Enhanced viability and neuronal differentiation of neural progenitors by chromaffin cell co-culture

The transplantation of neural stem cells and progenitors has potential in restoring lost cellular populations following central nervous system (CNS) injury or disease, but survival and neuronal differentiation in the adult CNS may be insufficient in the absence of exogenous trophic support. Adrenal medullary chromaffin cells produce a trophic cocktail including basic fibroblast growth factor (FGF-2) and neurotrophins. The aim of this study was to evaluate whether chromaffin cells can provide a supportive microenvironment for neural progenitor cells. In order to assess this, the growth and differentiation of neural progenitor cell cultures from embryonic rat cortex were compared in standard FGF-2-supplemented neural progenitor growth media, in standard media but lacking FGF-2, or in media lacking FGF-2 but co-cultured with bovine chromaffin cells. Using bromodeoxyuridine (BrdU)-prelabeling, findings indicated poor survival of progenitor cultures in the absence of FGF-2. In contrast, the addition of chromaffin cells in co-culture appeared to 'rescue' the progenitor cultures and resulted in robust neurospheres containing numerous BrdU-labeled cells interspersed with and closely apposed to chromaffin cells. As indicated by H3 labeling, cells in co-cultures continued to proliferate, but at a substantially reduced rate compared with standard FGF-2 supplemented growth media. The co-cultures contained more beta-tubulin III-positive processes than parallel cultures maintained in FGF-2-supplemented media and these cells displayed a more mature phenotype with numerous varicosities and complex processes. These findings indicate that chromaffin cells can provide a supportive environment for the survival and neuronal differentiation of neural progenitor cells and suggest that their addition may be useful as a sustained source of trophic support to improve outcomes of neural stem cell transplantation.