Rationale: In patients with interstitial lung diseases (ILD) basal cells accumulate within areas of pathological bronchiolization and honeycomb cysts in the peripheral lung. We have previously demonstrated the disease-enriched outgrowth of alveolar basal cells and an anti-fibrotic effect of their secretome in vitro and in vivo. Here, we aimed to characterize similarities and differences between fibrotic alveolar- and airway basal cells. Methods: Alveolar- and airway-derived basal cells were cultured from peripheral lung tissue obtained via transbronchial biopsies (TBB) and from proximal airway via mucosal biopsies (MB) in the same ILD patients. The cells were cultured in an epithelial cell specific growth medium (Cnt-PR-A) and analyzed by single cell RNA sequencing (scRNA-seq), proliferation- and scratch assays, and in an air-liquid-interface (ALI). Results: Both alveolar- and airway basal cells expressed canonical basal cell markers (TP63, KRT5, KRT14, KRT17), and showed similar capacities for wound repair, proliferation and differentiation into mucociliary epithelium. Interestingly, scRNA-seq analysis revealed clear transcriptomic differences between fibrotic alveolar- and airway-derived basal cells. Conclusion: The transcriptomic differences between alveolar basal cells and airway basal cells from lung of ILD patients might be due to the different microenvironment and will be useful to understand the role, function and origin of alveolar basal cells in ILD. Supported by a project grant (310030_192536) by the Swiss National Research Foundation.

Background: Protein arginine methyl transferases (PRMT) modify protein function by transferring methyl groups to specifically arginine residues and thereby change the function of the target protein. High expression of PRMT-1 controls cell proliferation and mitochondria activity in chronic inflammatory lung diseases such as asthma. To exert its action PRMT1 needs to form a complex with PRMT4. In IPF it had been reported that the mRNA of PRMT1 is upregulated but there is no data on the protein level or on the expression of other PRMTs. Methods: PRMT expression was assessed by Western-blotting and immunochemistry in primary fibroblasts isolated from resected lungs of 11 IPF patients and controls were used as control (n=3) AMI1 was used to block PRMT action. Fibroblast proliferation was determined by manual cell counts after 72 hours after stimulation with either platelet derived growth factor (PDGF)-BB or transforming growth factor (TGF)-b. Results: Three PRMTs were significantly higher expressed by IPF cells compared to control: PRMT1, PRMT4 and PRMT5. PDGF-BB or TGF-b upregulated the expression of PRMT1 and PRMT4 in the nucleus, while PRMT5 was located in the cytosol, of both IPF and non-IPF fibroblasts. Proliferation of fibroblasts was significantly downregulated by preincubation with AMI1 in both fibroblast types, and in the presence of either PDGF-BB or TGF-b. However, the effect was less obvious in IPF derived cells. Conclusion: PRMT1, 4 and 5 are disease specifically and constitutively upregulated in IPF fibroblasts. Fibroblast proliferation is sensitive to PRMT inhibition and suggests that this pathway may present a new therapeutic target in IPF.