Expression of sclerostin in alveolar bone remodeling of ovariectomized rats

To investigate the expression and distribution of sclerostin in the alveolar bone of rat in the absence of estrogen, and to provide evidence for the analysis of the histological correlation between sclerostin and alveolar bone remodeling in rats.

The experimental subjects of this study were 32 8-week-old female Wistar rats. Among them, 16 rats were ovariectomized (OVX), and 16 rats were subjected to a sham operation (Sham). These rats were sacrificed 1, 2, 3, and 4 weeks after the operation, and the mandibles were removed and embedded. The mesial and distal sections of the rat’s mandibular first molars were selected and stained with anti-tartrate phosphatase (TRAP), sclerostin immunostaining, multiple immunostainings, RANKL and TRAP double staining, and silver-plated multiple staining.

As the postoperative time in rats increased, the TRAP-positive osteoclasts counts in the OVX group in the interalveolar septum of mandibular first molar increased significantly, and statistical difference was noted between the groups (P < 0.05). The OVX 2w, 3w, and 4w groups exhibited more TRAP-positive osteoclasts compared with the Sham group at the corresponding time point, and the results were statistically different (P < 0.05). Sclerostin immunostaining revealed that the proportion of positive bone cells in the mesial side of the periodontal ligament area of mandibular first molar in the OVX group gradually decreased. Statistical differences were noted between the OVX 3w group and the OVX 4w group as well as the OVX 1w group and, the OVX 2w group (P < 0.05). In the comparison between the area near the periodontal ligament and the central area of the alveolar bone septum of the mandibular first molar in the same group, the positive expression ratio of sclerostin in the OVX 3w and OVX 4w groups in the area near the periodontal ligament was reduced compared with that in the central area of the alveolar bone septum. The results were statistically significant (P < 0.05). A larger number of osteoblasts was noted around the osteoclasts in the OVX 4w group compared with the Sham 4w group based on ALP/ TRAP /sclerostin multiple staining, whereas less sclerostin-positive osteoblasts were noted in the OVX 4w group. Sclerostin/TRAP/silver plating staining showed that the bone tubules around the sclerostin positive bone cells mostly exhibited a parallel and neat arrangement, and the bone tubules around sclerostin negative bone cells were more irregular and disorderly arranged in the OVX 4w group.

Sclerostin protein is involved in alveolar bone remodeling in estrogen-deficient rats.