Morphological and functional platelet abnormalities in Berkeley sickle cell mice

Abstract

Berkeley sickle cell mice are used as an animal model of human sickle cell disease but there are no reports of platelet studies in this model. Since humans with sickle cell disease have platelet abnormalities, we studied platelet morphology and function in Berkeley mice (SS). We observed elevated mean platelet forward angle light scatter (FSC) values (an indirect measure of platelet volume) in SS compared to wild type (WT) (37 ± 3.2 vs. 27 ± 1.4, mean ± SD; p <0.001), in association with moderate thrombocytopenia (505 ± 49 × 10 3 /μl vs. 1151 ± 162 × 10 3 /μl; p <0.001). Despite having marked splenomegaly, SS mice had elevated levels of Howell-Jolly bodies and "pocked" erythrocytes (p <0.001 for both) suggesting splenic dysfunction. SS mice also had elevated numbers of thiazole orange positive platelets (5 ± 1 % vs. 1 ± 1%; p <0.001), normal to low plasma thrombopoietin levels, normal plasma glycocalicin levels, normal levels of platelet recovery, and near normal platelet life spans. Platelets from SS mice bound more fibrinogen and antibody to Pselectin following activation with a threshold concentration of a protease activated receptor (PAR)-4 peptide compared to WT mice. Enlarged platelets are associated with a predisposition to arterial thrombosis in humans and some humans with SCD have been reported to have large platelets. Thus, additional studies are needed to assess whether large platelets contribute either to pulmonary hypertension or the large vessel arterial occlusion that produces stroke in some children with sickle cell disease.

Mechanisms of enhanced thrombus formation in cerebral microvessels of mice expressing hemoglobin-S

“…[7][8][9][10][11] Murine models of SCD offer the potential to better understand the pathophysiology of SCD and to identify novel therapeutic targets. 42 Studies using a variety of SCD models have revealed increased adhesive interactions between circulating erythrocytes and leukocytes with the endothelium, which can impede microvascular perfusion and promote vasoocclusive events. 1 However, it is important to recognize the limitations of the currently available SCD models, because none of them truly mimics human disease (mainly because of the complexities of SCD and the apparent contribution of multiple biologic processes to the vasculopathy associated with this disease).…”

Platelet TGF-β1 contributions to plasma TGF-β1, cardiac fibrosis, and systolic dysfunction in a mouse model of pressure overload

“…18 When thrombocytopenia was detected in a sample, it was confirmed using flow cytometry with a fluorescently labeled mAb to mouse GPIb␤ as previously described. 18 Preparation of mouse platelet lysate, platelet releasate, serum, and plasma…”

“…Whole blood platelet count was determined with an automated instrument (ADVIA120) and by flow cytometry using a fluorescently labeled mAb to mouse GPIb␤. 18 Plasma samples were prepared by immediately centrifuging the samples at 12 000g for 5 minutes at RT. No platelet contamination was observed in the plasma prepared by this method.…”

Genetic diminution of circulating prothrombin ameliorates multiorgan pathologies in sickle cell disease mice

“…15,16 Thrombocytosis and platelet activation are also well-recognized features of SCD. 4,13,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Thrombotic events including pulmonary embolism, deep vein thrombosis, and SCD-related stroke are common. 17,[36][37][38][39][40] SCD-associated pulmonary hypertension (PHT) is associated with endothelial cell activation (as measured by soluble vascular cell adhesion molecule-1 [sVCAM-1]), which would also support procoagulant activity.…”