Immunohistochemical Studies of Cell Organization in the Human Epiphysis

Objective. To study the cellular composition of the human epiphysis. Materials and methods. An immunohistochemical method using cell-specific markers selectively detecting astroglial, endothelial, nerve, and mast cells was employed to study the epiphysis in seven males aged 16–68 years. Antibodies to glial fibrillary acidic protein (GFAP), vimentin, low molecular weight neurofilament proteins (clone 2F11), and mast cell tryptase were used. Results. Immunohistochemical reactions for GFAP in the human epiphysis identified a large number of astroglial processes but few astroglial cell bodies. Cells had relatively small primary processes which were significantly thicker than those of stellate astrocytes in other parts of the brain. Astrocyte processes formed dense plexuses around blood vessels and many concretions. Many cell processes in the stroma and particularly the parenchyma and blood vessel endothelial cells were vimentin-immunoreactive. Coexpression of GFAP and vimentin was not seen in any of the structures studied. Low molecular weight neurofilament proteins were detected in occasional pinealocytes and their processes. Mast cells immunohistochemically labeled for tryptase were detected in all the epiphyseal formations studied (most frequently in the stroma) Conclusions: 1) GFAP-immunopositive astrocytes in the human epiphysis differed in terms of their morphological features from typical stellate astrocytes in other parts of the brain, such that pineal GFAP-immunopositive astrocytes could be placed in a separate subgroup of astrocytes; 2) human epiphyseal astrocytes did not simultaneously contain GFAP and vimentin, in contrast to pineal astrocytes in other mammals; 3) mast cells are a consistent component of the human epiphysis – obligatory in the stroma and facultative in the parenchyma; 4) human epiphyseal pinealocytes express neuron-specific neurofilament protein, which is evidence supporting their neuron-like nature; 5) the localization of neuron-like endocrine cells and significant quantities of immunocompetent mast cells in the human epiphysis define this endocrine organ as an important component of the unified neuroimmunoendocrine system of the body.