Objective      To observe the pathological changes of rabbit periodontitis model exposed to hypoxia in high altitude and investigate the roles of receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) in the process.       Methods      Forty rabbits were randomly divided into following groups

plain experimental group

plain control group

plateau experimental group

and plateau control group (n=10). The periodontitis models were established by ligating the two central incisors of mandible and being raised by high-glucose diets. The animals of control and experimental groups were exposed to normoxia or hypoxia conditions respectively. All rabbits were sacrificed after 8 weeks. Pathological changes of periodontitis and morphology of osteoclasts were observed by HE staining

and the expression of RANKL and OPG in periodontitis tissue were tested by fluorescent light immunofluorescence assay. RANKL

OPG were semi-quantitatively analyzed by laser scanning and confocal microscopy.        Results      The RANKL gray values were 1.799±0.036

1.519±0.061 respectively in the plateau group and plain group

significantly higher than in the plateau control group and plain control group (1.242±0.078 and 0.963±0.098

P0.05). Compared to the plateau control group

OPG was lower in the plateau experimental group

but no significant difference was found between them (P0.05). RANKL expression was positively correlated with periodontal indexes

including plaque index (PLI)

bleeding index (BI)

and attachment loss (AL) in the plateau experimental group (P0.01).       Conclusion      Hypoxia environment improves the incidence and progress of periodontitis by changing the RANKL/OPG system in osteoclasts.