Expression of osteoprotegerin and receptor activator of nuclear factor kappa-B ligand in mandibular ramus osteotomy healing with administration of different doses of parathyroid hormone

Abstract

Objective: To investigate the effect of parathyroid hormone (PTH) on the bone healing of mandibular ramus osteotomy. Methods: The mandibular ramus osteotomy model was established in sixty rabbits and these rabbits were randomly divided into experimental group A, experimental group B and control group. In the experimental group A and experimental group B, the rabbits were given PTH (20 and 40 μg/kg respectively) every other day after operation. In the control group, 1 ml saline was given. The animals were sacrificed at 1 week, 2 weeks, 3 weeks and 4 weeks postoperatively. The new bone formation was observed by histology and cone bone CT. The expression of osteoprotegerin and receptor activator of nuclear factor kappa-B (RANKL) in the new bone was detected by real-time quantitative PCR. Results: The experimental groups has better osteogenesis and the bone mineral density than the control group in osteotomy area. The experimental group B showed the best osteogenesis.Osteoprotegerin mRNA expression in experimental group A (1.127±0.035, 1.742±0.049, 1.049±0.062, 1.063±0.036) was significantly higher than that in the control group in each period (0.965±0.082, 1.254±0.071, 0.793±0.061, 0.684±0.055) (P=0.010, P=0.000, P=0.001, P=0.020), while group B (1.416±0.205, 2.648±0.168, 1.652±0.091, 1.712±0.070) was significantly higher than group A (P=0.000, P=0.010, P=0.023, P=0.003). RANKL mRNA expression in control group (1.666±0.086, 1.058±0.105, 0.885±0.124, 0.972±0.136) was significantly higher than that of the group A (0.788±0.036, 0.585±0.017, 0.692±0.017, 0.527±0.051) (P=0.001, P=0.006, P=0.003, P=0.028) in each period, while group A was significantly higher than group B(0.247±0.022, 0.240±0.034, 0.134±0.011, 0.103±0.050) (P=0.000, P=0.001, P=0.002, P=0.012). Conclusions: PTH can upregulate the expression of osteoprotegerin and reduce expression of RANKL, thus promoting new bone formation. Intermittent administration of high dose of parathyroid hormone can further promote the healing process after mandibular ramus osteotomy.