Abstract
Purpose:
Several vertebrate species have been shown to be able to change the rate of axial eye growth, as well as of choroidal thickness to compensate for retinal image defocus. Hyperopic defocus induces choroidal thinning in vivo. Vascular Endothelial Growth Factor A (VEGFA) was suggested as one of the signals that induce choroidal thinning in vitro (Sheng et al., 2012). The concentration of Vascular Endothelial Growth Factor A (VEGFA) in the aqueous of highly myopic patients was found to be lower than in emmetropes (Shin, Nam et al., 2012), but the time courses of the changes in VEGFA during myopia development is not known. We are planning to study the role of VEGF in the chicken model but first it is necessary to describe the expression of the different members of the VEGFs and their receptors in the fundal layers of the chick eye.
Methods:
Eyes from 3 weeks old chicks (n = 5) were hemisected and the retinas, retinal pigment epithelium and choroid were carefully dissected. Semi-quantitative real-time PCR was used to quantify mRNA level of VEGFA (transcript variant 1 and 2), VEGFC, VEGFD, VEGFR1, VEGFR2 and VEGFR3 in the fundal layers using beta-actin as reference gene. PCR products were verified by automated sequencing.
Results:
In animals with normal visual exposure, VEGFA, VEGFC, VEGFD, VEGFR1, VEGFR2 and VEGFR3 mRNA were expressed in retina, retinal pigment epithelium and choroid, although the mean normalised expression of VEGFR1 was very low in all tissues. VEGFR3 mRNA expression was significantly higher in the choroid compared to retina and RPE (ANOVA, p < 0.05).
Conclusions:
This study shows that the mRNA of VEGF and VEGF family receptors is expressed in the avascular retina of the chicken, as well as retinal pigment epithelium and choroid. Furthermore, quantification of its abundance is possible. Therefore, the regulation of the VEGF signaling system can now be studied during myopia development and pharmacological treatment.
Keywords: 605 myopia •
748 vascular endothelial growth factor •
452 choroid