Abstract Rationale Mucociliary disorder (MCD) plays a crucial role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Mucus plugs in COPD are associated with accelerated lung function decline, exacerbation and mortality. However, the mechanisms underlying MCDs, particularly the epithelial damage-repair, cell fate transition and initiation of airway inflammation—remain poorly understood, posing a critical barrier to the development of precision diagnostics and targeted therapies. Methods Lineage tracing combined with single-cell RNA sequencing was performed to track airway epithelium throughout COPD development in mice for 12 months. Structural and functional disorders of mucociliary clearance were dissected by immunostaining, electron microscopy and high-speed video camera. The differentiation trajectory of epithelium was illustrated by pseudotime analysis and confirmed in air-liquid culture. Epithelial-immune crosstalk was interpreted by co-culture of primary neutrophils and ciliated cells. Tracheal and bronchiolar tissue samples from COPD patients were used to confirm the key findings in mice. Results The normal life cycle of airway ciliated cells goes through a ciliary dysfunction-aging-inflammation-apoptosis transition, which was significantly accelerated under COPD conditions. Tracheal ciliated cells have a shorter life span than bronchiolar ciliated cells and were more vulnerable to CS exposure, while protected by submucous gland environment. The average half-life of tracheal ciliated cells was 6.75 months, whereas it decreased to 0.64 months post CS exposure (MPE), primarily due to apoptosis. Damage of bronchiolar ciliated cells is moderate, with an average half-life of more than 12 months, featured with ciliary assembly defect due to centriole multiplication collapse driven by aberrantly activated Notch signaling. CS exposure promotes basal-to-ciliated differentiation to regenerate dead ciliated cells, through an early start of TP73-RFX3/FOXJ1 program, giving rise to an intermediate cell state expressing markers of both basal and ciliated cells. Neutrophils are the first immune populations found in the trachea post CS exposure, right after the development of MCDs but before the development of emphysema and lung function decline. Mechanistically, CS induced the generation of CEACAM1+ inflammatory ciliated subset at 2 MPE, the first inflammatory responder in epithelium, which express chemokines recruiting neutrophils. Finally, we confirmed the existence of inflammatory ciliated subsets and dysregulated ciliary assembly pathway in COPD patients. Conclusions This study systematically illustrates the programmed injury/regeneration/cell fate transition of epithelium and their role in inflammation initiation in COPD, highlighting the spatial-temporal heterogeneity of this process in trachea and bronchiole, at single cell resolution, evoking the need for precision prevention, diagnostics, and treatment for MCDs. This abstract is funded by: Noncommunicable Chronic Diseases-National Science and Technology Major Project (2024ZD0528400); National Natural Science Foundation of China (82270001, 22HAA00617); National Key R&D Program of China (2024YFA1108900)
Wang et al. (Fri,) studied this question.