Abstract
Abstract: :
Purpose: The perifoveal region of primate retina is the last to be vascularized and the fovea remains avascular. In this study we investigate VEGF expression associated with formation of the perifoveal capillary plexus (PFC). Method: We used paraffin embedded fetal human (14 to 20 weeks gestation, WG) and monkey retinae (foetal day, Fd 85 - 4 months postnatal) fixed in Methyl Carnoy solution and sectioned in the horizontal plane. DIG-labelled riboprobes were prepared from human VEGF cDNA, hybridized in situ and detected using anti-DIG antibody with Fast Red Alkaline Phosphatase kit (Roche), then double labeled using antibody to vimentin and imaged by confocal microscopy. Results: VEGF mRNA was detected in the optic nerve head of human retina at 14 WG and astrocytes in the nerve fibre layer associated with the developing primary vasculature at prenatal ages in both species. VEGF mRNA was detected at low levels in the ganglion cell layer (GCL) of central retina at Fd 85 and in cells associated with vessels forming at the GCL/inner plexiform layer (IPL) interface which contribute to the PFC. At Fd95, VEGF mRNA expression was strong in the GCL of the incipient fovea but was reduced by Fd 105, when the PFC were established. Between Fd 130 and 152 VEGF mRNA was seen in the inner nuclear layer, associated with development of the deep plexus. Conclusion: VEGF expression in the GCL of the incipient fovea may induce growth of capillaries towards the fovea. Expression of VEGF in the GCL at the incipient fovea suggests (1) that the GCL is transiently hypoxic during development and (2) that vacularization of the incipent fovea is inhibited by unidentified anti-angiogenic factors.
Keywords: 564 retinal development • 423 growth factors/growth factor receptors