Fe3O4 magnetic nanoparticles improve the vitrification of mouse immature oocytes and modulate the pluripotent genes expression in derived pronuclear-stage embryos.

ABSTRACT

The vitrification of Germinal Vesicle (immature) oocytes is beneficial for preservation of fertility in cases involving reproductive problems. The use of nanoparticles (NP(s)) as vitrification aid is a novel approach towards improving vitrification efficiency. The efficacy of use of iron oxide (Fe3O4) nanoparticles as vitrification aid is reported in this paper. Immature oocytes from NMRI mice were collected and divided into non-vitrified (nVit), Vitrified (Vit) and Vitrified + NP (Vit+NP) groups. In the Vit+NP group, solutions containing Fe3O4 nanoparticles at three different concentrations (0.004%, 0.008% and 0.016% w/v) were separately added to the vitrification solution and their effects on the vitrification of the oocytes were compared. The concentration that was found to be best performing (0.004% w/v) was used in vitrification studies in subsequent experiments. Mitochondrial function, apoptosis incidence, ultrastructure alteration, nuclear maturity, embryo formation and genes expression (Nanog, Oct4, Cdx2, and Sox2) were evaluated in response to the addition of the nanoparticle solution during vitrification. Nuclear maturity of oocyte and embryo formation increased significantly (P ≤ 0.05) in the vitrified + NP group. Expression of Sox2 also increased significantly in both vitrified and vitrified + NP groups. While there was a significant increase in Oct4 expression in the vitrified group as compared to control, there was no significant difference between vitrified and Vit+NP groups. The expression of Cdx2 decreased significantly (P ≤ 0.05) in the Vit+NP group. From these observations, Fe3O4 nanoparticles could protect immature oocytes from cryodamages, positively affect vitrification and modulate the pluripotency of derived pronuclear-stage embryos.