Expression Of SPARC In Bone Of Rats Sub-chronically Exposed To Excessive Fluoride

PrefaceBecause of fluoride is disproportion in the crust of the earth,some circumstances have super high level of fluoride.If human body exposes to these circumstances,the fluoride in the body will exceed to normal physiological need,and the fluorion concentration will increase in body fluid and tissues.Then it will cause chronic intoxication in the body,and this is called endemic fluorosis.Natural high-fluoride areas are spread all over the world,and China is the most serious place.The main pathologic change of the disease is to bone,and the clinical appearances are skeletal fluorosis and dental fluorosis.The major express of skeletal fluorosis is acceleration of bone turnover,and osteoblasts and osteoclasts proliferate actively.SPARC(Secreted Protein,Acidic and Rich in Cysteine)is one of the production of osteoblast,and could bind with collagen protein and hydroxylapatite to regulate the interaction between cells and matrix.Simultaneously,it can combine some cytokines to tune up the reconstruction of bone.Some researches have found that SPARC has relationship with certain tumors.So we think SPARC is likely to relevant with bone metabolism.And overdose of fluoride can interfere bone metabolism,too.But the domestic and international literature references were not found about the relationship between SPARC and fluorosis.In view of above,this experiment will be the first to show the relationship between SPARC and fluorosis.And SPARC may play a role in the developed process of skeletal fluorosis.These could deep the genesis mechanism of skeletal fluosis in the molecular level and provide new clues for further study of the phthogenesy of fluorosis. Materials and MethodsSixty Wistar rats were randomly assigned to four groups:a control group,a low-dose fluoride group,a middle-dose fluoride group and a high-dose fluoride group. The rats in the control group were fed with spring water,and the others with different dose of fluoride water till they were killed at different months.We copied the dringking-water type subchronic fluorosis animal models under normal diets.The levels of the rats' fluoride content in bone,serum and urine were analyzed by fluoride ion selective electrode(FISE)method.And immunohistochemistry was used to detect the expression of SPARC in rat bone tissues taken from distal femur.Meanwhile,HE staining was also used to checked the bone density.And dental fluorosis was defied every two weeks.Data got from the experiment was showed by(?)±S,and analyzed with SPSS statistics software for windows 13.0.ANOVA was used to measure differences in the degree of different dose fluoride groups at intervals.The size of testαwas set 0.05.ResultsMost of rats in fluoride treated groups displayed dental fluorosis and the subchronic fluorosis animal models were made successfully.The fluoride content in bone,serum and bone all increased with the fluoride dose rising.There were significant differences among different fluoride dose groups at the same period(p＜0.001).While in the interval of this experiment,significant differences were also found among different periods at the same dose group(p＜0.001).Found from HE staining,distal epiphyseal disk proximal tissue of the fluoride groups became more active and trabecula of bone were much more thicker compared with the control group.And the demarcation between cortex and medulla was not clear in fluoride groups.The expression of SPARC in bone in the high-dose and middle-dose fluoride groups was a little lower than the control group.At the end of the experiment period,the expression of SPARC showed raised first and then reduced.And the middle-dose fluoride group in the end of the third month was the lowest.ConclusionsThe content of fluoride in bone,serum and urine in rats of fluoride treated groups were significantly different compared with the control group with the fluoride dose rised and time prolonged.This was the first to show the relationship between SPARC and fluorosis.We found that the expression of SPARC in bone was associated with rats exposed to subchronic excess fluorine.The expression of SPARC in bone tissues was significantly different in different time,and it increased first and then decreased with time extending.At the end of the third month,the expression descended and then rised with the dose of fluoride advancing.And it might play a role in the process of skeletal fluorosis.It needs further research to discover which period SPARC exert its functions. Then it could provide new clues for further study of the phthogenesy of fluorosis.