Correlations Of Sdf-1 And Cxcr4 Levels With Caspase-3 Expression In The Retina Of Rats After Optic Nerve Injury

Objective: This study explores the correlations of stromal cell-derived factor-1 (SDF-1) and CXC chemo-kine receptor 4 (CXCR4) levels with caspase-3 expression in the retina of rats after optic nerve injury. Materials and methods: A total of 24 adult healthy specific pathogen-free Sprague-Dawley rats were selected and randomly divided into an optic nerve injury group (n=16) and an optic nerve sham-injury group (n=8). The optic nerve injury group was further sub-divided into a 3 d group (n=8) and a 7 d group (n=8) after their injuries. In the optic nerve in-jury group, the left eye of each rat was removed and prepared for the optic nerve injury model using the optic nerve clamping method. In the sham-injury group, the optic nerve in the left eye was only exposed without being clamped. The rats were sacrificed at 3 d and 7 d after their optic nerve injuries, and the retina was isolated. The expressions of SDF-1, CXCR4, and caspase-3 in the retina of the rats in each group were measured using an immunohistochemical method. Messenger ribonucleic acid (mRNA) and the protein expressions of SDF-1, CXCR4, and caspase-3 (cleaved caspase-3) in the retinas of rats were measured using quantitative real-time polymerase chain reaction (qPCR) and western blotting, respectively. Moreover, the correlations of the expression of SDF-1 and CXCR4 with caspase-3 expression were analyzed using the Spearman method. The apoptosis of retinal ganglion cells of rats in each group was observed using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. Re-sults: Immunohistochemistry of the retinas revealed that, compared with those in the sham-injury group, the expres-sions of SDF-1 and CXCR4 in the retina in the 3 d group and the 7 d group were gradually increased. Caspase-3 expression was significantly elevated at 3 d after the injuries, but obviously decreased at 7 d after the injuries. The results of qPCR showed that the relative expression levels of SDF-1 and CXCR4 mRNA in the retina at 3 d and 7 d after optic nerve injuries were also significantly higher than those in the sham-injury group (P<0.01), and the caspase-3 mRNA expression was initially increased at 3 d but reduced at 7 d after the injuries (P<0.01). Western blotting for the detection of the SDF-1, CXCR4 and caspase-3 proteins indicated changes similar to those of the qPCR. Spearman analysis results demonstrated that there was a positive correlation between the SDF-1 and CXCR4 expressions, but the expressions of SDF-1 and CXCR4 had negative correlations with caspase-3 expression. TUNEL staining showed that apoptosis of the retinal cells was increased in the 3 d group but significantly decreased in the 7 d group. Conclusion: After optic nerve injury, the continuous increase of the SDF-1 and CXCR4 levels suppresses the apoptosis of retinal cells and repairs the retina by inhibiting the cleavage activation of caspase-3. This provides new insights for the ongoing treatment of optic nerve injury.