Objective: The mechanism of remote viral gene delivery to the spinal cord is unknown. The present experiment demonstrates that intraneural injection of colchicine is capable of inhibiting remote delivery of both adenoviral and adeno-associated viral (AAV) vectors, implicating axonal transport in this process.
Methods: The right sciatic nerves of adult Sprague-Dawley rats were injected with phosphate-buffered saline (PBS) (n = 5) or 10 (n = 7) or 100 (n = 4) microg colchicine. Two days later, the nerves of all animals were initially injected with 1.2 x 10(7) plaque-forming units of Ad5RSVntLac-Z. Two separate groups were injected concurrently with vector and PBS (n = 5) or 10 microg colchicine (n = 5). In a second experiment, the right sciatic nerves of CD1 mice were preinjected with PBS (n = 6) or 10 microg colchicine (n = 5). Two days later, the nerves were injected with rAAVCAG-EGFPwpre (an adeno-associated vector carrying the green fluorescent protein gene). In both experiments, sciatic nerves and spinal cords were removed and analyzed for gene expression.
Results: Sciatic nerve vector injection resulted in expression in both the nerve injection site and neuronal cell bodies located predominantly in the ipsilateral ventral horn. Analysis of variance revealed a significant treatment effect for 10 and 100 microg intraneural colchicine with inhibition of remote adenoviral delivery at 10 microg and blockade of remote delivery at 100 microg (P < 0.001). Colchicine injection concurrent with and before vector injection had similar inhibitory effects. Two-way analysis of variance revealed significant colchicine inhibition of remote delivery in both adenovirus- and AAV-injected animals (P < 0.003) but no dose-by-vector interaction, suggesting that both vectors are equally inhibited by colchicine.
Conclusion: Colchicine inhibits remote spinal cord delivery of adeno-associated and adenoviral vectors in a dose-dependent manner, suggesting that remote delivery is dependent on retrograde axonal transport.