Uncertain histological origin of "glia-like" cells in adult human brain tissue cultures.

Abstract

Most brain cells studies come from cultured rodent brain tissue, so basic questions about the behaviour of cultured adult human glial cells may remain unanswered. Cells cultured from adult human brain have been poorly defined until now and are often termed "glia-like" based on some morphological similarities with astrocytes. However, the cells in question fail to express glial markers and may be well be of non-glial origin. We examined adult human brain and cultures from 10 patients with non-malignant diagnoses. Immunofluorescence methods were used for glial and non-glial cell type identifications. Confluent cultures contained the following: 0.1 % astrocytes, ≤ 0.01 % oligodendrocytes, 2-5 % microglial and 95-98 % "glia-like" cells. Astrocytes tested as followed: GFAP+/Vim+, microglia: Ferr+Vim+, "glia-like" cells: Vim+/Fn+/CK- or CK+. In the brain tissue, astrocytes were GFAP+/Vim+, microglia Ferr+/Vim-, fibronectin expression was restricted to brain vessels. This report demonstrates considerable morphological and cytoskelatal dedifferentiation of cultured brain cells. Cytokeratins, specific markers for epithelial cell differentiation, were absent in the brain tissue. However, they were expressed in "glia-like" cells. This finding could be considered glial dedifferentiation given the ectodermal origin of the brain tissue. We suggest that "glia-like" cells come from currently unknown glial progenitor cells scattered through the brain tissue (Tab. 1, Fig. 4, Ref. 19).