DEVELOPMENTAL-CHANGE OF MEGAKARYOCYTE MATURATION AND DNA-PLOIDY IN HUMAN FETUS

Megakaryocytes in fetal livers obtained from 30 water-balloon aborted normal fetuses of 3 to 6 months' gestation, in the bone marrow from th e same 30 fetuses, and another 9 fetuses of 7 to 8 months' gestation a nd in the normal bone marrow of adults were analyzed by immunocytochem ical staining for size and maturation stage distribution and by flow c ytometry for ploidy distribution simultaneously. In human fetuses, meg akaryocytes showed a shift during ontogenesis from smaller towards lar ger size and from less mature towards a more mature stage with advance ment of gestation. This was accompanied by a significant progressive s hift to higher ploidy. However, the proportions (78.64%) of hypoploidy (less than or equal to 8N) megakaryocytes in bone marrow of 7-8 month s' gestation fetuses was still much higher than that (33.32%) in human adults (p<0.05), with the proportion of hyperploidy (greater than or equal to 16N) megakaryocytes lower than that (67.86%) in human adults. This result indicated that megakaryocyte polyploidization may be reta rded or inhibited during development.