Macrophages Are Key Regulators of Stem Cells during Skeletal Muscle Regeneration and Diseases

Muscle regeneration is a closely regulated process that involves a variety of cell types such as satellite cells, myofibers, fibroadipogenic progenitors, endothelial cells, and inflammatory cells. Among these different cell types, macrophages emerged as a central actor coordinating the different cellular interactions and biological processes. Particularly, the transition of macrophages from their proinflammatory to their anti-inflammatory phenotype was shown to regulate inflammation, myogenesis, fibrosis, vascularization, and return to homeostasis. On the other hand, deregulation of macrophage accumulation or polarization in chronic degenerative muscle disorders was shown to impair muscle regeneration. Considering the key roles of macrophages in skeletal muscle, they represent an attractive target for new therapeutic approaches aiming at mitigating various muscle disorders. This review aims at summarizing the novel insights into macrophage heterogeneity, plasticity, and functions in skeletal muscle homeostasis, regeneration, and disease.

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Abcg2 labels multiple cell types in skeletal muscle and participates in muscle regeneration

The Journal of Cell Biology ◽

10.1083/jcb.201103159 ◽

2011 ◽

Vol 195 (1) ◽

pp. 147-163 ◽

Cited By ~ 35

Author(s):

Michelle J. Doyle ◽

Sheng Zhou ◽

Kathleen Kelly Tanaka ◽

Addolorata Pisconti ◽

Nicholas H. Farina ◽

...

Keyword(s):

Skeletal Muscle ◽

Satellite Cells ◽

Muscle Regeneration ◽

Side Population ◽

Cell Types ◽

Lineage Tracing ◽

Skeletal Muscle Regeneration ◽

Genetic Lineage ◽

Multiple Cell ◽

A Minor

Skeletal muscle contains progenitor cells (satellite cells) that maintain and repair muscle. It also contains muscle side population (SP) cells, which express Abcg2 and may participate in muscle regeneration or may represent a source of satellite cell replenishment. In Abcg2-null mice, the SP fraction is lost in skeletal muscle, although the significance of this loss was previously unknown. We show that cells expressing Abcg2 increased upon injury and that muscle regeneration was impaired in Abcg2-null mice, resulting in fewer centrally nucleated myofibers, reduced myofiber size, and fewer satellite cells. Additionally, using genetic lineage tracing, we demonstrate that the progeny of Abcg2-expressing cells contributed to multiple cell types within the muscle interstitium, primarily endothelial cells. After injury, Abcg2 progeny made a minor contribution to regenerated myofibers. Furthermore, Abcg2-labeled cells increased significantly upon injury and appeared to traffic to muscle from peripheral blood. Together, these data suggest an important role for Abcg2 in positively regulating skeletal muscle regeneration.

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Regulation of Skeletal Muscle Satellite Cell Differentiation by Omega-3 Polyunsaturated Fatty Acids: A Critical Review

Frontiers in Physiology ◽

10.3389/fphys.2021.682091 ◽

2021 ◽

Vol 12 ◽

Author(s):

Peter O. Isesele ◽

Vera C. Mazurak

Keyword(s):

Skeletal Muscle ◽

Fatty Acids ◽

Polyunsaturated Fatty Acids ◽

Muscle Regeneration ◽

Critical Review ◽

Myogenic Differentiation ◽

Skeletal Muscle Regeneration ◽

Omega 3 ◽

Muscle Disorders ◽

Myogenic Progenitor Cells

Skeletal muscle is composed of multinuclear cells called myofibres, which are formed by the fusion of myoblasts during development. The size of the muscle fiber and mass of skeletal muscle are altered in response to several pathological and physiological conditions. Skeletal muscle regeneration is primarily mediated by muscle stem cells called satellite cells (SCs). In response to injury, these SCs replenish myogenic progenitor cells to form new myofibers to repair damaged muscle. During myogenesis, activated SCs proliferate and differentiate to myoblast and then fuse with one another to form muscle fibers. A reduced number of SCs and an inability to undergo myogenesis may contribute to skeletal muscle disorders such as atrophy, cachexia, and sarcopenia. Myogenic regulatory factors (MRF) are transcription factors that regulate myogenesis and determines whether SCs will be in the quiescent, activated, committed, or differentiated state. Mitochondria oxidative phosphorylation and oxidative stress play a role in the determination of the fate of SCs. The potential activation and function of SCs are also affected by inflammation during skeletal muscle regeneration. Omega-3 polyunsaturated fatty acids (PUFAs) show promise to reduce inflammation, maintain muscle mass during aging, and increase the functional capacity of the muscle. The aim of this critical review is to highlight the role of omega-3 PUFAs on the myogenic differentiation of SCs and pathways affected during the differentiation process, including mitochondrial function and inflammation from the current body of literature.

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Current Strategies for the Regeneration of Skeletal Muscle Tissue

International Journal of Molecular Sciences ◽

10.3390/ijms22115929 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5929

Author(s):

Emine Alarcin ◽

Ayca Bal-Öztürk ◽

Hüseyin Avci ◽

Hamed Ghorbanpoor ◽

Fatma Dogan Guzel ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Tissue ◽

Muscle Regeneration ◽

Striated Muscle ◽

Cell Types ◽

Skeletal Muscle Tissue ◽

Skeletal Muscle Regeneration ◽

Muscle Repair ◽

Clinical Implementation ◽

Different Cell Types

Traumatic injuries, tumor resections, and degenerative diseases can damage skeletal muscle and lead to functional impairment and severe disability. Skeletal muscle regeneration is a complex process that depends on various cell types, signaling molecules, architectural cues, and physicochemical properties to be successful. To promote muscle repair and regeneration, various strategies for skeletal muscle tissue engineering have been developed in the last decades. However, there is still a high demand for the development of new methods and materials that promote skeletal muscle repair and functional regeneration to bring approaches closer to therapies in the clinic that structurally and functionally repair muscle. The combination of stem cells, biomaterials, and biomolecules is used to induce skeletal muscle regeneration. In this review, we provide an overview of different cell types used to treat skeletal muscle injury, highlight current strategies in biomaterial-based approaches, the importance of topography for the successful creation of functional striated muscle fibers, and discuss novel methods for muscle regeneration and challenges for their future clinical implementation.

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The COX-2 pathway is essential during early stages of skeletal muscle regeneration

AJP Cell Physiology ◽

10.1152/ajpcell.00088.2004 ◽

2004 ◽

Vol 287 (2) ◽

pp. C475-C483 ◽

Cited By ~ 189

Author(s):

Brenda A. Bondesen ◽

Stephen T. Mills ◽

Kristy M. Kegley ◽

Grace K. Pavlath

Keyword(s):

Skeletal Muscle ◽

Muscle Regeneration ◽

Inflammatory Cells ◽

Skeletal Muscle Regeneration ◽

Cellular Processes ◽

Early Stages ◽

Inflammatory Drugs ◽

Cox 2 ◽

Anti Inflammatory

Skeletal muscle regeneration comprises several overlapping cellular processes, including inflammation and myogenesis. Prostaglandins (PGs) may regulate muscle regeneration, because they modulate inflammation and are involved in various stages of myogenesis in vitro. PG synthesis is catalyzed by different isoforms of cyclooxygenase (COX), which are inhibited by nonsteroidal anti-inflammatory drugs. Although experiments employing nonsteroidal anti-inflammatory drugs have implicated PGs in tissue repair, how PGs regulate muscle regeneration remains unclear, and the potentially distinct roles of different COX isoforms have not been investigated. To address these questions, a localized freeze injury was induced in the tibialis anterior muscles of mice chronically treated with either a COX-1- or COX-2-selective inhibitor (SC-560 and SC-236, respectively), starting before injury. The size of regenerating myofibers was analyzed at time points up to 5 wk after injury and found to be decreased by SC-236 and in COX-2−/− muscles, but unaffected by SC-560. In contrast, SC-236 had no effect on myofiber growth when administered starting 7 days after injury. The attenuation of myofiber growth by SC-236 treatment and in COX-2−/− muscles is associated with decreases in the number of myoblasts and intramuscular inflammatory cells at early times after injury. Together, these data suggest that COX-2-dependent PG synthesis is required during early stages of muscle regeneration and thus raise caution about the use of COX-2-selective inhibitors in patients with muscle injury or disease.

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Fibro-adipogenic progenitors in skeletal muscle homeostasis, regeneration and diseases

Open Biology ◽

10.1098/rsob.210110 ◽

2021 ◽

Vol 11 (12) ◽

Author(s):

Thomas Molina ◽

Paul Fabre ◽

Nicolas A. Dumont

Keyword(s):

Skeletal Muscle ◽

Stem Cells ◽

Muscle Regeneration ◽

New Technologies ◽

Cell Activity ◽

Cellular Heterogeneity ◽

Skeletal Muscle Regeneration ◽

Acute Injury ◽

Muscle Stem Cells ◽

Muscle Homeostasis

Skeletal muscle possesses a remarkable regenerative capacity that relies on the activity of muscle stem cells, also known as satellite cells. The presence of non-myogenic cells also plays a key role in the coordination of skeletal muscle regeneration. Particularly, fibro-adipogenic progenitors (FAPs) emerged as master regulators of muscle stem cell function and skeletal muscle regeneration. This population of muscle resident mesenchymal stromal cells has been initially characterized based on its bi-potent ability to differentiate into fibroblasts or adipocytes. New technologies such as single-cell RNAseq revealed the cellular heterogeneity of FAPs and their complex regulatory network during muscle regeneration. In acute injury, FAPs rapidly enter the cell cycle and secrete trophic factors that support the myogenic activity of muscle stem cells. Conversely, deregulation of FAP cell activity is associated with the accumulation of fibrofatty tissue in pathological conditions such as muscular dystrophies and ageing. Considering their central role in skeletal muscle pathophysiology, the regulatory mechanisms of FAPs and their cellular and molecular crosstalk with muscle stem cells are highly investigated in the field. In this review, we summarize the current knowledge on FAP cell characteristics, heterogeneity and the cellular crosstalk during skeletal muscle homeostasis and regeneration. We further describe their role in muscular disorders, as well as different therapeutic strategies targeting these cells to restore muscle regeneration.

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The Transcription Factor Nfix Requires RhoA-ROCK1 Dependent Phagocytosis to Mediate Macrophage Skewing during Skeletal Muscle Regeneration

Cells ◽

10.3390/cells9030708 ◽

2020 ◽

Vol 9 (3) ◽

pp. 708 ◽

Cited By ~ 2

Author(s):

Marielle Saclier ◽

Michela Lapi ◽

Chiara Bonfanti ◽

Giuliana Rossi ◽

Stefania Antonini ◽

...

Keyword(s):

Skeletal Muscle ◽

Transcription Factor ◽

Muscle Regeneration ◽

Tissue Repair ◽

Skeletal Muscle Regeneration ◽

Acute Injury ◽

Dead Cell ◽

Myogenic Cells ◽

Inflammatory Phenotype ◽

Anti Inflammatory

Macrophages (MPs) are immune cells which are crucial for tissue repair. In skeletal muscle regeneration, pro-inflammatory cells first infiltrate to promote myogenic cell proliferation, then they switch into an anti-inflammatory phenotype to sustain myogenic cells differentiation and myofiber formation. This phenotypical switch is induced by dead cell phagocytosis. We previously demonstrated that the transcription factor Nfix, a member of the nuclear factor I (Nfi) family, plays a pivotal role during muscle development, regeneration and in the progression of muscular dystrophies. Here, we show that Nfix is mainly expressed by anti-inflammatory macrophages. Upon acute injury, mice deleted for Nfix in myeloid line displayed a significant defect in the process of muscle regeneration. Indeed, Nfix is involved in the macrophage phenotypical switch and macrophages lacking Nfix failed to adopt an anti-inflammatory phenotype and interact with myogenic cells. Moreover, we demonstrated that phagocytosis induced by the inhibition of the RhoA-ROCK1 pathway leads to Nfix expression and, consequently, to acquisition of the anti-inflammatory phenotype. Our study identified Nfix as a link between RhoA-ROCK1-dependent phagocytosis and the MP phenotypical switch, thus establishing a new role for Nfix in macrophage biology for the resolution of inflammation and tissue repair.

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Progressive and Coordinated Mobilization of the Skeletal Muscle Niche throughout Tissue Repair Revealed by Single-Cell Proteomic Analysis

Cells ◽

10.3390/cells10040744 ◽

2021 ◽

Vol 10 (4) ◽

pp. 744

Author(s):

Matthew Borok ◽

Nathalie Didier ◽

Francesca Gattazzo ◽

Teoman Ozturk ◽

Aurelien Corneau ◽

...

Keyword(s):

Skeletal Muscle ◽

Stem Cells ◽

Stem Cell ◽

Muscle Regeneration ◽

Cell Types ◽

Skeletal Muscle Regeneration ◽

Muscle Repair ◽

Muscle Stem Cell ◽

Muscle Stem Cells ◽

Cell Lineages

Background: Skeletal muscle is one of the only mammalian tissues capable of rapid and efficient regeneration after trauma or in pathological conditions. Skeletal muscle regeneration is driven by the muscle satellite cells, the stem cell population in interaction with their niche. Upon injury, muscle fibers undergo necrosis and muscle stem cells activate, proliferate and fuse to form new myofibers. In addition to myogenic cell populations, interaction with other cell types such as inflammatory cells, mesenchymal (fibroadipogenic progenitors—FAPs, pericytes) and vascular (endothelial) lineages are important for efficient muscle repair. While the role of the distinct populations involved in skeletal muscle regeneration is well characterized, the quantitative changes in the muscle stem cell and niche during the regeneration process remain poorly characterized. Methods: We have used mass cytometry to follow the main muscle cell types (muscle stem cells, vascular, mesenchymal and immune cell lineages) during early activation and over the course of muscle regeneration at D0, D2, D5 and D7 compared with uninjured muscles. Results: Early activation induces a number of rapid changes in the proteome of multiple cell types. Following the induction of damage, we observe a drastic loss of myogenic, vascular and mesenchymal cell lineages while immune cells invade the damaged tissue to clear debris and promote muscle repair. Immune cells constitute up to 80% of the mononuclear cells 5 days post-injury. We show that muscle stem cells are quickly activated in order to form new myofibers and reconstitute the quiescent muscle stem cell pool. In addition, our study provides a quantitative analysis of the various myogenic populations during muscle repair. Conclusions: We have developed a mass cytometry panel to investigate the dynamic nature of muscle regeneration at a single-cell level. Using our panel, we have identified early changes in the proteome of stressed satellite and niche cells. We have also quantified changes in the major cell types of skeletal muscle during regeneration and analyzed myogenic transcription factor expression in satellite cells throughout this process. Our results highlight the progressive dynamic shifts in cell populations and the distinct states of muscle stem cells adopted during skeletal muscle regeneration. Our findings give a deeper understanding of the cellular and molecular aspects of muscle regeneration.

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Treg cells limit IFN-γ production to control macrophage accrual and phenotype during skeletal muscle regeneration

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1800618115 ◽

2018 ◽

Vol 115 (11) ◽

pp. E2585-E2593 ◽

Cited By ~ 37

Author(s):

Marisella Panduro ◽

Christophe Benoist ◽

Diane Mathis

Keyword(s):

Skeletal Muscle ◽

Muscle Regeneration ◽

Cell Types ◽

Treg Cells ◽

Regenerative Process ◽

Skeletal Muscle Regeneration ◽

Acute Injury ◽

Immune System Cell ◽

Ifn Γ ◽

The Impact

Skeletal muscle regeneration is a highly orchestrated process that depends on multiple immune-system cell types, notably macrophages (MFs) and Foxp3+CD4+ regulatory T (Treg) cells. This study addressed how Treg cells rein in MFs during regeneration of murine muscle after acute injury with cardiotoxin. We first delineated and characterized two subsets of MFs according to their expression of major histocompatibility complex class II (MHCII) molecules, i.e., their ability to present antigens. Then, we assessed the impact of Treg cells on these MF subsets by punctually depleting Foxp3+ cells during the regenerative process. Treg cells controlled both the accumulation and phenotype of the two types of MFs. Their absence after injury promoted IFN-γ production, primarily by NK and effector T cells, which ultimately resulted in MF dysregulation and increased inflammation and fibrosis, pointing to compromised muscle repair. Thus, we uncovered an IFN-γ–centered regulatory layer by which Treg cells keep MFs in check and dampen inflammation during regeneration of skeletal muscle.

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Single-cell analysis of the muscle stem cell hierarchy identifies heterotypic communication signals involved in skeletal muscle regeneration

10.1101/671032 ◽

2019 ◽

Cited By ~ 4

Author(s):

Andrea J. De Micheli ◽

Paula Fraczek ◽

Sharon Soueid-Baumgarten ◽

Hiranmayi Ravichandran ◽

Iwijn De Vlaminck ◽

...

Keyword(s):

Skeletal Muscle ◽

Stem Cell ◽

Single Cell ◽

Progenitor Cells ◽

Muscle Regeneration ◽

Cell Types ◽

Myogenic Cell ◽

Skeletal Muscle Regeneration ◽

Cell Populations ◽

Communication Signals

AbstractMuscle stem cells (MuSCs) are an essential adult stem cell population with the capacity to self-renew and regenerate muscle tissue. Functionally heterogeneous subpopulations of MuSCs have been identified based on their expression of myogenic regulatory factors and surface markers. However, a unified organization of muscle stem and progenitor cells and their subpopulations remains unresolved. Here, we performed temporal analysis of skeletal muscle regeneration using single-cell RNA-sequencing (scRNA-seq) of myotoxin-injured adult mouse hindlimb muscles. We generated over 34,000 single-cell transcriptomes spanning four muscle regeneration time-points and identified 15 distinct cell types, including a heterogeneous population of MuSCs and progenitor cells. Our analysis provides a hierarchical map of myogenic cell populations and identifies stage-specific regulatory programs that govern their contributions to muscle regeneration. In this transcriptomic atlas, we observed cell type-specific regenerative dynamics, exemplified by waves of transient amplification and diversification of multiple immune cell types and, subsequently, myogenic cells. Unbiased trajectory inference organized the myogenic cell populations within the atlas into a continuum, consisting of a hierarchy of quiescent MuSCs, cycling progenitors, committed myoblasts, and terminally differentiated myocytes. This myogenic trajectory matched prior understanding and also revealed that MuSC stages are defined by synchronous changes in regulatory factors, cell cycle-associated, and surface receptor gene expression. Lastly, we analyzed the transcriptomic atlas to identify over 100 candidate heterotypic communication signals between myogenic and non-myogenic cell populations, including many involving the fibroblast growth factor (FGF), Notch, and Syndecan receptor families and their associated ligands. Syndecan receptors were implicated in a large fraction of these cell communication interactions and were observed to exhibit transcriptional heterogeneity within the myogenic continuum. Using multiparameter mass cytometry (CyTOF), we confirmed that cycling MuSCs exhibit diversified Syndecan-1/2 expression, which suggests that dynamic alterations in Syndecan signaling interactions may coordinate stage-specific myogenic cell fate regulation. This scRNA-seq reference atlas provides a resolved hierarchical organization of myogenic subpopulations as a resource to investigate cell-cell interactions that regulate myogenic stem and progenitor cell fates in muscle regeneration.

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Simvastatin Impairs the Inflammatory and Repair Phases of the Postinjury Skeletal Muscle Regeneration

BioMed Research International ◽

10.1155/2018/7617312 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Iwona Otrocka-Domagała ◽

Katarzyna Paździor-Czapula ◽

Tomasz Maślanka

Keyword(s):

Skeletal Muscle ◽

Muscle Regeneration ◽

Muscle Injury ◽

Inflammatory Cells ◽

Skeletal Muscle Regeneration ◽

Regenerative Capacity ◽

Inflammatory Phase ◽

M1 Macrophage ◽

Increased Risk ◽

Repair Phase

Background. Recent clinical data have suggested that the chronic use of high-lipophilic statins impairs the regenerative capacity of skeletal muscle. Because this activity of statins is poorly understood, we aimed to investigate the effect of simvastatin (SIM) on postinjury myofibre regeneration. Methods. The porcine model was used in this study. The animals were divided into two groups: nontreated (control; n=24) and SIM-treated (40 mg/day; n=24). On the 15th day (day 0) of the experiment, a bupivacaine hydrochloride- (BPVC-) induced muscle injury was established, and the animals were sacrificed in the following days after muscle injury. The degree of regeneration was assessed based on histopathological and immunohistochemical examinations. The presence and degree of extravasation, necrosis, and inflammation in the inflammatory phase were assessed, whereas the repair phase was evaluated based on the numbers of muscle precursor cells (MPCs), myotube and young myofibres. Results. In the inflammatory phase, SIM increased the distribution and prolonged the period of extravasation, prolonged the duration of necrosis, and prolonged and enhanced the infiltration of inflammatory cells. In the repair phase, SIM delayed and prolonged the activity of MPCs, delayed myotube formation, and delayed and decreased the formation of young myofibres. Our results indicated that SIM did not improve blood vessel stabilization at the site of the injury, did not exert an anti-inflammatory effect, prolonged and enhanced the inflammatory response, and impaired MPC activity, differentiation, and fusion. Moreover, SIM appeared to reduce M1 macrophage activity, resulting in slower removal of necrotic debris and sustained necrosis. Conclusion. This study shows that SIM negatively affects the inflammatory and repair phases of the postinjury muscle regeneration. These findings are unique, strengthen the available knowledge on the side effects of SIM, and provide evidence showing that statin therapy is associated with an increased risk of impairment of the regenerative capacity of muscle.

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