Mild traumatic brain injuries (TBIs), particularly when repetitive in nature, are increasingly recognized to have a range of significant negative implications for brain health. Much of the ongoing research in the field is focused on the neurological consequences of these injuries and the relationship between TBIs and long-term neurodegenerative conditions such as chronic traumatic encephalopathy and Alzheimer's disease. However, our understanding of the complex relationship between applied mechanical force at impact, brain pathophysiology, and neurological function remains incomplete. Past research has shown that mild TBIs, even below the threshold that results in cranial fracture, induce changes in cranial bone structure and morphology. These structural and physiological changes likely have implications for the transmission of mechanical force into the underlying brain parenchyma. Here, we review this evidence in the context of the current understanding of bone mechanosensitivity and the consequences of TBIs or concussions. We postulate that heterogeneity of the calvarium, including differing bone thickness attributable to past impacts, age, or individual variability, may be a modulator of outcomes after subsequent TBIs. We advocate for greater consideration of cranial responses to TBI in both experimental and computer modeling of impact biomechanics, and raise the hypothesis that calvarial bone thickness represents a novel biomarker of brain injury vulnerability post-TBI.

Cranial Bone Changes Induced by Mild Traumatic Brain Injuries: A Neglected Player in Concussion Outcomes?

Meningeal lymphatics restoration and neurovascular protection synergistically improve traumatic brain injury treatment

Glioma is one of the most aggressive solid brain tumors with a poor prognosis. A chronic tumor inflammatory microenvironment drives glioma promotion and progression. The neutrophil-to-lymphocyte ratio and other clinicopathological variables usually serve as prognostic glioma markers. However, they are not ubiquitous prognostic markers for glioma as they fail to reveal the intricacy between the glioma-specific tumor inflammatory microenvironment and the systemic inflammatory responses, especially those chronic inflammatory responses, which vary among individuals fabricating diverse prognostic outcomes. Here, we introduced an explainable artificial intelligence model to typify chronic inflammatory responses as prognostic markers for glioma using 694-patients’ data from The Cancer Genome Atlas. We characterized the glioma-specific personalized inflammatory mediators using multi-layered regulators such as transcriptional networks, cellular infiltration markers, and cellular senescence markers, which identified five unique chronic inflammatory responses (p-value<0.0001). We defined its prognostic significance using overall survival analyses. The chronic inflammatory responses were positively correlated with poor overall survival in glioma. The patients with higher chronic inflammatory responses showed significantly shorter overall survival than those with lower chronic inflammatory responses. Interestingly, optimizing those chronic inflammatory responses improved the overall survival of glioma patients. We identified the effector genes within the personalized inflammatory mediators’ networks, indicating them as the targets for optimizing individualized chronic inflammatory response profiles through co-drug intervention. Significance Explainable artificial intelligence-based typification of chronic inflammatory responses accelerates glioma prognosis and supports co-drug discovery to modulate inflammatory responses alongside cancer therapy, suggested by 694-glioma patients’ data analysis.

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An explainable artificial intelligence-based typification of chronic inflammatory responses enhances glioma prognosis

The persistent dysregulation and accumulation of poisonous proteins from destructive neural tissues and cells activate pathological mechanisms after traumatic brain injury (TBI). The lymphatic drainage system of the brain, composed of the glymphatic system and meningeal lymphatic vessels (MLVs), plays an essential role in the clearance of toxic waste after brain injury. The neuroprotective effect of interleukin 33 (IL-33) in TBI mice has been demonstrated; however, its impact on brain lymphatic drainage is unclear. Here, we established a fluid percussion injury model to examine the IL-33 administration effects on neurological function and lymphatic drainage in the acute brain of TBI mice. We verified that exogenous IL-33 could improve the motor and memory skills of TBI mice and demonstrated that in the acute phase, it increased the exchange of cerebrospinal and interstitial fluid, reversed the dysregulation and depolarization of aquaporin-4 in the cortex and hippocampus, improved the drainage of MLVs to deep cervical lymph nodes, and reduced tau accumulation and glial activation. We speculate that the protective effect of exogenous IL-33 on TBI mice's motor and cognitive functions is related to the enhancement of brain lymphatic drainage and toxic metabolite clearance from the cortex and hippocampus in the acute stage. These data further support the notion that IL-33 therapy may be an effective treatment strategy for alleviating acute brain injury after TBI. 

https://actaneurocomms.biomedcentral.com/counter/pdf/10.1186/s40478-023-01555-4

Exogenous interleukin 33 enhances the brain’s lymphatic drainage and toxic protein clearance in acute traumatic brain injury mice

Immune regulation in neurovascular units after traumatic brain injury

Brain edema is the most common and fatal complication after traumatic brain injury (TBI). Meningeal lymphatic vessels (MLVs) are the conduits that transport cerebrospinal fluid (CSF) and macromolecules to deep extracranial cervical lymph nodes (dCLNs). After TBI, the drainage function of MLVs can become impaired. However, the scenario in which the improvement of the function of MLVs can promote brain edema absorption after TBI has not been reported. Therefore, the purpose of this study was to investigate the effects of ketoprofen, 9-cis retinoic acid (RA) and vascular endothelial cell growth factor-C (VEGF-C), which promote the proliferation of peripheral lymphatic vessels, on the cerebellar medullary cistern injection of TBI rats, as well as their mechanism of action on brain edema after TBI. In the experiment, we found that ketoprofen, 9-cisRA, and VEGF-C can improve the function of MLVs, promote the extracranial drainage of CSF and the absorption of brain edema, weaken the neuroinflammatory response, reduce reactive oxygen species (ROS) production, maintain the structural integrity of MLVs, and improve neurological function. In addition, ketoprofen, 9-cisRA, and VEGF-C upregulated the lymphatic-specific proteins VEGF receptor (VEGFR)3, PROX1, forkhead box protein C2 (FOXC2), and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1). These results indicate that ketoprofen, 9-cisRA, and VEGF-C may maintain the integrity of the meningeal lymphatic wall and promote lymphatic proliferation by upregulating the expression of lymphatic vessel-specific proteins, improve meningeal lymphatic function after TBI, promote CSF drainage and brain edema absorption, reduce the immune response of the nervous system, and reduce ROS formation, thereby improving prognoses. These findings may provide new ideas for the treatment of brain edema after TBI. 

Karl Martin

Papers

Improving the Function of Meningeal Lymphatic Vessels to Promote Brain Edema Absorption after Traumatic Brain Injury