Eur J Anat, 12 (2): 97-114 (2008)

Pineal gliosis and gland ageing. The possible role of the glia in the transfer of melatonin from pinealocytes to the blood and cerebrospinal fluid

Gomez Esteban M.B., Munoz M.I., Carbajo S., Carvajal J.C., Alvarez-Morujo A.J., Barragan L.M.

Dpto. de Anatomía e Histología Humanas, Facultad de Medicina, Universidad de Salamanca, Avda. Alfonso X el Sabio s/n, 37007 Salamanca, Spain

ABSTRACT Using immunohistochemical approaches applied to 6 ?m-thick sections from the pineal glands of cows with ages between 1 and 7 years, we studied the expression of GFAP, vimentin and S-100 and of ?-tubulin. The latter compound appeared in both pinealocytes and in some nerve fibres. In both younger and older cows, vimentin was expressed in the somata of cells localised in peripheral zones of the glands and in fibres with a bead-like aspect that coursed deep into the centres of the glands, as well as in pericapillary cells, apparently in the endothelia of vessels and, like GFAP and S-100, in a thick network of prolongations located between the basal side of the epithelial cells of the pineal recess and pinealocytes, sometimes reaching the ependymal lumen. The network of glial prolongations formed a space with a reticulated aspect interposed between the pinealocytes and the ependymal epithelium. The thickness of this network was especially striking in the older cows. The expression of GFAP and S-100 was also observed in the somata and the cytoplasmic prolongations of cells distributed throughout the gland that surrounded the pinealocytes. In cows with ages of 4 and 7 years the pineal gland showed a pronounced degree of gliosis that isolated the pinealocytes from one another and from the vascular bed. Additionally, all three glial markers were expressed in cells whose somata and cytoplasmic prolongations configured spaces with a trabecular aspect, very poor in connective tissue, which coursed throughout the glands to reach the reticulated space, in especially thin neighbouring zones of the epithelium of the pineal recess. The results suggest a decisive role of the pineal glia in gland ageing, in the secretion of melatonin, and in the configuration of the vascular and ependymal pathways that the hormone must follow from pinealocytes to its target organs.

Keywords: beta tubulin, glial fibrillary acidic protein, melatonin, protein S 100, vimentin, age, aging, animal tissue, article, controlled study, cow, cytoplasm, ependyma, glia, gliosis, hormone release, immunohistochemistry, nonhuman, perikaryon, pineal body, pinealocyte, protein expression, vascular endothelium