TGF-β signaling drives phenotypic and functional characteristics of human mast cells within epithelium

Mast cells (MCs) are key effector cells in the development of type 2 inflammation, such as asthma and nasal polyposis. Intraepithelial MCs are phenotypically distinct from those found within the subepithelium and preferentially expand during mucosal inflammation, yet the mechanism driving their development and their relative contribution to inflammation is not clear. We previously found that TGF-β directed the murine intraepithelial airway MC phenotype. Here, we investigate whether TGF-β has a similar effect on human MCs. Using single cell RNA-sequencing of primary nasal polyp MCs and bulk sequencing of in vitro peripheral blood-derived MCs (PB-MCs) stimulated with TGF-β, we identified a shared signature of TGF-β within human intraepithelial MCs. This included downregulation of subepithelial MC-associated granule components (NDST2, CMA1, and CTSG), differential regulation of lipid mediator biosynthetic enzymes (PTGS1, HPGDS), and upregulation of transcription factors (SKIL, FOXP1). TGF-β suppressed incorporation of the proteases chymase and cathepsin G into PB-MC granules in vitro as part of a broader intraepithelial MC phenotype, allowing direct assessment of the differential role of MC subsets during inflammation. Through this approach, we found that TGF-β modifies MC production of inflammatory mediators in response to stimulation, enhancing MC production of the lipid mediators, PGD2 and CysLTs, in response to IgE-crosslinking; selectively decreasing IL-13, TNF-α, and IL-6; and enhancing chemokine production (IL-8 and MIP-1β). Thus, we identify a central role for TGF-β signaling in driving the human intraepithelial MC phenotype and re-shaping their response to activation.

Supported by NIH (K22 AI146281, U19AI070535)