CRISPR-mediated Inhibition of TGF-β2 in the Trabecular Meshwork
The most important risk factor and treatment target of glaucoma is elevated pressure inside the eye. Current drugs that lower eye pressure do not treat the pathology of glaucoma, and therefore they tend to lose effect after prolonged treatment. Many studies showed that high levels of transforming growth factor β2 (TGF- β2) causes high eye pressure. Our proposed study aims to use a novel technology called CRISPR interference to correct those abnormal protein modifications and return the high TGF- β2 level to normal, with the hope of thus restoring function to the trabecular meshwork (TM) tissue that drains fluid from the eye.
In primary open-angle glaucoma (POAG) patients, the increase of eye pressure is due to damage in the trabecular meshwork (TM), a specialized tissue that functions as a safety valve. Many studies including ours have shown that cell factors, including TGF-β2 are elevated in the POAG TM, and their elevation induces glaucomatous damages. So one key question is how these factors are elevated in the glaucomatous TM (GTM). Our recent publication showed that there is an excessive modification of DNA associated proteins in the GTM, and this modification plays an important role in the determination of the level of TGF-beta2 in the GTM. Therefore, one potential therapeutic strategy for treating POAG would be lowering TGF-β2 by manipulation of DNA-associated protein modification.
Recently, a novel technology called CRISPR interference (CRISPRi) enables researchers to achieve DNA-associated protein modification for individual cell factors. The CRISPRi system consists of an enzyme (dCas9-KRAB) and an RNA molecule. The RNA molecule would guide the enzyme to the desired location in TM cells and restore abnormal DNA-associated protein modification to normal status. This system is suitable for POAG because it may correct the pathology in the TM. We will use TM cells, perfusion cultured human eyes, and mice to study the efficiency of the CRISPRi system. Upon completion of this project, we expect to have determined whether the dCAS9-KRAB system is a useful tool/therapy for treating glaucoma.
About the Researcher
Dr. Weiming Mao is an assistant professor at the North Texas Eye Research Institute (NTERI) of the University of North Texas Health Science Center. His research interest is in the area of molecular pathology of the trabecular meshwork (TM), a specialized tissue that finely regulates the pressure inside the eye. He has dedicated his efforts to elucidating the disease mechanism of glaucomatous damage in the TM, as well as developing new research tools and therapies. At NTERI, Dr. Mao uses molecular biology and cell biology techniques, perfusion cultured eyes, and mouse models to determine cell signaling changes in the glaucomatous TM. He also works on potential therapeutic strategies to treat glaucoma. Dr. Mao’s overall goal is to find the cause of glaucomatous elevation of the pressure inside the eye, target the abnormal molecules or pathways, and find a safe and efficient way to correct them.
After obtaining his PhD degree in the area of vision science at the University of Alabama at Birmingham, Dr. Mao received his postdoctoral training and became a faculty member at the University of North Texas Health Science Center.
Every three to four months, faculty members, postdocs, and graduate students at NTERI provide free vision screening and vision health education to the community. There are always glaucoma patients suffering vision loss in attendance, who ask us why their intraocular pressure (IOP) cannot be controlled by eye drops and if there is any breakthrough in research. Currently, the only approved and most effective treatment of glaucoma is to lower IOP. Many ocular hypotensive medicines have been developed, which greatly enhanced the treatment of glaucoma and protect the vision of glaucoma patients. However, after prolonged use of one or a combination of these medicines, they tend to lose their efficacy. I believe it is because these medicines do not address the pathological changes in the trabecular meshwork (TM), and it is the TM that controls the majority of the drainage of the fluid (aqueous humor) that fills the eye. Although these existing medicines lower pressure, they work either by decreasing the production of aqueous humor, or opening up an alternative and lesser drainage pathway, known as the uveoscleral pathway, for aqueous humor drainage. If we can find out the exact disease mechanism inside the TM, we will be able to develop compounds or genetic tools to restore its normal function, so that the high pressure inside the eye will be under control throughout our glaucoma patients’ lives.
I am very grateful to the BrightFocus Foundation and their donors, many of whom are glaucoma patients themselves, along with the families and friends of individuals with glaucoma. It is their encouragement and continual support that keep our research going.
First published on: August 24, 2017
Last modified on: June 30, 2020