Effect Of ?-cryptoxanthin On Alveolar Bone Absorption Of Experimental Periodontitis In Rats

BackgroundInflammatory cytokines and the chemokines upregulate the expression of receptor activator of nuclear factor kappa B ligand(RANKL)in the course of periodontitis lesions.RANKL activates osteoclast(OC)precursor cells.Then Mature multinuclear OC adsorbs onto the surface of mineralized bone matrix for bone resorption.Alveolar bone resorption is the main cause of tooth loosening and shedding.The key to cure periodontitis is to prevent the absorption of alveolar bone and promote the restoration and regeneration of alveolar bone.?-cryptoxanthin is a kind of carotenoid,which is found in fruits and vegetables.?-cryptoxanthin can prevent bone loss by stimulating osteoblastic bone formation and inhibiting osteoclastic bone absorption.Previous studies have found that low level of ?-cryptoxanthin in serum is associated with the increase of periodontitis in the prevalence.The level of ?-cryptoxanthin in serum of patients with periodontitis is significantly lower.?-cryptoxanthin can inhibit lipopolysaccharide(LPS)-induced inflammatory reaction,downregulate the ratio of RANKL /osteoprotegerin(OPG).Injection of ?-cryptoxanthin can inhibit LPS-induced alveolar bone density(BMD)decrease.These studies have shown that ?-cryptoxanthin can affect the development of periodontitis.However,there are few studies on the effect of ?-cryptoxanthin on the alveolar bone resorption of periodontitis,and its mechanism is not very clear.ObjectiveThe purpose of this study was to evaluate the effect of ?-cryptoxanthin on periodontal tissue of rats with experimental periodontitis by detecting alveolar bone loss(ABL),the number of OC and the expression of RANKL and OPG.Its possible mechanism of action in vivo was analyzed.MethodsThirty Sprague Dawley(SD)male rats were divided into three groups by random assignment: 1)normal control(N);2)periodontitis model(P);3)?-cryptoxanthin intervention(E).Group P and group E were induced experimental periodontitis.Rats in group E were intervened with ?-cryptoxanthin.To induced experimental periodontitis model,orthodontic ligature wire of 0.2 mm diameter was binded around the neck of the bilateral maxillary second molar and the buccal gingival sulcus received an injection of bacillus coli lipopolysaccharide(LPS)(30?l/ rat)every 48 hours,a total of three times.As control,group N was injected with saline.Rats in group E were injected with ?-cryptoxanthinin(12?l/ rat)after LPS injection at the same site every 48 hours,a total of three times.Group P accepted equal amounts of corn oil instead of ?-cryptoxanthinin.The rats were executed by intraperitoneal injection of overdose 10% chloral hydrate at the eighth day.Removed bilateral maxillary tissue(including teeth,gums and alveolar bone).Morphological analysis was performed to evaluate the distance between alveolar bone crest(ABC)and Cemento-enamel junction(CEJ)for right maxillary specimens.For left maxillary samples,histological and immunohistochemical analyses were performed to detect the expression of receptor activator of nuclear factor-kappa B ligand(RANKL)and osteoprotegerin(OPG)nearby the ABC.The osteoclast(OC)were detected by tartrate-resistant acid phosphatase(TRAP).ResultsCompared with group N,ABL increased,junctional epithelium(JE)migrated to the root and alveolar bone resorption obviously in group P,which indicated that periodontitis was successful induced in group p.Group E showed reduced the lower level of ABL,inflammatory cells,RANKL immunolabeling cells and TRAP-positive multinucleated cells when compared to group P(P<0.05).?-cryptoxanthin treatment increased the genic expression of OPG(P<0.05).Meanwhile,there were no differences about ABL and the number of OC between group E and group N(P >0.05).Conclusions?-cryptoxanthin influenced the occurrence and development of periodontitis and inhibited alveolar bone resorption.It possible mechanism was that ?-cryptoxanthin play a role through down-regulating the ratio of OPG/RANKL and reducing the number of OC.