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Objectives: A vendor informed us that rats shipped to us and used by us in a spinal cord contusion injury experiment were infected by rat parvovirus type 1a (RPV-1a). Our aim was therefore to determine whether this infection may have altered locomotor recovery or tissue pathology. Setting: Stockholm, Sweden. Methods: We induced a moderate contusion injury of the spinal cord in rats received from an (unknown to us) RPV-1a-contaminated facility. We compared the hind limb locomotor function between RPV-1a-infected rats and non-infected controls with the same spinal cord lesions, obtained before (historical control), as well as after infection (future controls). Histologically, we assessed spinal tissue sparing, astrocyte reactivity and the amount of macrophages/activated microglia. Results: RPV-1a-infected rats had significantly better hind limb locomotor recovery compared with both ‘historical' and ‘future' controls. We also observed significantly better tissue sparing and axonal sparing around the injury site, as well as significant reductions in macrophages/activated microglia and astrocyte reactivity in the spinal cords of RPV-1a-infected rats. Conclusion: The results stress the importance of knowing the health status of animals used to study central nervous system trauma and support the notion that acquired infections, even if asymptomatic, may alter response to injury in mammals. Furthermore, the results demonstrate that virus infections may have positive effects on functional recovery after spinal cord injury and indicate that RPV-1a infection may be neuroprotective by dampening secondary damage.

With no currently available drug treatment for spinal cord injury, there is a need for additional therapeutic candidates. We took the approach of repositioning existing pharmacological agents to serve as acute treatments for spinal cord injury and previously found imatinib to have positive effects on locomotor and bladder function in experimental spinal cord injury when administered immediately after the injury. However, for imatinib to have translational value, it needs to have sustained beneficial effects with delayed initiation of treatment, as well. Here, we show that imatinib improves hind limb locomotion and bladder recovery when initiation of treatment was delayed until 4 h after injury and that bladder function was improved with a delay of up to 24 h. The treatment did not induce hypersensitivity. Instead, imatinib-treated animals were generally less hypersensitive to either thermal or mechanical stimuli, compared with controls. In an effort to provide potential biomarkers, we found serum levels of three cytokines/chemokines—monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-3α, and keratinocyte chemoattractant/growth-regulated oncogene (interleukin 8)—to increase over time with imatinib treatment and to be significantly higher in injured imatinib-treated animals than in controls during the early treatment period. This correlated to macrophage activation and autofluorescence in lymphoid organs. At the site of injury in the spinal cord, macrophage activation was instead reduced by imatinib treatment. Our data strengthen the case for clinical trials of imatinib by showing that initiation of treatment can be delayed and by identifying serum cytokines that may serve as candidate markers of effective imatinib doses.

Article history: Received 31 March 2014 Revised 24 April 2014 Accepted 25 April 2014 Available online 11 May 2014 studies (Benowitz, 2012; Bunge and Pearse, 2012; Erschbamer et al., 2012), pointing out weaknesses in the re-assessment studies including incomplete replication of the basis of the original experiments, too much variability, too little power and other suboptimal circumstances. In the following, we wish to comment on the reassessment (Sharp et al., 2014a) of our imatinib study (Abrams et al., 2012). We assisted the re-assessment team by responding to questions about details

Mechanistic target of rapamycin complex 1 (mTORC1) is an intracellular kinase complex that regulates energy homeostasis and transcription. Modulation of mTORC1 has proven beneficial in experimental spinal cord injury, making this molecular target a candidate for therapeutic intervention in spinal cord injury. However, both inactivation and activation of mTORC1 have been reported beneficial for recovery. To obtain a more complete picture of mTORC1 activity, we aimed to characterize the spatiotemporal activation pattern of mTORC1 and identify activation in particular cell types after contusion spinal cord injury in rats. To be able to provide a spatial characterization of mTORC1 activation, we monitored activation of downstream target S6. We found robust mTORC1 activation both at the site of injury and in spinal segments rostral and caudal to the injury. There was constitutive mTORC1 activation in neurons that was biphasically reduced caudally after injury. We found biphasic mTORC1 activation in glial cells, primarily activated microglia/macrophages. Furthermore, we found mTORC1 activation in proliferating cells, suggesting this may be a function affected by mTORC1 modulation. Our results reveal potential windows of opportunity for therapeutic interference with mTORC1 signaling and immune cells as targets for inhibition of mTORC1 in spinal cord injury.

A number of different rodent experimental models of spinal cord injury have been used in an attempt to model the pathophysiology of human spinal cord injury. As a result, interlaboratory comparisons of the outcome measures can be difficult. Further complicating interexperiment comparisons is the fact that the rodent response to different experimental models is strain-dependent. Moreover, the literature is abundant with examples in which the same injury model and strain result in divergent functional outcomes. The objective of this research was to determine whether substrain differences influence functional outcome in experimental spinal cord injury. We induced mild contusion spinal cord injuries in three substrains of Sprague-Dawley rats purchased from three different European breeders (Scanbur, Charles River, and Harlan) and evaluated the impact of injury on spontaneous locomotor function, hypersensitivity to mechanical stimulation, and bladder function. We found that Harlan rats regained significantly more hindlimb function than Charles River and Scanbur rats. We also observed substrain differences in the recovery of the ability to empty the bladder and development of hypersensitivity to mechanical stimulation. The Harlan substrain did not show any signs of hypersensitivity in contrast to the Scanbur and Charles River substrains, which both showed transient reduction in paw withdrawal thresholds. Lastly, we found histological differences possibly explaining the observed behavioral differences. We conclude that in spite of being the same strain, there might be genetic differences that can influence outcome measures in experimental studies of spinal cord injury of Sprague-Dawley rats from different vendors.

After contusion spinal cord injury (SCI), astrocytes become reactive and form a glial scar. While this reduces spreading of the damage by containing the area of injury, it inhibits regeneration. One strategy to improve the recovery after SCI is therefore to reduce the inhibitory effect of the scar, once the acute phase of the injury has passed. The pleiotropic cytokine interleukin-6 (IL-6) is secreted immediately after injury and regulates scar formation; however, little is known about the role of IL-6 in the sub-acute phases of SCI. Interestingly, IL-6 also promotes axon regeneration, and therefore its induction in reactive astrocytes may improve regeneration after SCI. We found that IL-6 is expressed by astrocytes and neurons one week post-injury and then declines. Using primary cultures of rat astrocytes we delineated the molecular mechanisms that regulate IL-6 expression and secretion. IL-6 expression requires activation of p38 and depends on NF-κB transcriptional activity. Activation of these pathways in astrocytes occurs when the PI3K-mTOR-AKT pathway is inhibited. Furthermore, we found that an increase in cytosolic calcium concentration was necessary for IL-6 secretion. To induce IL-6 secretion in astrocytes, we used torin2 and rapamycin to block the PI3K-mTOR pathway and increase cytosolic calcium, respectively. Treating injured animals with torin2 and rapamycin for two weeks, starting two weeks after injury when the scar has been formed, lead to a modest effect on mechanical hypersensitivity, limited to the period of treatment. These data, taken together, suggest that treatment with torin2 and rapamycin induces IL-6 secretion by astrocytes and may contribute to the reduction of mechanical hypersensitivity after SCI.