Adult donor rod photoreceptors integrate into the mature mouse retina.

PURPOSE: Previous studies indicate that early postnatal mouse photoreceptors have the ability to integrate into the mature host retina after transplantation, while progenitors and fully differentiated photoreceptors do not. The authors sought to determine whether the decline in the ability of photoreceptors to integrate after transplantation with increasing age is related to a loss of migratory ability in the adult neurons or by a decrease in their survival.
METHODS: Dissociated retinal cells were transferred from green fluorescent protein-positive (GFP(+)) donor mice of ages ranging from embryonic day (E)12.5 to adults (>28 days postnatal [P]). Immunofluorescence was used to assess marker expression and the morphology of integrated cells. In vitro cultures of dissociated Nrl-GFP mice were used to assay survival.
RESULTS: It was confirmed in previous reports that neonatal rods integrate into adult hosts. However, in contrast to previous reports, the age of the donor cell was not as critical as previously reported, because it was found that donor cells older than P11 effectively integrated into adult host retina. Although fully adult photoreceptors (P28 and older) show a higher transplant failure rate than immature ones (P5), successful transplants had very similar numbers of integrated cells for both mature and immature donors. Integrated cells from all ages were indistinguishable from those of the host in morphology and marker expression.
CONCLUSIONS: Fully mature photoreceptors retain the ability to integrate into the mature retina. The authors propose that their potential for integration is limited primarily by their decreased survival after dissociation.