Reducing Apoptosis in the Ischemic Retina Using Hyperbaric Oxygen Treatment in Two Different Mouse Models

Abstract

Methods: : Mice underwent CRAO (n=40) or crush induction (n=40); 20 of each group underwent HBO treatment. CRAO was induced by laser activation after rose-Bengal administration intravenously. Crush injury was induced by compressing the optic nerve posterior to the globe. Mice treated by HBO were exposed to 100% oxygen, in 2 atm for 90 minutes immediately after induction, and daily thereafter for up to 14 days. Histological sections of the retina were examined for apoptosis; mRNA expression levels of Bax, Bcl-2, and Caspase-3 were analyzed using quantitative real-time PCR, in the treated and untreated induced ischemic retinae.

Results: : Maximal retinal cell loss of the inner retinal layers on day 21 were 60% and 80% in the CRAO and crush injury respectively. In the HBO treated groups, cell loss was only 30% and 40% respectively. Molecular analysis revealed an increase of Bax (X4), Caspase 3 (X2) and Bcl-2 (X1.5) on day 1 in crush models, but not in the HBO treated mice. On day 3 all levels reverted to baseline (Caspase 3, Bax) or lower (Bcl-2 0.67), similar to the levels measured in the HBO treated mice. CRAO showed similar trends, with 2-fold increase in the Bcl-2 level on day 3 in the HBO treated group.

Conclusions: : HBO-treatment protects neuronal cells from apoptosis. Histologically and molecularly we demonstrated reduced apoptosis and tissue preservation. These results encourage further clinical trials in patients with ischemic neuronal damage.

Keywords: apoptosis/cell death • ischemia • retina