The fact that the cells are not rejected, in fact in the hypomyelinated mice actually completely replaced the mouse brain cells, is amazing and terrifying.
http://www.jneurosci.org/content/34/48/16153.abstract
An amazing model for brain study; a terrifying revelation highlighted by the fact that the authors considered replicating this in monkeys, but decided against it. You know that someone will do it. The future of pets? Will we be asking our dogs advice??