Abstract
Angiogenesis plays a central role in neovascular processes. In sickle cell patients neovascularization is considered a common feature that is associated with complications such as retinopathy and cerebrovascular disease. Several studies have reported increased vascular growth factor levels such as vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in small groups of patients. Recently the angiopoietin/Tie2 system has been shown to be of major importance in vessel maturation. In order to thoroughly characterize vascular growth factor profiles in sickle cell patients we analyzed serum levels of VEGF, PlGF, Angiopoietin-1, Angiopoietin-2, Tie-2 and erythropoietin (EPO) during the asymptomatic phase as well as during painful crises in HbSS patients (n=42) and compared these to levels in HbAA controls (n=30). Also, levels were compared between patients with and without a history of acute vaso-occlusive complications the year prior to sample collection. Serum Angiopoietin-2, Tie-2 and EPO levels were significantly higher in sickle cell patients as compared to controls (p<0.01, p=0.03 and p<0.01 respectively), whereas PlGF and VEGF serum levels were similar between patients and controls (p= 0.21 and p=0.5). Only Angiopoietin-2 and EPO serum levels were significantly increased in sickle cell patients during acute vaso-occlusive crises as compared to levels in asymptomatic patients (p<0.01 and p=0.03 respectively). No differences were detected in measured parameters between patients with a history of acute vaso-occlusive complications as compared to patients without acute vaso-occlusive complications in the preceding year. Our results show a specific pattern of angiopoietins in sickle cell patients. Considering the importance of endothelial cell activation in sickle cell disease and the regulation of endothelial cell survival and blood vessel maturation by the angiopoietin/Tie-2 system, further analysis of angiogenesis in sickle cell disease is warranted.
