Immunohistochemical assessment of cellular proliferation in the developing human CNS using formalin-fixed paraffin-embedded material.

Assessment of cell proliferation in the developing human brain has been limited to counting mitotic cells, since the other procedures currently used for determination of the mitotic activity either depend on experimental manipulation of the tissue, e.g., labeling with radioactive thymidine precursors or with bromodeoxyuridine, or on frozen sections of the tissue, e.g., Ki-67 immunoreactivity. As most of the developing human brain material available is formalin fixed and paraffin embedded, these procedures are not practical. An immunohistochemical technique based on a monoclonal antibody directed against a proliferating cell nuclear antigen (PCNA) was used for detecting cellular proliferation in the developing human brain. Known progenitor cells in proliferating zones showed distinct PCNA-reactivity, but the method also revealed new areas of cell proliferation in fixed paraffin-embedded tissue blocks from the developing human brain.