Polymorphonuclear leukocyte degranulation with exposure to polymethylmethacrylate nanoparticles.

Polymethylmethacrylate (PMMA) is clinically employed in a wide range of orthopaedic procedures. The etiology of the inflammatory reaction of recipient tissues to PMMA remains unresolved. Classically, polymorphonuclear leukocytes (PMNs) release cytoplasmic lysosomal granules when exposed to a variety of proinflammatory stimuli. Such degranulation contributes, and partially defines, the local tissue reaction to this foreign material. In the present investigation, PMMA particles (50-60 nm) were mixed with human PMNs, and the amount of lactate dehydrogenase, lysozyme, and beta-glucuronidase released from the cells was quantitated. In all cases, a dose-dependent increase in degranulation followed the addition of increasing amounts of PMMA to the PMNs. In addition, the migration of PMNs was diminished in a dose-dependent manner with exposure to increasing amounts of the cement. These results suggested that PMMA stimulates the release of leukocyte lysosomal contents and alters the migration characteristics of these cells in a manner that is consistent with the local inflammatory reaction to this cement.