Contributions
Abstract: O04
Type: Oral presentation
Session Topic: Inherited and acquired coagulation disorders
Presentation during EHA Scientific Conference on Bleeding Disorders:
On Thursday, September 15, 2016 from 09:00 - 10:30
Location: Rubí + Zafir
Background
Factor XIII (FXIII), the fibrin stabilizing factor, is involved in the formation of a normal blood clot and is present both in plasma and platelets. Megakaryocytes themselves can synthetize FXIII but is still unclear whether platelet FXIII may derive from endocytosis of exogenous FXIII by megakaryocytes.
Aims
To evaluate plasma and platelets FXIII levels at different time points in a patient with severe FXIII deficiency under replacement therapy with recombinant (r)FXIII concentrates. To investigate the possible in vitro uptake of FXIII by megakaryocytes derived from the patient with severe FXIII deficiency.
Methods
Plasma levels of FXIII activity and antigen, as well as intraplatelet content, were measured before and after administration of rFXIII concentrate at different time points. Clot formation was evaluated by whole blood rotational thrombelastometry (ROTEM®) before and after replacement therapy. Synthesis and uptake of FXIII by megakaryocytes in culture were studied by immunofluorescence technique.
Results
Before administration of rFXIII concentrate, plasma FXIII activity and antigen levels were <5% and <1%, respectively. These values increased up to 106% and 77%, respectively, 2 hours after rFXIII administration. Subsequentely, a progressive reduction of both levels up to 32% and 24%, respectively, were seen at day 13 after infusion. Platelet FXIII antigen levels were <1% before replacement therapy and reached 6% within 13 days after infusion.
Coagulation profile in INTEM and EXTEM assays on blood samples collected before replacement therapy, showed a prolonged clot formation time (CFT), reduced clot stability (MCF and AUC) and early clot lysis (ML). Normalization of ROTEM® parameters was seen after administration of rFXIII concentrate.
Cultured megakaryocytes from the patient, before undergoing replacement therapy, were negative for the immunostaining with anti-FXIII antibody and became positive only after the addition of FXIII to the culture medium.
Conclusions
Administration of rFXIII concentrates in severe FXIII deficient patient’s results in restoration of FXIII plasma levels and increased intraplatelet FXIII content. Correction of clot formation and stability can be monitored by ROTEM® after rFXIII concentrates. In vitro experiments on cultured megakaryocytes from the patient revealed that these cells, which were unable to synthesize FXIII because of a genetic defect, can endocytose exogenous FXIII and possibly produced FXIII-containing platelets, as shown with the in vivo data. The role of intraplatelet FXIII still remains to be fully elucidated.
References
1. Tahlan et al, Arch Pathol Lab Med 2014; 138:278-281.
2. Adány et al, Cell Mol Life Sci 2003; 60:1049-1060.
3. Muszbek et al, Crit Rev Clin Lab Sci 1996; 33:357-421.
4. Sixma et al, Thromb Haemost 1984; 51:388-391.
5. Adány et al, Thromb Haemost 1996; 76:74-79.
6. Malara et al, Blood 2011; 117:2476-2483.
7. McDonagh et al, J Clin Invest 1969; 48:940-946.
Abstract: O04
Type: Oral presentation
Session Topic: Inherited and acquired coagulation disorders
Presentation during EHA Scientific Conference on Bleeding Disorders:
On Thursday, September 15, 2016 from 09:00 - 10:30
Location: Rubí + Zafir
Background
Factor XIII (FXIII), the fibrin stabilizing factor, is involved in the formation of a normal blood clot and is present both in plasma and platelets. Megakaryocytes themselves can synthetize FXIII but is still unclear whether platelet FXIII may derive from endocytosis of exogenous FXIII by megakaryocytes.
Aims
To evaluate plasma and platelets FXIII levels at different time points in a patient with severe FXIII deficiency under replacement therapy with recombinant (r)FXIII concentrates. To investigate the possible in vitro uptake of FXIII by megakaryocytes derived from the patient with severe FXIII deficiency.
Methods
Plasma levels of FXIII activity and antigen, as well as intraplatelet content, were measured before and after administration of rFXIII concentrate at different time points. Clot formation was evaluated by whole blood rotational thrombelastometry (ROTEM®) before and after replacement therapy. Synthesis and uptake of FXIII by megakaryocytes in culture were studied by immunofluorescence technique.
Results
Before administration of rFXIII concentrate, plasma FXIII activity and antigen levels were <5% and <1%, respectively. These values increased up to 106% and 77%, respectively, 2 hours after rFXIII administration. Subsequentely, a progressive reduction of both levels up to 32% and 24%, respectively, were seen at day 13 after infusion. Platelet FXIII antigen levels were <1% before replacement therapy and reached 6% within 13 days after infusion.
Coagulation profile in INTEM and EXTEM assays on blood samples collected before replacement therapy, showed a prolonged clot formation time (CFT), reduced clot stability (MCF and AUC) and early clot lysis (ML). Normalization of ROTEM® parameters was seen after administration of rFXIII concentrate.
Cultured megakaryocytes from the patient, before undergoing replacement therapy, were negative for the immunostaining with anti-FXIII antibody and became positive only after the addition of FXIII to the culture medium.
Conclusions
Administration of rFXIII concentrates in severe FXIII deficient patient’s results in restoration of FXIII plasma levels and increased intraplatelet FXIII content. Correction of clot formation and stability can be monitored by ROTEM® after rFXIII concentrates. In vitro experiments on cultured megakaryocytes from the patient revealed that these cells, which were unable to synthesize FXIII because of a genetic defect, can endocytose exogenous FXIII and possibly produced FXIII-containing platelets, as shown with the in vivo data. The role of intraplatelet FXIII still remains to be fully elucidated.
References
1. Tahlan et al, Arch Pathol Lab Med 2014; 138:278-281.
2. Adány et al, Cell Mol Life Sci 2003; 60:1049-1060.
3. Muszbek et al, Crit Rev Clin Lab Sci 1996; 33:357-421.
4. Sixma et al, Thromb Haemost 1984; 51:388-391.
5. Adány et al, Thromb Haemost 1996; 76:74-79.
6. Malara et al, Blood 2011; 117:2476-2483.
7. McDonagh et al, J Clin Invest 1969; 48:940-946.