C98-04 Downregulation of Abca1 Impairs Regenerative Capacity of Alveolar Epithelial Type 2 Cells in COPD

Abstract Rationale Chronic obstructive pulmonary disease (COPD) is associated with impaired alveolar regenerative repair. Dysfunction of alveolar epithelial type 2 (AT2) cells, the resident progenitor cells in alveolar, is central to COPD pathogenesis. Cholesterol metabolism is critical for stem cell homeostasis, however, its role in AT2 cell dysfunction in COPD remains poorly understood. Here, we investigate whether chronic cigarette smoke (CS) injury disrupts cholesterol metabolism, specifically through downregulation of the key transporter, ATP-binding cassette transporter A1 (ABCA1), thereby impairing the regenerative potential of AT2 cells. Methods To investigate the impact of CS on AT2 cell function, we established a COPD murine model via long-term (6-month) CS exposure. We then functionally assessed AT2 cell progenitor capacity by fluorescence-activated cell sorting (FACS) sorting and 3D organoid culture to quantify colony-forming efficiency and size. To uncover the underlying mechanism, we performed organoid bulk RNA sequencing and integrated re-analysis of single-cell sequencing dataset GSE168299 for transcriptomic analysis of AT2 cells. Concurrently, we evaluated lipid accumulation in lung tissue by Oil Red O staining and validated the expression of the identified key gene, Abca1, by qPCR. Finally, we used the ABCA1 inhibitor DIDS sodium salt to conduct functional verification through pharmacological approach. Results AT2 cells from CS-exposed mice exhibited a profound regenerative defect in organoid colony-forming and growth compared to room air (RA) group. Transcriptomic profiling consistently revealed that these functionally impaired AT2 cells had significant enrichment in epithelial development and cholesterol-related processes, coupled with downregulation of the central mediator Abca1. Then, qPCR confirmed Abca1 downregulation in organoid, and Oil Red O staining demonstrated evident lipid accumulation in CS-exposed lungs. Critically, functional experiments established causality, as pharmacological inhibition of ABCA1 with DIDS recapitulated the CS-induced injury in a dose-dependent manner, significantly suppressing organoid formation and growth. Conclusion Our study revealed ABCA1-mediated disruption of cholesterol process as a key mechanism impairing AT2 cell regenerative capacity in COPD. Downregulation of ABCA1 compromises AT2 cell proliferation and self-renewal. Therefore, targeting ABCA1 function or cholesterol homeostasis represents a promising therapeutic strategy to promote lung regeneration and repair in COPD. This abstract is funded by: the National Nature Science Foundation of China (82270039, 81970035)