Abstract
Purpose: :
Both the erythropoietin and its receptor are expressed in the retina, however, their cellular distribution and involvement in retinal development is not known. In the present study, we examined developing postnatal and adult rat retinas by specific antibodies with single and double labeling techniques in order to identify the temporal and spatial onset of their expression in the mammalian retina.
Methods: :
Retinas from Sprague-Dawley rats of different postnatal ages were analyzed by erythropoietin-, erythropoietin receptor-specific and cell type-specific antibodies and lectin cytochemistry.
Results: :
In the adult retina both the erythropoietin and its receptor were expressed in the photoreceptor inner segments, in the inner nuclear, ganglion, and both plexiform layers. Their expression patterns changed similarly during development. At birth, we found strong immunoreactivities in the ganglion cell layer and in the inner cell rows of the neuroblast layer and weak staining in the outer part of the neuroblast layer. During the following days the immunoreactivity of the ganglion cells and presumptive amacrine cells became more prominent. The cells of the ganglion cell layer showed a cytoplasmatic staining to the anti-erythropoietin antibody. From the second half of the first postnatal week strongly stained horizontal cells were observed by both antibodies at the level of the separating outer plexiform layer. During the second week a transient erythropoietin receptor expression was found in some cells of the outer nuclear layer, which followed a centroperipheral gradient. At the level of the developing photoreceptor inner and outer segments exclusively the inner segments were positively stained by both antibodies.
Conclusions: :
The erythropoietin is produced locally by the ganglion cells and its main targets are the amacrine, horizontal and photoreceptor cells. Since the erythropoietin exhibits neuroprotective and neurotrophic properties in neural tissue, it may act as a regulating factor during the retinal development.
Keywords: retinal development • neuroprotection • immunohistochemistry