Endomitoz

Endomitoz, also known as endomitosis, is a form of cell cycle in which a cell undergoes DNA replication and enters a mitotic state but cytokinesis does not complete. The result is a polyploid nucleus that contains multiple complete sets of chromosomes within a single cell. Endomitosis can occur when cells initiate mitosis but fail to divide the cytoplasm, or when successive S and partial mitotic cycles occur without cytokinesis, leading to progressively increased DNA content.

In biological systems, endomitosis is most prominently observed during the development of certain blood cells and placental tissues. Megakaryocytes, the precursor cells of platelets in bone marrow, frequently undergo endomitosis to become highly polyploid, a state that supports efficient platelet production. Trophoblast giant cells in the placenta and some other specialized cell types also exhibit endomitotic cycles. In plants and some invertebrates, endomitosis-like processes can contribute to endopolyploidy, aiding tissue growth and metabolic capacity.

Mechanistically, endomitosis involves activation of the cell cycle and, at least transiently, the mitotic machinery, followed by failure of complete cytokinesis. The resulting cells show enlarged nuclei with increased DNA content; the extent of polyploidy can vary from a few extra genome copies to several dozen.

Significance and implications vary by context. Physiologically, endomitosis supports rapid cell enlargement and functional specialization, as in megakaryopoiesis. Pathologically, dysregulated endomitotic cycles can be associated with abnormal tissue growth or cancer-related polyploid giant cells. Detection is typically by cytological examination or DNA-content analysis.