Endomitose

Endomitose, sometimes encountered as endomitosis in some sources, refers to a variant of the cell cycle in which DNA replication occurs without completion of cell division, producing polyploid cells. The term is not uniformly used in English-language texts, where endomitosis or endoreduplication are more common. In endomitose, a cell may enter a mitotic program and duplicate its chromosomes, but cytokinesis is incomplete or blocked, resulting in a single enlarged nucleus with multiple chromosome sets, or in multinucleated cells.

Occurrence and functions vary across organisms. Endomitose is well described in megakaryocytes, the bone marrow cells responsible for producing platelets, where polyploid nuclei support high levels of cytoplasmic production for thrombopoiesis. It also occurs in placental trophoblast giant cells, certain hepatocytes, and various plants and invertebrates, often linked to growth, metabolic demand, or developmental timing.

Mechanistic distinctions can be nuanced. Endomitose is contrasted with endoreduplication, where DNA replication happens without any mitotic entry, and with classical mitosis that proceeds but fails at cytokinesis. Depending on the context, endomitose may involve partial mitotic processes with subsequent bypass of cell division, or simple rounds of chromosome duplication without a full mitotic program.

Significance and interpretation vary by tissue. Polyploid cells can exhibit increased metabolic capacity, altered gene expression, or specialized functional roles. Abnormal or dysregulated endomitose-like processes are sometimes discussed in pathology or cancer biology, but the term remains less standardized than endomitosis or endoreduplication.