Metabolic control in VAT by Tregs through OSM-mediated suppression of adipogenesis

Regulatory T cells (Tregs) play diverse roles in tissue homeostasis. In visceral adipose tissue (VAT), resident Tregs, enriched with PPAR?, are clonally expanded in a IL-33 dependent manner. However, the tissue-specific functions of VAT Tregs, with unique transcriptome compared to spleen or other peripheral tissues, remain largely unknown. We identified two PPAR?+ mesenchymal stromal cells in VAT (VmSCs), named VmSC4s (PPAR?+Thy1-) and 5s (PPAR?+Thy1+). Lineage-tracing and transcriptome analysis revealled that VmSC4s contain precursors for VmSC5s. We also demonstrated that VAT Tregs directly suppress adipogenic differentation of VmSC5s through Oncostain M (OSM) to promote insulin sensitivity and glucose tolerance. Thus, VAT-Treg-derived OSM and VmSCs-displayed OSMR maintain tissue homeostasis via limiting the differentiation of dysfunctional adipocytes, which provide therapeutic targets for treating obesity and diabetes. Overall design: To determine if there is a transition between VmSC4s and 5s, the two populations were adoptive-transferred into a Kaeda recipient mice. VmSC4s and 5s before transfer, VmSC4-derived VmSC4s as well as 5s, and VmSC5-derived VmSC5s were double-sorted. To study if VAT Tregs control adipogenesis, Tregs were puctually depleted via diphtheria toxin (DT) injections into Foxp3-DTR+ and littermate Foxp3-DTR- controls. Then the floating cells from VAT were digested in QIAzol for RNA extraction. To verify whether inhibition of adipogenesis from VAT Tregs is direct, conditioned medium from VAT Tregs was incubated with VmSC5s. VmSC5s were also treated with 10ng/mL OSM to further investigate the mediators from VAT Tregs to control adipogenic differentiation.