| Objective:In this experiment,cyclophosphamide was used to induce premature ovarian failure in rats,which resulted in the decrease of serum estrogen,and then the changes of condylar cartilage and subchondral bone were observed by intragastric administration of different concentrations of estrogen.It aims to explore the pathogenesis of ICR and whether if estrogen supplementation therapy can be applied to ICR or not,and to search for the best concentration of estrogen therapy.Methods:75 female SD rats with normal estrous cycle for 6 weeks were randomly divided into 5 groups.Group A: CTX+ estradiol group(0.0525mg/kg estrogen treatment group):First,the amount of CTX was calculated according to the weight of the rats.The cyclophosphamide was diluted into 1 ml sodium chloride injection.The first dose of cyclophosphamide was injected intraperitoneally at 50 mg / kg,then the maintenance dose of 8 mg / kg was injected for 14 days.Then in the 4th week of the experiment,the dose of estradiol valerate was calculated according to the weight of the rats.The dose of estradiol valerate was calculated as 0.0525 mg / kg.Estradiol valerate was diluted into 1 ml sodium chloride injection to form suspension.The suspension was prepared by gavage daily and administered through gastrointestinal tract until the end of the 12 th week.Group B: CTX+ estradiol group(0.105mg/kg estrogen treatment group):First,the amount of CTX was calculated according to the weight of the rats.The cyclophosphamide was diluted into 1 ml sodium chloride injection.The first dose of cyclophosphamide was injected intraperitoneally at 50 mg / kg,then the maintenance dose of 8 mg / kg was injected for 14 days.Then in the 4th week of the experiment,the dose of estradiol valerate was calculated according to the weight of the rats.Thedose of estradiol valerate was calculated as 0.105 mg / kg.Estradiol valerate was diluted into 1 ml sodium chloride injection to form suspension.The suspension was prepared by gavage daily and administered through gastrointestinal tract until the end of the 12 th week.Group C: CTX+ estradiol group(0.21mg/kg estrogen treatment group):First,the amount of CTX was calculated according to the weight of the rats.The cyclophosphamide was diluted into 1 ml sodium chloride injection.The first dose of cyclophosphamide was injected intraperitoneally at 50 mg / kg,then the maintenance dose of 8 mg / kg was injected for 14 days.Then in the 4th week of the experiment,the dose of estradiol valerate was calculated according to the weight of the rats.The dose of estradiol valerate was calculated as 0.21 mg / kg.Estradiol valerate was diluted into 1 ml sodium chloride injection to form suspension.The suspension was prepared by gavage daily and administered through gastrointestinal tract until the end of the 12 th week.Group D: CTX group:First,the amount of CTX was calculated according to the weight of the rats.The cyclophosphamide was diluted into 1 ml sodium chloride injection.The first dose of cyclophosphamide was injected intraperitoneally at 50 mg / kg,then the maintenance dose of 8 mg / kg was injected for 14 days.Group E: blank control group: free diet without any treatment.Serum estradiol concentration was detected before the experiment,at 4th,8th,and 12 th of experiment.Five rats were executed at 4th,8th,and 12 th respectively.The condylar process was made into the section,followed by HE staining and observation of condylar cartilage morphology.Imgpro plus6.0 software was used to detect the bone parametersof rat condyle(number of trabeculae,trabecular spacing,thickness of trabecular bone).Results:(1)Serum E2 concentration measurement:I: At 4th of experiment,the serum E2 concentration in group A?group B?group C and group D was significantly decreased compared with that in group E,The levelof serum E2 in groupB was higher than that in group A and group C,and the difference was statistically significant(P<0.05).II: At 8th,12 th of experiment,the serum E2 concentration in group A?group B and group C was significantly increased compared with that in group D.The level of serum E2 in groupB was higher than that in groupA and group C,and the difference was statistically significant(P<0.05).The concentration of estradiol in group A ?group B and group C at the 12 th week was higher than that of at the 12 th week,and the difference was statistically significant(p < 0.05).(2)Morphologic change in condylar cartilage:I: At 4th of experiment,Compared with group E,the condylar cartilage structure of group A?group B?grooup C and group D was changed,the thickness of the cell layer decreased obviously,and the cell arrangement was disordered.The number of trabeculae decreased and the arrangement of bone trabeculae was loose,showing the degenerative change.II: At 8th,12 th of experiment,Compared with group D,the thickness of condylar cartilage of group A?group B and group C was increased,showing the reparative change.The repair changes were the most obvious in group B(P<0.05).(3)The morphological changes of subchondral bone:I: At 4th of experiment,compared with group E,the number and thickness of trabecular bone in group A?group B?group C and group D were increased,and trabecular bone spacing were widenethe difference was statistically significant(P<0.05).II: At 8th,12 th of experiment,Compared with group D,the number and thickness of trabecular bone in group A?group B and group C were decreased,and trabecular bone spacing were narrowed.The changes were the most obvious in group B,and the difference was statistically significant(P<0.05).There was no significant difference in the number and thickness of trabecular bone ? the trabecular bone spacing between 8th and 12 th week in group A?group B ? group C and group D(p > 0.05).conclusion:1: Under the experiment condition,Decrease of serum estradiol concentration induced by cyclophosphamide in rats,the thickness of condylar cartilage in rats was decreased with disordered cell structure,the number of trabecular bone was thinning and the bone marrow cavity was enlarged.2: Under the experiment condition,the administration of different concentrations of estrogen(0.0525 mg / kg ?0.105 mg / kg ?0.21 mg / kg)via gastrointestinal tract can increase the serum E2 concentration in rats and thickness of condylar cartilage and subchondral bone with reparative changes.And when the concentration was 0.105 mg / kg,the repair change was the most obvious. |
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