Abstract
Background:
Pathological retinal neovascularization, a major cause of blindness, occurs in conditions such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Microglial activation and chronic neuroinflammation play critical roles in disease progression by promoting vascular permeability and angiogenesis. While anti-VEGF therapies are the current standard of care, their efficacy is limited, requiring frequent intraocular injections and raising concerns about long-term retinal health. Noninvasive transpalpebral electrical stimulation (TpES) has emerged as a potential alternative therapy, but its mechanism and therapeutic impact remain poorly understood.
Methods:
To investigate the therapeutic effects of TpES, we applied daily microcurrent stimulation (300 µA, 20 Hz, 4 min) in laser-induced choroidal neovascularization (CNV) and streptozotocin (STZ)-induced DR mouse models. Vascular pathology was assessed using fluorescein angiography, optical coherence tomography (OCT), and immunohistochemistry. Mechanistic studies were conducted using primary microglia and human retinal endothelial cells (HREC) to evaluate TpES-induced changes in intracellular calcium ([Ca²⁺]i) signaling, mitochondrial membrane potential, and ATP production. Additionally, human RPE/choroidal explants from healthy, AMD, and DR donors were cultured to assess TpES effects on angiogenesis in healthy and pathological human tissues.
Results:
TpES significantly reduced vascular leakage (by ~ 30%, p < 0.001) and lesion size in the CNV model (p < 0.05), while also suppressing microglial infiltration and VEGF-A expression. In the DR model, TpES attenuated microaneurysm formation, preserved endothelial tight junctions (in vitro). Mechanistic studies revealed that TpES suppressed ATP-induced microglial activation by reducing mitochondrial membrane potential and intracellular ATP levels, leading to depletion of ER calcium stores and inhibition of proinflammatory and proangiogenic signaling. TpES also directly suppressed endothelial cell migration and tube formation, as well as angiogenic sprouting in human RPE/choroidal explants.
Conclusions:
These findings establish TpES as a dual-action therapy that mitigates both inflammation and pathological angiogenesis by modulating microglial and endothelial metabolism. Given its noninvasive nature and ability to target key pathways in retinal pathology, TpES represents a promising therapeutic strategy for AMD, DR, and other retinal vascular diseases.
Keywords:
Angiogenesis; Ca2+ signaling; Electrical stimulation; Microglia; Mitochondria; Retinal endothelial cells.