Characterization of astroglial cell proliferation in vitro and in vivo.

: On the basis of experimental set-ups in vitro and in vivo and by making use of specific autoradiographical techniques, the following data on the proliferation of astrocytes from newborn rats in vitro and unpretreated rats and mice in vivo could be obtained: (i) The commonly employed immunohistochemical staining techniques in vitro are not applicable in tissue sections. (ii) In vivo, astrocytes show increasing durations of cell cycle (tc) as well as S phase (ts) prenatally until about birth. A similar trend can be observed in vitro. However, the absolute values for ts and tc can be substantially modified depending on the culture conditions. (iii) As regards the mode of proliferation, astrocytes in vitro grow exponentially and without transition of quiescent cells from the non-growth fraction into the growth fraction (GF). In contrast, astrocytes in vivo exhibit steady-state growth and continuous recruitment of proliferating cells from the non-GF. These differences show that there is a need for further in vivo-experiments when studying new strategies in the treatment of gliomas.