Effects of different culture systems on in vitro growth of porcine oocytes from preantral follicle

Abstract

In vitro growth of preantral follicles is a leap forward for assisted reproductive technology with large reserves to preserve fertility. Small oocytes require interaction between the ovarian cell and oocyte components to reach their full ability. However, culture systems that support the tight connection of cells remain have not yet shown significant progress. Conventional two-way culture has impeded the growth of large animal follicles, which are spherical and require a long incubation period. In addition, the 2D culture system breaks down the association between oocytes and surrounding granulosa cells, leaving the oocytes bare and unable to progress to maturation. The oocytes had greater ability in the matrix with high supporting flexibility to sustain the follicles in culture for an extended period. In this study, we report the effect of using agarose as a soft substrate for porcine oocyte culture and development. Oocytegranulosa cell complexes (OGs) obtained from 0.3-0.4 mm follicles were established on plates coated with 1% agarose (w/v) compared with a conventional 2D culture system. We then evaluated the connection of granulosa cells with oocytes, follicular expansion, the abundance of lipids, developmental competence, and chromatin configuration in oocytes after culture for 14 days. The oocyte-cumulus-granulosa complexes (OCGs) cultured on agarose gel conditions showed significantly greater antrum formation, granulosa cell proliferation, and oocyte-ovarian cells adhesion, resulting in improvement of lipid content, size of oocytes, and several oocytes reaching the germinal vesicle stage than those cultured on the standard 2D culture system method. The results indicated that porcine oocyte-derived preantral follicles cultured in a 3D agarose system created a sufficient soft matrix that could help oocyte development and significantly reduce the extrusion of oocytes.