Neuronal differentiation in the early human retinogenesis

Aim: Our study investigates the differentiation of retinal stem cells towards different neuronal subtypes during the critical period of human eye development.

Methods: Expression of the neuronal marker neurofilament 200 (NF200), tyrosine hydroxilase (TH) and choline acetyltransferase (ChAT) was seen by immunofluorescence in the 5th-12th - week stage of development in the human eye. Data was analysed by Mann-Whitney, Kruskal-Wallis and Dunn's post hoc tests.

Results: NF200, TH and ChAT cells appeared in the 5th/6th week and gradually increased during further development. The proportion of TH positive areas were distributed similarly to NF200, with a higher proportion in the outer neuroblastic layer. The proportion of a ChAT positive surface was highest in the 5th/6th - week whilst from the 7th week onwards, its proportion became higher in the optic nerve and inner neuroblastic layers than in the outer layer, where a decrease of ChAT positive areas were seen.

Conclusions: Our study indicates a high differentiation potential of early retinal cells, which decreased with the advancement of development. The observed great variety of retinal phenotypic expressions results from a large scale of influences, taking place at different developmental stages.