Proliferative activity of epidermal basal cells after wounding - AgNOR counts compared with bromodeoxyuridine reactivity in rats

Quantitative changes in nucleolus organizer regions (NORs) are known marker s of proliferation that can be demonstrated by a specific silver staining t echnique on paraffin-embedded sections. Wounding of skin induces proliferat ion of basal epidermal cells at the wound margin. The degree of proliferati on depends on the survival time and can be measured by morphometric assessm ent of argyrophilic NORs (AgNORs). Following incision wounding of the pinna e, rats were allowed to survive for different intervals (7 rats per interva l) up to 120 hours. Before each sacrifice, biopsies were taken and incubate d ill a bromodeoxyuridine (BrdU) solution, embedded in paraffin, and staine d with an antibody against BrdU. At the same time morphometric analysis of AgNOR counts was performed on sections made from the same material. BrdU in corporating nuclei were assessed by simple counting, whereas morphometric a nalysis of AgNOR counts was computer aided. Both methods revealed an increa se in the number of proliferating cells, a plateau phase being reached afte r about 36 hours, followed by a decline after about 70 hours. Both methods thus allowed a reliable temporal classification of the skin injury accordin g to survival time. The molecular background of the AgNOR changes in relati on to the proliferation of cellular elements is discussed in detail.