Glaucoma is a major cause of blindness and current treatments are insufficient. A major risk factor for glaucoma, and the only treatable risk factor, is elevated intraocular pressure (IOP). Current IOP-lowering therapies fail too often, and thus there continues to be great interest in novel IOP control strategies. The trabecular meshwork (TM), the key tissue determining IOP, has reduced cellularity in glaucoma, which has led a number of groups to study stem cell-based therapies for the TM. An obstacle to such therapies is cell delivery: current approaches have low cell delivery efficiency and specificity for the TM, and cannot deliver cells to all parts of the TM. Here a novel technological solution for ?steering? stem cells to the TM is proposed, which can be additionally used to visualize stem cell delivery and to monitor stem cell apoptosis. This approach will be tested in several models of ocular hypertension. The key technology is superparamagnetic and photosensitive nanoparticles. Their superparamagnetic properties mean that cells which have taken up these nanoparticles can be rapidly steered to the TM by a magnet placed at the limbus. Their photosensitivity means that cells can be visualized by ultrasound/photoacoustic imaging in the living eye. The functionality of these nanoparticles will be further enhanced by using a photosensitive marker of active caspase-3 to monitor stem cell apoptosis. Our overall objective is to validate these technologies as a safe and effective approach for monitoring and steering of stem cells to the TM, thereby restoring intraocular pressure (IOP) homeostasis in glaucoma patients.
Three specific aims towards this long-term goal are proposed, building on our significant preliminary data.
In aim 1, a novel caspase-3-sensitive reporter for monitoring apoptosis will be synthesized and characterized, and magnets for steering stem cells to the TM will be optimized.
In aim 2, an instrument capable of imaging of labeled stem cells in whole eyes, including longitudinal monitoring of stem cell distribution and apoptosis, will be developed.
In aim 3, stem cells will be delivered to the TM in two glaucoma models, and their ability to restore IOP homeostasis will be evaluated. The ability of ultrasound/photoacoustic imaging to monitor stem cell delivery to the TM and stem cell apoptosis will also be validated; and mesenchymal stem cells (MSCs) will be compared to differentiated induced pluripotent stem cells (iPSC-TMs) for their efficacy in restoring IOP homeostasis. This project is highly innovative: it the first study to steer and visualize stem cells as part of a treatment for ocular hypertension. It is also the first to compare the efficacy of MSCs vs. iPSC-TMs for treating ocular hypertension. We expect, as suggested by our strong preliminary data, to discover that stem cells can be efficiently and selectively steered to the TM by a simple magnet placed at the limbus for as little as 15 minutes; and that it will be possible to accurately monitor the location of stem cells in the eye and stem cell apoptosis over time. Further, we expect that TM function will be improved by stem cells steered in this way, as tested in 2 glaucoma models.
Glaucoma is the second leading cause of blindness worldwide, and a major risk factor for the disease is elevated pressure within the eye; indeed, all current treatments try to lower eye pressure, but are often unsuccessful. In glaucoma patients, we know that the tissue within the eye that controls eye pressure, the trabecular meshwork, has fewer cells, which presumably impedes tissue function. Here we use nanotechnology to develop a system to ?steer? stem cells to the trabecular meshwork to restore tissue function in patients, to visualize these cells in the eye, and to evaluate whether such a steered approach is effective in controlling eye pressure.
