3D Liquid Marble Microbioreactors Support In Vitro Maturation of Prepubertal Ovine Oocytes and Affect Expression of Oocyte-Specific Factors

SIMPLE SUMMARY: Oocyte in vitro maturation has broad potential for generating embryos for research and for application of assisted reproductive technologies, such as in vitro embryo production. In human, the possibility to efficiently mature oocytes in vitro would solve the reproductive problems of patients with special diseases. Nevertheless, the developmental ability of in vitro matured oocytes is currently lower than those matured in vivo. Here, we used young sheep oocytes as model of low-quality gametes to show that a novel liquid marble 3D culture system is suitable to mature in vitro oocytes with reduced potential, improving the rates of in vitro embryo production. The present findings are useful for the optimization of in vitro maturation systems, and to improve the developmental potential of in vitro matured oocytes. Further applications should be considered also in other species, including human, to mature oocytes with intrinsic low quality. ABSTRACT: In vitro oocyte maturation (IVM) is a well-established technique. Despite the high IVM rates obtained in most mammalian species, the developmental competence of IVM oocytes is suboptimal. The aim of this work was to evaluate the potential beneficial effects of a liquid marble microbioreactor (LM) as a 3D culture system to mature in vitro prepubertal ovine oocytes, as models of oocytes with intrinsic low competence. Cumulus–oocyte complexes of prepubertal sheep ovaries were in vitro matured in a LM system with hydrophobic fumed-silica-nanoparticles (LM group) or in standard conditions (4W control group). We evaluated: (a) maturation and (b) developmental rates following in vitro fertilization (IVF) and embryo culture; (c) expression of a panel of genes. LM and 4W groups showed similar IVM and IVF rates, while in vitro development to blastocyst stage approached significance (4W: 14.1% vs. LM: 28.3%; p = 0.066). The expression of GDF9, of enzymes involved in DNA methylation reprogramming and of the subcortical maternal complex was affected by the IVM system, while no difference was observed in terms of cell-stress-response. LM microbioreactors provide a suitable microenvironment to induce prepubertal sheep oocyte IVM and should be considered to enhance the developmental competence of oocytes with reduced potential also in other species, including humans.