The Investigation Of Apoptosis Of DRG In Non-freezing Cold Injury Of The Sciatic Nerve In The Rat

Objective:To detect the apoptosis of sensory neurons in dorsal root ganglion(DRG) following non-freezing cold injury of the rat's sciatic nerve,we counted the apoptotic neurons and observed their morphology changes of sensory neurons in L4-6 DRGs in focal cooling injury of rat's sciatic nerves.Methods:66 male Wistar rats were randomly divided into two groups,each consisted of 33 rats.The sciatic nerves were cooled to 4℃for 2 hours.The control group accepted sham operation.The pathological examination of L4-6 DRGs(7d,14d,and 21d post operation) was performed.The apoptotic sensory neurons of L4-6 DRGs were counted using FCM(Annexin/PI) and their morphology changes were observed by TUNEL staining.In order to ensure the reliability and reproducibility of the results, the measurements were repeated twice using different biologic samples.Results:1.The sensory neurons of L4-6 DRGs were proved to have apoptosis after non-freezing cold injury of the rat's sciatic nerve.2.FCM(Annexin/PI) quantitative analysis indicate that the neurons' apoptosis rate of(7d,14d,and 21d post operation) increased compared to the control with statistical significance(P＜0.05),while the neurons' death rate did not show any statistical difference.3.TUNEL qualitative analysis discovered hallmark pathological characters of neuron apoptosis in L4-6 DRGs(7d,14d,and 21d post operation),which were recognized as earlier period apoptosis cells.4.TUNEL quantitative analysis showed the apoptosis rate of the sensory neurons in L4-6 DRGs increased compared to the control with statistical significance(P＜0.05).The apoptosis rate increased on 7d post operation,and reached a peak on the 14d and then decreased slightly on the 21d. Conclusion:Non-freezing cold injure on sciatic nerves caused the sensory neurons' apoptosis of L4-L6 DRGs.The apoptosis peak appeared on the 14 day after non-freezing cold injure,and the neurons were in early apoptotic state.