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E. A. Stewart, A. C. Browning, W. M. Amoaku; Human Choroidal Endothelial Cell Growth Factors and Signalling in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3433.
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Age-related macular degeneration (AMD) is the most common cause of irreversible visual loss in elderly populations in the western world. As the population ages, the number of people with AMD is expected to double by 2020, with marked economic implications. AMD is caused by choroidal neovascularisation (CNV) of human choroidal endothelial cells (hCEC); this is primarily thought to be stimulated by vascular endothelial growth factor (VEGF) isoform 165. However, the mechanisms and growth factors responsible for AMD are not fully understood as current treatments which block VEGF do not completely abrogate CNV, indicating that other growth factors or VEGF isoforms may be involved. In order to assist in the development of future treatments of AMD, further investigation is required into the intracellular mechanisms involved in the activation of hCECs.
hCEC were isolated, cultured and characterised as previously published by this laboratory (Br J Ophthalmol 2005 89:1343-7). hCEC proliferation was then measured after exposure to growth factors expressed in the eye including VEGF isoforms, FGF2, IGF-1, PDGF-BB and IL-1B using the WST-1 assay. The effect of these growth factors on angiogenesis was assessed using a double layer Matrigel technique. The significance of the effect of the natural inhibitor PEDF and current anti-angiogenic treatments was also assessed using these techniques. The specific intracellular signalling involved in the effects of these growth factors was then analysed by isolation of stimulated phosphotyrosine modified proteins and 2D gel electrophoresis.
A consistent pattern of stimulation was seen between growth factors in all experiments. Both VEGF isoforms and FGF2 stimulated significant increases in both proliferation and angiogenesis, whilst the other growth factors IGF-1, PDGF and IL-1B did not significantly increase either. PEDF appeared to have a phasic effect on the proliferation of hCEC in combination with VEGF isoforms. Specific proteins whose expression varied between growth factor signalling were identified.
Several growth factors and their isoforms may have potent roles in AMD and this complicates its treatment. The identification of the specific signalling pathways involved in growth factor stimulation will allow more specifically targeted treatments of AMD in the future.
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