Transcorneal but not transpalpebral electrical stimulation disrupts mucin homeostasis of the ocular surface

Abstract

Purpose Transcorneal electrical stimulation (TcES) is increasingly applied as a therapy for preserving and improving vision in retinal neurodegenerative and ischemic disorders. However, a common complaint about TcES is its induction of eye pain and dryness in the clinic, while the mechanisms remain unknown. Method TcES or transpalpebral ES (TpES) was conducted in C57BL6j mice for 14 days. The contralateral eyes were used as non-stimulated controls. Levels of intracellular [Ca2+] ([Ca2+]i) were assessed by Fura-2AM. The conductance resistances of the eye under various ES conditions were measured in vivo by an oscilloscope. Results Although TcES did not affect tear production, it significantly induced damage to the ocular surface, as revealed by corneal fluorescein staining that was accompanied by significantly decreased mucin (MUC) 4 expression compared to the control. Similar effects of ES were detected in cultured primary corneal epithelium cells, showing decreased MUC4 and ZO-1 levels after the ES in vitro. In addition, TcES decreased secretion of MUC5AC from the conjunctiva in vivo, which was also corroborated in goblet cell cultures, where ES significantly attenuated carbachol-induced [Ca2+]i increase. In contrast to TcES, transpalpebral ES (TpES) did not induce corneal fluorescein staining while significantly increasing tear production. Importantly, the conductive resistance from orbital skin to the TpES was significantly smaller than that from the cornea to the retina in TcES. Conclusion TcES, but not TpES, induces corneal epithelial damage in mice by disrupting mucin homeostasis. TpES thus may represent a safer and more effective ES approach for treating retinal neurodegeneration clinically.

Electrical stimulation alters DNA methylation and promotes neurite outgrowth

“…ES is currently being explored across various research areas to understand its beneficial effects 11–14 . It has proven its efficacy in regenerative medicine research and studies have also shown that it has the potential to regulate epigenetic events 15 .…”

“…ES is currently being explored across various research areas to understand its beneficial effects. [11][12][13][14] It has proven its efficacy in regenerative medicine research and studies have also shown that it has the potential to regulate epigenetic events. 15 In a recent study, nanosecond pulsed electric fields was shown to cause downregulation of DNA methylation transferase 1 (DNMT1), which mediated the DNMT1-OCT4/ NANOG axis resulting in the differentiation potential of mesenchymal stem cells.…”