Substrate-bound human recombinant L1 selectively promotes neuronal attachment and outgrowth in the presence of astrocytes and fibroblasts

Axonal pathfinding is a complex process that is mediated through cell-matri x and cell-cell interactions. A large number of studies have demonstrated t hat ECM and ECM-derived proteins and peptides are potent promoters of neuri te outgrowth, however much less attention is given to the fact that these s ame ligands also elicit responses in a wide variety of non-neuronal cell ty pes. We examined the use of a substrate-bound recombinant form of human LI, an integral membrane protein, as a ligand for bridging materials for repai ring the CNS by studying its effectiveness in promoting specific responses of neuronal cells in the presence of astrocytes and fibroblasts. LI, a cell adhesion molecule expressed in the developing CNS and PNS, has strong neur ite promoting activity, and contributes to axonal guidance and axonal fasci culation during development. In this study, substrates treated with L1-Fc w ere compared to subtrates treated with fibronectin and poly-lysine (PDL) wi th respect to their interaction with a variety of cell types, including thr ee types of neurons (DRG neurons, cerebellar granule neurons, and hippocamp al neurons), astrocytes, dermal fibroblasts, and meningeal cells. L1-Fc-tre ated substrates supported significantly higher levels of neurite outgrowth relative to fibronectin and PDL, while inhibiting the attachment of astrocy tes, meningeal cells, and fibroblasts. We also show that neuronal cells att ach to and extend neurites on 30 mum diameter L l-Fc-treated filaments as a n example of a potentially useful bridging substrate. The high level of bio logical specificity displayed by surface-bound L1, along with the fact that it is a potent promoter of neurite outgrowth, is normally expressed on axo ns and regulates axonal fasciculation during normal development bodes well for its use on bridging materials For the repair of the CNS, and suggests t hat cell adhesion molecules, in general, may be useful for biomaterial modi fication. Moreover, small diameter filaments coated with L1-Fc may function in an analogous way to pioneering axons that guide the growth of axons to distal targets during development. (C) 2001 Elsevier Science Ltd. All right s reserved.