In vivo administration of IL-1 beta accelerates silk ligature-induced alveolar bone resorption in rats.

The effects of recombinant human interleukin-1 beta (rhIL-1 beta) on alveolar bone resorptive activity in rats were examined. Continuous administration of rhIL-1 beta or phosphate-buffered saline (PBS) was given via osmotic pumps for 3, 7 and 14 days to rats with silk ligatures around second maxillary molars. Other animals without ligatures received insertion of pumps containing rhIL-1 beta or remained untreated. Sections were subject to three different stains:--hematoxylin and eosin (H-E) for histology, acid phosphatase (ACPase) activity for osteoclast detection, and immunohistochemistry using anti-rat monocyte/macrophage monoclonal antibody (ED 1). In addition, body weight, plasma calcium and phosphorus levels were monitored. The mean body weight of rats receiving rhIL-1 beta was significantly lower (P < 0.05 to P < 0.01) compared with untreated rats throughout the experimental period. On Day 7, plasma calcium and phosphorus levels were significantly lower in rats receiving rhIL-1 beta than in rats receiving PBS only (P < 0.05). Sections revealed a moderate inflammatory cell infiltrate reaching near the alveolar crest in both groups with ligatures on Day 3. Only rats receiving rhIL-1 beta exhibited enhancement of inflammatory cell invasion on Days 7 and 14. In rats receiving rhIL-1 beta with ligatures, numerous resorption lacunae containing ACPase-positive multinucleated giant cells (MNGCs), coinciding with ED1-positive cells, were located on the mesial side of the septum where extensive bone resorption had occurred throughout the experimental period. In animals receiving rhIL-1 beta without ligatures, compared with untreated rats, increased ACPase-positive cells were observed on the mesial side of the septum on Day 3. In animals receiving PBS only, a few ACPase-positive cells were observed confined to the mesial regions where slight bone resorption occurred on Days 7 and 14. These results indicate that the administration of rhIL-1 beta accelerated alveolar bone destruction in ligature-induced periodontal tissue inflammation over a two-week period.