Transplanted Donor- or Stem Cell-Derived Cone Photoreceptors Can Both Integrate and Undergo Material Transfer in an Environment-Dependent Manner

Abstract

SummaryHuman vision relies heavily upon cone photoreceptors, and their loss results in permanent visual impairment. Transplantation of healthy photoreceptors can restore visual function in models of inherited blindness, a process previously understood to arise by donor cell integration within the host retina. However, we and others recently demonstrated that donor rod photoreceptors engage in material transfer with host photoreceptors, leading to the host cells acquiring proteins otherwise expressed only by donor cells. We sought to determine whether stem cell- and donor-derived cones undergo integration and/or material transfer. We find that material transfer accounts for a significant proportion of rescued cells following cone transplantation into non-degenerative hosts. Strikingly, however, substantial numbers of cones integrated into the Nrl−/− and Prph2rd2/rd2, but not Nrl−/−;RPE65R91W/R91W, murine models of retinal degeneration. This confirms the occurrence of photoreceptor integration in certain models of retinal degeneration and demonstrates the importance of the host environment in determining transplantation outcome.

CRX Expression in Pluripotent Stem Cell-Derived Photoreceptors Marks a Transplantable Subpopulation of Early Cones

“…At 3 weeks post‐transplantation into the subretinal space of 8 to 10‐week‐old Pde6brd1 mice, human GFP + cells expressing the pan‐photoreceptor marker Recoverin were found in a distinct outer nuclear like layer in direct contact with the host secondary order neurons. Some of the transplanted human CRX + cells displayed the expression of pan cone photoreceptor marker, Arrestin 3, and cone opsins, which indicates further differentiation to more mature cones upon transplantation and corroborates recent data obtained with mouse ESC and retinal‐derived CRX‐GFP + photoreceptor precursors . Since no cones were found in the host retina, it is impossible for the CRX‐GFP + to have acquired the cone fate through cellular transfer.…”

“…In addition to developmental maturation, it is of interest to investigate the role of host retina. In this study, we used a model of fast retinal degeneration to ensure lack of host photoreceptors and minimize the likelihood of material transfer between host and donor photoreceptors, thus enhancing the possibility of hESC‐derived photoreceptor precursor engraftment . We performed immunocytochemistry using two different antibodies to HNAs and in both cases we observed colocalization with the CRX immunostaining and endogenous GPP expression, thus demonstrating that these cells were not endogenous mouse photoreceptors and did not arise through material transfer.…”

“…We did not observe any polyploid nuclei, thus excluding cell fusion as potential mechanism for the presence of CRX‐GFP + cells next to the host INL. In a recently published article, Waldron et al (2018) show that the retinal environment of Nrl −/− and Prph2 rd2/rd2 models supports both donor cone‐derived photoreceptor integration alongside material transfer, which the authors associated with a cone rich retinal environment and a disrupted OLM due to injection trauma . The Pde6brd1 mouse model is different to the two models described above in that it degenerates extremely fast and thus is unlikely to host cone or rod cells which would enable material transfer with the transplanted human cells.…”

“…Human embryonic stem cells (hESC) and induced pluripotent stem cells (hiPSC) have an intrinsic capacity to differentiate into self‐organized laminated retinal organoids which contain all the key retinal cell types that form synaptic connections, respond to light and electrophysiological stimuli and engraft in animal models of retinal degeneration . These retinal organoids have been shown to recapitulate human retinal development and moreover to yield a population of cone photoreceptors which are able to both integrate and undergo material transfer in an environment‐dependent manner . A growing number of recent publications have also indicated the usefulness of patient specific retinal organoids for disease modeling and toxicology studies .…”

Vitamin C improves the therapeutic potential of human amniotic epithelial cells in premature ovarian insufficiency disease

“…Others have suggested that stem cell-derived exosomes and exosomal microRNAs (miR-144-5p) inhibit ovarian cell apoptosis [4][5][6]. Recently, several studies noted that material transfer between host and donor cells accounts for the rescue effect of stem cell therapy [7,8]. Additionally, we cannot rule out the possibility that transplanted stem cells may integrate into host ovaries, differentiate into ovarian cells, and replace the impaired cells of the recipients.…”