Profiling medical specialties and informing aspiring physicians: a data-driven approach.

A detailed, unbiased perspective of the inter-relations among medical fields could help students make informed decisions on their future career plans. Using a data-driven approach, the inter-relations among different medical fields were decomposed and clustered based on the similarity of their working environments.Publicly available, aggregate databases were merged into a single rich dataset containing demographic, working environment and remuneration information for physicians across Canada. These data were collected from the Canadian Institute for Health Information, the Canadian Medical Association, and the Institute for Clinical Evaluative Sciences, primarily from 2018 to 2019. The merged dataset includes 25 unique medical specialties, each with 36 indicator variables. Latent Profile Analysis (LPA) was used to group specialties into distinct clusters based on relatedness.The 25 medical specialties were decomposed into seven clusters (latent variables) that were chosen based on the Bayesian Information Criterion. The Kruskal-Wallis test identified eight indicator variables that significantly differed between the seven profiles. These variables included income, work settings and payment styles. Variables that did not significantly vary between profiles included demographics, professional satisfaction, and work-life balance satisfaction.The 25 analyzed medical specialties were grouped in an unsupervised manner into seven profiles via LPA. These profiles correspond to expected and meaningful groups of specialties that share a common theme and set of indicator variables (e.g. procedurally-focused, clinic-based practice). These profiles can help aspiring physicians narrow down and guide specialty choice.

Inflammatory Biomarkers and Intracranial Hemorrhage after Endovascular Thrombectomy.

BACKGROUND: Intracranial hemorrhage after endovascular thrombectomy is associated with poorer prognosis compared with those who do not develop the complication. Our study aims to determine predictors of post-EVT hemorrhage - more specifically, inflammatory biomarkers present in baseline serology. METHODS: We performed a retrospective review of consecutive patients treated with EVT for acute large vessel ischemic stroke. The primary outcome of the study is the presence of ICH on the post-EVT scan. We used four definitions: the SITS-MOST criteria, the NINDS criteria, asymptomatic hemorrhage, and overall hemorrhage. We identified nonredundant predictors of outcome using backward elimination based on Akaike Information Criteria. We then assessed prediction accuracy using area under the receiver operating curve. Then we implemented variable importance ranking from logistic regression models using the drop in Naegelkerke R2 with the exclusion of each predictor. RESULTS: Our study demonstrates a 6.3% SITS (16/252) and 10.0% NINDS (25/252) sICH rate, as well as a 19.4% asymptomatic (49/252) and 29.4% (74/252) overall hemorrhage rate. Serologic markers that demonstrated association with post-EVT hemorrhage were: low lymphocyte count (SITS), high neutrophil count (NINDS, overall hemorrhage), low platelet to lymphocyte ratio (NINDS), and low total WBC (NINDS, asymptomatic hemorrhage). CONCLUSION: Higher neutrophil counts, low WBC counts, low lymphocyte counts, and low platelet to lymphoycyte ratio were baseline serology biomarkers that were associated with post-EVT hemorrhage. Our findings, particularly the association of diabetes mellitus and high neutrophil, support experimental data on the role of thromboinflammation in hemorrhagic transformation of large vessel occlusions.

Data Driven Analysis Reveals Shared Transcriptome Response, Immune Cell Composition, and Distinct Mortality Rates Across Differing Etiologies of Critical Illness.

OBJECTIVES: Sepsis and trauma are common health problems and provide great challenges in critical care. Diverse patient responses to these conditions further complicate patient management and outcome prediction. Whole blood transcriptomics provides a unique opportunity to follow the molecular response in the critically ill. Prior results show robust and diverse genomic signal in the acute phase and others have found shared biological mechanisms across divergent disease etiologies. We hypothesize that selected transcriptomics responses, particularly immune mechanisms are shared across disease etiologies. We further hypothesize that these processes may identify homogenous patient subgroups with shared clinical course in critical illness deciphering disease heterogeneity. These processes may serve as universal markers for predicting a complicated clinical course and/or risk of a poor outcome. DESIGN: We present a system level, data driven, genome-wide analysis of whole blood gene expression for a total of 382 patients suffering from either abdominal sepsis (49), pulmonary sepsis (107) or trauma (158) and compare these to gene expression in healthy controls (68). PATIENTS AND SETTING: We relied on available open genetic data from gene expression omnibus for patients diagnosed with abdominal sepsis, community-acquired pneumonia, or trauma which also included healthy control patients. MEASUREMENTS AND MAIN RESULTS: Our results confirm that immune processes are shared across disease etiologies in critical illnesses. We identify two consistent and distinct patient subgroups through deconvolution of serum transcriptomics: 1) increased neutrophils and naïve CD4 cell fractions and 2) suppressed neutrophil fraction. Furthermore, we found immune and inflammatory processes were downregulated in subgroup 2, a configuration previously shown to be more susceptible to multiple organ failure. Correspondingly, this subgroup had significantly higher mortality rates in all three etiologies of illness (0% vs 6.1%, p = 3.1 × 10 for trauma; 15.0% vs 25.4%, p = 4.4 × 10 for community-acquired pneumonia, and 7.1% vs 20.0%, p = 3.4 × 10 for abdominal sepsis). CONCLUSIONS: We identify two consistent subgroups of critical illness based on serum transcriptomics and derived immune cell fractions, with significantly different survival rates. This may serve as a universal predictor of complicated clinical course or treatment response and, importantly, may identify opportunities for subgroup-specific immunomodulatory intervention.

Multimorbidity states associated with higher mortality rates in organ dysfunction and sepsis: a data-driven analysis in critical care.

BACKGROUND: Sepsis remains a complex medical problem and a major challenge in healthcare. Diagnostics and outcome predictions are focused on physiological parameters with less consideration given to patients' medical background. Given the aging population, not only are diseases becoming increasingly prevalent but occur more frequently in combinations ("multimorbidity"). We hypothesized the existence of patient subgroups in critical care with distinct multimorbidity states. We further hypothesize that certain multimorbidity states associate with higher rates of organ failure, sepsis, and mortality co-occurring with these clinical problems. METHODS: We analyzed 36,390 patients from the open source Medical Information Mart for Intensive Care III (MIMIC III) dataset. Morbidities were defined based on Elixhauser categories, a well-established scheme distinguishing 30 classes of chronic diseases. We used latent class analysis to identify distinct patient subgroups based on demographics, admission type, and morbidity compositions and compared the prevalence of organ dysfunction, sepsis, and inpatient mortality for each subgroup. RESULTS: We identified six clinically distinct multimorbidity subgroups labeled based on their dominant Elixhauser disease classes. The "cardiopulmonary" and "cardiac" subgroups consisted of older patients with a high prevalence of cardiopulmonary conditions and constituted 6.1% and 26.4% of study cohort respectively. The "young" subgroup included 23.5% of the cohort composed of young and healthy patients. The "hepatic/addiction" subgroup, constituting 9.8% of the cohort, consisted of middle-aged patients (mean age of 52.25, 95% CI 51.85-52.65) with the high rates of depression (20.1%), alcohol abuse (47.75%), drug abuse (18.2%), and liver failure (67%). The "complicated diabetics" and "uncomplicated diabetics" subgroups constituted 9.4% and 24.8% of the study cohort respectively. The complicated diabetics subgroup demonstrated higher rates of end-organ complications (88.3% prevalence of renal failure). Rates of organ dysfunction and sepsis ranged 19.6-69% and 12.5-46.7% respectively in the six subgroups. Mortality co-occurring with organ dysfunction and sepsis ranges was 8.4-23.8% and 11.7-27.4% respectively. These adverse outcomes were most prevalent in the hepatic/addiction subgroup. CONCLUSION: We identify distinct multimorbidity states that associate with relatively higher prevalence of organ dysfunction, sepsis, and co-occurring mortality. The findings promote the incorporation of multimorbidity in healthcare models and the shift away from the current single-disease paradigm in clinical practice, training, and trial design.

Operative planning aid for optimal endoscopic third ventriculostomy entry points in pediatric cases.

OBJECT: Endoscopic third ventriculostomy (ETV) uses anatomical spaces of the ventricular system to reach the third ventricle floor and create an alternative pathway for cerebrospinal fluid flow. Optimal ETV trajectories have been previously proposed in the literature, designed to grant access to the third ventricle floor without a displacement of eloquent periventricular structures. However, in hydrocephalus, there is a significant variability to the configuration of the ventricular system, implying that the optimal ETV trajectory and cranial entry point needs to be planned on a case-by-case basis. In the current study, we created a mathematical model, which tailors the optimal ETV entry point to the individual case by incorporating the ventricle dimensions. METHODS: We retrospectively reviewed the imaging of 30 consecutive pediatric patients with varying degrees of ventriculomegaly. Three dimensional radioanatomical models were created using preoperative MRI scans to simulate the optimal ETV trajectory and entry point for each case. The surface location of cranial entry points for individual ETV trajectories was recorded as Cartesian coordinates centered at Bregma. The distance from the Bregma in the coronal plane represented as "x", and the distance from the coronal suture in the sagittal plane represented as "y". The correlation between the ventricle dimensions and the x, y coordinates were tested using linear regression models. RESULTS: The distance of the optimal ETV entry point from the Bregma in the coronal plane ("x") and from the coronal suture in the sagittal plane ("y") correlated well with the frontal horn ratio (FHR). The coordinates for x and y were fitted along the following linear equations: x = 85.8 FHR-13.3 (r 2 = 0.84, p < 0.001) and y = -69.6 FHR + 16.7 (r 2 = 0.83, p < 0.001). CONCLUSION: The surface location of the optimal cranial ETV entry point correlates well with the ventricle size. We provide the first model that can be used as a surgical planning aid for a case specific ETV entry site with the incorporation of the ventricle size.

Aquaporin-4 regulates the velocity and frequency of cortical spreading depression in mice.

The astrocyte water channel aquaporin-4 (AQP4) regulates extracellular space (ECS) K(+) concentration ([K(+)]e) and volume dynamics following neuronal activation. Here, we investigated how AQP4-mediated changes in [K(+)]e and ECS volume affect the velocity, frequency, and amplitude of cortical spreading depression (CSD) depolarizations produced by surface KCl application in wild-type (AQP4(+/+)) and AQP4-deficient (AQP4(-/-)) mice. In contrast to initial expectations, both the velocity and the frequency of CSD were significantly reduced in AQP4(-/-) mice when compared with AQP4(+/+) mice, by 22% and 32%, respectively. Measurement of [K(+)]e with K(+)-selective microelectrodes demonstrated an increase to ∼35 mM during spreading depolarizations in both AQP4(+/+) and AQP4(-/-) mice, but the rates of [K(+)]e increase (3.5 vs. 1.5 mM/s) and reuptake (t1/2 33 vs. 61 s) were significantly reduced in AQP4(-/-) mice. ECS volume fraction measured by tetramethylammonium iontophoresis was greatly reduced during depolarizations from 0.18 to 0.053 in AQP4(+/+) mice, and 0.23 to 0.063 in AQP4(-/-) mice. Analysis of the experimental data using a mathematical model of CSD propagation suggested that the reduced velocity of CSD depolarizations in AQP4(-/-) mice was primarily a consequence of the slowed increase in [K(+)]e during neuronal depolarization. These results demonstrate that AQP4 effects on [K(+)]e and ECS volume dynamics accelerate CSD propagation.

Quantifying surgical access in eyebrow craniotomy with and without orbital bar removal: cadaver and surgical phantom studies.

BACKGROUND: Eyebrow craniotomy is a recently described minimally invasive approach for tackling primarily pathology of the anterior skull base. The removal of the orbital bar may further expand the surgical corridor of this exposure, but the extent of benefit is poorly quantified. We assessed the effect of orbital bar removal with regards to surgical access in the eyebrow craniotomy using classic morphometric measurements in cadaver heads. Using surgical phantoms and neuronavigation, we also measured the 'working volume', a new parameter for characterising the volume of surgical access in these approaches. METHODS: Silicon injected cadaver heads (n = 5) were used for morphometric analysis of the eyebrow craniotomy with and without orbital bar removal. Working depths and 'working areas' of surgical access were measured as defined by key anatomical landmarks. The eyebrow craniotomy with or without orbital bar removal was also simulated using surgical phantoms (n = 3, 90-120 points per trial), calibrated against a frameless neuronavigation system. Working volume was derived from reference coordinates recorded along the anatomical borders of the eyebrow craniotomy using the "α-shape algorithm" in R statistics. RESULTS: In cadaver heads, eyebrow craniotomy with removal of the orbital bar reduced the working depth to the ipsilateral anterior clinoid process (42 ± 2 versus 33 ± 3 mm; p < 0.05), but the working areas as defined by deep neurovascular and bony landmarks was statistically unchanged (total working areas of 418 ± 80 cm(2) versus 334 ± 48 cm(2); p = 0.4). In surgical phantom studies, however, working-volume for the simulated eyebrow craniotomies was increased with orbital bar removal (16 ± 1 cm(3) versus 21 ± 1 cm(3); p < 0.01). CONCLUSIONS: In laboratory studies, orbital bar removal in eyebrow craniotomy provides a modest reduction in working depth and increase in the working volume. But this must be weighed up against the added morbidity of the procedure. Working volume, a newly developed parameter may provide a more meaningful endpoint for characterising the surgical access for different surgical approaches and it could be applied to other operative cases undertaken with frameless neuronavigation.

Identification of clinically relevant patient endotypes in traumatic brain injury using latent class analysis.

Traumatic brain injury (TBI) is a complex condition where heterogeneity impedes the advancement of care. Understanding the diverse presentations of TBI is crucial for personalized medicine. Our study aimed to identify clinically relevant patient endotypes in TBI using latent class analysis based on comorbidity data. We used the Medical Information Mart for Intensive Care III database, which includes 2,629 adult TBI patients. We identified five stable endotypes characterized by specific comorbidity profiles: Heart Failure and Arrhythmia, Healthy, Renal Failure with Hypertension, Alcohol Abuse, and Hypertension. Each endotype had distinct clinical characteristics and outcomes: The Heart Failure and Arrhythmia endotype had lower survival rates than the Renal Failure with Hypertension despite featuring fewer comorbidities overall. Patients in the Hypertension endotype had higher rates of neurosurgical intervention but shorter stays in contrast to the Alcohol Abuse endotype which had lower rates of neurosurgical intervention but significantly longer hospital stays. Both endotypes had high overall survival rates comparable to the Healthy endotype. Logistic regression models showed that endotypes improved the predictability of survival compared to individual comorbidities alone. This study validates clinical endotypes as an approach to addressing heterogeneity in TBI and demonstrates the potential of this methodology in other complex conditions.

Identification of genes with oscillatory expression in glioblastoma: the paradigm of SOX2.

Quiescence, a reversible state of cell-cycle arrest, is an important state during both normal development and cancer progression. For example, in glioblastoma (GBM) quiescent glioblastoma stem cells (GSCs) play an important role in re-establishing the tumour, leading to relapse. While most studies have focused on identifying differentially expressed genes between proliferative and quiescent cells as potential drivers of this transition, recent studies have shown the importance of protein oscillations in controlling the exit from quiescence of neural stem cells. Here, we have undertaken a genome-wide bioinformatic inference approach to identify genes whose expression oscillates and which may be good candidates for controlling the transition to and from the quiescent cell state in GBM. Our analysis identified, among others, a list of important transcription regulators as potential oscillators, including the stemness gene SOX2, which we verified to oscillate in quiescent GSCs. These findings expand on the way we think about gene regulation and introduce new candidate genes as key regulators of quiescence.

Eyebrow craniotomy for anterior skull base lesions: how I do it.

BACKGROUND: The eyebrow craniotomy is a less invasive alternative approach for accessing anterior skull base lesions, compared to traditional and more extensive exposures. We give a stepwise description of this minimally invasive technique with discussion on the indications, limitations and key aspects of perioperative management. METHODS: Positioning of the head and planning the surgical corridor are dictated by the nature, site and size of the target lesion. The eyebrow incision should spare the medial and posterolateral neural structures. Microsurgical strategy is based on opening up the basal cisterns and respecting the distorted neurovascular anatomy. Selective use of brain retractor and angulation of the operative microscope enable the surgeon to make use of the "keyhole effect" for accessing a larger target. Perioperative measures are in part dictated by the nature of the pathology, involvement of the optic apparatus and changes to pituitary function. CONCLUSION: The eyebrow craniotomy may be safely used as a minimally invasive approach for a variety of anterior skull base lesions. There is an operative learning curve and some types of pathologies are easier to approach by this technique than others. KEY POINTS: • The eyebrow craniotomy is an alternative less invasive approach for accessing anterior skull base lesions • Positioning of the head and planning the surgical corridor are dictated by the nature, site and size of the target lesion • Microsurgical strategy is based on opening up the basal cisterns and respecting the distorted neurovascular anatomy. • Selective use of brain retractor and angulation of the operative microscope enable the surgeon to make use of the "keyhole effect" for accessing a larger target • Perioperative measures are in part dictated by the nature of the pathology, involvement of the optic apparatus and changes to pituitary function. • There is an operative learning curve and some types of pathologies are easier to approach by this technique than others.

Endoscopic transnasal approach to the pituitary--operative technique and nuances.

BACKGROUND: The endoscopic transnasal approach is becoming the preferred minimally invasive approach to the pituitary region. We review the key anatomical landmarks, stepwise description of the surgical technique, technical variations, indications, limitations and important aspects of peri-operative management. TECHNIQUE: The procedure consists of nasal, sphenoidal and sella stages performed using a rigid fibre-optic endoscope. Tumour debulking is undertaken with low-profile ring curettes, suction and/or ultrasonic aspirator. At the end, the pituitary fossa floor is reconstructed in a graded fashion, depending on the extent of the CSF leak through the arachnoidal and dural defects. Important technical variations include the surgeon position relative to the patient, uni- versus binostril approach, two- versus four-handed technique, extent of resection of the middle turbinate and the type of repair of the sella floor. Post-operative management is influenced by the nature of the pathology, involvement of the optic apparatus and changes to the pituitary function. In selected cases, extension of the technique along the sagittal and coronal planes can allow access to the other pathologies in the anterior, middle and posterior skull bases (i.e. the so-called extended approach). CONCLUSION: The endoscopic approach is becoming the technique of choice for accessing the pituitary region, with reduced nasal trauma, improved access, visualisation and potentially better tumour resection compared to the microscopic technique. However, there is an operative learning curve and some pathologies are more easily approached by this technique than others.

Earlier Surgery Reduces Complications in Acute Traumatic Thoracolumbar Spinal Cord Injury: Analysis of a Multi-Center Cohort of 4108 Patients.

Early surgical intervention to decompress the spinal cord and stabilize the spinal column in patients with acute traumatic thoracolumbar spinal cord injury (TLSCI) may lessen the risk of developing complications and improve outcomes. However, there has yet to be agreement on what constitutes "early" surgery; reported thresholds range from 8 to 72 h. To address this knowledge gap, we conducted an observational cohort study using data from the American College of Surgeons (ACS) Trauma Quality Improvement Program (TQIP) from 2010 to 2016. The association between time from hospital arrival to surgical intervention and risk of major complications was assessed using restricted cubic splines. Propensity score matching was then used to assess the association between delayed surgery and risk of complications. Across 354 trauma centers 4108 adult TLSCI patients who underwent surgery were included. Median time-to-surgery was 18.8 h (interquartile range [IQR]: 7.4-40.9 h). The spline model suggests the risk of major complication rises consistently after a 12-h surgical wait-time. After propensity score matching, the odds of major complication were significantly lower for those receiving surgery within 12 h (odds ratio [OR] 0.77, 95% confidence interval [CI]: 0.64 to 0.94). This was also true for immobility-related complications (OR 0.79, 95% CI: 0.64 to 0.97). Patients in the early group spent 1.5 fewer days in the critical care unit on average (95% CI: -2.09 to -0.88). Although surgery within 12 h may not always be feasible, these data suggest that whenever possible surgeons should strive to reduce the amount of time between hospital arrival and surgical intervention, and health care systems should support this endeavor.

Cancer-selective metabolic vulnerabilities in MYC-amplified medulloblastoma.

MYC-driven medulloblastoma (MB) is an aggressive pediatric brain tumor characterized by therapy resistance and disease recurrence. Here, we integrated data from unbiased genetic screening and metabolomic profiling to identify multiple cancer-selective metabolic vulnerabilities in MYC-driven MB tumor cells, which are amenable to therapeutic targeting. Among these targets, dihydroorotate dehydrogenase (DHODH), an enzyme that catalyzes de novo pyrimidine biosynthesis, emerged as a favorable candidate for therapeutic targeting. Mechanistically, DHODH inhibition acts on target, leading to uridine metabolite scarcity and hyperlipidemia, accompanied by reduced protein O-GlcNAcylation and c-Myc degradation. Pyrimidine starvation evokes a metabolic stress response that leads to cell-cycle arrest and apoptosis. We further show that an orally available small-molecule DHODH inhibitor demonstrates potent mono-therapeutic efficacy against patient-derived MB xenografts in vivo. The reprogramming of pyrimidine metabolism in MYC-driven medulloblastoma represents an unappreciated therapeutic strategy and a potential new class of treatments with stronger cancer selectivity and fewer neurotoxic sequelae.

Redefining critical illness.

Research and practice in critical care medicine have long been defined by syndromes, which, despite being clinically recognizable entities, are, in fact, loose amalgams of heterogeneous states that may respond differently to therapy. Mounting translational evidence-supported by research on respiratory failure due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-suggests that the current syndrome-based framework of critical illness should be reconsidered. Here we discuss recent findings from basic science and clinical research in critical care and explore how these might inform a new conceptual model of critical illness. De-emphasizing syndromes, we focus on the underlying biological changes that underpin critical illness states and that may be amenable to treatment. We hypothesize that such an approach will accelerate critical care research, leading to a richer understanding of the pathobiology of critical illness and of the key determinants of patient outcomes. This, in turn, will support the design of more effective clinical trials and inform a more precise and more effective practice at the bedside.

Integrated computational analyses reveal novel insights into the stromal microenvironment of SHH-subtype medulloblastoma.

Medulloblastoma is the most common malignant brain tumour of childhood. While our understanding of this disease has progressed substantially in recent years, the role of tumour microenvironment remains unclear. Given the increasing role of microenvironment-targeted therapeutics in other cancers, this study was aimed at further exploring its role in medulloblastoma. Multiple computational techniques were used to analyze open-source bulk and single cell RNA seq data from primary samples derived from all subgroups of medulloblastoma. Gene expression is used to infer stromal subpopulations, and network-based approaches are used to identify potential therapeutic targets. Bulk data was obtained from 763 medulloblastoma samples and single cell data from an additional 7241 cells from 23 tumours. Independent bulk (285 tumours) and single cell (32,868 cells from 29 tumours) validation cohorts were used to verify results. The SHH subgroup was found to be enriched in stromal activity, including the epithelial-to-mesenchymal transition, while group 3 is comparatively stroma-suppressed. Several receptor and ligand candidates underlying this difference are identified which we find to correlate with metastatic potential of SHH medulloblastoma. Additionally, a biologically active gradient is detected within SHH medulloblastoma, from "stroma-active" to "stroma-suppressed" cells which may have relevance to targeted therapy. This study serves to further elucidate the role of the stromal microenvironment in SHH-subgroup medulloblastoma and identify novel treatment possibilities for this challenging disease.

Aquaporin-4 Reduces Post-Traumatic Seizure Susceptibility by Promoting Astrocytic Glial Scar Formation in Mice.

Seizures are important neurological complications after traumatic brain injury (TBI) and are reported for up to 50% of patients with TBI. Despite several studies, no drug strategy has been able to alter the biological events leading to epileptogenesis. The glial water channel, aquaporin-4 (AQP4), was shown to facilitate cytotoxic cell swelling in ischemia and glial scar formation after stab wound injury. In this study, we examined post-traumatic seizure susceptibility of AQP4-deficient mice (AQP4-/-) after injection of pentylenetetrazole (PTZ) 1 month after controlled cortical impact (CCI) and compared them to wild-type sham injury controls. After PTZ injection, AQP4-/- mice demonstrated dramatically shortened seizure latency (120 ± 40 vs. 300 ± 70 sec; p < 0.001) and increased seizure severity (grade 7.5 ± 0.4 vs. 5.8 ± 0.4; p < 0.001) compared to their wild-type counterparts. Morphometric analysis demonstrated a significant 2-fold reduction in astrocytosis, with a concomitant increase in microgliosis in injured AQP4-null mice compared to their injured wild-type counterparts (44 ± 2 vs. 24 ± 3 cells per high power field [cells/hpf], respectively; p < 0.0001). Minocycline, an inhibitor of microglia, reversed the post-TBI epilepsy phenotype of AQP4-null mice. After minocycline treatment, AQP4-/- mice demonstrated similar latency of seizures evoked by PTZ (723 ± 35 vs. 696 ± 38 sec; p > 0.05) and severity of seizures evoked by PTZ (grade 4.0 ± 0.5 vs. 3.81 ± 0.30; p > 0.05) compared to wild-type counterparts. Immunohistochemical analysis demonstrated decreased immunostaining of microglia to levels comparable to wild-type (12 ± 2 vs. 11 ± 4 cells/hpf, respectively; p > 0.05). Taken together, these results suggest a protective role of AQP4 in post-traumatic seizure susceptibility by promoting astrogliosis, formation of a glial scar, and preventing microgliosis.

Novel variants in human Aquaporin-4 reduce cellular water permeability.

Cerebral edema contributes significantly to morbidity and mortality after brain injury and stroke. Aquaporin-4 (AQP4), a water channel expressed in astrocytes, plays a key role in brain water homeostasis. Genetic variants in other aquaporin family members have been associated with disease phenotypes. However, in human AQP4, only one non-synonymous single-nucleotide polymorphism (nsSNP) has been reported, with no characterization of protein function or disease phenotype. We analyzed DNA from an ethnically diverse cohort of 188 individuals to identify novel AQP4 variants. AQP4 variants were constructed by site-directed mutagenesis and expressed in cells. Water permeability assays in the cells were used to measure protein function. We identified 24 variants in AQP4 including four novel nsSNPs (I128T, D184E, I205L and M224T). We did not observe the previously documented M278T in our sample. The nsSNPs found were rare ( approximately 1-2% allele frequency) and heterozygous. Computational analysis predicted reduced function mutations. Protein expression and membrane localization were similar for reference AQP4 and the five AQP4 mutants. Cellular assays confirmed that four variant AQP4 channels reduced normalized water permeability to between 26 and 48% of the reference (P < 0.001), while the M278T mutation increased normalized water permeability (P < 0.001). We identified multiple novel AQP4 SNPs and showed that four nsSNPs reduced water permeability. The previously reported M278T mutation resulted in gain of function. Our experiments provide insight into the function of the AQP4 protein. These nsSNPs may have clinical implications for patients with cerebral edema and related disorders.

Gene Expression Signatures Identify Biologically Homogenous Subgroups of Grade 2 Meningiomas.

INTRODUCTION: Meningiomas are the most common brain tumor, with prevalence of approximately 3%. Histological grading has a major role in determining treatment choice and predicting outcome. While indolent grade 1 and aggressive grade 3 meningiomas exhibit relatively homogeneous clinical behavior, grade 2 meningiomas are far more heterogeneous, making outcome prediction challenging. We hypothesized two subgroups of grade 2 meningiomas which biologically resemble either World Health Organization (WHO) grade 1 or WHO grade 3. Our aim was to establish gene expression signatures that separate grade 2 meningiomas into two homogeneous subgroups: a more indolent subtype genetically resembling grade 1 and a more aggressive subtype resembling grade 3. METHODS: We carried out an observational meta-analysis on 212 meningiomas from six distinct studies retrieved from the open-access platform Gene Expression Omnibus. Microarray data was analyzed with systems-level gene co-expression network analysis. Fuzzy C-means clustering was employed to reclassify 34 of the 46 grade 2 meningiomas (74%) into a benign "grade 1-like" (13/46), and malignant "grade 3-like" (21/46) subgroup based on transcriptomic profiles. We verified shared biology between matching subgroups based on meta-gene expression and recurrence rates. These results were validated further using an independent RNA-seq dataset with 160 meningiomas, with similar results. RESULTS: Recurrence rates of "grade 1-like" and "grade 3- like" tumors were 0 and 75%, respectively, statistically similar to recurrence rates of grade 1 (17%) and 3 (85%). We also found overlapping biological processes of new subgroups with their adjacent grades 1 and 3. CONCLUSION: These results underpin molecular signatures as complements to histological grading systems. They may help reshape prediction, follow-up planning, treatment decisions and recruitment protocols for future and ongoing clinical trials.

Landscape of immune cell gene expression is unique in predominantly WHO grade 1 skull base meningiomas when compared to convexity.

Modulation of tumor microenvironment is an emerging frontier for new therapeutics. However in meningiomas, the most frequent adult brain tumor, the correlation of microenvironment with tumor phenotype is scarcely studied. We applied a variety of systems biology approaches to bulk tumor transcriptomics to explore the immune environments of both skull base and convexity (hemispheric) meningiomas. We hypothesized that the more benign biology of skull base meningiomas parallels the relative composition and activity of immune cells that oppose tumor growth and/or survival. We firstly applied gene co-expression networks to tumor bulk transcriptomics from 107 meningiomas (derived from 3 independent studies) and found immune processes to be the sole biological mechanism correlated with anatomical location while correcting for tumour grade. We then derived tumor immune cell fractions from bulk transcriptomics data and examined the immune cell-cytokine interactions using a network-based approach. We demonstrate that oncolytic Gamma-Delta T cells dominate skull base meningiomas while mast cells and neutrophils, known to play a role in oncogenesis, show greater activity in convexity tumors. Our results are the first to suggest the importance of tumor microenvironment in meningioma biology in the context of anatomic location and immune landscape. These findings may help better inform surgical decision making and yield location-specific therapies through modulation of immune microenvironment.

Distinct regional ontogeny and activation of tumor associated macrophages in human glioblastoma.

Tumor-associated macrophages (TAMs) constitute up to 50% of tumor bulk in glioblastoma (GBM) and play an important role in tumor maintenance and progression. The recently discovered differences between invading tumour periphery and hypoxic tumor core implies that macrophage biology is also distinct by location. This may provide further insight into the observed treatment resistance to immune modulation. We hypothesize that macrophage activation occurs through processes that are distinct in tumor periphery versus core. We therefore investigated regional differences in TAM recruitment and evolution in GBM by combining open source single cell and bulk gene expression data. We used single cell gene expression data from 4 glioblastomas (total of 3589 cells) and 122 total bulk samples obtained from 10 different patients. Cell identity, ontogeny (bone-marrow derived macrophages-BMDM vs microglia), and macrophage activation state were inferred using verified gene expression signatures. We captured the spectrum of immune states using cell trajectory analysis with pseudotime ordering. In keeping with previous studies, TAMs carrying BMDM identity were more abundant in tumor bulk while microglia-derived TAMs dominated the tumor periphery across all macrophage activation states including pre-activation. We note that core TAMs evolve towards a pro-inflammatory state and identify a subpopulation of cells based on a gene program exhibiting strong, opposing correlation with Programmed cell Death-1 (PD-1) signaling, which may correlate to their response to PD-1 inhibition. By contrast, peripheral TAMs evolve towards anti-inflammatory phenotype and contains a population of cells strongly associated with NFkB signaling. Our preliminary analysis suggests important regional differences in TAMs with regard to recruitment and evolution. We identify regionally distinct and potentially actionable cell subpopulations and advocate the need for a multi-targeted approach to GBM therapeutics.