ADDITION OF PURIFIED BASAL LAMINA MOLECULES ENABLES SCHWANN-CELL ENSHEATHMENT OF SYMPATHETIC NEURITES IN CULTURE

Our aim was to determine the effect of purified basal lamina component s on the differentiation of non-myelin-forming Schwann cells accompany ing rat sympathetic neurons in culture. Previous work has demonstrated that Schwann cells contacting superior cervical ganglion neurons cult ured in the presence of ascorbate and serum fail to effectively deposi t matrix and ensheathe neurites unless fibroblasts are also present. W e questioned if an increase in the amount of available basal lamina co mponents could mimic fibroblast-induced Schwann cell differentiation. Superior cervical ganglion neuron plus Schwann cell cultures were supp lemented with purified basal lamina molecules for up to 7 weeks. The a ddition of laminin, type IV collagen, heparan sulfate proteoglycan, or a combination of all three components, led to increased basal lamina deposition and increased neurite ensheathment compared with cultures w ith no additions. In long-term cultures receiving component additions, however, ensheathment was exaggerated, and the Schwann cells were hyp ertrophic. The ensheathing conformations adopted by these Schwann cell s surpassed normal-appearing ensheathment and resembled more unusual u nmyelinated nerve morphology found in vivo by others in normal senesce nce and in several peripheral neuropathies. These experiments show tha t increased availability of exogenous basal lamina components leads to increased basal lamina deposition and that basal lamina elaboration c an have dramatic effects on the morphology of nonmyelinating Schwann c ells. These findings suggest that influences of extracellular matrix s hould be considered when unusual Schwann cell/axon conformations are s een in vivo. (C) 1995 Academic Press, Inc.