PB1073 - Endothelial Cell-Dependent Activated Protein C Formation is Significantly Decreased in Hereditary Protein C Deficiency Regardless of Underlying Gene Variant and Residual Activity in Plasma

Tuesday, June 27, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Hannah L. McRae

PhD Student
Institute of Experimental Hematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany

Co-Author(s)

Nadine Schwarz, MS

PhD Student
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany
JM

Jens Müller

Scientific Director
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany
SE

Sebastian F. Eckert

Resident Physician
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany
Johannes Oldenburg, MD (he/him/his)

Professor, Chairman and Director
University Clinic Bonn AöR, Institute of Experimental Haematology and Transfusion Medicine, Bonn, Germany
Bonn, Nordrhein-Westfalen, Germany
SR

Sara Reda

Physician
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany
BP

Bernd Pötzsch

Professor
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany
HR

Heiko Rühl

Senior researcher
Institute of Experimental Haematology and Transfusion Medicine, University Hospital Bonn
Bonn, Nordrhein-Westfalen, Germany

Background: Protein C (PC) deficiency is a high-risk hereditary thrombophilia caused by numerous variants in the PROC gene. The endothelium is involved by promoting activated PC (APC) formation and regulating thrombin generation.

Aims: To evaluate APC formation and thrombin generation by human umbilical vein endothelial cells (HUVECs) in patients with various PROC mutations as compared to healthy controls.

Methods: HUVECs from an established cell line were cultured in 48-well plates and treated with citrated, defibrinated plasma from patients with PC deficiency not on anticoagulation (n=13) and healthy donors (n=11). Thrombin formation was initiated by the addition of 1 pM tissue factor. Generated Thrombin and APC were measured over 60 and 120 minutes, respectively, via oligonucleotide-based enzyme capture assays (OECAs). Plasma levels of PC, free protein S (PS), antithrombin (AT), and coagulation factors II, V, VII, VIII, IX, X, and XI were also measured in all samples at the time of the experiment. PC mutations were retrieved from the patients’ medical records.

Results: PS, AT, and coagulation factor levels were normal for all samples in each group. There were 11 unique, all previously published, PROC gene variants among the 13 patients. PC was decreased in all patients, two of them had borderline levels. All healthy controls had normal PC levels (Table). Thrombin generation did not differ significantly before 60 minutes, when it increased in the PC deficient patients (p=4x10-4). APC was significantly lower in patients at the 30, 40, and 120 minute timepoints (p=6x10-6, p=1x10-7, and p=0.003, respectively) (Figure).

Conclusion(s): All 13 patients had lower APC than the control group at all timepoints. This is in accordance with the increased thrombin generation in the PC group at 60 minutes and suggests that patients with PROC gene variants may have a higher risk of thrombosis regardless of PC activity levels in plasma.