# Identification of Ephrin type-B receptor 4 as a critical mediator of tissue fibrosis

## TL;DR

This study identifies EphB4 as a key driver of lung fibrosis, showing it regulates genes involved in scar tissue formation and suggests it as a potential therapeutic target.

## Contribution

Ephrin type-B receptor 4 (EphB4) is newly identified as a critical mediator of pulmonary fibrosis.

## Key findings

- EphB4 deletion or inhibition reduced fibrosis in a mouse model of pulmonary fibrosis.
- EphB4 regulates genes related to ECM, ER cargo, and protein trafficking in fibroblasts.
- Elastin is identified as a key mediator in EphB4 signaling in fibrotic conditions.

## Abstract

Pulmonary fibrosis (PF) is a pathology associated with interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF). Fibrosis promotes continual secretion of extracellular matrix (ECM), producing nonfunctional scar tissue and causing organ failure. This study investigated the tyrosine kinase receptor Ephrin type-B receptor 4 (EphB4) as a mediator of PF. To this end, we generated mice with conditional Col1a2-driven deletion of Ephb4 and used a preclinical mouse model of PF, total and single nuclei RNA (snRNA) sequencing, NanoString, previously published single-cell data, computational analysis, and functional assays of mouse and human healthy control and IPF lung fibroblasts. Col1a2-CreERT–driven Ephb4 deletion, or EphB4 inhibition via NVP-BHG712, markedly protected against bleomycin-induced PF. Total RNA-Seq of fibroblasts isolated from Ephb4-deficient fibrotic mouse lungs exhibited reduced expression of ECM, ER Cargo, and protein trafficking–related genes. NVP-BHG712 reduced expression of these identified genes in mouse lung fibroblasts under fibrotic conditions in vitro. snRNA-Seq of mouse lungs treated with NVP-BHG712 identified transcriptomic changes of ECM genes in specific fibroblast subpopulations. RNA-Seq, computational, and functional assays using mouse and human IPF fibroblasts identified elastin as a key mediator involved in EphB4 signaling. Combined, our data show that EphB4 is a crucial mediator of PF.

For the first time, the EphB4 receptor has been identified as a crucial mediator of pulmonary fibrosis that regulates genes involved in ECM organization, ER cargo concentration and protein trafficking in fibroblasts.