Neuralized Mouse Embryonic Stem Cells Develop Neural Rosette-Like Structures in Response to Retinoic Acid and Produce Teratomas in the Brains of Syngeneic Mice

Several induction protocols can direct differentiation of mouse embryonic stem cells (ESCs) to become neural cells. The B5 and B6 mouse ESC lines display different growth patterns in vitro, and when grown as adherent cultures, the B6 ESCs proliferated at a significantly lower rate than B5 ESCs. Remarkably, after a neural induction protocol that includes removal of LIF and addition of retinoic acid (RA), mature B6 embryoid bodies (EBs) displayed a unique neural rosette-like morphology. On Day 8 of neural induction, B6 EBs revealed mature neuronal markers localized primarily to cells in the center of the EBs and glial markers expressed both in centrally and peripherally located cells. In contrast to B5 cells, when neuralized Day 8 B6 EB cells were dissociated and transplanted into the left striatum of syngeneic C57BL/6 mouse brains, teratomas formed. In addition, teratomas established from undifferentiated B6 cells grew more rapidly and achieved larger volumes when compared to those produced by Day 8, neuralized B6 EBs. The slow growth rate of B6 cells in vitro may have contributed to incomplete neuralization, formation of neural rosette-like structures, and a propensity to form teratomas.