Plasticidade das junções comunicantes no músculo bíceps braquial em modelo experimental de hipertrofia muscular: análises morfológicas, moleculares e funcionais
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Data
2021-05-26
Autores
Pimentel Neto, Jurandyr [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A junção neuromuscular (JNM) e a junção miotendínea (JMT) compreendem um sistema de junções comunicantes que por meio de diferentes estímulos se adaptam, alteram a sua morfologia e consequentemente a estrutura muscular. Um dos principais estímulos que contribuem com tais adaptações é o exercício físico em diferentes modalidades e aplicações para cada grupamento muscular. É comprovado que o exercício físico promove benefícios ao músculo estriado esquelético e particularmente as ultraestruturas da JMT, a morfologia da JNM e consequentemente aos sarcômeros. Desta forma os diferentes protocolos de escada vertical, que representam o modelo experimental de hipertrofia muscular, podem contribuir com as adaptações nas junções comunicantes e quando associados seus efeitos podem ser potencializados. O objetivo do presente estudo consistiu em descrever as adaptações morfométricas e moleculares das junções comunicantes do músculo bíceps braquial de ratos Wistar adultos, em protocolos experimentais de escada vertical. Foram utilizados 60 ratos divididos em 4 grupos: Sedentário (S) - não participou de nenhum protocolo experimental; Escalada (E) - sem sobrecarga adicional; Escalada Sobrecarga (ES) - com sobrecarga adicional progressiva; Escalada/Escalada Sobrecarga (EES) - combinação dos protocolos em dias intercalados. Os protocolos (E, ES, EES) foram realizados em 24 sessões, 3x/semana por um período de 8 semanas. Estes grupos foram submetidos durante o período pré (T1) e pós (T2) protocolo a testes funcionais. A massa corporal foi avaliada em 3 períodos (P1, P2 e P3) e ao término dos protocolos amostras do músculo bíceps braquial foram dissecadas para as técnicas microscópicas e morfométricas. Em relação à massa corporal, os Grupos experimentais apresentaram aumento da massa, porém não significativo. Em relação à massa muscular, houve aumento em E, ES e EES. Os animais dos grupos E, ES e EES apresentaram melhor rendimento no desempenho funcional, no período pós protocolo, diante do aumento do teste de carga máxima carregada e no número de escaladas realizadas e redução do tempo das escaladas. Por meio da microscopia de luz foi possível revelar aumento da área nuclear e da dimensão fractal no Grupo E e ES e redução no Grupo EES. Em relação à área de colágeno observou-se aumento nos Grupos E, ES e EES. A análise de ATPase miofibrilar demonstrou aumento da área de secção transversa (AST) das fibras: Tipo I nos Grupo E, ES e EES; Tipo II em E e ES e redução em EES; Tipo IIx aumento nos Grupos E, ES e EES. Os comprimentos dos sarcômeros do ventre muscular revelaram aumento nos Grupos E e ES e redução em EES. Nos sarcômeros proximais aumentos no Grupo E, com redução nos Grupos ES e EES. Os sarcômeros distais apresentaram aumento nos Grupos E e EES e redução em ES. Em relação ao comprimento das invaginações sarcoplasmáticas observou-se aumento nos Grupos E, ES e EES, assim como sua interface miotendínea já em relação a espessura,observou-se aumento em E e EES com redução em ES. Nos comprimentos das evaginações sarcoplasmáticas houve aumento nos Grupos E, ES e EES e nas espessuras redução em E, ES e EES. A Lâmina Basal (LB) apresentou espessamento nos Grupos E e ES e redução no Grupo EES. A Camada de Suporte de Colágeno (CSC) e as fibras colágenas transversais apresentaram aumento principalmente nos Grupos E e EES. Na região pós-sináptica (JNM) a área corada apresentou redução nos Grupos E, ES e EES, a área total demonstrou redução em ES e aumento em E e EES. O perímetro corado, perímetro total e dispersão reduziram nos Grupos E, ES e EES, com aumento no diâmetro máximo nos Grupos E e EES e redução em ES. Na JMT foram imunomarcados os telócitos (CD34+) em todos os Grupos com sua ampla disposição em suas margens. Concluímos que os diferentes protocolos experimentais contribuíram com aumento da massa muscular e desempenho funcional, além de promoverem adaptações morfológicas nas junções comunicantes, principalmente no grupo sem sobrecarga (E) e no grupo de protocolos associados (EES). As alterações refletiram no sistema unidirecional da JNM até a JMT e em suas estruturas, além da associação com o nicho de telócitos e sua íntima relação com a JMT em todos os grupos.
The neuromuscular junction (NMJ) and the myotendinous junction (MTJ) comprise a system of communicating junctions that, through different stimuli, adapt, alter their morphology and consequently the muscle structure. One of the main stimuli that contribute to such adaptations is physical exercise in different modalities and applications for each muscle group; it is proven to bring benefits to the striated skeletal muscle, particularly the ultrastructures of MTJ, the morphology of NMJ, and consequently to sarcomeres. In this way, the different vertical ladder protocols can contribute to the adaptations in the communicating junctions, and when associated, their effects can be potentiated. The present study's objective was to describe the morphometric and molecular adaptations of the communicating biceps brachial muscle junctions of adult Wistar rats in experimental vertical ladder protocols. We used 60 rats divided into 4 groups: Sedentary (S) - did not participate in any experimental protocol; Climbing (C) - performed climbs without additional overload; Overload Climbing (OC) - performed climbs with additional progressive overload; Climbing/Overload Climbing (COC) - performed interspersed climbs with and without additional progressive overload. The protocols (C, OC, COC) were performed in 24 sessions, 3x/week, for 8 weeks. These groups were submitted during the pre (T1) and post (T2) functional testing protocols. The body mass was evaluated in 3 periods (P1, P2 and P3), and at the end of the protocols, the biceps brachii muscle samples were dissected for microscopic and morphometric techniques. In relation to the body mass, the Experimental Groups presented an increase, however not significant. About the muscular mass, there was an increase in OC and not significant in C and COC. The animals of the groups C, OC, and COC presented a better performance in the functional performance, in the period after the protocol, in front of the increase of the test of maximum loaded load and the number of climbs accomplished and the reduction of the time of the climbs. It was possible to reveal an increase in the nuclear area and fractal dimension in Group C and OC and decrease Group COC through light microscopy. In relation to the collagen area, there was an increase in Groups C, OC, and COC. The myofibrillar ATPase analysis showed an increase in the cross-sectional area (CSA) of the fibers: Type I in Group C, OC, and COC; Type II in C and OC and reduction in COC; Type IIx increase in Groups C, OC, and COC. The lengths of the belly's sarcomeres revealed an increase in Groups C and OC and a reduction in COC. The proximal sarcomeres increase in Group C, with the reduction in Groups OC and COC. The distal sarcomeres showed an increase in Groups C and OC and a decrease in COC. Regarding the length of the sarcoplasmic invaginations, there was an increase in the groups E, ES, and ES, and in the thickness, there was an increase in C and COC with a reduction in OC. In the lengths of the sarcoplasmic evaginations, there was an increase in the groups C, OC, and COC, and in the thickness, there was a reduction in C, OC, and COC. The Basal Lamina (BL) showed thickening in Groups E and ES and reduction in Group EES. The Collagen Support Layer (CSL) and transverse collagen fibers increased mainly in Groups C and EES. In the post-synaptic region (NMJ), the stained area showed a reduction in Groups C, OC, and COC, the total area showed a reduction in OC and an increase in C and COC. The stained perimeter, total perimeter, and dispersion decreased in Groups C, OC, and COC, with an increase in the maximum diameter in Groups C and COC and reduction in OC. At MTJ, telocytes (CD34 +) were immunostained in all Groups with their expansive disposition on their margins. We concluded that the different experimental protocols contributed to an increase in muscle mass and functional performance and promoted morphological adaptations in the communicating junctions, mainly in the group without overload (C) and in the group of associated protocols (COC). The changes are reflected in the unidirectional system of the NMJ to the MTJ and its structures, in addition the association with the niche of telocytes and its close relationship with the MTJ in all groups.
The neuromuscular junction (NMJ) and the myotendinous junction (MTJ) comprise a system of communicating junctions that, through different stimuli, adapt, alter their morphology and consequently the muscle structure. One of the main stimuli that contribute to such adaptations is physical exercise in different modalities and applications for each muscle group; it is proven to bring benefits to the striated skeletal muscle, particularly the ultrastructures of MTJ, the morphology of NMJ, and consequently to sarcomeres. In this way, the different vertical ladder protocols can contribute to the adaptations in the communicating junctions, and when associated, their effects can be potentiated. The present study's objective was to describe the morphometric and molecular adaptations of the communicating biceps brachial muscle junctions of adult Wistar rats in experimental vertical ladder protocols. We used 60 rats divided into 4 groups: Sedentary (S) - did not participate in any experimental protocol; Climbing (C) - performed climbs without additional overload; Overload Climbing (OC) - performed climbs with additional progressive overload; Climbing/Overload Climbing (COC) - performed interspersed climbs with and without additional progressive overload. The protocols (C, OC, COC) were performed in 24 sessions, 3x/week, for 8 weeks. These groups were submitted during the pre (T1) and post (T2) functional testing protocols. The body mass was evaluated in 3 periods (P1, P2 and P3), and at the end of the protocols, the biceps brachii muscle samples were dissected for microscopic and morphometric techniques. In relation to the body mass, the Experimental Groups presented an increase, however not significant. About the muscular mass, there was an increase in OC and not significant in C and COC. The animals of the groups C, OC, and COC presented a better performance in the functional performance, in the period after the protocol, in front of the increase of the test of maximum loaded load and the number of climbs accomplished and the reduction of the time of the climbs. It was possible to reveal an increase in the nuclear area and fractal dimension in Group C and OC and decrease Group COC through light microscopy. In relation to the collagen area, there was an increase in Groups C, OC, and COC. The myofibrillar ATPase analysis showed an increase in the cross-sectional area (CSA) of the fibers: Type I in Group C, OC, and COC; Type II in C and OC and reduction in COC; Type IIx increase in Groups C, OC, and COC. The lengths of the belly's sarcomeres revealed an increase in Groups C and OC and a reduction in COC. The proximal sarcomeres increase in Group C, with the reduction in Groups OC and COC. The distal sarcomeres showed an increase in Groups C and OC and a decrease in COC. Regarding the length of the sarcoplasmic invaginations, there was an increase in the groups E, ES, and ES, and in the thickness, there was an increase in C and COC with a reduction in OC. In the lengths of the sarcoplasmic evaginations, there was an increase in the groups C, OC, and COC, and in the thickness, there was a reduction in C, OC, and COC. The Basal Lamina (BL) showed thickening in Groups E and ES and reduction in Group EES. The Collagen Support Layer (CSL) and transverse collagen fibers increased mainly in Groups C and EES. In the post-synaptic region (NMJ), the stained area showed a reduction in Groups C, OC, and COC, the total area showed a reduction in OC and an increase in C and COC. The stained perimeter, total perimeter, and dispersion decreased in Groups C, OC, and COC, with an increase in the maximum diameter in Groups C and COC and reduction in OC. At MTJ, telocytes (CD34 +) were immunostained in all Groups with their expansive disposition on their margins. We concluded that the different experimental protocols contributed to an increase in muscle mass and functional performance and promoted morphological adaptations in the communicating junctions, mainly in the group without overload (C) and in the group of associated protocols (COC). The changes are reflected in the unidirectional system of the NMJ to the MTJ and its structures, in addition the association with the niche of telocytes and its close relationship with the MTJ in all groups.
Descrição
Palavras-chave
Junção miotendínea, Junção neuromuscular, Exercício físico, Morfometria, Telócitos, Myotendinous junction, Neuromuscular junction, Physical exercise, Morphometry, Telocytes