Cultivation of neural EGF-responsive precursor cells.

We demonstrated that proliferation of dissociated neural E14 and E19 rat precursor cells could be induced by Long-EGF. Dividing EGF-responsive neural progenitor cells stimulated by Long-EGF formed spherical multicellular clusters (neurospheres) which may reach macroscopical size. We have studied the inner organization of cells in semithin sections and revealed that the cell population within the neurosphere is not uniform. These are original findings as other researchers did not process neurospheres histologically. Cells located in a central area possessed neuron-like morphology whereas peripheral cells where differentiated to a lesser degree. Generally, we have observed several apoptotic cells or apoptotic bodies per section. Moreover, the central portion of the neurosphere contained degenerating cells that probably die from worsened nutrition conditions in the large neurosphere. After plating the neurosphere in serum-supplemented medium, cells began to migrate radially from the edge of the neurosphere and differentiate. The cells lying in the vicinity to the cluster mimicked radial glia whereas the cells located at the periphery of the colony took morphology of astroglial cells. These observations suggest EGF-responsive neural precursor cells retained their ability to produce both neuronal and glial phenotypes after prolonged cultivation period.