Alveolar bone and subchondral bone respond differently to short-term hyperglycemia
Diabetes mellitus is a disease with high prevalence which has negative impact on the skeleton associated to decrease in bone formation with reduction in the function and number of osteoblasts. In previous studies we found that in the long term, the deleterious effects on bone manifest differently in long bones and alveolar bone. The aim of the current study was to evaluate and compare the response of alveolar bone and tibial bone in rats 7 days after induction of hyperglycemia. Materials and methods: 16 male Wistar rats, 3 months old, divided into: DG (diabetic group, n=8) and CG (sham control group, n=8). DG: one intraperitoneal injection of 60 mg/kg body weight streptozotocin, CG: equivalent volume of citrate buffer. All animals were euthanized 7 days after induced diabetes. Lower maxillary bones and tibias were processed for routine staining and immunohistochemical techniques for detecting SOST/sclerostin and Runx2. Histomorphometric evaluations: bone volume (BV/TV, %), number of Ot SOST+ (SOST+Ot N/mm2) and % Runx2 positive osteoblasts (Runx2-Ob+ N/mm2). Statistical comparison: Student’s t-test, p<0.05. Results: Seven days after induced diabetes, subchondral bone in tibias showed no change in BV/TV (DG 39.10±2.66 vs. CG 36.75±5.31), while alveolar bone showed a significant reduction (DG 42.05±1.49 vs. CG 48.11±3.86). SOST+Ot N/mm2 increased significantly in diabetic animals in alveolar bone (DG 12.28±1.68 vs. CG 6.94±0.68) but no change in tibias (trabecular bone: DG 2.33±1.43 vs. CG 3.39±1.49; cortical bone DG 5.35±1.71 vs. CG 5.45±2.83), with expression being significantly lower than that observed in alveolar bone. Runx2-Ob+ N/mm2 showed significant reduction in the experimental group in alveolar bone (DG 34.17±29.18 vs. CG 84.65±7.01) with no change observed in subchondral bone of tibias (DG 98.98±1.07 vs. CG 99.49±0.7). Conclusion: Comparison of our results shows that by 7 days, hyperglycemia may be preventing bone formation earlier in alveolar bone than in subchondral bone.