Further challenges include the identification
of signaling molecules that promote the generation
of beneficial populations
of astrocytes, identification
of appropriate stem and / or progenitor
cell populations that can be the
source of such
cells, and determination
of whether there are situations in which it is more useful to transplant astrocytes themselves rather than to transplant
stem or progenitor
cells that might generate astrocytes in vivo in response to signals present in the host environment.