Mesenchymal Stem Cells and Their Exosomes Modulate Sebocyte Fate and Lipid-Associated Proteomic-Lipidomic Remodeling.

Sebocytes regulate skin lipid production and inflammatory homeostasis, yet how mesenchymal stem cells (MSCs) and MSCs-derived exosomes reshape sebocyte function remains unclear. This study compared the effects of indirect MSCs co-culture and MSCs-derived exosome treatment on MTS-associated metabolic activity, intracellular lipid droplet accumulation, proteomic remodeling, and lipidomic profiles in sebocytes. Human sebocytes were indirectly co-cultured with bone marrow-derived MSCs using transwell inserts or treated with MSCs-derived exosomes under proliferative or low-serum, lipid accumulation-promoting conditions. MTS-associated metabolic activity was assessed using the MTS assay, intracellular lipid droplet accumulation using Nile Red staining, proteomic remodeling using label-free LC-MS/MS, and lipidomic changes using untargeted LC-MS lipidomics. Indirect MSCs co-culture reduced MTS-associated metabolic activity, particularly under low-serum conditions, while markedly increasing intracellular lipid droplet accumulation. Proteomic analysis indicated that MSCs co-culture promoted cytoskeletal, adhesion-related, and lipid-handling remodeling. Lipidomics further revealed broad lipid-class reprogramming, characterized by increased phospholipid-associated features and reduced lysophospholipid-associated features. In contrast, MSCs-derived exosomes increased MTS-associated metabolic activity under low-serum conditions, while intracellular lipid droplet accumulation remained largely comparable to control levels. Exosome treatment induced more selective proteomic changes related to proteostasis, mitochondrial adaptation, and vesicular trafficking/signaling, with limited lipidomic alterations that did not remain significant after FDR correction. MSCs co-culture and MSCs-derived exosomes exert biologically distinct effects on sebocytes. Whole MSCs co-culture drives extensive lipid-associated remodeling, whereas isolated exosomes mainly increase MTS-associated metabolic activity and induce adaptive proteomic responses, suggesting that exosomes transmit only part of the broader MSCs paracrine influence on sebocyte biology.