Sphingolipids in Extracellular Vesicles Released From the Skeletal Muscle Plasma Membrane Control Muscle Stem Cell...

Area of Science:

• Cell Biology
• Biochemistry
• Regenerative Medicine

Background:

• Extracellular vesicles (EVs) from skeletal muscle (SkM) cells are crucial for regulating muscle homeostasis and regeneration.
• Understanding SkM-EV release mechanisms and the impact of inflammation is vital for developing effective EV-based therapies.
• Muscle regeneration involves a complex inflammatory response that can influence EV function.

Purpose of the Study:

• To characterize large (lEVs) and small (sEVs) released from SkM cells under basal and inflammatory conditions (TNF-α).
• To evaluate the regenerative roles of SkM-EV subtypes in vivo, focusing on their bioactive sphingolipid content.
• To determine how inflammation alters SkM-EV cargo and function for improved therapeutic design.

Main Methods:

• Isolation and characterization of SkM-lEVs and sEVs using electron microscopy and lipidomic profiling.
• In vivo evaluation of EV subtypes in a cardiotoxin-induced mouse muscle injury model.
• Analysis of sphingolipid composition, particularly sphingosine-1-phosphate (S1P) subspecies, in EVs.

Main Results:

• SkM cells release both sEVs and lEVs, primarily from the plasma membrane; sEVs originate from specialized membrane folds.
• sEVs promote M1 macrophage polarization and migration, and muscle stem cell (MuSC) differentiation, accelerating repair.
• lEVs inhibit MuSC proliferation and impair the pro- to anti-inflammatory transition; TNF-α exposure alters sEV sphingolipid content and impairs regenerative functions.

Conclusions:

• The sphingolipid content of SkM-EVs, especially S1P subspecies, is critical for their regenerative function in muscle tissue.
• Distinct sEVs and lEVs exert differential effects on MuSC behavior and macrophage phenotypes.
• Modulating SkM-EV sphingolipid composition offers a potential strategy to enhance muscle regenerative capacity.