Behaviour of CD11b-Positive Cells in an Animal Model of Laser-Induced Choroidal Neovascularisation

Abstract

Background/Aim: Immune cells, e.g. microglial cells of the retina, appear to be involved in pathological processes in neovascular age-related macular degeneration. Therefore, the purpose of this study was to immunohistochemically check the expression of various factors and cytokines by CD11b-positive (CD11b+) immune cells in an animal model of choroidal neovascularisation (CNV). Methods: We used the animal model of laser-induced CNV in mice. Eyes were isolated at 1, 4, 7, and 14 days after laser treatment. Cryosections were prepared and checked immunohistochemically for the presence of different growth factors and cytokines on microglial cells and other immune cells identified by CD11b immunoreactivity. Results: We found that the number of CD11b+ cells at the laser spots increased dramatically 4 days after laser treatment, the majority of them entering the laser spot most probably by migration. CD11b+ cells in the laser spot were positive for a variety of pro-angiogenic factors, such as PDGF-β, FGF-1, FGF-2, and TGF-β₁. They were also positive for some inflammatory cytokines, in particular TNF-α, IL-6, and CXCL1. In non-treated retinas, CD11b+ cells showed almost no immunoreactivity for these proteins. Conclusion: Microglial cells, macrophages, and other CD11b+ cells may promote the neovascularisation in the laser spot and show a moderate inflammatory behaviour. Immunoreactivity for most of these molecules was found to decrease during the time of observation. Modulation of immune cell activity may thus be a tool to reduce the extent of CNV.

Cytokine Profiling in Patients With Exudative Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy

“…25 It is secreted by RPE and Müller cells in a light-induced retinal degeneration model in rats 26 and is also upregulated in a model of laserinduced CNV in mice. 27 Deregulation of neutrophils plays a key role in the pathogenesis of in CNV-AMD, which is characterized by inflammation and angiogenesis. 28 Direct comparisons of aqueous humor GRO levels between CNV-AMD/PCV patients and controls were reported previously, but the results are inconsistent among datasets.…”

The Role of Microglia in Diabetic Retinopathy: Inflammation, Microvasculature Defects and Neurodegeneration

“…Angiogenesis and inflammation are not independent, but rather two interacting processes which share several mediators (e.g., VEGF) and signaling pathways. Thus, microglia might induce neovascularization by releasing pro-angiogenic mediators, including cytokines, growth factors and proteases [ 272 , 273 ]. Cytokines could directly or indirectly enhance vascular growth in endothelial cells [ 274 , 275 , 276 ].…”

“…Following photocoagulation, morphological changes from ramified to amoeboid microglia occurred and these microglia migrated into the outer nuclear layer and to the laser-induced injury [ 272 , 291 , 292 ]. Activation and infiltration into the outer nuclear layer started 6 h after light induction, but the number of amoeboid microglia declined 7 days after light exposure and the cells were then present mostly in the sub-retinal space [ 293 ].…”

“…Microglia activation peaked parallel to the apoptotic loss of cells 1 day after injury [ 293 ]. Expression of chemokines, pro-angiogenic mediators and inflammatory cytokines increased after laser-induced injury [ 272 , 293 ].…”

Association of CD11b+Monocytes and Anti–Vascular Endothelial Growth Factor Injections in Treatment of Neovascular Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy

“…Important findings include the immunohistochemical documentation of CD11b in areas of experimentally induced CNV and expression by CD11b + cells of VEGF and other proangiogenic factors. 22 CD11b is an integrin expressed on the surface of myeloid cells and facilitates cell adhesion and migration, especially at sites of inflammation. CD11b is also part of complement receptor 3.…”