n = 6 blank control group was created. The mice in the control group were fed regular food and gavaged with normal saline daily. The mice in the control group were given a high-fat diet and 1 mg/kg of letrozole via gavage for 21 days to establish a PCOS model of insulin resistance and hyperandrogenism. The mice, after successful modeling, were randomly divided into PCOS group and metformin group (n = 6). During the treatment period, the control group continued to be fed with normal feed and given normal saline; the PCOS group was fed with continuous high-fat feed and given letrozole (1 mg/kg/day) by intragastric administration, and the metformin group was given metformin by intragastric administration (200 mg/kg/day). After 30 days of treatment, the experimental mice were euthanized, serum was collected, one mouse ovary was collected for histological examination, and the other was stored in a -80 refrigerator for molecular biology experimental research.

n = 6 blank control group was created. The mice in the control group were fed regular food and gavaged with normal saline daily. The mice in the control group were given a high-fat diet and 1 mg/kg of letrozole via gavage for 21 days to establish a PCOS model of insulin resistance and hyperandrogenism. The mice, after successful modeling, were randomly divided into PCOS group and metformin group (n = 6). During the treatment period, the control group continued to be fed with normal feed and given normal saline; the PCOS group was fed with continuous high-fat feed and given letrozole (1 mg/kg/day) by intragastric administration, and the metformin group was given metformin by intragastric administration (200 mg/kg/day). After 30 days of treatment, the experimental mice were euthanized, serum was collected, one mouse ovary was collected for histological examination, and the other was stored in a -80 refrigerator for molecular biology experimental research.

Adult female C57BL/6J mice were purchased from Cyagen Bioscience (Santa Clara, CA, USA). Prior to the experiment, the animals were allowed to adapt to the environment for 1 week. For this study, all procedures were approved by the Ethics Committee of Shanghai Seventh Peoples Hospital (item number: 2021-AR-059). Adult female C57BL/6J mice were housed withaccess to food and waterad libitum. The PCOS mouse model was established as described previously. In brief, female C57BL/6J mice (4 weeks old) were subcutaneously injected with DHEA (6 mg/0.1kg body weight) daily for 20 days.

C57BL/6 J (3-week-old) female mice, weighing 15-20 g, were purchased from Beijing Vitalriver Laboratory Animal Technology Co Ltd., China. Experimental animals were randomly divided into control (glycerol treatment) and experimental groups (PCOS, DHEA treatment). The modeling method was as described previously. The PCOS model and control was verified successfully as our previous results, and ovarian tissue was extracted for RT-qPCR detection.

Adult Sprague-Dawley rats (70 days old) of both sexes were purchased from the Laboratory Animal Centre of Harbin Medical University, Harbin, China. Before the experiment, female rats were allowed to acclimatize for a minimum of 1 week and then were monitored daily by vaginal lavage to determine the stage of the estrous cycle as previously described (Zhanget al., 2016). Pregnancy was achieved by housing female rats on the night of proestrus with fertile males of the same strain at a 2:1 ratio. Confirmation of mating was performed the morning after by the presence of a vaginal plug, and this was considered as GD 0.5. The rats were sacrificed between 8:00 a.m. and 9:00 a.m. hours on GD 14.5.

Adult Sprague-Dawley rats (70 days old) of both sexes were purchased from the Laboratory Animal Centre of Harbin Medical University, Harbin, China. Before the experiment, female rats were allowed to acclimatize for a minimum of 1 week and then were monitored daily by vaginal lavage to determine the stage of the estrous cycle as previously described (Zhanget al., 2016). Pregnancy was achieved by housing female rats on the night of proestrus with fertile males of the same strain at a 2:1 ratio. Confirmation of mating was performed the morning after by the presence of a vaginal plug, and this was considered as GD 0.5. The rats were sacrificed between 8:00 a.m. and 9:00 a.m. hours on GD 14.5.

We recruited 12 infertility patients (6 PCOS and 6 controls) aged 20 and 38 who underwent in vitro fertilization (IVF) at the Department of Reproductive Medicine Center, the First Affiliated Hospital of Sun Yat-Sen University. All patients were treated the antagonist stimulation protocol. Briefly, on cycle day 2, ovarian stimulation was started by daily injection of recombinant FSH (r-FSH) (Gonal-F; Merck Serono). Gonadotropin-releasing hormone (GnRH) antagonist (Cetrotide, 0.25 mg; Merck Serono) injection was started from the day 6 of stimulation. When at least three follicles had reached 17 mm or two follicles had reached 18 mm in diameter, an intramuscular injection of 5,000 IU-10000 IU of human chorionic gonadotropin (hCG) is used for triggering final oocyte maturation.

We recruited 12 infertility patients (6 PCOS and 6 controls) aged 20 and 38 who underwent in vitro fertilization (IVF) at the Department of Reproductive Medicine Center, the First Affiliated Hospital of Sun Yat-Sen University. All patients were treated the antagonist stimulation protocol. Briefly, on cycle day 2, ovarian stimulation was started by daily injection of recombinant FSH (r-FSH) (Gonal-F; Merck Serono). Gonadotropin-releasing hormone (GnRH) antagonist (Cetrotide, 0.25 mg; Merck Serono) injection was started from the day 6 of stimulation. When at least three follicles had reached 17 mm or two follicles had reached 18 mm in diameter, an intramuscular injection of 5,000 IU-10000 IU of human chorionic gonadotropin (hCG) is used for triggering final oocyte maturation.