Cellular channels during development and after peripheral nerve injury are
thought to provide guidance cues to growing axons. In tissue culture where
these cues are absent, neurites from dorsal root ganglion neurons grow with
a radial distribution. To induce directional axonal growth and to enhance
the rate of axonal growth after injury, we have designed microfilaments of
poly(L-lactide). We demonstrate that dorsal root ganglia grown on these fil
aments in vitro extend longitudinally oriented neurites in a manner similar
to native peripheral nerves. The extent of neurite growth was significantl
y higher on laminin-coated filaments compared with uncoated and poly-L-lysi
ne-coated filaments. As high as 5.8 +/- 0.2 mm growth was observed on lamin
in-coated filaments compared with 2.0 +/- 0.2 mm on uncoated and 2.2 +/- 0.
3 mm on poly-L-lysine-coated filaments within 8 days. Schwann cells were fo
und to grow on all types of filaments. They were, however, absent in the le
ading edges of growth on laminin-coated filaments. Photolysis of Schwann ce
lls caused a significant reduction in the neurite length on all types of fi
laments. Laminin-coated filaments, however, induced significantly longer ne
urites compared with uncoated and/or poly-L-lysine-coated filaments even in
the absence of Schwann cells. Our results suggest that laminin-coated poly
(L-lactide) filaments are suitable for inducing directional and enhanced ax
onal growth. Implants designed by arranging these microfilaments into bundl
es should aid regenerating axons by providing guidance cues and channels to
organize matrix deposition, cell migration, axon growth, and improve funct
ional recovery. (C) 2000 John Wiley & Sons, Inc.