RNF213 rare variants in an ethnically diverse population with Moyamoya disease.

BACKGROUND AND PURPOSE: Moyamoya disease (MMD) is a rare, genetically heterogeneous cerebrovascular disease resulting from occlusion of the distal internal carotid arteries. A variant in the Ring Finger 213 gene (RNF213), altering arginine at position 4810 (p.R4810K), is associated with MMD in Asian populations. However, there are a lack of data on the role of RNF213 in patients with MMD of additional ethnicities and diasporic Asian populations. We investigate the contribution of RNF213 alterations to MMD in an ethnically diverse population based in the United States. METHODS: We initially sequenced RNF213 exons 43, 44, and 45 (encoding the eponymous RING finger domain) and exon 60 (encoding p.R4810K) in 86 ethnically diverse patients with MMD. Comprehensive exome sequencing data from 24 additional patients with MMD was then analyzed to identify RNF213 variants globally. Segregation of variants with MMD and other vascular diseases was assessed in families. RESULTS: RNF213 p.R4810K was identified in 56% (9/16) of patients with MMD of Asian descent and not in 94 patients of non-Asian descent. 3.6% (4/110) of patients had variants in the exons encoding the RING finger domain. Seven additional variants were identified in 29% (7/24) of patients with MMD who underwent exome sequencing. Segregation analysis supported an association with MMD for 2 variants and a lack of association with disease for 1 variant. CONCLUSIONS: These results confirm that alterations in RNF213 predispose patients of diverse ethnicities to MMD, and that the p.R4810K variant predisposes individuals of Asian descent in the United States to MMD.

CD44 deficiency contributes to enhanced experimental autoimmune encephalomyelitis: a role in immune cells and vascular cells of the blood-brain barrier.

Adhesion molecule CD44 is expressed by multiple cell types and is implicated in various cellular and immunological processes. In this study, we examined the effect of global CD44 deficiency on myelin oligodendrocyte glycoprotein peptide (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Compared to C57BL/6 wild-type mice, CD44-deficient mice presented with greater disease severity, increased immune cell numbers in the central nervous system, and increased anti-MOG antibody and proinflammatory cytokine production, especially those associated with T helper 17 (Th17) cells. Further, decreased numbers of peripheral CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) were observed in CD44-knockout mice throughout the disease course. CD44-knockout CD4 T cells exhibited reduced transforming growth factor-ß receptor type I (TGF-ß RI) expression that did not impart a defect in Treg polarization in vitro, but did correlate with enhanced Th17 polarization in vitro. Further, EAE in bone marrow-chimeric animals suggested CD44 expression on both circulating and noncirculating cells limited disease severity. Endothelial expression of CD44 limited T-cell adhesion to and transmigration through murine endothelial monolayers in vitro. Importantly, we also identified increased permeability of the blood-brain barrier in vivo in CD44-deficient mice before and following immunization. These data suggest that CD44 has multiple protective roles in EAE, with effects on cytokine production, T-cell differentiation, T-cell-endothelial cell interactions, and blood-brain barrier integrity.

CD44 regulates vascular endothelial barrier integrity via a PECAM-1 dependent mechanism.

Vascular integrity is a critical parameter in normal growth and development. Loss of appropriate vascular barrier function is present in various immune- and injury-mediated pathological conditions. CD44 is an adhesion molecule expressed by multiple cell types, including endothelial cells (EC). The goal of the present study was to examine how loss of CD44 affected vascular permeability. Using C57BL/6 WT and CD44-KO mice, we found no significant permeability to Evan's Blue in either strain at baseline. However, there was significantly increased histamine-induced permeability in CD44-deficient mice compared to WT counterparts. Similar results were observed in vitro, where CD44-deficient endothelial monolayers were also impermeable to 40kD-FITC dextran in the absence of vasoactive challenge, but exhibited enhanced and prolonged permeability following histamine. However, CD44-KO monolayers have reduced baseline barrier strength by electrical resistance, which correlated with increased permeability, at baseline, to smaller molecular weight 4-kD FITC-dextran, suggesting weakly formed endothelial junctions. The CD44-KO EC displayed several characteristics consistent with impaired barrier function/dysfunctional EC junctions, including differential expression, phosphorylation, and localization of endothelial junction proteins, increased matrix metalloprotease expression, and altered cellular morphology. Reduced platelet endothelial cell adhesion molecule-1 (PECAM-1) expression by CD44-KO EC in vivo and in vitro was also observed. Reconstitution of murine CD44 or PECAM-1 restored these defects to near WT status, suggesting CD44 regulates vascular permeability and integrity through a PECAM-1 dependent mechanism.

Mast cell deficiency improves cognition and enhances disease-associated microglia in 5XFAD mice.

Emerging evidence suggests that peripheral immune cells contribute to Alzheimer's disease (AD) neuropathogenesis. Among these, mast cells are known for their functions in allergic reactions and neuroinflammation; however, little is known about their role in AD. Here, we crossed 5XFAD mice with mast cell-deficient strains and observed the effects on AD-related neuropathology and cognitive impairment. We found that mast cell depletion improved contextual fear conditioning in 5XFAD mice without affecting cued fear conditioning, anxiety-like behavior, or amyloid burden. Furthermore, mast cell depletion led to an upregulation of transcriptomic signatures for putatively protective disease-associated microglia and resulted in reduced markers indicative of reactive astrocytes. We hypothesize a system of bidirectional communication between dural mast cells and the brain, where mast cells respond to signals from the brain environment by expressing immune-regulatory mediators, impacting cognition and glial cell function. These findings highlight mast cells as potential therapeutic targets for AD.

Displaced Supracondylar Humerus Fractures in Toddlers.

Gartland type III fracture is the most troublesome type of supracondylar humerus fracture. These injuries most often occur in school age children, but they are seen in pediatric patients of all ages. The goal of this study was to analyze toddlers with Gartland type III fractures to identify clinically significant differences compared with older children. A retrospective cohort study was conducted with 94 toddlers (<3 years) and 378 older children (3 to 12 years). Factors including demographics, mechanism of injury, additional injuries, location of trauma, pin configuration, postoperative complications, follow-up time, and compliance with the treatment plan were collected and compared. The study included 94 toddlers (59% girls, 2.11±0.64 years) and 378 older children (48% girls, 6.32±1.89 years), chosen at random, who were treated between 2000 and 2015. Among toddlers, fractures were more likely to occur at home (P<.001) and to be the result of suspected nonaccidental trauma (P<.001). Older children had more additional injuries (P<.001), but were no more likely to have an open fracture (P=.59) or a flexion-type fracture (P=.42). Older children were more likely to undergo open reduction (P=.03), whereas toddlers were more likely to be treated with a medial pin (P<.001). Toddlers experienced more cubitus varus (P<.001) and loss of reduction (P=.02). No difference was found in length of follow-up (P=.83) or compliance with the treatment plan (P=.11). This study provides novel insights into clinical differences between toddlers and older children with Gartland type III fractures. Knowledge of these differences can facilitate the delivery of targeted, age-specific care for patients with type III supracondylar humerus fractures. [Orthopedics. 2020;43(5);e421-e424.].

Rate of Open Reduction for Supracondylar Humerus Fractures Varies Across Pediatric Orthopaedic Surgeons: A Single-Institution Analysis.

OBJECTIVES: To (1) define a single institution's rate of open reduction for operative pediatric supracondylar humerus (SCH) fractures; (2) describe variability by surgeon in rates of irreducible fracture (IRF) and open reduction; and (3) determine whether variation in opening rate correlated with surgeon experience. DESIGN: Retrospective analytic study. SETTING: Urban tertiary care Level 1 trauma center. PATIENTS/PARTICIPANTS: Twelve fellowship-trained pediatric orthopaedists. MAIN OUTCOME MEASUREMENTS: Rate of open reduction for operatively treated SCH fractures (OTA/AO 13-M/3). RESULTS: One thousand two hundred twenty-nine type II SCH fractures (none of which required open reduction) were excluded from the analysis. A total of 1365 other SCH fractures were included: 1302 type III fractures, 27 type IV fractures, and 36 fractures with unspecified type. 2.9% of type III and 22.2% of type IV fractures required open reduction. None of the injuries with unspecified type required open reduction. The rate of open reduction among 11 surgeons ranged from 0% to 15.0% in type III-IV fractures (P = 0.001). 86% (38/44) of open reductions were performed for IRF. In regression analysis, patient age was associated with open reduction for IRF (odds ratio 1.22, P = 0.001), but surgeon years-in-practice (0.321) and number of previous cases (0.327) were not associated with open reduction. Other indications for opening included suspected vascular or neurologic injury. CONCLUSIONS: Open reduction was rarely performed in this sample, but IRF was the dominant indication for opening. We found true variation in surgeons' rates of performing open reductions. More experience was not correlated with decreased likelihood of open reduction. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Flexion-Type Supracondylar Humeral Fractures: Ulnar Nerve Injury Increases Risk of Open Reduction.

BACKGROUND: The vast majority of displaced pediatric supracondylar humeral fractures can be treated successfully with closed reduction and percutaneous pinning. The need for open reduction is difficult to determine a priori and is typically due to the failure of closed reduction attempts or persistent limb ischemia. The aims of this study were to determine the prevalence of flexion-type supracondylar humeral fractures, the rate of open reduction for flexion-type fractures, and the predictive impact of ulnar nerve injury on the need for open reduction for flexion-type supracondylar humeral fractures. METHODS: We developed a database of consecutive pediatric supracondylar humeral fractures treated operatively at a tertiary care pediatric trauma center from 2000 to 2015. Data recorded included age, mechanism of injury, fracture type (open or closed), fracture pattern (flexion-type or extension-type), concomitant skeletal injury, neurovascular injury, treatment, and surgeon. Radiographs of all flexion-type supracondylar humeral fractures were reviewed in order to confirm the classification of the injury pattern. The rate of open reduction for fractures with a flexion-type injury pattern and for such fractures with and without ulnar nerve injury at presentation was assessed. RESULTS: Of 2,783 consecutive pediatric supracondylar humeral fractures treated by surgeons at our center, 95 (3.4%) were flexion-type fractures. Ulnar nerve injury was noted for 10 (10.5%) of the 95 flexion-type fractures. Open injuries were identified at presentation in 3 (3.2%) of the 95 cases. Among closed fractures, 21 (22.8%) of 92 flexion-type fractures required open reduction compared with 50 (1.9%) of 2,647 extension-type fractures (odds ratio [OR] = 15.4; 95% confidence interval [CI] = 8.8 to 27.0; p < 0.001). Among closed flexion-type fractures, open reduction was performed in 6 (60%) of 10 fractures with associated ulnar nerve injury and in 15 (18.3%) of 82 fractures without ulnar nerve injury (OR = 6.7; 95% CI = 1.7 to 26.7; p = 0.003). CONCLUSIONS: Among closed supracondylar humeral fractures, the flexion-type injury pattern was associated with a 15.4-fold increase in the odds of open reduction. The presence of an ulnar nerve injury at presentation resulted in an additional 6.7-fold higher risk of open reduction among flexion-type supracondylar humeral fractures. Patients and families should be counseled regarding the high rate of open reduction for flexion-type supracondylar humeral fractures, particularly those with an associated ulnar nerve injury. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Aortic Disease Presentation and Outcome Associated With ACTA2 Mutations.

BACKGROUND: ACTA2 mutations are the major cause of familial thoracic aortic aneurysms and dissections. We sought to characterize these aortic diseases in a large case series of individuals with ACTA2 mutations. METHODS AND RESULTS: Aortic disease, management, and outcome associated with the first aortic event (aortic dissection or aneurysm repair) were abstracted from the medical records of 277 individuals with 41 various ACTA2 mutations. Aortic events occurred in 48% of these individuals, with the vast majority presenting with thoracic aortic dissections (88%) associated with 25% mortality. Type A dissections were more common than type B dissections (54% versus 21%), but the median age of onset of type B dissections was significantly younger than type A dissections (27 years versus 36 years). Only 12% of aortic events were repair of ascending aortic aneurysms, which variably involved the aortic root, ascending aorta, and aortic arch. Overall, cumulative risk of an aortic event at age 85 years was 0.76 (95% confidence interval, 0.64-0.86). After adjustment for intrafamilial correlation, sex and race, mutations disrupting p.R179 and p.R258 were associated with significantly increased risk for aortic events, whereas p.R185Q and p.R118Q mutations showed significantly lower risk of aortic events compared with other mutations. CONCLUSIONS: ACTA2 mutations are associated with high risk of presentation with an acute aortic dissection. The lifetime risk for an aortic event is only 76%, suggesting that additional environmental or genetic factors play a role in expression of aortic disease in individuals with ACTA2 mutations.

Modeling the neurovascular niche: unbiased transcriptome analysis of the murine subventricular zone in response to hypoxic insult.

Premature infants often experience chronic hypoxia, resulting in cognitive & motor neurodevelopmental handicaps. These sometimes devastating handicaps are thought to be caused by compromised neural precursor cell (NPC) repair/recovery resulting in variable central nervous system (CNS) repair/recovery. We have identified differential responses of two mouse strains (C57BL/6 & CD1) to chronic hypoxia that span the range of responsiveness noted in the premature human population. We previously correlated several CNS tissue and cellular behaviors with the different behavioral parameters manifested by these two strains. In this report, we use unbiased array technology to interrogate the transcriptome of the subventricular zone (SVZ) in these strains. Our results illustrate differences in mRNA expression in the SVZ of both C57BL/6 and CD1 mice following hypoxia as well as differences between C57BL/6 and CD1 SVZ under both normoxic and hypoxic conditions. Differences in expression were found in gene sets associated with Sox10-mediated neural functions that explain, in part, the differential cognitive and motor responsiveness to hypoxic insult. This may shed additional light on our understanding of the variable responses noted in the human premature infant population and facilitate early intervention approaches. Further interrogation of the differentially expressed gene sets will provide a more complete understanding of the differential responses to, and recovery from, hypoxic insult allowing for more informed modeling of the ranges of disease severity observed in the very premature human population.

Optical characterization of multilayer stacks used as phase-change media of optical disk data storage.

We report results of measurements of the optical constants of the dielectric layer (ZnS-SiO2), reflecting layer (aluminum-chromium alloy), and phase-change layer (GeSbTe, AgInSbTe) used as the media of phase-change optical recording. The refractive index n and the absorption coefficient k of these materials vary to some extent with the film thickness and with the film deposition environment. We report the observed variations of optical constants among samples of differing structure and among samples fabricated in different laboratories.