Systemic low-molecular weight drug delivery to pre-selected neuronal regions.
Bottom Line: We describe a procedure for controlled, periodic, reversible modulation of selected regions of the blood-brain barrier (BBB) or the inner-blood-retina barrier (iBRB) based on incorporation into an AAV-2/9 vector of a doxycycline-inducible gene encoding shRNA targeting claudin-5, one of 30 or so proteins constituting the BBB and iBRB.The vector may be introduced stereotaxically into pre-selected regions of the brain or into the retina, rendering these regions permeable to low-molecular weight compounds up to approximately 1 kDa for the period of time during which the inducing agent, doxycycline, is administered in drinking water, but excluding potentially toxic higher molecular weight materials.We report on the use of barrier modulation in tandem with systemic drug therapy to prevent retinal degeneration and to suppress laser-induced choroidal neovascularization (CNV), the latter being the hallmark pathology associated with the exudative, or wet, form of age-related macular degeneration (AMD).
Affiliation: Ocular Genetics Unit, Department of Genetics, Trinity College Dublin, Dublin 2, Ireland. email@example.comShow MeSH
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Mentions: Systemic administration of CLDN5 AAV caused a phenotype similar to that observed at the iBRB, and as expected also manifested in increased permeability of Gd-DTPA across the BBB correlated with suppression of brain capillary claudin-5 (Supplementary Fig 4). Moreover, a stereotaxic inoculation of 2 µl of the CLDN5 AAV-2/9 (5 × 1011 vp/ml) in the region of the right hippocampus showed a localized and inducible BBB modulation site-specifically when mice were supplemented with doxycycline (2 mg/ml) in their drinking water. This localized modulation of the BBB caused enhanced passive diffusion of Gd-DTPA from the blood to the brain while causing no signs of oedema formation. Specifically, dark contrasting observed in the right hippocampus of Fig 3E was manifested as intensely high-contrast blue in the pseudo-coloured image of Fig 3F. Each of nine individual mice injected had significantly higher Gd-DTPA contrasting in their right hippocampus compared to the left (Supplementary Fig 5). Importantly, the inducibility of the barrier modulating system was highlighted when doxycycline was removed from the drinking water and no barrier permeability was observed (Supplementary Fig 6).
Affiliation: Ocular Genetics Unit, Department of Genetics, Trinity College Dublin, Dublin 2, Ireland. firstname.lastname@example.org