220 NONHUMAN PRIMATE EMBRYONIC STEM CELLS SIMILAR TO THE BIOLOGICAL PROPERTIES OF MOUSE EMBRYONIC STEM CELLS

Human and mouse embryonic stem (ES) cells are derived from the inner cell mass of preimplantation blastocysts and human ES cells were long thought to be equivalent to mouse ES cells, despite clear morphological difference and different signalling pathways to maintain their pluripotency between these two ES cell types. Mouse ES cells depend on leukemia inhibitory factor (LIF) and bone morphogenic protein 4 (BMP4) signalling, whereas their human counterparts rely on basic fibroblast growth factor (bFGF) and activin A signalling. The biggest difference of two ES cells is the ability of chimera formation and mouse ES cells can contribute chimera but primate ES cells fails to do that. Monkey ES cells in primates only can be tested for chimera formation in vivo due to the ethical issue and cynomolgus monkey is the most common nonhuman primate to be used for the safety study of drug discoveries. The objective of this study was to develop novel cynomolgus monkey ES cells that have similar biological properties with mouse ES cell and our ultimate goal is to establish germline competent nonhuman primate ES cells. Ovarian stimulation and oocyte collection were carried out for the derivation of ES cells as previously described by Torii et al. Briefly, GnRH (0.9 mg/head) was administered to cynomolgus monkey and two weeks later, a micro infusion pump (iPRECIO™, Primetech Corp) contains FSH was implanted subcutaneously. Follicular aspiration was then performed 40 h after hCG injection and metaphase II oocytes were fertilized by intracytoplasmic sperm injection (ICSI). Cynomolgus monkey ES cells were then established under mouse ES cell conditions such as LIF/STAT signalling and a dome tree-dimensional (3D) morphology nonhuman primate ES cells were selected. On the other hands, ES cells that were established with the presence of basic FGF showed conventional layer-type morphology. Dome-type ES cells express pluripotent transcriptional factors such as Oct-3/4, Nonog and Sox2 as same as layer-type ES cells and both ES lines were capable of multilineage differentiations in vitro after embryoid body formation. Dome-type nonhuman ES cells can also form teratomas and differentiated into all three germ layers when grafted into immunodeficiency mice. For fluorescent gene delivery to nonhuman primate ES cells, feeder-free condition was applied and CAG-GFP vector was transfected into ES cells using Neon electroporation system (Invitrogen Inc.) for the tracing ES cells in the transplantation study. In this study, we have established dome-type ES cell lines that similar to mouse ES cells in morphology and signalling pathway. Dome-type nonhuman primate ES cells express pluripotent gene markers and prove their pluripotency both of in vitro and in vivo, in addition, these modifications would be important to create germline competent ES cells.