Nanosecond laser induces proliferation and improved cellular health within the retinal pigment epithelium

Andrew Ian Jobling ^1* Quan Findlay ¹ Ursula Greferath ¹ Kirstan A Vessey ¹ Satya Gunnam ¹ Victoria Morrison ¹ Gene Venables ¹ Robyn H Guymer ² Erica L Fletcher ^1*

• ¹ The University of Melbourne, Parkville, Australia
• ² Centre for Eye Research Australia, East Melbourne, Victoria, Australia

Background: Age-related macular degeneration (AMD) is a leading cause of vision loss in those over 60 years of age. Although there are limited interventions that may prevent the development or progression of disease, more efficacious treatments are required. Short-pulsed laser treatment shows promise in delaying progression of early disease. This work details how nanosecond laser influences the retinal pigment epithelium (RPE), the principal cell type implicated in AMD.Methods: C57BL/6J mice (3-month-old) underwent monocular nanosecond laser treatment to assess short-term RPE response, while 9-month-old C57BL/6J and ApoEnull mice were similarly treated and longer-term responses investigated after 3 months. Human tissue was also obtained after two nanosecond laser treatments (1 month apart). RPE proliferation was assessed using bromodeoxyuridine and RPE gene change explored using qPCR and RNAseq. Melanin and lipofuscin content were quantified using histological techniques.Results: Nanosecond laser induced RPE proliferation in treated and fellow mouse eyes, with monolayer repair occurring within 3 days. This was replicated in human tissue, albeit over a longer duration (1-4 weeks). Wildtype animals showed no overt change in RPE gene expression after short or longer post-treatment durations, while laser treated ApoEnull animals showed increased Mertk and Pedf expression, and a reduced number of dysregulated aging genes in treated and fellow eyes after 3 months. Furthermore, melanin and lipofuscin content were restored to wildtype levels in laser-treated ApoEnull RPE, while melanolipofuscin granules were reduced within treated regions of human RPE.This work shows nanosecond laser stimulates RPE proliferation and results in an improved cellular phenotype. These data provide a biological basis for the prophylactic use of nanosecond lasers in AMD.