What Is the Megakaryocyte?

Megakaryocyte is a cell in the bone marrow differentiated from hematopoietic stem cells. It is a mature cell in the normal bone marrow that can produce platelets. The nucleus is large, but the number is very small, which is very difficult to study.

Megakaryocyte

Megakaryocyte is

It is a mature cell that can produce platelets in normal bone marrow, formerly known as granular megakaryocytes. The cells are huge, and mature megakaryocytes rupture and fall off to form platelets. Each megakaryocyte can produce an average of about 2000 (200-7700) platelets.

The megakaryocyte system includes primitive megakaryocytes, naive megakaryocytes, and megakaryocytes and platelets.

(1) Primordial megakaryocyte: The cell body is large, 15-30 m in diameter, round or irregular. The nucleus is large, round, irregular, and the nuclear chromatin is thick and reticulate, arranged closely, with 2 to 3 nucleoli. Cell mass is less, uneven, irregular edges, dark blue staining, no granules, pale nucleus staining.

(2) Juvenile megakaryocytes: The cell body is significantly enlarged, with a diameter of 30-50 m, and its appearance is often irregular. Nuclei are irregular, overlapping or twisted, nuclear chromatin is coarse grained or small, closely packed, with or without nucleoli, increased cell mass, stained blue or light blue, and pale blue near the nucleus Color or light pink, with a small amount of azuramide blue particles.

(3) Megakaryocytes:

Granular megakaryocytes: The cell body is very large, with a diameter of 40 to 70 m, sometimes up to 100 m, and its morphology is irregular. The nucleus is large, irregular in shape, the nuclear chromatin is rough, densely arranged in clumps, no nucleoli, the cytoplasm is extremely rich, pink stained, blue is mixed, and the mass contains a lot of fine purple particles Clusters often form, but no platelets are formed.

Producing platelet-type megakaryocytes: The cell body is huge, with a diameter of 40 to 70 m, sometimes up to 100 m. The nucleus is irregular, highly lobular, and the nuclear chromatin is agglomerate. The cytoplasm is uniform pink, and the cytoplasm is filled with purple-red particles or platelets of various sizes. The cell membrane is unclear, mostly pseudopod-shaped, and platelets are often accumulated on the medial and lateral sides.

Nucleated megakaryocytes: After the cytoplasm of platelet-type megakaryocytes disintegrates, a large number of platelets are released, leaving only one nucleus, which is called the naked nucleus.

(4) Platelets: The cell body is very small, only 2 to 4 m in diameter, and is star-shaped, oval, comma-shaped, or irregular. The cytoplasm was stained light blue or reddish, with small purple particles at the center, but no nucleus.

Megakaryocytes

Megakaryocyte leukemia

This disease is a malignant disease caused by the massive proliferation of megakaryocytes, which is very rare. Seen at any age, the ratio of men and women is uncertain, 2/3 of the cases have a decrease in whole blood cells, and may be associated with damaged platelet membranes and functional defects. Early hepatosplenic lymphadenopathy is rare. Secondary bone marrow fibrosis is more common in this disease. Dry bone marrow aspirate, megakaryocytes and reticular fibrosis in biopsy.

The diagnosis is based on abnormally increased megakaryocytes in the bone marrow and the surrounding blood, mainly promegakaryocytes, and there are more abnormal small promegakaryocytes. The bone marrow promegakaryocytes are> 30%. Under the electron microscope, the organelles in the promegakaryocyte cytoplasm were abundant, and there were vesicular or nodular protrusions on the cell surface, while the microvilli and wrinkle-like protrusions were very few.

Platelet peroxidase (PPO) is the earliest enzyme marker that appeared in the differentiation of megakaryocytes. It has strong specificity and can be found by examining the electron microscope PPO reaction. The PPO reaction appears near the nucleus membrane and endoplasmic reticulum of megakaryocytes. Myeloperoxidase is mainly different in Golgi and cytoplasmic particles.

Platelet glycoprotein is a specific marker of the megakaryocyte-platelet system. Anti-glycoprotein Ib antibodies recognize more mature megakaryocytes. Anti-glycoprotein IIb / a antibodies can identify naive and poorly differentiated megakaryocytes. In addition, there is an abnormality of chromosome 21.

Bone marrow megakaryocyte maturation disorder

Megakaryocyte maturation disorder is often considered as a typical change in bone marrow examination of idiopathic thrombocytopenic purpura (ITP) .In clinical work, diseases such as connective tissue disease, hypersplenism, and megaloblastic anemia can also be expressed as peripheral platelets Decreased bone marrow megakaryocyte maturation. Bone marrow cells are hypoproliferative, and the degree of hyperplasia is low; leukocyte granulocytes are reduced, mainly lobulated nuclei, rod-shaped nuclei, and late myelocytes, with few mesenocytes; young red blood cells are reduced, young and late red cells are reduced Obviously, the size, staining, and morphology of mature red blood cells are normal; the ratio of granulocyte to red (> normal) reference value range, other characteristics: the number of megakaryocytes is reduced, lymphocytes are increased, and plasma cells are also increased. Peripheral blood like whole blood cells are reduced, and lymphocytes are relatively increased.