Interstitial lung disease (ILD) increases morbidity and mortality in patients with
rheumatoid arthritis (RA). Although the pathogenesis of ILD associated with RA (RA-ILD+) remains poorly defined, vascular tissue is crucial in lung physiology. In this context, endothelial progenitor cells (
EPC) are involved in endothelial tissue repair. However, little is known about their implication in RA-ILD+. Accordingly, we aimed to investigate the potential role of
EPC related to endothelial damage in RA-ILD+.
EPC quantification in peripheral blood from 80 individuals (20 RA-ILD+ patients, 25 RA-ILD- patients, 21
idiopathic pulmonary fibrosis (IPF) patients, and 14 healthy controls) was performed by flow cytometry.
EPC were considered as CD34+, CD45low, CD309+ and CD133+. A significant increase in
EPC frequency in RA-ILD+ patients, as well as in RA-ILD- and IPF patients, was found when compared with controls (p < 0.001, p = 0.02 and p < 0.001, respectively). RA-ILD+ patients exhibited a higher
EPC frequency than the RA-ILD- ones (p = 0.003), but lower than IPF patients (p < 0.001). Our results suggest that
EPC increase may represent a reparative compensatory mechanism in patients with RA-ILD+. The degree of
EPC frequency may help to identify the presence of ILD in RA patients and to discriminate RA-ILD+ from IPF.