Abstract
Purpose:
The Royal College of Surgeons (RCS) dystrophic rats are widely used for modeling human diseases characterized by RPE cell dysfunction or degeneration, and represent the standard pre-clinical model for RPE transplantation. However, there are disadvantages associated with this model, such as the early onset and fast progression of degeneration, and the ability of diverse cell sources to delay photoreceptor degeneration. Here we describe in detail the effect of sodium iodate (SI), a strong inducer of RPE cell death, on the mouse retina, and evaluate the utility of this model for transplantation experiments.
Methods:
SI was injected systemically in 6-8 week old C57BL/6 mice. Functional characterization was done by ERG and by measuring visual acuity with an optomotor drum, 3, 7, 14, 21 and 28 days post injection. Morphological characterization and RNA isolation were performed at the indicated time points. hESC-derived RPE cells were transplanted into the subretinal space 1 week after SI injection. 3 weeks post transplantation the retinae were isolated and analyzed.
Results:
The effect of SI on RPE cells was very severe, leading to the complete loss of the RPE monolayer by day 7. The effect on photoreceptors was slower, with 10-33% reduction of ONL thickness by day 28. The ERG showed that 3 days post injection the retinae were less sensitive and that by day 14 both a- and b-waves became unrecordable. Interestingly, light seemed to enhance the effect of SI, since ERG waves were better preserved when animals were kept in the dark. A reverse transcription followed by PCR using primers specific for genes involved in the phototransduction cascade and pigment regeneration showed a reduced expression of several genes by day 3. In SI-treated retinae protein mislocalization and dendrite sprouting of bipolar cells was observed. Interestingly, transplantation into the SI-model revealed that RPE donor cells were able to form a polarized monolayer on the free Bruch’s membrane and to phagocyte shed outer segments.
Conclusions:
Injection of SI is a reproducible protocol to cause RPE toxicity and, consequently, retinal degeneration. Additionally, it leads to altered gene expression and retinal remodeling. Our combined data suggests that the SI model is appropriate for analyzing the behavior of donor cells upon transplantation, but less suitable for functional studies.
Keywords: 701 retinal pigment epithelium •
741 transplantation