Satoru Yoshii

Collagen filaments as a scaffold for nerve regeneration

This article describes repair of peripheral nerve defect using collagen filaments instead of tubes. Many tube-shaped nerve guides induce regeneration of severed peripheral nerve axons within a limited distance. Substantial regeneration of nerve axons has not been reported without a tubular conduit. Here we show the regeneration of peripheral nerve axons along filaments of collagen without a tube. Cables of collagen filaments were grafted to repair 20-mm defects of rat sciatic nerves. Nerve autografts and collagen tubes were grafted as controls. The mean number and the mean fiber diameter of regenerated myelinated axons were approximately 4800 and 3.3 microm in the distal end of the nerve autograft at 8 weeks postoperatively while in the distal end of the collagen-filaments nerve guide, they were approximately 5500 and 2.3 microm. Collagen tubes failed to bridge the nerve defect. Histologic studies suggest that nerve axons regenerated substantially along the collagen filaments.

Peripheral nerve regeneration along collagen filaments.

This paper describes the regeneration of severed peripheral nerve axons along collagen filaments without a tube. Two thousand collagen filaments were grafted to bridge 20 mm defects of rat sciatic nerve. The number of myelinated axons was approximately 4800 in the distal end of the nerve autograft at 8 weeks postoperatively; while in the collagen-filaments nerve guide it was 5500. The results suggested the collagen filaments guided regenerating axons effectively.

30 mm regeneration of rat sciatic nerve along collagen filaments.

This paper describes 30 mm regeneration of peripheral nerve axons along collagen filaments; 31-mm-long collagen filaments or collagen tube were grafted to bridge a 30-mm defect of rat sciatic nerve. The mean number and the diameter of regenerated myelinated axons were 330+/-227 and 2.7+/-0.9 microm at the distal end of the collagen-filaments 12 weeks postoperatively; while at the distal end of the tube no axon was found.

Bridging a Spinal Cord Defect Using Collagen Filament

Study Design. A rat model of spinal cord defect was designed to evaluate the effect of collagen filament implant on nerve regeneration in the spinal cord defect. Objectives. To bridge a spinal cord defect and restore the function in adult mammals. Summary of Background Data. Resection of the spinal cord in mammals is always followed by motor paralysis and loss of voluntary function below the lesion. Partial success in bridging the ends of the spinal cord after complete resection was reported. However, restoration of function has not been reported in adult mammalian. Materials and Methods. Four thousand collagen filaments 5-mm-long were grafted to bridge a 5-mm defect of rat spinal cord. Controls had their spinal cord defect left ungrafted after resection. At 1-week intervals, animals were evaluated functionally. After 4 and 12 weeks, animals were evaluated histologically. After 12 weeks, animals were evaluated electrophysiologically. Results. The severed spinal cord axons regenerated along the collagen filament implant crossing the proximal and distal spinal cord implant interfaces at 4 weeks after surgery. The rats with collagen filament grafts could walk, run, and climb with hind forelimb coordination at 12 weeks after surgery. Sensory-evoked potential waveform was found in the rats with collagen filament at 12 weeks after surgery. Conclusions. The collagen filaments support the axonal regeneration of the transected spinal cord and the restoration of function.

In vivo guidance of regenerating nerve by laminin-coated filaments

Laminin is reportedly an extremely potent neurite-promoting agent in vitro. We investigated the effect of laminin on regeneration of axons in vivo, using a cord of polyester filaments coated with laminin as a guide, replacing a 10-mm segment of the rat sciatic nerve. After 4 weeks the cross section of the nerve guide at its midportion was examined under an electron microscope. Many regenerated axons were seen in the laminin-coated group, whereas no axon was observed in the controls. We conclude that laminin guides the regeneration of axons in vivo.

Ependymoma of the spinal cord and the cauda equina region.

Ependymomas are the most common glial tumors of the spinal cord, including the conus medullaris, filum terminale, and cauda equina. This study involved eight ependymomas of the spinal cord encountered during a 29-year period (1968-1996). The male:female ratio was 1:1.7, and the mean age at diagnosis was 33.7 years (range, 13-55 years). The outcome was studied in relation to initial presentation, initial therapy, location of tumor, histology of tumor, and gender after a follow-up period ranging from 2-16 years (mean, 113 months). Complete removal was achieved in six patients. Two patients received postoperative irradiation after partial removal. Histological examination revealed a benign ependymoma in all patients. Patients undergoing gross total excision at initial operation had excellent or good outcomes. We conclude that ependymomas of the spinal cord should be removed completely, if possible. Spine surgeons should be aware of the disease, and magnetic resonance imaging should be used in its detection.

Effects of neurotrophic factors on nerve regeneration monitored by in vivo imaging in thy1-YFP transgenic mice

We evaluated sciatic nerve regeneration in thy1-YFP transgenic mice selectively expressing a fluorescent protein in their axons. Using in vivo imaging, we observed the dorsal cutaneous renervation of the hind paw for 8 weeks. Three to four weeks after the operation, the length of the regenerated nerve treated with NGF tended to be longer than that of the regenerated nerve treated with saline. Functional recovery was evaluated by a withdrawal response of the hind paw to mechanical stimuli. In NGF and GDNF groups, mice started to resume a mechanical response 4 weeks after the operation, earlier than in the saline control group. Histological and ultrastructural analyses showed that the density of unmyelinated axons in the regenerated nerve of the NGF group was larger than that of those in the saline group. These results indicate that NGF accelerated the regeneration of the sciatic nerve and thus that the monitoring of cutaneous nerve regeneration in the dorsal foot is useful to evaluate the regeneration of the sciatic nerve in vivo.

Nerve regeneration along collagen filament and the presence of distal nerve stump.

Abstract This article describes the regeneration of severed peripheral nerve axons along collagen filaments in the absenceof the distal nerve stump. 22-mm long nerve guides made of collagen filaments were sutured to the proximal ends of severed rat sciatic nerves. The distal ends of the guides were sutured to the distal stumps of the nerves in a group and not sutured in the other. Nerve autografts and collagen tubes were used as controls. At 8 weeks postoperatively, the mean number and the mean diameter of myelinated axons were 5491 ± 617 (mean ± SD) and 2.3 ± 1.3 µm at the distal ends of the collagen filaments nerve guides those the distal ends were sutured to the distal stumps of the nerves, while in the nerve autografts these were 4837 ± 604 and 3.3 ± 1.4 µm. These were 1992 ± 770 and 2.7 ± 1.2 µm at the distal ends of the collagenfilaments guides those the distal ends were not sutured to the distal stumps of the nerves, while in the nerve autografts these were 3041 ± 847 and 2.3 ± 1.1 µm. No axon was found at the distal ends of the collagen tubes. The results suggested that the contact guidance and the chemotaxis guided regenerating axons along the collagen filaments.

Novel Methods for Clinical Applications of Bioactive Ceramics

Bioactive ceramics in general have the characteristic of chemically binding to bone in vivo, but they are mechanically weaker than bioinert ceramics. Typical bioactive ceramics include tricalcium phosphate (TCP), calcium hydroxyapatite (HA), Bioglass, Ceravital, and an apatiteand wollastonite-containing glass-ceramic (AWGC). The mechanical strengths and chemical and biological properties in vivo vary considerably for the different materials; furthermore, for clinical applications, methods are required that can accommodate the different natures of the different materials. We have attempted some novel methods for clinical applications, and our results are reported here.

Myxomatous degeneration of the ligamentum flavum of the lumbar spine

Study design: Report of two cases of acute lumbar nerve root compression caused by myxomatous degeneration of the ligamentum flavum.Objective: To report a rare cause of acute lumbar nerve root compression.Setting: Orthopaedic department, Osaka, Japan.Summary of background data: Two patients, both 50-year-old men presenting with signs and symptoms suggestive of acute lumbar nerve root compression were found to have a ligamentum flavum mass. The masses were removed and the patients regained normal function postoperatively.Methods: To reveal the nature of the mass, histopathological studies were made. Continuous sections were prepared from the removed mass lesions. The sections were stained with hematoxylin and eosin, van Giesons stain, azan stain, periodic acid Schiff reaction, Alcian blue stain and von Kossas stain.Results: Histological examination revealed myxomatous degeneration of the ligamentum flavum. No elastic fibers were found at the degeneration site. Diffuse mucopolysaccharide deposition was found at the degeneration site, however, no cyst was found. Collagen fibers were not increased. Hypertrophy or ossification of the ligamentum flavum was not recognized in the sections. At a follow-up examination over 2 years later, the patients were free of symptoms and the findings of a neurological examination were normal.Conclusion: Two cases of myxomatous degeneration of the ligamentum flavum of the lumbar spine were reported, which have seldom been described as the cause of acute lumbar nerve root compression.Spinal Cord (2001) 39, 488–491.