We next addressed whether hESC-derived trigeminal neurons can engraft in the adult mouse CNS and project toward their physiological target. The trigeminal nuclei in the brainstem receive afferent innervation from the trigeminal sensory ganglion that is relayed to the contralateral thalamus. The pons was selected as site for transplantation, because it is surgically accessible and located within proximity of the trigeminal brain stem nuclei that receive afferent input from the trigeminal ganglia. Hence, GFP+ human trigeminal neuron clusters were injected into adult NOD/SCID mice via stereotactic surgery (see Experimental Procedures). Histological analysis 4 weeks after transplantation showed survival of GFP+ human cell graft in the ventral pons (Figure S5E). Although GFP+ cell bodies remained tightly clustered at injection site, GFP+ fibers showed extensive projections into the host brain (n = 6) including the endogenous trigeminal nuclei (Figure S5F). Expression of BRN3A confirmed the sensory neuron identity of the cells (Figure S5G). Graft-derived human fiber bundles (hNCAM+ and GFP+) were observed emanating from the graft core (Figure S5H). These data demonstrate in vivo survival of trigeminal placode derivatives, differentiation along sensory neuron lineage, and the establishment of axonal projections toward relevant endogenous targets in the embryonic chick and adult mouse brain.
Histological analysis
4 weeks
weeks
GFP+ fibers showed extensive projections into the host brain
n
6