Effect of molar ligation and local Porphyromonas gingivalis inoculation on alveolar bone loss in the mouse / 北京大学学报(医学版)

ABSTRACT

Objective:To compare the extent and time course of alveolar bone loss and osteoclast activation in two murine models of periodontal disease:molar ligation and Porphyromonas gingivalis (P.gingivalis) oral inoculation.Methods:A split-mouth design was applied to two groups of mice (C57BL6,6-8 weeks old,n =24 in both groups),resulting in four treatment groups:(1) Control group:unligated upper right 2nd molars receiving CMC only,(2)Ligature group:ligation of a 9-0 suture around the upper left 2nd molar,(3) P.gingivalis group:unligated upper right 2nd molar receiving P.gingivalis challenge only,(4)Ligature ± P.gingivalis group:ligation of the upper left 2nd molar in combination with oral inoculation with 109 colony-forming units(CFU) P.gingivalis.Alveolar bone loss was measured as the cementoenamel junction and alveolar bone crest (CEJ-ABC) distance.In the study,48 C57BL6 mice were designed and treated as described above,and osteoclasts were counted on histological sections following tartrate-resistant acid phosphatase (TRAP) staining and counts were normalized to alveolar bone surface distance.Then 36 C57BL6 mice were investigated,of which 30 were ligated a 940 silk ligature around the 2nd molar in the left maxillary quadrant and 6 were not ligated.After ligation for 1 week,the ligatures in 12 mice were taken off for either 1 week or 2 weeks.The CEJ-ABC distance of the 6 mice without ligation was baseline.The CEJ-ABC distances were measured and analyzed.The data were analyzed with one-way ANOVA.Results:Molar ligation induced marked alveolar bone loss after 3,6,9 and 12 weeks [(0.16 ±0.04) mm,(0.16 ±0.02) mm,(0.18 ±0.03) mm,(0.17 ±0.02) mm],vs.corresponding controls [(0.09 ± 0.03) mm,(0.10 ± 0.01) mm,(0.12 ± 0.04) mm,(0.12 ± 0.01) mm] andP.gingivalisgroup [(0.09±0.03)mm、(0.12±0.01)mm,(0.12±0.02)mm,(0.10± 0.01) mm],P ＜ 0.05.Combined treatment with molar ligation and P.gingivalis did not further increase the CEJ-ABC distance.Evidence for osteoclast activation was found one day after molar ligation,and TRAP-positive cell numbers peaked on day 3 (12 ±4 vs.control 2 ±2,P ＜0.01).After taking off ligature following ligation for 2 weeks,it showed significantly regrowth of alveolar bone compared with that before removal of the ligature on day 7 [(0.07 ±0.02) mm vs.(0.13 ± 0.01) mm,P ＜ 0.01].Conclusion:Molar ligation is a rapid and effective way to induce periodontal bone loss in mice.Osteoclast activation occurs within 24 hours of ligature placement,and the extent of bone loss well exceeds that of the P.gingivalis-induced bone loss.Removing ligature after periodontal disease might help bone regeneration by regrowth of the alveolar bone.