Atlas of Hematology

Enhanced platelet adhesion in essential thrombocythemia after in vitro activation
OBJECTIVE: Essential thrombocythemia (ET) is a chronic myeloproliferative disorder characterized by elevated platelet counts and increased risk of thrombosis. Ex vivo data suggest increased platelet reactivity in agreement with the increased thrombosis risk, while in vitro tests often detect decreased platelet activity. The present study aimed to investigate adhesion of ET-platelets in vitro, which is an aspect of platelet function that has been addressed in only a few studies on ET patients. METHODS: The study included 30 ET patients and 14 healthy controls. Platelet adhesion was measured with a static platelet adhesion assay. RESULTS: The main finding was that ET-platelets were more readily activated by adhesion-inducing stimuli in vitro than control platelets. This was particularly evident in elderly patients and when using multiple stimuli, such as surfaces of collagen or fibrinogen combined with addition of adenosine 5’-diphosphate or ristocetin. Such multiple stimuli resulted in adhesion above the control mean +2 standard deviations for approximately 50% of the patients.CONCLUSION: The results are in accordance with the concept of increased platelet activity in ET, but opposite to most other in vitro studies. We suggest that the conditions in the adhesion assay might mimic the in vivo situation regarding the presence of chronic platelet activation.

Authors: Andreas C. Eriksson, Kourosh Lotfi, Per A. Whiss

Keywords: Esansiyel trombositemi, platelet aktivasyonu, adezyon, tromboz, platelet tayini

Year: 2010
Number: 2
Referance No: 82612

Figure 1. Platelet adhesion to albumin (a), collagen (b), fibrinogen (c), and fibronectin (d) was significantly increased by ADP (1 and 10 µmol/L) for both controls and ET-platelets. A dose-response relationship was seen on all surfaces for ET-platelets, but only on albumin and fibronectin for controls. Differences in basal adhesion (solvent) between the three groups were not significant. Data are presented as mean+SD. Filled bars = Controls (n = 11 except for fibronectin where n = 10, age range: 31-63 years), open bars = Age-matched patients (n = 14, age range: 30-66 years), patterned bars = Patients ? 67 years (n = 16, age range: 67-87 years). ns = not significant, **p<0.01, ***p<0.001
Figure 2. The combination of 0.1 µmol/L adrenaline (Adr) and 10 µmol/L LPA increased platelet adhesion synergistically to albumin for both ETplatelets and controls. Data are presented as mean+SD. Filled bars = Controls (n = 11, age range: 31-63 years), open bars = Age-matched patients (n = 14, age range: 30-66 years), patterned bars = Patients ? 67 years (n = 16, age range: 67-87 years). ns = not significant, **p<0.01, ***p<0.001
Figure 3. Platelet adhesion to albumin (filled circles), collagen (triangles) and fibrinogen (squares) induced by ADP (1 and 10 µmol/L), ristocetin (Risto 1 mg/ml) or the combination of adrenaline (Adr 0.1 µmol/L) and LPA (10 µmol/L) with basal adhesion subtracted. The increase in platelet adhesion induced by the soluble platelet activators was generally higher for ET patients compared to controls (n = 12-14, age range: 31-66 years except in D where age range: 31-63 years) and there were no differences between age-matched patients (n = 14, age range: 30-66 years) and patients ? 67 years (n = 16, age range: 67-87 years). Horizontal lines represent mean values. ns = not significant, *p<0.05, **p<0.01, ***p<0.001
Figure 4. The relative proportion of all ET patients presenting with platelet adhesion to albumin (Alb), collagen (Coll) and fibrinogen (Fibrg) exceeding the mean + 2SD of the control group for different activating stimuli with basal adhesion subtracted (n = 30, age range: 30-87 years). Numerals on the x-axis represent concentrations of soluble platelet activators in µmol/L except for ristocetin where the unit of concentration is mg/ml. Adr = adrenaline, Risto = ristocetin

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