GDNF and ischemic stroke: M2 type microglia has anti-inflammatory effect, it can secrete anti-inflammatory medium and neurotrophic factor such as IL-10, IL-13, TGF-beta, glial cells derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), which promote tissue repair and neuron regeneration in ischemic stroke [55].