Female BALB/c mice (4-6 weeks old, 18-20 g) were obtained from Shanghai Regan Biotechnology Co., Ltd. (Shanghai, China) and were reared in a specific, pathogen-free facility. After 1 week of acclimatization, mice were randomly divided into two groups: the donor group (n = 10) and recipient groups (n = 10). Ovariosteresis and estradiol valerate injection (0.5 ug/mouse/week; Aladdin, Shanghai, China) was carried out to avoid differences in the estrous cycle. Mice were anesthetized by 2% isoflurane, and then the ovaries on both sides were exposed through flank incisions and removed. Donor mice were sacrificed under isoflurane anesthesia, and each uterine horn of the donor mice was concentrated and peeled in warm PBS to remove uterine muscle. Endometrial tissues were weighed and cut into small fragments with scissors and resuspended in sterile PBS with 1 x ampicillin (Beyotime, Shanghai, China). After that, endometrium preparation was intraperitoneally injected into two recipient mice (50 mg/mouse). Two weeks after EM transplantation, endometriosis lesions and eutopic endometrial tissues were removed from the peritoneal cavities and uteri.