Abstract
Purpose: :
To determine whether endogenous retinal stem cells are present in Pigmented Royal College of Surgeon rats (RCS-P+ rats) and to determine how their distribution changes during retinal degeneration.
Methods: :
All experiments were conducted in compliance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Retinal vertical sections from RCS-P+ rats aged between 3 to 120 days were analyzed using routine histological stains (hematoxylin-eosin, HE) and fluorescence immunohistochemistry. Endogenous retinal stem cells were stained using a Chx10 antibody (Sigma, 1:100) conjugated to fluorescent markers (goat anti-rabbit IgG coupled to fluorescein isothiocyanate, FITC). Long-Evans rats of the same ages were used for comparison and as a normal control. Each retinal section was divided into 3 parts: anterior, middle and posterior one third of retina for imaging. Software Q-Win (LEICA DM TRET) was used to convert the fluorescent digital retinal images to corresponding black-and-white images used for the subsequent Chx10 expressing positively identified cell count manually. In every image we chose 5 equal areas throughout the retina (from RPE to NFL) and make to total chose area add up to the same that is 1mm2 and count the Chx10 expressing positively identified cell manually. Comparisons between different ages and rat strains were statistically analyzed using SPSS12.0 software by using Independent-T-test.
Results: :
Endogenous retinal stem cells are present up to 7 days postnatal both in the Long-Evans and the RCS-P+ rat. However, by day 15 stem cells are no longer present in the retina of either section. Retinal degeneration in RCS-P+ rats reaches a peak on day 30 and at this time, endogenous retinal stem cells reappear in the inner nuclear layer (INL) at a density of 26.7/mm2 and 26.8/mm2 in the middle and posterior retina, respectively. Towards the end of retinal degeneration in the RCS-P+ rat day 90 and 120, very few retinal stem cells are present in the INL at either retinal location. Comparison with the Long-Evans rat strain showed that .endogenous retinal stem cells were not present in any layer after day 15.
Conclusions: :
During the progress retinal degeneration of RCS-P+ rats, the degeneration stimulates the proliferations of stem cells which means that the retina environment is still hostile to stem cells and regeneration, but this does not halt or repair the damage.
Keywords: retinal degenerations: cell biology • immunohistochemistry • retinal culture