Effects of Cyclosporin A on the Epiphyseal Plate Growth in Rats HJ Kim, OJ Kim, YC Hoang, JH Shin, HO Park, MS Kim, EJ Lee, SH KimDental Science Research Institute, College of DentistryCyclosporin A (CsA), hydrophobic cyclic peptide composed of 11 amino acids has been currently used in immuno-suppression by its ability to inhibit cytokine release. The inhibition of cytokine release can secondarily affect on bonemetabolism, modelling and remodelling. Current concept suggests that CsA can induce osteopenia by stimulating bothbone formation and resorption. But many reports have not been coincident each other in respect of its action mechanismin vivo and in vitro. The present study was performed to clarify CsA effects on bone growth using cell proliferation assay, gene expres-sion in vitro using MC3T3 cell line. Histomorphomertical data were obtained from knee joint in vivo after 3, 7 and 14days of each CsA treatment. MC3T3-E1 cell proliferation was inhibited by the treatment of CsA 1,000 ng/ml and 1,500 ng/ml in concentrationfor 1 and 3 days. CollagenI(α)1 gene expression was decreased by the treatment in a dose dependant manner, whereasALP expression was stable in every concentration of treatment. Histomorphometrical data analysis such as length ofhypertrophied and proliferating cartilage layer, area of secondary ossification center, trabecular bone length underneaththe epiphyseal plate and finally chondroclast number and size showed that most of the measurements were decreased