Survival and Integration of Developing and Progenitor-Derived Retinal Ganglion Cells following Transplantation

Abstract

There is considerable interest in transplanting stem cells or progenitors into the injured nervous system and enhancing their differentiation into mature, integrated, functional neurons. Little is known, however, about what intrinsic or extrinsic signals control the integration of differentiated neurons, either during development or in the adult. Here we ask whether purified, postmitotic, differentiated retinal ganglion cells (RGCs) directly isolated from rat retina or derived from in vitro-differentiated retinal progenitor cells can survive, migrate, extend neurites, and form morphologic synapses in a host retina, in vivo and ex vivo. We found that acutely purified primary and in vitro-differentiated RGCs survive transplantation and migrate into deeper retinal layers, including into their normal environment, the ganglion cell layer (GCL). Transplanted RGCs from a wide range of developmental ages, but not from adults, were capable of extending lengthy neurites in the normal and injured adult rat retina ex vivo and to a lesser degree after transplantation in vivo. We have also demonstrated that RGCs may be differentiated and purified from retinal precursor cultures and that they share many of the same cell biological properties as primary RGCs. We have established that progenitor-derived RGCs have similar capacity for integration as developing primary RGCs but appear to form a lower number of presynaptic punctae. This work provides insight for further understanding of the integration of developing RGCs into their normal environment and following injury.

Neuronal remodeling in retinal circuit assembly, disassembly, and reassembly

“…The challenge now is that these seeded neurons must be integrated into the surviving circuitry to re-establish lost connections. A recent study demonstrated that embryonic and neonatal RGCs seeded into the adult retina integrate into the ganglion cell layer and project neurites in the IPL, where synapses may be formed [95]. How well transplanted neurons reinstate their detailed circuitry and functions remains to be elucidated.…”

Retinal ganglion cell polarization using immobilized guidance cues on a tissue-engineered scaffold

“…[12] However, RGC transplantation is inherently more difficult than photoreceptor transplantation, as it requires the transplanted cells to integrate dendritically with their amacrine or bipolar cell presynaptic partners in the inner plexiform layer, extend their axons radially through the retina to the optic nerve, grow down the optic nerve and find their appropriate targets in the brain. Previously, we investigated the use of both PLL-PEG hydrogels [26] and PLA electrospun scaffolds [27] to study RGC survival and neurite growth and as a potential cell delivery vehicle.…”

“…Recently, transplanted RGCs have been observed to project dendritic processes into the inner plexiform layer,[12] and stem cells transplanted directly onto the optic nerve head are able to project a process through the optic nerve head. [13] However, transplanted cells located away from the optic nerve head were unable to extend their axons radially as occurs with endogenous RGCs in the normal retina.…”

Towards the development of a human glaucoma disease-in-a-dish model using stem cells

“…Preclinical data have shown that primary RGCs and RP cellderived RGCs differentiated in vitro are able to survive transplantation intravitreally, migrate to the retina and in some cases, integrate into the ganglion cell layer with neurites extending into the nerve fiber layer and inner plexiform layer [81]. Aoki et al showed that, once implanted, ESC-derived eye-like structures contained cells that could differentiate into RGC-like cells in the host ganglion cell layer [82].…”