Endothelial nitric oxide synthase is expressed in amacrine cells of developing human retinas.
OBJECTIVE
To examine the expression and cellular distribution pattern of endothelial nitric oxide synthase (eNOS) in the developing human retina and to compare its expression with that in rats.


METHODS
Expression of eNOS was examined by immunohistochemistry in retinas of humans ranging from 8.5 to 28 weeks of gestation (WG) and of rats.


RESULTS
In the developing human retina, eNOS expression was first detected in the proximal margin of the neuroblastic layer in the incipient fovea-surrounding area at 12 WG. At 17 to 28 WG, eNOS-immunoreactive cells were located in the innermost part of the inner nuclear layer and in the ganglion cell layer, expanding to both temporal and nasal retinas and the processes projecting into the inner plexiform layer. These eNOS-positive cells coexpressed syntaxin and glutamate decarboxylase, and are probably GABAergic amacrine cells. The onset of eNOS expression in developing amacrine cells, however, preceded the invasion of retinal vasculature, long before vascular function involving these cells can be expected, suggesting that eNOS has a role not only in vasoregulation but also in retinal development. From 20 WG on, eNOS was also detected in the photoreceptors adjacent to the fovea. eNOS expression in amacrine cells and photoreceptors was observed in the central-to-peripheral and temporal-to-nasal gradients. However, in the developing rat retina, eNOS was expressed exclusively in the vascular endothelial cells.


CONCLUSIONS
The results support that eNOS plays a role, not only in the regulation of vascular function but also in the process of retinal development in humans.
Li
Shengxiu
S
Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Tay
David
D
Shu
Siyun
S
Bao
Xinmin
X
Wu
Yongming
Y
Wang
Xiaoyang
X
Yip
Henry K
HK
D025042:Amacrine Cells / Q000196:embryology* / Q000201:enzymology*; D000818:Animals; D019084:Fluorescent Antibody Technique, Indirect; D005865:Gestational Age; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D020419:Photoreceptor Cells, Vertebrate / Q000201:enzymology; D050765:Qa-SNARE Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000196:embryology
D019394:Ki-67 Antigen; D050765:Qa-SNARE Proteins; D052250:Nitric Oxide Synthase Type III; D005968:Glutamate Decarboxylase