THBS1 in cell-cell communication routes of human lung fibrosis and regeneration

Gaining insight into the molecular mechanisms of the development and persistence of myofibroblasts is essential for understanding the pathobiology of pulmonary fibrosis. In addition to conventional TGFβ1-driven fibroblast-to-myofibroblast transition (FMT), there is increasing evidence that other yet unknown pro-fibrotic secreted factors might be involved in FMT and myofibroblast cell death. We aim to identify novel secreted factors that drive fibrotic and apoptotic communication routes between tissue cells and (myo)fibroblasts. First, we performed a meta-analysis using existing single-cell RNA data (Lang et al. STM. 2023) taken from a human ex vivo lung fibrosis model. NicheNet analysis identified 205 ligands which promote gene expression alterations in fibroblasts upon fibrotic stimulation. Using human cytokine arrays of the supernatants from precision-cut lung slices (hPCLS) after fibrotic treatment, we could validate several ligands including Thrombospondin 1 (THBS1). THBS1 quantification by ELISA showed overexpression after fibrotic stimulation in hPCLS supernatants. Moreover, THBS1 was upregulated in IPF-patient-derived fibroblasts after TGFβ1 treatment, advocating for its potential autocrine and paracrine communication loops. Interestingly, a time-resolved scRNAseq dataset analysis revealed that THBS1 expression was decreased in the fibrotic lungs of aged mice. Then we will test THBS1 functionally via our established siRNA system in phenotypic FMT, apoptosis and organoid assays. In summary, the bioinformatic examination of scRNAseq data across various human fibrosis models identified THBS1 as a promising new mediator of cell-cell or even cell-matrix communication in lung fibrosis and regeneration.