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Gonzalez Calle A, Paknahad J, Pollalis D, Kosta P, Thomas B, Tew BY, Salhia B, Louie S, Lazzi G, Humayun M. An extraocular electrical stimulation approach to slow down the progression of retinal degeneration in an animal model. Sci Rep 2023; 13:15924. [PMID: 37741821 PMCID: PMC10517961 DOI: 10.1038/s41598-023-40547-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 08/12/2023] [Indexed: 09/25/2023] Open
Abstract
Retinal diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD) are characterized by unrelenting neuronal death. However, electrical stimulation has been shown to induce neuroprotective changes in the retina capable of slowing down the progression of retinal blindness. In this work, a multi-scale computational model and modeling platform were used to design electrical stimulation strategies to better target the bipolar cells (BCs), that along with photoreceptors are affected at the early stage of retinal degenerative diseases. Our computational findings revealed that biphasic stimulus pulses of long pulse duration could decrease the activation threshold of BCs, and the differential stimulus threshold between ganglion cells (RGCs) and BCs, offering the potential of targeting the BCs during the early phase of degeneration. In vivo experiments were performed to evaluate the electrode placement and parameters found to target bipolar cells and evaluate the safety and efficacy of the treatment. Results indicate that the proposed transcorneal Electrical Stimulation (TES) strategy can attenuate retinal degeneration in a Royal College of Surgeon (RCS) rodent model, offering the potential to translate this work to clinical practice.
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Affiliation(s)
- Alejandra Gonzalez Calle
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
| | - Javad Paknahad
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Institute for Technology and Medical Systems Innovation, Los Angeles, CA, 90033, USA
| | - Dimitrios Pollalis
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
| | - Pragya Kosta
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Institute for Technology and Medical Systems Innovation, Los Angeles, CA, 90033, USA
| | - Biju Thomas
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
| | - Ben Yi Tew
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Department of Translational Genomics, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Bodour Salhia
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Department of Translational Genomics, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA
| | - Stan Louie
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Mann School of Pharmacy and Pharmaceutical Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Gianluca Lazzi
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA
- USC Institute for Technology and Medical Systems Innovation, Los Angeles, CA, 90033, USA
| | - Mark Humayun
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90033, USA.
- USC Ginsburg Institute for Biomedical Therapeutics, University of Southern California, Los Angeles, CA, 90033, USA.
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Paknahad J, Humayun M, Lazzi G. Selective Activation of Retinal Ganglion Cell Subtypes Through Targeted Electrical Stimulation Parameters. IEEE Trans Neural Syst Rehabil Eng 2022; 30:350-359. [PMID: 35130164 PMCID: PMC8904155 DOI: 10.1109/tnsre.2022.3149967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
To restore vision to the low vision, epiretinal implants have been developed to electrically stimulate the healthy retinal ganglion cells (RGCs) in the degenerate retina. Given the diversity of retinal ganglion cells as well as the difference in their visual function, selective activation of RGCs subtypes can significantly improve the quality of the restored vision. Our recent results demonstrated that with the proper modulation of the current amplitude, small D1-bistratified cells with the contribution to blue/yellow color opponent pathway can be selectively activated at high frequency (200 Hz). The computational results correlated with the clinical findings revealing the blue sensation of 5/7 subjects with epiretinal implants at high frequency. Here we further explored the impacts of alterations in pulse duration and interphase gap on the response of RGCs at high frequency. We used the developed RGCs, A2-monostratified and D1-bistratified, and examined their response to a range of pulse durations (0.1−1.2 ms) and interphase gaps (0−1 ms). We found that the use of short pulse durations with no interphase gap at high frequency increases the differential response of RGCs, offering better opportunities for selective activation of D1 cells. The presence of the interphase gap has shown to reduce the overall differential response of RGCs. We also explored how the low density of calcium channels enhances the responsiveness of RGCs at high frequency.
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Paknahad J, Kosta P, Bouteiller JMC, Humayun MS, Lazzi G. Mechanisms underlying activation of retinal bipolar cells through targeted electrical stimulation: a computational study. J Neural Eng 2021; 18. [PMID: 34826830 DOI: 10.1088/1741-2552/ac3dd8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 11/26/2021] [Indexed: 11/12/2022]
Abstract
Objective. Retinal implants have been developed to electrically stimulate healthy retinal neurons in the progressively degenerated retina. Several stimulation approaches have been proposed to improve the visual percept induced in patients with retinal prostheses. We introduce a computational model capable of simulating the effects of electrical stimulation on retinal neurons. Leveraging this computational platform, we delve into the underlying mechanisms influencing the sensitivity of retinal neurons' response to various stimulus waveforms.Approach. We implemented a model of spiking bipolar cells (BCs) in the magnocellular pathway of the primate retina, diffuse BC subtypes (DB4), and utilized our multiscale admittance method (AM)-NEURON computational platform to characterize the response of BCs to epiretinal electrical stimulation with monophasic, symmetric, and asymmetric biphasic pulses.Main results. Our investigations yielded four notable results: (a) the latency of BCs increases as stimulation pulse duration lengthens; conversely, this latency decreases as the current amplitude increases. (b) Stimulation with a long anodic-first symmetric biphasic pulse (duration > 8 ms) results in a significant decrease in spiking threshold compared to stimulation with similar cathodic-first pulses (from 98.2 to 57.5µA). (c) The hyperpolarization-activated cyclic nucleotide-gated channel was a prominent contributor to the reduced threshold of BCs in response to long anodic-first stimulus pulses. (d) Finally, extending the study to asymmetric waveforms, our results predict a lower BCs threshold using asymmetric long anodic-first pulses compared to that of asymmetric short cathodic-first stimulation.Significance. This study predicts the effects of several stimulation parameters on spiking BCs response to electrical stimulation. Of importance, our findings shed light on mechanisms underlying the experimental observations from the literature, thus highlighting the capability of the methodology to predict and guide the development of electrical stimulation protocols to generate a desired biological response, thereby constituting an ideal testbed for the development of electroceutical devices.
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Affiliation(s)
- Javad Paknahad
- Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States of America.,Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, United States of America
| | - Pragya Kosta
- Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, United States of America
| | - Jean-Marie C Bouteiller
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States of America
| | - Mark S Humayun
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States of America.,Department of Ophthalmology, University of Southern California, Los Angeles, CA, United States of America
| | - Gianluca Lazzi
- Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States of America.,Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, United States of America.,Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States of America.,Department of Ophthalmology, University of Southern California, Los Angeles, CA, United States of America
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