RÉSUMÉ
Objective To comparatively investigate the characteristics of bone metabolism in forelimb malformation WHBE rabbits based on the OPG/RANK/RANKL system.Methods Healthy male 2-2.5-month old WHBE rabbit ( HWR) , Healthy Japanese rabbit ( HJR) and forelimb malformation WHBE rabbit ( FMWR) were used in this study and divided into 3 groups, HWR, HJR and FMWR groups, with 10 rabbits in each group.The shape of forelimb and mean gray value observed from X-ray film were examined, and the bone tissue micro-morphology was analyzed using HE staining.Re-al-time fluorescence quantitative PCR was used to determine the expression of osteoprotegerin ( OPG) and receptor activator of NF-KB ligand ( RANKL) mRNA.The expressions of OPG, receptor activator of NF-KB ( RANK) and RANKL protein in serum and bone tissue were assayed by enzyme-linked immunoassay ( ELISA) and immunohistochemistry, respectively. Results Compared with the HWR and HJR groups, rabbits in the FMWR group appeared abnormal in toutuous forelimb and thinner bone cortex.The mean gray values of X-ray in the FMWR group were lower than that in the HWR group ( P<0.05).There were significant differences between the FMWR and healthy rabbits (HWR and HJR) in the following pa-rameters:RANKL mRNA expression and RANKL/OPG mRNA ratio in the liver(P<0.05, P<0.01), serum protein expression of RANK and RANKL and RANKL/OPG ratio (P<0.05, P<0.01), and positive index of expression of RANKL protein and RANKL/OPG ratio in the bone tissue(P<0.05, P<0.01).Furthermore, the gene expression lev-els of OPG and RANKL of HWR were significantly higher than that of HJR(P<0.05, P<0.01).Conclusions The FMWR show some abnormal symptoms in bone metabolism as well as decrease of bone quality and histological changes of bone micro-structure, due to the significant increase of RANKL/OPG ratio of FMWR.The breed differences between WHBE and Japanese rabbits in RANKL mRNA expression level may be one of factors inducing limb malformation in the WHBE rabbits.