Effect of PEG-recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) on growth and differentiation of the HEL cell line

Background and Objective. Thrombopoietin has been established as the major regulator of megakaryocyte and platelet production. In this study we evaluated the effects of PEG-recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), a pegylated and truncated form of thrombopoietin, on the growth and differentiation of the HEL cell line. As a model system we chose the pluripotent HEL line that acquires multiple markers of the megakaryocyte/platelet phenotype following treatment with phorbol esters, and, more importantly, expresses the receptor for thrombopoietin (Mpl receptor) at its cellular surface. Design and Methods. The effect of PEG- rHuMGDF on HEL proliferation/differentiation was evaluated in a liquid culture assay. Results. Peg-rHuMGDF do not increase the proliferative capacity of HEL cell but, in parallel experiments, HEL cells showed a more mature and differentiated pattern after exposure to the cytokine. Our results show that PEG-rHuMGDF, at the optimal doses of 100-150 ng/mL, is able to induce: 1) morphological changes with the formation of cytoplasmic protrusions; 2) increased ploidy as demonstrated by cytofluorimetric analysis; 3) increased expression of megakaryocyte markers, including glycoprotein IIB-IIIa and the platelet-specific alloantigen (PI(A1)). Interpretation and Conclusion. These findings show that HEL cells represent a useful model to investigate the differentiative properties of thrombopoietin in the megakaryocyte compartment.