2015 Shaffer Research Grants

Glaucoma is the leading cause of irreversible blindness worldwide and disproportionately affects people of African descent because it occurs more frequently, has a younger age of onset, and a more aggressive course than other people groups. These findings are largely based on epidemiology studies performed outside of Africa, specifically the US and the Caribbean. Studies in East Africa and South Africa have found a much lower prevalence of glaucoma than those performed in the US and Caribbean, perhaps because people of African descent residing in the US and Caribbean are descendants of West Africans. Recently, we performed the first properly designed glaucoma prevalence study in West Africa (Ghana) and found a prevalence much more similar to the US and Caribbean populations. We also collected over 1,200 blood sample for genetic analysis, creating the largest genetic database in people of African descent in the world, in an attempt to identify the genes for glaucoma in this people group. The current study is designed to do three things: determine the number of new cases per year (incidence) of glaucoma in this population (no glaucoma incidence studies have been performed in sub-Saharan Africa), determine the rate of progression of glaucoma in the 362 people identified with glaucoma in the original study, and to add to the genetic material in our quest to identify the genes involved in glaucoma in people of African descent.

Glaucoma is often associated with elevated intraocular pressure (IOP). At present, the only effective approach to treat glaucoma is to reduce IOP. IOP rises beyond what the eye can tolerate because of increased resistance to fluid leaving the eye in the outflow pathways. There are two main outflow pathways: uveoscleral and trabecular. Prostaglandins, the most commonly prescribed class of glaucoma therapeutics, target the uveoscleral pathway. Compounds are in development to effectively and safely decrease resistance in the trabecular pathway. Self-administration of one or more daily topical medications by patients may affect IOP control due to poor adherence to therapy. Surgical treatments may result in complications and eventual loss of effectiveness, resulting in a return to topical drop therapy. Delivery of therapeutic genes to the eye is a promising strategy to provide long term IOP control, removing the patient from the drug delivery system. In this project, we aim to develop viral vector based therapeutic constructs that target the cytoskeleton of the trabecular meshwork ™, the key structure of the main drainage route. The vectors will be designed to express cytoskeleton-modulating proteins (caldesmon and C3) known to increase open spaces in the TM, thus increasing fluid flow from the eye and reducing IOP. Vectors will be tested in an organ culture system to measure effectiveness. Fluorescent proteins and other markers will be attached to the vectors to enable identification of cell types transfected by the vectors. Successful IOP lowering by the vectors will facilitate development of gene therapy for glaucoma patients.

Loss of vision in glaucoma is caused by the death of a specific type of neuronal cell, the retinal ganglion cell (the neuron that sends information to the brain). Presently there are no treatments aimed at neuroprotection for glaucoma patients. Unfortunately, this means that for many patients, physicians are left with no treatment options to prevent the progression of vision loss. This project aims to determine the molecular signaling pathways responsible for killing retinal ganglion cells in glaucoma. In this application, we concentrate on defining the molecular pathways that control axonal degeneration in retinal ganglion cells after glaucoma-relevant injuries, including ocular hypertension. Specifically, using genetic resources, we will determine whether two molecules that are important for axonal degeneration, prevent retinal ganglion cell death after axonal injury. Given the importance of axonal insult and degeneration in glaucoma, the experiments proposed in this study have the potential to define key therapeutic targets for developing neuroprotective treatments for glaucoma that target early pathological events.

For his research project to explore a novel idea in the field of neurodegeneration, defining the molecular cascade that controls axon degeneration, which is a key early event in glaucoma, Dr. Richard Libby was awarded the 2017 Shaffer Prize from Glaucoma Research Foundation. The Shaffer Prize, presented annually by Glaucoma Research Foundation, recognizes a researcher whose project best exemplifies the pursuit of innovative ideas in the quest to better understand glaucoma.

Glaucoma is a group of eye diseases that lead to damage to the optic nerve and can result in irreversible blindness. In the most common form of the disease, damage to the optic nerve is caused by elevated pressure inside the eye, due to a resistance of the aqueous humor to exit the eye. The exact mechanisms leading to that resistance to aqueous humor outflow are not known, but it has been speculated that blockage of the outflow channels might be a contributing factor. Accordingly, patients affected with glaucoma often present a build up of amorphous material in the outflow channels. Genetic studies showed lower amounts of alpha L-Iduronidase (IDUA) in the glaucomatous outflow pathway. IDUA is a lysosomal enzyme that is needed to break down sugars known as glycosaminoglycans (GAGs). These sugars are used to build tissues, but if not properly degraded, they accumulate in the body. IDUA deficiency causes mucopolysaccharidosis, a disease characterized by the accumulation of GAGs inside and outside the cells, gradually leading to tissues and organ dysfunction, with eventual cell death. Patients affected by this disease often develop ocular hypertension and glaucoma. Here, we propose (1) to clarify whether accumulation of GAGs causes elevated ocular pressure by characterizing the functionality of the outflow channels in a murine model of human mucopolysaccharidosis; and (2) test whether exogenous supplementation of IDUA improves outflow pathway tissue function. These studies have the potential to develop novel therapeutic strategies for the treatment of ocular hypertension and glaucoma.

The presence and rate of progression in glaucoma influence clinical decisions, yet the methods currently available to monitor progression are imprecise and do not allow clinicians to make accurate assessments of their patients. We recently developed an innovative model to detect and monitor glaucoma progression. This dynamic structure-function model jointly uses information from the structure and function of the eye to determine whether the disease is progressing. The model is also individualized to each patient to improve its ability to tease out true progression from variability. This is crucial because the large differences that exist between patients can mask the presence of change. The objective of this project is to test our model in the earliest stages of glaucoma. Detecting early changes is crucial to minimize vision loss. Using data from the large Ocular Hypertension Treatment Study, we will assess the specificity and sensitivity of our model in identifying conversion from ocular hypertension to glaucoma. We will also determine whether our model is able to detect this conversion at an earlier point in time. At the conclusion of this study, clinicians will have a powerful method to detect glaucoma progression, leading to improved patient care and preservation of sight.

Glaucoma is a leading cause of blindness and visual morbidity worldwide, and yet the pathophysiology of the glaucomatous process is still lacking fundamental understanding even considering recent advancements in imaging technology and genetics. The deleterious effects to the eye of elevated intraocular pressure (IOP) have been known for long and are now considered the main risk factor for glaucoma. A critical barrier for improving glaucoma diagnosis and treatment has been the lack of a complete understanding of the role of IOP in the eye and the causes underlying the range of patient sensitivities to IOP. Eyes that demonstrate similar clinical features may react differently to changes in IOP. The reason for these differences is mostly unknown. Our global hypothesis is that both IOP and the pressure inside the brain (cerebrospinal fluid pressure – CSFP) are significant contributors to the biomechanical environment within the optic nerve head. Hence, the sensitivity to IOP of a particular subject can be better predicted by considering CSFP. Our research aims to measure and manipulate IOP and CSFP in vivo in an animal model in order to uncover the factors that drive different sensitivity to IOP in different eyes. Our work will establish the fundamental principles by which the pressures inside the eye and the brain interact, and provide an avenue for understanding and eventually treating glaucoma by taking all properties of each individual eye into account.

Glaucomatous damage to axons occurs at the optic nerve head (ONH). Support cells within the ONH, called astrocytes, provide multiple functions to protect axons. However, early ONH astrocyte activation has been identified as a potential source of axonal injury in glaucoma. Strategies acting to maintain normal astrocyte function may lead to preservation of ONH axons and therefore reduce glaucomatous damage. The development of targeted drug-delivery strategies to sustain ONH astrocyte structure and function is an important area of research. ONH astrocytes have cellular extensions, which ensheath axons. We have shown that these cellular extensions are rich in a cytoskeletal protein called actin and re-orient prior to axonal injury in a rat model of glaucoma. The objective of this proposal is to locally deliver small molecules to the ONH in a rat model of glaucoma, with a specific aim of determining if local ONH actin modulation in vivo will alter ONH axonal survival. Our research is based upon the overall hypothesis that normal ONH actin-rich astrocyte extensions are necessary for axon survival, and disruption of astrocyte actin assembly will be detrimental to axons. Through our work, we will identify a novel ONH drug delivery method which can be used to assay other molecular pathways that may be involved in axon injury, and to test local axon-protective effects of small molecules in experimental glaucoma.

Glaucoma is a leading cause of blindness affecting millions of Americans. However, current treatment strategies are not sufficient to prevent disease progression and no specific blood test is available for early diagnosis and better follow-up of this blinding disease. To accomplish better management of glaucoma, our experimental research aims to characterize disease-causing molecular alterations and identify molecules that can be used for clinical testing. Our recent studies have indicated four specific molecules (apoptosis-inducing factor, CREB-binding protein, ephrin type-A receptor, and huntingtin protein) that can be measured in blood samples and exhibit increased levels in patients with glaucoma. The proposed project aims to determine the value of these molecules for clinical testing in glaucoma. We will therefore analyze the presence and abundance of these molecules (called “oecandidate biomarkers”) in blood and aqueous humor (intraocular fluid that fills the space between the cornea and the iris) samples collected from larger groups of patients with or without glaucoma and age-matched controls, and determine their predictive value for the initiation and progression of glaucoma. We expect that this new project will provide important information about specific molecular markers (called “biomarkers”) to diagnose glaucoma early, predict its prognosis, and monitor disease progression and treatment responses in patients with glaucoma. Prediction and early diagnosis of glaucoma will allow early treatment to halt disease progression, and monitoring the disease progression and treatment responses will facilitate the efforts ongoing to develop new and improved treatments for glaucoma.

In September 2015, IOVS (vol. 56 no. 10) published results from this research project in “Proteomics Analysis of Molecular Risk Factors in the Ocular Hypertensive Human Retina.” The published paper concluded that” “molecular alterations detected in the ocular hypertensive human retina as opposed to previously detected alterations in human donor retinas with clinically manifest glaucoma suggest that proteome alterations determine the individual threshold to tolerate the ocular hypertension-induced tissue stress or convert to glaucomatous neurodegeneration when intrinsic adaptive/protective responses are overwhelmed.”