Reproduction Abstracts

Introduction: A role for oocyte core 1-derived O-glycans in the regulation of ovarian follicle development has previously been shown using the C1galt1^F/F:ZP3Cretransgenic mouse model. In this model, oocyte-specific ablation of core 1-derived O-glycans results in a sustained increase in ovulation rate and fertility, which is hypothesized to be due to changes in follicle development. In this study, we sought to characterise the role of oocyte core 1-derived O-glycans in ovarian follicle development by comparing follicle morphology and development between Control (C1galt1^F/F) and Mutant (C1galt1^F/F:ZP3Cre) females at 2 weeks of age.

Methods: This study was approved by the Local Ethical Review Panel (University of Oxford). Ovaries were collected from 2 week-old Control and Mutant mice, fixed in formalin, embedded in paraffin, serially sectioned at 5 μm, and stained with haematoxylin. Photographs were taken at ×40 magnification. A set of morphological criteria was defined and used to classify follicles by stage of development, and the proportion of follicles at each stage per ovary calculated. Measurements were taken, using ImageJ software, of several morphological variables including follicle area, antral area and number of granulosa cells per follicle.

Results and discussion: We found that the mean antral area was significantly smaller in 2 week-old Mutant follicles compared with Controls, despite no difference in mean follicle area. Mutant follicles also had an increased number of granulosa cells (whose accumulation is an indicator of follicle development) per follicle at the preantral stage. These results suggest that development of follicles containing oocytes that lack core 1-derived O-glycans is prolonged, delaying antrum formation. This study was partially funded by Nuffield Department of Obstetrics and Gynaecology.