"Glia-like" cells of fibroblast morphology are present in cultures from injured human brain tissue.

OBJECTIVE: Astrocytes undergo morphological and molecular changes in response to numerous pathological conditions. BACKROUND: Increased expression of glial fibrillary acidic protein (GFAP) has been reported as a characteristic feature of reactive astrocytes. However, GFAP-positive cells occur rarely in adult human brain cultures. These cultures are mostly composed of flat GFAP-negative "glia-like" cells, which remain poorly characterized in relation to reactive astrogliosis. METHODS: We examined the cultures from macroscopically injured and normal brain tissue from patients with brain trauma, gliomas, or brain metastases. Immunofluorescence and immunohistochemical methods were used for reactive astrocytes detection. RESULTS: The intensity of GFAP-positive staining was higher in reactive astrocytes in the brain tissue surrounding gliomas or metastases and lower in brain tissue damaged by traumatic injury. We did not observe any correlation between GFAP-positive reactive astrocytes in cultures and brain tissue. However, we found rapidly proliferating spindle-shaped cells in cultures prepared from injured brain tissue. CONCLUSION: Present data demonstrate the unexplained phenomenon of disparate cell morphologies in cultures when prepared either from macroscopically normal or injured human brain tissue. While normal cultures are mainly comprised of flat cells, the cultures from severely damaged brain tissue may be entirely composed of spindle-shaped cells usually classified as fibroblasts. We suggest that this spindle-shaped cellular morphology is not specific for fibroblasts, but it rather can be interpreted as the most favorable shape for rapid cell proliferation under culture conditions. After brain trauma, unknown processes may be triggered, such as induced cell proliferation which can be revealed under culture condition. Accordingly, we conclude that spindle-shaped cells are activated precursors of glial cells (Fig. 3, Ref. 15).

Astroglial differentiation of fibronectin­positive human "glia-like" cells.

OBJECTIVES: Fibronectin (Fn) is a glycoprotein of extracellular matrix produced by a variety of mesenchymal and neoplastic cell types. BACKGROUND: In adult brain tissue, Fn is restricted to blood vessels. However, adult human brain cultures are almost entirely comprised of flat or spindle­shaped Fn-positive cells usually referred to as "glia-like" cells. Since Fn is primarily present in fibroblasts, these cultures may be considered to be of non-glial origin. METHODS: Cells gained by long-term culturing of adult human brain tissue derived from brain biopsies obtained from 12 patients with non-malignant diagnoses were examined by immunofluorescence methods. RESULTS: Primary cultures contained GFAP-/Vim+/Fn+ "glia-like" cells (95-98 %) and GFAP+/Vim+/Fn- astrocytes (0.1 %) which disappeared by passage number 3. The formation of cell processes and enlargement of cell bodies was observed in 9 of 12 cultures with decreased cell growth during passages 12 to 17. It is remarkable that during this period, all "glia-like" cells became GFAP+/Vim+/Fn+. CONCLUSION: Herein, we confirm our previously published hypothesis about the origin of adult human "glia-like" cells, which we consider to be precursor cells scattered through the brain cortex and subcortical white matter. Cultures were comprised entirely of GFAP-/Fn+ "glia-like" cells and showed morphological and immunochemical astroglial differentiation with spontaneously decelerated growth during prolonged passaging. We propose that the adult human brain tissue contains a "dormant population" of undefined glial precursor cells. Under culture, these cells show to have a high proliferative capacity and different stages of cell dedifferentiation (Fig. 2, Ref. 21).

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

OBJECTIVES: 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. BAGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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).