OBJECTIVE: To compare the bone metabolism characteristics of WHBE rabbits with forelimb deformity using OPG (osteoprotegerin)/RANK (receptor activator of NF-κB)/RANKL (receptor activator of NF-κB ligand) system.
Methods: 10 WHBE rabbits, Japanese white rabbits and WHBE rabbits with forelimb malformation were selected and divided into 3 groups, marked as HWR (healthy WHBE rabbit), HJR (healthy Japanese rabbit) and FMWR (forelimb malformation WHBE rabbit) group. The X-ray films of the forelimbs of each group were used to observe the shape of the ulna and radius of the forelimbs of each group, and the average gray value was determined; the microscopic morphology of the forelimb bone tissue was analyzed by HE staining of the bone tissue paraffin section; the fluorescence quantitative PCR method was used to detect OPG, The RANKL gene was expressed in the liver; the expression of OPG/RANK/RANKL protein in serum and bone tissue were determined by enzyme-linked immunosorbent assay and immunohistochemistry, respectively.
RESULTS: Compared with the HWR and HJR groups, the ulna and radius of the forelimbs of the rabbits in the FMWR group were abnormally curved, and the bone cortex was significantly thinner. The gray value of the X-ray films was significantly lower than that in the HWR group (P<0.05). In the FMWR group, the expression level of RANKL gene and RANKL/OPG mRNA ratio in liver (P<0.01), serum RANK, RANKL protein content and RANKL/OPG ratio (P<0.05, P<0.01), RANKL protein expression positive index in bone tissue and RANKL/OPG ratio (P<0.05, P<0.01). RANKL/OPG ratio (P<0.05, P<0.01) and other indicators were significantly higher than those in HWR group and HJR group. Compared with the HJR group, the expression levels of OPG and RANKL genes in the HWR group were significantly increased (P<0.05, P<0.01).
Conclusion: The WHBE rabbits with forelimb deformity have the phenomenon of decreased bone quality and damaged bone tissue, and the ratio of RANKL/OPG is significantly increased. Bone metabolism disorder is the main reason for the deformity of the bones. The differences in the expression level of RANKL gene between WHBE rabbits and Japanese white rabbits may be the reason for the susceptibility of WHBE rabbits to forelimb deformities.