Effects of dorsal column demyelination on evoked potentials in nucleus gracilis

Forced Remyelination Promotes Axon Regeneration in a Rat Model of Spinal Cord Injury

Spinal cord injuries result in the loss of motor and sensory functions controlled by neurons located at the site of the lesion and below. We hypothesized that experimentally enhanced remyelination supports axon preservation and/or growth in the total spinal cord transection in rats. Multifocal demyelination was induced by injection of ethidium bromide (EB), either at the time of transection or twice during transection and at 5 days post-injury. We demonstrated that the number of oligodendrocyte progenitor cells (OPCs) significantly increased 14 days after demyelination. Most OPCs differentiated into mature oligodendrocytes by 60-90 dpi in double-EB-injected rats; however, most axons were remyelinated by Schwann cells. A significant number of axons passed the injury epicenter and entered the distant segments of the spinal cord in the double-EB-injected rats. Moreover, some serotoninergic fibers, not detected in control animals, grew caudally through the injury site. Behavioral tests performed at 60-90 dpi revealed significant improvement in locomotor function recovery in double-EB-injected rats, which was impaired by the blockade of serotonin receptors, confirming the important role of restored serotonergic fibers in functional recovery. Our findings indicate that enhanced remyelination per se, without substantial inhibition of glial scar formation, is an important component of spinal cord injury regeneration.

The effects of glucocorticoids on neuropathic pain: a review with emphasis on intrathecal methylprednisolone acetate delivery

Methylprednisolone acetate (MPA) has a long history of use in the treatment of sciatic pain and other neuropathic pain syndromes. In several of these syndromes, MPA is administered in the epidural space. On a limited basis, MPA has also been injected intrathecally in patients suffering from postherpetic neuralgia and complex regional pain syndrome. The reports on efficacy of intrathecal administration of MPA in neuropathic pain patients are contradictory, and safety is debated. In this review, we broadly consider mechanisms whereby glucocorticoids exert their action on spinal cascades relevant to the pain arising after nerve injury and inflammation. We then focus on the characteristics of the actions of MPA in pharmacokinetics, efficacy, and safety when administered in the intrathecal space.

Remyelination, axonal sparing, and locomotor recovery following transplantation of glial-committed progenitor cells into the MHV model of multiple sclerosis

The behavior and myelinogenic properties of glial cells have been well documented following transplantation into regions of focal experimental demyelination in animal models. However, the ability of glial cell preparations to remyelinate in such models does not necessarily indicate that their transplantation into demyelinated lesions in clinical disease will be successful. One of the precluding factors in this regard is a greater understanding of the environmental conditions that will support transplant-mediated remyelination. In this study, we determined whether the complex and reactive CNS environment of the mouse hepatitis virus (MHV) model of multiple sclerosis (MS) could support transplant-mediated remyelination. Striatal neural precursors derived from postnatal day 1 mice were committed to a glial cell lineage and labeled. Immunohistochemical staining indicated that this population generated >93% glial cells following differentiation in vitro. Transplantation of glial-committed progenitor cells into the T8 spinal cord of MHV-infected mice demonstrating complete hindlimb paralysis resulted in migration of cells up to 12 mm from the implantation site and remyelination of up to 67% of axons. Transplanted-remyelinated animals contained approximately 2× the number of axons within sampled regions of the ventral and lateral columns as compared to non-transplanted animals, suggesting that remyelination is associated with axonal sparing. Furthermore, transplantation resulted in behavioral improvement. This study demonstrates for the first time that transplant-mediated remyelination is possible in the pathogenic environment of the MHV demyelination model and that it is associated with locomotor improvement.

Under one roof: the Miami Project to Cure Paralysis model for spinal cord injury research

Concentrating a wide range of spinal cord injury (SCI) research laboratories in a single location to accelerate progress and draw attention to the promise of SCI research has made The Miami Project to Cure Paralysis one of the most publicly recognized and often controversial research groups in the neurosciences. A "Center of Excellence" at the University of Miami School of Medicine, the Miami Project also serves as a model for SCI research programs being developed nationally and internationally. Founded in 1985, the Miami Project set out on an unprecedented path-to develop a research center dedicated to improving treatments for SCI by bridging basic and clinical science. In doing so, neurosurgeon Barth Green, M.D., enlisted not only a multidisciplinary team of scientists but also a devoted following of financial donors and volunteer research subjects, and support from the University of Miami and Florida legislature. Highly visible spokespersons, including cofounder ex-Miami Dolphin Nick Buoniconti and his son Marc, brought the issue of SCI paralysis and the promise of research before the public, the media, and sports communities. As progress in the neurosciences has raced ahead, public attention to medical research, and SCI research in particular, has grown exponentially. This review will assess the Miami Project as a model for disease-based research that unites academic, philanthropic, and patient communities in a common cause.

Schwann cells are removed from the spinal cord after effecting recovery from paraplegia

Remyelination of the CNS is necessary to restore neural function in a number of demyelinating conditions. Schwann cells, the myelinating cells of the periphery, are candidates for this purpose because they have more robust regenerative properties than their central homologs, the oligodendrocytes. Although the ability of Schwann cells to remyelinate the CNS has been demonstrated, their capacity to enter the adult spinal cord in large numbers and effect functional recovery remains uncertain. We used cholera toxin B-subunit conjugated to saporin to demyelinate the rat lumbar spinal cord, remove macroglia, and produce paraplegia. After the removal of oligodendrocyte and astrocyte debris by invading macrophages, there was a spontaneous entry of Schwann cells into the spinal cord, along with axonal remyelination and concomitant functional recovery from paraplegia occurring within 75 d. The Schwann cells appeared to enter the dorsal funiculi via the dorsal root entry zone and the lateral funiculi via rootlets that had become adherent to the lateral spinal cord after the inflammation. In the following weeks, Schwann cell myelin surrounding central axons was progressively replaced by oligodendrocyte myelin without lapse in motor function. Our results show that endogenous Schwann cells can reverse a severe neurological deficit caused by CNS demyelination and enable later oligodendrocyte remyelination.