Multinukleation

Multinukleation is the cellular condition in which a single cell contains more than one nucleus. It can arise by two main mechanisms. One is cell fusion, where two or more mononucleate cells combine to form a single cytoplasm with multiple nuclei. The other is nuclear division without cytokinesis, a process called endomitosis or, more broadly, endoreduplication, which can produce polyploid nuclei or, in some cases, several nuclei within one cell.

In normal physiology, multinucleated cells serve important roles. Skeletal muscle fibers (myotubes) form by extensive fusion of myoblasts, resulting in large, multinucleated cells specialized for contraction. Osteoclasts, the bone-resorbing cells, arise from mononuclear precursors that fuse to create multinucleated cells with high digestive capacity. The placenta contains syncytiotrophoblasts formed by fusion of cytotrophoblasts, contributing to nutrient exchange. Megakaryocytes in the bone marrow become highly polyploid and extend cytoplasmic processes that release platelets.

Multinukleation can also occur in disease. Pathologic multinucleation often results from cell fusion induced by viral infections, producing multinucleated giant cells called syncytia (for example, in infections with certain paramyxoviruses or HIV). It can also arise from failed cytokinesis during cell division, contributing to tumor cell biology or tissue remodeling.

Diagnosis and study of multinukleation rely on microscopy to visualize nuclei and cytoplasmic sharing, sometimes complemented by techniques that assess DNA content. The functional significance of multinucleation varies by tissue and context, ranging from enabling specialized function to signaling dysregulated cell division.