Phil M.E. Waite

Transplantation of nasal olfactory tissue promotes partial recovery in paraplegic adult rats

Recent reports have highlighted the potential therapeutic role of olfactory ensheathing cells for repair of spinal cord injuries. Previously ensheathing cells collected from the olfactory bulbs within the skull were used. In humans a source of these cells for autologous therapy lies in the nasal mucosa where they accompany the axons of the olfactory neurons. The aim of the present study was to test the therapeutic potential of nasal olfactory ensheathing cells for spinal cord repair. Olfactory ensheathing cells cultured from the olfactory lamina propria or pieces of lamina propria from the olfactory mucosa were transplanted into the transected spinal cord. Three to ten weeks later these animals partially recovered movement of their hind limbs and joints which was abolished by a second spinal cord transection. Control rats, receiving collagen matrix, respiratory lamina propria or culture medium, did not recover hind limb movement. Recovery of movement was associated with recovery of spinal reflex circuitry, assessed using the rate-sensitive depression of the H-reflex from an interosseous muscle. Histological analysis of spinal cords grafted with olfactory tissue demonstrated nerve fibres passing through the transection site, serotonin-positive fibres in the spinal cord distal to the transection site, and retrograde labelling of brainstem raphe and gigantocellularis neurons from injections into the distal cord, indicating regeneration of descending pathways. Thus, olfactory lamina propria transplantation promoted partial restoration of function after relatively short recovery periods. This study is particularly significance because it suggests an accessible source of tissue for autologous grafting in human paraplegia.

Advances in Secondary Spinal Cord Injury: Role of Apoptosis

The outcome of spinal cord injury depends on the extent of secondary damage produced by a series of cellular and molecular events initiated by the primary trauma. This article reviews the evidence that secondary spinal cord injury involves the apoptotic as well as necrotic death of neurons and glial cells. Also discussed are the major factors that can contribute to cell death, such as glutamatergic excitotoxicity, free radical damage, cytokines, and inflammation. The development of innovative therapeutic strategies to reduce secondary spinal cord injury depends on an increased understanding of secondary injury mechanisms at the molecular and biochemical level. Such therapeutic interventions may include the use of antiapoptotic drugs, free radical scavengers, and anti-inflammatory agents. These could be targeted to block key reactions on cellular and molecular injury cascades, thus reducing secondary tissue damage, minimizing side effects, and improving functional recovery.

Trigeminal Sensory System

This chapter addresses the unique anatomy of the pathway for facial sensations, involving the trigeminal ganglion and its associated nuclei within the brainstem. The innervation of specialized cranial structures such as the teeth, tongue, oral and nasal mucosa, cornea, meninges, and conjunctiva are considered. This chapter will also address trigeminal mechanisms in clinically relevant conditions such as toothache, headache and trigeminal neuralgia including using advances in imaging techniques and resolution. Thus it is now possible to obtain functional MR images (fMRI) of the trigeminal pathway from ganglion to cortex. Magnetoencephalography (MEG) and fMRI techniques have provided more details on cortical organization in facial regions of both S1 and S2, while diffusion tensor imaging has been useful for visualizing trigeminothalamic pathways. Plasticity of the system after injury, its association with pain conditions, and the opportunities that this offers for training and rehabilitation, are further areas of current research that are discussed.

Somatotopic organization of vibrissal responses in the ventro-basal complex of the rat thalamus

1. The region of the ventro‐basal complex (VB) of the thalamus responding to movements of the whiskers has been mapped electrophysiologically in rats under either urethane or barbiturate anaesthesia.

The responses of cells in the rat thalamus to mechanical movements of the whiskers

1. The responses of single cells to mechanical movements of individual whiskers have been recorded from the ventro‐basal complex of the thalamus, in rats under urethane or barbiturate anaesthesia.

Survival and migration of human and rat olfactory ensheathing cells in intact and injured spinal cord

Increasing evidence indicates the potential of olfactory ensheathing cells (OECs) for treating spinal cord injuries. The present study compared proliferation and migration of adult rat and human OECs transplanted into the spinal cord of athymic (immunodeficient) rats. OECs were purified from the nasal lamina propria and prelabeled with a cytoplasmic dye. After OEC injection into the thoracic spinal cord, animals were perfused 4 hr, 24 hr, and 7 days later. Both rat and human OECs showed similar migration. Cells were seen leaving the injection site after 4 hr, and by 7 days both rat and human OECs had migrated approximately 1 mm rostrally and caudally within the cord (rat: 1,400 ± 241 μm rostral, 1,134 ± 262 μm caudal, n = 5; human: 1,337 ± 192 μm rostral, 1,205 ± 148 μm caudal, n = 6). Proliferation of transplanted OECs was evident at 4 hr, but most had ceased dividing by 24 hr. In 10 animals, the spinal cord was injured by a contralateral hemisection made 5 mm rostral to the transplantation site at the time of OEC transplantation. After 7 days, macrophages were numerous both around the injury and at the transplantation site. In the injured cord, rat and human OECs migrated for shorter distances, in both rostral and caudal directions (rat: 762 ± 118 μm rostral, 554 ± 142 μm caudal, n = 4; human: 430 ± 55 μm rostral, 399 ± 161 μm caudal, n = 3). The results show that rat and human OECs rapidly stop dividing after transplantation and have a similar ability to survive and migrate within the spinal cord of immunocompromised hosts. OECs migrated less in animals with a concomitant contralateral hemisection.

Responses in the rat thalamus to whisker movements produced by motor nerve stimulation

1. The effect of electrical stimulation of the motor nerve supplying the whiskers on the activity of single cells in the vibrissal region of the ventrobasal complex of the thalamus has been studied in rats under urethane anaesthesia.

Effects of human OEC-derived cell transplants in rodent spinal cord contusion injury

Numerous reports indicate that rodent olfactory ensheathing cells (OECs) assist in spinal cord repair and clinical trials have been undertaken using autologous transplantation of human olfactory ensheathing cells (hOECs) as a treatment for spinal cord injury. However, there are few studies investigating the efficacy of hOECs in animal models of spinal cord injury. In this study hOECs were derived from biopsies of human olfactory mucosa, purified by culture in a serum-free medium containing neurotrophin-3, genetically labelled with EGFP, and stored frozen. These hOEC-derived cells were thawed and transplanted into the spinal cord injury site 7 days after a moderate contusion injury of the spinal cord at thoracic level T10 in the athymic rat. Six weeks later the animals receiving the hOEC-derived transplants had greater functional improvement in their hindlimbs than controls, assessed using open field (BBB scale) and horizontal rung walking tests. Histological analysis demonstrated beneficial effects of hOEC-derived cell transplantation: reductions in the volume of the lesion and the cavities within the lesion. The transplanted cells were located at the periphery of the lesion where they integrated with GFAP-positive astrocytes resulting in a significant reduction of GFAP staining intensity adjacent to the lesion. Although their mechanism of action is unclear we conclude that hOEC-derived cell transplants improved functional recovery after transplantation into the contused spinal cord, probably by modulating inflammatory responses and reducing secondary damage to the cord.

Axonal Injury in Children after Motor Vehicle Crashes: Extent, Distribution, and Size of Axonal Swellings Using β-APP Immunohistochemistry

The brains of 32 children (3 months to 16 years) who died as a result of motor vehicle collisions were examined for axonal injury using beta-APP immunohistochemistry. The extent and distribution of axonal injury was assessed and quantified throughout the forebrain, brainstem and cerebellum. The mean diameter of immunoreactive axons in the corpus callosum was measured for this pediatric group and, for comparison, a small adult sample. beta-APP immunoreactivity was seen in 14 pediatric cases (survival 35 mins to 87 h), most frequently in the parasagittal white matter (12/14), the corpus callosum (11/14), the brainstem (10/14) and cerebellum (9/14). In 2 cases, axon swelling was visualized in the internal capsule after only 35-45-min survival, earlier than has previously been reported. No immunoreactivity was seen in the remaining 18 cases who died within 1 h. The extent and distribution of axonal injury throughout the brain showed a rapid early increase with increasing survival time and then a slower progression. The diameter of individual callosal axons increased with increasing survival times, rapidly over the first 24 h and then more slowly. There was no statistical difference (p < 0.05) for callosal axon diameters at different survival times between the children and the adults sampled here. The extent and distribution of axonal injury throughout the brain appears to be similar in children to that previously reported in adults. The spatial and temporal spread of axonal damage suggests there may be therapeutic potential for the process to be arrested or slowed in its early stages.

Intra-axonal neurobiotin™ injection rapidly stains the long-range projections of identified trigeminal primary afferents in vivo: comparisons with HRP and PHA-L

Currently available methods for studying the morphology of physiologically characterized primary afferents are limited by difficulties inherent in impaling thin fibers and by the limited distances over which conventional tracers move during the course of a recording session. We have encountered an alternative method that overcomes these limitations. Neurobiotin (NB; Vector) injections into rat trigeminal (V) primary afferents in the brain stem or V ganglion provided rapid, long-range staining with recording and electrophoretic parameters that are commonly used to eject horseradish peroxidase (HRP) or Phaseolus vulgaris leucoagglutinin (PHA-L). When NB was injected into brain stem fibers responsive to vibrissal deflection with A-beta conduction velocities, collaterals were darkly stained in each of the 4 V subnuclei, as well as the cervical dorsal horn. Labeled fibers were also seen in the V root and peripherally in the infra-orbital nerve for a distance up to 15 mm from the injection site (30 mm total). Cell bodies in the ganglion were never labeled. When NB was injected into V ganglion cells with low- or high-threshold receptive fields and A-beta or A-delta conduction velocities, parent axons were stained in the V spinal tract to the level of the obex, and collaterals were visible in each of the 4 V subnuclei. Such long-range staining occurred within 4 h of tracer injection. HRP never stained brain stem fibers following ganglion cell injections and, when injected centrally with the same survival intervals used with NB, dark staining was limited to within 4 mm of the injection site. Unlike NB or HRP, PHA-L injections rarely produced useful data, either because of the high mortality accompanying attempts to achieve a 1-2 week survival period or because injected neurons were not recovered. Due to its rapid and robust transport, NB is a more convenient and reliable tracer than PHA-L for producing long-range staining of the projections of identified ganglion cells. Intracellular injection of NB also produces rapid Golgi-like staining of fibers over much greater distances than HRP under equivalent staining parameters.