To study the protective effect of icariin (ICA) on D-galactose (D-Gal) induced 15P-1 Sertoli cells injury via the Nrf2 signaling pathway.15P-1 cells were divided into control group,150 mM D-Gal group,D-Gal+ICA (0.5 μM) group and D-Gal+ICA (1.0 μM) group.The mRNA and protein expression levels of GDNF,BMP4 and SCF in 15P-1 cells were detected by RT-PCR and Western blot,respectively.The expression levels of tight junction related proteins Occludin and Claudin-1,Nrf2 signaling pathway proteins including Nrf2,HO-1 and NQO-1 in 15P-1 cells were detected by Western blot.The expression and localization of Nrf2 were detected by immunofluorescence.The mRNA and protein expression levels of GDNF,BMP4 and SCF in 15P-1 cells in D-Gal stimulated group were significantly decreased compared with the control group.On the contrary,ICA significantly increased the mRNA and protein expression levels of GDNF,BMP4 and SCF.In addition,the protein expression levels of Occludin,Claudin-1,Nrf2,HO-1,and NQO-1 in 15P-1 cells in D-Gal group were significantly decreased compared with the control group,while icariin significantly up-regulated the above related protein expression.The results of immunofluorescence further showed that ICA up-regulated the expression of Nrf2 in the nucleus of 15P-1 cells.ICA can alleviate the injury of 15P-1 Sertoli cells induced by D-Gal and improve its function,and its mechanism may be related to upregulation of Nrf2 signaling pathway proteins.