Abstract
Introduction: :
Studies have shown that cones degenerate in chromophore-deficient mouse models for Leber Congenital Amaurosis (LCA), but exogenous supplementation of the native 11-cis retinal chromophore can inhibit this degeneration, suggesting that 11-cis retinal could be used as a therapeutic agent for preserving functional cones in patients with LCA. However, the treated mice were maintained in the dark.
Purpose: :
To determine the effect of light/dark cycles on the cones of 11-cis retinal-treated Rho-/-Rpe65-/- mice.
Methods: :
11-cis Retinal was introduced into Rho-/-Rpe65-/- mice at P10 as a single subcutaneous injection mixed with Matrigel. The mice were maintained in either normal cyclic light/dark or constant dark conditions. Cone function was determined by electroretinography (ERG), and morphology assessed by fluorescence microscopy. Cross sections at P21 were used to visualize cone opsin localization, and flat-mounted retinas used to determine the number of cone opsin-containing cells at P25 and P30.
Results: :
As expected, the 11-cis retinal-treated mice raised in constant dark shows improved cone ERG signals, improved cone opsin localization and increased cone photoreceptor cell number when compared with untreated mice. However, 11-cis retinal-treated mice raised in cyclic light did not show any of the improvements seen with the dark-reared mice.
Conclusions: :
Thus, 11-cis retinal by itself will not be a good therapeutic candidate for preserving cones in LCA due to the need for total darkness following treatment.
Keywords: color pigments and opsins • retinoids/retinoid binding proteins • retinal degenerations: cell biology