Changes in acetylcholinesterase during poly-ploidization and maturation of megakaryocytes

Acetylcholinesterase (AChE) may help regulate rodent megakaryocytopoiesis by altering proliferation of the progenitors. If megakaryocytes (MK) participate in a negative feedback loop, then AChE levels should increase with maturity. AChE does appear to increase with size, so the assumption has been that AChE increases with maturity, since size increases with ploidy and maturity. We directly measured all of these features in the same MK. X-Y coordinates were recorded for each rat MK (N=471) via computer-controlled microscopy. Every MK was sequentially measured for both size and AChE (AChE stain), maturity (Giemsa) and ploidy (Feulgen) via image cytometry. Cellular area increased (1.1-1.9× a 4n MK) as nuclear area increased with polyploidy (4n-32n), and resulted in significantly more AChE (total 1.4-3.3×; mean 1.2-1.7× a 4n MK). Cellular area also increased as cells matured (Stage I-III) within each ploidy class (4n-32n), and this resulted in significantly more total AChE (1.5-5.1× a Stage I MK). Although area and total AChE declined slightly in the Stage IV cells, mean AChE levels continued to increase throughout all stages of maturity. Another study (N=416) focusing on the most mature cells, verified this relationship between declining areas but high levels of AChE activity. Although higher levels of AChE coincide with higher levels of polyploidy, the most significant increases in AChE expression occur during cellular maturation within all ploidy classes. Thus, this study provides further evidence that mature MK have the potential to help regulate megakaryocytopoiesis.