Advances and strategies for spinal cord regeneration

Modelo experimental de lesão medular e protocolo de avaliação motora em ratos wistar

OBJETIVOS: Determinar modelo de contusão medular padronizado e método de avaliação motora em ratos com quadro de paraplegia. MÉTODOS: Utilizados 20 ratos Wistar divididos em quatro grupos, diferenciado o nível de gravidade da lesão raquimedular; realizadas lesões intermediárias padronizadas, através do sistema "MASCIS IMPACTOR" (Multicenter Animal Spinal Cord Injury Study): grupo 1 - 12,5 mm (lesão leve); grupo 2 - 25 mm (lesão moderada); grupo 3 - 50 mm (lesão grave); grupo 4 - animais que não sofreram lesão (grupo controle). Após 48 horas foi avaliada função motora, segundo escala proposta por Basso, Beattie e Bresnahan. RESULTADOS: Utilizando o modelo, notamos que as contusões leves (12,5mm de altura) foram efetivas, e os animais apresentaram infecção urinária na fase aguda uma semana após a contusão. As contusões intermediárias (25 mm de altura) foram efetivas, os animais apresentaram infecção urinária até duas semanas após a contusão. As contusões graves (50mm de altura) foram efetivas, os animais apresentaram infecção urinária durante três a quatro semanas e autofagia. CONCLUSÃO: O modelo de lesão medular utilizando o sistema MASCIS IMPACTOR e a avaliação funcional proposta por Basso, Beattie e Bresnahan é reprodutível, podendo ser utilizada, propiciando troca de informações entre os diferentes pesquisadores.

Real-time monitoring of mitochondrial NADH and microcirculatory blood flow in the spinal cord

STUDY DESIGN

We developed a real-time, in vivo monitoring system for the evaluation of spinal cord viability in rats during spinal cord ischemia.

OBJECTIVE

The aim of the present study was to apply a real-time multiparametric monitoring system in a rat spinal cord model exposed to ischemia or mechanical compression.

SUMMARY OF BACKGROUND DATA

The evaluation of spinal cord integrity during spine surgeries is highly important, as it enhances the potential to prevent secondary irreversible damage to the spinal cord tissue. Mitochondrial NADH redox state is the most sensitive parameter for tissue oxygenation state and, together with microcirculatory blood flow, can estimate the metabolic status of the spinal cord tissue.

METHODS

We applied the Tissue Vitality Monitoring System (TVMS) that includes optical fibers for the simultaneous monitoring of the spinal cord blood flow (SCBF) using laser Doppler flowmetry, and the mitochondrial NADH fluorescence using the fluorometric technique. Additionally, systemic arterial blood pressure was measured. Two models involving the interruption of the spinal blood flow were tested: the occlusion of the abdominal aorta (ischemia) and spine mechanical compression.

RESULTS

The results clearly demonstrated the link between the level of ischemia and the viability state of the spinal tissue. When SCBF decreased, in both experimental models, mitochondrial NADH was elevated, while reperfusion was associated with NADH oxidation. Nevertheless, during the recovery phase, even though SCBF significantly increased (became hyperemic), no further oxidation of NADH was observed.

CONCLUSION

The monitoring of the mitochondrial function together with SCBF by the TVMS reflects the viability of the spinal cord tissue and, together with the conventional monitoring techniques, may help to evaluate the spine conditions, especially under surgical procedures involving the deterioration of the spinal cord blood supply.

Movements elicited by electrical stimulation of muscles, nerves, intermediate spinal cord, and spinal roots in anesthetized and decerebrate cats

Electrical stimulation offers the possibility of restoring motor function of paralyzed limbs after spinal-cord injury or stroke, but few data are available to compare possible sites of stimulation, such as muscle, nerve, spinal roots, or spinal cord. The aim of this study was to establish some characteristics of stimulation at these sites in the anesthetized and midcollicular decerebrate cat. The hind limb was constrained to move in the sagittal plane against a spring load. Ventral-root stimulation only produced movements down and back; the direction moved systematically backward the more caudal the stimulated roots. In contrast, dorsal-root stimulation only produced movements up and forward. Thus, neither method alone could produce the full range of normal movements. Muscle, nerve, and intraspinal stimulation within the intermediate regions of the gray matter generated discrete, selective movements in a wide range of directions. Muscle stimulation required an order of magnitude more current. Single microwire electrodes located in the spinal gray matter could activate a synergistic group of muscles, and generally had graded recruitment curves, but the direction of movement occasionally changed abruptly as stimulus strength increased. Nerve stimulation produced the largest movements against the spring load (>80% of the passive range of motion) and was the most reproducible from animal to animal. However, recruitment curves with nerve stimulation were quite steep, so fine control of movement might be difficult. The muscle, nerve, and spinal cord all seem to be feasible sites to restore motor function. The pros and cons from this study may be helpful in deciding the best site for a particular application, but further tests are needed in the chronically transected spinal cord to assess the applicability of these results to human patients.

Peripheral nerve grafts and aFGF restore partial hindlimb function in adult paraplegic rats

The purpose of this study was to evaluate the degree of functional recovery in adult rats with completely transected spinal cord following experimental treatment regimens that include implantation of peripheral nerve segments and local application of acidic fibroblast growth factor (aFGF). Rats were randomly divided to five groups: (1) spinal cord transection, (2) spinal cord transection and aFGF treatment, (3) spinal cord transection and peripheral nerve grafts, (4) spinal cord transection, aFGF treatment, and peripheral nerve grafts, and (5) sham control (laminectomy only). The locomotor behavior of all rats was analyzed by the Basso, Beattie and Bresnahan (BBB) open field locomotor test over the six months survival time. Immunohistochemisty for neurofilament protein, and somatosensory (SSEP) and motor evoked potentials (MEP) were used to evaluate axon growth across the damage site following the different treatments. The results show four principal findings: (1) Only the combination of peripheral nerve grafts and aFGF treatment improved hindlimb locomotor function after spinal cord transection. (2) The SSEP and MEP demonstrated electrophysiological evidence of both sensory and motor information crossing the damaged site, but only in the combined nerve grafts and aFGF treatment rats. (3) Immunostaining demonstrated neurofilament positive axons extending through the graft area and into distal end of spinal cord, but only in the group with combined nerve grafts and aFGF treatment. (4) Retransection of group 4 rats eliminated the behavioral recovery, MEP, and SSEP responses, indicating that the improvement of hindlimb locomotor activity came from supraspinal control. These results demonstrate the ability of the repair strategy combining peripheral nerve grafts and aFGF treatment to facilitate the regeneration of spinal ascending and descending tracts and also recovery of motor behavior following spinal cord injury.

Managing neural tissue injury in combined vertebral column-spinal cord injury

Orthopaedic, neurosurgical, and trauma nurses all care for patients who have sustained a spinal cord injury (SCI) and are challenged to address care issues related to spinal stability as well as neurologic function. Advances in the understanding of the pathobiology of SCI have given rise to a three-tiered, time-sensitive approach to intervention designed to optimize functional recovery. Immediately after injury, pharmacologic strategies dominate. They are generally intended to limit progression of the initial injury, preserve existing neurologic function, and create the nidus for future regeneration. This article reviews the current standard of care with respect to hyperacute neuroprotection after blunt SCI in adults. After a synopsis of selected concepts in the pathophysiology of injury and pharmacology, clinical trial results will be presented, followed by a discussion of the nursing implications associated with the use of high-dose methylprednisolone neuroprotective therapy.