Investigation of Aged Human Lung Endothelial Cells in Idiopathic Pulmonary Fibrosis

Faulkner, Eamon Connor

Abstract

Introduction
Older age is the main risk factor for idiopathic pulmonary fibrosis (IPF). Ageing-related changes in lung blood (pulmonary and bronchial) and lymphatic vessels are implicated in IPF pathophysiology, based on reports of their altered density and increased permeability. This study tested the hypothesis that aged human lung endothelial cells (EC or endothelium) heterogeneity is altered in IPF.
Methods
Single-cell RNA sequencing (scRNAseq) datasets of “aged lung” tissues were selected, integrated and compared only from those publicly available sources which contain age-matching samples for both donors/controls and IPF patients (49 years and older; age 63 [5.6] years; mean [SD]). Findings were validated by immunohistochemistry using EC-specific markers. A humanised in vitro model of the aged human lung endothelium monolayer was created using primary human pulmonary blood vessel endothelial cells (HPBEC). The HPBEC were cultured in vitro in the presence of human serum from healthy volunteers or IPF patients (HVHS and IPFHS, respectively), followed by scRNAseq analysis.
Results
The generation of integrated single-cell maps of aged lung tissues revealed 17 subpopulations of endothelium (12 for blood and 5 for lymphatic vessels, including 9 novel), with distinct transcriptional profiles. In IPF lung, the heterogeneity of aged lung endothelium was significantly altered - both in terms of cell numbers (linked to disease-related changes in tissue composition) and differentially expressed genes (associated with fibrosis, inflammation, differentiation and vasodilation) in individual pulmonary, bronchial and lymphatic EC subpopulations. Six subpopulations of HPBEC were identified using the humanised in vitro model. No difference in cell numbers for individual subpopulations of HPBEC cultured in IPFHS when compared to HVHS were observed, whilst statistically significant alterations in one HPBEC subpopulation, termed the “de-differentiated” HPBEC, were found.
Conclusions
The presented findings reveal previously underappreciated extent of aged lung endothelium heterogeneity, suggest direct involvement of its specific subpopulations in IPF pathophysiology and uncover cellular and molecular targets which may have diagnostic, prognostic and therapeutic relevance. This study and thesis create a conceptual framework for appreciating the disease-specific heterogeneity of aged lung endothelium as a hallmark of IPF. The humanised in vitro model presents a platform for investigating the role of altered endothelial heterogeneity in IPF.

Citation

Faulkner, E. C. Investigation of Aged Human Lung Endothelial Cells in Idiopathic Pulmonary Fibrosis. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4866422

• Thesis Type: Thesis
• Deposit Date: Oct 15, 2024
• Keywords: Biomedical sciences
• Public URL: https://hull-repository.worktribe.com/output/4866422
• Additional Information: Centre for Biomedicine; Hull York Medical School; University of Hull and University of York
• Award Date: May 28, 2024