Imbalance between circulating endothelial cells and endothelial progenitors in idiopathic pulmonary fibrosis

Background: Fibrogenesis during idiopathic pulmonary fibrosis (IPF) is associated with abnormal vascular remodeling. Respective abundance of circulating endothelial cells (CEC) and endothelial progenitor cells (EPC) might reflect the balance between vascular injury and repair and potentially serve as a biomarker of the disease. Objectives: We postulated that CEC and all EPC subtypes might be differently modulated in IPF. We aimed at 1) assessing them in early stages of IPF and 2) searching for correlations with disease severity. Methods: 64 consecutive patients with newly diagnosed IPF and 10 healthy age-matched volunteers were studied. CEC were isolated with CD146-coated beads. CD34, CD133 and KDR antigens, characterizing EPC, were assessed through flow cytometry. EPC (early CFU-Hill and late endothelial cells forming colonies (ECFC)) were also counted using cell culture. Results: CEC numbers were significantly increased in IPF (p=0.004) whereas EPC assessed using both flow cytometry (CD34+KDR+) and cell culture were decreased vs controls (p or 40%). ECFC was the only cell type found to be correlated to DLCO (Spearman correlation test, p=0.04). Conclusion: IPF is associated with markers of vascular injury and with a global decrease in EPC. Disease severity is associated with an EPC mobilization whose mechanisms and clinical impact need to be explored.