Postnatal neurogenesis in the cow pineal gland: an immunohistochemical study

In the pineal gland of cows and rats structures designated rosettes have been described both during embryonic development and in adult animals. In order to investigate the possible nature of the cells comprising such structures, in the present work we studied the pineal glands from 10 cows of one- or four-years-old using conventional immunocytochemical and confocal microscopy techniques. As markers of glial cells, we used anti-vimentin (Vim) and glial fibrillary acidic protein (GFAP) and anti-S-100 sera, and the pinealocytes were labelled with β-III tubulin. As a marker of stem cells, we used an antinestin serum, while an anti-PCNA serum was employed to label proliferating cells. To explore the neuronal nature of some cells of the rosettes, we used an anti-SRIF serum. The rosettes were seen to be present throughout the glandular parenchyma and displayed a central cavity surrounded by cells, most of which expressed all or just some of the above glial labels and nestin, although there were also some rosettes with cells that expressed β-III tubulin and other cells that expressed SRIF. Likewise, in the cells of the rosettes the cell nucleus showed strong expression of PCNA. Confocal microscopy revealed that the walls of the rosettes contained cells that coexpressed Vim/S-100, Vim/GFAP and Vim/nestin. The number of rosettes was significantly greater in the animals of one year of age with respect to the four-year-old cows. The present findings allow us to suggest that rosettes are evolving structures and that most of the cells present in their walls should be considered stem cells, and hence responsible for the postnatal neurogenesis occurring in the pineal gland of cows.