Conclusion
NSIR in rats is independent of hyperglycemia but due to STZ's direct cytotoxic effects on retinal progenitor cells. NSIR is a typical reaction to STZ-induced retinal oxidative stress and DNA damage. This significant finding suggests that NSIR may be a valuable model for studying retinal progenitor DNA damage-related diseases, potentially leading to new insights and treatments.
Methods
Intravitreal or subcutaneous injection of STZ was performed on newborn rats. Electroretinogram (ERG) and H&E staining investigated retinal function and morphological changes. Retinal cell types, cell death, proliferation, inflammation, and angiogenesis were studied by immunostaining. RNA sequencing was performed to examine the transcriptome changes of retinal cells after intravitreal injection of STZ.
Results
Intravitreal (5 μg or 10 μg) or subcutaneous (30 mg/kg) injection of STZ at the early stage of newborn rats couldn't induce hyperglycemia but caused NSIR (Neonatal STZ-induced retinopathy), including reduced ERG amplitudes, retinal rosettes and apoptosis, cell cycle arrest, microglial activation, and delayed retinal angiogenesis. STZ did not affect the early-born retinal cell types but significantly reduced the late-born ones. Short-term and long-term hyperglycemia had no significant effects on the NSIR phenotypes. RNA sequencing revealed that STZ induces oxidative stress and activates the p53 pathway of retinal cells. Locally or systemically, STZ injection after P8 couldn't induce SINR when all retinal progenitors exit the cell cycle.