Changes in the ultrastructure of oocytes / follicles with polycystic ovarian syndrome following freezing-thawing

Changes in the ultrastructure of oocytes / follicles with polycystic ovarian syndrome following freezing-thawing
Sajedeh Afzalnia,^1,* Fatemeh Ghasemian ,² Tooba Mirzapoor,³
1. Department of Biology, Faculty of Science, University of Guilan, Rasht, Iran
2. Department of Biology, Faculty of Science, University of Guilan, Rasht, Iran
3. Department of Biology, Faculty of Science, University of Guilan, Rasht, Iran
Introduction: Background and purpose: Polycystic ovary syndrome (PCOs) is one of the most common causes of infertility. In cases where fertility does not occur naturally, assisted reproductive techniques are used. One of the methods of assisted reproduction is the cryopreservation. The freezing of oocytes was done for a number of reasons such as; ovarian hyperstimulation syndrome, chemotherapy, parental conflict to have another child which will be felt more in the coming years. There are problems during oocyte freezing-thawing process, including damage to the mitotic spindle and the internal organelles of the oocyte, which is the purpose of the present study.
Methods: Materials and methods: 10 NMRI mice were divided into two groups: control and PCOs group. The PCOs mice were induced by intramuscular injection of 4 mg/kg estradiol valerate dissolved in 0.2 mg Sesame oil once a day. After 60 days, mice in each group were sacrificed, and ovarian tissue collected. The oocytes / follicles were freezed . Thawed oocytes and follicles were cultured for 24 hrs and then examined for ultrastructural changes by transition electron microscopy (TEM).
Results: Results: The freezing process causes vacuoles to form in the oocyte system, which may indicate structural damage. Occurrence of vacuoles in immature oocytes eventually leads to reduced ovarian competence for fertilization or evolutionary disruption in the early stages of the fetus. Ultrastructural changes in mitochondrial complexes and smooth endoplasmic reticulum vesicles were observed in the GV group, which could potentially justify the reduction of ejaculatory efficacy for fertilization due to impaired calcium homeostasis. The size of mitochondrial accumulations and smooth endoplasmic reticulum in the freezing group is smaller than the control group. The follicles are relatively healthy with a clear membrane.
Conclusion: Conclusion: Freezing and thawing process of PCOs oocytes/follicles lead to damages in internal organelles.
Keywords: Keywords: Polycystic ovarian syndrome, Vitrification, Thawing, Oocyte, TEM.