Abstract
Purpose: :
To compare the localization of prostaglandin E EP2 receptor subtypes in normal human, primate, dog and rabbit ocular tissues.
Methods: :
Paraffin-embedded sections from 5 normal human donor eyes, and 5 primate, 9 canine and 6 rabbit eyes were processed for immunohistochemistry with EP2-specific antibodies and subsequently incubated with Alexa Fluor 568 secondary antibodies to detect the presence of EP2 receptors. Fluorescence of the localized antibodies was visualized using the Hamamatsu Nanozoomer and the LSM710 Confocal microscope, and fluorescence intensities/unit of area were calculated and compared for various structures with Metamorph Pro.
Results: :
In the anterior segment of the eye, EP2 receptor expression was localized to the corneal epithelium and endothelium, trabecular meshwork, cilliary epithelium and endothelium, ciliary muscle, iris and the episcleral vasculature in all species studied. In the posterior segment of the eye, EP2 receptor labeling was prominent in the retinal, choroidal and scleral vasculature. EP2 was also localized to the neural retina in a subset of retinal ganglion cells, Muller cells and a subset of neurons in the inner plexiform layer. Interspecies EP2 expression was mostly comparable. One notable difference was the significantly lower expression of EP2 receptors in the rabbit trabecular meshwork and ciliary muscle.
Conclusions: :
These immunohistochemical results present evidence that the EP2 receptor is abundantly expressed mammalian ocular tissues with minor interspecies differences. Thus, primate, dog and ,to a lesser extent, rabbit make appropriate animal models for studying the ocular pathophysiological roles of EP2 receptor agonists relevant to human disease.
Keywords: immunohistochemistry • microscopy: light/fluorescence/immunohistochemistry • receptors