M2 upregulated SIRT2 expression in the EpSCs through BDNF-TrkB signaling. (a) The secretion of BDNF in different macrophage conditioned media was detected by ELISAs. The BDNF protein in the M2 conditioned medium was significantly higher than that in the M1 or M0 conditioned medium. (b) The expression of TrkB receptor in the EpSCs was observed by immunofluorescence staining, which was mainly located on the surface of cell bodies, axons and dendrites. (c) Representative immunoreactive bands of p-TrkB and TrkB in the EpSCs cocultured with M2 derived from the WT or BDNF^-/- mice. The p-TrkB expression in the EpSCs was significantly induced when cocultured with M2 from the WT mice but had no change when cocultured with M2 from the BDNF^-/- mice. RT-PCR (d) and western blot assays (e) were used to detect SIRT2 expression in the EpSCs of different groups. The EpSCs cocultured with M2 from the BDNF^-/- mice showed decreased SIRT2 expression. Data represent three independent experiments. *p<0.05, **p<0.01, ***p<0.001.