Application of Allograft Endometriosis Rat Model in Pharmaco-dynamic Evaluation of GnRH Agonists

Objective To establish an allogeneic rat model of endometriosis and to evaluate the effects of gonadotropin-releasing hormone (GnRH) agonist GenSci006 on experimental rat endometriosis. Methods Endometrium from SPF grade donor female SD rats were transplanted onto the abdominal wall of recipient female rats to construct an allogeneic endometriosis model. The rats undergoing sham surgery were divided into the sham group. Three weeks later, the length, width and height of the ectopic endometrium were measured, and the volume of the endometrium (V1) was calculated before drug administration. The modeling rats were randomly divided into four groups: model group, triptorelin group (0.25 mg/kg), GenSci006-1 group (0.125 mg/kg) and GenSci006-2 group (0.25 mg/kg). Each group had 16 rats and received a single dose of the corresponding drug. The sham group and model group were administered an equal volume of solvent. Three weeks after administration, ectopic endometrium was measured to calculate the volume V2 and inhibition rate. The effect of GenSci006 on rat uterus and ovarian tissues was assessed by comparing organ coefficients and changes in pathological sections. Enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of serum estradiol (E2), progesterone (P4), follicle stimulating hormone (FSH), and luteinizing hormone (LH). Real-time fluorescent quantitative PCR was used to detect the expression of GnRH receptor (GnRHR) mRNA in the hypothalamus and pituitary. Western blot was used to detect the expression of estradiol receptor alpha (ERα), beta (ERβ) and progesterone receptor (PR) in ectopic endometrium. Results Three weeks after administration, compared with the model group, the body weight of rats in the triptorelin and GenSci006-2 groups significantly increased (P < 0.05), while the volume of ectopic endometrium significantly decreased (P < 0.05). Compared with the sham group, the model group showed no significant changes in uterine and ovarian organ coefficients or endometrial thickness (P > 0.05). Compared with the model group, the uterine organ coefficients and endometrial thickness were significantly reduced in the triptorelin and GenSci006-2 groups (P < 0.05). Compared with the sham group, the serum levels of E2, P4, FSH and LH in the model group showed no significant changes (P > 0.05). Compared with the model group, the ovarian organ coefficient and serum P4 levels of rats in the Triptorelin, GenSci006-1, and GenSci006-2 groups were significantly reduced (P < 0.05), while the serum LH levels of rats in the GenSci006-1 group were significantly increased (P < 0.05). However, there were no significant changes in serum E2 and FSH levels in each group (P > 0.05). Compared with the model group, the expression levels of GnRHR mRNA in the pituitary tissue of rats in the triptorelin and GenSci006-2 groups were significantly downregulated (P < 0.05), with no significantly changes in the hypothalamus (P > 0.05). There were no significant changes in the expression level of GnRHR mRNA in the hypothalamus or the protein levels of ERα, ERβ and PR in the ectopic endometrial tissue in any group (P > 0.05). Conclusion The allogeneic endometriosis rat model is a suitable animal model for screening and evaluating drugs for treating endometriosis. The volume of ectopic endometrium, inhibition rate, uterine and ovarian organ coefficients, and serum E2 levels may serve as indicators for detecting drug efficacy.