Background Inflammasome-mediated neuroinflammation may cause secondary injury following traumatic brain injury (TBI) in children. The pattern recognition receptors NLRP1 and NLRP3 are essential components of their respective inflammasome complexes. We sought to investigate whether NLRP1 and/or NLRP3 abundance is altered in children with severe TBI. Methods Cerebrospinal fluid (CSF) from children (n=34) with severe TBI (Glasgow coma scale score [GCS] ≤8) who had externalized ventricular drains placed for routine care was evaluated for NLRP1 and NLRP3 at 0–24h, 25–48h, 49–72h, and >72h post-TBI and was compared to infection-free controls that underwent lumbar puncture to rule out CNS infection (n=8). Patient age, sex, initial GCS, mechanism of injury, treatment with therapeutic hypothermia, and 6 month Glasgow outcome score (GOS) were collected. Results CSF NLRP1 was undetectable in controls and detected in 2 TBI patients and at only <24h post-TBI. CSF NLRP3 levels were increased in TBI patients compared with controls at all time points, p<0.001. TBI patients ≤ 4 years of age had higher peak NLRP3 levels vs. patients > 4 (15.50 [3.65–25.71] vs. 3.04 [1.52–8.87] ng/mL, respectively; p=0.048). Controlling for initial GCS in multivariate analysis, peak NLRP3 > 6.63ng/mL was independently associated with poor outcome at 6 months. Conclusions In the first report of NLRP1 and NLRP3 in childhood neurotrauma we found that CSF NLRP3 is elevated in children with severe TBI and independently associated with younger age and poor outcome. Future studies correlating NLRP3 with other markers of inflammation and response to therapy are warranted.

Objective Cerebral Edema (CE) in TBI is the consequence of multiple underlying mechanisms, and is associated with unfavorable outcomes. Genetic variability in these pathways likely explains some of the clinical heterogeneity observed in edema development. A role for Sulfonylurea-receptor-1 (Sur1) in CE is supported. However, there are no prior studies examining the effect of genetic variability in the Sur1 gene (ABCC8) on the development of CE. We hypothesize that ABCC8 single nucleotide polymorphisms (SNP) are predictive of CE. Methods DNA was extracted from 385 patients. SNPs in ABCC8 were genotyped using the Human Core Exome v1.2 (Illumina). CE measurements included acute CT edema, mean and peak intracranial pressure (ICP), and need for decompressive craniotomy. Results 14 SNPs with minor-allele frequency>0.2 were identified. 4 SNPS rs2283261, rs3819521, rs2283258 and rs1799857 were associated with CE measures. In multiple regression models, homozygote-variant genotypes in rs2283261, rs3819521, and rs2283258 had increased odds of CT edema (OR=2.45, p=0.007; OR=2.95, p=0.025; OR=3.00, p=0.013), had higher mean (β=3.13,p=0.000; β=2.95,p=0.005; β=3.20,p=0.008) and peak (β=8.00,p=0.001; β=7.64,p=0.007; β=6.89,p=0.034) ICP. The homozygote wild-type genotype of rs1799857 had decreased odds of decompressive craniotomy (OR=0.47, p=0.004). Conclusions This is the first report assessing the impact of ABCC8 genetic variability on CE development in TBI. Minor allele ABCC8 SNP genotypes had increased risk of CE, while major SNP alleles were protective—potentially suggesting an evolutionary advantage. These findings could guide risk stratification, treatment responders, and the development of novel targeted or gene-based therapies against CE in TBI and other neurological disorders.

This study identifies four tag SNPs associated with cerebral oedema and/or outcome in TBI, tagging a region including 33 polymorphisms. In polymorphisms predictive of oedema, variant alleles/genotypes confer increased risk. Different variant polymorphisms were associated with favourable outcome, potentially suggesting distinct mechanisms. Significant polymorphisms spatially clustered flanking exons encoding the sulfonylurea receptor site and transmembrane domain 0/loop 0 (juxtaposing the channel pore/binding site). This, if validated, may help build a foundation for developing future strategies that may guide individualised care, treatment response, prognosis and patient selection for clinical trials.

Cerebral edema is critical to morbidity/mortality in traumatic brain injury (TBI) and is worsened by hypotension. Glibenclamide may reduce cerebral edema by inhibiting sulfonylurea receptor-1 (Sur1); its effect on diffuse cerebral edema exacerbated by hypotension/resuscitation is unknown. We aimed to determine if glibenclamide improves pericontusional and/or diffuse edema in controlled cortical impact (CCI) (5m/sec, 1 mm depth) plus hemorrhagic shock (HS) (35 min), and compare its effects in CCI alone. C57BL/6 mice were divided into five groups (n = 10/group): naïve, CCI+vehicle, CCI+glibenclamide, CCI+HS+vehicle, and CCI+HS+glibenclamide. Intravenous glibenclamide (10 min post-injury) was followed by a subcutaneous infusion for 24 h. Brain edema in injured and contralateral hemispheres was subsequently quantified (wet-dry weight). This protocol brain water (BW) = 80.4% vehicle vs. 78.3% naïve, p < 0.01) but was not reduced by glibenclamide (I%BW = 80.4%). Ipsilateral edema also developed in CCI alone (I%BW = 80.2% vehicle vs. 78.3% naïve, p < 0.01); again unaffected by glibenclamide (I%BW = 80.5%). Contralateral (C) %BW in CCI+HS was increased in vehicle (78.6%) versus naive (78.3%, p = 0.02) but unchanged in CCI (78.3%). At 24 h, glibenclamide treatment in CCI+HS eliminated contralateral cerebral edema (C%BW = 78.3%) with no difference versus naïve. By 72 h, contralateral cerebral edema had resolved (C%BW = 78.5 ± 0.09% vehicle vs. 78.3 ± 0.05% naïve). Glibenclamide decreased 24 h contralateral cerebral edema in CCI+HS. This beneficial effect merits additional exploration in the important setting of TBI with polytrauma, shock, and resuscitation. Contralateral edema did not develop in CCI alone. Surprisingly, 24 h of glibenclamide treatment failed to decrease ipsilateral edema in either model. Interspecies dosing differences versus prior studies may play an important role in these findings. Mechanisms underlying brain edema may differ regionally, with pericontusional/osmolar swelling refractory to glibenclamide but diffuse edema (via Sur1) from combined injury and/or resuscitation responsive to this therapy. TBI phenotype may mandate precision medicine approaches to treat brain edema.

PURPOSE Despite the enormity of the problem and the lack of new therapies, research in the pre-clinical arena specifically using pediatric traumatic brain injury (TBI) models is limited. In this review, some of the key models addressing both the age spectrum of pediatric TBI and its unique injury mechanisms will be highlighted. Four topics will be addressed, namely, 1) unique facets of the developing brain important to TBI model development, 2) a description of some of the most commonly used pre-clinical models of severe pediatric TBI including work in both rodents and large animals, 3) a description of the pediatric models of mild TBI and repetitive mild TBI that are relatively new, and finally 4) a discussion of challenges, gaps and potential future directions to further advance work in pediatric TBI models. METHODS This narrative review on the topic of pediatric TBI models was based on review of PUBMED/Medline along with a synthesis of information on key factors in pre-clinical and clinical developmental brain injury that influence TBI modeling. RESULTS In the contemporary literature, six types of models have been used in rats including weight drop, fluid percussion injury (FPI), impact acceleration, controlled cortical impact (CCI), mechanical shaking, and closed head modifications of CCI. In mice, studies are largely restricted to CCI. In large animals, FPI and rotational injury have been used in piglets and shake injury has also been used in lambs. Most of the studies have been in severe injury models, although more recently studies have begun to explore mild and repetitive mild injuries to study concussion. CONCLUSIONS Given the emerging importance of TBI in infants and children, the morbidity and mortality that is produced, along with its purported link to the development of chronic neurodegenerative diseases, studies in these models merit greater systematic investigations along with consortium type approaches and long-term follow-up to translate new therapies to the bedside.