Origin of multinucleated giant cells in long-term diffusion chamber cultures.

Abstract Multinucleated giant cells (MNGCs) form spontaneously in long-term in vivo diffusion chamber cultures of murine bone marrow. Their appearance coincides with the growth of macrophages which become the predominant cells in culture after an initial phase favoring granulopoiesis. Host mice bearing diffusion chamber cultures were given regular injections of [3H]thymidine beginning prior to the development of MNGCs. The nuclei in MNGCs in these cultures were nonuniformly labeled. In any given MNGC all, none, or some of the nuclei might be labeled and the percentage of labeled nuclei was similar to the percentage labeling of the mononuclear macrophages in these cultures. These findings demonstrate that under these experimental conditions MNGCs arise primarily from cell fusion rather than nuclear division and that they are the random fusion products of both quiescent and actively dividing macrophages.