Generation of embryonic stem cell lines from immature rabbit ovarian follicles

In mammalian ovaries, many immature follicles remain after the dominant follicles undergo ovulation. Here we report the successful production of rabbit embryonic stem cells (ESCs) from oocytes produced by in vitro culture of immature follicles and subsequent in vitro maturation treatment. In total, we obtained 53 blastocysts from oocytes that received intracytoplasmic sperm injection followed by in vitro culture. Although only weak expression of POU5f1 was observed in the inner cell masses of in-vitro-cultured follicle-derived embryos, repeated careful cloning enabled establishment of 3 stable ESC lines. These ESC lines displayed the morphological characteristics of primed pluripotent stem cells. The ESC lines also expressed the pluripotent markers Nanog, POU5f1, and Sox2. Further, these ESCs could be differentiated into each of the 3 different germ layers both in vitro and in vivo. These results demonstrate that immature follicles from rabbits can be used to generate ESCs. Moreover, the use of rabbit oocytes as a cell source provides an experimental system that closely matches human reproductive and stem cell physiology.