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Izhak Nir, Changdong Liu, Rong Wen; Light Treatment Enhances Photoreceptor Survival in Dystrophic Retinas of Royal College of Surgeons Rats. Invest. Ophthalmol. Vis. Sci. 1999;40(10):2383-2390.
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purpose. To determine whether treatment with bright light elicits a protective
response that enhances photoreceptor survival in Royal College of
Surgeons (RCS) rats with inherited retinal degeneration.
methods. RCS rats were illuminated for 10 to 12 hours with 130 foot-candles (fc)
of white or green light. Untreated littermates that were kept under low
cyclic light levels were used as control subjects. Photoreceptor
survival was determined by quantitative analysis of photoreceptor
nuclei and ultrastructural assessment of cellular organization. Basic
fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF)
gene expression were determined at the mRNA and protein levels.
results. Treatments of RCS rats with a single dose of bright light on
postnatal day 23 (P23) greatly enhanced photoreceptor survival.
Ultrasturctural analysis revealed intact inner segments in
light-treated retinas, whereas in untreated retinas only remnants of
inner segments were observed. By P42, numerous viable nuclei were
counted in the posterior retina of light-treated rats, whereas most of
the remaining nuclei in untreated RCS rat retinas were highly pyknotic.
At 2.5 days after treatment with a single dose of bright light, bFGF
gene expression was significantly higher than in untreated RCS rat
retinas. By P42, bFGF protein levels were still significantly higher in
the treated retinas.
conclusions. Exogenous bFGF has been shown to promote photoreceptor survival in the
RCS rat retina. Thus, the increased bFGF expression that was measured
in the light-treated RCS rat retinas may be a protective response to
light stress, which supports the observed rescue of photoreceptors in
light-treated RCS rat retinas.
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