Sonogenetic Vision Restoration for Inherited Retinal Disorders

Abstract

Purpose : While retinal prostheses have shown improvement of vision loss due to retinal degeneration, the electrical stimulation devices are invasive and require complex implantation surgeries. We have demonstrated use of focused single-element ultrasound transducers to elicit spiking activity in retinal neurons. However, significant challenges in the translation of this technology include (i) requirement of high-intensity ultrasound, and (ii) the lack of cell-specific stimulation. By sensitizing specific retinal cells (e.g., retinal ganglion cells) toward ultrasound (US) using the heterologously-expressed mechanosensitive channel (SAM), the sonogenetic simulation is a potential alternative therapeutic modality to restore visual function in the degenerated retina.

Methods : We have screened and mutated mechanosensitive channels (SAM^m) from different microbial species, which upon expression in mammalian cells and retina, allows sonogenetic stimulation by US with intensity orders of magnitude lower than that required without SAM sensitization. The activation of cells was verified and quantitatively measured by pressure clamp (in-vitro) and electrophysiology (in-vivo). For in-vivo study, mouse retina was sensitized with SAM^m(via intravitreal injection of AAV carrying SAM^m gene) and subjected to US stimulation of mouse eye. US-evoked electrical activities were measured by corneal and cortical electrodes, allowing evaluation of functional response.

Results : By molecular engineering, the activation threshold of SAM^m was significantly reduced as compared to wild-type SAM. Our preliminary studies show successful transfection of SAM^m in-vitro (HEK Cells) leads to activation of cells (measured by patch clamp/MEA) in response to low power ultrasound stimulation. In-vivo stimulation of SAM^msensitized retinal cells by low-intensity (< 1 MPa) ultrasound led to cellular activation, measured by cortical electrophysiology. Enhanced electrical signals (measured with corneal electrodes) in SAM^m-treated rd1 mice (with photoreceptor loss) was obtained in response to US stimulation as compared to the non-treated negative control.

Conclusions : SAM^m sensitization of the retina combined with external US stimulation elicited the functional response in blind mice model. The success of this combination therapy (Sonogenetics) may lead to a new clinical modality for the treatment of patients with severe vision loss due to inherited retinal disorders.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.