Xiyan Wang1, Shi-Wen Jiang2, Liguo Wang3, Yanmei Sun1, Fangyan Xu1, Hai He1, Shuo Wang1, Zhenghong Zhang4, Xiaoyan Pan5. 1. Reproductive Medical Center, Jilin Medical University, Jilin 132013, PR China. 2. Center for Reproductive Medicine, Wuxi Maternity and Child Health Care Hospital Affiliated to Nanjing Medical University, Wuxi 214002, PR China. 3. Department of Urology, Affiliated Hospital of Jilin Medical University, Jilin 132013, PR China. 4. Provincial Key Laboratory for Developmental Biology and Neurosciences, Key Laboratory of OptoElectronic Science and Technology for Medicine of Ministry of Education, Fujian Normal University, Fuzhou 350007, PR China. 5. Reproductive Medical Center, Jilin Medical University, Jilin 132013, PR China; Center for Reproductive Medicine, Wuxi Maternity and Child Health Care Hospital Affiliated to Nanjing Medical University, Wuxi 214002, PR China. Electronic address: xpanphd@163.com.
Abstract
AIMS: In order to investigate the effects and mechanism of Bisphenol A (BPA) on the growth of preantral follicles and the maturation of oocytes in vitro, preantral follicles were harvested from mouse ovaries and in vitro cultured for 11 days with different concentrations of BPA (0, 4.5 and 45 μM) for calculating the percentages of antral follicles, denuded oocytes, degenerative oocytes and the maturation rate of oocytes, besides measuring the diameter of follicles and the thickness of cumulus cell layers. METHODS: The contents of estradiol (E2) in the culture media on Day 4, 8 and 10 were detected by ELISA. The estrogen receptor (ER) expression, spindle morphology and chromosome distribution in oocytes on Day 10 and 11 were observed by immunofluorescence. Western blotting was used to detect the expressions of growth differentiation factor 9 (GDF-9), bone morphogenetic protein-15 (BMP-15), phosphorylated extracellular signal-regulated kinase 1 (p-Erk1) and phosphorylated Ca2+/calmodulin-dependent protein kinase II (p-CaMKII) in the oocytes. RESULTS: Compared with control, BPA (45 μM) significantly reduced percentages of antral follicles (9.25% vs. 91.17%, P < 0.05) and the maturation rate of oocytes (7.61% vs. 79.83%, P < 0.05), but increased the percentages of denuded oocytes (30.29% vs. 3.36%, P < 0.05) and degenerative oocytes (45.70% vs. 2.45%, P < 0.05). The diameter of follicles and the thickness of the cumulus cell layers were decreased significantly (P < 0.05). Moreover, BPA (45 μM) significantly decreased E2 contents in the culture medium on Day 8 and 10 (P < 0.05) and the expressions of ER, GDF-9 and BMP-15 in oocytes (P < 0.05). Furthermore, BPA (4.5 and 45 μM) treatment resulted in the abnormal spindle morphology and chromosome distribution, and the decreased expressions of p-Erk1 and p-CaMKII in the MII oocytes. CONCLUSION: Together, these results clearly demonstrated BPA retarded the preantral follicle growth in vitro through interfering with the synthesis and secretion of E2 and reducing the expressions of ER, GDF-9 and BMP-15, and led to the abnormal meioses of oocytes through reducing p-Erk1 and p-CaMKII expressions in the preantral follicles, which will help us to further unsderstand the mechanism of BPA exposure retarding in vitro growth of preantral follicles and maturation of oocyes.
AIMS: In order to investigate the effects and mechanism of Bisphenol A (BPA) on the growth of preantral follicles and the maturation of oocytes in vitro, preantral follicles were harvested from mouseovaries and in vitro cultured for 11 days with different concentrations of BPA (0, 4.5 and 45 μM) for calculating the percentages of antral follicles, denuded oocytes, degenerative oocytes and the maturation rate of oocytes, besides measuring the diameter of follicles and the thickness of cumulus cell layers. METHODS: The contents of estradiol (E2) in the culture media on Day 4, 8 and 10 were detected by ELISA. The estrogen receptor (ER) expression, spindle morphology and chromosome distribution in oocytes on Day 10 and 11 were observed by immunofluorescence. Western blotting was used to detect the expressions of growth differentiation factor 9 (GDF-9), bone morphogenetic protein-15 (BMP-15), phosphorylated extracellular signal-regulated kinase 1 (p-Erk1) and phosphorylated Ca2+/calmodulin-dependent protein kinase II (p-CaMKII) in the oocytes. RESULTS: Compared with control, BPA (45 μM) significantly reduced percentages of antral follicles (9.25% vs. 91.17%, P < 0.05) and the maturation rate of oocytes (7.61% vs. 79.83%, P < 0.05), but increased the percentages of denuded oocytes (30.29% vs. 3.36%, P < 0.05) and degenerative oocytes (45.70% vs. 2.45%, P < 0.05). The diameter of follicles and the thickness of the cumulus cell layers were decreased significantly (P < 0.05). Moreover, BPA (45 μM) significantly decreased E2 contents in the culture medium on Day 8 and 10 (P < 0.05) and the expressions of ER, GDF-9 and BMP-15 in oocytes (P < 0.05). Furthermore, BPA (4.5 and 45 μM) treatment resulted in the abnormal spindle morphology and chromosome distribution, and the decreased expressions of p-Erk1 and p-CaMKII in the MII oocytes. CONCLUSION: Together, these results clearly demonstrated BPAretarded the preantral follicle growth in vitro through interfering with the synthesis and secretion of E2 and reducing the expressions of ER, GDF-9 and BMP-15, and led to the abnormal meioses of oocytes through reducing p-Erk1 and p-CaMKII expressions in the preantral follicles, which will help us to further unsderstand the mechanism of BPA exposure retarding in vitro growth of preantral follicles and maturation of oocyes.