Ultrastructural characteristics of human oocytes vitrified before and after <i>in vitro</i> maturation

Abstract

The development of an effective program that combines in vitro maturation (IVM) and cryopreservation for immature oocytes would represent a novel advance for in vitro fertilization (IVF), especially as a means to preserve the fertility of women in unique situations. The aim of this study was to analyze the ultrastructural characteristics of human oocytes, obtained after controlled ovarian stimulation, to determine whether IVM is best performed before or after vitrification. To this end, we analyzed the following features in a total of 22 MII oocytes: size, zona pellucida and perivitelline space, mitochondria number, M-SER (mitochondria-smooth endoplasmic reticulum) aggregates and M-V (mitochondria-vesicle) complexes, the number of cortical granules and microvilli, and the presence of vacuolization using transmission electron microscopy (TEM). Each oocyte presented a rounded shape, with an intact oolemma, and was surrounded by a continuous zona pellucida and perivitelline space. Statistical analysis comparing oocytes vitrified before or after IVM indicated that there were no significant differences between examined characteristics.

Vitrification of human immature oocytes before and after in vitro maturation: a review

“…In oocytes subjected to vitrification post-IVM, general features were physiologically preserved, with an abundant presence of mitochondria often associated to SER, to form M-SER aggregates, and less frequently to vesicles, to form MV complexes. The number of mitochondria was slightly, but not statistically, higher, respect to oocytes vitrified prior to IVM [71]. From the same study, it seems that oocytes cryopreserved after IVM show slight improvements in term of ultrastructural characteristics of cytoplasm maturation in respect to those vitrified before IVM [71].…”

“…The number of mitochondria was slightly, but not statistically, higher, respect to oocytes vitrified prior to IVM [71]. From the same study, it seems that oocytes cryopreserved after IVM show slight improvements in term of ultrastructural characteristics of cytoplasm maturation in respect to those vitrified before IVM [71].…”

“…2c) and the presence of a reduced amount of CGs (Fig. 2d), including the presence of isolated elements in the inner cytoplasm [71], may be due to the superimposition of a possible cryodamage [52]. The reduced number of CG, irrespective of the device used for vitrification (open or closed) ( Fig.…”

Stereological study of organelle distribution in human oocytes at metaphase I

“…Throughout the years, the morphology of human oocytes has been reported by several authors, shedding some light on their ultrastructure at different developmental stages (Hertig and Adams, 1967;Sundstrom, 1985a,b;Sathananthan, 1985;Yang et al, 2009;Morimoto, 2009;Shahedi et al, 2013;Coticchio et al, 2016;Palmerini et al, 2014;Sousa et al, 2016;Segovia et al, 2017). However, none of these studies was exclusively dedicated to human MI oocytes.…”

Oocyte in vitro maturation: A sytematic review

“…In vitro matured oocytes were evaluated ultrastructurally before and after vitrification and vitrified thawed oocytes were compared with previtrified oocytes concerning ultrastructural changes including M-smooth endoplasmic reticulum M-vs, the number of cortical granules, the integrity of oolemma and microvilli, vacuolization, and surrounding zona. The authors concluded that the ultrastructure of matured oocytes from IVM cycles had similar cytoarchitecture in both vitrified-warmed and previtrified oocytes in EM studies ( 111 ) . Dal Canto et al ( 112 ) studied the morphokinetics of embryos derived from in vitro matured oocytes from hCG-primed IVM cycles.…”