Association of giant multinucleated cells with deterioration of osteoinductive potency of bone matrix

A thirty four intramuscular implants of rat decalcified bone matrix into mice and rats were histologically inspected in order to find out if there is an inverse correlation between the induction of multinucleated giant cell formation and the bone induction activity. It was found that the presence of multinucleated giant cells which avidly resorbed the implanted matrix was almost always combined with the lack of local bone induction. In contrast, the specimens exhibiting intense bone induction were devoided of multinucleated giant cells. Our observation confirm the opinion expressed by Walters and Schneider that multinucleated giant cells induced by mineralized bone chips are not osteoclasts but a type of inflammatory cells, analogous if not identical to the "foreign body cells". It is postulated that formation of multinucleated giant cells is a morphological expression of hyperactivity of mononuclear phagocytes. Hyperactive multinucleated giant cells avidly resorb bone matrix and degrade bone inducing substance(s) like skeletal growth factor and/or bone morphogenetic peptides resulting in the deterioration or lack of bone induction.