Background Antiphospholipid syndrome (APS) is an acquired thombophillia characterised by recurrent thromboembolism and
pregnancy morbidity. Thrombospondin (TSP-1) is a r glycoprotein secreted by platelets upon activation with proinflammatory,
antiangiogenic and proapoptotic properties. TSP-1 activates TGF-b1 and has been shown to be involved in TH-17 response. We aimed to investigate Thrombospondin-1 in APS.
Materials and methods Plasma, serum, and total IgG were isolated from 90 patients with APS, 46 healthy controls (HC) and 26 SLE patients. Monocytes and CD4+ T-cells were isolated from 4 HC.
Human Umbilical Vein Endothelial Cells were isolated from 2 APS patients and 5 HC and cultured with plasma or total IgG from HC or APS patients. Monocytes were stimulated with total IgG and these supernatants were used to stimulate CD4+ T-cells.
Plasma and cell culture supernatant TSP-1, IL-1β, IL-17A and free active TGF-β1 levels were determined using an ELISA.
Results APS patients had higher plasma levels of TSP-1 than HCs and SLE patients (APS: mean 390 ng/ml vs HC: 144.3 vs SLE: 153.0)
Patient plasma free active TGF-β1 levels were higher and strongly correlated with TSP-1 (r=0,827). Among the APS patients those with TSP-1 levels>600 ng/ml had IL-1b and IL-17A in their plasma.
APS HUVECs and HC HUVECs cultured with APS plasma expressed higher levels of TSP-1 copmared to their controls. (APS=139.4 ng/ml vs HC=22.8 ng/ml p=0,0009). Monocytes stimulated with APS total IgG produced higher levels of IL-1b and TSP-1 compared to their controls (700pg/ml vs 50pg/ml and 500 ng/ml vs 200 ng/ml respectively). APS stimulated supernatants induced IL-17A expression from T-cells (250pg/ml) whereas the HC had no effect.
Regarding the clinical aspects of APS, there was significant difference between the patients with pregnancy morbidity alone (130.1 ng/ml) and those with miscarriages and thrombosis (403.2 ng\ml).
Conclusions Preliminary results suggest that APS patients have higher TSP-1 plasma levels which correlate with free active TGF-β1. Monocytes and HUVECs treated with APS plasma and APS IgG produce higher levels of TSP-1 and IL-1b and these supernatants induce the IL-17A expression from T-cells.
All these suggest a possible involvement of TSP-1 in thrombus formation, inflammation and inhibition of angiogenesis that needs further study.
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