Modulation of microglia activation after human donor retinal ganglion cell transplantation

Stem cell-derived retinal ganglion cell transplantation therapy offers a promising avenue for restoring vision in patients with significant retinal ganglion cell loss. The major challenge in this therapeutic approach is ensuring the survival of transplanted human donor retinal ganglion cells within the host retina. Here, we demonstrated the pivotal role of host retinal microglia and macrophages in the rejection, acceptance and survival of human donor cells. To identify the potential targets for treatment in microglia-retinal ganglion cell interaction, we assembled a single-cell atlas for mouse retina during development, aging, maturation and across neurodegenerative conditions. To our knowledge, this is the largest integrated atlas containing 1,053,629 cells including 36,080 myeloid cells. The downstream analysis highlighted phagocytosis among other known pathways involved in microglia activation, neuroinflammation and host retinal ganglion cell damage. We hypothesized that the same mechanisms are responsible for donor retinal ganglion cell removal. We showed that it is possible to improve the survival of human donor stem cell-derived retinal ganglion cells through modulation of the host retinal microglia. Pretreatment of human donor retinal ganglion cells with annexin V and/or soluble Fas ligand before transplantation led to a 2.5-fold increase in donor cell survival, including the outgrowth of axons targeting optic nerve head. Detailed analyses of the host mouse retina post-transplantation revealed morphological changes microglia and macrophages typical for activation in neuroinflammation. These findings indicate that soluble Fas ligand and annexin V treatment can be used to improve the success rate of transplantation of neurons within the retina and central nervous system.