Non-invasive electrical stimulation as a potential treatment for retinal degenerative diseases

Transpalpebral electrical stimulation for the treatment of retinitis pigmentosa: study protocol for a series of N-of-1 single-blind, randomized controlled trial

BACKGROUND

Retinitis pigmentosa (RP) is an inherited disease characterized by a progressive loss of rod photoreceptors of the eye, leading to irreversible blindness. To date, to our knowledge, no clinical prospective studies have been undertaken that could document the effect of interventions that could reverse or reduce the progression of this disease. The application of microcurrent stimulation (ES) of the eye in the treatment of chronic eye diseases such as glaucoma and age-related macular degeneration has been used over several decades and has been reported to have beneficial effects to reduce the progression of these blinding diseases and has been supported by animal studies and smaller clinical studies, but to date, no large randomized clinical trials on the use of microcurrent therapy have been published. More recent clinical reports have also shown beneficial effects of ES on slowing the progression of RP but also lacks data from robust prospective clinical outcome studies. To our knowledge, this is the first prospective randomized study to evaluate the safety and clinical effectiveness of transpalpebral electrical stimulation (TpES) on the progression of RP.

METHODS

Randomized prospective study using N-of-1 trial 3 single-blind, crossover comparisons. The intervention period of each comparison is divided into treatment period and control period which are randomized arranged. Twelve participants will be strictly recruited in N-of-1 trial by the researcher in accordance with the inclusion and exclusion criteria. The main outcome of interest examined after each cycle of the 8-week intervention period is the assessment of the visual field (VF). Other variables of interest are best corrected visual acuity (BCVA), retinal function using electroretinogram (ERG), and visual function using NEI VFQ-25 questionnaire. Objective assessments of retinal changes will be undertaken using optical coherence tomography (OCT) and fundus autofluorescence (FAF).

DISCUSSION

The trial will evaluate the efficacy and safety of microcurrent stimulation on RP and provide high-quality evidence for clinical application through N-of-1 trial.

TRIAL REGISTRATION

Chinese Clinical Trial Registry; ChiCTR2300067357; https://www.chictr.org.cn/showproj.html?proj=174635 . Registered on 5 January 2023.

Noninvasive electrical stimulation as a neuroprotective strategy in retinal diseases: a systematic review of preclinical studies

BACKGROUND

Electrical activity has a crucial impact on the development and survival of neurons. Numerous recent studies have shown that noninvasive electrical stimulation (NES) has neuroprotective action in various retinal disorders.

OBJECTIVE

To systematically review the literature on in vivo studies and provide a comprehensive summary of the neuroprotective action and the mechanisms of NES on retinal disorders.

METHODS

Based on the PRISMA guideline, a systematic review was conducted in PubMed, Web of Science, Embase, Scopus and Cochrane Library to collect all relevant in vivo studies on "the role of NES on retinal diseases" published up until September 2023. Possible biases were identified with the adopted SYRCLE's tool.

RESULTS

Of the 791 initially gathered studies, 21 articles met inclusion/exclusion criteria for full-text review. The results revealed the neuroprotective effect of NES (involved whole-eye, transcorneal, transscleral, transpalpebral, transorbital electrical stimulation) on different retinal diseases, including retinitis pigmentosa, retinal degeneration, high-intraocular pressure injury, traumatic optic neuropathy, nonarteritic ischemic optic neuropathy. NES could effectively delay degeneration and apoptosis of retinal neurons, preserve retinal structure and visual function with high security, and its mechanism of action might be related to promoting the secretion of neurotrophins and growth factors, decreasing inflammation, inhibiting apoptosis. The quality scores of included studies ranged from 5 to 8 points (a total of 10 points), according to SYRCLE's risk of bias tool.

CONCLUSION

This systematic review indicated that NES exerts neuroprotective effects on retinal disease models mainly through its neurotrophic, anti-inflammatory, and anti-apoptotic capabilities. To assess the efficacy of NES in a therapeutic setting, however, well-designed clinical trials are required in the future.

Electrical stimulation alters DNA methylation and promotes neurite outgrowth

Electrical stimulation (ES) influences neural regeneration and functionality. We here investigate whether ES regulates DNA demethylation, a critical epigenetic event known to influence nerve regeneration. Retinal ganglion cells (RGCs) have long served as a standard model for central nervous system neurons, whose growth and disease development are reportedly affected by DNA methylation. The current study focuses on the ability of ES to rescue RGCs and preserve vision by modulating DNA demethylation. To evaluate DNA demethylation pattern during development, RGCs from mice at different stages of development, were analyzed using qPCR for ten-eleven translocation (TETs) and immunostained for 5 hydroxymethylcytosine (5hmc) and 5 methylcytosine (5mc). To understand the effect of ES on neurite outgrowth and DNA demethylation, cells were subjected to ES at 75 µAmp biphasic ramp for 20 min and cultured for 5 days. ES increased TETs mediated neurite outgrowth, DNA demethylation, TET1 and growth associated protein 43 levels significantly. Immunostaining of PC12 cells following ES for histone 3 lysine 9 trimethylation showed cells attained an antiheterochromatin configuration. Cultured mouse and human retinal explants stained with β-III tubulin exhibited increased neurite growth following ES. Finally, mice subjected to optic nerve crush injury followed by ES exhibited improved RGCs function and phenotype as validated using electroretinogram and immunohistochemistry. Our results point to a possible therapeutic regulation of DNA demethylation by ES in neurons.