Fasting Induces a Highly Resilient Deep Quiescent State in Muscle Stem Cells via Ketone Body Signaling

Short-term fasting is beneficial for the regeneration of multiple tissue types. However, the effects of fasting on muscle regeneration are largely unknown. Here we report that fasting slows muscle repair both immediately after the conclusion of fasting as well as after multiple days of refeeding. We show that ketosis, either endogenously produced during fasting or a ketogenic diet, or exogenously administered, promotes a deep quiescent state in muscle stem cells(MuSCs). Although deep quiescent MuSCs are less poised to activate, slowing muscle regeneration, they have markedly improved survival when facing sources of cellular stress. Further, we show that ketone bodies, specifically b hydroxybutyrate, directly promote MuSC deep quiescence via a non-metabolic mechanism. We show that b-hydroxybutyrate functions as an HDAC inhibitor within MuSCs leading to acetylation and activation of an HDAC1 target protein p53. Finally, we demonstrate that p53 activation contributes to the deep quiescence and enhanced resilience observed during fasting.

Protein Expression in the Gastrocnemius Muscle of a Rodent Shrapnel-Injury Model

With shrapnel injuries, the metal fragment is usually left in place to reduce the risk of morbidity extensive surgery might bring. This means the individual may retain those metals for the remainder of their life. Often the long-term health effects of the embedded metal are not known, especially with respect to protein damage and perturbations of muscle repair pathways. In this study, using homogenates of rat gastrocnemius muscle implanted with pellets of military-relevant metals, we investigated expression of iNOS and eNOS, enzymes involved in nitric oxide production, as well as MMP-2 and MMP-9, matrix metalloproteinases associated with muscle repair. In addition, hydroxynonenal-modified proteins were investigated to assess metal-induced oxidative damage and metal levels in the gastrocnemius determined. Metals were implanted for up to 12 months in order to determine the long-term effects on the expression of muscle-associated proteins. With the exception of iron and cobalt at 1-month post-implantation, there were no significant differences in metal levels in the gastrocnemius in any of the cohorts. Protein expression analysis showed significant decreases in iNOS and eNOS in the 6-month and 12-month lead and depleted uranium groups. Hydroxynonenal-modified proteins were also significantly increased in the iron, copper, lead, and depleted uranium groups. These results suggest that some embedded metals can induce long-term oxidative damage, as well as affect enzyme systems involved in signal transduction.

Loss of Nup210 results in muscle repair delays and age-associated alterations in muscle integrity

Nuclear pore complexes, the channels connecting the nucleus with the cytoplasm, are built by multiple copies of ∼30 proteins called nucleoporins. Recent evidence has exposed that nucleoporins can play cell type-specific functions. Despite novel discoveries into the cellular functions of nucleoporins, their role in the regulation of mammalian tissue physiology remains mostly unexplored because of a limited number of nucleoporin mouse models. Here we show that ablation of Nup210/Gp210, a nucleoporin previously identified to play a role in myoblast differentiation and Zebrafish muscle maturation, is dispensable for skeletal muscle formation and growth in mice. We found that although primary satellite cells from Nup210 knockout mice can differentiate, these animals show delayed muscle repair after injury. Moreover, Nup210 knockout mice display an increased percentage of centrally nucleated fibers and abnormal fiber type distribution as they age. Muscle function experiments also exposed that Nup210 is required for muscle endurance during voluntary running. Our findings indicate that in mammals, Nup210 is important for the maintenance of skeletal muscle integrity and for proper muscle function providing novel insights into the in vivo roles of nuclear pore complex components.

Effect of Photo Biomodulation on Muscle Repair: a Literature Review

Muscle injuries are frequent, both in the practice of exercises and in the work environment, and after the injury, healing begins. The inflammatory phase of muscle healing is accompanied by an increase in the production of reactive oxygen species (ROS), and a reduction in the antioxidant activity of defense enzymes. This imbalance between both can generate oxidative stress, which can cause oxidative damage by directly affecting vital cellular constituents, such as lipids, proteins and DNA, in addition to interfering negatively in the muscle cells differentiation . Therefore, substances or therapies that stimulate antioxidant repair and defense are crucial to keep the levels of free radical production low, and to minimize factors that delay or prevent tissue recovery, among these therapies photo biomodulation has stood out. The objective of this literature review is to clarify the FBM effect on oxidative stress and muscle repair. Therefore, a search was carried out in the databases of Pubmed, Scielo, Lilacs and PEDro, using the keywords “Photo biomodulation”, “low power laser”, “muscle repair”, “oxidative stress”, and in English were ”Photo biomodulation”, “low level laser therapy”, “muscle repair” and “oxidative stress”. The texts that addressed the research topic, published between 2000 and 2020, were chosen. After analyzing the articles, it was possible to observe that photo biomodulation, despite presenting a great variety of parameters, moment of application and irradiation protocol found in the literature, shows beneficial results in the repair muscle and in the reduction of oxidative stress and fatigue markers. Keywords: Low-Level Light Therapy. Oxidative Stress. Edema. ResumoLesões musculares são frequentes, tanto na prática de exercícios como no ambiente de trabalho, sendo que após a lesão, inicia a cicatrização. A fase inflamatória da cicatrização muscular é acompanhada do aumento da produção de espécies reativas de oxigênio (ERO) e uma redução da atividade antioxidante das enzimas de defesa. Este desequilíbrio entre ambos pode gerar o estresse oxidativo, que leva a danos e atingi diretamente constituintes celulares vitais, como lipídios, proteínas e DNA, além de interferir negativamente na diferenciação das células musculares. Portanto, substâncias ou terapias que estimulem a reparação e a defesa antioxidante são cruciais para manter os níveis de produção de radicais livres baixos, e minimizar os fatores que atrasam ou impedem a recuperação do tecido, dentre estas terapias a fotobiomodulação tem se destacado. O objetivo da presente revisão de literatura é esclarecer o efeito da FBM sobre o estresse oxidativo e o reparo muscular. Sendo assim, realizou-se uma pesquisa nas bases de dados da Pubmed, Scielo, Lilacs e PEDro, utilizando as palavras-chave “Fotobiomodulação”, “laser de baixa potência”, “reparo muscular”, “estresse oxidativo”, e em inglês foram “photobiomodulation”, “low level laser therapy”, “muscle repair” e “oxidative stress”. Foram escolhidos os textos que abordavam o tema da pesquisa, publicados entre 2000 e 2020. Analisando os artigos foi possível observar que a fotobiomodulação apesar de apresentar grande variedade de parâmetros, momento de aplicação e protocolo de irradiação encontrados na literatura, mostra resultados benéficos no reparo muscular e na diminuição de marcadores do estresse oxidativo e fadiga. Palavras-chave: Terapia com Luz de Baixa Intensidade. Estresse Oxidativo. Edema.

Correction of whistle deformity secondary to cleft lip repair by V-Y plasty: a simple and effective technique

Several techniques are available for the surgical repair of the cleft lip, however, avoiding secondary deformities and achieving consistent results remains a challenge. The whistle deformity is a secondary lip deformity characterised by inadequate fullness of the central upper lip with abnormal exposure of the central incisors when the lips are at rest, giving a whistling appearance. The causes include scarring of the vermilion and failure to restore the mucosal or muscular continuity. Various surgical options are available ranging from simple procedures like V-Y plasty and Z-plasty to complex procedures like complete lip redo, locoregional flaps, fillers and grafts. V-Y plasty is a simple, effective procedure for lip lengthening that can be performed under local anaesthesia as an outpatient procedure. It is less technique sensitive and also allows for some degree of muscle repair. We present a case of whistle deformity satisfactorily corrected with V-Y plasty.

Current Thoughts of Notch’s Role in Myoblast Regulation and Muscle-Associated Disease

The evolutionarily conserved signaling pathway Notch is unequivocally essential for embryogenesis. Notch’s contribution to the muscle repair process in adult tissue is complex and obscure but necessary. Notch integrates with other signals in a functional antagonist manner to direct myoblast activity and ultimately complete muscle repair. There is profound recent evidence describing plausible mechanisms of Notch in muscle repair. However, the story is not definitive as evidence is slowly emerging that negates Notch’s importance in myoblast proliferation. The purpose of this review article is to examine the prominent evidence and associated mechanisms of Notch’s contribution to the myogenic repair phases. In addition, we discuss the emerging roles of Notch in diseases associated with muscle atrophy. Understanding the mechanisms of Notch’s orchestration is useful for developing therapeutic targets for disease.

Proliferin-1 Ameliorates Cardiotoxin-Related Skeletal Muscle Repair in Mice

Background. We recently demonstrated that proliferin-1 (PLF-1) functions as an apoptotic cell-derived growth factor and plays an important role in vascular pathobiology. We therefore investigated its role in muscle regeneration in response to cardiotoxin injury. Methods and Results. To determine the effects of PLF-1 on muscle regeneration, we used a CTX-induced skeletal muscle injury model in 9-week-old male mice that were administered with the recombinant PLF-1 (rPLF-1) or neutralizing PLF-1 antibody. The injured muscles exhibited increased levels of PLF-1 gene expression in a time-dependent manner. On day 14 after injury, rPLF-1 supplementation ameliorated CTX-induced alterations in muscle fiber size, interstitial fibrosis, muscle regeneration capacity, and muscle performance. On day 3 postinjury, rPLF-1 increased the levels of proteins or genes for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, p-p38MAPK, interleukin-10, Pax7, MyoD, and Cyclin B1, and it increased the numbers of CD34+/integrin-α7+ muscle stem cells and proliferating cells in the muscles and/or bone marrow of CTX mice. An enzyme-linked immunosorbent assay revealed that rPLF-1 suppressed the levels of plasma tumor necrosis factor-α and interleukin-1β in CTX mice. PLF-1 blocking accelerated CTX-related muscle damage and dysfunction. In C2C12 myoblasts, rPLF-1 increased the levels of proteins for p-Akt, p-mTOR, p-GSK3α/β, p-Erk1/2, and p-p38MAPK as well as cellular functions; and these effects were diminished by the depletion of PLF-1 or silencing of its mannose-6-phosphate receptor. Conclusions. These findings demonstrated that PLF-1 can improve skeletal muscle repair in response to injury, possibly via the modulation of inflammation and proliferation and regeneration, suggesting a novel therapeutic strategy for the management of skeletal muscle diseases.

Large-scale integration of single-cell transcriptomic data captures transitional progenitor states in mouse skeletal muscle regeneration

Skeletal muscle repair is driven by the coordinated self-renewal and fusion of myogenic stem and progenitor cells. Single-cell gene expression analyses of myogenesis have been hampered by the poor sampling of rare and transient cell states that are critical for muscle repair, and do not inform the spatial context that is important for myogenic differentiation. Here, we demonstrate how large-scale integration of single-cell and spatial transcriptomic data can overcome these limitations. We created a single-cell transcriptomic dataset of mouse skeletal muscle by integration, consensus annotation, and analysis of 23 newly collected scRNAseq datasets and 88 publicly available single-cell (scRNAseq) and single-nucleus (snRNAseq) RNA-sequencing datasets. The resulting dataset includes more than 365,000 cells and spans a wide range of ages, injury, and repair conditions. Together, these data enabled identification of the predominant cell types in skeletal muscle, and resolved cell subtypes, including endothelial subtypes distinguished by vessel-type of origin, fibro-adipogenic progenitors defined by functional roles, and many distinct immune populations. The representation of different experimental conditions and the depth of transcriptome coverage enabled robust profiling of sparsely expressed genes. We built a densely sampled transcriptomic model of myogenesis, from stem cell quiescence to myofiber maturation, and identified rare, transitional states of progenitor commitment and fusion that are poorly represented in individual datasets. We performed spatial RNA sequencing of mouse muscle at three time points after injury and used the integrated dataset as a reference to achieve a high-resolution, local deconvolution of cell subtypes. We also used the integrated dataset to explore ligand-receptor co-expression patterns and identify dynamic cell-cell interactions in muscle injury response. We provide a public web tool to enable interactive exploration and visualization of the data. Our work supports the utility of large-scale integration of single-cell transcriptomic data as a tool for biological discovery.

Modeling the ACVR1R206H mutation in human skeletal muscle stem cells

Abnormalities in skeletal muscle repair can lead to poor function and complications such as scarring or heterotopic ossification (HO). Here, we use fibrodysplasia ossificans progressiva (FOP), a disease of progressive HO caused by ACVR1R206H (Activin receptor type-1 receptor) mutation, to elucidate how ACVR1 affects skeletal muscle repair. Rare and unique primary FOP human muscle stem cells (Hu-MuSCs) isolated from cadaveric skeletal muscle demonstrated increased ECM marker expression, showed skeletal muscle-specific impaired engraftment and regeneration ability. Human induced pluripotent stem cell (iPSC)-derived muscle stem/progenitor cells (iMPCs) single cell transcriptome analyses from FOP also revealed unusually increased ECM and osteogenic marker expression compared to control iMPCs. These results show that iMPCs can recapitulate many aspects of Hu-MuSCs for detailed in vitro study, that ACVR1 is a key regulator of Hu-MuSC function and skeletal muscle repair; and that ACVR1 activation in iMPCs or Hu-MuSCs may contribute to HO by changing the local tissue environment.