Megakaryocytopoiesis in Experimental Iron Deficiency Anemia

Iron deficiency anemia is associated with increased platelet production. The megakaryocytic response to both moderate and severe iron deficiency anemia has been assessed in rats maintained on a low-iron diet. In animals with moderate anemia, the proportion of immature megakaryocytes and 24-hr tritiated thymidine labeling index were increased with no change in megakaryocyte concentration, size, or mitotic index. This indicates that increased platelet production is achieved by an increased rate of influx of precursor cells into the megakaryocyte compartment with an increased rate of efflux. In severe anemia, however, not only were the labeling index and the proportion of immature cells increased, but megakaryocyte size and mitotic index were significantly increased with a marked decrease in megakaryocyte concentration. This suggests that the circulating platelet mass is maintained by an increased platelet output per megakaryocyte with higher ploidy. Thus, in chronic iron deficiency anemia, megakaryocytopoiesis changes depending on the duration and degree of iron deficiency, with a more rapid turnover at first and increased polyploidy later.