High-resolution 3D reconstruction of human oocytes using FIB-SEM

Abstract

The oocyte plays a pivotal role in the reproduction of our species. Nevertheless, its biology remains poorly understood. Electron microscopy is traditionally used to inspect the ultrastructure of female gametes. However, two-dimensional micrographs contain only fragmentary information about the spatial organization of the complex oocyte cytoplasm. Here, we employed the Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) to explore human oocyte intracellular morphology in three dimensions (3D). Volume reconstruction from high-resolution image stacks provided an unprecedented view of ooplasmic architecture. Organelle distribution patterns observed in 9 donor oocytes, representing 3 maturational stages, documented structural changes underlying the process by which the egg acquires developmental competence. 3D image segmentation was performed to extract information about distinct organelle populations. The quantitative analysis of the organelle abundance revealed that mitochondrion occupies ~ 4.26 % of the maturing oocyte cytoplasm. This proof-of-concept study demonstrates the potential of FIB-SEM imaging to study human oocyte morphology.

The spectrum of in vitro maturation in clinical practice: the current insight

“…Nevertheless, understanding the molecular aspect of the maturation of the oocyte is important. The initial molecules are essential in maintaining the state of mitotic arrest to ensure an excellent long fertility journey in women (42). The cyclic adenosine monophosphate (43) and natriuretic peptide precursor type C (NPPC) and receptor 2 (NPR2) are responsible for this matter.…”