Abstract
Purpose: :
Previous studies indicate that thyroid hormones play an important role in M/L-cone differentiation of the mouse. Little or no data exist however about cone development in other species of mammals, mainly due to the lack of proper methods. The aim of the present study was to examine if in vitro retinal culturing could be used to investigate and compare photoreceptor development in other rodent species.
Methods: :
Retinas of early postnatal (P0-P4) Sprague-Dowley rats, Syrian golden hamsters, Siberian hamsters and mice were explanted onto semiporous membranes, and kept in culture for 14-28 days. Culturing media contained a 1:1 mixture of DMEM and F12, supplemented with vitamins, amino acids and hormones, with or without serum (FCS, 10-30%) added. After fixation, general retinal morphology was compared on radial sections and opsin expression patterns were analyzed using immunocytochemistry and PCR . Cultures were compared with the retinas of age-matched in vivo littermates.
Results: :
All four species exhibited a near normal differentiation pattern, with M/L-cone densities and morphology comparable to that observed in vivo, even under definitive conditions, without serum added to the medium. The time of explantation had no significant effect on M/L-cone differentiation and the structure was also maintained under prolonged culturing conditions. Although the general morphology of cultured mouse retinas was inferior as compared to that of the other species, M/L-cones were detectable, and confined exclusively to the superior retinal half, a cone topography characteristic of in vivo retinas.
Conclusions: :
Our results indicate that in vitro culturing is a useful tool, to study M/L-cone differentiation in rodent species. The technique enables us to study potential factors influencing photoreceptor development, and to point out similarities and differences in retinal maturation between species.
Keywords: color pigments and opsins • retina: distal (photoreceptors, horizontal cells, bipolar cells) • retinal development