Abstract
Purpose:
Various eye diseases, including proliferative diabetic retinopathy (PDR) and retinopathy of prematurity (ROP), are the result of a pathological neovascularization. Different animal models such as oxygen-induced retinopathy (OIR) have been developed in order to understand the cellular and molecular mechanisms of these diseases. One of the growth factors involved in both physiological and pathological neovascularization is the Insulin-like growth factor-1 (IGF-1). Previously, we have demonstrated the IGF-1 effect on retinal cell migration via IGF-1R and the expression of this receptor in retina of animals with and without OIR treatment (ARVO Meeting 2012). Herein, we examine the IGF-1R expression, tissue distribution and cellular localization in relationship with the retinal cell death.
Methods:
Neonatal C57BL/6J mice were subjected to 75% oxygen from postnatal day 7 (P7) to P12 and then returned to room air for five days. Control mice were exposed to room air from birth until P17. Retinal blood vessel patterns were visualized by GSA labeling. Retinas from animals with and without OIR treatment were analyzed for IGF-1R expression and tissue distribution at selected time points (P3, P12, P15, P18, P21 and P27). The IGF-1R localization was examined using cell-type specific markers (GFAP, GS, Brn3a, PKC alpha and calbindin among other) by immunofluorescence and confocal microscopy. In order to identify apoptotic cells in the same retinas, TUNEL assay (Roche) was used.
Results:
In retinas without OIR we first observed IGF-1R expression in endothelial cells which was confirmed by using the GSA. This receptor was also expressed at level of ganglion cells as well as in the end feet of Muller glial cells. In addition, we visualized staining for IGF-1R in inner and outer nuclear layers. When the IGF-1R expression in the OIR model was analyzed, we observed a change in the distribution due to an alteration in the structure of the neural retina. Considering that this model produces Muller glial cells activation and retinal cell death, then the expression of GFAP was analyzed. Increased GFAP expression was detected in Müller cells in OIR retinas from P15. Finally, in agreement with GFAP expression, TUNEL possitive cells in the retinas were also observed at P15.
Conclusions:
The IGF-1R distribution and localization in retinas were modified after OIR treatment coinciding with the onset of GFAP expression and the retinal cell death.
Keywords: 543 growth factors/growth factor receptors •
635 oxygen •
700 retinal neovascularization