Takahiko Hamasaki

BDNF, NT-3, and NGF released from transplanted neural progenitor cells promote corticospinal axon growth in organotypic cocultures.

Study Design. Experimental study of spinal cord injury using an organotypic slice culture. Objective. To clarify the mechanism of corticospinal axon regeneration following transplantation of neural progenitor cells (NPCs) in the injured spinal cord. Summary of Background Data. Several mechanisms underlying central nervous system regeneration after transplantation of NPCs have been proposed; however, the precise mechanism has not been clarified. Previously, we demonstrated that transplanted NPCs secreted humoral factors that in turn promoted corticospinal axon growth using the unique organotypic coculture system involving brain cortex and spinal cord from neonatal rats. Methods. Cultured NPCs were immunostained with antibodies against neurotrophic factors including brain-derived neurotrophic factor (BDNF), neurotrophin (NT)-3, nerve growth factor (NGF), and ciliary neurotrophic factor (CNTF) both before and after differentiation. To evaluate corticospinal axon growth quantitatively, we used the organotypic coculture system. The dissected brain cortex and spinal cord obtained from neonatal rats were aligned next to each other and cultured on a membrane. NPCs were transplanted onto the cocultures. Furthermore, neutralizing antibodies against BDNF, NT-3, NGF, or CNTF were added to the cocultures. Axon growth from the brain cortex into the spinal cord was assessed quantitatively using anterograde axon tracing with DiI. Results. The cultured NPCs were positively immunostained by antibodies against BDNF, NT3, NGF, and CTNF both before and after differentiation. Transplantation of NPCs promoted axon growth from the brain cortex into the spinal cord. The axon growth promoted by NPCs was significantly suppressed by the addition of neutralizing antibodies against BDNF, NT-3, and NGF but not CNTF. Conclusion. The neurotrophic factors, BDNF, NT-3, and NGF, secreted by transplanted NPCs, were involved in the promotion of corticospinal axon growth after transplantation of NPCs.

Plate-only open door laminoplasty maintains stable spinal canal expansion with high rates of hinge union and no plate failures.

Study Design. Prospective clinical series. Objective. To evaluate the ability of plate-only laminoplasty to achieve stable laminar arch reconstruction and to determine the rate and time course with which bony healing occurs in such constructs. Summary of Background Data. Reconstruction of a stable laminar arch with sufficient room for the decompressed spinal cord is a desired goal when performing cervical laminoplasty for myelopathy. Traditional forms of laminoplasty fixation, such as sutures, bone struts, and ceramic spacers, may be associated with complications including loss of fixation, dislodgement with neurologic compromise, and premature laminoplasty closure. Plates, in contrast, provide more rigid fixation. Plate-only laminoplasty is gaining popularity as a method of laminoplasty fixation, but there is little data on its effectiveness. Methods. Fifty-four patients who underwent open door laminoplasty for cervical myelopathy and had available postoperative computed tomography (CT) scans formed the basis of this study. In all cases, a 4-mm round burr was used to create the hinge at the junction of the lateral mass and lamina by completely removing the dorsal cortex and thinning the ventral cortex until a greenstick deformation of the hinge could be produced. Laminoplasty plates were used as the sole method of fixation. No supplemental bone graft struts were used on the plated side, and the hinge side was not bone grafted. Axial CT scans obtained at 3, 6, and 12 months postoperatively were assessed for plate complications and bony healing of the hinge. Results. No plate failures, dislodgements, or premature closures occurred in any of the levels at any time postoperatively. Computed tomography scan review demonstrated that 55% of levels were healed at 3 months, 77% at 6 months, and 93% at 12 months. At each timepoint, C6 and C7 had the highest hinge healing rates. Laminar screw backout was seen in 5/217 (2.3%) of levels, but was not associated with plate dislodgement, laminoplasty closure, or neurologic consequences, and did not occur in any case in which 2 laminar screws had been placed. Conclusion. Plate-only laminoplasty provided stable reconstruction of an expanded laminar arch with no failures, dislodgements, adverse neurologic consequences, or premature closures in 217 levels. Ninety-three percent of hinges demonstrated radiographic union at 12 months, and even those that did not heal by CT scan criteria maintained patent expansion of the spinal canal without adverse neurologic consequences. Supplemental bone graft does not appear necessary when plated laminoplasty is performed.

Prevalence of Physical Signs in Cervical Myelopathy : A Prospective, Controlled Study

Study Design. Prospective case-control study. Objective. To determine the prevalence and utility of commonly tested myelopathic signs in surgically treated patients with cervical myelopathy (CM). Summary of Background Data. Although physical signs are sought in making the diagnosis of CM, their importance remains unclear, as patients with CM may have normal examinations while those without CM can demonstrate “myelopathic” signs. Methods. Patients presenting with cervical complaints and advanced imaging were evaluated over a 6-month interval in a single surgical practice. The CM group consisted of those with (1) a history of myelopathic symptoms and (2) correlative spinal cord compression on imaging, who then (3) underwent surgery and (4) improved Nurick score by ≥1 grade after surgery. The controls consisted of patients with neck/radicular complaints but no myelopathic symptoms and no cord compression on imaging. Myelopathic signs included hyperreflexia or provocative signs (Hoffman inverted brachioradialis reflex, clonus, Babinski). Results. There were 39 CM patients and 37 controls. Myelopathic signs were more prevalent in the CM group (79% vs. 57%; P = 0.05), with significantly higher rates of all provocative signs but not hyperreflexia. Overall, myelopathic signs were not highly sensitive in diagnosing the presence of CM, as 21% of CM patients failed to demonstrate any myelopathic signs. There was no correlation between the presence of myelopathic signs and diabetes or preoperative Nurick score. However, those with cord signal changes were significantly more likely to demonstrate myelopathic signs. Conclusion. Although myelopathic signs are significantly more common in CM patients, they may be negative in approximately one-fifth and can not be relied on to make the diagnosis. In patients who lack myelopathic signs but otherwise seem myelopathic with no alternative explanations, symptoms combined with correlative imaging studies must be used to base treatment decisions, as the absence of signs does not preclude the diagnosis of myelopathy nor its successful surgical treatment.

Biomechanical assessment of minimally invasive decompression for lumbar spinal canal stenosis: a cadaver study.

Study Design A biomechanical study on the cadaveric human lumbar spine. Objective We focused on a biomechanical comparison of the changes wrought on motion segments after a minimally invasive decompression and after a conventional medial facetectomy. Summary of Background Data Minimally invasive posterior decompression using a microscope or an endoscope is becoming popular for elderly patients with lumbar spinal canal stenosis. An advantage of the technique is that the cauda equina and nerve roots are in clear view and the facet joints, paravertebral muscles, and spinous process are well preserved. Methods Eight human lumbar motion segments were used in this study. Each specimen was tested according to the following loading protocol: axial compression, flexion, extension, lateral bending to the right and to the left, and axial rotation to the right and to the left. This loading protocol was applied to each motion segment after the following surgical interventions: (1) left fenestration, (2) bilateral decompression via unilateral approach, (3) medial facetectomy, and (4) total facetectomy. The relative stiffness of the motion segments was determined and compared with a normalized stiffness for the specimen when intact. Results Bilateral decompression via unilateral approach produces less biomechanical effect in terms of stiffness changes as compared with medial facetectomy. Bilateral decompression leaves the spine more than 80% as stiff as the intact spine. Conclusions These results go toward supporting a minimally invasive bilateral decompression. Minimally invasive bilateral decompression, as opposed to a conventional medial facetectomy, preserves the facet joints as much as possible. Preserving the facet joints during the decompression should produce less postoperative instability.

Expansive laminoplasty for cervical myelopathy with interconnected porous calcium hydroxyapatite ceramic spacers: comparison with autogenous bone spacers.

Study Design Expansive cervical laminoplasties with interconnected porous calcium hydroxyapatite ceramic (IP-CHA) spacers were performed in cervical myelopathy patients. Objectives To evaluate the usefulness and osteoconductive capability of IP-CHA spacers in expansive laminoplasty. Summary of Background Data Expansive laminoplasty for cervical myelopathy is designed to preserve the posterior structures, so as to prevent postoperative development of instability and cervical kyphosis. The technique requires successful reconstruction of the laminae of vertebral arches, as sinking or nonunion of the expanded laminae may induce neurologic regression, segmental motor paralysis, and postoperative axial pain. A novel IP-CHA with sufficient biocompatibility and mechanical strength was developed as an artificial bone substitute. Methods Expansive open-door laminoplasties were performed in 88 cervical myelopathy patients, and both autogenous bone spacers harvested from the spinous processes and IP-CHA spacers in combination with bone marrow were alternately grafted into the opened side of each lamina. All patients were followed up with computerized tomography scans, and bonding rates for both the IP-CHA and autogenous spacers, bone fusion rates of the hinges of the laminae, and complications associated with the implants were examined. Results Clinical symptoms significantly improved in all patients without major complications related to the procedure. The IP-CHA spacers demonstrated comparable bone bonding to the autogenous spacers on postoperative computerized tomography scans. The expanded laminae withstood expanded positions without sinking or floating throughout the followups, and the hinges completely fused in more than 95% of patients in both groups within 1 year. Conclusions The IP-CHA spacer contributed to high bone fusion rates of the spacers and hinges of the laminae, and there were no complications associated with their use. Cervical laminoplasty with the IP-CHA spacers is a safe and simple method that yields sufficient fixation strength and provides sufficient bone bonding within a short period of time after operation.

Therapeutic effects with magnetic targeting of bone marrow stromal cells in a rat spinal cord injury model.

Study Design. Experimental rat animal study using a new cell delivery system. Objective. To investigate the therapeutic effects with magnetic targeting of bone marrow stromal cells (BMSCs) in a rat spinal cord injury (SCI) model. Summary of Background Data. Several methods to deliver therapeutic agents have been used for the treatment of SCI in animal studies. However, the most appropriate administration method for clinical application has not been established. Previously, we reported the development of a new cell delivery system using magnetic targeting. This system has potential as a clinical application for a minimally invasive and efficient transplant method in SCI. Methods. Contusion SCI was induced by placing a 25 g rod onto the spinal cord for 90 seconds in adult SD rats. A neodymium magnet was placed in the paravertebral muscles at the T7 level in the magnet group, whereas a nonmagnet metal was placed at the same spinal cord level in the nonmagnet group. Magnetically labeled BMSCs were injected into the subarachnoid space in both the magnet and nonmagnet group. Results. Aggregations of the BMSCs were detected on the surface of the injured spinal cord in the magnet group, whereas few BMSCs were observed in the nonmagnet group. Hindlimb motor function of the magnet group demonstrated significant improvement compared with that of the nonmagnet group. Conclusion. This cell delivery system may be a useful method for future clinical application in the treatment of SCI.

Chondroitinase ABC promotes corticospinal axon growth in organotypic cocultures

Study design:Organotypic coculture model using brain cortex and spinal cord of neonatal rats was used to test the effect of chondroitinase ABC (ChABC) on corticospinal axon growth.Objective:Chondroitin sulfate proteoglycan (CSPG) is neurite outgrowth inhibitory factor that combines with reactive astrocyte at the lesion site to form a dense scar that acts as a barrier to regenerating axons. ChABC is a bacteria enzyme that digests the glycosaminoglycan side chain of CSPG. We investigated the effect of ChABC on corticospinal axon growth quantitatively using the organotypic cocultures of brain cortex and spinal cord.Setting:Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University.Method:We used organotypic cocultures with neonatal brain cortex and spinal cord as an in vitro assay system for assessing axon growth. After administering ChABC, we counted the number of axons passing through a reference line running parallel to the junction between the brain cortex and spinal cord 500 and 1000 μm from the junction. The immunoreactivity of CSPG was assessed.Result:The average number of axons after ChABC administration was significantly greater than in the control group. Administration of ChABC decreased CSPG expression in this coculture system.Conclusion:ChABC induces axonal regeneration by degrading CSPG after central nerve system injury. ChABC has great potential for future therapeutic use in spinal cord-injured patients.

Spinal instrumentation for sacral-pelvic fixation: a biomechanical comparison between constructs ending with either S2 bicortical, bitriangulated screws or iliac screws.

Study Design A biomechanical study of 2 fixation techniques for lumbosacral fixation. Objective To evaluate 2 techniques, one using S1 screws combined with bicortical, bitriangulated (BCBT) S2 screws, and the other using S1 screws combined with iliac screws. Summary of Background Data Common to the 2 techniques of sacral-pelvic fixation is S1 pedicle screws; the difference lies between S2 screws versus iliac screws. Iliac screws are clinically effective, yet present clinical disadvantages that S2 screws can potentially obviate, for example, wide dissection, soft tissue coverage, crossing the sacroiliac joint, and interference with bone graft harvesting. In an effort to optimize S2 fixation, we have used a BCBT S2 technique. Methods Eight fresh human sacral-pelvic specimens were harvested (average age 78.7 y; bone density 0.75 g/cm2). Screws were placed bilaterally: (1) at S1: 7.5 mm diameter screws were placed bicortical; (2) at S2: 7.5 mm diameter by 60 mm long screws were placed bicortical and bitriangulated; (3) the ilium received 7.5 mm diameter by 80-mm-long screws. Sacral-pelvic constructs were assembled and biomechanical stiffness testing was performed. The stiffness in each loading mode was calculated. After the stiffness tests were completed, each BCBT S2 screw and each iliac screw were individually loaded to determine fixation strength of each type of screw. Results There was no significant difference in stiffness between the 2 constructs, although S1 and the BCBT S2 construct tended to be stiffer in all modes. However, for the fixation strength of screws, the iliac screws loosened at loads that were significantly greater than those for BCBT S2 screws (c.f. 435.9 N with 144.7 N). Conclusions Iliac screws maybe the better choice in cases with poor bone quality. However, the S1-BCBT-S2 screw construct is biomechanically an appropriate alternative to the S1-iliac screw construct and it presents clinical advantages.

Magnetically labeled neural progenitor cells, which are localized by magnetic force, promote axon growth in organotypic cocultures.

Study Design. An in vitro, rat animal study was conducted. Objective. To assess the corticospinal axon growth potential in varying concentrations of neural progenitor cells (NPCs) and in magnetically localized labeled NPCs, quantitatively using our original organotypic coculture system. Summary of Background Data. Transplantation of NPCs for spinal cord injury has been anticipated as a possible future treatment. It is important not only to illuminate the mechanism of NPCs for spinal cord injury, but also to develop an effective cell delivery system for clinical use. In order to develop more effective, efficient, and minimally invasive cell delivery systems, we established a new system using magnetic targeting. Methods. Magnetically labeled NPCs were suspended with activated magnetic beads and individual NPCs, and were compared the characterization to nonlabeled NPCs in vitro. We transplanted varying concentrations of 102, 103, 104, 105, and 106 NPCs in 1 &mgr;L medium to coculture models. Then the 104 labeled NPCs were transplanted with or without magnet to the cocultures. Results. Magnetically labeled NPCs had similar potential in axon growth compared with nonlabeled NPCs, so there were few toxic effects of magnetically labeling NPCs. The differential potentials were not changed whether they were localized or scattered in vitro. Corticospinal axon growth was promoted in accordance with the transplanted NPC numbers around the organotypic coculture. Localized labeled NPCs with a magnet promoted axon growth much more than scattered labeled NPCs without a magnet, so magnetically localized labeled NPCs expressed higher potential in axon growth. Conclusion. Magnetically labeled NPCs, which were localized by magnetic force, could promote axon growth in this organotypic coculture system.

Education-associated cortical glucose metabolism during sustained attention.

For many diseases and injuries of the central nervous system, transplantation of neural progenitor cells is being evaluated as a possible treatment option. Although local, intravenous and subarachnoid injections have been reported as administration methods of neural progenitor cells, each of these methods has limitations. More effective and minimally invasive cell delivery systems are necessary for transplanting neural progenitor cells. In this study, we have developed a technique to form magnetically labeled neural progenitor cells for a magnetic targeting system. We demonstrated that neural progenitor cells can couple with magnetic beads, and that the labeled neural progenitor cells preserve the characteristics of non-labeled neural progenitor cells, and that they can be localized by magnetic force in vitro. Labeled neural progenitor cells have the potential to be used in magnetic targeting systems in-vivo models.