Here we propose to develop a bio-engineered scaffold for the inner retina capable of being used as both a model for this tissue and as a tool for cell transplantation. The neural retina, like other parts of the central nervous system (CNS), fails to regenerate following cell death associated with injury or diseases. To overcome this lack of regenerative repair, in diseases of the photoreceptors, cell replacement therapies have been attempted. In these studies, injected cells are able to migrate into the correct lamina of the retina, form synapses and function in animal models.1, 2 But can such a technique be used with diseases of the retinal ganglion cells (RGCs) whose axons must regrow through the inhibitory environment of the diseased optic nerve? The recent discovery of molecular mechanisms that promote optic nerve and CNS axon regeneration, such as PTEN/SOCS3 or KLF4 deletion,3-6 combined with our studies showing transplanted RGCs extend processes locally and form synapses in the inner plexiform layer (IPL),7 suggest that a transplantation therapy may yet be possible for RGCs. However, data thus far suggest that transplanted cells are largely unable to direct their axons towards the optic nerve head, perhaps due to developmental changes in retinal guidance molecules.8, 9 Recently, we have developed a biodegradable radial electrospun scaffold (rES) cell delivery vehicle capable of directing RGC axons radially, matching the orientation of the retinal nerve fiber layer (NFL).10 However the RGCs seeded on the rES grow in both directions rather than having their axon growth polarized towards the center as it is in the native tissue. In addition, it is not known if the transplanted cells will be capable of extending their dendrites off of the cell delivery vehicle to form synapses with the injured retina. In this study, we will further develop our cell delivery scaffold, immobilizing neurotrophic factors found during development to polarize axon growth towards the scaffold center and the optic nerve head once transplanted. In addition, we will combine the rES with a hydrogel composed of ECM matrix components of the developing IPL in order to stimulate the transplanted RGC dendrites extension to retinal explants. Using these explant models, we will evaluate the transplanted cells for functional synaptic connections through staining and the propagation of light responses. Finally, using cells modified for regrowth through an injured optic nerve, we will investigate the ability of axons from transplanted cells to enter the optic nerve. These studies will lead to the creation of a retinal cell delivery device with the correct patterning of the ganglion cell layer and a hydrogel system optimized to stimulate the integration of the transplanted cells. Taken together, this proposal will be an important step towards our long term goal of restoring vision to those suffering from glaucoma and other optic neuropathies.
We propose to construct a new bioengineering approach to transplanting the cells which connect the retina to the brain. This approach will focus on a method for restoring vision to retinas in end stage glaucoma, the second leading cause of blindness in the United States.
