Cellular and molecular mechanisms of nasolacrimal duct obstruction: New insights into CD4+ T cell-MIF-fibroblast pathways

• The cellular landscape of nasolacrimal duct tissue from NLDO patients was delineated, with 10 major cell types noted. • The fibroblasts in nasolacrimal duct of NLDO patients were obviously activated and expressed more genes related to collagen synthesis and immunoglobulin genes, suggesting an obvious immune response and fibrosis tendency The mucosal immune response in the nasolacrimal duct epithelium at the obstructed site was significantly enhanced, accompanied by the emergence of a novel cell subset characterized by high IGHG4 expression. This subset exhibited marked upregulation of humoral immunity-related genes, suggesting its potential involvement in a robust local immune response. • The immunologic microenvironment of nasolacrimal duct obstruction in NLDO patients was characterized by significant infiltration of activated CD4 + T cells Fibroblasts can be affected by MIF secreted mainly by T/NK cells to secrete inflammation-and fibrosis-related proteins, but are not the main source of MIF. • In vitro experiments showed that CD4 + T cells and fibroblasts in NLDO nasolacrimal duct tissue promoted the process of nasolacrimal duct fibrosis through MIF. Nasolacrimal duct obstruction (NLDO) is a common ophthalmic condition characterized by epiphora and ocular discharge. Its etiology remains poorly understood, and treatment primarily relies on surgical intervention due to a lack of effective drugs. To characterize the single-cell transcriptional landscape of the nasolacrimal duct in patients with nasolacrimal duct obstruction (NLDO) and to elucidate the immunoregulatory mechanisms underlying the key fibrotic process driving disease progression. Nasolacrimal duct tissues were obtained from 4 menopausal female patients by endoscopic dacryocystorhinostomy (DCR). Samples were collected from both the obstruction and para -blocked sites (Self-control of disease progression processes). Single-cell RNA sequencing was performed on the samples, and the cell composition and cell–cell interactions were analyzed. Subsequently, body fluid and tissue samples were obtained from 13 patients for histological and in vitro functional assays. Ten major cell types were identified in 67,658 cells of the nasolacrimal duct. Intercellular communication analysis revealed the critical role of macrophage migration inhibitory factor (MIF) in the interaction between fibroblasts and immune cells. Histological analysis revealed significant inflammation and fibrosis in nasolacrimal duct obstruction. Mechanistically, CD4 + T cell-derived MIF activated fibroblasts, promoting their proliferation. Subsequently, these fibroblasts secreted pro-inflammatory cytokines and extracellular matrix, which further stimulated CD4 + T cells. This created a self-perpetuating feedback loop that exacerbated disease progression. Overall, targeting MIF to disrupt this cycle presents a novel therapeutic approach to delay the progression to complete obstruction. This study delineates the cellular transcriptomic profile of the nasolacrimal duct in NLDO patients and demonstrates that the MIF-centered immunoregulatory axis acts as a key driver of fibrotic obstruction, while plasma cells and CD8 + T cells also contribute to the immune landscape. These findings provide critical insights into the immunoregulatory mechanisms underlying NLDO and highlight MIF-related pathways as potential therapeutic targets for impeding disease progression.