proposal of non-invasive experimental model to induce scoliosis in rats.

BACKGROUND: In the literature, there are several experimental models that induce scoliosis in rats; however, they make use of drugs or invasive interventions to generate a scoliotic curve. OBJECTIVES: To design and apply a non-invasive immobilization model to induce scoliosis in rats. METHODS: Four-week old male Wistar rats (85±3.3g) were divided into two groups: control (CG) and scoliosis (SG). The animals in the SG were immobilized by two vests (scapular and pelvic) made from polyvinyl chloride (PVC) and externally attached to each other by a retainer that regulated the scoliosis angle for twelve weeks with left convexity. After immobilization, the abdominal, intercostal, paravertebral, and pectoral muscles were collected for chemical and metabolic analyses. Radiographic reports were performed every 30 days over a 16-week period. RESULTS: The model was effective in the induction of scoliosis, even 30 days after immobilization, with a stable angle of 28±5º. The chemical and metabolic analyses showed a decrease (p<0.05) in the glycogenic reserves and in the relationship between DNA and total protein reserves of all the muscles analyzed in the scoliosis group, being lower (p<0.05) in the convex side. The values for the Homeostatic Model Assessment of Insulin Resistance indicated a resistance condition to insulin (p<0.05) in the scoliosis group (0.66±0.03), when compared to the control group (0.81±0.02). CONCLUSIONS: The scoliosis curvature remained stable 30 days after immobilization. The chemical and metabolic analyses suggest changes in muscular homeostasis during the induced scoliosis process.

Stretching and electrical stimulation reduce the accumulation of MyoD, myostatin and atrogin-1 in denervated rat skeletal muscle.

Denervation causes muscle atrophy and incapacity in humans. Although electrical stimulation (ES) and stretching (St) are commonly used in rehabilitation, it is still unclear whether they stimulate or impair muscle recovery and reinnervation. The purpose of this study was to evaluate the effects of ES and St, alone and combined (ES + St), on the expression of genes that regulate muscle mass (MyoD, Runx1, atrogin-1, MuRF1 and myostatin), on muscle fibre cross-sectional area and excitability, and on the expression of the neural cell adhesion molecule (N-CAM) in denervated rat muscle. ES, St and ES + St reduced the accumulation of MyoD, atrogin-1 and MuRF1 and maintained Runx1 and myostatin expressions at normal levels in denervated muscles. None of the physical interventions prevented muscle fibre atrophy or N-CAM expression in denervated muscles. In conclusion, although ES, St and ES + St changed gene expression, they were insufficient to avoid muscle fibre atrophy due to denervation.