The human amnion consists of the epithelial cell layer and underlying connective tissue. After removing the epithelial cells, the resulting acellular connective tissue matrix was manufactured into thin dry sheets called amnion matrix sheets. The sheets were further processed into tubes, amnion matrix tubes (AMTs), of varying diameters, with the walls of varying numbers of amnion matrix sheets with or without a gelatin coating. The AMTs were implanted into rat sciatic nerves. Regenerating nerves extended in bundles through tubes of 1-2 mm in diameter and further elongated into host distal nerves 1-3 weeks after implantation. Morphometrical analysis of the regenerated nerve cable at the middle of each amnion matrix tube 3 weeks after implantation was performed. The average numbers of myelinated axons were almost the same (ca. 80-112/10(4) microm(2)) in AMTs of 1-2 mm in diameter, as in the normal sciatic nerve (ca. 95/10(4) microm(2)). No myelinated fibers were found in AMTs composed of multiple thin tubes of 0.2 mm in diameter. The myelinated axons were thinner in implanted tubes than those in the normal sciatic nerve. The rate of occurrences of myelinated axons less than 4 microm in diameter was significantly higher in the AMTs, whereas axons in the normal sciatic nerve were diverse in distribution, with the highest population at 8-12 microm in diameter. Reinnervation to the gastrocnemius muscle was demonstrated electrophysiologically 9 months after implantation. It was concluded that the extracellular matrix sheet from the human amnion is an effective conduit material for peripheral nerve regeneration.

Muscle segments excised from rabbit biceps femoris muscles were treated with detergent sodium dodecyl sulphate to denature cellular constituents, and each was autografted in a 5 cm gap of the sciatic nerve in the same rabbit. Axonal regrowth through the grafts and reinnervation into the host sciatic nerves and muscles were studied morphologically, and electrophysiologically, 4 months after grafting. Regenerating axons accompanied by Schwann cells extended through basal lamina tubes of the grafts into the distal host nerves. Reinnervation of the tibialis anterior muscles by motor nerves was confirmed by recovery of the compound muscle action potentials (CMAP) and the reinnervation of the muscle spindles was demonstrated by electron microscopy. These findings indicated that the basal lamina tubes of denatured muscles were effective scaffolds through which the regenerating nerve fibers grew across as large a gap as 5 cm.

A biodegradable copolymer of poly L-lactic acid and epsilon-caprolactone (PLAC) was manufactured into a tube, in which a denatured skeletal muscle segment was placed longitudinally. This model tube was implanted as a guide to promote nerve regeneration across a 5 cm gap in the rabbit sciatic nerve. Five months after implantation, good nerve regeneration was found throughout the graft and in the distal host nerve. The population (29.6/16 x 10(2) microm(2)) of regenerated nerves in the graft was higher than that of the contralateral normal sciatic nerve (18.0/16 x 10(2) microm(2)). Regenerated nerve fibers extended to the distal host nerve. The number of myelinated fibers was 13.7/16 x 10(2) microm(2) at a level 1.5 cm from the distal suture. The diameters (below 2 microm) of most regenerated myelinated (nerves in the graft and in the distal host nerve were much smaller than those (6-8 microm) of normal nerves. Electrophysiological evaluation showed that the hindlimb muscle (gastrocnemius) was innervated by motor nerves in all animals 5 months after implantation. These results indicate that the PLAC tube with a denatured muscle segment inside provided good conditions for nerve fiber regrowth. The PLAC tube is thought to protect the denatured muscle segment from rapid dissociation in the host tissue.

The basal laminae of muscle fibers, when treated by denaturing methods including freeze thawing, have been used as conduits for regenerating nerves. In this study, we developed a new method for denaturing skeletal muscle fibers through treatment with a biological detergent, sodium dodecyl sulfate. Laminin and type IV collagen proteins of muscle fiber basal laminae were preserved after the detergent treatment. A segment of detergent-denatured muscle was grafted to a 1-cm defect of the rat sciatic nerve. One week after grafting, regenerating axons immunostained for neurofilaments were seen extending within laminin-positive muscle fiber basal lamina tubes. Four weeks after grafting, numerous myelinated axons at a much higher level than the control unoperated sciatic nerve, were found in the middle of the graft. They were smaller in diameter than those in the control nerve. Distal host nerves were well reinnervated 4 weeks after grafting. These findings suggest that the basal laminae of detergent-denatured muscle fibers provide effective conduits for regenerating axons.

The subventricular zone (SVZ) of the lateral ventricle of the mammalian forebrain is the major site in which neural progenitor cells (NPC) persist in the adult brain. The NPC are located beneath ventricular ependymal cells and have the capacity to self-renew and continuously produce neurons and glial cells. We have shown previously that neurospheres can be obtained from the brain of deceased adult rats and that neurosphere cells survive after transplantation into the spinal cord. In the present study, we investigated whether fresh NPC from living adult rats can survive and be integrated into host tissues after transplantation into the adult rat spinal cord of the same strain. We used rats expressing transgenic green fluorescent protein (GFP) as a donor to identify the transplanted NPCs. The SVZ tissues were obtained from the striatal wall of the lateral ventricle of adult GFP-rats and were grafted into lesions of the spinal cord at the cervical level. Two to 3 weeks after grafting, NPC migrated through the host tissue 0.5-1 mm away from the implantation site, and were integrated into the white matter of the host spinal cord. Surviving NPC exhibited immunohistochemical phenotypes of astrocytes (glial fibrillary acidic protein), but not for neurons (alpha-tubulin III) or oligodendrocytes (Rip; Hybridoma Bank, Iowa City, IA, USA). Thus, NPC from the SVZ of adult rats can survive and differentiate into at least astrocytes, which can then be integrated into host tissue after transplantation into spinal cord lesions in the adult rat.