Bcl-2转基因小鼠视神经再生轴突长期存活的研究

Long time survival of the regenerated optic nerve axons in Bcl-2 transgenic mice

目的探讨出生3d的Bcl-2转基因小鼠视神经损伤后再生的神经轴突是否能够存活至成年并恢复功能。方法实验研究。出生3d的C5781／6J小鼠和Bcl-2转基因小鼠行视神经夹闭损伤手术，建立视神经损伤再生模型，夹闭后立刻向玻璃体腔内注射顺行性神经轴突标记物CTB-F标记再生的神经轴突，分别在手术后4、8、10、13、18和24d处死小鼠，做视神经和脑组织冰冻切片，行组织学染色和GAP-43免疫荧光染色，观察视神经轴突的再生。同样方法在小鼠视神经损伤后分别立刻玻璃体腔内注射MK801、视上丘放置NMDA或BDNF，术后10d和13d时进行视神经再生分析。结果在损伤后第4天视神经再生的轴突长人脑内的靶组织，维持到10d左右，10d后逐渐回缩；加入MK801、NMDA或BDNF，能够使再生轴突在脑内存活时间延长3d左右，13d后也逐渐回缩。结论出生3d的Bcl-2转基因小鼠视神经损伤后成功再生长人脑内靶组织，但再生的神经轴突在脑内存活10d后逐渐回缩，可能与不能建立突触连接有关。

Objective To study if the regenerating axons can be alive till adult and restore function when the optic nerve was crushed at 3 days after birth （P3） in Bcl-2 transgenic mice. Methods It was a experimental study. Optic nerve crush was performed on C57B1/6J and Bcl-2 transgenic mice at P3, immediately followed by intro vitreous injection of a nerve axon tracer--cholera toxin B subunit conjugated with fluorescein （CTB-F）. Mice were sacrificed at day 4, 8, 10, 13, 18 and 24 post operation, the optic nerve and the brain was cryosectioned. Immunofluerescence staining of GAP-43 was carried out to evaluate the regenerating axon. Same procedure was used together with immediately MK801 intro vitreous injection, gel foam soaked with NMDA or BDNF put in superior colliculus. Mice were sacrificed on 10 or 13 days post operation. Optic nerve regeneration was evaluated. Results The regenerated optic nerve axons reached the targets in the brain at 4 days post operation. But after 10 days, the regenerated axons were retracted. MK801, NMDA and BDNF can prolonged the alive of regenerated axons in the brain targets, but its alive was only lasted 3 more days. It retracted finally on 13 days after surgery. Conclusion Optic nerve can regenerate successfully to reach the targets in the brain when it was crushed on P3 in Bcl-2 transgenic mice, but the regenerated nerve axons can only survive for 10 days when it is retracted from the brain. It is probably because of the failure of the synapse formation at this time.