Human limbal neurospheres prevent photoreceptor cell death in a rat model of retinal degeneration

BackgroundThe culture of retinal progenitors from an accessible adult stem cell source such as the limbus could provide a useful autologous source of retinal cell therapies. The human corneoscleral limbus contains multipotent stem cells that can be cultured as floating neurospheres. Previous work in rodents has demonstrated neuronal and photoreceptor differentiation from limbal neurosphere cultures. Here, this study has examined undifferentiated cultured adult human limbal neurospheres as donor cells for retinal cell therapies by transplantation into a rat model of retinal degeneration.

MethodsGene expression in limbal neurospheres was examined by immunostaining and western blot. Human limbal neurospheres were transplanted into the subretinal space of Royal College of Surgeon's rats. Rats were monitored by optical coherence tomography for 6weeks then processed for retinal histology.

ResultsHuman limbal neurospheres expressed the neural lineage markers, Nestin, sex determining region box-2 and N-cadherin, and the retinal transcription factors microphthalmia-associated transcription factor, sex determining region box-2 and orthodentical homeobox-2. Human limbal neurospheres could be cultured to express NeuN, neurofilament and rhodopsin. Rats receiving saline or no injection underwent complete degeneration of the retinal outer nuclear layer after 3weeks. In contrast, rats injected with human limbal neurospheres or retinal pigment epithelial cells maintained the outer nuclear layer for up to 6weeks. Gene expression in transplanted limbal neurospheres was inconsistent with the production of mature retinal pigment epithelial or photoreceptor cells.

ConclusionsHuman limbal neurospheres represent an accessible source of autologous donor cells for the treatment of retinal diseases.