Single-nuclei RNA-seq reveals aberrant cell populations in restrictive allograft syndrome after lung transplantation

<bold>*</bold> contributed equally <bold>Introduction:</bold> The pathogenesis of restrictive allograft syndrome (RAS), the most severe and progressive phenotype of chronic lung allograft dysfunction, remains unclear. <bold>Aim:</bold> To analyze the cellularly-resolved transcriptomic and histologic features in the human RAS lung and their relevance for the pathophysiology of RAS. <bold>Methods:</bold> Peripheral lung tissues from 15 patients undergoing lung re-transplantation and 9 control lungs were studied by snRNA-seq (10x Genomics). Findings were validated by immunofluorescent microscopy. <bold>Results:</bold> snRNA-seq data revealed IPF-associated aberrant basaloid cells, ectopic <italic>COL15A1+</italic> endothelial cells (ECs), and <italic>CTHRC1+</italic> fibrotic fibroblasts in RAS lungs. In contrast to IPF, features of bronchiolization are completely lacking. Aberrant basaloid and intermediate epithelial cell populations are characterized by therapeutically modifiable expression patterns, including integrin αvβ6, the activator of TGFβ. Histologic stainings confirmed our transcriptomic discoveries and disclosed distinctive distribution patterns with e.g., aberrant basaloid cells being localized at the edge of the fibrotic pushing border in RAS. <bold>Conclusions:</bold> RAS is characterized by uniquely distributed aberrant basaloid cells, ectopic <italic>COL15A1+</italic> ECs, and <italic>CTHRC1+</italic> fibrotic fibroblasts, populations previously found in IPF, making these cell types the prime target for therapeutic interventions. <fig><object-id>erj;64/suppl_68/OA985/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>