Thrombospondin-1 Is Elevetad in the Plasma of Patients with Antiphospholipid Syndrome and Is Correlated with Soluble Fas Ligand and Free Active TGF-B levels

Markos Patsouras¹, Marina Sikara², Athanasios G. Tzioufas² and Panayiotis Vlachoyiannopoulos², ¹PATHOPHYSIOLOGY DEPARTMENT, UNIVERSITY OF ATHENS, School of Medicine, National University of Athens, Athens, Greece, ²Pathophysiology, School of Medicine, National University of Athens, Athens, Greece

Meeting: 2014 ACR/ARHP Annual Meeting

Keywords: antiphospholipid syndrome, endothelial cells, platelets and thrombosis, SLE

Session Information

Title: Cytokines, Mediators, Cell-cell Adhesion, Cell Trafficking and Angiogenesis

Session Type: Abstract Submissions (ACR)

Background/Purpose

Antiphospholipid syndrome (APS) is an acquired thombophillia characterized by recurrent thromboembolism and pregnancy morbidity. Thrombospondin (TSP-1) is a matricellular glycoprotein with antiangiogenic and proapoptotic properties, which is secreted by platelets upon activation. It has been described to promote apoptosis through activation of caspases or induction of Fas ligand (sFasL) expression. Furthermore, TSP-1 is considered as the major activator of TGF-beta by releasing it from the Latency Acossiated Peptide. Herein, we sought to study the involvement of TSP-1 in antiphospholipid syndrome

Methods

Plasma, serum and platelets obtained from 90 patients fulfilling the diagnostic criteria of APS, 46 healthy individuals (healthy controls: HC) and 26 SLE patients, that served as disease controls were studied.
Human Umbilical Vein Endothelial Cells (HUVECs) were isolated from 2 APS patients and 3 HCs upon full term vaginal delivery by a standard protocol. HC-HUVECs were cultured in the presence of 10% plasma from HC (n=10) or APS patients (n=20) for 20 hours. Then, culture supernatants (SPN) were removed, cells were washed twice with HBS and fresh medium was added and left for two hours (hr). The 2 hr SPNs were collected and kept at -20⁰C till use. Furthermore, HUVECs from APS patients were cultured in medium supplemented or not with their own plasma. TSP-1, soluble FasL (sFasL) and active cell-free TGF-b were determined by ELISA in plasma and cell culture SPNs.

Results

APS patients had significantly higher plasma levels of TSP-1, compared to HCs and SLE patients [Mean ng/ml [intarquartile range]: 390.0 [95.90-437.7] in APS patients vs 144.3 [46.3-236.6], p<0.0001, and: 153.0 [8.2-267.2], p=0.029 in HCs and SLE patients, respectively). TSP-1 was found to strongly correlate with sFasL and active TGFβ levels (Spearman r =0.8785, p<0.0001 and r =0.827, p<0.0001 respectively). Significantly higher levels of TSP-1 were detected in culture SPNs obtained from HUVECs treated with plasma from APS patients compared to those from HCs (mean concentration: 139.4 ng/ml in APS vs 22.8 ng/ml in HCs, p=0.0009). The analysis of correlations with clinical features, revealed that lower TSP-1 levels (mean value 130.1 ng/ml) were associated with pregnancy morbidity alone, whereas higher levels (403.2 ng/ml) with thromboembolic events with or without misacarriages (p<0.05).

Conclusion

Our findings implicate TSP-1 in APS pathogenesis, and associate it with the levels of sFasL and active TGF-b in the plasma of patients. Further studies are needed to clarify the exact role of TSP-1.

Disclosure:

M. Patsouras,
None;

M. Sikara,
None;

A. G. Tzioufas,
None;

P. Vlachoyiannopoulos,
None.

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