Abstract Introduction/Rationale Paraseptal (PSE) and centrilobular (CLE) emphysema are the two predominant pathological subtypes of pulmonary emphysema, differing in their anatomical distribution and clinical presentation. PSE commonly occurs in the lung periphery and is often asymptomatic, occasionally associated with spontaneous pneumothorax, whereas CLE predominantly affects central acini and manifests with airflow obstruction. A subset of patients exhibits a mixed phenotype with comparable degrees of PSE and CLE. The cellular and molecular mechanisms distinguishing these subtypes remain poorly defined. We hypothesized that PSE and CLE represent distinct disease entities, each driven by unique pathophysiological mechanisms. Methods We performed GeoMx spatial transcriptomic profiling on formalin-fixed, paraffin-embedded (FFPE) lung tissue sections from 6 controls (no COPD/emphysema), 8 CLE-only, 5 PSE-only, and 4 mixed CLE/PSE patients. For each subject, multiple tissue cores were obtained, and all samples were scanned by microCT to confirm the presence and anatomical distribution of PSE or CLE lesions. As a validation cohort, we performed single-cell RNA sequencing (scRNA-seq) on lung tissue from controls, CLE-only, and mixed CLE/PSE cases to map the pulmonary cellular landscape. Results Spatial transcriptomics revealed that mixed CLE/PSE parenchyma displayed the most pronounced transcriptomic divergence from either pure subtype. Pathways related to metabolism, cellular growth, and inflammation were downregulated in mixed CLE/PSE regions, whereas immune and inflammatory pathways were strongly enriched in pure CLE. Cellular deconvolution of spatial data indicated a reduction in adaptive immune cells within mixed CLE/PSE parenchyma. scRNA-seq analysis confirmed an enrichment of macrophages in mixed CLE/PSE lungs, contrasting with higher proportions of T and B lymphocytes in pure CLE. Pseudobulk differential expression identified enhanced TGF-β signaling in alveolar type 2 (AT2) epithelial cells and increased hypoxia and apoptosis signatures in alveolar type 1 (AT1) cells in mixed CLE/PSE. Airway and club cells exhibited signatures of active metabolism, protein secretion, and DNA replication, suggestive of compensatory proliferation. Conclusion Mixed CLE/PSE emphysema represents a distinct molecular phenotype characterized by intrinsic epithelial dysfunction rather than immune-driven injury. Impaired renewal and repair of alveolar epithelial cells seem to initiate a cascade of maladaptive responses, including activation and proliferation of airway epithelial and secretory cells aimed at maintaining tissue integrity. This epithelial-driven remodelling may contribute to abnormal parenchymal regeneration and disease progression, highlighting the need to redefine emphysema not solely by anatomical patterns but by underlying cellular and molecular mechanisms that may inform targeted therapeutic strategies. This abstract is funded by: None
Zhang et al. (Fri,) studied this question.