Regeneration of hemisectioned spinal cords with and without supporting materials.

Nerve regeneration in hemisectioned spinal cords with and without supporting materials was examined in rats. Cell migration and newly formed capillaries surrounded by laminin-positive materials appeared at the lesioned site 7 days postoperatively. Reactive astrocytes increased at the lesioned site and extended into the spinal cord within 3 weeks. However, cell reactions decreased by 4 weeks and a cavity formed at the lesioned site in all animals. Regenerated axons were found only proximal to the lesioned site at 4 to 8 weeks. In the presence of supporting material (sciatic nerve containing proliferated Schwann cells or membrane filter), no cavity formed in the spinal cord and glial reactions were modest around the supporting material. Regenerated axons with growth cones were observed in the supporting material. However, no regenerated axons penetrated into the distal part of the spinal cord. Spinal cord axons can regenerate in the presence of supporting materials, but appropriate microenvironments, such as those found in the injured sciatic nerve, are required for spinal axons to traverse a lesion and penetrate into the spinal cord.