Inhibition of TNF-α Restores Muscle Force, Inhibits Inflammation, and Reduces Apoptosis of Traumatized Skeletal Muscles

Tian Y., Wang T., Bu H., Shao G., Zhang W., Zhang L.

As skeletal muscle is one of the largest organs in the body, its damage can directly reflect a decline in somatic function, thus, further affecting daily life and health. Inflammation is a prerequisite for the repair of injured skeletal muscles. Chronic inflammation induced by inadequate repair in skeletal muscle aggravates tissue injury. Exosomes regulate inflammatory responses to facilitate the repair of skeletal muscle injury. Moreover, exosomal miR-223 with high specificity is the most abundant miRNA in peripheral blood and regarded as biomarkers for inflammation post skeletal muscle injury, which warrants further investigation. Available studies have demonstrated that exosomal miR-223 negatively correlates with TNF-α levels in serum and regulates the canonical inflammatory NF-κB signaling pathway. miR-223 is a negative feedback regulator with great potential for adjusting inflammatory imbalance and promoting skeletal muscle repair. The research on the regulation of negative feedback factors in the inflammatory signaling pathway is essential in biology and medicine. Therefore, this review mainly elaborates the formation, heterogeneity and markers of exosomes and points out exosomal miR-223 as a beneficial role in chronic skeletal muscle inflammation and can be expected to be a potential therapeutic target for skeletal muscle damage.

Abubakar S.D., Ihim S.A., Farshchi A., Maleknia S., Abdullahi H., Sasaki T., Azizi G.

Zizzo J.

It is well known that muscles can waste away (atrophy) due to a lack of physical activity. Muscle wasting commonly presents with reduced muscle strength and an impaired ability to perform daily tasks. Several studies have attempted to categorize muscle atrophy into three main subgroups: physiologic, pathologic, and neurogenic atrophy. Physiologic atrophy is caused by the general underuse of skeletal muscle (e.g., bedridden). Pathologic atrophy is characterized as the loss of stimulus to a specific region (e.g., aging). Neurogenic atrophy results from damage to the nerve innervating a muscle (e.g., SMA, GBS). Mechanisms have been elucidated for many of these pathways (e.g., ubiquitin-proteasome system, NF-κB, etc.). However, many causes of muscle atrophy (e.g., burns, arthritis, etc.) operate through unelucidated signaling cascades. Therefore, this review highlights the underlying mechanisms of each subtype of muscle atrophy while emphasizing the need for additional research in properly classifying and identifying muscle atrophy.

Sciorati C., Gamberale R., Monno A., Citterio L., Lanzani C., De Lorenzo R., Ramirez G.A., Esposito A., Manunta P., Manfredi A.A., Rovere-Querini P.

Sarcopenia is a hallmark of aging. Inflammation due to increased generation of cytokines such as TNFα, IL-1β and IL-6 has been implicated in the pathogenesis of sarcopenia. In skeletal muscle of C57BL/6 mice from 12 until 28 months of age, we observed a progressive reduction of myofiber cross sectional area, loss of type II fibers and infiltration by inflammatory cells. Muscle strength decreased in parallel. Pharmacological TNFα blockade by weekly subcutaneous injection of Etanercept from 16 to 28 months of age prevented atrophy and loss of type II fibers, with significant improvements in muscle function and mice lifespan. The effects on leukocyte recruitment were limited. These results provide a proof of principle that endogenous TNFα is sufficient to cause sarcopenia and to reduce animal survival, and open a novel perspective on novel potential pharmacological treatment strategies based on TNFα blockade to prevent the noxious events associated with aging.

Webster J.M., Kempen L.J., Hardy R.S., Langen R.C.

Cachexia is the involuntary loss of muscle and adipose tissue that strongly affects mortality and treatment efficacy in patients with cancer or chronic inflammatory disease. Currently no specific treatments or interventions are available for patients developing this disorder. Given the well-documented involvement of pro-inflammatory cytokines in muscle and fat metabolism in physiological responses and in the pathophysiology of chronic inflammatory disease and cancer, considerable interest has revolved around their role in mediating cachexia. This has been supported by association studies that report increased levels of pro-inflammatory cytokines such as TNF-α and IL-6 in some, but not all, cancers and in chronic inflammatory diseases such as COPD and rheumatoid arthritis. In addition, preclinical studies including animal disease models have provided a substantial body of evidence implicating a causal contribution of systemic inflammation to cachexia. The presence of inflammatory cytokines can affect skeletal muscle through several direct mechanisms, relying on activation of the corresponding receptor expressed by muscle, and resulting in inhibition of muscle protein synthesis, elevation of catabolic activity through the ubiquitin-proteasome system (UPS) and autophagy, and impairment of myogenesis. Additionally, systemic inflammatory mediators indirectly contribute to muscle wasting through dysregulation of tissue and organ systems, including GCs via the hypothalamus-pituitary-adrenal (HPA) axis, the digestive system leading to anorexia-cachexia, and alterations in liver and adipocyte behaviour, which subsequently impact on muscle. Finally, myokines secreted by skeletal muscle itself in response to inflammation, have been implicated as autocrine and endocrine mediators of cachexia, as well as potential modulators of this debilitating condition. Whilst inflammation has been shown to play a pivotal role in cachexia development, further understanding how these cytokines contribute to disease progression is required to reveal biomarkers or diagnostic tools to help identify at risk patients, or enable the design of targeted therapies to prevent or delay the progression of cachexia.

Chazaud B.

Inflammation is usually considered as harmful; however, it is also necessary for tissue recovery after injury. Macrophages exert immune and nonimmune functions throughout this process. During skeletal muscle regeneration, they mount an inflammatory response while exerting trophic roles on muscle and mesenchymal stem cells. Proinflammatory macrophages shift to being anti-inflammatory, triggering the resolution of inflammation. Studies have highlighted that during this shift, a crosstalk ensues, integrating cues for resolution, efferocytosis, cellular metabolism, and signaling pathways. During the restorative phase, macrophages dampen inflammation while promoting stem cell differentiation, angiogenesis, and matrix remodeling. Since blunting the inflammatory phase can be detrimental for muscle regeneration, we suggest that rather than fighting inflammation, it should be allowed to operate and resolve, thus allowing for tissue recovery.

Howard E.E., Pasiakos S.M., Blesso C.N., Fussell M.A., Rodriguez N.R.

A transient increase in local pro-inflammatory cytokine expression following skeletal muscle injury mediates the repair and regeneration of damaged myofibers through myogenesis. Regenerative capacity is diminished and muscle wasting occurs, however, when intramuscular inflammatory signaling is exceedingly high or persists chronically. An excessive and persistent inflammatory response to muscle injury may therefore impair recovery by limiting the repair of damaged tissue and triggering muscle atrophy. The concentration-dependent activation of different downstream signaling pathways by several pro-inflammatory cytokines in cell and animal models support these opposing roles of post-injury inflammation. Understanding these molecular pathways is essential in developing therapeutic strategies to attenuate excessive inflammation and accelerate functional recovery and muscle mass accretion following muscle damage. This is especially relevant given the observation that basal levels of intramuscular inflammation and the inflammatory response to muscle damage are not uniform across all populations, suggesting certain individuals may be more susceptible to an excessive inflammatory response to injury that limits recovery. This narrative review explores the opposing roles of intramuscular inflammation in muscle regeneration and muscle protein turnover. Factors contributing to an exceedingly high inflammatory response to damage and age-related impairments in regenerative capacity are also considered.

Biferali B., Proietti D., Mozzetta C., Madaro L.

Skeletal muscle is composed of a large and heterogenous assortment of cell populations that interact with each other to maintain muscle homeostasis and orchestrate regeneration. Although Satellite Cells (SCs) - which are muscle stem cells - are the protagonists of functional muscle repair following damage, several other cells such as inflammatory, vascular and mesenchymal cells coordinate muscle regeneration in a finely tuned process. Fibro-Adipogenic Progenitors (FAPs) are a muscle interstitial mesenchymal cell population, which supports SCs differentiation during tissue regeneration. During the first days following muscle injury FAPs undergo massive expansion, which is followed by their macrophage-mediated clearance and the re-establishment of their steady state pool. It is during this critical time window that FAPs, together with the other cellular components of the muscle stem cell niche, establish a dynamic network of interactions that culminate in muscle repair. A number of different molecules have been recently identified as important mediators of this cross-talk, and its alteration has been associated with different muscle pathologies. In this review, we will focus on the soluble factors that regulate FAPs activity, highlighting their roles in orchestrating the inter-cellular interactions between FAPs and the other cell populations that participate in muscle regeneration.

Marinkovic M., Fuoco C., Sacco F., Cerquone Perpetuini A., Giuliani G., Micarelli E., Pavlidou T., Petrilli L.L., Reggio A., Riccio F., Spada F., Vumbaca S., Zuccotti A., Castagnoli L., Mann M., et. al.

Fibro-adipogenic progenitors (FAPs) promote satellite cell differentiation in adult skeletal muscle regeneration. However, in pathological conditions, FAPs are responsible for fibrosis and fatty infiltrations. Here we show that the NOTCH pathway negatively modulates FAP differentiation both in vitro and in vivo. However, FAPs isolated from young dystrophin-deficient mdx mice are insensitive to this control mechanism. An unbiased mass spectrometry–based proteomic analysis of FAPs from muscles of wild-type and mdx mice suggested that the synergistic cooperation between NOTCH and inflammatory signals controls FAP differentiation. Remarkably, we demonstrated that factors released by hematopoietic cells restore the sensitivity to NOTCH adipogenic inhibition in mdx FAPs. These results offer a basis for rationalizing pathological ectopic fat infiltrations in skeletal muscle and may suggest new therapeutic strategies to mitigate the detrimental effects of fat depositions in muscles of dystrophic patients.

Jarvinen T., Jarvinen M., Kalimo H.

Thoma A., Lightfoot A.P.

Atrophy is a classical hallmark of an array of disorders that affect skeletal muscle, ranging from inherited dystrophies, acquired inflammatory myopathies, ageing (sarcopenia) and critical illness (sepsis). The loss of muscle mass and function in these instances is associated with disability, poor quality of life and in some cases mortality. The mechanisms which underpin muscle atrophy are complex; however, significant research has demonstrated an important role for inflammatory cytokines such as tumour necrosis factor-alpha (TNF-α), mediated by the generation of reactive oxygen species (ROS) in muscle wasting. Moreover, activation of the transcription factor nuclear factor kappa B (NF-κB) is a key lynchpin in the overall processes that mediate muscle atrophy. The significance of NF-κB as a key regulator of muscle atrophy has been emphasised by several in vivo studies, which have demonstrated that NF-κB-targeted therapies can abrogate muscle atrophy. In this chapter, we will summarise current knowledge on the role of cytokines (TNF-α) and NF-κB in the loss of muscle mass and function and highlight perspectives towards future research and potential therapies to combat muscle atrophy.

Straughn A.R., Hindi S.M., Xiong G., Kumar A.

Abstract Skeletal muscle regeneration in adults is attributed to the presence of satellite stem cells that proliferate, differentiate, and eventually fuse with injured myofibers. However, the signaling mechanisms that regulate satellite cell homeostasis and function remain less understood. While IKKβ-mediated canonical NF-κB signaling has been implicated in the regulation of myogenesis and skeletal muscle mass, its role in the regulation of satellite cell function during muscle regeneration has not been fully elucidated. Here, we report that canonical NF-κB signaling is induced in skeletal muscle upon injury. Satellite cell-specific inducible ablation of IKKβ attenuates skeletal muscle regeneration in adult mice. Targeted ablation of IKKβ also reduces the number of satellite cells in injured skeletal muscle of adult mice, potentially through inhibiting their proliferation and survival. We also demonstrate that the inhibition of specific components of the canonical NF-κB pathway causes precocious differentiation of cultured satellite cells both ex vivo and in vitro. Finally, our results highlight that the constitutive activation of canonical NF-κB signaling in satellite cells also attenuates skeletal muscle regeneration following injury in adult mice. Collectively, our study demonstrates that the proper regulation of canonical NF-κB signaling is important for the regeneration of adult skeletal muscle.

Beyfuss K., Hood D.A.

p53 is a tumor suppressor protein involved in regulating a wide array of signaling pathways. The role of p53 in the cell is determined by the type of imposed oxidative stress, its intensity and duration. The last decade of research has unravelled a dual nature in the function of p53 in mediating the oxidative stress burden. However, this is dependent on the specific properties of the applied stress and thus requires further analysis.A systematic review was performed following an electronic search of Pubmed, Google Scholar, and ScienceDirect databases. Articles published in the English language between January 1, 1990 and March 1, 2017 were identified and isolated based on the analysis of p53 in skeletal muscle in both animal and cell culture models.Literature was categorized according to the modality of imposed oxidative stress including exercise, diet modification, exogenous oxidizing agents, tissue manipulation, irradiation, and hypoxia. With low to moderate levels of oxidative stress, p53 is involved in activating pathways that increase time for cell repair, such as cell cycle arrest and autophagy, to enhance cell survival. However, with greater levels of stress intensity and duration, such as with irradiation, hypoxia, and oxidizing agents, the role of p53 switches to facilitate increased cellular stress levels by initiating DNA fragmentation to induce apoptosis, thereby preventing aberrant cell proliferation.Current evidence confirms that p53 acts as a threshold regulator of cellular homeostasis. Therefore, within each modality, the intensity and duration are parameters of the oxidative stressor that must be analyzed to determine the role p53 plays in regulating signaling pathways to maintain cellular health and function in skeletal muscle.Acadl: acyl-CoA dehydrogenase, long chain; Acadm: acyl-CoA dehydrogenase, C-4 to C-12 straight chain; AIF: apoptosis-inducing factor; Akt: protein kinase B (PKB); AMPK: AMP-activated protein kinase; ATF-4: activating transcription factor 4; ATM: ATM serine/threonine kinase; Bax: BCL2 associated X, apoptosis regulator; Bcl-2: B cell Leukemia/Lymphoma 2 apoptosis regulator; Bhlhe40: basic helix-loop-helix family member e40; BH3: Borane; Bim: bcl-2 interacting mediator of cell death; Bok: Bcl-2 related ovarian killer; COX-IV: cytochrome c oxidase IV; cGMP: Cyclic guanosine monophosphate; c-myc: proto-oncogene protein; Cpt1b: carnitine palmitoyltransferase 1B; Dr5: death receptor 5; eNOS: endothelial nitric oxide synthase; ERK: extracellular regulated MAP kinase; Fas: Fas Cell surface death receptor; FDXR: Ferredoxin Reductase; FOXO3a: forkhead box O3; Gadd45a: growth arrest and DNA damage-inducible 45 alpha; GLS2: glutaminase 2; GLUT 1 and 4: glucose transporter 1(endothelial) and 4 (skeletal muscle); GSH: Glutathione; Hes1: hes family bHLH transcription factor 1; Hey1: hes related family bHLH transcription factor with YRPW motif 1; HIFI-α: hypoxia-inducible factor 1, α-subunit; HK2: Hexokinase 2; HSP70: Heat Shock Protein 70; H2O2: Hydrogen Peroxide; Id2: inhibitor of DNA-binding 2; IGF-1-BP3: Insulin-like growth factor binding protein 3; IL-1β: Interleukin 1 beta; iNOS: inducible nitric oxide synthase; IRS-1: Insulin receptor substrate 1; JNK: c-Jun N-terminal kinases; LY-83583: 6-anilino-5,8-quinolinedione; inhibitor of soluble guanylate cyclase and of cGMP production; Mdm 2/ 4: Mouse double minute 2 homolog (mouse) Mdm4 (humans); mtDNA: mitochondrial DNA; MURF1: Muscle RING-finger protein-1; MyoD: Myogenic differentiation 1; MyoG: myogenin; Nanog: Nanog homeobox; NF-kB: Nuclear factor-κB; NO: nitric oxide; NoxA: phorbol-12-myristate-13-acetate-induced protein 1 (Pmaip1); NRF-1: nuclear respiratory factor 1; Nrf2: Nuclear factor erythroid 2-related factor 2; P21: Cdkn1a cyclin-dependent kinase inhibitor 1A (P21); P38 MAPK: mitogen-activated protein kinases; p53R2: p53 inducible ribonucleotide reductase gene; P66Shc: src homology 2 domain-containing transforming protein C1; PERP: p53 apoptosis effector related to PMP-22; PGC-1α: Peroxisome proliferator-activated receptor gamma coactivator 1-alpha; PGM: phosphoglucomutase; PI3K: Phosphatidylinositol-4,5-bisphosphate 3-kinase; PKCβ: protein kinase c beta; PTEN: phosphatase and tensin homolog; PTIO: 2-phenyl-4, 4, 5, 5,-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) has been used as a nitric oxide (NO) scavenger; Puma: The p53 upregulated modulator of apoptosis; PW1: paternally expressed 3 (Peg3); RNS: Reactive nitrogen species; SIRT1: sirtuin 1; SCO2: cytochrome c oxidase assembly protein; SOD2: superoxide dismutase 2; Tfam: transcription factor A mitochondrial; TIGAR: Trp53 induced glycolysis repulatory phosphatase; TNF-a: tumor necrosis factor a; TRAF2: TNF receptor associated factor 2; TRAIL: type II transmembrane protein.

Liu T., Zhang L., Joo D., Sun S.

The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory responses. NF-κB induces the expression of various pro-inflammatory genes, including those encoding cytokines and chemokines, and also participates in inflammasome regulation. In addition, NF-κB plays a critical role in regulating the survival, activation and differentiation of innate immune cells and inflammatory T cells. Consequently, deregulated NF-κB activation contributes to the pathogenic processes of various inflammatory diseases. In this review, we will discuss the activation and function of NF-κB in association with inflammatory diseases and highlight the development of therapeutic strategies based on NF-κB inhibition.

Passot C., Mulleman D., Bejan-Angoulvant T., Aubourg A., Willot S., Lecomte T., Picon L., Goupille P., Paintaud G., Ternant D.

Perrone G., Giampaoli C., Smirnoff A.L., Ochoa A., Pareja R., De Simone E.

de Souza A.L., da Silva Rosa Alves A.L., de Sousa J.C., Barbosa N.C., Rodrigues F.C., Santos S.A., de Oliveira T.S., Temerozo J.R., Bou-Habib D.C., Takiya C.M., de Azevedo Canetti C., Benjamim C.F., Coutinho-Silva R., Kurtenbach E.

Tan Y., Ye Y., Huang C., Li J., Huang L., Wei X., Liang T., Qin E., Xiong G., Bin Y.

Xiong S., Huang L., Liu H., Zhang X., Li M., Cui Y., Shao C., Hu X.

BACKGROUND Macrophages are central to the orchestration of immune responses, inflammatory processes, and the pathogenesis of diabetic complications. The dynamic polarization of macrophages into M1 and M2 phenotypes critically modulates inflammation and contributes to the progression of diabetic nephropathy. Sodium-glucose cotransporter 2 inhibitors such as dapagliflozin, which are acclaimed for their efficacy in diabetes management, may influence macrophage polarization, thereby ameliorating diabetic nephropathy. This investigation delves into these mechanistic pathways, aiming to elucidate novel therapeutic strategies for diabetes. AIM To investigate the inhibitory effect of dapagliflozin on macrophage M1 polarization and apoptosis and to explore its mechanism of action. METHODS We established a murine model of type 2 diabetes mellitus and harvested peritoneal macrophages following treatment with dapagliflozin. Concurrently, the human monocyte cell line cells were used for in vitro studies. Macrophage viability was assessed in a cell counting kit 8 assay, whereas apoptosis was evaluated by Annexin V/propidium iodide staining. Protein expression was examined through western blotting, and the expression levels of macrophage M1 surface markers, inflammatory cytokines, and apoptotic factors were quantified using flow cytometry, enzyme linked immunosorbent assay, and quantitative real-time polymerase chain reaction analyses. RESULTS Dapagliflozin attenuated M1 macrophage polarization and mitigated apoptosis in the abdominal macrophages of diabetic mice, evidenced by the downregulation of proapoptotic genes (Caspase 3 ), inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor-α, and IL-1β], and M1 surface markers (inducible nitric oxide synthase, and cluster of differentiation 86), as well as the upregulation of the antiapoptotic gene BCL2 . Moreover, dapagliflozin suppressed the expression of proteins associated with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway (PI3K, AKT, phosphorylated protein kinase B). These observations were corroborated in vitro , where we found that the modulatory effects of dapagliflozin were abrogated by 740Y-P, an activator of the PI3K/AKT signaling pathway. CONCLUSION Dapagliflozin attenuates the polarization of macrophages toward the M1 phenotype, thereby mitigating inflammation and promoting macrophage apoptosis. These effects are likely mediated through the inhibition of the PI3K/AKT signaling pathway.

Hassan N.F., Ragab D., Ibrahim S.G., Abd El-Galil M.M., Hassan Abd-El-Hamid A., Hamed D.M., Magdy William M., Salem M.A.

Although colistin has a crucial antibacterial activity in treating multidrug-resistant gram-negative bacteria strains; it exhibited renal and neuronal toxicities rendering its use a challenge. Previous studies investigated the incretin hormones either glucose-dependent insulinotropic polypeptide (GIP) or glucagonlike peptide-1 (GLP-1) for their neuroprotective and nephroprotective effectiveness. The present study focused on investigating Tirzepatide (Tirze), a dual GLP-1/GIP agonist, as an adjuvant therapy in the colistin treatment protocol for attenuating its renal and neuronal complications. Rats were divided into; The normal control group, the colistin-treated group received colistin (300,000 IU/kg/day for 7 days; i.p.). The Tirze-treated group received Tirze (1.35 mg/kg on the 1,4,7thdays; s.c.) and daily colistin. Tirze effectively enhanced histopathological alterations, renal function parameters, and locomotor activity in rats. Tirze mechanistically acted via modulating various signaling axes evolved under the insult of phosphatidylinositol 3-kinases (PI3K)/phosphorylated protein kinase-B (p-Akt)/ glycogen synthase kinase (GSK)3-β hub causing mitigation of nuclear factor (NF)-κB (NF-κB) / tumor necrosis factor-α (TNF-α), increment of nuclear factor erythroid 2-related factor 2 (Nrf2)/ glutathione (GSH), downregulation of ER stress-related biomarkers (activation transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP)), antiapoptotic effects coupling with reduction of glial fibrillary acidic protein (GFAP) immunoreactivity and enhancement of phosphorylated c-AMP response element-binding (p-CREB) / brain-derived neurotrophic factor (BDNF)/tyrosine kinase B (TrkB) neuroprotective pathway. Briefly, Tirze exerts a promising role as adjuvant therapy in the colistin treatment protocol for protection against colistin's nephro- and neurotoxicity according to its anti-inflammatory, antioxidant, and antiapoptotic impacts besides its ability to suppress ER stress-related biomarkers.

Yan Z., Xu Y., Li K., Zhang W., Liu L.

BackgroundFrailty is a complex clinical syndrome characterized by a decline in the functioning of multiple body systems and reduced adaptability to external stressors. Dietary ω-3 fatty acids are considered beneficial dietary nutrients for preventing frailty due to their anti-inflammatory and immune-regulating properties. However, previous research has yielded conflicting results, and the association between ω-6 fatty acids, the ω-6: ω-3 ratio, and frailty remains unclear. This study aims to explore the relationship between these factors using the National Health and Nutrition Examination Survey (NHANES) database.Materials and methodsSpecialized weighted complex survey design analysis software was employed to analyze data from the 2005–2014 NHANES, which included 12,315 participants. Multivariate logistic regression models and restricted cubic splines (RCS) were utilized to assess the relationship between omega intake and frailty risk in all participants. Additionally, a nomogram model for predicting frailty risk was developed based on risk factors. The reliability of the clinical model was determined by the area under the receiver operating characteristic (ROC) curve, calibration curves, and decision curve analysis (DCA).ResultsIn dietary ω-3 intake, compared to the T1 group (≤1.175 g/d), the T3 group’s intake level (>2.050 g/d) was associated with approximately 17% reduction in frailty risk in model 3, after rigorous covariate adjustments (odds ratio (OR) = 0.83, 95% confidence interval (CI): (0.70, 0.99)). In dietary ω-6 intake, the T2 group’s intake level (>11.423, ≤19.160 g/d) was associated with a 14% reduction in frailty risk compared to the T1 group (≤11.423 g/d) (OR: 0.86, 95% CI: 0.75, 1.00, p = 0.044). RCS results indicated a non-linear association between ω-3 and ω-6 intake and frailty risk. Both ROC and DCA curves demonstrated the stability of the constructed model and the effectiveness of an omega-rich diet in reducing frailty risk. However, we did not find a significant association between the ω-6: ω-3 ratio and frailty.ConclusionThis study provides support for the notion that a high intake of ω-3 and a moderate intake of ω-6 may contribute to reducing frailty risk in middle-aged and elderly individuals.

Lai Y., Ramírez-Pardo I., Isern J., An J., Perdiguero E., Serrano A.L., Li J., García-Domínguez E., Segalés J., Guo P., Lukesova V., Andrés E., Zuo J., Yuan Y., Liu C., et. al.

AbstractMuscle atrophy and functional decline (sarcopenia) are common manifestations of frailty and are critical contributors to morbidity and mortality in older people1. Deciphering the molecular mechanisms underlying sarcopenia has major implications for understanding human ageing2. Yet, progress has been slow, partly due to the difficulties of characterizing skeletal muscle niche heterogeneity (whereby myofibres are the most abundant) and obtaining well-characterized human samples3,4. Here we generate a single-cell/single-nucleus transcriptomic and chromatin accessibility map of human limb skeletal muscles encompassing over 387,000 cells/nuclei from individuals aged 15 to 99 years with distinct fitness and frailty levels. We describe how cell populations change during ageing, including the emergence of new populations in older people, and the cell-specific and multicellular network features (at the transcriptomic and epigenetic levels) associated with these changes. On the basis of cross-comparison with genetic data, we also identify key elements of chromatin architecture that mark susceptibility to sarcopenia. Our study provides a basis for identifying targets in the skeletal muscle that are amenable to medical, pharmacological and lifestyle interventions in late life.

Shimizu Y., Hamada K., Guo T., Hasegawa C., Kuga Y., Takeda K., Yagi T., Koyama H., Takagi H., Aotani D., Kataoka H., Tanaka T.

Recent studies have shown a role of inflammation in muscle atrophy and sarcopenia. However, no anti-inflammatory pharmacotherapy has been established for the treatment of sarcopenia. Here, we investigate the potential role of PPARα and its ligands on inflammatory response and PGC-1α gene expression in LPS-treated C2C12 myotubes. Knockdown of PPARα, whose expression was upregulated upon differentiation, augmented IL-6 or TNFα gene expression. Conversely, PPARα overexpression or its activation by ligands suppressed 2-h LPS-induced cytokine expression, with pemafibrate attenuating NF-κB or STAT3 phosphorylation. Of note, reduction of PGC-1α gene expression by LPS treatment for 24 hours was partially reversed by fenofibrate. Our data demonstrate a critical inhibitory role of PPARα in inflammatory response of C2C12 myotubes and suggest a future possibility of PPARα ligands as a candidate for anti-inflammatory therapy against sarcopenia.

Stratos I., Rinas I., Schröpfer K., Hink K., Herlyn P., Bäumler M., Histing T., Bruhn S., Müller-Hilke B., Menger M.D., Vollmar B., Mittlmeier T.

Testosterone deficiency in males is linked to various pathological conditions, including muscle and bone loss. This study evaluated the potential of different training modalities to counteract these losses in hypogonadal male rats. A total of 54 male Wistar rats underwent either castration (ORX, n = 18) or sham castration (n = 18), with 18 castrated rats engaging in uphill, level, or downhill interval treadmill training. Analyses were conducted at 4, 8, and 12 weeks postsurgery. Muscle force of the soleus muscle, muscle tissue samples, and bone characteristics were analyzed. No significant differences were observed in cortical bone characteristics. Castrated rats experienced decreased trabecular bone mineral density compared to sham-operated rats. However, 12 weeks of training increased trabecular bone mineral density, with no significant differences among groups. Muscle force measurements revealed decreased tetanic force in castrated rats at week 12, while uphill and downhill interval training restored force to sham group levels and led to muscle hypertrophy compared to ORX animals. Linear regression analyses showed a positive correlation between bone biomechanical characteristics and muscle force. The findings suggest that running exercise can prevent bone loss in osteoporosis, with similar bone restoration effects observed across different training modalities.

Moon S., Hong J., Go S., Kim B.

Various immune cells participate in repair and regeneration following tissue injury or damage, orchestrating tissue inflammation and regeneration processes. A deeper understanding of the immune system’s involvement in tissue repair and regeneration is critical for the development of successful reparatory and regenerative strategies. Here we review recent technologies that facilitate cell-based and biomaterial-based modulation of the immune systems for tissue repair and regeneration. First, we summarize the roles of various types of immune cells in tissue repair. Second, we review the principle, examples, and limitations of regulatory T (Treg) cell-based therapy, a representative cell-based immunotherapy. Finally, we discuss biomaterial-based immunotherapy strategies that aim to modulate immune cells using various biomaterials for tissue repair and regeneration.

Xu X., Talifu Z., Zhang C., Gao F., Ke H., Pan Y., Gong H., Du H., Yu Y., Jing Y., Du L., Li J., Yang D.

Spinal cord injury leads to loss of innervation of skeletal muscle, decreased motor function, and significantly reduced load on skeletal muscle, resulting in atrophy. Factors such as braking, hormone level fluctuation, inflammation, and oxidative stress damage accelerate skeletal muscle atrophy. The atrophy process can result in skeletal muscle cell apoptosis, protein degradation, fat deposition, and other pathophysiological changes. Skeletal muscle atrophy not only hinders the recovery of motor function but is also closely related to many systemic dysfunctions, affecting the prognosis of patients with spinal cord injury. Extensive research on the mechanism of skeletal muscle atrophy and intervention at the molecular level has shown that inflammation and oxidative stress injury are the main mechanisms of skeletal muscle atrophy after spinal cord injury and that multiple pathways are involved. These may become targets of future clinical intervention. However, most of the experimental studies are still at the basic research stage and still have some limitations in clinical application, and most of the clinical treatments are focused on rehabilitation training, so how to develop more efficient interventions in clinical treatment still needs to be further explored. Therefore, this review focuses mainly on the mechanisms of skeletal muscle atrophy after spinal cord injury and summarizes the cytokines and signaling pathways associated with skeletal muscle atrophy in recent studies, hoping to provide new therapeutic ideas for future clinical work.

Tu H., Li Y.

Responding to tissue injury, skeletal muscles undergo the tissue destruction and reconstruction accompanied with inflammation. The immune system recognizes the molecules released from or exposed on the damaged tissue. In the local minor tissue damage, tissue-resident macrophages sequester pro-inflammatory debris to prevent initiation of inflammation. In most cases of the skeletal muscle injury, however, a cascade of inflammation will be initiated through activation of local macrophages and mast cells and recruitment of immune cells from blood circulation to the injured site by recongnization of damage-associated molecular patterns (DAMPs) and activated complement system. During the inflammation, macrophages and neutrophils scavenge the tissue debris to release inflammatory cytokines and the latter stimulates myoblast fusion and vascularization to promote injured muscle repair. On the other hand, an abundance of released inflammatory cytokines and chemokines causes the profound hyper-inflammation and mobilization of immune cells to trigger a vicious cycle and lead to the cytokine storm. The cytokine storm results in the elevation of cytolytic and cytotoxic molecules and reactive oxygen species (ROS) in the damaged muscle to aggravates the tissue injury, including the healthy bystander tissue. Severe inflammation in the skeletal muscle can lead to rhabdomyolysis and cause sepsis-like systemic inflammation response syndrome (SIRS) and remote organ damage. Therefore, understanding more details on the involvement of inflammatory factors and immune cells in the skeletal muscle damage and repair can provide the new precise therapeutic strategies, including attenuation of the muscle damage and promotion of the muscle repair.

Deprez A., Orfi Z., Rieger L., Dumont N.A.

Skeletal muscle possesses a high plasticity and a remarkable regenerative capacity that relies mainly on muscle stem cells. Molecular and cellular components of the muscle stem cell niche, such as immune cells, play key roles to coordinate muscle stem cell function and to orchestrate muscle regeneration. An abnormal infiltration of immune cells and/or imbalance of pro- and anti-inflammatory cytokines could lead to muscle stem cell dysfunctions that could have long lasting effects on muscle function. Different genetic variants were shown to cause muscular dystrophies that intrinsically compromise muscle stem cell function and disturb their microenvironment leading to impaired muscle regeneration that contributes to disease progression. Alternatively, many acquired myopathies caused by comorbidities (e.g., cardiopulmonary or kidney diseases), chronic inflammation/infection, or side effects of different drugs can also perturb muscle stem cell function and their microenvironment. The goal of this review is to comprehensively summarize the current knowledge on acquired myopathies and their impact on MuSC function. We further describe potential therapeutic strategies to restore muscle stem cell regenerative capacity.

Dubuisson N., Versele R., Planchon C., Selvais C.M., Noel L., Abou-Samra M., Davis-López de Carrizosa M.A.

Duchenne muscular dystrophy (DMD) is a progressive disease caused by the loss of function of the protein dystrophin. This protein contributes to the stabilisation of striated cells during contraction, as it anchors the cytoskeleton with components of the extracellular matrix through the dystrophin-associated protein complex (DAPC). Moreover, absence of the functional protein affects the expression and function of proteins within the DAPC, leading to molecular events responsible for myofibre damage, muscle weakening, disability and, eventually, premature death. Presently, there is no cure for DMD, but different treatments help manage some of the symptoms. Advances in genetic and exon-skipping therapies are the most promising intervention, the safety and efficiency of which are tested in animal models. In addition to in vivo functional tests, ex vivo molecular evaluation aids assess to what extent the therapy has contributed to the regenerative process. In this regard, the later advances in microscopy and image acquisition systems and the current expansion of antibodies for immunohistological evaluation together with the development of different spectrum fluorescent dyes have made histology a crucial tool. Nevertheless, the complexity of the molecular events that take place in dystrophic muscles, together with the rise of a multitude of markers for each of the phases of the process, makes the histological assessment a challenging task. Therefore, here, we summarise and explain the rationale behind different histological techniques used in the literature to assess degeneration and regeneration in the field of dystrophinopathies, focusing especially on those related to DMD.

Li Z., Zhou Q., Liu X., Li Y., Fan X., Liu G.

Although there are numerous treatment strategies, including surgery and chemotherapy, the prognosis of cervical cancer remains far from satisfactory. There is an urgent need to develop more effective, more tolerable and safer therapeutics for the treatment of cervical cancer. Lycorine is a natural plantextract that has been previously found to confer anti‑tumor activities. Therefore, in the present study, the effects of lycorine and its possible mechanism of action in cervical cancer were investigated. Cell Counting Kit‑8, wound healing and Transwell assays were used to verify the proliferation and migration of HeLa cells following lycorine intervention. The results demonstrated that lycorine significantly inhibited the proliferation and migration of HeLa cells. RNA binding motif 10 (RBM10) is a protein associated with apoptosis. It has been suggested that lycorine can affect the expression of RBM10. Flow cytometry demonstrated that lycorine may inhibit the initiation and progression of cervical cancer by promoting apoptosis, which may be mediated through the upregulation of RBM10 expression and increasing TNF‑α levels. Xenograft mouse experiments indicated that when lycorine was injected through the tail vein, HeLa tumor growth was inhibited. Mechanistically, western blotting demonstrated that lycorine significantly inhibited the activation of the Akt signaling pathway and potentially reversed epithelial‑mesenchymal transition, which was also mediated by RBM10. Furthermore, following RBM10 knockdown with small interfering‑RNA, the inhibitory effects of lycorine on cervical cancer was significantly abrogated. Overall, results of the present study suggest that lycorine can upregulate the expression of RBM10 and inhibit the proliferation and migration of cervical cancer cells.