Comparison of the effects of Ham'sF10 and αMEM in combination with FBS or BSA in vitrification/warming solution on quality and viability of sheep ovarian follicles

Optimized study of an in vitro 3D culture of preantral follicles in mice

BACKGROUND

In vitro culture of preantral follicles is a promising technology for fertility preservation.

OBJECTIVES

This study aims to investigate an optimized three-dimensional (3D) fetal bovine serum (FBS)-free preantral follicle culture system having a simple and easy operation.

METHODS

The isolated follicles from mouse ovaries were randomly divided in an ultra-low attachment 96-well plates supplement with FBS or bovine serum albumin (BSA) culture or encapsulated with an alginate supplement with FBS or BSA culture. Meanwhile, estradiol (E₂) concentration was assessed through enzyme-linked immunosorbent assay of culture supernatants. The diameter of follicular growth was measured, and the lumen of the follicle was photographed. Spindle microtubules of oocytes were detected via immunofluorescence. The ability of oocytes to fertilize was assessed using in vitro fertilization.

RESULTS

The diameters were larger for the growing secondary follicles cultured in ultra-low attachment 96-well plates than in the alginate gel on days 6, 8, and 10 (p < 0.05). Meanwhile, the E₂ concentration in the BSA-supplemented medium was significantly higher in the alginate gel than in the other three groups on days 6 and 8 (p < 0.05), and the oocytes in the FBS-free system could complete meiosis and fertilization in vitro.

CONCLUSIONS

The present study furnishes insights into the mature oocytes obtained from the 3D culture of the preantral follicle by using ultra-low attachment 96-well plate with an FBS-free system in vitro and supports the clinical practices to achieve competent, mature oocytes for in vitro fertilization.

Silk fibroin sheet multilayer suitable for vitrification of in vitro-matured bovine oocytes

Minimum volume cooling (MVC) procedure has been successfully applied to vitrify mammalian oocytes, but high skill of capillary pipetting is required to load the oocytes on a cryodevice with a minimal volume (<1 μL) of vitrification solution (VS). Here we report a novel cryodevice for bovine oocyte vitrification, silk fibroin (SF) sheet multilayer, of which spontaneous absorption property can eliminate pipette operation for removal of excess VS. Based on physical stability and scanning electron microscopic observation, the SF sheet prepared from 1.5% (wt/vol) fibroin solution was selected and layered around a polypropylene strip (0.1-mm thickness, 0.7-mm width, 10-mm depth). Ten denuded bovine mature oocytes were loaded onto the SF sheet multilayer with 2-3 μL of the VS, and then cooled rapidly by plunging into liquid nitrogen. Nylon mesh (NM) device with square opening 37-μm length of a side and commercially available Cryotop® (CT) device were used as controls, and the minimization of VS volume was performed by paper towel absorption and capillary aspiration, respectively. In SF, NM and CT groups, post-warming oocyte recovery rates were 99.5, 99.1 and 100%, and the morphological survival rates were 99.7, 94.5 and 99.0%, respectively. Subsequent IVF and 8-days IVC resulted in comparable blastocyst yields among the three groups (25.5, 25.0 and 26.1% in SF, NM and CT groups, respectively). These results suggest that SF sheet multilayer is a useful cryodevice for bovine matured oocytes in MVC vitrification because VS volume surrounding the oocytes can be easily minimized through its absorption property.