Sequential therapy of anti-Nogo-A antibody treatment and treadmill training leads to cumulative improvements after spinal cord injury in rats.

Intense training is the most clinically successful treatment modality following incomplete spinal cord injuries (SCIs). With the advent of plasticity enhancing treatments, understanding how treatments might interact when delivered in combination becomes critical. Here, we investigated a rational approach to sequentially combine treadmill locomotor training with antibody mediated suppression of the fiber growth inhibitory protein Nogo-A. Following a large but incomplete thoracic lesion, rats were immediately treated with either anti-Nogo-A or control antibody (2weeks) and then either left untrained or step-trained starting 3weeks after injury for 8weeks. It was found that sequentially combined therapy improved step consistency and reduced toe dragging and climbing errors, as seen with training and anti-Nogo-A individually. Animals with sequential therapy also adopted a more parallel paw position during bipedal walking and showed greater overall quadrupedal locomotor recovery than individual treatments. Histologically, sequential therapy induced the greatest corticospinal tract sprouting caudally into the lumbar region and increased the number of serotonergic synapses onto lumbar motoneurons. Increased primary afferent sprouting and synapse formation onto lumbar motoneurons observed with anti-Nogo-A antibody were reduced by training. Animals with sequential therapy also showed the highest reduction of lumbar interneuronal activity associated with walking (c-fos expression). No treatment effects for thermal nociception, mechanical allodynia, or lesion volume were observed. The results demonstrate that sequential administration of anti-Nogo-A antibody followed in time with intensive locomotor training leads to superior recovery of lost locomotor functions, which is probably mediated by changes in the interaction between descending sprouting and local segmental networks after SCI.

Movement rehabilitation after spinal cord injuries: emerging concepts and future directions.

Considerable inroads are being made into developing new treatments for spinal cord injury (SCI) which aim to facilitate functional recovery, including locomotion. Research on rehabilitative strategies following SCI using animal models has demonstrated that regaining and maintaining motor function, such as standing or stepping, is governed by principles of skill acquisition. Mechanisms key to learning motor tasks, including retention and transfer of skill, feedback and conditions of practice, all have examples in the SCI animal literature, although the importance of many concepts may often be overlooked. Combinatorial strategies which include physical rehabilitation are beginning to yield promising results. However, the effects of molecular-cellular interventions including chondroitinaseABC, anti-NogoA, foetal stem cell transplantation, etc., are still poorly understood with reference to the changes made to spinal plasticity by training and exercise. Studies that investigate the interplay between rehabilitation and other treatments have had mixed results; it appears likely that precise timings of different interventions will help to maximize recovery of function. Understanding how the time-course of injury and different rehabilitative and treatment modalities might factor into spinal plasticity will be critical in future therapeutic interventions.

Osteopontin expression and function within the dorsal root ganglion.

Osteopontin expression has previously been demonstrated in the adult rat dorsal root ganglion, although its function remains unclear. Here, we demonstrate, using real-time reverse transcription-polymerase (RT-PCR) chain reaction, that osteopontin mRNA expression is increased 1 and 3 weeks following sciatic nerve section (axotomy). Further, immunohistochemical staining suggests that this increase is restricted to neurons already expressing the protein. Osteopontin knock-out animals have significantly increased mechanosensory thresholds in the intact adult compared with the wild-type controls; however no differences in allodynia are noted between genotypes using a model of neuropathic pain. Lastly, exogenous recombinant osteopontin has no effect on neurite outgrowth from adult wild-type sensory neurons, nor were differences in neurite outgrowth observed in osteopontin knock-out animals compared with wild-type controls.