Vitrification does not alter ultrastructure of human oocyte cumulus cells
Neda Taghizabet (IR)
[Taghizabet] Yazd Reproductive Science Research Center
Context: Cumulus cells (CCs) have been implicated in the regulation of female gamete development, meiotic maturation, oocyte - sperm interaction, and capacitation. However, cryopreservation of cumulus oocyte complex (COCs) is a problematic issue derived from their sensitivity to the process of freezing. Objective : The aim was to describe the possible effect of vitrification on ultrastructure of CCs of human mature oocytes collected from infertile patients. Sample collected : A total of 50 CCs of surplus human mature oocytes collected during ICSI procedure were allocated into two groups: Methods : Group I, control fresh CCs (n=25); Group II, vitrified CCs (n=25). Finally,10 samples from each group were selected and the ultrastructural changes of CCs were analyzed using transmission electron microscopy. Results: In group I, the Golgi apparatus, Rough Endoplasmic Reticulum (RER), Vesicles, Nucleus with Nucleolus, free Ribosome and Lipid droplets were observed close to the membrane surface. However, lipid droplets were seen most dense both in peri-nuclear space and cortical membrane in group II. Also, oval Nuclei with nucleoli were other findings in group II.In some cells, Microvilli were observed in vitrified CCs surface, while there were Gap junctions in fresh CCs surface. A few vacuolations was the cryoinjury phenomenon in group II.Also similar group I, the same organelles of Golgi apparatus, RER, free Ribosome and mitochondria were other findings. Conclusion: The vitrifiction procedure did not cause noticeable alteration, in the fine structure of CCs organelles. Hence, it may be possible to cryopreserve the intact COCs for preserving oocyte integrity.