Thyroid hormone-dependent development of mouse cerebellar Purkinje cells in vitro

Using a well-defined medium with insulin, transferrin and selenium but without serum and albumin, we quantitatively determined the effect of thyroid hormones on the development of Purkinje cells in mouse cerebellar monolayer cultures. Addition of a thyroid hormone, T3 or T4, to the serum-free medium resulted in a highly elaborate dendritic development of Purkinje cells. The cultured Purkinje cells in the presence of T4 even showed similarities in shape and in synapse formation to normal Purkinje cells in vivo. Such effect of T4 on the dendritic arborization of Purkinje cells was dose dependent and significantly sensitive to a low dose of T4 even at 50 pM. The effect of T4 was confirmed by an inhibition experiment using amiodarone, which was reported to induce thyroid dysfunction. Furthermore, T4 affected not only Purkinje cell development but also the shape of other neural cells such as small interneurons (mainly granule cells) and astrocytes in cerebellar cultures. T4 induced development of both interneurons and astrocytes having long processes. These results indicate that thyroid hormones play a pivotal role in the development of mouse Purkinje cell dendrites acting on Purkinje cells directly and/or indirectly via the close interaction with interneurons and astrocytes.