Assistant Professor Massachusetts Eye and Ear, Harvard Medical School BOSTON, Massachusetts, United States
Abstract: Glaucoma is a “silent creeper,” with a significant proportion of patients getting their diagnosis at the late stages of the disease when a structural loss already occurred and a significant portion of host retinal ganglion cells (RGCs) is gone. Available glaucoma treatments reduce intraocular pressure medically or surgically, but it can only slow or halt disease progression. No therapies exist to restore lost visual function and target RGCs directly to improve their survival. Functional replacement of retinal ganglion cells is needed to recover sight lost to Glaucoma and other optic neuropathies. Our roadmap to achieve functional integration of stem cell derived RGCs aims to recapitulate the normal development, which requires alignment of intrinsic and extrinsic signals necessary for donor cell survival, migration, structural and functional integration, dendrite and axon outgrowth, synapse formation and acceptance by innate and adaptive immune system. The advanced transcriptomic analysis of human retinal development allowed us to identify several factors in the developing retina microenvironment that are not present in the adult. These include known neurotrophins (GDNF, BDNF), migratory (SDF1, aFGF) and axon guidance cues (Netrin, Slit). By creating the chemokine gradient within the host retina with recombinant SDF1 we were able to significantly improve the integration of donor RGCs following transplantation (2.7-fold) with no adverse effects. Our transplantation studies in severely immunodeficient NSG mice show that the viable donor neurons are primarily eliminated by host innate immune system. To further investigate this we have performed a timecourse transplantation study in reporter CX3CR1-GFP mice with in vivo imaging, histological and molecular readouts with and without inhibitors of microglia-RGC interaction. We have shown that it is possible to significantly increase donor cell survival (3.4-fold) by inhibiting the microglia-RGC interaction with Annexin V, which led to increased axon outgrowth into the optic nerve head. Overall, our studies confirm the feasibility of RGC replacement and strongly suggest the use of co-treatments to enable functional integration.
Funding Source: Gilbert Family Foundation, Department of Defense, National Eye Institute.
