The Effect of Hematopoietic Growth Factors on Platelet Aggregability

We compared the in vitro effect of thrombopoietin (TPO) on platelet aggregation to other hematopoietic growth factors (HGFs): granulocyte colony stimulating factor (G- CSF), granulocyte macrophage colony stimulating factor (GM- CSF), interleukin-3 (IL-3), interleukin-6 (IL-6), and erythro poietin (EPO). The platelet aggregation response of the venous blood of eight volunteers with differing aggregation patterns was characterized by a platelet aggregation (PA) score that provided numerical assessment of an individual's platelet ag gregation tendency to adenosine diphosphate (ADP). The method for analysis of the data included constructing regres sion lines for each participant's PA score versus the HGF con centration (range of 0.5 nG/mL to 100 nG/mL) and calculating the regression coefficients for the slope and the Y axis inter cept. We demonstrated that the proposed method resulted in accurate assessment of the HGF effect or lack of it on the platelet aggregation response. Within the concentration range evaluated, the influence of IL-6 and G-CSF on platelet aggrega bility was insignificant and the effects of GM-CSF and IL-3 were almost undetectable. In contrast, the potentiating effect of TPO on platelet activation was dose dependent with significant enhancement for all responder types. The concentrations of TPO utilized in our in vitro experiments were in pathophysi ological range, indicating that its impact on platelet aggregation may have clinical relevance, and that monitoring platelet func tion in conjunction with TPO treatment might be advisable. Investigation of the possible synergistic effect of HGF combi nations is warranted.