Abstract
Purpose :
Retinal and optic nerve (ON) microglia were identified previously as early indicators of damage and therapeutic targets in glaucoma models. Hydroxyl dendrimer nanoparticles selectively target activated microglia in the brain and retina. Here, we assess dendrimer-based nanoparticles for their ability to label activated microglia and therapeutically target microglia in laser-induced experimental rat glaucoma.
Methods :
Unilateral, translimbal laser treatment was performed to induce glaucoma in Wistar rats and IOP was monitored serially by rebound tonometry. Cy5-labelled dendrimer (D-Cy5) was administered either intravitreally or systemically at 3, 7, or 28 days following laser treatment. Retinal biodistribution and microglial uptake was determined by immunofluorescence microscopy and Iba-1 labelling at 3-28 days following dendrimer treatment. N-acetylcysteine-conjugated dendrimer (D-NAC) or free NAC (20μg/eye) was injected intravitreally 7 days after translimbal laser and retinal transcription of TNFa, IL-1b, MCP-1, ICAM-1, iNOS, and NRF2 was determined by RT-PCR (n=6 per group) on day 28.
Results :
In the laser induced glaucoma eyes, activated microglia were increased in the retina and ON compared to contralateral control eyes. Intravitreally administered D-Cy5 was selectively localized and retained in activated microglia of laser-treated eyes for up to 28 days. D-Cy5 colocalization with Iba-1 positive retinal microglia was 90% at 7 days after injection and 55% after 28 days. Retinal cross sections demonstrated nerve fiber layer and inner plexiform layer dendrimer uptake in laser-treated eyes, with minimal dendrimer uptake in healthy eyes. Following laser treatment and systemic D-Cy5 administration, dendrimer uptake was not seen in retina, however, was present in the ON. A single dose of intravitreal D-NAC reduced significantly retinal transcription of inflammatory markers TNFa , IL-1b , MCP-1, ICAM-1, and iNOS compared to untreated (p < 0.01, 0.01, 0.01, 0.05, and 0.01 respectively) and NAC-treated eyes (p<0.05, 0.05, 0.01, NS, and NS respectively).
Conclusions :
Hydroxyl dendrimer nanoparticles labeled activated microglia at early timepoints and reduced transcription of inflammatory genes in laser-induced glaucoma. These results highlight the potential of dendrimers for early glaucoma detection and as targeted therapeutics for glaucoma treatment.
This is a 2021 ARVO Annual Meeting abstract.