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A.E. Hendrickson, D. Possin, H. Djajadi; Human Retinal Development in the Absence of Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):563.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Anencephaly is the failure of the forebrain to develop. The visual thalamus undergoes retrograde degeneration which in turn causes transsynaptic degeneration of retinal ganglion cells (GC). Retinas were examined from anencephalic (AnC) fetuses and neonatal infants to determine what effect GC loss has on retinal circuit and foveal formation. Methods: One midgestation and two neonatal human AnC retinas were fixed and processed for serial sectioning. Immunocytochemical labeling for synaptic, cytoplasmic, photoreceptor and neurotransmitter markers was performed on sections from AnC and normal age–matched controls. Results: In the AnC and normal fetal retinas, photoreceptor opsins were expressed in a similar pattern and photoreceptors had the same morphology. In both retinas, bipolar cells (BP) labeled for Goa, PKC, recoverin and glutamate vesicular transporter and the same was true for amacrine (AM) markers calretinin, calbindin, GABA and glycine. BP and AM terminals had the same distribution in the inner plexiform layer (IPL). In both fetal and neonatal AnC retinas, the IPL was only 20% as thick as the normal, and GC appeared absent with only a very few cell bodies or axons showing Brn3 or neurofilament labeling. There was no obvious loss of cells in the inner nuclear layer in either the fetal or neonatal AnC retinas. In the AnC neonates, blood vessels were present in central retina and may have invaded the foveal region. There was no sign of a foveal pit but the foveal region still contained a pure cone area. Foveal cones were elongated and had fibers of Henle, suggesting that some cone packing had occurred before birth. Conclusions: The loss of visual cortex induces a rapid retrograde transynaptic degeneration of the GC with only a few surviving by midgestation. This degeneration does not spread into the BP and AM cells, but does result in a very thin IPL. The AnC IPL retained a correct lamination based on BP and AM markers. The failure of pit formation could be due to encroaching blood vessels and/or death of GC. Morphological evidence suggests that foveal cones had undergone some packing, despite the lack of a foveal pit.
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