An ultrastructural study of nuclear and centriolar configurations in multinucleated giant cells

Multinucleated giant cells were examined with electron microscopy from (1) four peripheral giant cell granulomas of the jaws, (2) a central giant cell tumor of the maxilla, (3) five giant cell tumors of tendon sheath, (4) experimentally induced foreign body granulomas in rats, (5) a virus-induced sarcoma, and (6) osteoclasts from the mandibles of rats and (7) the femurs of hamsters. The purpose of the study was (1) to examine the location and arrangement of the nuclei and the centrioles of the multinuclueated cells and compare them with the osteoclast which has previously been thought to have a unique arrangement and (2) to observe whether the physical location of the centrioles and the nuclei were such that the nuclei could undergo mitosis within the cytoplasm. All of the multinucleated cells were found to have a similar arragnement of nuclear concentration areas and nucleus-free areas. A giant centrosphere containing multiple pairs of centrioles was found in the nucleus-free areas, unassociated with any particular nucleus. In the case of the foreign body giant cell and the osteoclast, this giant centrosphere was located very close to the foreign material or bone. When occasional single pairs of centrioles were found, they were located in the area of nuclear concentration, closely associated with a particular nucleus at the periphery. These findings have shown that a common centrosphere containing multiple centrioles is not an exclusive feature of the osteoclast as was previously thought. The findings suggest that a mononuclear cell containing a centriole pair fuses to the larger cell and maintains its centriole pair in close proximity to its nucleus for a short period of time, during which it may undergo mitotic activity. Eventually, the centrioles proceed to a common centrosphere whereas the nuclei aggregate in another area making further mitotic activity an unlikely possibility.