RTN4 and proliferative diabetic retinopathy: In addition, RTN4 is necessary for the migration and contraction of airway smooth muscle cells in airway remodeling in chronic asthma (Xu et al., 2011), promoting angiogenesis in proliferative diabetic retinopathy via the PI3K/Akt signal pathway (Zhang et al., 2017), and facilitating EMT in non-small cell lung cancer (Wu et al., 2018).