Wolters, P. J. — Page 2 | Search bioRxiv

bioRxiv2019

Telomere Dysfunction Drives Chronic Lung Allograft Dysfunction Pathology

RationaleTelomere dysfunction is associated with multiple fibrotic lung processes, including chronic lung allograft dysfunction (CLAD) which is a major limitation to long-term survival following lung transplantation. Although shorter donor telomere lengths are associated with an increased risk of CLAD, it is unknown whether short telomeres are a cause or consequence of CLAD pathology.\n\nObjectiveOur objective was to test whether telomere dysfunction contributes to pathologic changes seen in CLAD.\n\nMethods and ResultsHistopathologic and molecular analysis of human CLAD lungs demonstrated shortened telomeres in lung epithelial cells quantified by teloFISH, increased numbers of surfactant protein C immunoreactive type II alveolar epithelial cells (AECs), and increased expression of senescence markers (beta-galactosidase, p16, p53 and p21) in lung epithelial cells. Telomere repeat binding factor 1 flox/flox (TRF1F/F) mice were crossed with tamoxifen inducible SCGB1a1-cre mice to generate SCGB1a1-creTRF1 F/F mice. Following 9 months of tamoxifen-induced deletion of TRF1 in club cells, mice developed mixed obstructive and restrictive lung physiology, small airway obliteration on micro-computed tomography, a 4-fold decrease in telomere length in airway epithelial cells, collagen deposition around bronchioles and adjacent lung parenchyma, increased type II AEC numbers, expression of senescence-associated beta-galactosidase in epithelial cells and decreased SCGB1a1 expression in airway epithelial cells.\n\nConclusionsThese findings demonstrate that telomere dysfunction isolated to club cells leads to airway-centric lung remodeling and fibrosis similar to that observed in patients with CLAD and suggest that lung epithelial cell telomere dysfunction may be a molecular driver of CLAD.

cell biology↗

bioRxiv2018

Single-cell RNA-seq reveals profibrotic macrophages in lung fibrosis

Myeloid cells localize to peripheral tissues in a wide range of pathologic contexts. However, appreciation of distinct myeloid subtypes has been limited by the signal averaging inherent to bulk sequencing approaches. Here we applied single-cell RNA sequencing (scRNA-seq) to map cellular heterogeneity in lung fibrosis induced by bleomycin injury in mice. We first developed a computational framework that enables unbiased, granular cell-type annotation of scRNA-seq. This approach identified a macrophage subpopulation that was specific to injured lung and notable for high expression of Cx3cr1+ and MHCII genes. We found that these macrophages, which bear a gene expression profile consistent with monocytic origin, progressively acquire alveolar macrophage identity and localize to sites of fibroblast accumulation. Probing their functional role, in vitro studies showed a trophic effect of these cells on fibroblast activation, and ablation of Cx3cr1-expressing cells suppressed fibrosis in vivo. We also found by gene set analysis and immunofluorescence that markers of these macrophages were upregulated in samples from patients with lung fibrosis compared with healthy controls. Taken together, our results uncover a specific pathologic subgroup of macrophages with markers that could enable their therapeutic targeting for fibrosis.

immunology↗