Growth of corticospinal axons on prosthetic substrates introduced into the spinal cord of neonatal rats.

Nitrocellulose implants treated with biological materials known to support neurite growth in vitro were introduced at thoracolumbar levels of the neonatal rat spinal cord before the arrival of growing corticospinal tract (CST) axons. Implant placement was designed to interrupt the normal CST growth path and provide a potential, alternative growth path. Subsequent growth of CST axons within the spinal cord in the vicinity of the implants was evaluated by labeling the axons with the anterograde transport of horseradish peroxidase. Untreated implants either blocked further CST axon growth or deflected CST axons to abnormal positions. Implants bearing living cells from spinal cord primary cultures were able to support the adhesion and growth of CST axons. Similarly, acellular implants coated with laminin, but not with poly-L-lysine supported the adhesion and growth of CST axons, suggesting that laminin or some other adhesive factor produced by immature neuroglial cells may be normally involved in CST axon growth and guidance.