A histomorphological investigation of the effect of cyclosporin on trabecular bone of the rat mandibular condyle

The effect of cyclosporin A (CSA) on the condylar trabecular bone was evalu ated by microscopy. Twenty, 5-week-old mate Sprague-Dawley rats were divide d into a treated and a control group. Animals in the treated group received CSA, 15 mg/kg body weight, by gastric feeding daily for 4 weeks; controls received the vehicle only. Five animals from each group were killed at the end of weeks 2 and 4. After histological processing, 10 tissue sections fro m the mid-part of the mandibular condyle were examined. Generally, a histop athological osteopenia was observed around the condyle after CSA treatment, especially at the end of week 4. In the control animals, the trabecular bo ne volume steadily increased from weeks 2 to 4 (from 0.46 +/- 0.07 to 0.61 +/- 0.07 mm(3)/mm(3)). However, the bone volume was significantly less in t he CSA group than in the control group at both times (0.33 +/- 0.02 vs 0.46 +/- 0.07 and 0.26 +/- 0.07 vs 0.61 +/- 0.07 mm(3)/mm(3) for CSA vs control group at the end of weeks 2 and 4, respectively). Conversely, an increased marrow volume was observed in the CSA group at both these times (0.60 +/- 0.02 vs 0.42 +/- 0.08 and 0.71 +/- 0.06 vs 0.31 +/- 0.06 mm(3)/mm(3) for CS A vs control group at the end of weeks 2 and 4, respectively). Decreases we re also observed in trabecular thickness, osteoid seam width, osteoid volum e and cortical bone width. Because trabecular bone mass, osteoid mass and c ortical bone thickness all showed a decrease after CSA at both times, an in hibitory effect of CSA on trabecular bone formation in the mandibular condy le is proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.