Human Marrow Megakaryocyte Differentiation: Multiparameter Correlative Analysis Identifies Von Willebrand Factor as a Sensitive and Distinctive Marker for Early (2N and 4N) Megakaryocytes.

Human megakaryocyte differentiation and maturation were studied in fresh marrow aspirates using multiparameter flow cytometric correlative analysis. The expression of glycoprotein (GP)IIb/IIIa, GPIIIa, GPIb and CD36 correlated directly with cell size and ploidy (r ≥ 0.97) however, GPIb acquisition was relatively slow. von Willebrand factor (vWF) is robustly expressed by early (2N and 4N) megakaryocytes, enabling their complete resolution from the other marrow cells at a level superior to that achieved with GPIIb/IIIa. Expression of myeloid CD45 and IgG-FcγRII (CDw32) increased with megakaryocyte maturation and contrasted with the declining expression of HLA-DR (negative in platelets). Interleukin-6 receptor expression in megakaryocytes was higher than in other marrow cells. Using the time-of-flight technique, the diameter of the megakaryocyte population was 37±4μm (mean±1SD) compared to 14±2μm for the total marrow cells, ranging from 21±4μm for 2N cells to 56±8μm for 64N cells. Cell size directly correlated with cell DNA (r=0.98). Receptor density of GPIIb/IIIa and GPIb decreased with the transition from 2N to 4N cells, then reached maximum at 32N-cells. We conclude that the present methods are useful for studying in vivo human megakaryocytopiesis in normal and altered states. The expression of vWF is a sensitive and distinctive marker for the identification of young marrow megakaryocytes.