Guided neurite elongation and Schwann cell invasion into magnetically aligned collagen in simulated peripheral nerve regeneration

High-strength magnetic fields were used to align collagen gel formed into 4 -mm-diameter rods during the self-assembly of type I collagen monomers into fibrils. We developed an in vitro assay to study neurite elongation into t he magnetically aligned collagen gel rods from dorsal root ganglia (DRG) ex plants placed onto one end of the rods. The depth of neurite elongation fro m chick embryo DRG neurons into these rods was found to be substantially gr eater than that observed in controls and increased with an increase in magn etic held strength, as did the collagen gel rod birefringence, indicative o f collagen fibril alignment along the rod axis. Moreover, the axial bias of neurite elongation became more pronounced with an increase in magnetic hel d strength, presumably due to a contact guidance response of growth cones a t the neurite tips. Coinvasion of Schwann cells from neonatal rat DRG was a lso studied in these assays using double immunolabeling. In the absence of serum, Schwann cells were highly associated with, and often trailed, elonga ting neurites. In the presence of serum, Schwann cells showed significantly higher rates of invasion and formed axially aligned chords reminiscent of bands of Bungner. These results may translate into an improved method of en tubulation repair of transected peripheral nerves by directing and stimulat ing axonal growth through a tube filled with magnetically aligned collagen gel, (C) 1999 Academic Press.