Abstract
Purpose :
Pathologies such as Age-related Macular degeneration cause irreversible blindness through late-stage retinal degeneration and there is currently no effective cure. Humanin-G is a mitochondrial derived peptide with reported oxidative and ER-stress related cell death protection. RCS rats have severe retinal degeneration, thickening of retinal layers due to the buildup of cellular debris, and severe vision loss. We hypothesize that subconjunctival injections of Humanin-G loaded PLGA microspheres will help to delay retinal degeneration in RCS rats.
Methods :
Our experimentation started with the RCS rats consisting of subconjunctival injection of HNG microspheres. Starting at P21, rats were anesthetized with Ketamine/Xylazine (37.5-50 mg/kg Ketamine, 5-10 mg/kg Xylazine) (dosage depends on animal’s sex). Females receive a lower dosage than males. After rats are anesthetized, the superior eye region is exposed and 50-100 uL of HNG-microsphere solution, or empty-microsphere solution, are slowly injected into the subconjunctival space of both eyes. Non-injected animals are also included. The experiment was concluded after 2 weeks (Short term study) and 6 weeks (long term study).
H&E staining was performed following standard protocols. From the images, we measured and compared the retinal layers using ImageJ to observe the differences between our treated and non-treated samples.
Results :
The 2-week experiment showed a thinner Layer C (IS/OS Photoreceptor layer) for the Empty MS compared to NT (p=0.0004) and the HNG-MS to NT (p=0.0013). In our set of 6-week experiments, we found that Layer C with the HNG-MS was on average less thick than both the empty-MS (p=0.0279) and the NT (p=0.0269). Our 6-week RCS samples also showed a larger empty-MS Layer D (RPE) compared to NT (p=0.0425).
Conclusions :
Following treatment, we observed thinner retinal layers, contrasting RCS rats' typical thickening due to retinal degeneration-related debris buildup. Our 2-week study's end revealed a potential protective effect of both HNG-MS and Empty-MS. We also see a similar effect with layer C in our long term 6-week study as the HNG-MS treated rats had a thinner layer than both the NT and Empty-MS. These findings suggest that HNG-MS treatment potentially slows retinal degeneration, observed in both short- and long-term studies, prompting further research to evaluate HNG as a treatment for retinal degeneration.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.