Update on the Status and Impact of the National Eye Institute Audacious Goals Initiative for Regenerative Medicine

Abstract

Purpose: This update will highlight a few of the projects funded by the National Eye Institute (NEI) Audacious Goals Initiative for Regenerative Medicine (AGI) and show their potential to advance regenerative medicine strategies and increase our understanding of the pathobiology of retinal disease.

Methods: We summarize the recent updates from a talk given to the scientific community about the progress of various AGI-funded projects.

Results: NEI is catalyzing the translation of ocular stem cell therapies with its AGI program. Since 2015, NEI has organized 3 consortia to catalyze stem cell-based therapies. The first focuses on developing functional imaging technologies that can enable noninvasive in vivo monitoring of activity of individual retinal neurons. The second consortium is identifying novel neural regeneration factors in the visual system. The third, funded in September of 2018, aims to generate translation-enabling models that mimic human eye disease and will evaluate the survival and integration of regenerated neurons in the visual system.

Conclusions: To date, 3 AGI consortia have catalyzed research in areas that will enable clinical trials for novel regenerative medicine approaches. With the first of the 3 consortia entering the final year of funding, some of these AGI-funded projects stand ready for deployment in the scientific and medical communities.

Introduction

According to the United States Centers for Disease Control and Prevention (CDC), age-related macular degeneration, diabetic retinopathy, and glaucoma are among the most common causes of irreversible blindness in the United States. These diseases are associated with aging, and as the average age of the population continues to increase in the developed world, the percentage of the population living with vision loss will continue to increase.¹ Significant advances by National Eye Institute (NEI)-funded investigators have been made in recent years in understanding the etiology and pathology of these diseases, but these advances have not yet translated into significant advances in patient treatments.

With the advent of groundbreaking new gene therapy and induced pluripotent stem cell technologies derived from these basic research advances, NEI introduced the Audacious Goals Initiative for Regenerative Medicine (AGI) to foster development and deployment of therapies aimed at preserving or restoring vision in patients suffering from diseases of irreversible blindness. Since launching, AGI has funded 3 consortia of researchers developing new tools for functional imaging, regenerative factor discovery, and disease modeling. Collectively, NEI has spent $62 million on 16 projects in these 3 research consortia on top of additional funding of investigator-initiated projects that have direct and indirect relevance to regenerative medicine. Figure 1 shows how the consortia build a foundation for the advancement of regenerative medicine therapies. As the regenerative medicine portfolio at NEI continues to expand, technologies, methodologies, and resources developed from AGI-funded research will begin to be available to the scientific community. This article provides updates on the status of some of these projects and their potential impacts on vision research.

FIG. 1.

The National Eye Institute Audacious Goals Initiative for Regenerative Medicine is laying the foundation to translate regenerative medicine approaches to the clinic through the strategic funding of collaborative consortia.

The AGI Functional Imaging Consortium

Key to any effort to introduce regenerative medicine therapies for clinical trials is the ability to quantitatively assess therapeutic efficacy. The AGI Functional Imaging Consortium, launched in 2015, funded 5 projects that would develop new imaging modalities to noninvasively image and measure the function of retinal neurons in patients. Such functional imaging technologies are critical to developing endpoints for clinical trials aimed to restore lost function to retinal neurons or integrate transplanted retinal neurons into patients' eyes. Specifically, the AGI Functional Imaging Consortium looks to deploy functional imaging technologies that will extend imaging capabilities already employed in the clinic, such as high-resolution optical coherence tomography. Other projects aim to improve experimental imaging techniques, such as adaptive optics (AO) scanning laser ophthalmoscopy, 2-photon microscopy, and magnetic resonance imaging, to increase their sensitivity, resolution, and applicability for clinical studies of the visual system.

Alfredo Dubra of Stanford University and Jessica Morgan of the University of Pennsylvania, for example, have created a near-infrared adaptive optics ophthalmoscope that can noninvasively measure cone photoreceptor activity at single-cell resolution. Previous studies by other groups demonstrated that cone photoreceptors increase their intrinsic reflective response to visual stimulus.² Dubra and Morgan used their AO ophthalmoscope to test whether this intrinsic property of cone photoreceptors could be used to quantitatively measure phototransduction in these cells. Indeed, despite heterogeneity in the responses of individual cone photoreceptors, Dubra and Morgan found correlations between the increase in amplitude of cone photoreceptor reflectance with both stimulus intensity and stimulus wavelength, suggesting their imaging modality could be used to noninvasively measure cone photoreceptor function in vivo.³

Projects such as these are critical to moving regenerative medicine therapies through the clinical trial process because of their ability to provide a quantitative endpoint in the absence of a behavioral endpoint accepted by U.S. Food and Drug Administration (FDA) regulators. Luxterna (rAAV-based RPE65 gene delivery), for example, consistently provided Leber congenital amaurosis patients with visual improvements as measured by performance in an obstacle course but failed to produce measurable improvements in electroretinogram (ERG) responses.⁴ Even multifocal ERG measurements, capable of providing more granular data on photoreceptor activity in the human retina, may be insufficient to measure improvements in photoreceptor activity conferred by the therapy being tested in the clinic. In light of the community's experience with previous testing of visual restorative therapies, there exists a clear need for new functional imaging technologies such as those being developed by AGI-funded investigators.

The AGI Regenerative Factor Discovery Consortium

The AGI has also encouraged discovery-based science with the goal of identifying factors that could be targeted to promote tissue regeneration either through activating endogenous repair mechanisms or through boosting the ability of transplanted cells to integrate and restore neural connections. Teams that are a part of the AGI Regenerative Factor Discovery Consortium have used high-throughput methodologies to screen, identify, and validate novel cellular factors that could be useful in efforts to restore function to the visual system. In response to the funding announcement encouraging researchers to adopt high-throughput screening, comparative biology, and new animal model development, 6 teams were awarded $12.4 million for 3 years and will ultimately contribute to a publicly available data repository that will catalyze future research to explore the biology of the new factors and explore related genes and pathways in other translational models.

One team, headed by Stephen Strittmatter at Yale University, has successfully developed the first functional genome-wide axon regeneration screen using mammalian neurons. Strittmatter's team plated cortical neurons from embryonic mice in 96-well plates and treated each well with control shRNA or 1 of the 83,000 shRNA clones his team developed to target >16,000 protein-coding genes in those cells. After disrupting the axons of those plated neurons, plates were screened using an automated system to identify candidate cell factors that, when knocked down, could promote axon regeneration.

Using this functional genome-wide screening approach, his team identified 479 genes that could promote axon regeneration when knocked down. Of the top 122 gene candidates, 63% of them showed high validity and reproducibility. Surprisingly, there was only slight overlap with previous genome-wide screening efforts that focused solely on transcriptome pathway analyses. Interestingly, many of the strongest gene candidates were in pathways related to transport, receptor binding, and cytokine signaling; many of these gene targets had also been identified in Caenorhabditis elegans or in studies focusing on single gene knockouts in mice.⁵ Projects such as this present the vision research community with a host of novel factors to investigate for regenerative medicine approaches, further underlining the capability of AGI to spur research in this area outside of the consortia.

The AGI Translation-Enabling Models Consortium

AGI teams are developing models that mimic important aspects of human vision, including the presence of cone photoreceptors, which are important for sharp central vision and color perception. Most animal models lack cone photoreceptors, so AGI scientists are developing new cone-rich animal models such as the ground squirrel and tree shrew. The AGI Translation-Enabling Models Consortium is generating new models that will allow vision researchers to explore the root cause of disease, study the changes that occur to eye tissues as disease progresses, and test potential therapies. Five projects are supported with $6 million per year for 5 years. With the new eye disease models, the AGI research teams will test strategies to replace photoreceptors and retinal ganglion cells (RGCs). These projects will develop the necessary surgical techniques and measurements of cell survival and function that will help pave the way for future human clinical trials of vision-restoration therapies.

Jeffrey Goldberg from Stanford is leading a multidisciplinary team involving laboratories at Stanford, Vanderbilt, Johns Hopkins, and the University of Washington. Together they will study a squirrel monkey glaucoma model and investigate parameters of human stem cell-derived RGC integration. By using fluorescently labeled human RGCs, they hope to optimize the delivery of the cells and their survival by comparing different surgical methods and immunosuppression regimens. During the course of their project, they plan to validate the monkey glaucoma model, study key structural and functional measures using innovative new modalities that should be portable between monkey and humans, and demonstrate the model's ability to move across institutions. Success of this project will provide an important proof-of-concept in nonhuman primates that would greatly aid therapeutic development before moving to human testing.

Future Directions

In January 2020, the NEI launched the Office of Regenerative Medicine (ORM). The office will focus on addressing the barriers facing regenerative medicine approaches by providing scientific and administrative support to the vision community. The ORM will coordinate future NEI Audacious Goals Initiative activities and disseminate the technologies and methods that come out of the funded consortia and by other NEI grantees that contribute advances in regenerative medicine. It will work with other institutes at the NIH and with other federal agencies to communicate relevant programs and information to all stakeholders. By serving as a central point of contact for all of NEI's programs that support and develop stem cell-related resources, the ORM hopes to promote research collaborations and accelerate the translation of therapies.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received.