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FACS-Isolation and Culture of Fibro-Adipogenic Progenitors and Muscle Stem Cells from Unperturbed and Injured Mouse Skeletal Muscle
Published on: June 8, 2022
Macrophage plasticity in skeletal muscle repair
Elena Rigamonti1, Paola Zordan1, Clara Sciorati1
1Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milano, Italy.
Abstract:
Macrophages are one of the first barriers of host defence against pathogens. Beyond their role in innate immunity, macrophages play increasingly defined roles in orchestrating the healing of various injured tissues. Perturbations of macrophage function and/or activation may result in impaired regeneration and fibrosis deposition as described in several chronic pathological diseases. Heterogeneity and plasticity have been demonstrated to be hallmarks of macrophages. In response to environmental cues they display a proinflammatory (M1) or an alternative anti-inflammatory (M2) phenotype. A lot of evidence demonstrated that after acute injury M1 macrophages infiltrate early to promote the clearance of necrotic debris, whereas M2 macrophages appear later to sustain tissue healing. Whether the sequential presence of two different macrophage populations results from a dynamic shift in macrophage polarization or from the recruitment of new circulating monocytes is a subject of ongoing debate. In this paper, we discuss the current available information about the role that different phenotypes of macrophages plays after injury and during the remodelling phase in different tissue types, with particular attention to the skeletal muscle.
Insights
Macrophages, crucial for host defense and tissue repair, exhibit distinct M1 and M2 phenotypes. Their sequential roles in injury healing and potential dysregulation in chronic diseases are key areas of study.
Area of Science:
- Immunology
- Regenerative Medicine
- Pathology
Background:
- Macrophages are vital immune cells involved in host defense and tissue repair.
- Macrophage heterogeneity and plasticity allow for distinct proinflammatory (M1) and anti-inflammatory (M2) phenotypes.
- Dysfunctional macrophages can lead to impaired regeneration and fibrosis in chronic diseases.
Purpose of the Study:
- To review the roles of different macrophage phenotypes in tissue injury and repair.
- To discuss the dynamic polarization versus monocyte recruitment debate in macrophage sequential infiltration.
- To highlight the specific involvement of macrophage phenotypes in skeletal muscle healing.
Main Methods:
- Literature review of existing research on macrophage roles in tissue healing.
- Analysis of studies investigating M1 and M2 macrophage functions post-injury.
- Comparative examination across different tissue types, focusing on skeletal muscle.
Main Results:
- M1 macrophages are involved in early inflammatory responses and debris clearance after injury.
- M2 macrophages are associated with later stages of tissue remodeling and healing.
- The precise mechanisms driving the sequential presence of these phenotypes remain under investigation.
Conclusions:
- Macrophage polarization dynamics are critical for effective tissue regeneration.
- Understanding macrophage roles is essential for developing therapeutic strategies for chronic diseases.
- Further research is needed to elucidate the interplay between macrophage phenotypes and tissue-specific repair processes.
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