AC105 Increases Extracellular Magnesium Delivery and Reduces Excitotoxic Glutamate Exposure within Injured Spinal Cords in Rats

Central nervous system development in rabbits (Oryctolagus cuniculus L. 1758)

The present study describes the embryonic and fetal development of the central nervous system in rabbits from the seventh day after conception until the end of the full-term fetal period. A total of 19 embryonic and fetal samples were carefully dissected and microscopically analyzed. Neural tube closure was observed between 7.5 and 8 days of gestation. Primordial encephalic vesicle differentiation and spinal canal delimitation were observed on the 12th day of gestation. Histologically, on the 15th day of gestation, the brain, cerebellum, and brain stem were delimited. On the 18th day of gestation, the cervical and lumbar intumescences of the spinal cord were visible. On the 28th day of gestation, four-cell layers could be distinguished in the cerebral cortex, while the cerebellar cortex was still differentiating. Overall, the morphological aspects of the embryonic and fetal developmental phases in rabbits were highly similar to those in humans. Thus, the present study provides relevant information highlighting rabbits as an excellent candidate animal model for preclinical research on human neurological diseases given the high adaptability of rabbits to bioterium conditions and the similarity of morphological events between rabbits and humans.

Persistent oppression and simple decompression both exacerbate spinal cord ascorbate levels

Background: Surgical decompression after acute spinal cord injury has become the consensus of orthopaedic surgeons. However, the choice of surgical decompression time window after acute spinal cord injury has been one of the most controversial topics in orthopaedics. Objective: We apply an online electrochemical system (OECS) for continuously monitoring the ascorbate of the rats' spinal cord to determine the extent to which ascorbate levels were influenced by contusion or sustained compression. Methods: Adult Sprague-Dawley rats (n=10) were instrumented for ascorbate concentration recording and received T11 drop spinal cord injury (SCI). The Group A (n=5) were treated with immediately decompression after SCI. The Group B (n=5) were contused and oppressed until 1 h after the injury to decompress. Results: The ascorbate level of spinal cord increased immediately by contusion injury and reached to 1.62 μmol/L ± 0.61 μmol/L (217.30% ± 95.09% of the basal level) at the time point of 60 min after the injury. Compared with the Group A, the ascorbate level in Group B increased more significantly at 1 h after the injury, reaching to 3.76 μmol/L ± 1.75 μmol/L (430.25% ± 101.30% of the basal level). Meanwhile, we also found that the decompression after 1 hour of continuous compression will cause delayed peaks of ascorbate reaching to 5.71 μmol/L ± 2.69 μmol/L (627.73% ± 188.11% of the basal level). Conclusion: Our study provides first-hand direct experimental evidence indicating ascorbate is directly involved in secondary spinal cord injury and exhibits the dynamic time course of microenvironment changes after continuous compression injury of the spinal cord.

Riluzole promotes neurological function recovery and inhibits damage extension in rats following spinal cord injury: a meta-analysis and systematic review

Spinal cord injury (SCI) is a devastating condition that has few treatment options. Riluzole, a sodium channel blocker used to treat amyotrophic lateral sclerosis, has been initially trialed in human SCI. We performed a systematic review to critically assess the efficacy of riluzole in locomotor recovery and damage extension in SCI rat models, and the potential for clinical translation. PubMed, Embase, Cochrane Library, and Chinese databases were searched from their inception date to March 2018. Two reviewers independently selected animal studies that evaluated neurological recovery and lesion area following riluzole treatment in SCI rat models, extracted data and assessed methodological quality. Pairwise meta-analysis, subgroup analysis, and network meta-analysis were performed to assess the effects of riluzole on SCI. Ten eligible studies were included. Two studies had high methodological quality. Overall, the Basso, Beattie, and Bresnahan scores were increased in riluzole-treated animals versus controls, and effect sizes showed a gradual increase from the 1st (five studies, n = 104, mean difference = 1.24, 95% CI = 0.11 to 2.37, p = 0.03) to 6th week after treatment (five studies, n = 120, mean difference = 2.34, 95% CI = 1.26 to 3.42, p < 0.0001). Riluzole was associated with improved outcomes in the inclined plane test and the tissue preservation area. Subgroup analyses suggested an association of locomotor recovery with riluzole dose. Network meta-analysis showed that 5 mg/kg riluzole exhibited greater protection than 2.5 and 8 mg/kg riluzole. Collectively, this review suggests that riluzole has a protective effect on SCI, with good safety and a clear mechanism of action and may be suitable for future clinical trials or applications. However, animal results should be interpreted with caution given the known limitations in animal experimental design and methodological quality.

Polyethylene glycol in spinal cord injury repair: a critical review

Polyethylene glycol (PEG) is a synthetic biocompatible polymer with many useful properties for developing therapeutics to treat spinal cord injury. Direct application of PEG as a fusogen to the injury site can repair cell membranes, mitigate oxidative stress, and promote axonal regeneration to restore motor function. PEG can be covalently or noncovalently conjugated to proteins, peptides, and nanoparticles to limit their clearance by the reticuloendothelial system, reduce their immunogenicity, and facilitate crossing the blood-brain barrier. Cross-linking PEG produces hydrogels that can act as delivery vehicles for bioactive molecules including growth factors and cells such as bone marrow stromal cells, which can modulate the inflammatory response and support neural tissue regeneration. PEG hydrogels can be cross-linked in vitro or delivered as an injectable formulation that can gel in situ at the site of injury. Chemical and mechanical properties of PEG hydrogels are tunable and must be optimized for creating the most favorable delivery environment. Peptides mimicking extracellular matrix protein such as laminin and n-cadherin can be incorporated into PEG hydrogels to promote neural differentiation and axonal extensions. Different hydrogel cross-linking densities and stiffness will also affect the differentiation process. PEG hydrogels with a gradient of peptide concentrations or Young's modulus have been developed to systematically study these factors. This review will describe these and other recent advancements of PEG in the field of spinal cord injury in greater detail.