miR-21 regulates astrogliosis through the Akt/mTOR signaling pathway. To determine the effects of miR-21 in the regulation of proliferation and apoptosis in vivo, expression of miR-21 was interrupted in a SCI mouse model. Mice were divided into four groups: sham, agomir-21, antagomir-21 and NC. (A) p-AKT, AKT, p-mTOR, Bax and Bcl2 were detected by Western blot and analyzed by ImageJ and SPSS (B-D). (E) the expression of Ki-67 was detected by immunohistochemistry (scale bar: low magnification, 100μm; high magnification, 20μm) and analyzed by ImageJ and SPSS. (G). (F) TUNEL assay (scale bar: low magnification, 100μm; high magnification, 20μm) was performed and analyzed by ImageJ and SPSS (H). Data are expressed as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 compared with the NC group. miR, microRNA; NGF, nerve growth factor; NC, negative control; SCI, spinal cord injury.