Three dimensional culture of pineal cell aggregates: a model of cell-cell co-operation.

Three dimensional (3-D) cultures of pineal cell aggregates were obtained by constant gyratory shaking the heterogenous cell populations, obtained from the rat pineals, in the DMEM (Dulbecco's modified Eagle's medium). Within 4 days, the pineal cells became organized into a tissue like configuration appearing as a compact ball, evidenced by the scanning electron microscopy. The 3-D aggregates seemed to be mainly composed of pinealocytes (round-oval cells), glial (elongated cells) and other unknown cells. The heterogenous cells were separated by intercellular spaces. The ultrastructural characteristics revealed by transmission electron microscopy exhibited the presence of granular lysosomes, typical of pinealocytes actively involved in the secretion. These pineal cell aggregates secreted melatonin and other indole amines i.e. 5-methoxytryptamine (5-MT), indole acetic acid (IAA), 5-methoxy-3-indole acetic acid (5-MIAA), tryptophol (TOL) and 5-methoxytryptophol (5-MTL) in the culture medium, indicating the functional aspect of pinealocytes. The 3-D aggregates cultures had advantages over the pineal monolayer cultures as, after 4 days of culture, the amounts of indole amines secreted by 3-D aggregates were higher than those secreted by monolayer cultures. Besides, the 3-D aggregates remained functional till 24 days in the gyratory culture conditions. In the continuous perifusion system, the 3-D aggregates secreted melatonin while challanged with isoproterenol. This 3-D model of pineal cell aggregates might be useful, in future, to perform other kinetic studies of the release of indole amines in perifusion experiments as this system allows the maintenance of pineal cells for a long period of time.