Age-related decline of interferon-gamma responses in macrophage impairs satellite cell proliferation and regeneration

Zfp697 is an RNA-binding protein that regulates skeletal muscle inflammation and remodeling

Skeletal muscle atrophy is a morbidity and mortality risk factor that happens with disuse, chronic disease, and aging. The tissue remodeling that happens during recovery from atrophy or injury involves changes in different cell types such as muscle fibers, and satellite and immune cells. Here, we show that the previously uncharacterized gene and protein Zfp697 is a damage-induced regulator of muscle remodeling. Zfp697/ZNF697 expression is transiently elevated during recovery from muscle atrophy or injury in mice and humans. Sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Notably, although Zfp697 is expressed in several cell types in skeletal muscle, myofiber-specific Zfp697 genetic ablation in mice is sufficient to hinder the inflammatory and regenerative response to muscle injury, compromising functional recovery. We show that Zfp697 is an essential mediator of the interferon gamma response in muscle cells and that it functions primarily as an RNA-interacting protein, with a very high number of miRNA targets. This work identifies Zfp697 as an integrator of cell-cell communication necessary for tissue remodeling and regeneration.

Harnessing immunomodulation to combat sarcopenia: current insights and possible approaches

Sarcopenia is a complex age-associated syndrome of progressive loss of muscle mass and strength. Although this condition is influenced by many factors, age-related changes in immune function including immune cell dynamics, and chronic inflammation contribute to its progression. The complex interplay between the immune system, gut-muscle axis, and autophagy further underscores their important roles in sarcopenia pathogenesis. Immunomodulation has emerged as a promising strategy to counteract sarcopenia. Traditional management approaches to treat sarcopenia including physical exercise and nutritional supplementation, and the emerging technologies of biophysical stimulation demonstrated the importance of immunomodulation and regulation of macrophages and T cells and reduction of chronic inflammation. Treatments to alleviate low-grade inflammation in older adults by modulating gut microbial composition and diversity further combat sarcopenia. Furthermore, some pharmacological interventions, nano-medicine, and cell therapies targeting muscle, gut microbiota, or autophagy present additional avenues for immunomodulation in sarcopenia. This narrative review explores the immunological underpinnings of sarcopenia, elucidating the relationship between the immune system and muscle during ageing. Additionally, the review discusses new areas such as the gut-muscle axis and autophagy, which bridge immune system function and muscle health. Insights into current and potential approaches for sarcopenia management through modulation of the immune system are provided, along with suggestions for future research directions and therapeutic strategies. We aim to guide further investigation into clinical immunological biomarkers and identify indicators for sarcopenia diagnosis and potential treatment targets to combat this condition. We also aim to draw attention to the importance of considering immunomodulation in the clinical management of sarcopenia.

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

Macrophages are versatile immune cells with remarkable plasticity, enabling them to adapt to diverse tissue microenvironments and perform various functions. Traditionally categorized into classically activated (M1) and alternatively activated (M2) phenotypes, recent advances have revealed a spectrum of macrophage activation states that extend beyond this dichotomy. The complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications orchestrates macrophage polarization, allowing them to respond to various stimuli dynamically. Here, we provide a comprehensive overview of the signaling cascades governing macrophage plasticity, focusing on the roles of Toll-like receptors, signal transducer and activator of transcription proteins, nuclear receptors, and microRNAs. We also discuss the emerging concepts of macrophage metabolic reprogramming and trained immunity, contributing to their functional adaptability. Macrophage plasticity plays a pivotal role in tissue repair and regeneration, with macrophages coordinating inflammation, angiogenesis, and matrix remodeling to restore tissue homeostasis. By harnessing the potential of macrophage plasticity, novel therapeutic strategies targeting macrophage polarization could be developed for various diseases, including chronic wounds, fibrotic disorders, and inflammatory conditions. Ultimately, a deeper understanding of the molecular mechanisms underpinning macrophage plasticity will pave the way for innovative regenerative medicine and tissue engineering approaches.

IL-33 Facilitates Fibro-Adipogenic Progenitors to Establish the Pro-Regenerative Niche after Muscle Injury

During the process of muscle regeneration post-injury in adults, muscle stem cells (MuSCs) function is facilitated by neighboring cells within the pro-regenerative niche. However, the precise mechanism triggering the initiation of signaling in the pro-regenerative niche remains unknown. Using single-cell RNA sequencing, 14 different muscle cells are comprehensively mapped during the initial stage following injury. Among these, macrophages and fibro-adipogenic progenitor cells (FAPs) exhibit the most pronounced intercellular communication with other cells. In the FAP subclusters, the study identifies an activated FAP phenotype that secretes chemokines, such as CXCL1, CXCL5, CCL2, and CCL7, to recruit macrophages after injury. Il1rl1, encoding the protein of the interleukin-33 (IL-33) receptor, is identified as a highly expressed signature surface marker of the FAP phenotype. Following muscle injury, autocrine IL-33, an alarmin, has been observed to activate quiescent FAPs toward this inflammatory phenotype through the IL1RL1-MAPK/NF-κB signaling pathway. Il1rl1 deficiency results in decreased chemokine expression and recruitment of macrophages, accompanied by impaired muscle regeneration. These findings elucidate a novel mechanism involving the IL-33/IL1RL1 signaling pathway in promoting the activation of FAPs and facilitating muscle regeneration, which can aid the development of therapeutic strategies for muscle-related disorders and injuries.

Characterizing the skeletal muscle immune microenvironment for sarcopenia: insights from transcriptome analysis and histological validation

Background

Sarcopenia is a condition characterized by the age-related loss of skeletal muscle mass and function. The pathogenesis of the disease is influenced by chronic low-grade inflammation. However, the specific changes in the immune landscape changes of sarcopenic muscle are not yet fully understood.

Methods

To gain insights into the immune cell composition and interactions, we combined single-nucleus RNA sequencing data, bulk RNA sequencing dataset, and comprehensive bioinformatic analyses on the skeletal muscle samples from young, aged, and sarcopenic individuals. Histological staining was then performed on skeletal muscles to validate the distribution of immune cells in clinical samples.

Results

We analyzed the transcriptomes of 101,862 single nuclei, revealing a total of 10 major cell types and 6 subclusters of immune cell types within the human skeletal muscle tissues. Notable variations were identified in the immune microenvironment between young and aged skeletal muscle. Among the immune cells from skeletal muscle microenvironment, macrophages constituted the largest fraction. A specific marker gene LYVE1 for skeletal muscle resident macrophages was further identified. Cellular subclasses included four distinct groups of resident macrophages, which play different roles in physiological or non-physiological conditions. Utilizing bulk RNA sequencing data, we observed a significant enrichment of macrophage-rich inflammation in sarcopenia.

Conclusions

Our findings demonstrate age-related changes in the composition and cross-talk of immune cells in human skeletal muscle microenvironment, which contribute to chronic inflammation in aged or sarcopenia muscle. Furthermore, macrophages emerge as a potential therapeutic target, thus advancing our understanding of the pathogenesis of sarcopenia.

Polygonatum sibiricum polysaccharide ameliorates skeletal muscle aging via mitochondria-associated membrane-mediated calcium homeostasis regulation

BACKGROUND

Sarcopenia, an age-related disease, is characterized by a gradual loss of muscle mass, strength, and function. It has been linked to abnormal organelle function in myotubes, including the mitochondria and endoplasmic reticulum (ER). Recent studies revealed that mitochondria-associated membranes (MAM), the sites connecting mitochondria and the ER, may be implicated in skeletal muscle aging. In this arena, the potential of Polygonatum sibiricum polysaccharide (PSP) emerges as a beacon of hope. PSP, with its remarkable antioxidant and anti-senescence properties, is on the cusp of a therapeutic revolution, offering a promising strategy to mitigate the impacts of sarcopenia.

PURPOSE

The objective of this research is to explore the effects of PSP on age-related muscle dysfunction and the underlying mechanisms involved both in vivo and in vitro.

METHODS

In this investigation, we used in vitro experiments using D-galactose (D-gal)-induced aging in C2C12 myotubes and in vivo experiments on aged mice. Key indices were assessed, including reactive oxygen species (ROS) levels, mitochondrial function, the expression of aging-related markers, and the key proteins of mitochondria and MAM fraction. Differentially expressed genes (DEGs) related to mitochondria and ER were identified, and bioinformatic analyses were performed to explore underlying mechanisms. Muscle mass and function were determined to evaluate the quantity and quality of skeletal muscle in vivo.

RESULTS

PSP treatment effectively mitigated oxidative stress and mitochondrial malfunction caused by D-gal in C2C12 myotubes, preserving mitochondrial fitness and reducing MAM formation. Besides, PSP attenuated D-gal-induced increases in Ca2+ concentrations intracellularly by modulating the calcium-related proteins, which were also confirmed by gene ontology (GO) analysis of DEGs. In aged mice, PSP increased muscle mass and improved grip strength, hanging time, and other parameters while reducing ROS levels and increasing antioxidant enzyme activities in skeletal muscle tissue.

CONCLUSION

PSP offers protection against age-associated muscle impairments. The proposed mechanism suggests that modulation of calcium homeostasis via regulation of the MAM results in a favorable functional outcome during skeletal muscle aging. The results of this study highlight the prospect of PSP as a curative intervention for sarcopenia and affiliated pathological conditions, warranting further investigation.

Aerobic exercise suppresses CCN2 secretion from senescent muscle stem cells and boosts muscle regeneration in aged mice

BACKGROUND

Aging negatively impacts tissue repair, particularly in skeletal muscle, where the regenerative capacity of muscle stem cells (MuSCs) diminishes with age. Although aerobic exercise is known to attenuate skeletal muscle atrophy, its specific impact on the regenerative and repair capacity of MuSCs remains unclear.

METHODS

Mice underwent moderate-intensity continuous training (MICT) from 9 months (aged + Ex-9M) or 20 months (aged + Ex-20M) to 25 months, with age-matched (aged) and adult controls. Histological examinations and MuSC transplantation assays assessed aerobic exercise effects on MuSC function and muscle regeneration. CCN2/connective tissue growth factor modulation (overexpression and knockdown) in MuSCs and AICAR supplementation effects were explored.

RESULTS

Aged mice displayed significantly reduced running duration (65.33 ± 4.32 vs. 161.9 ± 1.29 min, mean ± SD, P < 0.001) and distance (659.17 ± 103.64 vs. 3058.28 ± 46.26 m, P < 0.001) compared with adults. This reduction was accompanied by skeletal muscle weight loss and decreased myofiber cross-sectional area (CSA). However, MICT initiated at 9 or 20 months led to a marked increase in running duration (142.75 ± 3.14 and 133.86 ± 20.47 min, respectively, P < 0.001 compared with aged mice) and distance (2347.58 ± 145.11 and 2263 ± 643.87 m, respectively, P < 0.001). Additionally, MICT resulted in increased skeletal muscle weight and enhanced CSA. In a muscle injury model, aged mice exhibited fewer central nuclear fibres (CNFs; 266.35 ± 68.66/mm2), while adult, aged + Ex-9M and aged + Ex-20M groups showed significantly higher CNF counts (610.82 ± 46.76, 513.42 ± 47.19 and 548.29 ± 71.82/mm2, respectively; P < 0.001 compared with aged mice). MuSCs isolated from aged mice displayed increased CCN2 expression, which was effectively suppressed by MICT. Transplantation of MuSCs overexpressing CCN2 (Lenti-CCN2, Lenti-CON as control) into injured tibialis anterior muscle compromised regeneration capacity, resulting in significantly fewer CNFs in the Lenti-CCN2 group compared with Lenti-CON (488.07 ± 27.63 vs. 173.99 ± 14.28/mm2, P < 0.001) at 7 days post-injury (dpi). Conversely, knockdown of CCN2 (Lenti-CCN2shR, Lenti-NegsiR as control) in aged MuSCs improved regeneration capacity, significantly increasing the CNF count from 254.5 ± 26.36 to 560.39 ± 48.71/mm2. Lenti-CCN2 MuSCs also increased fibroblast proliferation and exacerbated skeletal muscle fibrosis, while knockdown of CCN2 in aged MuSCs mitigated this pattern. AICAR supplementation, mimicking exercise, replicated the beneficial effects of aerobic exercise by mitigating muscle weight decline, enhancing satellite cell activity and reducing fibrosis.

CONCLUSIONS

Aerobic exercise effectively reverses the decline in endurance capacity and mitigates muscle atrophy in aged mice. It inhibits CCN2 secretion from senescent MuSCs, thereby enhancing skeletal muscle regeneration and preventing fibrosis in aged mice. AICAR supplementation mimics the beneficial effects of aerobic exercise.

Immune checkpoint inhibitor for different age patients with NSCLC in efficacy: A systematic review and meta-analysis

OBJECTIVE

This article is a Meta-analysis aiming to systematically evaluate the difference in efficacy of immune checkpoint inhibitor in patients with non-small cell lung cancer (NSCLC) by age.

METHODS

We performed a Meta-analysis of published randomized controlled trials concerning for patients with NSCLC by age. We compared overall survival among three groups (age <65 years, age 65-75 years, age ≥75 years). Hazard ratios (HRs) and 95% confidence intervals (CIs) were collected and pooled.

RESULTS

A total of 10,291 patients from 17 RCTs were included. In the group under age 65 years, immune checkpoint inhibitor can significantly prolong the overall survival of patients with NSCLC (HR = 0.73, 95% CI: 0.66∼0.81, P < 0.00001). In the age 65-75 years group, immune checkpoint inhibitors prolonged overall survival in patients with NSCLC (HR = 0.78, 95% CI:0.71∼0.84, P < 0.00001). However, it has no significant effect on the overall survival of NSCLC patients (HR = 0.88, 95% CI:0.72∼1.08, P > 0.05) in the group older than 75 years.

CONCLUSIONS

Immune checkpoint inhibitors prolonged the overall survival of NSCLC patients in the age <65 years group and the age 65-75 years group, but in the age ≥75 years group, there was no significant effect on overall survival. This may be related to innate immune and adaptive immune dysregulation due to "immunosenescence" in older patients.

Control of muscle satellite cell function by specific exercise-induced cytokines and their applications in muscle maintenance

Exercise is recognized to play an observable role in improving human health, especially in promoting muscle hypertrophy and intervening in muscle mass loss-related diseases, including sarcopenia. Recent rapid advances have demonstrated that exercise induces the release of abundant cytokines from several tissues (e.g., liver, muscle, and adipose tissue), and multiple cytokines improve the functions or expand the numbers of adult stem cells, providing candidate cytokines for alleviating a wide range of diseases. Muscle satellite cells (SCs) are a population of muscle stem cells that are mitotically quiescent but exit from the dormancy state to become activated in response to physical stimuli, after which SCs undergo asymmetric divisions to generate new SCs (stem cell pool maintenance) and commit to later differentiation into myocytes (skeletal muscle replenishment). SCs are essential for the postnatal growth, maintenance, and regeneration of skeletal muscle. Emerging evidence reveals that exercise regulates muscle function largely via the exercise-induced cytokines that govern SC potential, but this phenomenon is complicated and confusing. This review provides a comprehensive integrative overview of the identified exercise-induced cytokines and the roles of these cytokines in SC function, providing a more complete picture regarding the mechanism of SC homeostasis and rejuvenation therapies for skeletal muscle.

Restoring Mitochondrial Function and Muscle Satellite Cell Signaling: Remedies against Age-Related Sarcopenia

Sarcopenia has a complex pathophysiology that encompasses metabolic dysregulation and muscle ultrastructural changes. Among the drivers of intracellular and ultrastructural changes of muscle fibers in sarcopenia, mitochondria and their quality control pathways play relevant roles. Mononucleated muscle stem cells/satellite cells (MSCs) have been attributed a critical role in muscle repair after an injury. The involvement of mitochondria in supporting MSC-directed muscle repair is unclear. There is evidence that a reduction in mitochondrial biogenesis blunts muscle repair, thus indicating that the delivery of functional mitochondria to injured muscles can be harnessed to limit muscle fibrosis and enhance restoration of muscle function. Injection of autologous respiration-competent mitochondria from uninjured sites to damaged tissue has been shown to reduce infarct size and enhance cell survival in preclinical models of ischemia-reperfusion. Furthermore, the incorporation of donor mitochondria into MSCs enhances lung and cardiac tissue repair. This strategy has also been tested for regeneration purposes in traumatic muscle injuries. Indeed, the systemic delivery of mitochondria promotes muscle regeneration and restores muscle mass and function while reducing fibrosis during recovery after an injury. In this review, we discuss the contribution of altered MSC function to sarcopenia and illustrate the prospect of harnessing mitochondrial delivery and restoration of MSCs as a therapeutic strategy against age-related sarcopenia.

Muscle stem cell niche dynamics during muscle homeostasis and regeneration

The process of skeletal muscle regeneration involves a coordinated interplay of specific cellular and molecular interactions within the injury site. This review provides an overview of the cellular and molecular components in regenerating skeletal muscle, focusing on how these cells or molecules in the niche regulate muscle stem cell functions. Dysfunctions of muscle stem cell-to-niche cell communications during aging and disease will also be discussed. A better understanding of how niche cells coordinate with muscle stem cells for muscle repair will greatly aid the development of therapeutic strategies for treating muscle-related disorders.

FGF10 attenuates allergic airway inflammation in asthma by inhibiting PI3K/AKT/NF-κB pathway

BACKGROUND

The effect of fibroblast growth factor 10 (Fgf10) against allergic asthma has remained unclear, despite its importance in lung development and homeostasis maintenance. The purpose of this study was to investigate the protective effect and potential mechanism of Fgf10 on asthma.

METHOD

House Dust Mite (HDM)-induced asthma mice were administered recombinant Fgf10 intranasally during activation. Flow cytometry and ELISA were performed to determine type of inflammatory cells and type 2 cytokines levels in bronchoalveolar lavage fluid (BALF). Hematoxylin and eosin (H&E) and periodic acid - Schiff (PAS) staining of lung sections were conducted to evaluate histopathological assessment. Transcriptome profiling was analyzed using RNA-seq, followed by bioinformatics and network analyses to investigate the potential mechanisms of Fgf10 in asthma. RT-qPCR was also used to search for and validate differentially expressed genes in human Peripheral Blood Mononuclear Cells (PBMCs).

RESULTS

Exogenous administration of Fgf10 alleviated HDM-induced inflammation and mucus secretion in lung tissues of mice. Fgf10 also significantly inhibited the accumulation of eosinophils and type 2 cytokines (IL-4, IL-5, and IL-13) in BALF. The PI3K/AKT/NF-κB pathway may mediate the suppressive impact of Fgf10 on the asthma inflammation. Through RNA-seq analysis, the intersection of 71 differentially expressed genes (DEGs) was found between HDM challenge and Fgf10 treatment. GO and KEGG enrichment analyses indicated a strong correlation between the DEGs and different immune response. Immune infiltration analysis predicted the differential infiltration of five types of immune cells, such as NK cells, dendritic cells, monocytes and M1 macrophages. PPI analysis determined hub genes such as Irf7, Rsad2, Isg15 and Rtp4. Interestingly, above genes were consistently altered in human PBMCs in asthmatic patients.

CONCLUSION

Asthma airway inflammation could be attenuated by Fgf10 in this study, suggesting that it could be a potential therapeutic target.

Hallmarks of ageing in human skeletal muscle and implications for understanding the pathophysiology of sarcopenia in women and men

Ageing is a complex biological process associated with increased morbidity and mortality. Nine classic, interdependent hallmarks of ageing have been proposed involving genetic and biochemical pathways that collectively influence ageing trajectories and susceptibility to pathology in humans. Ageing skeletal muscle undergoes profound morphological and physiological changes associated with loss of strength, mass, and function, a condition known as sarcopenia. The aetiology of sarcopenia is complex and whilst research in this area is growing rapidly, there is a relative paucity of human studies, particularly in older women. Here, we evaluate how the nine classic hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication contribute to skeletal muscle ageing and the pathophysiology of sarcopenia. We also highlight five novel hallmarks of particular significance to skeletal muscle ageing: inflammation, neural dysfunction, extracellular matrix dysfunction, reduced vascular perfusion, and ionic dyshomeostasis, and discuss how the classic and novel hallmarks are interconnected. Their clinical relevance and translational potential are also considered.

The multifaceted role of macrophages in homeostatic and injured skeletal muscle

Skeletal muscle is essential for body physical activity, energy metabolism, and temperature maintenance. It has excellent capabilities to maintain homeostasis and to regenerate after injury, which indispensably relies on muscle stem cells, satellite cells (MuSCs). The quiescence, activation, and differentiation of MuSCs are tightly regulated in homeostatic and regenerating muscles. Among the important regulators are intramuscular macrophages, which are functionally heterogeneous with different subtypes present in a spatiotemporal manner to regulate the balance of different MuSC statuses. During chronic injury and aging, intramuscular macrophages often undergo aberrant activation, which in turn disrupts muscle homeostasis and regenerative repair. Growing evidence suggests that the aberrant activation is mainly triggered by altered muscle microenvironment. The trained immunity that affects myeloid progenitors during hematopoiesis may also contribute. Aged immune system may contribute, in part, to the aging-related sarcopenia and compromised skeletal muscle injury repair. As macrophages are actively involved in the progression of many muscle diseases, manipulating their functional activation has become a promising therapeutic approach, which requires comprehensive knowledge of the cellular and molecular mechanisms underlying the diverse activation. To this end, we discuss here the current knowledge of multifaceted role of macrophages in skeletal muscle homeostasis, injury, and repair.

The transcriptional regulator KLF15 is necessary for myoblast differentiation and muscle regeneration by activating FKBP5

Successful muscle regeneration following injury is essential for functional homeostasis of skeletal muscles. Krüppel-like factor 15 (KLF15) is a metabolic transcriptional regulator in the muscles. However, little is known regarding its function in muscle regeneration. Here, we examined microarray datasets from the Gene Expression Omnibus database, which indicated downregulated KLF15 in muscles from patients with various muscle diseases. Additionally, we found that Klf15 knockout (Klf15KO) impaired muscle regeneration following injury in mice. Furthermore, KLF15 expression was robustly induced during myoblast differentiation. Myoblasts with KLF15 deficiency showed a marked reduction in their fusion capacity. Unbiased transcriptome analysis of muscles on day 7 postinjury revealed downregulated genes involved in cell differentiation and metabolic processes in Klf15KO muscles. The FK506-binding protein 51 (FKBP5), a positive regulator of myoblast differentiation, was ranked as one of the most strongly downregulated genes in the Klf15KO group. A mechanistic search revealed that KLF15 binds directly to the promoter region of FKBP5 and activates FKBP5 expression. Local delivery of FKBP5 rescued the impaired muscle regeneration in Klf15KO mice. Our findings reveal a positive regulatory role of KLF15 in myoblast differentiation and muscle regeneration by activating FKBP5 expression. KLF15 signaling may be a novel therapeutic target for muscle disorders associated with injuries or diseases.

Integrated bioinformatics analysis of dendritic cells hub genes reveal potential early tuberculosis diagnostic markers

BACKGROUND

Dendritic cells (DCs) are most potent antigen-processing cells and play key roles in host defense against Mycobacterium tuberculosis (MTB) infection. In this study, hub genes in DCs during MTB infection were first investigated using bioinformatics approaches and further validated in Monocyte-derived DCs.

METHODS

Microarray datasets were obtained from Gene Expression Omnibus (GEO) database. Principal component analysis (PCA) and immune infiltration analysis were performed to select suitable samples for further analysis. Differential analysis and functional enrichment analysis were conducted on DC samples, comparing live MTB-infected and non-infected (NI) groups. The CytoHubba plugin in Cytoscape was used to identify hub genes from the differentially expressed genes (DEGs). The expression of the hub genes was validated using two datasets and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in human monocyte-derived DCs. Enzyme-linked immunosorbent assay (ELISA) was used to validate interferon (IFN) secretion. Transcription factors (TFs) and microRNAs (miRNAs) that interact with the hub genes were predicted using prediction databases. The diagnostic value of the hub genes was evaluated using receiver operating characteristic (ROC) curves and area under the curve (AUC) values.

RESULTS

A total of 1835 common DEGs among three comparison groups (18 h, 48 h, 72 h after MTB infection) were identified. Six DEGs (IFIT1, IFIT2, IFIT3, ISG15, MX1, and RSAD2) were determined as hub genes. Functions enrichment analysis revealed that all hub genes all related to IFN response. RT-qPCR showed that the expression levels of six hub genes were significantly increased after DC stimulated by live MTB. According to the results of ELISA, the secretion of IFN-γ, but not IFN-α/β, was upregulated in MTB-stimulated DCs. AUC values of six hub genes ranged from 84 to 94% and AUC values of 5 joint indicators of two hub genes were higher than the two hub genes alone.

CONCLUSION

The study identified 6 hub genes associated with IFN response pathway. These genes may serve as potential diagnostic biomarkers in tuberculosis (TB). The findings provide insights into the molecular mechanisms involved in the host immune response to MTB infection and highlight the diagnostic potential of these hub genes in TB.

The time-course of cancer cachexia onset reveals biphasic transcriptional disruptions in female skeletal muscle distinct from males

BACKGROUND

Cancer-cachexia (CC) is a debilitating condition affecting up to 80% of cancer patients and contributing to 40% of cancer-related deaths. While evidence suggests biological sex differences in the development of CC, assessments of the female transcriptome in CC are lacking, and direct comparisons between sexes are scarce. This study aimed to define the time course of Lewis lung carcinoma (LLC)-induced CC in females using transcriptomics, while directly comparing biological sex differences.

RESULTS

We found the global gene expression of the gastrocnemius muscle of female mice revealed biphasic transcriptomic alterations, with one at 1 week following tumor allograft and another during the later stages of cachexia development. The early phase was associated with the upregulation of extracellular-matrix pathways, while the later phase was characterized by the downregulation of oxidative phosphorylation, electron transport chain, and TCA cycle. When DEGs were compared to a known list of mitochondrial genes (MitoCarta), ~ 47% of these genes were differently expressed in females exhibiting global cachexia, suggesting transcriptional changes to mitochondrial gene expression happens concomitantly to functional impairments previously published. In contrast, the JAK-STAT pathway was upregulated in both the early and late stages of CC. Additionally, we observed a consistent downregulation of Type-II Interferon signaling genes in females, which was associated with protection in skeletal muscle atrophy despite systemic cachexia. Upregulation of Interferon signaling was noted in the gastrocnemius muscle of cachectic and atrophic male mice. Comparison of female tumor-bearing mice with males revealed ~ 70% of DEGs were distinct between sexes in cachectic animals, demonstrating dimorphic mechanisms of CC.

CONCLUSION

Our findings suggest biphasic disruptions in the transcriptome of female LLC tumor-bearing mice: an early phase associated with ECM remodeling and a late phase, accompanied by the onset of systemic cachexia, affecting overall muscle energy metabolism. Notably, ~ 2/3 of DEGs in CC are biologically sex-specific, providing evidence of dimorphic mechanisms of cachexia between sexes. Downregulation of Type-II Interferon signaling genes appears specific to CC development in females, suggesting a new biological sex-specific marker of CC not reliant on the loss of muscle mass, that might represent a protective mechanism against muscle loss in CC in female mice.

Mechanisms of ferroptosis with immune infiltration and inflammatory response in rotator cuff injury

The processes driving ferroptosis and rotator cuff (RC) inflammation are yet unknown. The mechanism of ferroptosis and inflammation involved in the development of RC tears was investigated. The Gene Expression Omnibus database was used to obtain the microarray data relevant to the RC tears for further investigation. In this study, we created an RC tears rat model for in vivo experimental validation. For the additional function enrichment analysis, 10 hub ferroptosis-related genes were chosen to construct the correlation regulation network. In RC tears, it was discovered that genes related to hub ferroptosis and hub inflammatory response were strongly correlated. The outcomes of in vivo tests showed that RC tears were related to Cd68-Cxcl13, Acsl4-Sat1, Acsl3-Eno3, Acsl3-Ccr7, and Ccr7-Eno3 pairings in regulating ferroptosis and inflammatory response. Thus, our results show an association between ferroptosis and inflammation, providing a new avenue to explore the clinical treatment of RC tears.

Zfp697 is an RNA-binding protein that regulates skeletal muscle inflammation and regeneration

Muscular atrophy is a mortality risk factor that happens with disuse, chronic disease, and aging. Recovery from atrophy requires changes in several cell types including muscle fibers, and satellite and immune cells. Here we show that Zfp697/ZNF697 is a damage-induced regulator of muscle regeneration, during which its expression is transiently elevated. Conversely, sustained Zfp697 expression in mouse muscle leads to a gene expression signature of chemokine secretion, immune cell recruitment, and extracellular matrix remodeling. Myofiber-specific Zfp697 ablation hinders the inflammatory and regenerative response to muscle injury, compromising functional recovery. We uncover Zfp697 as an essential interferon gamma mediator in muscle cells, interacting primarily with ncRNAs such as the pro-regenerative miR-206. In sum, we identify Zfp697 as an integrator of cell-cell communication necessary for tissue regeneration.

Macrophage Involvement in Aging-Associated Skeletal Muscle Regeneration

The skeletal muscle is a dynamic organ composed of contractile muscle fibers, connective tissues, blood vessels and nerve endings. Its main function is to provide motility to the body, but it is also deeply involved in systemic metabolism and thermoregulation. The skeletal muscle frequently encounters microinjury or trauma, which is primarily repaired by the coordinated actions of muscle stem cells (satellite cells, SCs), fibro-adipogenic progenitors (FAPs), and multiple immune cells, particularly macrophages. During aging, however, the capacity of skeletal muscle to repair and regenerate declines, likely contributing to sarcopenia, an age-related condition defined as loss of muscle mass and function. Recent studies have shown that resident macrophages in skeletal muscle are highly heterogeneous, and their phenotypes shift during aging, which may exacerbate skeletal muscle deterioration and inefficient regeneration. In this review, we highlight recent insight into the heterogeneity and functional roles of macrophages in skeletal muscle regeneration, particularly as it declines with aging.

Altered T cell infiltration and enrichment of leukocyte regulating pathways within aged skeletal muscle are associated impaired muscle function following influenza infection

Older adults have diminished immune responses that increase susceptibility to infectious diseases, such as influenza (flu). In older adults, flu infection can lead to hospitalization, catastrophic disability, and mortality. We previously demonstrated severe and prolonged muscle degradation and atrophy in aged mice during flu infection. Here, we utilized an unbiased transcriptomic analysis to elucidate mechanisms of flu-induced muscular declines in a mouse model. Our results showed age-related gene expression differences including downregulation of genes associated with muscle regeneration and organization and upregulation of genes associated with pro-inflammatory cytokines and migratory immune pathways in aged mice when compared to young. Pathway analysis revealed significant enrichment of leukocyte migration and T cell activation pathways in the aged muscle during infection. Intramuscular CD4 T cells increased in both young and aged mice during infection, while intramuscular CD8 T cells increased exclusively in aged muscle. CD4 T cells in young muscle were regulatory T cells (Treg), while those in aged were T follicular helper (Tfh) and Th2 cells. Correspondingly, IL-33, an important cytokine for Treg accumulation within tissue, increased only in young flu-infected muscle. Conversely, CXCL10 (IP-10) increased only in aged muscle suggesting a continued recruitment of CD8 T cells into the aged muscle during flu infection. Overall, our findings elucidate a link between flu-induced disability and dysregulated intracellular T cell recruitment into flu-injured muscle with aging. Furthermore, we uncovered potential pathways involved that can be targeted to develop preventative and therapeutic interventions to avert disability and maintain independence following infection.

Aging disrupts MANF-mediated immune modulation during skeletal muscle regeneration

Age-related decline in skeletal muscle regenerative capacity is multifactorial, yet the contribution of immune dysfunction to regenerative failure is unknown. Macrophages are essential for effective debris clearance and muscle stem cell activity during muscle regeneration, but the regulatory mechanisms governing macrophage function during muscle repair are largely unexplored. Here, we uncover a new mechanism of immune modulation operating during skeletal muscle regeneration that is disrupted in aged animals and relies on the regulation of macrophage function. The immune modulator mesencephalic astrocyte-derived neurotrophic factor (MANF) is induced following muscle injury in young mice but not in aged animals, and its expression is essential for regenerative success. Regenerative impairments in aged muscle are associated with defects in the repair-associated myeloid response similar to those found in MANF-deficient models and could be improved through MANF delivery. We propose that restoring MANF levels is a viable strategy to improve myeloid response and regenerative capacity in aged muscle.

Global Long Noncoding RNA Expression Profiling of MSTN and FGF5 Double-Knockout Sheep Reveals the Key Gatekeepers of Skeletal Muscle Development

Improving livestock and poultry growth rates and increasing meat production are urgently needed worldwide. Previously, we produced a myostatin (MSTN) and fibroblast growth factor 5 (FGF5) double-knockout (MF^-/-) sheep by CRISPR Cas9 system to improve meat production, and also wool production. Both MF^-/- sheep and the F1 generation (MF^+/-) sheep showed an obvious "double-muscle" phenotype. In this study, we identified the expression profiles of long noncoding RNAs (lncRNAs) in wild-type and MF^+/- sheep, then screened out the key candidate lncRNAs that can regulate myogenic differentiation and skeletal muscle development. These key candidate lncRNAs can serve as critical gatekeepers for muscle contraction, calcium ion transport and skeletal muscle cell differentiation, apoptosis, autophagy, and skeletal muscle inflammation, further revealing that lncRNAs play crucial roles in regulating muscle phenotype in MF^+/- sheep. In conclusion, our newly identified lncRNAs may emerge as novel molecules for muscle development or muscle disease and provide a new reference for MSTN-mediated regulation of skeletal muscle development.

Mechanisms of skeletal muscle-tendon development and regeneration/healing as potential therapeutic targets

Skeletal muscle contraction is essential for the movement of our musculoskeletal system. Tendons and ligaments that connect the skeletal muscles to bones in the correct position at the appropriate time during development are also required for movement to occur. Since the musculoskeletal system is essential for maintaining basic bodily functions as well as enabling interactions with the environment, dysfunctions of these tissues due to disease can significantly reduce quality of life. Unfortunately, as people live longer, skeletal muscle and tendon/ligament diseases are becoming more common. Sarcopenia, a disease in which skeletal muscle function declines, and tendinopathy, which involves chronic tendon dysfunction, are particularly troublesome because there have been no significant advances in their treatment. In this review, we will summarize previous reports on the development and regeneration/healing of skeletal muscle and tendon tissues, including a discussion of the molecular and cellular mechanisms involved that may be used as potential therapeutic targets.

Cellular interplay in skeletal muscle regeneration and wasting: insights from animal models

Skeletal muscle wasting, whether related to physiological ageing, muscle disuse or to an underlying chronic disease, is a key determinant to quality of life and mortality. However, cellular basis responsible for increased catabolism in myocytes often remains unclear. Although myocytes represent the vast majority of skeletal muscle cellular population, they are surrounded by numerous cells with various functions. Animal models, mostly rodents, can help to decipher the mechanisms behind this highly dynamic process, by allowing access to every muscle as well as time-course studies. Satellite cells (SCs) play a crucial role in muscle regeneration, within a niche also composed of fibroblasts and vascular and immune cells. Their proliferation and differentiation is altered in several models of muscle wasting such as cancer, chronic kidney disease or chronic obstructive pulmonary disease (COPD). Fibro-adipogenic progenitor cells are also responsible for functional muscle growth and repair and are associated in disease to muscle fibrosis such as in chronic kidney disease. Other cells have recently proven to have direct myogenic potential, such as pericytes. Outside their role in angiogenesis, endothelial cells and pericytes also participate to healthy muscle homoeostasis by promoting SC pool maintenance (so-called myogenesis-angiogenesis coupling). Their role in chronic diseases muscle wasting has been less studied. Immune cells are pivotal for muscle repair after injury: Macrophages undergo a transition from the M1 to the M2 state along with the transition between the inflammatory and resolutive phase of muscle repair. T regulatory lymphocytes promote and regulate this transition and are also able to activate SC proliferation and differentiation. Neural cells such as terminal Schwann cells, motor neurons and kranocytes are notably implicated in age-related sarcopenia. Last, newly identified cells in skeletal muscle, such as telocytes or interstitial tenocytes could play a role in tissular homoeostasis. We also put a special focus on cellular alterations occurring in COPD, a chronic and highly prevalent respiratory disease mainly linked to tobacco smoke exposure, where muscle wasting is strongly associated with increased mortality, and discuss the pros and cons of animal models versus human studies in this context. Finally, we discuss resident cells metabolism and present future promising leads for research, including the use of muscle organoids.

Protein therapy of skeletal muscle atrophy and mechanism by angiogenic factor AGGF1

BACKGROUND

Skeletal muscle atrophy is a common condition without a pharmacologic therapy. AGGF1 encodes an angiogenic factor that regulates cell differentiation, proliferation, migration, apoptosis, autophagy and endoplasmic reticulum stress, promotes vasculogenesis and angiogenesis and successfully treats cardiovascular diseases. Here, we report the important role of AGGF1 in the pathogenesis of skeletal muscle atrophy and attenuation of muscle atrophy by AGGF1.

METHODS

In vivo studies were carried out in impaired leg muscles from patients with lumbar disc herniation, two mouse models for skeletal muscle atrophy (denervation and cancer cachexia) and heterozygous Aggf1^+/- mice. Mouse muscle atrophy phenotypes were characterized by body weight and myotube cross-sectional areas (CSA) using H&E staining and immunostaining for dystrophin. Molecular mechanistic studies include co-immunoprecipitation (Co-IP), western blotting, quantitative real-time PCR analysis and immunostaining analysis.

RESULTS

Heterozygous Aggf1^+/- mice showed exacerbated phenotypes of reduced muscle mass, myotube CSA, MyHC (myosin heavy chain) and α-actin, increased inflammation (macrophage infiltration), apoptosis and fibrosis after denervation and cachexia. Intramuscular and intraperitoneal injection of recombinant AGGF1 protein attenuates atrophy phenotypes in mice with denervation (gastrocnemius weight 81.3 ± 5.7 mg vs. 67.3 ± 5.1 mg for AGGF1 vs. buffer; P < 0.05) and cachexia (133.7 ± 4.7 vs. 124.3 ± 3.2; P < 0.05). AGGF1 expression undergoes remodelling and is up-regulated in gastrocnemius and soleus muscles from atrophy mice and impaired leg muscles from patients with lumbar disc herniation by 50-60% (P < 0.01). Mechanistically, AGGF1 interacts with TWEAK (tumour necrosis factor-like weak inducer of apoptosis), which reduces interaction between TWEAK and its receptor Fn14 (fibroblast growth factor-inducing protein 14). This leads to inhibition of Fn14-induced NF-kappa B (NF-κB) p65 phosphorylation, which reduces expression of muscle-specific E3 ubiquitin ligase MuRF1 (muscle RING finger 1), resulting in increased MyHC and α-actin and partial reversal of atrophy phenotypes. Autophagy is reduced in Aggf1^+/- mice due to inhibition of JNK (c-Jun N-terminal kinase) activation in denervated and cachectic muscles, and AGGF1 treatment enhances autophagy in two atrophy models by activating JNK. In impaired leg muscles of patients with lumbar disc herniation, MuRF1 is up-regulated and MyHC and α-actin are down-regulated; these effects are reversed by AGGF1 by 50% (P < 0.01).

CONCLUSIONS

These results indicate that AGGF1 is a novel regulator for the pathogenesis of skeletal muscle atrophy and attenuates skeletal muscle atrophy by promoting autophagy and inhibiting MuRF1 expression through a molecular signalling pathway of AGGF1-TWEAK/Fn14-NF-κB. More importantly, the results indicate that AGGF1 protein therapy may be a novel approach to treat patients with skeletal muscle atrophy.

Interferon regulates neural stem cell function at all ages by orchestrating mTOR and cell cycle

Stem cells show intrinsic interferon signalling, which protects them from viral infections at all ages. In the ageing brain, interferon signalling also reduces the ability of stem cells to activate. Whether these functions are linked and at what time interferons start taking on a role in stem cell functioning is unknown. Additionally, the molecular link between interferons and activation in neural stem cells and how this relates to progenitor production is not well understood. Here we combine single-cell transcriptomics, RiboSeq and mathematical models of interferon to show that this pathway is important for proper stem cell function at all ages in mice. Interferon orchestrates cell cycle and mTOR activity to post-transcriptionally repress Sox2 and induces quiescence. The interferon response then decreases in the subsequent maturation states. Mathematical simulations indicate that this regulation is beneficial for the young and harmful for the old brain. Our study establishes molecular mechanisms of interferon in stem cells and interferons as genuine regulators of stem cell homeostasis and a potential therapeutic target to repair the ageing brain.

Single-cell RNA-seq reveals interferon-induced guanylate-binding proteins are linked with sarcopenia

BACKGROUND

Sarcopenia is defined as an age-related progressive loss of muscle mass and/or strength. Although different factors can contribute to this disease, the underlying mechanisms remain unclear. We assessed transcriptional heterogeneity in skeletal muscles from sarcopenic and control mice at single-cell resolution.

METHODS

A mouse model was established to study sarcopenic skeletal muscles. Single-cell RNA-seq was performed on tibialis anterior (TA) muscle cells collected from sarcopenic and control mice. A series of bioinformatic analyses were carried out to identify and compare different cell types under different conditions. Immunofluorescence staining and western blotting were used to validate the findings from single-cell experiments. Tube formation assays were conducted to further evaluate the effects of Gbp2 on endothelial cells during angiogenesis.

RESULTS

A murine sarcopenia model was successfully established using a senescence-accelerated mouse strain (SAMP6, n = 5). Sarcopenia phenotype was induced by administration of dexamethasone (20 mg/kg) and reduced physical activity. Senescence-resistant mice strain (SAMR1) and SAMP6 strain with similar activity but injected with PBS were recruited as two control groups. As signs of sarcopenia, body weight, muscle cell counts and cross-sectional fibre area were all significantly decreased in sarcopenic mice (P value = 0.004, 0.03 and 0.035, respectively). After quality control, 13 612 TA muscle single-cell transcriptomes were retained for analysis. Fourteen cell clusters were identified from the profiled cells. Among them, two distinct endothelial subtypes were found to be dominant in the sarcopenia group (42.2% cells) and in the two control groups (59.1% and 47.9% cells), respectively. 191 differentially expressed genes were detected between the two endothelial subtypes. Sarcopenia-specific endothelial cell subtype exhibited a dramatic increase in the interferon family genes and the interferon-inducible guanylate-binding protein (GBP) family gene expressions. For example, Igtp and Gbp2 in sarcopenic endothelial cells were 5.4 and 13.3 times higher than those in the control groups, respectively. We further validated our findings in muscle specimens of sarcopenia patients and observed that GBP2 levels were increased in endothelial cells of a subset of patients (11 of 40 patients, 27.5%), and we identified significantly higher CD31 and GBP2 co-localization (P value = 0.001128). Finally, we overexpressed Gbp2 in human umbilical vein endothelial cells in vitro. The endothelial cells with elevated Gbp2 expression displayed compromised tube formation.

CONCLUSIONS

Our single-cell-based results suggested that endothelial cells may play critical roles in sarcopenia development through interferon-GBP signalling pathways, highlighting new therapeutic directions to slow down or even reverse age-related sarcopenia.

Novel Approaches to Program Cells to Differentiate into Cardiomyocytes in Myocardial Regeneration

With heart failure (HF) being one of the leading causes of hospitalization and death worldwide, multiple stem cell therapies have been attempted to accelerate the regeneration of the infarct zone. Versatile strategies have emerged to establish the cell candidates of cardiomyocyte lineage for regenerative cardiology. This article illustrates critical insights into the emerging technologies, current approaches, and translational promises on the programming of diverse cell types for cardiac regeneration.

Atrophic skeletal muscle fibre-derived small extracellular vesicle miR-690 inhibits satellite cell differentiation during ageing

BACKGROUND

Sarcopenia is a common and progressive skeletal muscle disorder characterized by atrophic muscle fibres and contractile dysfunction. Accumulating evidence shows that the number and function of satellite cells (SCs) decline and become impaired during ageing, which may contribute to impaired regenerative capacity. A series of myokines/small extracellular vesicles (sEVs) released from muscle fibres regulate metabolism in muscle and extramuscular tissues in an autocrine/paracrine/endocrine manner during muscle atrophy. It is still unclear whether myokines/sEVs derived from muscle fibres can affect satellite cell function during ageing.

METHODS

Aged mice were used to investigate changes in the myogenic capacity of SCs during ageing-induced muscle atrophy. The effects of atrophic myotube-derived sEVs on satellite cell differentiation were investigated by biochemical methods and immunofluorescence staining. Small RNA sequencing was performed to identify differentially expressed sEV microRNAs (miRNAs) between the control myotubes and atrophic myotubes. The target genes of the miRNA were predicted by bioinformatics analysis and verified by luciferase activity assays. The effects of identified miRNA on the myogenic capacity of SCs in vivo were investigated by intramuscular injection of adeno-associated virus (AAV) to overexpress or silence miRNA in skeletal muscle.

RESULTS

Our study showed that the myogenic capacity of SCs was significantly decreased (50%, n = 6, P < 0.001) in the tibialis anterior muscle of aged mice. We showed that atrophic myotube-derived sEVs inhibited satellite cell differentiation in vitro (n = 3, P < 0.001) and in vivo (35%, n = 6, P < 0.05). We also found that miR-690 was the most highly enriched miRNA among all the screened sEV miRNAs in atrophic myotubes [Log₂ (Fold Change) = 7, P < 0.001], which was verified in the atrophic muscle of aged mice (threefold, n = 6, P < 0.001) and aged men with mean age of 71 ± 5.27 years (2.8-fold, n = 10, P < 0.001). MiR-690 can inhibit myogenic capacity of SCs by targeting myocyte enhancer factor 2, including Mef2a, Mef2c and Mef2d, in vitro (n = 3, P < 0.05) and in vivo (n = 6, P < 0.05). Specific silencing of miR-690 in the muscle can promote satellite cell differentiation (n = 6, P < 0.001) and alleviate muscle atrophy in aged mice (n = 6, P < 0.001).

CONCLUSIONS

Our study demonstrated that atrophic muscle fibre-derived sEV miR-690 may inhibit satellite cell differentiation by targeting myocyte enhancer factor 2 during ageing.

Emerging cellular senescence-centric understanding of immunological aging and its potential modulation through dietary bioactive components

Immunological aging is strongly associated with the observable deleterious effects of human aging. Our understanding of the causes, effects, and therapeutics of aging immune cells has long been considered within the sole purview of immunosenescence. However, it is being progressively realized that immunosenescence may not be the only determinant of immunological aging. The cellular senescence-centric theory of aging proposes a more fundamental and specific role of immune cells in regulating senescent cell (SC) burden in aging tissues that has augmented the notion of senescence immunotherapy. Now, in addition, several emerging studies are suggesting that cellular senescence itself may be prevalent in aging immune cells, and that senescent immune cells exhibiting characteristic markers of cellular senescence, similar to non-leucocyte cells, could be among the key drivers of various facets of physiological aging. The present review integrates the current knowledge related to immunosenescence and cellular senescence in immune cells per se, and aims at providing a cohesive overview of these two phenomena and their significance in immunity and aging. We present evidence and rationalize that understanding the extent and impact of cellular senescence in immune cells vis-à-vis immunosenescence is necessary for truly comprehending the notion of an 'aged immune cell'. In addition, we also discuss the emerging significance of dietary factors such as phytochemicals, probiotic bacteria, fatty acids, and micronutrients as possible modulators of immunosenescence and cellular senescence. Evidence and opportunities related to nutritional bioactive components and immunological aging have been deliberated to augment potential nutrition-oriented immunotherapy during aging.

Inflammaging: Implications in Sarcopenia

In a world in which life expectancy is increasing, understanding and promoting healthy aging becomes a contemporary demand. In the elderly, a sterile, chronic and low-grade systemic inflammation known as "inflammaging" is linked with many age-associated diseases. Considering sarcopenia as a loss of strength and mass of skeletal muscle related to aging, correlations between these two terms have been proposed. Better knowledge of the immune system players in skeletal muscle would help to elucidate their implications in sarcopenia. Characterizing the activators of damage sensors and the downstream effectors explains the inference with skeletal muscle performance. Sarcopenia has also been linked to chronic diseases such as diabetes, metabolic syndrome and obesity. Implications of inflammatory signals from these diseases negatively affect skeletal muscle. Autophagic mechanisms are closely related with the inflammasome, as autophagy eliminates stress signaling sent by damage organelles, but also acts with an immunomodulatory function affecting immune cells and cytokine release. The use of melatonin, an antioxidant, ROS scavenger and immune and autophagy modulator, or senotherapeutic compounds targeting senescent cells could represent strategies to counteract inflammation. This review aims to present the many factors regulating skeletal muscle inflammaging and their major implications in order to understand the molecular mechanisms involved in sarcopenia.

Integrative bioinformatics analysis to explore a robust diagnostic signature and landscape of immune cell infiltration in sarcoidosis

Background

The unknown etiology of sarcoidosis with variable clinical features leads to delayed diagnosis and limited therapeutic strategies. Hence, exploring the latent mechanisms and constructing an accessible and reliable diagnostic model of sarcoidosis is vital for innovative therapeutic approaches to improve prognosis.

Methods

This retrospective study analyzed transcriptomes from 11 independent sarcoidosis cohorts, comprising 313 patients and 400 healthy controls. The weighted gene co-expression network analysis (WGCNA) and differentially expressed gene (DEG) analysis were performed to identify molecular biomarkers. Machine learning was employed to fit a diagnostic model. The potential pathogenesis and immune landscape were detected by bioinformatics tools.

Results

A 10-gene signature SARDS consisting of GBP1, LEF1, IFIT3, LRRN3, IFI44, LHFPL2, RTP4, CD27, EPHX2, and CXCL10 was further constructed in the training cohorts by the LASSO algorithm, which performed well in the four independent cohorts with the splendid AUCs ranging from 0.938 to 1.000. The findings were validated in seven independent publicly available gene expression datasets retrieved from whole blood, PBMC, alveolar lavage fluid cells, and lung tissue samples from patients with outstanding AUCs ranging from 0.728 to 0.972. Transcriptional signatures associated with sarcoidosis revealed a potential role of immune response in the development of the disease through bioinformatics analysis.

Conclusions

Our study identified and validated molecular biomarkers for the diagnosis of sarcoidosis and constructed the diagnostic model SARDS to improve the accuracy of early diagnosis of the disease.

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.

TNFα and IFNγ cooperate for efficient pro- to anti-inflammatory transition of macrophages during muscle regeneration

IFNγ is traditionally known as a proinflammatory cytokine with diverse roles in antimicrobial and antitumor immunity. Yet, findings regarding its sources and functions during the regeneration process following a sterile injury are conflicting. Here, we show that natural killer (NK) cells are the main source of IFNγ in regenerating muscle. Beyond this cell population, IFNγ production is limited to a small population of T cells. We further show that NK cells do not play a major role in muscle regeneration following an acute injury or in dystrophic mice. Surprisingly, the absence of IFNγ per se also has no effect on muscle regeneration following an acute injury. However, the role of IFNγ is partially unmasked when TNFα is also neutralized, suggesting a compensatory mechanism. Using transgenic mice, we showed that conditional inhibition of IFNGR1 signaling in muscle stem cells or fibro-adipogenic progenitors does not play a major role in muscle regeneration. In contrast to common belief, we found that IFNγ is not present in the early inflammatory phase of the regeneration process but rather peaks when macrophages are acquiring an anti-inflammatory phenotype. Further transcriptomic analysis suggests that IFNγ cooperates with TNFα to regulate the transition of macrophages from pro- to anti-inflammatory states. The absence of the cooperative effect of these cytokines on macrophages, however, does not result in significant regeneration impairment likely due to the presence of other compensatory mechanisms. Our findings support the arising view of IFNγ as a pleiotropic inflammatory regulator rather than an inducer of the inflammatory response.

The promising roles of macrophages in geriatric hip fracture

As aging becomes a global burden, the incidence of hip fracture (HF), which is the most common fracture in the elderly population and can be fatal, is rapidly increasing, and its extremely high fatality rate places significant medical and financial burdens on patients. Fractures trigger a complex set of immune responses, and recent studies have shown that with aging, the immune system shows decreased activity or malfunctions in a process known as immune senescence, leading to disease and death. These phenomena are the reasons why elderly individuals typically exhibit chronically low levels of inflammation and increased rates of infection and chronic disease. Macrophages, which are key players in the inflammatory response, are critical in initiating the inflammatory response, clearing pathogens, controlling the innate and adaptive immune responses and repairing damaged tissues. Tissue-resident macrophages (TRMs) are widely present in tissues and perform immune sentinel and homeostatic functions. TRMs are combinations of macrophages with different functions and phenotypes that can be directly influenced by neighboring cells and the microenvironment. They form a critical component of the first line of defense in all tissues of the body. Immune system disorders caused by aging could affect the biology of macrophages and thus the cascaded immune response after fracture in various ways. In this review, we outline recent studies and discuss the potential link between monocytes and macrophages and their potential roles in HF in elderly individuals.

Inflammaging: The ground for sarcopenia?

Sarcopenia is a progressive skeletal muscle disease that occurs most commonly in the elderly population, contributing to increased costs and hospitalization. Exercise and nutritional therapy have been proven to be effective for sarcopenia, and some drugs can also alleviate declines in muscle mass and function due to sarcopenia. However, there is no specific pharmacological treatment for sarcopenia at present. This review will mainly discuss the relationship between inflammaging and sarcopenia. The increased secretion of proinflammatory cytokines with aging may be because of cellular senescence, immunosenescence, alterations in adipose tissue, damage-associated molecular patterns (DAMPs), and gut microbes due to aging. These sources of inflammaging can impact the sarcopenia process through direct or indirect pathways. Conversely, sarcopenia can also aggravate the process of inflammaging, creating a vicious cycle. Targeting sources of inflammaging can influence muscle function, which could be considered a therapeutic target for sarcopenia. Moreover, not only proinflammatory cytokines but also anti-inflammatory cytokines can influence muscle and inflammation and participate in the progression of sarcopenia. This review focuses on the effects of TNF-α, IL-6, and IL-10, which can be detected in plasma. Therefore, clearing chronic inflammation by targeting proinflammatory cytokines (TNF-α, IL-1, IL-6) and the inflammatory pathway (JAK/STAT, autophagy, NF-κB) may be effective in treating sarcopenia.

Inhibiting uptake of extracellular vesicles derived from senescent bone marrow mesenchymal stem cells by muscle satellite cells attenuates sarcopenia

Objective

Osteoporosis is associated with senescence of bone marrow mesenchymal stem cells (BMSCs). Extracellular vesicles derived from senescent BMSCs (BMSC-EVs) could be uptaken by muscle satellite cells (SCs). We hypothesized that inhibiting the uptake of harmful BMSC-EVs by SCs could prevent patients with osteoporosis complicated with sarcopenia.

Methods

Bioinformatics analysis was used to analyze senescent SCs. Myogenic potential of SCs was measured using myogenesis assay and immunofluorescence while muscle atrophy was measured using histological evaluation. And the interaction of cluster of differentiation (CD) 81 and the membrane proteins of SCs was verified using biotin pulldown assay.. CD81-specific siRNA (si-CD81) was used to knockdown CD81 and anti-CD81 antibody (anti-CD81 Ab) was used to block CD81.

Results

Differentially expressed genes in senescent SCs were enriched in muscle cell differentiation. The myogenic potential of senescent SCs was significantly decreased. Senescent BMSC-EVs impaired myogenesis of SCs. CD81 on the surface of BMSC-EVs could bind to membrane proteins of SCs. Both knockdown of CD81 and blocking CD81 prevented the uptake of senescent BMSC-EVs by SCs, thus relieving harmful effects of senescent BMSC-EVs on muscle atrophy.

Conclusion

Blocking CD81 on the surface of senescent BMSC-EVs attenuates sarcopenia in aged mice, which could be useful for prevention of sarcopenia in patients with osteoporosis in clinical practice.

Translational potential of this article

Inhibiting uptake of extracellular vesicles derived from senescent bone marrow mesenchymal stem cells by muscle satellite cells can prevent muscle atrophy in aged mice and has potential for application in treating sarcopenia.

Anatomical Transcriptome Atlas of the Male Mouse Reproductive System During Aging

The elderly males undergo degenerative fertility and testicular endocrine function that jeopardize the reproductive health and well-being. However, the mechanisms underlying reproductive aging are unclear. Here, we tried to address this by investigating the phenotypes and transcriptomes of seven regions of the male mouse reproductive tract: the testis, efferent ductules, initial segment, caput, corpus and cauda epididymidis, and vas deferens, in adult (3 months) and aged (21 months) mice. Quantitative PCR, immunohistochemistry, immunofluorescent staining, and enzyme-linked immunosorbent assay were performed for the analysis of gene expression in mice, human tissues, and semen samples. Aged male mice showed both systematic and reproductive changes, and remarkable histological changes were detected in the testis and proximal epididymis. Transcriptomes of the male reproductive tract were mapped, and a series of region-specific genes were identified and validated in mouse and/or human tissues, including Protamine 1 (Prm2), ADAM metallopeptidase domain 28 (Adam28), Ribonuclease A family member 13 (Rnase13), WAP four-disulfide core domain 13 (Wfdc13), and Wfdc9. Meanwhile, age-related transcriptome changes of different regions of the male reproductive tract were characterized. Notably, increased immune response was functionally related to the male reproductive aging, especially the T cell activation. An immune response-associated factor, phospholipase A2 group IID (Pla2g2d), was identified as a potential biomarker for reproductive aging in mice. And the PLA2G2D level in human seminal plasma surged at approximately 35 years of age. Furthermore, we highlighted Protein tyrosine phosphatase receptor type C (Ptprc), Lymphocyte protein tyrosine kinase (Lck), Microtubule associated protein tau (Mapt), and Interferon induced protein with tetratricopeptide repeats 3 (Ifit3) as critical molecules in the aging of initial segment, caput, caput, and cauda epididymidis, respectively. This study provides an RNA-seq resource for the male reproductive system during aging in mice, and is expected to improve our understanding of male reproductive aging and infertility.

Therapeutic Application of Extracellular Vesicles-Capsulated Adeno-Associated Virus Vector via nSMase2/Smpd3, Satellite, and Immune Cells in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by loss-of-function mutations in the dystrophin gene on chromosome Xp21. Disruption of the dystrophin-glycoprotein complex (DGC) on the cell membrane causes cytosolic Ca2+ influx, resulting in protease activation, mitochondrial dysfunction, and progressive myofiber degeneration, leading to muscle wasting and fragility. In addition to the function of dystrophin in the structural integrity of myofibers, a novel function of asymmetric cell division in muscular stem cells (satellite cells) has been reported. Therefore, it has been suggested that myofiber instability may not be the only cause of dystrophic degeneration, but rather that the phenotype might be caused by multiple factors, including stem cell and myofiber functions. Furthermore, it has been focused functional regulation of satellite cells by intracellular communication of extracellular vesicles (EVs) in DMD pathology. Recently, a novel molecular mechanism of DMD pathogenesis-circulating RNA molecules-has been revealed through the study of target pathways modulated by the Neutral sphingomyelinase2/Neutral sphingomyelinase3 (nSMase2/Smpd3) protein. In addition, adeno-associated virus (AAV) has been clinically applied for DMD therapy owing to the safety and long-term expression of transduction genes. Furthermore, the EV-capsulated AAV vector (EV-AAV) has been shown to be a useful tool for the intervention of DMD, because of the high efficacy of the transgene and avoidance of neutralizing antibodies. Thus, we review application of AAV and EV-AAV vectors for DMD as novel therapeutic strategy.

Stem cell aging in the skeletal muscle: The importance of communication

Adult stem cells sustain tissue homeostasis and regeneration; their functional decline is often linked to aging, which is characterized by the progressive loss of physiological functions across multiple tissues and organs. The resident stem cells in skeletal muscle, termed satellite cells, are normally quiescent but activate upon injury to reconstitute the damaged tissue. In this review, we discuss the current understanding of the molecular processes that contribute to the functional failure of satellite cells during aging. This failure is due not only to intrinsic changes but also to extrinsic factors, most of which are still undefined but originate from the muscle tissue microenvironment of the satellite cells (the niche), or from the systemic environment. We also highlight the emerging applications of the powerful single-cell sequencing technologies in the study of skeletal muscle aging, particularly in the heterogeneity of the satellite cell population and the molecular interaction of satellite cells and other cell types in the niche. An improved understanding of how satellite cells communicate with their environment, and how this communication is perturbed with aging, will be helpful for defining countermeasures against loss of muscle regenerative capacity in sarcopenia.

Dynamics of muscle growth and regeneration: Lessons from the teleost

The processes of myogenesis during both development and regeneration share a number of similarities across both amniotes and teleosts. In amniotes, the process of muscle formation is considered largely biphasic, with developmental myogenesis occurring through hyperplastic fibre deposition and postnatal muscle growth driven through hypertrophy of existing fibres. In contrast, teleosts continue generating new muscle fibres during adult myogenesis through a process of eternal hyperplasia using a dedicated stem cell system termed the external cell layer. During developmental and regenerative myogenesis alike, muscle progenitors interact with their niche to receive cues guiding their transition into myoblasts and ultimately mature myofibres. During development, muscle precursors receive input from neighbouring embryological tissues; however, during repair, this role is fulfilled by other injury resident cell types, such as those of the innate immune response. Recent work has focused on the role of macrophages as a pro-regenerative cell type which provides input to muscle satellite cells during regenerative myogenesis. As zebrafish harbour a satellite cell system analogous to that of mammals, the processes of regeneration can be interrogated in vivo with the imaging intensive approaches afforded in the zebrafish system. This review discusses the strengths of zebrafish with a focus on both the similarities and differences to amniote myogenesis during both development and repair.

Structured presurgery prehabilitation for aged patients undergoing elective surgery significantly improves surgical outcomes and reduces cost: A nonrandomized sequential comparative prospective cohort study

Background

With increasing global life expectancy, the number of major surgeries performed on aged adults invariably increases. This study aimed to examine the effectiveness of a structured prehabilitative program for aged colorectal cancer patients in improving short‐term surgical outcomes.

Methods

A prospective philanthropically sponsored Programme for Enhanced Elderly Recovery at Sengkang General Hospital (PEERS) was initiated in February 2017 for patients ≥70‐years‐old who were due to undergo elective colectomies. These patients were put through a 2‐ to 4‐week‐long program before surgery, which included geriatric assessment, nutrition supplementation, and resistance training. They were compared with patients from a similar age group before PEERS was introduced (non‐PEERS).

Results

Fifty‐eight patients, with a median age of 78.5 (70–93) years, were recruited from a single institution to undergo PEERS. Baseline characteristics between the groups were similar. There was no significant improvement of anthropometric and functional characteristics before and after PEERS. Duration of hospitalization was shorter in the PEERS group (9 vs 11 days, P = 0.01). Both groups had similar 30‐days’ morbidity rates (8.6% vs 17.4%, P = 0.26). The PEERS group had significant improvement in their median EuroQol‐5 Dimension score (0.70 presurgery to 0.80 6‐months’ postsurgery, P = 0.01). After multivariate analysis, the average duration of hospitalization in the PEERS group was 6.8 days shorter (P = 0.018; CI, 1.2–12.4) after adjusting for modality of surgery and complications. This represented a cost saving of USD$11,838.80.

Conclusion

A standardized prehabilitation program for aged adults reduced the duration of hospitalization, improved the quality of life after surgery, and reduced costs.

Skeletal muscle aging, cellular senescence, and senotherapeutics: Current knowledge and future directions

Cellular senescence is a state of cell cycle arrest induced by several forms of metabolic stress. Senescent cells accumulate with advancing age and have a distinctive phenotype, characterized by profound chromatin alterations and a robust senescence-associated secretory phenotype (SASP) that exerts negative effects on tissue health, both locally and systemically. In preclinical models, pharmacological agents that eliminate senescent cells (senotherapeutics) restore health and youthful properties in multiple tissues. To date, however, very little is understood about the vulnerability of terminally-differentiated skeletal muscle fibers and the resident mononuclear cells that populate the interstitial microenvironment of skeletal muscle to senescence, and their contribution to the onset and progression of skeletal muscle loss and dysfunction with aging. Scientific advances in these areas have the potential to highlight new therapeutic approaches to optimize late-life muscle health. To this end, this review highlights the current evidence and the key questions that need to be addressed to advance the field's understanding of cellular senescence as a mediator of skeletal muscle aging and the potential for emerging senescent cell-targeting therapies to counter age-related deficits in muscle mass, strength, and function. This article is part of the Special Issue - Senolytics - Edited by Joao Passos and Diana Jurk.

Muscle fibrosis and maladaptation occur progressively in CKD and are rescued by dialysis

BACKGROUND

Skeletal muscle maladaptation accompanies chronic kidney disease (CKD) and negatively impacts physical function. Emphasis in CKD has historically been placed on muscle fiber intrinsic deficits, such as altered protein metabolism and atrophy. However, targeted treatment of fiber intrinsic dysfunction has produced limited improvement, whereas alterations within the fiber extrinsic environment have scarcely been examined.

METHODS

We investigated alterations to the skeletal muscle interstitial environment with deep cellular phenotyping of biopsies from patients with CKD compared to age-matched control participants and performed transcriptome profiling to define the molecular underpinnings of CKD-associated muscle impairments. We further examined changes in the observed muscle maladaptation following initiation of dialysis therapy for kidney failure.

RESULTS

Patients with CKD exhibited a progressive fibrotic muscle phenotype, which was associated with impaired regenerative capacity and lower vascular density. The severity of these deficits was strongly associated with the degree of kidney dysfunction. Consistent with these profound deficits, CKD was associated with broad alterations to the muscle transcriptome, including altered extracellular matrix organization, downregulated angiogenesis, and altered expression of pathways related to stem cell self-renewal. Remarkably, despite the seemingly advanced nature of this fibrotic transformation, dialysis treatment rescued these deficits, restoring a healthier muscle phenotype. Furthermore, after accounting for muscle atrophy, strength and endurance improved after dialysis initiation.

CONCLUSION

These data identify a dialysis-responsive muscle fibrotic phenotype in CKD and suggest that the early dialysis window presents a unique opportunity of improved muscle regenerative capacity during which targeted interventions may achieve maximal impact.

TRIAL REGISTRATION

NCT01452412FUNDING. NIH.

The Roles of Macrophages in Heart Regeneration and Repair After Injury

Although great advances have been made, the problem of irreversible myocardium loss due to the limited regeneration capacity of cardiomyocytes has not been fully solved. The morbidity and mortality of heart disease still remain high. There are many therapeutic strategies for treating heart disease, while low efficacy and high cost remain challenging. Abundant evidence has shown that both acute and chronic inflammations play a crucial role in heart regeneration and repair following injury. Macrophages, a primary component of inflammation, have attracted much attention in cardiac research in recent decades. The detailed mechanisms of the roles of macrophages in heart regeneration and repair are not completely understood, in part because of their complex subsets, various functions, and intercellular communications. The purpose of this review is to summarize the progress made in the understanding of macrophages, including recent reports on macrophage differentiation, polarization and function, and involvement in heart regeneration and repair. Also, we discuss progress in treatments, which may suggest directions for future research.

Influence of IGF-I serum concentration on muscular regeneration capacity in patients with sarcopenia

Background

Previous research has described a neuroprotective effect of IGF-I, supporting neuronal survival, axon growth and proliferation of muscle cells. Therefore, the association between IGF-I concentration, muscle histology and electrophysiological markers in a cohort of patients with sarcopenia dares investigation.

Methods

Measurement of serum concentrations of IGF-I and binding partners, electromyographic measurements with the MUNIX (Motor Unit Number Index) method and muscle biopsies were performed in 31 patients with acute hip fracture older age 60 years. Molecular markers for denervation (neural cell adhesion molecule NCAM) and proliferation markers (Ki67) were assessed by immunofluorescence staining of muscle biopsy tissue. Skeletal muscle mass by bioelectrical impedance analysis and hand-grip strength were measured to assess sarcopenia status according to EWGSOP2 criteria.

Results

Thirty-one patients (20 women) with a mean age of 80.6 ± 7.4 years were included. Concentrations of IGF-I and its binding partners were significantly associated with sarcopenia (ß = − 0.360; p = 0.047) and MUNIX (ß = 0.512; p = 0.005). Further, expression of NCAM (ß = 0.380; p = 0.039) and Ki67 (ß = 0.424; p = 0.022) showed significant associations to IGF-I concentrations.

Conclusions

The findings suggest a pathogenetic role of IGF-I in sarcopenia based on muscle denervation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04699-3.

Fusion and beyond: Satellite cell contributions to loading-induced skeletal muscle adaptation

Satellite cells support adult skeletal muscle fiber adaptations to loading in numerous ways. The fusion of satellite cells, driven by cell-autonomous and/or extrinsic factors, contributes new myonuclei to muscle fibers, associates with load-induced hypertrophy, and may support focal membrane damage repair and long-term myonuclear transcriptional output. Recent studies have also revealed that satellite cells communicate within their niche to mediate muscle remodeling in response to resistance exercise, regulating the activity of numerous cell types through various mechanisms such as secretory signaling and cell-cell contact. Muscular adaptation to resistance and endurance activity can be initiated and sustained for a period of time in the absence of satellite cells, but satellite cell participation is ultimately required to achieve full adaptive potential, be it growth, function, or proprioceptive coordination. While significant progress has been made in understanding the roles of satellite cells in adult muscle over the last few decades, many conclusions have been extrapolated from regeneration studies. This review highlights our current understanding of satellite cell behavior and contributions to adaptation outside of regeneration in adult muscle, as well as the roles of satellite cells beyond fusion and myonuclear accretion, which are gaining broader recognition.

Metabolipidomic profiling reveals an age-related deficiency of skeletal muscle pro-resolving mediators that contributes to maladaptive tissue remodeling

Specialized pro-resolving mediators actively limit inflammation and support tissue regeneration, but their role in age-related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography-tandem mass spectrometry and tested whether treatment with the pro-resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro-resolving mediators 8-oxo-RvD1, resolvin E3, and maresin 1, as well as many anti-inflammatory cytochrome P450-derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro-inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E₂ ) and 12-lipoxygenase (e.g., 12-hydroxy-eicosatetraenoic acid), but aged mice produced fewer markers of pro-resolving mediators including the lipoxins (15-hydroxy-eicosatetraenoic acid), D-resolvins/protectins (17-hydroxy-docosahexaenoic acid), E-resolvins (18-hydroxy-eicosapentaenoic acid), and maresins (14-hydroxy-docosahexaenoic acid). Similar absences of downstream pro-resolving mediators including lipoxin A₄ , resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro-resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non-steroidal anti-inflammatory drugs.

Macrophage function in the elderly and impact on injury repair and cancer

Older age is associated with deteriorating health, including escalating risk of diseases such as cancer, and a diminished ability to repair following injury. This rise in age-related diseases/co-morbidities is associated with changes to immune function, including in myeloid cells, and is related to immunosenescence. Immunosenescence reflects age-related changes associated with immune dysfunction and is accompanied by low-grade chronic inflammation or inflammageing. This is characterised by increased levels of circulating pro-inflammatory cytokines such as tumor necrosis factor (TNF), interleukin (IL)-1β and IL-6. However, in healthy ageing, there is a concomitant age-related escalation in anti-inflammatory cytokines such as transforming growth factor-β1 (TGF-β1) and IL-10, which may overcompensate to regulate the pro-inflammatory state. Key inflammatory cells, macrophages, play a role in cancer development and injury repair in young hosts, and we propose that their role in ageing in these scenarios may be more profound. Imbalanced pro- and anti-inflammatory factors during ageing may also have a significant influence on macrophage function and further impact the severity of age-related diseases in which macrophages are known to play a key role. In this brief review we summarise studies describing changes to inflammatory function of macrophages (from various tissues and across sexes) during healthy ageing. We also describe age-related diseases/co-morbidities where macrophages are known to play a key role, focussed on injury repair processes and cancer, plus comment briefly on strategies to correct for these age-related changes.