[Monitoring retrograde adenoviral transgene expression in spinal cord and anterograde labeling of the peripheral nerves].

OBJECTIVE: Targeted adenoviral gene delivery from peripheral nerves was used to integrally analyse the characterization and time course of LacZ gene (AdLacZ) retrograde transfer to spinal cord and transgene product anterograde labeling of peripheral nerve.

METHODS: Recombinant replication-defective adenovirus containing AdLacZ was administrated to the cut proximal stumps of median and tibial nerves in Wistar rats. Then the transected nerve was repaired with 10-0 nylon sutures. At different time point post-infection the spinal cords of C5 to T1 attached with DRGs and brachial plexuses, or L2 to L6 attached with DRGs and lumbosacral plexuses were removed. The removed spinal cord and DRCs were cut into 50 microm serial coronal sections and processed for X-gal staining and immunohistochemical staining. The whole specimens of brachial or lumbosacral plexuses attaching with their peripheral nerves were processed for X-gal staining. The number of X-gal stained neurons was counted and the initial detected time of retrograde labeling, peak time and persisting period of gene expression in DRG sensory neurons, spinal cord motor neurons and peripheral nerves were studied.

RESULTS: The gene transfer was specifically targeted to the particular segments of spinal cord and DRGs, and transgene expression was strictly unilaterally corresponding to the infected nerves. Within the same nerve models, the initial detected time of gene expression was earliest in DRG neurons, then in the motor neurons and latest in peripheral nerves. The persisting duration of beta-gal staining was shortest in motor neurons, then in sensory neurons and longest in peripheral nerves. The initial detected time of beta-gal staining in median nerve models was earlier in median nerve models compared with that in the tibial nerve models. Although the initial detected time and the beginning of peak duration of beta-gal staining were not same, the decreasing time of beta-gal staining in motor and sensory neurons of the two nerve models were started at about the same day 8 post-infection. The labeled neurons were more in tibial nerve models than that in median nerve models. Within the same models, the labeled sensory neurons of DRGs were more than labeled motor neurons of ventral horn. The beta-gal staining was tender in median nerves than that in tibial nerves. However the persisting time of beta-gal staining was longer in tibial nerve models.

CONCLUSION: The strong gene expression in neurons and PNS renders this system particularly attractive for neuroanatomical tracing studies. Furthermore this gene delivery method allowing specific targeting of motor and sensory neurons without damaging the spinal cord might offer potentialities for the gene therapy of peripheral nerve injury.