Poly(I:C)-Activated Nasal Fibroblasts Promote Eosinophil Recruitment in CRSwNP.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by persistent mucosal inflammation and eosinophilic infiltration. Although epithelial and immune cells have been widely studied, the role of nasal fibroblasts in innate immune activation and eosinophil recruitment remains unclear. METHODS: Public single-cell RNA sequencing data from sinonasal tissues were analyzed to define the cellular distribution of TLR3 and inflammatory mediators. TLR3 expression was validated in patient-derived sinonasal tissues. Primary human nasal fibroblasts were stimulated with polyinosinic-polycytidylic acid (Poly(I:C)), and cytokine and chemokine expression was assessed by real-time PCR and ELISA. Signaling pathways were examined using pharmacologic inhibitors and western blotting. Eosinophil migration toward Poly(I:C)-stimulated fibroblasts was evaluated using a microfluidic chemotaxis platform. RESULTS: TLR3 and inflammatory mediators, including CCL2, IL6, CXCL8, and CCL11, were preferentially enriched in stromal cells. Fibroblast subclustering revealed expansion of activated, remodeling, and inflammatory fibroblast states in CRSwNP, accompanied by increased TLR3 and chemokine expression. Tissue TLR3 expression was increased in CRSwNP and positively correlated with Lund-Mackay CT scores. Poly(I:C) stimulation induced dose-dependent production of IL-6, CXCL8, CCL2, and CCL11 in primary nasal fibroblasts. These responses were mediated through TRIF, p38, JNK, and PI3K/AKT signaling. Functionally, Poly(I:C)-stimulated fibroblasts promoted eosinophil chemotaxis, which was attenuated by inhibition of TRIF, JNK, and PI3K signaling. CONCLUSIONS: Nasal fibroblasts function as active stromal mediators of TLR3-dependent innate immune activation in CRSwNP. Fibroblast-derived inflammatory and eosinophil-recruiting mediators may link viral-like stimulation to eosinophilic inflammation and tissue remodeling in CRSwNP.