Histological and molecular findings in the Retinal Pigment Epithelium after Selective Retinal Therapy with Real Time Feedback Technology

Abstract

Purpose : To define and evaluate the recovery of the retinal pigment epithelium (RPE) cells by using Q switched, frequency-double: Nd:YLF laser along controlled wound healing stimulation without photoreceptor damage.

Methods : The study was performed with local IACUC approval and in accordance with the ARVO guidelines on animal use. Q switched, frequency-double: Nd:YLF laser (Lutronic R:GEN Laser System) was tested in healthy 12-month-old C57BL/6J mice. Laser treatment was guided by the Real Time Feedback (RTF) technology which allows for specific targeting of melanosomes found in RPE cells. Clinical assessment utilized fundus imaging, optical coherence tomography (OCT) and fluorescein angiography (FA) was evaluated at different time points. Histological analysis using H&E, immunohistochemical targeting ZO-1 and real-time Polymerase Chain Reaction (RT-PCR) targeting metalloproteases (MMPs) and renin angiotensin system (RAS) components were used to interrogate relationships between anatomical and molecular changes.

Results : Clinical changes were detected specifically along RPE cells after the treatment using FA and color fundus images, while reflectivity on the OCT could detect significant changes in the RPE cells or outer retina layers. Henceforth all clinical findings improved and return to baseline levels after one month. Controlled RPE cell disruption and polymegathism phenomena was evident in RPE cells nearby the treated areas between hours to days after treatment which resolved within one month. A sustained upregulation on specific MMPs factors, specially on MMP9 was observed beginning at one month after treatment, whereas RAS components were upregulated weeks before. No molecular biomarker changes were observed in the retinal tissue.

Conclusions : Selective retinal therapy can specifically promote regeneration of the RPE cells activating two wound healing pathways. Changes in RAS component gene expression as part of the wound healing process is a novel approach to evaluate tissue repair within the retina and RPE capable of detecting earlier changes after photocoagulation therapy. This can complement a well-known benefit effect of chronic upregulation on MMPs expression.

This is a 2020 ARVO Annual Meeting abstract.