Extracellular vesicles participate in the transport of cytokines and angiogenic factors in diabetic patients with ocular complications

Abstract

Introduction: Extracellular vesicles (EVs), including circulating microvesicles (MVs) or mi- croparticles (MPs) and exosomes, derived from cells or platelets are present in the peripheral blood and are important elements involved in the activation of the coagulation system, transport of macromolecules and intercellular communication. In patients with vascular complications (including diabetes), the number of EVs is significantly increased during the acute phase of the disease. However, less is known about EVs release in the chronic state of diabetes.

Objectives: To analyse the profile of inflammatory cytokines and angiogenic factors in EVs in diabetic patients with ocular and vascular complications.

Patients and methods: The study included patients with diabetes and varying degrees of ocular complications including retinopathy (n = 48) and the control group (n = 13). EV-enriched and EV-depleted fractions were obtained from platelet-poor plasma by means of the centrifugation method (16 000 g, for 90 min). In screening, the profile of cytokines with pro-angiogenic effects was preliminary assessed using the protein microarray technology for controlled diabetic patients - CD, uncontrolled diabetic patients - UD and for the control group. In all patients, concentrations of cytokines: RANTES (Regulated on Activation, Normal T-cell Expressed and secreted) and Ang-2 (angiopoietin-2) were assayed using the ELISA method. Common blood and biochemical tests were performed.

Results: In patients with diabetes, analysis of supernatant revealed significantly increased concentrations of basic fibroblast growth factor (bFGF) and soluble receptor for vascular endothelial growth factor 2 (V-EGFR2) when compared to the control group: 49 (10.5-122) vs. 24 (2-72.5) SD (p = 0.03) and 260 (195.5-351) vs. 360 (256-461.5) SD (p = 0.01). In UD patients, concentrations of RANTES, angiostatin, tumor necrosis factor-α (TNF), and tissue inhibitors of metalloproteinase 1 and 2 (TIMP1 and TIMP2) were relatively higher in the EV-enriched fraction when compared to the EV-depleted fraction. Post hoc analysis revealed significant differences between UC patients and the control group in RANTES (16.73 (14.41-18.93) vs. 14.62 (12.37-15.28) mg/ml; p = 0.0235) and Ang-2 (2.76 (2.23-4.64) ng/ml vs. 1.74 (1.54-1.93); p = 0.0316) concentrations. These analyses did not reveal any significant differences in RANTES and Ang-2 concentrations between CD patients and the control group.

Conclusions: The profiles of cytokines and angiogenic factors in EVs are significantly increased in patients with diabetes. Also, the formation of specific cytokines related to EVs is strongly influenced by disease duration and successful treatment. EVs seem to be the conveyors of upregulated cytokines and angiogenic agents in diabetic patients.

Keywords: Angiopoietin-2; Extracellular vesicles (EVs); RANTES; cytokines; diabetes; retinopathy.