Ex Vivo Integration of Human Stem Retinal Ganglion Cells into the Mouse Retina

Cell replacement therapies may be key in achieving functional recovery in neurodegenerative optic neuropathies diseases such as glaucoma. One strategy that holds promise in this regard is the use of human embryonic stem cell and induced pluripotent stem-derived retinal ganglion cells (hRGCs). Previous hRGC transplantation studies have shown modest success. This is in part due to the low survival and integration of the transplanted cells in the host retina. The field is further challenged by mixed assays and outcome measurements that probe and determine transplantation success. Thefore, we have devised a transplantation assay involving hRGCs and mouse retina explants that bypasses physical barriers imposed by retinal membranes. We show that hRGC neurites and somas are capable of invading mouse explants with a subset of hRGC neurites being guided by mouse RGC axons. Neonatal mouse retina explants, and to a lesser extent, adult explants, promote hRGC integrity and neurite outgrowth. Using this assay, we tested whether suppmenting cultures with brain derived neurotrophic factor (BDNF) and the adenylate cyclase activator, forskolin, enhances hRGC neurite integration, neurite outgrowth, and integrity. We show that supplementing cultures with a combination BDNF and forskolin strongly favors hRGC integrity, increasing neurite outgrowth and complexity as well as the invasion of mouse explants. The transplantation assay presented here is a practical tool for investigating strategies for testing and optimizing the integration of donor cells into host tissues.