Skeletal muscle regeneration is hindered in severe injuries and degenerative diseases, including volumetric muscle loss (VML), due to the failure of current treatments to induce functional tissue growth. Various biological functions in skeletal muscle are supported by the extracellular matrix (ECM), a collection of proteins and glycosaminoglycans. <i>In vivo</i> studies on murine plantaris muscle hypertrophy indicate that ECM remodeling facilitates muscle growth, but a global analysis of ECM protein dynamics during skeletal muscle hypertrophy and repair are unknown. Understanding this influence of the ECM can establish instructive cues for regenerative therapies. Here, we define global proteomic changes throughout stages of plantaris muscle hypertrophy, with an emphasis on characterizing ECM proteins. Synergistic ablation of the gastrocnemius and soleus muscles induced a compensatory hypertrophic effect causing a 40% mass increase in the plantaris muscle 28 days post injury. Liquid chromatography-tandem mass spectrometry revealed the differential abundance of 1233 proteins, including 99 ECM proteins, across five time points. After two days of injury, a significant increase of ECM glycoproteins was observed although the overall collagen abundance decreased. Throughout the duration of injury, the relative abundance of type I collagen decreased while there was an increase of proteins associated with type I collagen fibrillogenesis (types III and V) and basement membrane (types IV and VI). Collectively, these results provide a better understanding of ECM dynamics throughout skeletal muscle hypertrophy. Future studies will evaluate protein synthesis by using non-canonical amino acids to identify newly synthesized proteins. Temporal analysis of protein dynamics symbolic to injury and tissue growth will provide tissue engineers with precise information to develop successful regenerative therapies to restore functional muscle in VML.

Orientador: Hirasilva Borba / Resumo: O objetivo deste estudo foi avaliar a qualidade física, química da carne e a histomorfometria das fibras musculares de peito amadeirado (PM), e submeter estas ao processo de maturação e produção de hambúrgures e linguiça frescal, com o intuito de obter uma aplicação industrial desta carne. O capítulo 1 aborda considerações gerais e revisão de literatura sobre o tema proposto. No capítulo 2 foram avaliadas as caracteristícas físicas, químicas e histológicas da carne de peito de frangos de corte acometidos pela miopatia PM. No capítulo 3 foram avaliados os possíveis efeitos da maturação por até sete dias sobre a qualidade da carne de peito de frangos de corte acometidos pelos diferentes graus de severidade da miopatia PM. No capítulo 4 foram avaliados a qualidade de linguiças tipo frescal fabricadas com carne de peito de frangos acometidos pelos diferentes graus de severidade da miopatia PM armazenadas por 28 dias. E no capítulo 5 foram avaliados a qualidade de hambúrgueres de frangos acometidos pelos diferentes graus de severidade da miopatia PM armazenados por 120 dias. As amostras cruas de frangos acometidos pelo grau severo da miopatia PM possuem qualidade física inferior comparada com a carne de frango normal, o que pode ser prejudicial ao processamento da carne. As carnes de grau severo da miopatia PM possui níveis superiores de docosa-hexaenoico e ácido araquidônico, além de menor teor de gordura que peitos normais. As análises histomorfométricas mostram que a miodegener... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to evaluate the physical, chemical and meat quality and histomorphometry of the woody breast muscle fibers, and to submit them to the process of maturing and production of hamburgers and fresh sausages, in order to obtain an industrial application of this meat. Chapter 1 discusses general considerations and literature review on the proposed theme. In chapter 2 the physical, chemical and histological characteristics of the breast meat of broilers affected by PM myopathy were evaluated. In Chapter 3, the possible effects of maturation for up to seven days on the quality of breast meat of broilers affected by the different degrees of severity of PM myopathy were evaluated. Chapter 4 evaluated the quality of fresh sausages made with chicken breast meat affected by the different degrees of severity of PM myopathy stored for 28 days. And in Chapter 5, the quality of chicken burgers affected by different degrees of severity of PM myopathy stored for 120 days was evaluated. Raw chicken samples affected by the severe degree of PM myopathy have lower physical quality compared to normal chicken meat, which can be detrimental to meat processing. The severe meats of PM myopathy have higher levels of docosahexaenoic and arachidonic acid, and lower fat content than normal breasts. The histomorphometric analyzes show that the myocardial disease caused by PM myopathy presents muscle fiber hypertrophy as compensatory mechanism in the moderate and severe degrees ... (Complete abstract click electronic access below) / Doutor

Die weltweite Zunahme der Prävalenz von Übergewicht und Adipositas und den damit verbundenen medizinischen und sozioökonomischen Herausforderungen stellt eine der wesentlichen Herausforderungen der modernen medizinischen Versorgung dar. Im Mittelpunkt stehen dabei insbesondere die Auswirkungen von Übergewicht und Adipositas auf das kardiovaskuläre System und den damit verbundenen funktionellen und strukturellen Veränderungen der kardiovaskulären Funktion.Als Mediatoren dieser funktionellen und strukturellen Veränderungen stehen dabei zunehmend Adipozytokine im Interesse wissenschaftlicher Arbeiten. Unter Adipozytokinen versteht man in diesem Zusammenhang einen Sammelbegriff für von Adipozyten und anderen Fettgewebszellen sezernierten autokrin-, endokrin- und parakrin wirkenden bioaktiven Molekülen. Insbesondere bei Übergewicht und Adipositas kommt es zu einer charakteristischen Veränderung im Sekretionsmuster dieser Adipozytokine. Die Wirkung einzelner Adipozytokine auf die kardiovaskuläre Funktion wurde in den letzten Jahren intensiv untersucht, über die Wirkung ganzer Adipozytokinprofile ist bisher jedoch nur wenig bekannt.Ziel der vorliegenden Arbeit war es zu klären, welchen Einfluss eine 24-stündige Behandlung von neonatalen ventrikulären Kardiomyozyten mit einem physiologischen Adipozytokin-Profil auf Hypertrophie-assoziierte Signalwege und Zellproteine hat.

Die weltweite Zunahme der Prävalenz von Übergewicht und Adipositas und den damit verbundenen medizinischen und sozioökonomischen Herausforderungen stellt eine der wesentlichen Herausforderungen der modernen medizinischen Versorgung dar. Im Mittelpunkt stehen dabei insbesondere die Auswirkungen von Übergewicht und Adipositas auf das kardiovaskuläre System und den damit verbundenen funktionellen und strukturellen Veränderungen der kardiovaskulären Funktion. Als Mediatoren dieser funktionellen und strukturellen Veränderungen stehen dabei zunehmend Adipozytokine im Interesse wissenschaftlicher Arbeiten. Unter Adipozytokinen versteht man in diesem Zusammenhang einen Sammelbegriff für von Adipozyten und anderen Fettgewebszellen sezernierten autokrin-, endokrin- und parakrin wirkenden bioaktiven Molekülen. Insbesondere bei Übergewicht und Adipositas kommt es zu einer charakteristischen Veränderung im Sekretionsmuster dieser Adipozytokine. Die Wirkung einzelner Adipozytokine auf die kardiovaskuläre Funktion wurde in den letzten Jahren intensiv untersucht, über die Wirkung ganzer Adipozytokinprofile ist bisher jedoch nur wenig bekannt. Ziel der vorliegenden Arbeit war es zu klären, welchen Einfluss eine 24-stündige Behandlung von neonatalen ventrikulären Kardiomyozyten mit einem physiologischen Adipozytokin-Profil auf Hypertrophie-assoziierte Signalwege und Zellproteine hat.

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The extracellular matrix (ECM) of the skeletal muscle provides the framework for the muscle structure and plays a key role in the repair and maintenance of myofibers through the resident fibroblasts and muscle satellite cells. However, excessive production of ECM components, notably collagen, leads to fibrosis which impedes muscle function, impairs the natural repair process, and leads to muscle weakness. Fibrosis is a hallmark of muscular dystrophies, including Duchenne muscular dystrophy (DMD). Duchenne muscular dystrophy is a terminal, x-linked disorder characterized by progressive muscle wasting as muscle fibers are replaced by fibrosis and fat. There are approximately 300,000 DMD patients worldwide, and the few disease modifying treatments are genotype specific, only helping a small percentage of the patient population. Myostatin is a member of the transforming growth factor beta (TGF-β) family of ligands, is a negative regulator of muscle mass, and may also contribute to the fibrotic environment in dystrophic muscle through myofibroblast proliferation and survival. Therefore, myostatin blockade could potentially ameliorate muscle weakness in DMD patients by increasing skeletal mass and function while also reducing the accumulation of fibrosis. A murine anti-myostatin antibody, mRK35, and its humanized analogue, domagrozumab, are specific and potent inhibitors of myostatin. mRK35 was tested in multiple mouse models, from healthy C57Bl/6 and C57Bl/10, mildly dystrophic C57Bl/10.mdx, and severely dystrophic D2.mdx mice, for changes in muscle mass, muscle function, and fibrotic content. Additionally, inflammatory, fibrotic, and myogenic gene expression changes were analyzed in the severely dystrophic animals treated with mRK35. Domagrozumab was tested in non-human primates (NHPs) for changes in skeletal muscle mass. Myostatin blockade with mRK35 resulted in muscle anabolic and functional improvements in healthy murine models and NHPs treated with domagrozumab demonstrated a dose-dependent increase in lean mass and muscle volume. However, as mice age or as the dystrophic severity of the model increases, the anabolic effect of myostatin inhibition is diminished. The extensor digitorum longus (EDL) muscle escapes this trend and is the most responsive to myostatin inhibition across all mouse strains and disease severities. However, analysis of the fibrotic content in the triceps and diaphragms of D2.mdx mice treated with mRK35 for 8 weeks does not reveal any change in fibrotic content. Gene expression changes in the muscles within these mice appear to be tightly tied to their healthy or dystrophic state and myostatin inhibition has minimal effect. In sum, while specific myostatin inhibition with mRK35 increases muscle weight and function in mice, there is no conclusive evidence of reduced muscle fibrosis. / 2023-06-22T00:00:00Z

The purpose of the study was to compare the physiological responses of skeletal muscle to a resistance training (RT) program using repetition maximum (RM) or relative intensity (RISR). Fifteen well-trained males underwent RT 3 d·wk−1 for 10 weeks in either an RM group (n = 8) or RISR group (n = 7). The RM group achieved a relative maximum each day, while the RISR group trained based on percentages. The RM group exercised until muscular failure on each exercise, while the RISR group did not reach muscular failure throughout the intervention. Percutaneous needle biopsies of the vastus lateralis were obtained pre-post the training intervention, along with ultrasonography measures. Dependent variables were: Fiber type-specific cross-sectional area (CSA); anatomical CSA (ACSA); muscle thickness (MT); mammalian target of rapamycin (mTOR); adenosine monophosphate protein kinase (AMPK); and myosin heavy chains (MHC) specific for type I (MHC1), type IIA (MHC2A), and type IIX (MHC2X). Mixed-design analysis of variance and effect size using Hedge’s g were used to assess within- and between-group alterations. RISR statistically increased type I CSA (p = 0.018, g = 0.56), type II CSA (p = 0.012, g = 0.81), ACSA (p = 0.002, g = 0.53), and MT (p < 0.001, g = 1.47). RISR also yielded a significant mTOR reduction (p = 0.031, g = −1.40). Conversely, RM statistically increased only MT (p = 0.003, g = 0.80). Between-group effect sizes supported RISR for type I CSA (g = 0.48), type II CSA (g = 0.50), ACSA (g = 1.03), MT (g = 0.72), MHC2X (g = 0.31), MHC2A (g = 0.87), and MHC1 (g = 0.59); with all other effects being of trivial magnitude (g < 0.20). Our results demonstrated greater adaptations in fiber size, whole-muscle size, and several key contractile proteins when using RISR compared to RM loading paradigms.

Pathological cardiac hypertrophy often leads to heart failure. Activation of autophagy has been shown in pathological hypertrophic hearts. Autophagy is regulated positively by Class III phosphoinositide 3-kinase (PI3K). However, it is unknown whether Class III PI3K plays a role in the transition of cardiac hypertrophy to heart failure. To address this question, we employed a previously established cardiac hypertrophy model in heat shock protein 27 transgenic mice which shares common features with several types of human cardiomyopathy. Age-matched wild-type mice served as control. Firstly, a prolonged activation of autophagy, as reflected by autophagosome accumulation, increased LC3 conversion and decreased p62 protein levels, was detected in hypertrophic hearts from adaptive stage to maladaptive stage. Moreover, morphological abnormalities in myofilaments and mitochondria were presented in the areas accumulated with autophagosomes. Secondly, activation of Class III PI3K Vacuolar protein sorting 34 (Vps34), as demonstrated by upregulation of Vps34 expression, increased interaction of Vps34 with Beclin-1, and deceased Bcl-2 expression, was demonstrated in hypertrophic hearts from adaptive stage to maladaptive stage. Finally, administration with Wortmaninn, a widely used autophagy inhibitor by suppressing Class III PI3K activity, significantly decreased autophagy activity, improved morphologies of intracellular apartments, and most importantly, prevented progressive cardiac dysfunction in hypertrophic hearts. Collectively, we demonstrated that Class III PI3K plays a central role in the transition of cardiac hypertrophy to heart failure via a prolonged activation of autophagy in current study. Class III PI3K may serve as a potential target for the treatment and management of maladaptive cardiac hypertrophy.

Activation of NF-κB contributes to cardiac hypertrophy and the interleukin-1 receptor (IL-1R)-mediated MyD88-dependent signaling pathway predominately activates NF-κB. Recent studies have shown that the TIR/ BB-Loop mimetic (AS-1) disrupted the interaction of MyD88 with the IL-1R, resulting in blunting of NF-κB activation. We have examined the effects of AS-1 on the IL-1b-induced hypertrophic response using cultured neonatal cardiac myocytes in vitro and transverse aortic constriction (TAC) pressure overload-induced cardiac hypertrophy in vivo. Neonatal cardiac myocytes were treated with AS-1 15 min prior to IL-1β stimulation for 24 h. AS-1 treatment significantly attenuated IL-1β-induced hypertrophic responses of cardiac myocytes. In vivo experiments showed that AS-1 administration prevented cardiac hypertrophy and dysfunction induced by pressure overload. AS-1 administration disrupted the interaction of IL-1R with MyD88 in the pressure overloaded hearts and prevented activation of NF-κB. In addition, AS-1 prevented increases in activation of the MAPK pathway (p38 and p-ERK) in TAC-induced hypertrophic hearts. Our data suggest that the IL-1R-mediated MyD88-dependent signaling pathway plays a role in the development of cardiac hypertrophy and AS-1 attenuation of cardiac hypertrophy is mediated by blocking the interaction between IL-1R and MyD88, resulting in decreased NF-κB binding activity and decreased MAPK activation.

We examined the role of Tollip in the hypertrophic response of cardiomyocytes. C57BL/6 mice were subjected to transverse aortic constriction (TAC) for 2 weeks and age-matched sham surgical operated mice served as control. TAC significantly reduced the association of Tollip with IRAK-1 by 66.4 percent and increased NF-kappaB binding activity by 86.5 percent and the levels of phosphop38 by 114.6 percent in the myocardium compared with sham control, respectively. In vitro experiments showed that IL-1beta stimulation also significantly reduced the association of Tollip with IRAK-1 and increased NFkappaB binding activity in neonatal cardiomyocytes. Tollip overexpression by transfection of cardiac myocytes significantly attenuated the IL-1beta-induced hypertrophic response of cardiac myocytes as evidenced by reduced cell size (16.4 percent) and decreased ANP expression (33.3 percent). Overexpression of Tollip also reduced NFkappaB binding activity by 30.7 percent and phospho-p38 by 47.1 percent, respectively. The results suggest that Tollip could be a negative regulator during the development of cardiac hypertrophy. The negative regulation of cardiac hypertrophy by Tollip may involve downregulation of the MyD88-dependent NF-kappaB activation pathway.