Trafficking of intracerebroventricularly injected antisense oligonucleotides in the mouse brain

Intracerebroventricular (icv) delivery of therapeutic molecules directly into the brain parenchyma has attracted considerable attention because of the advantage of bypassing the blood-brain barrier. Exogenous icv administration of antisense oligodeoxynucleotides (AS-ODNs) has been implicated in modifying gene expression within the targeted brain area. The biodistribution, tissue penetration, and stability of exogenously administered AS-ODNs are the major determinants with regard to their potential utility as agents for modifying gene expression. This report examined the distribution and clearance of labeled AS-ODNs with the aim of exploring the feasibility of icv administration of AS-ODNs as a targeted treatment approach to Alzheimer's disease. A single icv injection of fluorescein-labeled 2'-O-(methoxy) ethyl (2'MOE) ribosyl-modified AS-ODNs directed at the beta-secretase cleavage site of beta-amyloid precursor protein (APP) mRNA into the mouse brain showed rapid uptake by 15 minutes, overall gradual spread and retention by 30 minutes to 3 hours, and complete clearance by 8 hours postinjection. Labeled AS-ODNs were observed to penetrate across the cell membrane and accumulate in both nuclear and cytoplasmic compartments of neuronal and nonneuronal cell populations. Current study provides a basic pattern of uptake, distribution, and stability of AS-ODNs in the mouse brain.