Abstract
Purpose :
Neovascular AMD is treated by intravitreal injections of anti-VEGF drugs, such as aflibercept. Unfortunately, some neovascularisations are resistant towards this treatment. Microglia (MG) as the resident immune cells play a crucial role in the development of AMD. However, the effect of anti-VEGF injections on MG is not yet known. This project aims to understand the effects of anti-VEGF medication on microglial cells by using the experimental model of laser-induced CNV in mice.
Methods :
55 mice were randomly divided into 3 groups. All mice received laser treatment. The first group of animals was not further treated after laser treatment, whereas groups 2 and 3 received intravitreal injections of aflibercept or PBS, respectively, immediately after laser treatment. The development of the laser spots was monitored by in vivo imaging (optical coherence tomography, fluorescence angiography, scanning laser ophthalmoscopy) as well as by immunohistochemical staining of choroidal flat mounts. Immunohistochemical staining of retinal cryosections was performed for VEGFR1, VEGFR2, CD14, IL-6 and CXCL-1, and co-localisation for the MG stained for Iba-1 was checked.
Results :
In vivo imaging revealed a decreased size of the laser spots and a significantly decreased size of the leakage in the anti-VEGF group compared to the PBS injection and control groups. Immunohistochemical staining of the flat mounts showed a decreased migration of retinal MG into the laser spots after anti-VEGF injection. In all groups, most of Iba1 positive cells were also positive for CD14. On days 4 and 7, portion of Iba1 positive cells that were also positive for VEGFR1 was slightly increased in the aflibercept group. Portion of Iba1 positive cells that were also positive for VEGFR2 was decreased in the aflibercept group. Immunoreactivity (IR) for CXCL-1 and IL-6 decreased after intravitreal injection of aflibercept.
Conclusions :
Intravitreally applied aflibercept inhibited action of MG in our experimental CNV model. We saw a decreased IR for the VEGFR2 and the proinflammatory cytokines CXCL-1 and IL-6. It may be hypothesised that these changes contributed to the reduction of MG migration into the laser spot and of the size of the CNV we found after intravitreal injection of aflibercept. Increased VEGFR1 levels might be interpreted as a kind of compensation mechanism due to binding of aflibercept to VEGF.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.