Unexpected presence of cytokeratins in human "glia-like" cells

To demonstrate the unexpected features of the predominant cell population in adult human brain tissue cultures usually termed "glia-like" cells.

Cytokeratins (CK) are intermediate filaments (IF) specific for normal and neoplastic epithelial cell differentiation.

We examined adult human brain tissue cultures and cryosections prepared from ten biopsies. Immunofluorescence staining with monoclonal antibodies against IF proteins: anti-pan CK, glial fibrillary acidic protein (GFAP) and vimentin was performed on primary and secondary cultures up to passage 10.

In primary cultures we detected only small numbers of immunocytochemically distinct astrocytes, oligodendrocytes and microglial cells. "Glia-like" cells were negatively stained with specific glial marker antibodies. They were positively stained with pan-CK antibodies in 8/10 cultures where 0.1 % to 70 % CK-positive cells were present in primary as well as in secondary cultures. Comparative immunofluorescence IF staining for CK, GFAP and vimentin showed differences in the cytoplasmatic distribution of IF fibres, numbers of positive cells and intensities of staining. Cryosections from brain biopsies stained negatively with pan-CK antibodies.

These findings demonstrate the presence of CK in adult human brain cultures which is not caused by cross-reactivity of IF antibodies. Based on these results we propose that unexpected CK expression in human "glia-like" cells is due to cell dedifferentiation under culture conditions (Tab. 1, Fig. 2, Ref. 24).