Neuron-schwann cell interaction in basal lamina formation

The availability of tissue culture systems that allow the growth of nerve cells, Schwann cells, and fibroblasts separately or in various combinations now makes possible investigation of the role of cell interactions in the development of the peripheral nervous system. Using these systems it was earlier found that basal lamina is formed on the Schwann cell surface in cultures of sensory ganglion cells and Schwann cells without fibroblasts. It is here reported that the presence of nerve cells is required for the generation of basal lamina on the Schwann cell plasmalemma. Utilizing nerve cell-Schwann cell preparations devoid of fibroblasts, this was found in the following ways. (1) When nerve cells are removed from 3- to 5-week-old cultures, the basal lamina disappears from Schwann cells. (2) If nerve cells are added back to such Schwann cell populations, Schwann cell basal lamina reappears. (3) Removal of nerve cells from older (3-4 months) cultures does not lead to basal lamina loss; areas presumed not to have been coated with lamina before neurite degeneration remain so, suggesting that the lamina persists but is not reformed. (4) If basal lamina is removed with trypsin, it is reformed in neuron plus Schwann cell cultures but not in Schwann cell populations alone. Thus, the formation but not the persistence of Schwann cell basal lamina requires the presence of nerve cells.