Characterization of the Skeletal Muscle Secretome Reveals a Role for Extracellular Vesicles and IL1α/IL1β in Restricting Fibro/Adipogenic Progenitor Adipogenesis

Abstract

Repeated mechanical stress causes injuries in the adult skeletal muscle that need to be repaired. Although muscle regeneration is a highly efficient process, it fails in some pathological conditions, compromising tissue functionality. This may be caused by aberrant cell–cell communication, resulting in the deposition of fibrotic and adipose infiltrates. Here, we investigate in vivo changes in the profile of skeletal muscle secretome during the regeneration process to suggest new targetable regulatory circuits whose failure may lead to tissue degeneration in pathological conditions. We describe the kinetic variation of expression levels of 76 secreted proteins during the regeneration process. In addition, we profile the gene expression of immune cells, endothelial cells, satellite cells, and fibro-adipogenic progenitors. This analysis allowed us to annotate each cell-type with the cytokines and receptors they have the potential to synthetize, thus making it possible to draw a cell–cell interaction map. We next selected 12 cytokines whose receptors are expressed in FAPs and tested their ability to modulate FAP adipogenesis and proliferation. We observed that IL1α and IL1β potently inhibit FAP adipogenesis, while EGF and BTC notably promote FAP proliferation. In addition, we characterized the cross-talk mediated by extracellular vesicles (EVs). We first monitored the modulation of muscle EV cargo during tissue regeneration. Using a single-vesicle flow cytometry approach, we observed that EVs differentially affect the uptake of RNA and proteins into their lumen. We also investigated the EV capability to interact with SCs and FAPs and to modulate their proliferation and differentiation. We conclude that both cytokines and EVs secreted during muscle regeneration have the potential to modulate adipogenic differentiation of FAPs. The results of our approach provide a system-wide picture of mechanisms that control cell fate during the regeneration process in the muscle niche.

Hindlimb Immobilization Increases IL-1β and Cdkn2a Expression in Skeletal Muscle Fibro-Adipogenic Progenitor Cells: A Link Between Senescence and Muscle Disuse Atrophy

“…Importantly, Madaro and colleagues et al ( Madaro et al, 2018 ) detected increased IL-1β in FAPs after denervation, further suggesting that IL-1β is a component of the FAP secretome that is stimulated with disuse. Most recently, Vumbaca and colleagues showed that IL-1β played an important role in the skeletal muscle secretome ( Vumbaca et al, 2021 ). The FAP secretome includes some factors that are anabolic such as WISP1, which induces satellite cell expansion and differentiation ( Lukjanenko et al, 2019 ; Zhang et al, 2020 ), and follistatin, which induces myoblast differentiation and inhibits myostatin ( Amthor et al, 2004 ; Mozzetta et al, 2013 ).…”

Physical activity-correlated changes in plasma enzyme concentrations in fragile sarcolemmal muscular dystrophies

“…Prior studies have demonstrated that these enzymes may be released by damaged muscle [41][42][43] . The mechanism(s) by which the enzymes enter the blood may combine leakage through sarcolemma wounds, exocytosis, extracellular vesicles [44][45][46] and activity-dependent lymph flow 47,48 .…”

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

“…TNF-α, which is highly secreted by pro-inflammatory macrophages during acute injury, was shown to be the effector of FAPs apoptosis [ 54 ]. Another pro-inflammatory factor secreted by pro-inflammatory macrophages, IL-1α/β, was also shown to inhibit adipogenic differentiation of FAPs [ 64 ]. As the regeneration process progresses, there is a switch in macrophage phenotype towards anti-inflammatory macrophages, which secrete higher levels of TGF-β.…”

“…In vitro experiments showed that myoblast conditioned medium promotes FAPs proliferation. Satellite cells were shown to secrete betabellulin and epidermal growth factor (EGF), two ligands of the EGF receptor (EGFR), which stimulate FAPs proliferation in vitro [ 64 ]. Notably, contrary to myoblast conditioned medium, myotube-conditioned medium inhibits the expression of adipogenesis genes and upregulates the expression of fibrogenesis genes, suggesting that factors secreted during late stage of myogenesis could impact on the cell fate decision of FAPs and ECM remodelling [ 17 , 80 ].…”