IN-VIVO ADMINISTRATION OF IL-1-BETA ACCELERATES SILK LIGATURE-INDUCEDALVEOLAR BONE-RESORPTION IN RATS

The effects of recombinant human interleukin-1 beta (rhIL-1 beta) on a lveolar bone resorptive activity in rats were examined. Continuous adm inistration of rhIL-1 beta or phosphate-buffered saline (PBS) was give n via osmotic pumps for 3, 7 and 14 days to rats with silk ligatures a round second maxillary molars. Other animals without ligatures receive d insertion of pumps containing rhIL-1 beta or remained untreated. Sec tions 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/macrophag e monoclonal antibody (ED 1). In addition, body weight, plasma calcium and phosphorus levels were monitored. The mean body weight of rats re ceiving rhIL-1 beta was significantly lower (P<0.05 to P<0.01) compare d with untreated rats throughout the experimental period. On Day 7, pl asma calcium and phosphorus levels were significantly lower in rats re ceiving rhIL-1 beta than in rats receiving PBS only (P<0.05). Sections revealed a moderate inflammatory cell infiltrate reaching near the al veolar crest in both groups with ligatures on Day 3. Only rats receivi ng 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 cel ls (MNGCs), coinciding with ED1-positive cells, were located on the me sial side of the septum where extensive bone resorption had occurred t hroughout the experimental period. In animals receiving rhIL-1 beta wi thout ligatures, compared with untreated rats, increased ACPase-positi ve cells were observed on the mesial side of the septum on Day 3. In a nimals receiving PBS only, a few ACPase-positive cells were observed c onfined 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 peri odontal tissue inflammation over a two-week period.