Interferon α impairs survival and function of circulating angiogenic cells in vitro: a model of failed endothelial repair in systemic lupus erythematosus

Abstract

BackgroundPatients with systemic lupus erythematosus have an increased risk of cardiovascular disease. Interferon α may impair endothelial repair mechanisms in lupus. Patients with systemic lupus erythematosus have fewer circulating angiogenic cells (CAC) and endothelial progenitor cells (EPCs). Mixed EPC and CAC populations have been shown to be sensitive to interferon α (IFNα). We aimed to investigate the effects of IFNα2b on an in-vitro model of angiogenesis and vascular repair. MethodsPeripheral blood mononuclear cells from healthy individuals were cultured on human fibronectin for 7 days. CAC phenotype was confirmed by low-density lipoprotein (LDL) uptake, lectin binding, and cell surface marker expression by RT-PCR. Cell survival in response to IFNα2b (0·01–10 ng/mL) was determined by the number of LDL-uptake-positive cells. To study CAC function, supernatant from CACs in the presence or absence of 10ng/mL IFNα2b was added to human aortic endothelial cells on Matrigel. Tubule formation was assessed at 14 h. FindingsCACs expressed markers of endothelial (CD31) and myeloid lineage (CD14, CD45), and strongly expressed the markers CD68, CD163, and CD206 suggesting an alternatively activated (M2) macrophage phenotype. IFNα2b significantly reduced the number of CACs at day 7 in a dose-dependent manner (r2= −0·769, p<0·0001). In co-culture with endothelial cells on Matrigel, CACs co-localised to the endothelial tubules but did not form tubule networks alone. CAC supernatant significantly increased tubule network density in terms of total pixel area (mean 27 781 [SE 1469] vs 36 283 [1804], p=0·0065), number of branches (340·2 [11·0] vs 510·6 [70·2], p=0·0434), junctions (162·4 [5·9 vs 241·1 [28·0], p=0·0104), and closed loops (21·8 [1·9] vs 38·3 [2·2], p=0·005). IFNα2b significantly reduced the number of closed loops (38·2 [2·2] vs 24·1 [3·5], p=0·0094). All other network parameters were reduced by IFNα2b but did not reach statistical significance. InterpretationCACs are of myeloid lineage, and CAC supernatant contains potent angiogenic factors which augment endothelial tubule networks. IFNα2b dramatically reduces the survival of CACs in vitro, resulting in reduced tubule network formation and may be a mechanism by which IFNα promotes vascular damage in systemic lupus erythematosus. FundingNorth West England Medical Research Council Fellowship Scheme in Clinical Pharmacology and Therapeutics.