【Animal Modeling】-Establishment and Evaluation of Rat Vaginitis Model

  Objective To establish a rat model of vaginitis, and to provide a new model for the development and evaluation of vaginitis treatment drugs.

  METHODS: Vaginal Gardnerella, Streptococcus albicans and Group B Streptococcus strains were isolated and purified from vaginal samples of patients with Gardnerella vaginalis, Streptococcus albicans and Group B Streptococcus. Twenty-six female rats were pretreated with estradiol benzoate (20 mg/kg) and streptomycin (10 μg each) in the morning, the mixed strains were intravaginally inoculated in the afternoon, and 10 female rats were selected for subcutaneous injection of benzoic acid Estradiol (20mg/kg) was used as the normal group, once a day for 3 consecutive days. Vaginal secretions and vaginal washes were collected before grouping to observe the mixed bacterial infection in the vagina of the rats, and 20 rats with successful infection were selected and randomly divided into the model group and the drug validation group according to their body weight and bacterial load (compound metronidazole vaginal suppository for each 54 mg, once a day for 5 consecutive days), 10 animals in each group. The normal group and the model group were given the same amount of 0.9% sodium chloride injection via vagina. After the last administration, vaginal lavage fluid was collected to detect the bacterial load, and vaginal secretions were collected for vaginal smear, cleanliness and pH inspection. The histopathological changes of vaginal tissue were observed by HE staining.

  Results The vaginal wall of the rats in the model group became thicker, the stratified squamous epithelium was degenerated, necrotic and exfoliated, the lamina propria was congested and edema obviously, neutrophils were the main cells, lymphocytes and mononuclear cells were infiltrated, scattered spot hemorrhages, and breast milk were infiltrated. The fibroblasts proliferate obviously in the protruding area, and the reticular fibers proliferate slightly. The number of mixed bacteria, pH value and cleanliness score of vaginal lavage fluid in the model group were significantly greater than those in the normal group (P<0.01), and the negative conversion rate was significantly reduced (P<0.01); The number of mixed bacteria, pH value and cleanliness score of the lavage fluid can increase the vaginal negative conversion rate, and can significantly improve the degree of vaginal tissue lesions.

  Conclusion After pretreatment of rats with estrogen and streptomycin sulfate for injection, mixed bacteria inoculation can successfully establish a rat model of mixed vaginitis, which provides an effective animal model for drug screening and evaluation of female reproductive system.