2025 Shaffer Research Grants

Our recent discoveries of two cell resiliency increasing functions offer an initial glimpse of the roles played by specific subtypes of ion channels in retinal ganglion cells that we are showing act to diminish the metabolic dysfunctions that can lead to blindness. The proposed research is focused on how the metabolic state of different retinal ganglion cell subtypes, arising as a result to their unusually high energy needs, modulates their electrical excitability. By understanding the links between the cells bioenergetic requirements, the conditions under which they generate potentially harmful reactive oxygen species when making energy, and how they respond to these intrinsic metabolic signals by reducing their excitability, we will identify the responsible mechanisms that act to suppress metabolic crisis in retinal ganglion cells. This knowledge is a prerequisite for improving diagnostic assessment that may improve detection and allow early intervention to prevent or restore vision loss due to ganglion cell loss in optic neuropathies including glaucoma.

This project aims to develop gene therapy for the degenerative eye disease glaucoma. It advances the work of two collaborative teams who have collectively demonstrated that delivering a molecule called Protrudin to the eye allows for robust regeneration in the optic nerve whilst NAD-related therapies protect retinal neurons against glaucoma. Glaucoma is a common optic nerve degenerative disease affecting 80 million people worldwide. It is associated with raised intraocular pressure (IOP), however IOP is relevant in as little 60% of patients (varying between countries) whilst the common pathology is progressive dysfunction and loss of optic nerve fibers (axons) and retinal ganglion cells. These are the neurons that connect the retina to the brain through their axons in the optic nerve. Neuroprotective and regenerative strategies for glaucoma are of great therapeutic need. Ocular gene therapy could be a viable approach, with its success in the clinic already demonstrated for genetic eye diseases. In the case of glaucoma, an ideal gene therapy would need to be protective, as well as capable of promoting the regeneration of lost axons. Protrudin can provide both regenerative and protective functions, but we know these effects could be improved. The project will examine new gene therapies that have the potential to deliver optimized retinal neuroprotection as well as optic nerve regeneration. Importantly, we aim to develop a gene therapy that can be delivered from a single treatment with the potential for lifelong therapeutic effects. These studies will provide pre-clinical validation of a gene therapy for treating degenerative eye disease, that can be further developed towards clinical trials. The study will also have broad relevance, not only for other optic neuropathies, but also for wider central nervous system injury or disease.

During development, the cells of the optic nerve head secrete signals to guide retinal ganglion cell (RGC) axon growth towards the optic nerve. However, when RGCs are transplanted into adult retinas, they do not grow toward the optic nerve. Isolating optic nerve head cells (ONHCs) from both the adult and the developing retina, we found RGCs in culture will grow towards the developing ONHCs but not towards the adult ONHCs. In this study, we will purify out the different cell types within the ONHCs and identify which cells from the developing optic nerve head secrete the guidance factors. Quantitative mass spectrometry-based proteomics will be used to identify which secreted proteins are more highly expressed between the ONHCs in the developing retina and the adult retina and those proteins analyzed for which are related to axon guidance through pathway analysis. Using plasmids with a promoter engineered to target ONHCs, adult ONHCs will be modified to express the identified missing guidance factors in order to test their ability to rescue their function and guide RGCs towards them in a 3D printed model of the retina’s nerve fiber layer. Following this study, we will have developed a method for overcoming the lack of guidance of transplanted RGCs, the first step in restoring vision to patients with late-stage glaucoma.

Primary Open Angle Glaucoma (POAG) is a serious eye disease that can lead to blindness if not treated effectively. It is caused by an increase in pressure inside the eye, known as intraocular pressure (IOP). This pressure builds up because of damage to a part of the eye called the trabecular meshwork (TM), which is responsible for draining fluid (called aqueous humor) from the eye. When the TM doesn’t function properly, fluid accumulates, causing IOP to rise. Over time, this elevated pressure can damage sensitive cells in the retina, known as retinal ganglion cells (RGCs), eventually leading to vision loss and irreversible blindness. While current treatments for glaucoma focus on reducing IOP, they don’t fix the damage in the TM, and their effectiveness tends to decrease over time. Unfortunately, over 10% of people with glaucoma become blind in both eyes despite receiving treatment. One major cause of POAG, especially in young individuals, is mutations in a gene called myocilin (MYOC). These mutations are a leading genetic factor for glaucoma development, particularly a more aggressive form called Juvenile-Onset Open Angle Glaucoma (JOAG). JOAG often begins in childhood or adolescence, with patients experiencing very high IOP and rapid progression to vision loss. Standard treatments for glaucoma are less effective for JOAG, as they don’t address the disease’s underlying genetic cause. In JOAG, the mutations in the MYOC gene cause a harmful buildup of myocilin protein in the TM cells. This accumulation leads to cellular stress, specifically in a part of the cell called the endoplasmic reticulum (ER) and ultimately causes the TM cells to die. This worsens the drainage problem, leading to higher IOP and faster progression of the disease. Interestingly, the normal version of the MYOC gene is not actually necessary for controlling IOP. This means that removing or “knocking out” the mutated MYOC gene in patients could prevent the damaging effects it causes, potentially restoring normal TM function. Scientists believe that using gene-editing technologies to permanently remove the defective MYOC gene could provide a one-time cure for this type of glaucoma, effectively halting disease progression and preserving vision. However, traditional gene-editing methods, such as CRISPR-Cas9, come with significant risks. CRISPR-Cas9 works by making cuts in the DNA, which can lead to unintended effects, such as damaging other important parts of the DNA (off-target effects) or causing large-scale genetic changes that could be harmful. Additionally, it’s difficult to deliver CRISPR-Cas9 to the right tissues in the eye without causing prolonged and potentially dangerous gene-editing activity, which could increase the risk of unwanted side effects, including cancer. To overcome these challenges, this project proposes using a newer and more precise gene-editing technique called “base editing.” Unlike CRISPR-Cas9, base editing doesn’t cut the DNA, which reduces the risk of off-target effects and large-scale genetic changes. Additionally, this project will explore the use of innovative delivery systems called lipid nanoparticles (LNPs) to safely and effectively deliver the base-editing technology specifically to the TM cells in the eye. This advanced approach could revolutionize glaucoma treatment by offering a highly targeted, one-time therapy that directly addresses the disease’s root cause, providing hope for a lasting solution for patients suffering from MYOC-related glaucoma.

Glaucoma is a leading cause of blindness worldwide. It primarily affects retinal ganglion cells (RGCs), which transmit visual information from the eye to the brain via the optic nerve. In glaucoma, neuroinflammation plays a major role in vision loss and is driven by overactive astrocytes, a type of support cell in the retina. When these astrocytes become reactive, they contribute to the damage and death of RGCs. Our project explores the potential of a naturally occurring molecule called lipoxin B4 (LXB4) to counteract this harmful process. LXB4 is known for its anti-inflammatory properties, and we’ve found that it can protect RGCs by reducing inflammation and calming reactive astrocytes. LXB4 also lowers the production of harmful proteins like C3, which are linked to increased inflammation in the optic nerve. By reducing astrocyte overactivity and inflammation, LXB4 helps preserve RGCs, potentially preventing further vision loss. This research introduces a new approach to treating glaucoma by focusing on protecting retinal cells with anti-inflammatory strategies, rather than relying solely on reducing eye pressure. If successful, LXB4-based therapies could provide a new way to slow or stop glaucoma’s progression and help millions of people maintain their vision.

Consequences of elevated intraocular pressure include compression of nerves in the back of the eye, which carry visual information to the brain. These nerves exit the eye through a complex tissue called the lamina cribrosa. The sustained eye pressure elevation causes the cells and support beams in the lamina cribrosa to stretch and change shape, which affects their behavior and ability to respond normally. The mechanisms that cause abnormal responses in glaucoma are still not fully known. However, it is thought the aberrant responses by cells at the lamina cribrosa play a significant role in glaucoma progression. One response of lamina cribrosa cells is the release of small particles called “extracellular vesicles”. These particles contain cellular components that regulate the cell’s environment, including the structural and biochemical support network known as the extracellular matrix. This project aims to determine if cells from the lamina cribrosa release extracellular vesicles that affect the extracellular matrix of the lamina cribrosa tissue. Our experiments are designed to first assess the extracellular vesicles from physiologically normal compared to glaucomatous lamina cribrosa cells and then stress them by stretching and monitor changes in the released extracellular vesicles. Successfully determining the role that extracellular vesicles play in extracellular matrix turnover in the lamina cribrosa will contribute to our knowledge of the mechanism leading to glaucoma progression and assess their potential as a therapeutic for this blinding disease.

Glaucoma, a leading cause of irreversible blindness, results from the progressive loss of retinal ganglion cells (RGCs), which transmit visual signals from the eye to the brain. A hallmark of glaucoma is the remodeling of the connective tissues in the optic nerve head (ONH) that support RGC axons. While high intraocular pressure and aging are well-established glaucoma risk factors affecting these tissues, the impact of low blood pressure—another independent risk factor—remains underexplored. Low blood pressure is thought to contribute to glaucoma by reducing blood flow to the ONH. This study aims to understand how chronically low blood pressure influences ocular blood flow and whether it alters the stiffness of the connective tissues surrounding the ONH. Using advanced ultrasound imaging, we will track blood flow and assess changes in the mechanical properties of the ONH and its supporting tissues in a rat model of low blood pressure. We hypothesize that reduced blood flow from low blood pressure triggers scleral stiffening, which increases strain on the more compliant ONH and ultimately leads to RGC damage, potentially driving glaucoma progression. By uncovering the mechanisms linking low blood pressure to glaucoma, we aim to pave the way for new neuroprotective glaucoma treatments that target the mechanovascular environment of the ONH.

Primary Open Angle Glaucoma (POAG) results in gradual loss of vision resulting in irreversible blindness in patients above 40 years in age. POAG is strongly associated with a harmful increase in pressure within the eye. Increase in eye pressure results in loss of Retinal Ganglion Cells (RGCs), the nerve cells that are necessary for sight. Eye pressure increases due to inadequate drainage of aqueous humor, a fluid that is secreted in the eye to nourish important tissues such as the lens and the cornea. Normally, aqueous humor leaves the eye through drainage channels known as the Trabecular Meshwork (TM). TM is maintained by specialized cells known as the TM cells. In patients with POAG, these drainage channels are clogged due to the dysfunction in TM cells. Dysfunction in TM cells leads to constriction and accumulation of excessive connective tissue material which results in clogging of the drainage channels. Currently drugs can be applied to the eye that prevent the formation of aqueous humor or facilitates an increase in the drainage of fluid by degrading the connective tissue within the eye. Patients where drugs are not effective are treated with invasive surgical techniques which imposes risks of further loss of complete vision. However, some patients are refractive to both strategies and lose their ability to see. In our preliminary studies, we have demonstrated that NADPH Oxidase -4 (NOX4) an enzyme that regulates the generation of reactive oxygen species in TM cells, when activated excessively, can cause TM cell dysfunction and increase the accumulation of connective tissue material. In this study, we propose to determine if inhibiting NOX4 can prevent the increase in pressure within the eye. If successful, this study may usher in a new treatment strategy for the management of POAG.

Retinal ganglion cells (RGC) project axons over long distances and connect with postsynaptic target neurons in the brain to relay visual information. RGC axons are especially vulnerable to elevated intraocular pressure due to glaucoma, such that damage progresses from the distal axon leading to cell death in the retina. Recent work has shown that target neurons also undergo transsynaptic degeneration following the loss of RGC input. Progressive glaucomatous degeneration provides a therapeutic window for treatments aimed at preventing vision loss. While prior studies have identified many signals that confer neuroprotective properties on retinal cells, approaches to prevent degeneration of target neurons are still unclear. This proposal investigates the effect of modulating neural activity in target neurons on preventing glaucomatous RGC axon degeneration and conferring neuroprotection to target neurons. The findings from this proposal will test a direct approach to prevent vision loss in mouse models of glaucoma and holds therapeutic relevance for treating human glaucoma.