Influence of Meningeal Cells on Cell Proliferation in the Cerebellum

Epithelial morphogenesis is dependent on the surrounding mesenchyme which, in addition to other influences, stimulates epithelial cell proliferation (review in Cunha et al., 1983, and this volume). We have previously deduced a similar role for the meninges, the mesenchyme surrounding the brain, of the cerebellum, because after destruction of meningeal cells in newborn rats and hamsters, the number of cerebellar granule cells becomes reduced by almost 20% in adult animals (Sievers et al., 1980, 1981a, b; Allen et al., 1981; Pehlemann et al., 1985a, b; v. Knebel Doeberitz et al., 1986). This proposal is supported by findings of Sensenbrenner and colleague (Barakat et al., 1981, 1982; Gensburger et al., this volume) who showed that, in vitro, addition of either meningeal cells or meningeal extracts increased and prolonged the proliferation of neuronal stem cells. In order to specify which brain cells are influenced by meningeal cells, we performed a cell-kinetic study on the proliferation and migration of cells in the cerebellar cortex with tritiated thymidine after destroying the meningeal cells in newborn rats.