Single-cell RNA sequencing elucidates potential mechanisms of endothelial cells in lung region-specific repair and remodeling in combined pulmonary fibrosis and emphysema

BACKGROUND: Combined pulmonary fibrosis and emphysema (CPFE) is a severe and progressive lung disease with limited therapeutic options and poor prognosis. CPFE manifests as emphysema and fibrosis in different lung regions and is frequently associated with pulmonary hypertension. Pulmonary vascular endothelial cells may regulate these processes, but their role in CPFE remains unclear. METHODS: Single-cell RNA sequencing and multiplex immunohistochemistry were performed on upper/lower lung tissues from CPFE patients and healthy controls. Cellular heterogeneity, gene expression, and intercellular communication networks were analyzed. RESULTS: The upper lung of CPFE exhibited marked depletion and impaired function of endothelial cells, along with neutrophil accumulation and M1 macrophage-driven inflammation. Conversely, the lower lung of CPFE displayed higher proportions of ACKR1 + venous endothelial cells and enhanced angiogenesis. Endothelial cells demonstrated profibrotic signaling via THBS1-SDC4, PDGFB-PDGFRα, and JAG1-NOTCH3 signaling targeting epithelial cells, fibroblasts, and smooth muscle cells, respectively. These endothelial cells also exhibited strong interactions with macrophages through chemokines and adhesion molecules such as CCL14 and ICAM1, and expressed factors promoting M2 macrophage polarization. Multi-color staining confirmed the proximity of these endothelial cells with specific lung resident cells and immune cells, with clear spatial compartmentalization of endothelial cells with their target cell populations in the upper and lower lungs of CPFE. CONCLUSIONS: This study provides a preliminary cellular characterization of CPFE, implicating endothelial cells as potential regulators of its regional pathology through angiocrine signaling and macrophage crosstalk. The findings provide novel mechanistic insights into the histopathological heterogeneity of CPFE and highlight these pathways as therapeutic targets.