GLIAL FIBRILLAR ACIDIC PROTEIN (GFAP)-POSITIVE NEURONS IN HUMAN POSTOPERATIVE NEOCORTICAL BRAIN SAMPLES

Glial fibrillar acidic protein (GFAP) is known to be selectively expressed in astroglial cells. However, it can be detected in the blood of patients suffering from several neurodegenerative diseases including traumatic brain injury (TBI) and Alzheimer’s disease (AD). As in post mortem samples of TBI patients, GFAP-positive cells with neuronal morphology were observed in the human neocortex. We made peroxidase-based immunostaining against GFAP in 145 postoperative human neocortical samples derived from tumour and/or epileptic patients and found neuron-like cells in 41 samples. They were also present in organotypic slice cultures (n=15) prepared from these tissues (n=27), and showed different morphology. Pyramidal-like neurons with dark nucleus and long dendrites, cells with inhibitory interneuron morphology, as well as cells with pale cytoplasmic staining were observed. Immunofluorescent staining combining GFAP with the neuronal markers NeuN and neurofilament-L (NFL) provided evidence for the neuronal identity of these cells. Correlation could not be demonstrated between the presence of GFAP+ neurons and gender, age, aetiology, lobe of origin, possible TBI events or AD. The hypotheses, i.e. either neurons start to express GFAP, or the NFL changes its conformation in the way that the antibody against GFAP recognizes it, have to be answered with further experiments. The factors initiating the appearance of GFAP-positive neurons might be linked to neurodegenerative diseases and remain to be identified.