Array-based functional screening of growth factors toward optimizing neural stem cell microenvironments.

To gain insights into the effect of various growth factors on the behaviors of neural stem cells, cell culture assays were performed on the array that displayed five different growth factors including basic fibroblast growth factor, epidermal growth factor, insulin-like growth factor-1, brain-derived neurotrophic factor, and ciliary neurotrophic factor. These factors were expressed in Escherichia coli as fusion proteins with a hexahistidine sequence and arrayed on a nickel ion-functionalized chip as single factors or the combination of two factors. Neural stem cells obtained from the fetal rat brain were cultured on the array to investigate their proliferation and differentiation. It was shown that the five growth factors displayed as a single component had significant impacts on cell behaviors. These effects are overall in accordance with those reported previously. On the other hand, in the case that two different growth factors were co-displayed on a single spot, the behaviors of neural stem cells could not be simply predicted from their individual effects. We performed a multivariate cluster analysis for the quantitative data on cell proliferation and differentiation. It was shown that the effect of two growth factors co-displayed was competitive, synergistic, or destructive depending on the combinations. In other peculiar cases, the effect of growth factors was totally different from those of individual factors.