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Akos Lukats, Arnold Szabo, Viktoria Doma, Gergely Halasz, Attila Magyar, Gyorgy Vegvari, Agoston Szel; Thyroid Hormone Dependent Differentiation of M/L-cones in Organotypic Cultures of the Rat and Syrian Hamster Retina. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3942.
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© ARVO (1962-2015); The Authors (2016-present)
Literature data indicate that thyroid hormones play an important role in M/L-cone differentiation of the mouse. Little data exist however about cone development in other species of mammals, mainly due to the lack of proper methods. In a previous work we demonstrated the expression of TRβ2 thyroid hormone receptor in the photoreceptors of the rat and the Syrian hamster. The aim of the present study was to examine if the hormone indeed controls M/L-cone development in these rodent species.
Retinas of early postnatal (P0-P4) Sprague-Dawley rats and Syrian golden hamsters 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%) added. Thyroid hormone (T3) was added to, or omitted from the cultures. After fixation, general retinal morphology was compared on radial sections and opsin expression patterns were analyzed using immunocytochemistry and PCR.
The retina of both species exhibited a near normal differentiation pattern in control cultures, with M/L-cone densities and morphology comparable to that observed in vivo, even without serum added to the medium. The structure was also maintained under prolonged culturing conditions. Withdrawal of T3 from the media affected only the cultures lacking serum substitution, indicating that serum alone contains enough thyroid hormone to allow full differentiation. The lack of hormone under serum free conditions significantly altered the staining pattern and number of M/L-opsin expressing cells. Even after 15 days in vitro, labeling with monoclonal probe completely disappeared, and the number of elements stained by polyclonal antiserum decreased significantly. The change was more prominent after 3 or 4 weeks in culture, but M/L-opsin expression could still be detected in all cultures using PCR reactions.
Our results show that thyroid hormone plays an important role in M/L-cone differentiation also in the two rodent species reported, and indicate that it may be a universal regulator in mammals. The organotypic culturing technique enables us to study potential factors influencing photoreceptor development, and to point out similarities and differences in retinal maturation between species.
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