Platelet production

Platelet production starts in the bone marrow and ends with terminal platelet formation in blood vessels of the bone marrow or lungs. Steps include the following:

(1) Hematopoietic stem cells in the bone marrow differentiate into megakaryocytes in a TPO-dependent manner.

(2 and 3) Megakaryocytes undergo endomitosis, creating nuclei with DNA content ranging from 2N to 128N. They develop a highly invaginated membrane throughout their cytoplasm, which is continuous with the external plasma membrane. This membrane serves as a reservoir for proplatelet formation.

(4) Megakaryocytes migrate to the vascular niche, where they extend proplatelets and release them into vascular sinusoids. The entire megakaryocyte is converted into preplatelets and proplatelets, and its nucleus is extruded and phagocytosed.

(5) Once in the bloodstream, proplatelets interconvert into preplatelets.