GDNF and Parkinson disease: Since the survival and differentiation rate of BM-MSCs in vivo is relatively low, neurotrophic factors, such as glial cell line-derived neurotrophic factor (GDNF) family ligand persephin was used to increase the survival rate of transplanted BM-MSCs, enhance the differentiation of cells into neuron- and glial-like cells, increase the content of DA in striatum, and ultimately improve the rotational behavior of PD rats [27].