NEDD4-1 deficiency impairs satellite cell function during skeletal muscle regeneration

BACKGROUND: Satellite cells are tissue-specific stem cells primarily responsible for the regenerative capacity of skeletal muscle. Satellite cell function and maintenance are regulated by extrinsic and intrinsic mechanisms, including the ubiquitin-proteasome system, which is key for maintaining protein homeostasis. In this context, it has been shown that ubiquitin-ligase NEDD4-1 targets the transcription factor PAX7 for proteasome-dependent degradation, promoting muscle differentiation in vitro. Nonetheless, whether NEDD4-1 is required for satellite cell function in regenerating muscle remains to be determined. RESULTS: Using conditional gene ablation, we show that NEDD4-1 loss, specifically in the satellite cell population, impairs muscle regeneration resulting in a significant reduction of whole-muscle size. At the cellular level, NEDD4-1-null muscle progenitors exhibit a significant decrease in the ability to proliferate and differentiate, contributing to the formation of myofibers with reduced diameter. CONCLUSIONS: These results indicate that NEDD4-1 expression is critical for proper muscle regeneration in vivo and suggest that it may control satellite cell function at multiple levels.

Effect of Thymoquinone on skeletal muscle regeneration via assessment of Pax-7 and Myo-D expression in the DMBA-treated hamster pouch / Efeito da Timoquinona na regeneração muscular esquelética através da avaliação da expressão das proteínas Pax-7 e Myo-D em bolsa jugal de hamsters tratados com DMBA

Objective: Pax-7 and Myo-D regulate satellite cells' activation and differentiation, thus muscle regeneration following damage. This research aimed to investigate the effect of Thymoquinone (TQ) on skeletal muscle regeneration following 7,12-dimethylbenz-(a)-anthracene (DMBA)-induced injury in the hamster buccal pouch via immunohistochemical assessment of Pax-7 and Myo-D expression. Material and Methods: 65 male golden Syrian hamsters were divided into 3 groups: Group 1: (n=5) received no treatment. Group 2: (n=20) served as a positive control. The left buccal pouches were painted with the carcinogen 3/week/ 6weeks. Group 3: (n=40) were subdivided into two equal sub-groups as follows: Group 3a: (n=20) were given one i.p. TQ injection. Group 3b: (n=20) were given two i.p. TQ injections. Five animals from each group (2 and 3) were euthanized at 24, 48 hrs, one, and two weeks after the last injection. A blood sample (2 ml) was withdrawn for assessment of TNF-α levels in serum. Serial sections of the pouches were examined histologically (H&E), and immunohistochemically (IHC) for the detection of Pax-7 and Myo-D proteins. Results: double i.p injections of TQ resulted in a significant elevation in the level of TNF-α from the second-day post-injection with a progressive formation of the muscle fibers (MFs) and mononuclear cells (MNCs) around the deeper blood vessels. At 14 days, no statistically significant difference was found between this group and group '2', while the difference remained significant compared to groups '1' and '3a'. The muscle fibers were more mature and compact. IHC results showed positive expression of the perivascular mononuclear cells (MNCs) to both Pax-7 and Myo-D with positive reactivity of the peripheral nuclei of muscle fibers to Pax-7 compared to the negative reaction in the positive control group. Conclusion: early and two TQ injections had a promising effect on the induction of striated muscle regeneration, mainly by non-myogenic stem cells (AU)

Objetivo: Pax-7 e Myo-D regulam a ativação e diferenciação de células satélites durante a regeneração muscular pós-trauma. Assim, objetivamos investigar o efeito da timoquinona (TQ) na regeneração muscular esquelética após injúria causada por 7,12 dimetilbenzantraceno (DMBA) em bolsa jugal de hamsters, através da análise imuno-histoquímica de Pax-7 e Myo-D. Material e Métodos: 65 hamsters-sírios machos foram divididos em 3 grupos: Grupo 1: (n=5) controle negativo, sem tratamento. Grupo 2: (n=20) controle positivo. A bolsa jugal do lado esquerdo recebeu aplicação do DMBA por 3 e 6 semanas. Grupo 3: (n=40) receberam aplicação de DMBA e foram então subdivididos em: Grupo 3a: (n=20) que recebeu 1 injeção intraperitoneal (ip) de TQ e Grupo 3b: (n=20) que recebeu duas injeções ip de TQ. Cinco animais dos grupos 2 e 3 foram eutanasiados em 24 horas, 48 horas, 7 dias e 14 dias após a administração de DMBA e da última injeção de TQ. Amostras de sangue (2 ml) foram coletadas para avaliação dos níveis séricos de TNF-α. Cortes seriados da bolsa jugal dos animais foram analisados histologicamente (H&E), e através de imunohistoquimica (IHC) para avaliação das proteínas Pax-7 e Myo-D. Resultados: duas injeções ip de TQ aumentaram os níveis séricos TNF-α à partir do segundo dia pós-administração com formação progressiva de fibras musculares (MFs) e células mononucleares (MNCs) ao redor dos vasos sanguíneos. No dia 14, não houve diferença estatística entre o grupo 3b e o grupo 2, enquanto a diferença permaneceu entre o grupo 1 e 3a. As MFs apresentavam-se mais maduras e compactas. A IHC mostrou expressão de Pax-7 e Myo-D nas MNCs ao redor dos vasos, e houve expressão nuclear de Pax-7 nas MFs no grupo 2. Conclusão: ambos regimes de administração do TQ, 1 ou 2 aplicações ip, apresentaram efeito promissor na indução da regeneração muscular esquelética, principalmente nas células não-miogênicas.(AU)

Anti-Inflammatory Effect of Omega-3 Fish Oil Accelerates MyoD and Myogenin Expressions Following Rat Exercise-Induced Muscle Injury Model in a Dose-Dependent Manner

@#Introduction: Exercise-induced muscle injury stimulates production of proinflammatory cytokines, e.g., TNF-α, resulting in impaired satellite-cell-dependent muscle regeneration. Omega-3 fatty acids emerge to possess anti-inflammatory properties. This study aims to analyze the effect of omega-3 fish oil administration on the levels of TNF-α, MyoD and myogenin expressions of satellite cells after injury. Methods: Twenty-nine adult male Wistar rats were randomized into five groups. Except for control groups, the rats underwent single bout of downhill running exercise and three groups were given low-to-high doses of omega-3 fish oil administration 2 hours after exercise. Blood samples were collected after 24 hours to measure the concentration of TNF-α using ELISA and then the soleus muscles were surgically removed after 72 hours to measure mRNA expressions of MyoD and myogenin using RT-PCR. Results: The results showed lower serum levels of TNF-α (166.83 ± 16.15 vs. 132.83 ± 25.44, 125.00 ± 17.26, 99.66 ± 32.00 pg/mL) and higher expressions of MyoD (0.47 ± 0.19 vs. 0.64 ± 0.20, 1.17 ± 0.16, 1.07 ± 0.14) and myogenin (0.45 ± 0.10 vs. 1.82 ± 0.35, 1.50 ± 0.34, 0.76 ± 0.20) in groups given low-to-high doses of omega-3 fish oil supplementation, respectively, compared to exercise group with no supplement at 72 hours after exercise. Conclusion: Our study suggests that omega-3 fish oil supplementation following muscle injury may accelerate myogenin expression and a low dose of supplementation achieves optimal effect in promoting muscle regeneration. .

Engraftment of human induced pluripotent stem cell-derived myogenic progenitors restores dystrophin in mice with duchenne muscular dystrophy

BACKGROUND: Duchenne muscular dystrophy (DMD) is a devastating genetic muscular disorder with no effective treatment that is caused by the loss of dystrophin. Human induced pluripotent stem cells (hiPSCs) offer a promising unlimited resource for cell-based therapies of muscular dystrophy. However, their clinical applications are hindered by inefficient myogenic differentiation, and moreover, the engraftment of non-transgene hiPSC-derived myogenic progenitors has not been examined in the mdx mouse model of DMD. METHODS: We investigated the muscle regenerative potential of myogenic progenitors derived from hiPSCs in mdx mice. The hiPSCs were transfected with enhanced green fluorescent protein (EGFP) vector and defined as EGFP hiPSCs. Myogenic differentiation was performed on EGFP hiPSCs with supplementary of basic fibroblast growth factor, forskolin, 6-bromoindirubin-3'-oxime as well as horse serum. EGFP hiPSCs-derived myogenic progenitors were engrafted into mdx mice via both intramuscular and intravenous injection. The restoration of dystrophin expression, the ratio of central nuclear myofibers, and the transplanted cells-derived satellite cells were accessed after intramuscular and systemic transplantation. RESULTS: We report that abundant myogenic progenitors can be generated from hiPSCs after treatment with these three small molecules, with consequent terminal differentiation giving rise to mature myotubes in vitro. Upon intramuscular or systemic transplantation into mdx mice, these myogenic progenitors engrafted and contributed to human-derived myofiber regeneration in host muscles, restored dystrophin expression, ameliorated pathological lesions, and seeded the satellite cell compartment in dystrophic muscles. CONCLUSIONS: This study demonstrates the muscle regeneration potential of myogenic progenitors derived from hiPSCs using non-transgenic induction methods. Engraftment of hiPSC-derived myogenic progenitors could be a potential future therapeutic strategy to treat DMD in a clinical setting.

The effect of icing treatment on recovery process of damaged muscle in the rat / 体力科学

<p>Although icing treatment has been well accepted as aftercare in sports fields, the detailed mechanisms of the treatment is not fully understood. In this study, we investigated the effect of icing treatment on the recovery process of rat plantaris muscles with artificially induced muscle damage. Sixty male Wistar rats (8-weeks-old) were randomly assigned to three groups; control (CTL), bupivacaine-injected (BPVC), and icing treatment after BPVC (ICE). Icing treatment was applied for 20 min immediately after BPVC, and the treatment was used once per day for 3 days. The plantaris muscles were removed at 3, 7, 15, and 28 days after the muscle damage, then immunohistochemical and real time RT-PCR analysis were performed. In histochemical analysis, although significant changes were found in the relative muscle weight, cross-sectional area of muscle fiber, percentage of muscle fiber with central nuclei, and expressed immature myosin heavy chain isoforms after muscle damage, as compared to the CTL group, no differences were found between BPVC and ICE groups. In mRNA expression analysis, the ICE group had a significantly lower value of MyoD than the BPVC group at 3 days after the damage. Expression of IL-6 mRNA, which relates to muscle inflammation, indicated significantly higher value in BPVC, but not in ICE, than CTL groups at 7days after the damage. Furthermore, BKB₂ receptor, which relates to acute muscle soreness, indicated a significantly higher expression in BPVC than ICE groups at 3 days after the damage. These results suggest that icing treatment is effective to suppress muscle inflammation and soreness at an early stage of recovery from damage, but not effective for muscle regeneration at a later stage.</p>

Local inhibition of nitrergic activity in tenotomized rats accelerates muscle regeneration by increasing fiber area and decreasing central core lesions

Muscular atrophy is a progressive degeneration characterized by muscular proteolysis, loss of mass and decrease in fiber area. Tendon rupture induces muscular atrophy due to an intrinsic functional connection. Local inhibition of nitric oxide synthase (NOS) by Nω-nitro-L-arginine methyl ester (L-NAME) accelerates tendon histological recovery and induces functional improvement. Here we evaluate the effects of such local nitrergic inhibition on the pattern of soleus muscle regeneration after tenotomy. Adult male Wistar rats (240 to 280 g) were divided into four experimental groups: control (n=4), tenotomized (n=6), vehicle (n=6), and L-NAME (n=6). Muscular atrophy was induced by calcaneal tendon rupture in rats. Changes in muscle wet weight and total protein levels were determined by the Bradford method, and muscle fiber area and central core lesion (CCL) occurrence were evaluated by histochemical assays. Compared to tenotomized (69.3±22%) and vehicle groups (68.1%±17%), L-NAME treatment induced an increase in total protein level (108.3±21%) after 21 days post-injury. A reduction in fiber areas was observed in tenotomized (56.3±1.3%) and vehicle groups (53.9±3.9%). However, L-NAME treatment caused an increase in this parameter (69.3±1.6%). Such events were preceded by a remarkable reduction in the number of fibers with CCL in L-NAME-treated animals (12±2%), but not in tenotomized (21±2.5%) and vehicle groups (19.6±2.8%). Altogether, our data reveal that inhibition of tendon NOS contributed to the attenuation of atrophy and acceleration of muscle regeneration.

Regulação e ativação das células satélites durante a regeneração muscular / Regulation and activation of satellite cells during musculoskeletal regeneration

Os avanços da biologia molecular, biologia celular e genética tem melhorado muito a nossa compreensão da biologia do músculo esquelético, demonstrando que as características biológicas das células satélites (CSs) são fundamentais no processo de regeneração muscular. O potencial terapêutico destas células vem sendo discutido pela literatura, por isso o entendimento do metabolismo e a regulação das células precursoras das fibras musculares merece atenção. Assim, o objetivo desta revisão narrativa é apresentar aspectos relacionados aos fatores de regulação das células satélites durante o processo de regeneração do músculo esquelético. A regeneração do músculo esquelético é um processo orquestrado que envolve a ativação e diferenciação das CSs. As interações celulares ocorrem com os diversos fatores miogênicos, de crescimento e hormonais. Entre eles destacam-se o HGF (fator de crescimento hepatocitário), IGF (fator de crescimento semelhante a insulina), MRFs (fatores regulatórios miogênicos), IL-6 (interleucina-6), VEGF (fator de crescimento vascular endotelial), Myf5 (fator miogênico 5), MRf4 (fator miogênico 4), MyoD (fator miogênico 1), androgênios e outros hormônios como a insulina. Todos estes fatores são dinâmicos e podem levar a uma maior compreensão da participação dessas células nos processos de regeneração tecidual. A interação com essas células promove ações positivas e negativas, levando a ativação ou inibição de suas atividades. O processo inflamatório e os fatores de crescimento atuam positivamente na diferenciação e proliferação celular. Entretanto, anti-inflamatórios, glicocorticoides e hormônios tireoidianos (T3) em excesso podem alterar o ciclo dessas células essenciais para o remodelamento tecidual. O entendimento de suas relações com as alterações fenotípicas e a sinalização que induzem modificações musculares é importante para o planejamento de estratégias de reabilitação e futuras terapias celulares.(AU)

The advance of molecular biology, cell biology and genetics has greatly improved our understanding of skeletal muscle biology, demonstrating that the biological characteristics of satellite cells (SCs) are essential in muscle regeneration. The therapeutic potential of these cells has been discussed in the literature, so the understanding of metabolism and regulation of precursor cells of the muscle fibers requires attention. The aim of this narrative review is to show aspects related to the regulatory factors of satellite cells during the process of skeletal muscle regeneration. Regeneration of skeletal muscle is an orchestrated process involving the activation and differentiation of SCs. The cellular interactions occur with various myogenic factors, growth factors and hormones. Stand out from HGF (Hepatocyte growth factor), IGF (insulin-like growth factor), MRFs (myogenic regulatory factors), IL-6 (interleukin-6), VEGF (vascular endothelial growth factor), Myf5 (myogenic factor 5), MRF4 (myogenic factor 4), MyoD (myogenic factor 1), androgens and other hormones such as insulin. All these factors are dynamic and can lead to a greater understanding of the role of cells in tissue regeneration processes. The interaction with these cells promotes positive and negative actions, leading to activation or inhibition of its activities. The inflammation and growth factors act positively on cell differentiation and proliferation. However, antiinflammatory, glucocorticoid and excess thyroid hormone (T3) may change the cycle of these cells essential to tissue remodeling. Understanding their relationship with the phenotypic changes and the signs inducing muscle changes is important for planning rehabilitation strategies and future cell therapies.(AU)

Effects of low-intensity pulsed ultrasound on injured skeletal muscle

BACKGROUND: Low-intensity pulsed ultrasound (LIPUS) has been shown to stimulate tissue metabolism and accelerate muscle healing. However, the optimal parameters in the use of LIPUS are still not clear. OBJECTIVE: The aim of this study was to analyze the effects of LIPUS on muscle healing in rats subjected to a cryolesion. METHOD: Twenty rats were divided into the following groups: an injured control group (CG) and an injured treated group (TG). Both groups were divided into 2 sub-groups (n=5 each) that were sacrificed 7 and 13 days post-surgery. Treatments were started 24 hours after the surgical procedure and consisted of 3 or 6 sessions. After euthanasia, the muscles were submitted to standard histological procedures. RESULTS: Qualitative analyses were based on morphological assessments of the muscle. The histopathological analysis on day 7 revealed that the muscles in the CG and the TG presented an intense inflammatory infiltrate, a large necrotic area and a disorganized tissue structure. After 13 days, both the CG and the TG had granulation tissue and newly formed fibers. The TG presented a more organized tissue structure. The quantitative analysis of collagen indicated similar findings among the groups, although the qualitative analysis revealed a better organization of collagen fibers in the TG at 13 days. The immunohistochemical analysis indicated that, at both time points, the expression of cyclooxygenase-2 was upregulated in the TG compared to the CG. CONCLUSIONS: LIPUS used as a treatment for muscle injury induced a more organized tissue structure at the site of the injury and stimulated the expression of COX-2 and the formation of new muscle fibers. .

Pulsed ultrasound therapy accelerates the recovery of skeletal muscle damage induced by Bothrops jararacussu venom

We studied the effect of pulsed ultrasound therapy (UST) and antibothropic polyvalent antivenom (PAV) on the regeneration of mouse extensor digitorum longus muscle following damage by Bothrops jararacussu venom. Animals (Swiss male and female mice weighing 25.0 ± 5.0 g; 5 animals per group) received a perimuscular injection of venom (1 mg/kg) and treatment with UST was started 1 h later (1 min/day, 3 MHz, 0.3 W/cm², pulsed mode). Three and 28 days after injection, muscles were dissected and processed for light microscopy. The venom caused complete degeneration of muscle fibers. UST alone and combined with PAV (1.0 mL/kg) partially protected these fibers, whereas muscles receiving no treatment showed disorganized fascicules and fibers with reduced diameter. Treatment with UST and PAV decreased the effects of the venom on creatine kinase content and motor activity (approximately 75 and 48%, respectively). Sonication of the venom solution immediately before application decreased the in vivo and ex vivo myotoxic activities (approximately 60 and 50%, respectively). The present data show that UST counteracts some effects of B. jararacussu venom, causing structural and functional improvement of the regenerated muscle after venom injury.

Effect of Citrus aurantium L. essential oil on muscle regeneration in mdx mice / Efecto del aceite esencial de Citrus aurantium L. en la regeneración muscular en ratones mdx

Duchenne muscular dystrophy (DMD) is a severe X-linked recessive disorder characterized by the progressive loss of muscular strength. Mdx mutant mice show a marked deficiency in dystrophin, which was related to muscle membrane stability. The aim of this study was to verify the possible protective anti-inflammatory effect of citrus oil on mdx muscle fibers. Thus, adult male and female mdx mice (014/06-CEEA) were divided into control and citrus-treated. After 60 days of treatment, one ml of blood was collected for creatine kinase (CK) test. Diaphragm, sternomastoideus, anterior tibial and gastrocnemius muscles were removed and processed according to histological routine methods. The observed alterations indicate a direct effect of citrus. Recent studies have improved the diagnosis of muscular diseases but with no definitions of efficient treatments. Intervention with several therapies is important to many patients presenting muscular dystrophy, which enables them to live longer and be more active, while there is no development of gene therapies.

La distrofia muscular de Duchenne (DMD) es una enfermedad grave ligada al cromosoma X, trastorno recesivo que se caracteriza por la pérdida progresiva de fuerza muscular. Mdx ratones mutantes muestran una marcada deficiencia en la distrofina, que está relacionada con la estabilidad de la membrana muscular. El objetivo de este estudio fue comprobar el posible efecto protector, antiinflamatorio del aceite de cítricos en las fibras musculares mdx. Los ratones mdx adultos machos y hembras (014/06-CEEA) se dividieron en control y cítricos tratados. Después de 60 días de tratamiento, un ml de sangre fue recogida para cuantificar la creatina quinasa (CK) de prueba. Fueron retirados y procesados los músculos diafragma, esternomastoideo, tibial anterior y gastrocnemio de acuerdo con los métodos de rutina histológica. Las alteraciones observadas indican un efecto directo de los cítricos. Estudios recientes han mejorado el diagnóstico de enfermedades musculares, pero sin definiciones de tratamientos eficaces. Intervención con varias terapias es importante para muchos pacientes que presentan distrofia muscular, lo que les permite vivir más y ser más activos, mientras no exista desarrollo de terapias génicas.

Bex1 Participates in Muscle Regeneration by Regulating Myogenic Satellite Cell Differentiation / 한국실험동물학회지

Bex1 protein is upregulated in regenerating muscle and interacts with calmodulin, a Ca2+-binding protein involved in cell cycle regulation. Following cardiotoxin-induced injury the regenerating muscle of Bex1 knock-out mice exhibits prolonged cell proliferation and delayed cell differentiation compared to wild-type mice. To gain insight into this process, we compared the regenerating myogenic morphologies of Bex1 knock-out and wild-type mice at several time points. Bex1-positive cells were identified by double immunofluorescence staining. These studies demonstrated that a population of cells that are Bex1-positive after injury are c-Met/basal lamina-positive and Mac-1-negative indicating that they are derived from at least a subset of myogenic progenitor/satellite cells but not invading immune cells. In addition, in regenerating muscle, Bex1 co-localizes with calmodulin in the cytoplasm of the late myoblast or early myotube stage of myogenesis. These results suggest that Bex1 participates in muscle regeneration through the regulation of satellite cell proliferation and differentiation by its interaction with calmodulin. Current studies of Bex1 may provide a new molecular tool for the identification of activated satellite cell and open the way to new or improved therapeutic regimens against progressive muscular atrophy.

Bex1 Participates in Muscle Regeneration by Regulating Myogenic Satellite Cell Differentiation / 한국실험동물학회지

Bex1 protein is upregulated in regenerating muscle and interacts with calmodulin, a Ca2+-binding protein involved in cell cycle regulation. Following cardiotoxin-induced injury the regenerating muscle of Bex1 knock-out mice exhibits prolonged cell proliferation and delayed cell differentiation compared to wild-type mice. To gain insight into this process, we compared the regenerating myogenic morphologies of Bex1 knock-out and wild-type mice at several time points. Bex1-positive cells were identified by double immunofluorescence staining. These studies demonstrated that a population of cells that are Bex1-positive after injury are c-Met/basal lamina-positive and Mac-1-negative indicating that they are derived from at least a subset of myogenic progenitor/satellite cells but not invading immune cells. In addition, in regenerating muscle, Bex1 co-localizes with calmodulin in the cytoplasm of the late myoblast or early myotube stage of myogenesis. These results suggest that Bex1 participates in muscle regeneration through the regulation of satellite cell proliferation and differentiation by its interaction with calmodulin. Current studies of Bex1 may provide a new molecular tool for the identification of activated satellite cell and open the way to new or improved therapeutic regimens against progressive muscular atrophy.

Effect of Exercise Training on Histochemical Muscle Recovery after Sciatic Nerve Crush in Rat / 체질인류학회지

It is constant controversy that exercise influence muscle regeneration in peripheral neuropathy. The aim of this experiment is to show that treadmill running exercise under well-controlled conditions is to improve of regeneration in rat gastrocnemius muscles after sciatic nerve crushing injury. Male Sprague-Dawley rats (1 month old, weight 150~180 g) were submitted to bouts of exercise on a treadmill up a 10 degrees decline and speed is 20 m/min for 60 min per day and gastrocnemius muscles were analysed at different exercise periods (5, 10, 15, 20 and 40 days) by immunohistochemistry in comparison with injured non-exercised muscles. Rats were sacrificed at 12th (5 days exercise), 19th (10 days exercise), 26th (15 days exercise), 33rd day (20 days exercise), 61st day (40 days exercise) after sciatic nerve crushing injury. It showed that type II myofibers (target fibers) on center area had reinnervation at sciatic nerve crush injury at 26th day in exercise rats, as at 33rd day appeared giant type II myofibers, myofibers grouping observed in regenerative muscle character, component ratio of closed normal muscle showed at 61st day. Giant type II myofibers showed at 33rd day in non-exercise rats, however did not nearly normal muscle at 61st day. Therefore we concluded that treadmill running exercise is able to improve regeneration processes in gastrocnemius muscles after sciatic nerve crushing injury of rats.

Age Related Local Growth Factors Affect Muscle Regeneration in Distraction Osteogenesis / 대한정형외과학회잡지

PURPOSE: To evaluate the effect of growth factors on muscle regeneration related to the distraction rate and age on bone distraction. MATERIALS AND METHODS: This study examined the effects in the tibialis anterior (TA) and soleus muscles after tibial bone distraction in 6 young and mature rats. The young and old rats were 6 weeks old (average 250 mg) and 6 months old (average 450 mg), respectively. In all rats, the right tibial bone was distracted, and the left was used as a control group. The development pattern of IGF-1, PDGF, bFGF was assessed using immunohistochemical techniques. The distraction rate was 0.7 mm/day (2 times) and the total extension ratio was 20% in all cases. RESULTS: In the TA muscle, the development of IGF-1 and PDGF was inversely proportional to age (p<0.05). In the soleus muscle, the development of IGF-1 and PDGF was higher in the old rats but the difference was not statistically significant. BrdU positive cells were expressed in the myosatellite cells and the basement membrane of myocytes. IGF-1 and PDGF was also expressed in myosatellite cells but bFGF was not. bFGF facilitated bone regeneration but the mechanism for its effects on muscle regeneration were not identified. CONCLUSION: Distraction osteogenesis facilitates the release of growth factors. Immature muscles adapt to the distraction but mature muscles do not. This suggests that mature muscles are less able to activate the proliferation and differentiation of myosatellite cells and the local release of growth factors when bone distraction is performed.

Effect of Local Growth Factors on Muscle Regeneration in Distraction Osteogenesis / 대한정형외과학회잡지

PURPOSE: This study evaluated the influence of growth factors on muscle regeneration when the bone is distracted, relative to the distraction rate. MATERIALS AND METHODS: The influence of bone distraction on the tibialis anterior and soleus muscles of 6-month-old Sprague-Dawley rats was evaluated. IGF-I, PDGF, and bFGF expression were used as growth markers. The rats were divided into two groups containing six rats each. In each group, the right tibia was distracted and the left tibia was used as the control. The distraction rates were 0.35 and 0.7 mm/day in the respective groups. RESULTS: For the tibialis anterior, the level of IGF-I expression in the group distracted at 0.35 mm/day was significantly higher (p0.05). In the tibialis anterior, PDGF expression was higher in the group distracted at 0.7 mm/day but this increase was not significant (p=0.145). In the soleus, the expression level was lower in the group distracted at 0.7 mm/day but the difference was not significant (p>0.05). bFGF was not expressed in the tibialis anterior or soleus. CONCLUSION: Bone distraction promotes the release of growth factors but the amount of growth factor released in mature muscle decreases in proportion to the distraction rate. bFGF is not related to myoblast proliferation and differentiation. Moreover, the amount of muscle growth decreases with increasing rate of muscle distraction.

Relationship between Utrophin and Regenerating Muscle Fibers in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a dystrophinopathy, and its associated gene is located on Xp21. Moreover, utrophin, a recently identified structural homologue of dystrophin is reported to be up-regulated in DMD. In order to investigate the association between utrophin and muscle regeneration in DMD, an immunohistochemical study using antibodies to utrophin, dystrophin, vimentin and desmin was carried out in 17 cases of DMD, 3 cases of polymyositis and 1 case of dermatomyositis. Dystrophin was negative in almost all cases of DMD, but positive in all cases of inflammatory myopathy (IM). Utrophin was positive in 94.0% of DMD and in 75.0% of IM. 36.4% of the myofibers were positive in DMD, as compared to 10.5% in IM (p=0.001). In both groups, utrophin positivity was present most commonly in small regenerating fibers (p=0.001, 0.013). Vimentin and desmin were intensely positive in regenerating fibers in all cases of DMD and IM. 34.4% and 35.4% of myofibers were positive for vimentin and desmin in DMD, as compared to 21.8% and 20.9% in IM (p=0.001, 0.001). In both groups, vimentin and desmin positivity were present most commonly in small regenerating fibers (p=0.001, 0.001). The staining intensities of utrophin, vimentin and desmin were also higher in small regenerating fibers. These results show that utrophin up-regulation is regeneration-associated, and that it is proportional to the quantity of regenerating myofibers, but is not specific for DMD.

Phenotypic Changes of Intermediate Filament Proteins during Degeneration and Regeneration of Rat Leg Muscles following Sciatic Nerve Injury / 대한정형외과연구학회지

PURPOSE: The intermediate filament proteins, desmin and vimentin, are specific components of the cytoskeleton of striated muscle fibers and of mononuclear cells of mesenchymal origin including myoblasts, respectively. Desmin has also been found in presumptive myoblasts of mammals. The aim of this experiment was attempted to observe the phenotypic changes of intermediate filaments in skeletal muscle fibers during early stages of sciatic nerve crushing injury. MATERIALS AND METHODS: The sciatic nerves of rats were surgically crushed by hemostat and serial cryosections of soleus and extensor digitorum longus(EDL) muscles were prepared at 2, 4, 6, 8, 10, 15, 20 and 27 days after nerve injury. Serial cryosections were immunolabelled with desmin, vimentin and laminin and were histochemically reacted with NADH-TR. RESULTS: 1) Firstly, desmin positive fibers were appeared in fast-twitch type C fibers of both muscles at 6 days after nerve crushing, but were not reacted for vimentin. 2) Co-expressions of desmin and vimentin were firstly detected in fast-twitch type A fibers of EDL muscles at 8 days after nerve injury. In soleus muscles, co-expressions of desmin and vimentin were firstly seen in slow-twitch type B fibers at 10 days after nerve injury. Many atrophic fibers, that contained several central nuclei like myotubes and co-expressed desmin and vimentin, were appeared in EDL muscles at 10 days after nerve injury. Although whole regions of fibers were regenerated in EDL muscles, only peripheral regions of fibers were regenerated in soleus muscles at 15 days after nerve injury. Many atrophic fibers, co-expressed of desmin and vimentin, were appeared in EDL muscles at 20 days after nerve injury. These whole fibers represented various degrees of regenerating stages. Most of mature fibers containing several central nuclei, only expressed vimentin slightly, were seen in soleus muscles at 20 days after nerve injury. Most fibers of both muscles were matured at 27 days after nerve injury, but some fibers in EDL muscles were still in processing of degeneration and regeneration. No expressions of desmin and vimentin indicated that muscle fibers were almostly matured in soleus muscles at 27 days after nerve injury. 3) Targetoid or target fibers which informed reinnervation, were appeared firstly in soleus muscles at 20 days and were seen in both muscles at 27 days after nerve injury. All targetoid and target fibers were type B fibers. CONCLUSION: Desmin was revealed in processes of degeneration and regeneration and vimentin was appealed in regeneration process. At the same time, positive immunoreactivity of desmin and vimentin showed specific differences in degree of degeneration and regeneration according to different muscles and muscle fibers.

Phenotypic Changes of Intermediate Filament Proteins during Degeneration and Regeneration of Rat Leg Muscles following Sciatic Nerve Injury / 대한정형외과연구학회지

PURPOSE: The intermediate filament proteins, desmin and vimentin, are specific components of the cytoskeleton of striated muscle fibers and of mononuclear cells of mesenchymal origin including myoblasts, respectively. Desmin has also been found in presumptive myoblasts of mammals. The aim of this experiment was attempted to observe the phenotypic changes of intermediate filaments in skeletal muscle fibers during early stages of sciatic nerve crushing injury. MATERIALS AND METHODS: The sciatic nerves of rats were surgically crushed by hemostat and serial cryosections of soleus and extensor digitorum longus(EDL) muscles were prepared at 2, 4, 6, 8, 10, 15, 20 and 27 days after nerve injury. Serial cryosections were immunolabelled with desmin, vimentin and laminin and were histochemically reacted with NADH-TR. RESULTS: 1) Firstly, desmin positive fibers were appeared in fast-twitch type C fibers of both muscles at 6 days after nerve crushing, but were not reacted for vimentin. 2) Co-expressions of desmin and vimentin were firstly detected in fast-twitch type A fibers of EDL muscles at 8 days after nerve injury. In soleus muscles, co-expressions of desmin and vimentin were firstly seen in slow-twitch type B fibers at 10 days after nerve injury. Many atrophic fibers, that contained several central nuclei like myotubes and co-expressed desmin and vimentin, were appeared in EDL muscles at 10 days after nerve injury. Although whole regions of fibers were regenerated in EDL muscles, only peripheral regions of fibers were regenerated in soleus muscles at 15 days after nerve injury. Many atrophic fibers, co-expressed of desmin and vimentin, were appeared in EDL muscles at 20 days after nerve injury. These whole fibers represented various degrees of regenerating stages. Most of mature fibers containing several central nuclei, only expressed vimentin slightly, were seen in soleus muscles at 20 days after nerve injury. Most fibers of both muscles were matured at 27 days after nerve injury, but some fibers in EDL muscles were still in processing of degeneration and regeneration. No expressions of desmin and vimentin indicated that muscle fibers were almostly matured in soleus muscles at 27 days after nerve injury. 3) Targetoid or target fibers which informed reinnervation, were appeared firstly in soleus muscles at 20 days and were seen in both muscles at 27 days after nerve injury. All targetoid and target fibers were type B fibers. CONCLUSION: Desmin was revealed in processes of degeneration and regeneration and vimentin was appealed in regeneration process. At the same time, positive immunoreactivity of desmin and vimentin showed specific differences in degree of degeneration and regeneration according to different muscles and muscle fibers.

The Experimental Study on the Usability of Gore-Tex(R) as an Extraocular Muscle Expander

Expander procedure is a newly developed extraocular muscle weakening technique which has several advantages such as good control of resection margin, easy reoperation, rare postoperative muscular paresis. For the study of usability of Gore-Tex(R) as a muscle expander, fifteen rabbits received expander procedure with Gore-Tex(R) in right eye and silicone retinal band in left eye. At postoperative 1, 3, 5, 7, 12 weeks, histopathologic examination was performed. There was no significant difference in inflammatory reaction in both groups. Inflammatory reaction decreased with time in both groups. In Gore-Tex(R) expander group, muscle regeneration from cut end was observed at the 3rd postoperative week and fibroblast ingrowth into the expander was observed at the 5th postoperative week. These findings were more prominent with time. Adhesion of expander to underlying sclera was not observed in both groups. It is concluded that expander procedure using Gore-Tex(R) will be a new and useful surgical method for the extraocular muscle weakening procedure.