Wild Type Mice Intravitreally Injected With Low Dose Triamcinolone and NOS II KO Mice Present Similar Chorio–Retinal Remodelling After Laser Photocoagulation

Abstract

Abstract: : Purpose: Compare the influence of the NOS II gene loss and intravitreous injection (IVT) of Triamcinolone (TM) on the retinal wound healing and blood vessel remodelling processes following laser photocogulation of the mouse eye. METHODS: Wild type C57BL/6J mice (WT) and NOS II knock out (KO) mice, 6 to 8 weeks old underwent a standard photocoagulation (50um spot size, 0.05’’, 400mW). One single lesion (one to two disc diameters nasal to the papillae) was induced OU in WT and KO mice. 3 groups were studied: Group I, WT mice, had only photocoagulation. Group II, WT mice, received an IVT of 1µl containing 5µg TM after photocoagulation. Group III, NOS II KO mice, had only photocoagulation. Two mice from each group were sacrificed every 3 to 4 days during a period of 3 weeks after photocoagulation. One eye of each mouse was snap frozen, cryopreserved in OCT and processed for immunohistochemical analysis (GFAP and von–Willebrand factor receptors and F4/80). TUNEL reaction and DAPI staining were also carried out. The second eye was preserved in 4% PFA for conventional histology. Sections through the entire laser lesion were collected and stained. At different time points, thorough systematic analysis of the cellular remodelling processes within the lesion and its vicinity were carried out. Results:The DAPI staining and histology demonstrated that early after laser treatment, a gradual posterior evagination of the retinal inner and outer nuclear layers towards the choroid takes place feeling the void created within the choroid by the laser burn. The GFAP positive cells (Muller’s and glia) activation which followed the photocoagulation were similar in all three groups. The remodelling behaviour of the retinal and choroidal vessels were identical in Groups II and III with a more accentuated vascular activation of the choroidal vessels at the edges of the photocoagulation lesion in Group I. An increase in the number of apoptotic cells within the retinal external nuclear layer was observed in Groups I and III while an abolition of the infiltrating macrophages was observed in Group II. Conclusions: Deficiency of the NOS II gene expression or TM IVT appear to have the same influence on the retinal and choroidal remodellind processes following laser photocoagulation in WT mice.

Keywords: neovascularization • laser • corticosteroids