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5-Fluorouracil reduces proliferating cell nuclear antigen immunoreactive cells in goldfish retina
1Department of Anatomy, University of Calgary Faculty of Medicine, Alberta, Canada.
Abstract:
A pyrimidine analogue, 5-fluorouracil (5-FU), was injected intravitreally into one eye of the goldfish, either alone, or before or after injection of the same eye with the dopaminergic neurotoxin, 6-hydroxydopamine (6-OHDA). Effects of these agents were explored by measuring their actions on numbers of proliferating cell nuclear antigen-immunoreactive (PCNA-ir) cells, representing mitotically active rod precursor cells (RPCs) in normal conditions, in both treated and untreated retinas. At various intervals (5-45 days after the first injection of drug), the retinas (n = 6 for each treatment group) were isolated and processed as wholemounts by an indirect immunohistochemical method for PCNA. Some retinas were cryosectioned and processed for certain immunoreactive cells other than PCNA. Changes in the mean density of PCNA-ir cells, following intravitreal 5-FU (10 micrograms/2 microliter saline on 3 consecutive days) alone or in combination with intravitreal 6-OHDA (2.5 micrograms/2 microliter), were statistically compared for interval vs. day 0 (control from intact retinas) and for treated vs. contralateral (untreated or treated) retinas, in both outer and inner nuclear layers (ONL and INL, respectively). 5-FU at this dose drastically reduced the densities of endogenous and 6-OHDA-induced PCNA-ir cells in the ONL of treated retinas, but transiently increased them in the contralateral untreated retinas, probably reflecting an injury influence from the treated retina. The density of PCNA-ir cells at the retinal margin was also greatly reduced in treated retinas. Such changes peaked on days 10-15, and gradually disappeared over days 30-45.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Intravitreal 5-fluorouracil (5-FU) significantly reduced proliferating cell nuclear antigen-immunoreactive (PCNA-ir) cells in goldfish retinas, impacting rod precursor cells (RPCs). This effect was observed in treated and contralateral eyes, with recovery noted over 30-45 days.
Area of Science:
- Ophthalmology
- Neuroscience
- Cell Biology
Background:
- The goldfish retina possesses regenerative capacity, with rod precursor cells (RPCs) crucial for maintaining retinal integrity.
- 5-fluorouracil (5-FU) is a pyrimidine analogue used in chemotherapy, and 6-hydroxydopamine (6-OHDA) is a dopaminergic neurotoxin.
- Understanding the impact of cytotoxic agents on retinal cell proliferation is vital for developing therapeutic strategies.
Purpose of the Study:
- To investigate the effects of intravitreal 5-fluorouracil (5-FU) on cell proliferation in goldfish retinas, both alone and in combination with 6-hydroxydopamine (6-OHDA).
- To quantify changes in proliferating cell nuclear antigen-immunoreactive (PCNA-ir) cells, indicative of mitotically active RPCs, following drug treatment.
Main Methods:
- Intravitreal injections of 5-FU and/or 6-OHDA were administered to goldfish eyes.
- Retinas were analyzed at various intervals (5-45 days) using immunohistochemistry for PCNA-ir cell detection.
- PCNA-ir cell densities were quantified in treated and contralateral retinas, including the outer nuclear layer (ONL) and retinal margin.
Main Results:
- Intravitreal 5-FU (10 µg/day for 3 days) drastically reduced PCNA-ir cell densities in the ONL of treated retinas.
- 5-FU also reduced PCNA-ir cells in retinas treated with 6-OHDA and at the retinal margin.
- A transient increase in PCNA-ir cells was observed in contralateral untreated retinas, suggesting a systemic injury response.
Conclusions:
- 5-FU significantly inhibits proliferation of RPCs in the goldfish retina, impacting both endogenous and neurotoxin-induced proliferation.
- The observed effects on PCNA-ir cells peaked around 10-15 days post-treatment and showed gradual recovery by 30-45 days.
- These findings highlight the potent anti-proliferative effects of 5-FU on retinal precursor cells and suggest potential for modulating retinal regeneration.