Nanoscale dysregulation of collagen structure-function disrupts mechano-homeostasis and mediates pulmonary fibrosis

Abstract

Matrix stiffening with downstream activation of mechanosensitive pathways is strongly implicated in progressive fibrosis; however, pathologic changes in extracellular matrix (ECM) that initiate mechano-homeostasis dysregulation are not defined in human disease. By integrated multiscale biomechanical and biological analyses of idiopathic pulmonary fibrosis lung tissue, we identify that increased tissue stiffness is a function of dysregulated post-translational collagen cross-linking rather than any collagen concentration increase whilst at the nanometre-scale collagen fibrils are structurally and functionally abnormal with increased stiffness, reduced swelling ratio, and reduced diameter. In ex vivo and animal models of lung fibrosis, dual inhibition of lysyl oxidase-like (LOXL) 2 and LOXL3 was sufficient to normalise collagen fibrillogenesis, reduce tissue stiffness, and improve lung function in vivo. Thus, in human fibrosis, altered collagen architecture is a key determinant of abnormal ECM structure-function, and inhibition of pyridinoline cross-linking can maintain mechano-homeostasis to limit the self-sustaining effects of ECM on progressive fibrosis.

Probing ECM remodeling in idiopathic pulmonary fibrosis via second harmonic generation microscopy analysis of macro/supramolecular collagen structure

“…1), consistent with fibrotic regions. It is now known there is marked difference in crosslinking in IPF relative to normal tissues, 34 where this could affect the net chirality. There are other possible underlying ECM changes as well, e.g., increased fibronectin deposition, 35 to which SHG is not directly sensitive.…”

Engineered Biomaterial Platforms to Study Fibrosis

“…[ 3,5,6 ] Increases in collagen cross‐linking have also been shown to be responsible for initial tissue stiffening in both lung and liver fibrosis, and to drive progressive fibrosis. [ 7,8 ]…”

“…[ 45 ] Animal models of IPF have shown that collagen crosslinking (as opposed to increased collagen concentration) is a major reason for tissue stiffening and that inhibiting crosslinking limits stiffening and fibrosis‐related dysfunction. [ 8 ] Topography scans of collagen deposits in diseased tissue found that collagen fibers had smaller diameters and increased stiffness and crosslinking when compared with normal tissue.…”

“…Since lung and liver tissues stiffen prior to ECM deposition, it would be informative to have tunable materials that mimic LOX‐mediated crosslinking of collagen fibers, such that fiber diameter decreases and stiffness increases. [ 8 ] Methods to produce fibrous hydrogels on the scale of collagen fibers that could also be modified to undergo dynamic changes from wide extensible fibers to narrow rigid fibers using photochemistry would also be useful to develop.…”

Label-free and Multimodal Second Harmonic Generation Light Sheet Microscopy

“…To demonstrate the utility of the multimodal SHG-LSM for biomedical studies we carry out a study of 3D lung fibroblast spheroids, confirming clear changes in the SHG signal when collagen production is promoted. Given that structure readouts of collagen provided by SHG imaging can allow diagnostic and prognostic information in cancer 49 and can also be markers of fibrotic lung disease 50 our 3D SHG-LSM approach can be transformative both for medical research and drug screening.…”