Novel Approach for Ex Vivo Production of Viable Eggs

Kanako Morohaku^1,2, Tomohiro Kohama¹, Ikuo Tomioka^1,2

1. Graduate School of Medicine, Science and Technology, Shinshu University, Minamiminowa-mura, Nagano, Japan

2. Faculty of Agriculture, Shinshu University, Minamiminowa-mura, Nagano, Japan

Abstract Text:

In mammals, ovaries contain numerous oocytes, but more than 99% of them degenerate without ovulation. To date, many trials have been performed to produce viable eggs from these oocytes using ex vivo cultures. Although the first successful report with live birth of offspring was represented by the culture of the entire ovary, the use of a whole or piece of an ovary as a specimen is very limited or almost unfeasible for ex vivo culture in most of mammals because of its size and the presence of thick and hard cortical tissues. Alternatively, oocytes derived from every follicular developmental stage are subjected to culture; in the case of tertiary follicles, fully grown immature oocytes can be collected, followed by in vitro maturation to produce viable eggs. On the other hand, when oocytes derived from follicles at earlier stages than the tertiary follicle stage are targeted for culture, ex vivo culture is initially necessary to require conditions for oocyte growth, especially in the specimens at the primary follicle stage. To address this issue, a novel approach must be developed. In this presentation, we will introduce our current study that enables the production of viable eggs from oocytes at early primary to secondary follicular stages in mice by ex vivo engineering culture system, which includes not only in vitro growth of isolated early primary follicles but also in vitro development of denuded oocytes co-cultured with granulosa cells. This approach may be expected to apply further culture in other mammals, including humans.