Hypothermia Used in Medical Applications for Brain and Spinal Cord Injury Patients

Effect of Valproic Acid on NLR Family Pyrin Domain Containing 1/3 (NLRP1/3) Inflammasome in Rats with Acute Spinal Cord Injury

Our study assesses valproic acid’s effect on NLRP1/3 inflammasome in rats with acute spinal cord injury (SCI). SD rats were clamped by aneurysm clips to establish SCI model followed by analysis of functional recovery by BBB score, degree of inflammatory infiltration, by H&E staining, NLRP1/NLRP3 and P2X7 level by western blot, IL-1β and IL-18 level by ELISA, blood spinal cord barrier by EVANS blue method. After SCI, the lower limb motor function of rats decreased and recovered after valproic acid treatment (P < 0.05). Inflammatory cell infiltration of SCI group increased and decreased after treatment. After SCI, NLRP1/3 level increased and P2X7 protein level elevated which were reversed after valproic acid treatment (P < 0.05). In rats with SCI, IL-1β level in spinal cord was higher than sham operation and lower after treatment (P < 0.05) without difference of IL-18 between injury group and treatment group (P > 0.05). In addition, fluorescence was higher in injury group than sham operation group and lower in valproic acid injection group than injury group. In conclusion, Valproic acid can promote motor function recovery in rats after SCI and inhibit inflammasome 1 and 3 expression, thereby inhibiting the maturation and release of IL-1β, and reducing P2X7 level after SCI.

Effects of therapeutic hypothermia on the safety of children with severe traumatic brain injury: a systematic review and meta-analysis

BACKGROUND

Therapeutic hypothermia (TH) is effective to treat adult traumatic brain injury (TBI), but there is still controversy about its safety to treat the children with severe TBI.

METHODS

Clinical studies on TH in children with severe TBI from January 2000 to September 2020 were screened in PubMed, Web of Science, Embase, Cochrane Library, Nature, NCKI, and Wanfang online databases. Data were meta-analyzed by Rev Man 5.3. Differences in mortality, adverse outcomes, duration of Pediatric Intensive Care Unit (PICU), incidence of infection, and incidence of arrhythmia were compared between experimental group and control group. The heterogeneity of the results was evaluated by chi-square test and I² test in Rev Man 5.3, and publication bias was evaluated by funnel plot.

RESULTS

Five articles were included, including 421 children. Cochrane evaluation was B grade or above, and Jadad scale score was over three points. The overall mortality between two groups showed great difference [odds ratio (OR) =1.72, 95% CI: 0.98-3.02, Z=1.87, P=0.04]. The incidence of adverse outcomes (OR =1.39, 95% CI: 0.86-2.25, Z=1.34, P=0.18), the duration of PICU [mean difference (MD) =0.51, 95% CI: -0.33 to 1.35, Z=1.19, P=0.24], the incidence of infection (OR =0.79, 95% CI: 0.51-1.23, Z=1.03, P=0.30), and the incidence of arrhythmia (OR =3.10, 95% CI: 0.77-12.50, Z=1.59, P=0.11) were not considerably different.

DISCUSSION

TH significantly reduced overall mortality in children with severe TBI, but did not significantly improve the incidence of adverse outcomes, PICU duration, infection rate, or arrhythmia. These results provided a reference for selecting proper clinical treatment methods for children with severe TBI.

Multifaceted Roles of cAMP Signaling in the Repair Process of Spinal Cord Injury and Related Combination Treatments

Spinal cord injury (SCI) results in multiple pathophysiological processes, including blood–spinal cord barrier disruption, hemorrhage/ischemia, oxidative stress, neuroinflammation, scar formation, and demyelination. These responses eventually lead to severe tissue destruction and an inhibitory environment for neural regeneration.cAMP signaling is vital for neurite outgrowth and axonal guidance. Stimulating intracellular cAMP activity significantly promotes neuronal survival and axonal regrowth after SCI.However, neuronal cAMP levels in adult CNS are relatively low and will further decrease after injury. Targeting cAMP signaling has become a promising strategy for neural regeneration over the past two decades. Furthermore, studies have revealed that cAMP signaling is involved in the regulation of glial cell function in the microenvironment of SCI, including macrophages/microglia, reactive astrocytes, and oligodendrocytes. cAMP-elevating agents in the post-injury milieu increase the cAMP levels in both neurons and glial cells and facilitate injury repair through the interplay between neurons and glial cells and ultimately contribute to better morphological and functional outcomes. In recent years, combination treatments associated with cAMP signaling have been shown to exert synergistic effects on the recovery of SCI. Agents carried by nanoparticles exhibit increased water solubility and capacity to cross the blood–spinal cord barrier. Implanted bioscaffolds and injected hydrogels are potential carriers to release agents locally to avoid systemic side effects. Cell transplantation may provide permissive matrices to synergize with the cAMP-enhanced growth capacity of neurons. cAMP can also induce the oriented differentiation of transplanted neural stem/progenitor cells into neurons and increase the survival rate of cell grafts. Emerging progress focused on cAMP compartmentation provides researchers with new perspectives to understand the complexity of downstream signaling, which may facilitate the clinical translation of strategies targeting cAMP signaling for SCI repair.

Autophagy of Spinal Microglia Affects the Activation of Microglia through the PI3K/AKT/mTOR Signaling Pathway

Delayed paralysis occurs within some patients suffered from ischemic spinal cord injury (ISCI) due to the aorta occlusion during the repair surgery of thoracic and thoracoabdominal aortic aneurysms. Although mild hypothermia has been reported to improve ISCI and prolong the tolerance of rats to ISCI without inducing immediate paralysis, the mechanism remains unclear. Herein, the study revealed that the mild hypothermia treatment indeed partially improved the ISCI in rats caused by cross-clamping at the descending aorta. ISCI induced the excessive activation of microglia and moderate autophagy in the spinal cord tissues of rats, while mild hypothermia significantly induced autophagy and reversed the excessive activation of microglia in the spinal cord tissues of rats. In OGD-stimulated mouse microglia BV-2 cells, the excessive activation of microglia and moderate autophagy were also observed; in the rapamycin-treated OGD model in BV-2 cells, autophagy was significantly enhanced whereas the excessive activation of microglia was reversed. In both in vivo ISCI model in rats and in vitro OGD model in BV-2 cells, the PI3K/AKT/mTOR pathway showed to be inhibited, whereas the PI3K/AKT/mTOR pathway was further inhibited by mild hypothermia in ISCI rats or rapamycin treatment in OGD-stimulated BV-2 cells. In conclusion, enhanced autophagy might be the mechanism of inhibited microglia activation by hypothermia treatment in ISCI rats and by rapamycin treatment in OGD-stimulated BV-2 cells. Autophagy could be enhanced through inhibiting the PI3K/AKT/mTOR pathway.

Pharmacologic and Regenerative Cell Therapy for Spinal Cord Injury: WFNS Spine Committee Recommendations

This is a review article examining the pharmacologic and regenerative cell therapy for spinal cord injury. A literature search during last 10 years were conducted using key words. Case reports, experimental (nonhuman) studies, papers other than English language were excluded. Up-to-date information on the pharmacologic and regenerative cell therapy for spinal cord injury was reviewed and statements were produced to reach a consensus in 2 separate consensus meeting of WFNS Spine Committee. The statements were voted and reached a consensus using Delphi method. Pharmacologic and regenerative cell therapy for spinal cord injury have long been an interest of many experimental and clinical researches. Clinical studies with methylpredinisolone have not shown clear cut benefit. Other drugs such as Rho inhibitor, minocycline, riluzole, granulocyte colony-stimulating factor have also been tried without significant benefits. Regenerative cell therapy using different types of stem cells, different inoculation techniques, and scaffolds have undergone many trials highlighting the efficacies of cells and their limitations. This review article summarizes the current knowledge on pharmacologic and regenerative cell therapy for spinal cord injury. Unfortunately, there is a need for further experimental and human trials to recommend effective pharmacologic and regenerative cell therapy.

Effects of local hypothermia-rewarming on physiology, metabolism and inflammation of acutely injured human spinal cord

In five patients with acute, severe thoracic traumatic spinal cord injuries (TSCIs), American spinal injuries association Impairment Scale (AIS) grades A-C, we induced cord hypothermia (33 °C) then rewarming (37 °C). A pressure probe and a microdialysis catheter were placed intradurally at the injury site to monitor intraspinal pressure (ISP), spinal cord perfusion pressure (SCPP), tissue metabolism and inflammation. Cord hypothermia-rewarming, applied to awake patients, did not cause discomfort or neurological deterioration. Cooling did not affect cord physiology (ISP, SCPP), but markedly altered cord metabolism (increased glucose, lactate, lactate/pyruvate ratio (LPR), glutamate; decreased glycerol) and markedly reduced cord inflammation (reduced IL1β, IL8, MCP, MIP1α, MIP1β). Compared with pre-cooling baseline, rewarming was associated with significantly worse cord physiology (increased ICP, decreased SCPP), cord metabolism (increased lactate, LPR; decreased glucose, glycerol) and cord inflammation (increased IL1β, IL8, IL4, IL10, MCP, MIP1α). The study was terminated because three patients developed delayed wound infections. At 18-months, two patients improved and three stayed the same. We conclude that, after TSCI, hypothermia is potentially beneficial by reducing cord inflammation, though after rewarming these benefits are lost due to increases in cord swelling, ischemia and inflammation. We thus urge caution when using hypothermia-rewarming therapeutically in TSCI.