Loss of ERG in human lung endothelial cells leads to release of pro-inflammatory and pro-fibrotic factors.

: Although vascular dysfunction is a hallmark of chronic aging-associated diseases, including idiopathic pulmonary fibrosis, the role of the pulmonary vasculature to lung repair versus lung fibrosis is not fully understood. We identified the endothelial transcription factor ETS-related gene (ERG) as an orchestrator of vascular homeostasis and repair following lung injury. To evaluate whether loss of endothelial ERG influences the activation of neighboring naïve lung fibroblasts, we collected the conditioned media (CM) generated by control- and ERG-silenced human lung endothelial cells (ECs) and we applied them to normal human lung fibroblasts. We found that CM from ERG-silenced human lung ECs strongly promoted human lung fibroblast activation and enhanced the effect of the fibrogenic mediator TGF. In support of these results, analysis of CM using nanoscale liquid chromatography coupled to tandem mass spectrometry (nano LC-MS/MS) revealed increased secretion of numerous pro-inflammatory and pro-fibrogenic mediators by ERG-silenced human lung ECs in comparison to control-silenced human lung ECs.