Modeling Endothelial Dysfunction in Idiopathic Pulmonary Fibrosis: Bridging Mechanistic Insights and Translational Applications

The alveolus, the lung's primary gas exchange unit, relies on tightly coordinated interactions between the epithelial and endothelial layers. In idiopathic pulmonary fibrosis (IPF), a progressive interstitial lung disease, this architecture is profoundly disrupted. While epithelial and mesenchymal compartments have been extensively studied, the role of pulmonary microvascular endothelial cells (PMVECs) in IPF pathogenesis remains underexplored. Here, we characterize PMVEC alterations in IPF using single-cell RNA sequencing and spatial transcriptomics, identifying subtype-specific markers and demonstrating their progressive loss in fibrotic lungs. To model endothelial dysfunction, we established robust protocols for isolating and culturing primary human ECs and applied a pharmacologically relevant cytokine cocktail (IPF-RC) that mimics the IPF microenvironment. IPF-RC exposure induced hallmark features of endothelial injury, including VE-cadherin loss, increased ICAM1/VCAM1 signaling, impaired barrier integrity, and reduced wound healing and angiogenic capacity. To address the need for translational tools in drug discovery, we optimized and validated a suite of functional, scalable test systems and their endpoints using both primary and commercial endothelial cells. These mechanistic assays reliably recapitulate fibrotic endothelial injury and enable quantitative assessment of therapeutic interventions. Notably, treatment with a cAMP analog partially restored endothelial function, supporting the utility of these models for regenerative and pharmacological screening. Our findings position PMVECs as active participants in IPF progression and present novel, scalable test systems that bridge mechanistic insight with translational application. These models offer a valuable platform for identifying endothelial-targeted therapies aimed at restoring alveolar capillary integrity in fibrotic lung disease.