Study On The Role Of OPG / RANK / RANKL In The Relationship Between Periodontitis And Vascular Calcification

Objective: This experiment is to study the expression and the possible role of OPG/RANK/RANKL system in the periodontitis compound vascular calcification rat models on the basis of successfully established animal model.Methods: 1.SPF Wistar rats were randomly assigned to four groups:control group(group C),vascular calcification group(group VDN),periodontitis group(group CP),compound group(group CP+VDN). The gingival sulcus fluid(GCF), serum, aorta and the maxillary containing second molar were taken for the following experiments. Probing depth and gingival sulcus bleeding index, maxillary biopsy containing with three molars were detected; the level of calcium, ALP and vascular tissue pathology changes were observed too. 2. Expression of OPG and RANKL in the periodontal tissue: Expression of OPG and RANKL in gingival crevicular fluid and periodontic-endodontic tissue was detected by ELISA and immunohistochemistry. 3. Expression of OPG and RANKL in vascular tissue: Detecting the expression of OPG and RANKL in vascular tissue and serum by immunohistochemistry(IHC), RT-PCR,Western-blot and ELISA.Results: 1. Animal models were successful. Histopathologic observation of periodontal tissue revealed: obvious inflammation was observed in group CP and CP+VDN.(1) PD and SBI of the CP and CP+VDN group were higher than those of the group C and VDN.(2) Group CP and CP+VDN exhibited apical migration of junctional epithelium, alveolar bone loss, which were similar to the characteristic of chronic periodontitis in humans and more severe than group C and VDN. Vascular tissue indicated:(1) The concentrations of calcium and ALP were much higher in the VDN and Compound groups compared to those of the control and CP groups(P<0.05).(2) Rat pathology of vascular tissue showed: there were no histological change in group C, the other three groups were disordered arranged of membrane elastic fibers. 2. Expression of OPG and RANKL in periodontal and pulp tissues:(1) In gingival sulcus fluid, the expression of OPG in CP or VDN group was low and RANKL was high,while OPG expression in group C and CP + VDN was low and RANKL was high. RANKL/OPG ratio in CP, VDN group was higher than that in C and CP + VDN group, and there were significant difference(P<0.05);There were no significant differences between CP+ VDN group and C group, no matter the levels of OPG and RANKL or the ratio of RANKL/OPG in GCF.(2) IHC of the periodontal tissue showed that OPG in group C was the highest, and RANKL in group CP+VDN was the highest. CP group, VDN group and CP + VDN strongly expressed RANKL of rats periodontal tissues, but in group C the expression of RANKL was the lowest; RANKL/OPG ratio in CP + VDN was the highest, group C the minimum, and there were significant differences(P<0.05).(3) IHC of the pulp tissue showed that OPG in group C was the highest, while RANKL was strongly expressed in group CP, VDN and CP + VDN, RANKL/OPG ratio in CP + VDN group was the highest and minimum in group C, and there were significant difference(P <0.05). 3.OPG and RANKL expression in vascular: OPG and RANKL expression in vascular showed the same tendency by ELISA、IHC、Real-time PCR and western blot. OPG level in group CP、VDN was significantly lower than that in C group(P<0.05), what`s more, OPG in group CP+VDN was statistically insignificant when compared with C group(P >0.05); RANKL in group CP、VDN were significantly higher than that in CP+VDN and C group; RANKL/OPG in CP、VDN group was higher than that in group CP+VDN and group C, and there were significant difference(P <0.05). RANKL/OPG ratio in group CP+VDN was statistically insignificant when compared with C group(P >0.05).Conclusion: OPG/RANK/RANKL system plays an important role in the relationship between periodontitis and vascular calcification. When periodontitis and vascular calcification exist at the same time, OPG and RANKL may not be a good indicator because the expression can be affected by the other disease.