To investigate whether light stimulation of ChETA-transfected astrocytes could upregulate bFGF level in vivo to enhance the differentiation of stem cells, ChETA-transfected astrocytes along with neural progenitors derived from human ESCs were prepared, and co-transplanted into the SN of the MPTP-mouse model of PD (Fig. 4a,b, Supplementary Fig. 4a). This evidence concerns the gene FGF2 and Parkinson disease.