Expressions of Olig1 and Nogo-A genes related to white matter injury after cerebral ischemia-reperfusion

Objective To investigate expressions of oligodendrocyte transcription factor 1 (Olig1) and neurite outgrowth inhibitor-A (Nogo-A) and white matter injury after focal cerebral ischemia in rats,and explore their relationship.Methods Sprague-Dawley male rats were subjected to middle cerebral artery occlusion for 2 hours.RQ-PCR was performed to examine the expression of Olig1 and Nogo-A in white matter at different reperfusion time points in both testing group and shame-operation control group.Myelin sheath was stained by LFB-PAS protocol,and axon was stained by Bielschowsky's silver stain.Integrated optical densities (IAs) in LFB-PAS staining in both hemispheres were measured,and the IAs ratio was calculated to represent the severity of the white matter damage.Results (1) The expreesion of Olig1 and Nogo-A:F=29.556 and 22.816 respectively.In the testing group,the expression levels of Olig1 and Nogo-A in the white matter began to decrease 6 h and 1 d post-reperfusion,respectively,to 83% and 84% of the levels in sham-operation group (q=2.074,P=0.042 and q=2.230,P=0.029 respectively),and both reached their lowest level at 7 d.They increased afterwards.At 14 d,Olig-1 reached the base level similar to the sham-operation group (q=0.625,P=0.534).At 21 d,Olig-1 and Nogo-A increased to 1.52 times and 66%,respectively,of those in sham-operation group (q=6.362,P ＜ 0.01 and q=4.681,P ＜ 0.01respectively).(2) LFB-PAS staining:F=122.181,myelin sheaths lost their LFB-PAS staining and IAs ratio decreased at 6 h after ischemia-reperfusion (0.91±0.05,q=3.829,P ＜0.01 vs sham-operatian group).Vacuoles appeared separating myelin sheaths at 12 h.The IAs ratio decreased gradually and reached its lowest point at 14 d (0.31±0.07).There was no significant difference in IAs ratio between 14 and 21 d (q=0.257,P=0.798).The change in axons was similar to that in Myelin sheaths.Conclusions The Olig1 and Nogo-A expression show biphasic change in time-lapse study and the changes by time are in accordance with the pattern in pathologic findings in the white matter by LFB and Bielschowsky' s silver staining.Olig1 and Nogo-A might participate in the pathogenesis of cerebral white matter lesion and plasticity. Key words: Brain ischemia; Reperfusion injury; Nerve tissue proteins; Basic helix-loop-helix transcription factors; Myelin proteins