Critical role for the TGF-β1/mTORC1 signalling axis in defining the transcriptional identity of CTHRC1+ pathologic fibroblasts in idiopathic pulmonary fibrosis

Single-cell RNA sequencing of fibrotic lung tissue has identified a novel population of high collagen-producing fibroblasts not present in non-diseased control lung, characterised by high expression of the marker, collagen triple helix repeat containing 1 (CTHRC1).

The cardinal pro-fibrotic mediator TGF-β1 has been widely implicated in promoting fibrogenesis in multiple fibrotic conditions. In addition to the canonical Smad signalling pathway, TGF-β1-induced collagen I production is under critical regulatory control by the mTORC1/4E-BP1 signalling hub. Using pharmacological inhibition (dual ATP-competitive mTOR inhibitors and rapamycin) in combination with gene-editing approaches, we now demonstrate that the role of the mTORC1 axis extends to the regulation of over a third of all TGF-β1 regulated matrisome genes.