Chapter 75

Thrombopoiesis

First published: 04 March 2022

Summary

Megakaryocytes are derived from a bipotent megakaryocyte–erythroid progenitor. Transendothelial migration and proplatelet formation and release are dependent on the interaction of megakaryocytes with bone marrow endothelial cells via adhesion molecules, including vascular cell adhesion molecule-1 and integrin α 4 β 1 . Several transcription factors determined to be critical for thrombopoiesis in humans and mice likely play a similar regulatory role in other species. In humans and domestic animals, megakaryocytes are located primarily in bone marrow. Megakaryocytes undergo some degree of fragmentation in the pulmonary circulation in most mammalian species. There are four to five times more megakaryocytes in mouse bone marrow than in human bone marrow, and mouse megakaryocytes are smaller. Megakaryocyte ploidy is not consistently related to platelet mass and platelet mass is not constant across species. In dogs and cats, platelet size is inversely proportional to platelet number, whereas there is no correlation between platelet number and size in cows, goats, or ponies.

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