Major bleeding disorders: diagnosis, classification, management and recent developments in haemophilia

Phosphatidylserine Regulation of Coagulation Proteins Factor IXa and Factor VIIIa

Blood coagulation is an intricate process, and it requires precise control of the activities of pro- and anticoagulant factors and sensitive signaling systems to monitor and respond to blood vessel insults. These requirements are fulfilled by phosphatidylserine, a relatively miniscule-sized lipid molecule amid the myriad of large coagulation proteins. This review limelight the role of platelet membrane phosphatidylserine (PS) in regulating a key enzymatic reaction of blood coagulation; conversion of factor X to factor Xa by the enzyme factor IXa and its cofactor factor VIIIa. PS is normally located on the inner leaflet of the resting platelet membrane but appears on the outer leaflet surface of the membrane surface after an injury happens. Human platelet activation leads to exposure of buried PS molecules on the surface of the platelet-derived membranes and the exposed PS binds to discrete and specific sites on factors IXa and VIIIa. PS binding to these sites allosterically regulates both factors IXa and VIIIa. The exposure of PS and its binding to factors IXa/VIIIa is a vital step during clotting. Insufficient exposure or a defective binding of PS to these clotting proteins is responsible for various hematologic diseases which are discussed in this review.

The effect of T helper (Th)/T cytotoxic (Tc) ratio on disease severity in type A hemophilia patients

BACKGROUND AND OBJECTIVES

The aim of this study was to investigate the T helper (Th) to T cytotoxic (Tc) ratio in children suffering from type A hemophilia disease and to evaluate the correlation of this ratio with disease severity.

MATERIAL AND METHOD

Two mls of EDTA anti coagulated whole blood was collected. Immunophenotyping of lymphocytes count was carried out by FACS analysis using a double CD4 and CD8 kit. The mean ± SD of absolute numbers of CD4 and CD8 lymphocytes/ml was calculated and the ratio of CD4/CD8 was evaluated by statistical method.

RESULTS

Among 80 type A hemophilia patients, 66 (82.5%) were male. The mean age was 15 ± 3.51 years. 12 (15%) of them were suffering from mild disease and 68 (85%) had sever disease. The CD4 /CD8 ratio was obtained between 0.45 and 1.44 with mean1.79 ± 0.78. The correlation between this ration and disease severity was 0.019.

CONCLUSION

The results showed that CD4/CD8 ratio has correlation with disease severity in type A hemophilia patients, however there was no association between this ratio and gender.

Phosphatidylserine positive microparticles improve hemostasis in in-vitro hemophilia A plasma models

Circulating microparticles (MPs) are procoagulant due to the surface containing phosphatidylserine (PS), which facilitates coagulation. We investigated if MPs improve hemostasis in HA plasma models. MPs isolated from pooled normal human plasma were added to severe, moderate and mild HA plasma models (0%, 2.5%, 20% FVIII). The MPs’ effect on hemostasis was evaluated by calibrated automated thrombogram (CAT) and overall hemostasis potential (OHP) assays, while fibrin structure was imaged by standard confocal, stimulated emission depletion (STED) microscopy and scanning electron microscopy (SEM). MPs partially restored thrombin generation and fibrin formation in all HA plasma models. The procoagulant effect of MPs requires PS exposure, to a less extent of contact pathway activation, but not tissue factor exposure or in vitro stimulation of MPs. MPs partially normalized the fibrin structure, and using super-resolution STED, MPs attached to fibrin were clearly resolved. In summary, our results demonstrate that PS positive MPs could improve hemostasis in HA plasma models.