Comparison of multinucleated cells elicited in rats by particulate bone, polyethylene, or polymethylmethacrylate.

Osteoclasts, the multinucleated resorbing cells of bone, are identified by their characteristic morphology, unique cell membrane specializations, and more recently by the presence of cell surface antigens recognized by monoclonal antibodies. They are derived from mononuclear precursor cells of hematogenous origin. The precise relationship between osteoclasts and other types of tissue giant cells is unknown. This study was designed to examine factors involved in the recruitment and differentiation of multinucleated cells and to investigate the relationship between so-called foreign body giant cells and bone-resorbing osteoclasts. Particles of various materials were implanted into subcutaneous pockets in rats. Histological, histochemical, and electron microscopic evaluations were made of specimens harvested 12 days after implantation. Large, foamy multinucleated cells were evident around particles of devitalized bone, polyethylene, and polymethylmethacrylate. Bone particles showed scalloped surfaces and were partially resorbed. Those cells adjacent to the bone particles stained positive for tartrate-resistant acid phosphatase, in contrast to the multinucleated cells adjacent to the other materials. All the cell types had extensive rough endoplasmic reticulum, abundant mitochondria, cytoplasmic vacuoles and dense bodies, giant centrospheres, and areas of fusion of plasma membranes. Cells in lacunae on the surface of the bone particles showed a clear zone of attachment to the bone substrate and ruffled borders, a feature characteristic of in osso osteoclasts. Although the giant cells occasionally displayed an extensive clear zone of attachment to the polyethylene and polymethylmethacrylate particles, no ruffled borders were detected. The results of these studies show that the multinucleated cells elicited in response to different materials, although sharing many common features, do demonstrate certain features that are substrate specific.(ABSTRACT TRUNCATED AT 250 WORDS)