2018 Volume 27 Issue 4 Pages 303-308
Intermittent administration of parathyroid hormone (PTH) is known to increase bone mass for the treatment of osteoporosis. The aim of this study was to evaluate the benefits of local intermittent administration of PTH for bone regeneration in rats with cranial bone defects. Cranial bone defects were induced under anesthesia using a trephine bur (diameter, 4.3 mm) in 8-week-old male Wistar rats, which were then divided into four groups for further treatment. In the PTH-3 and PTH-1 groups, animals received PTH at 14.1 μg/kg in an absorbable collagen sponge placed near the bone defect. Animals in the collagen group received saline at 0.05 ml using the same method, while control animals received only sham surgery. Following surgery, PTH-3 animals received two subcutaneous injections of PTH (14.1 μg/kg) at the experimental site, while the PTH-1, collagen, and control animals each received saline (0.05 ml). All animals were sacrificed at 21 days after surgery. The ratio of new bone mineral content to total defect volume (BMC/TV) at the experimental sites was evaluated using micro-computed tomography. Tissue sections were analyzed by hematoxylin and eosin staining and immunohistochemistry with anti-alkaline phosphatase (ALP), anti-dentin matrix protein 1 (DMP1) and anti-Osterix antibodies. The BMC/TV ratio was significantly higher in the PTH-3 and PTH-1 groups than in the collagen group. The ratio of new bone to defect area (N/D%) was significantly higher in PTH-3 animals than in controls. ALP-positivity was more widely distributed in new bone in PTH-3 animals than in the other groups, and regions of DMP1-positivity and Osterix-positivity were also more widespread in these animals. These findings suggest that local intermittent administration of PTH enhances bone regeneration in rats with cranial bone defects.
