Mitotic bookmarking by SWI/SNF subunits.

For cells to initiate and sustain a differentiated state, it is necessary that a 'memory' of this state is transmitted through mitosis to the daughter cells1-3. Mammalian switch/sucrose non-fermentable (SWI/SNF) complexes (also known as Brg1/Brg-associated factors, or BAF) control cell identity by modulating chromatin architecture to regulate gene expression4-7, but whether they participate in cell fate memory is unclear. Here we provide evidence that subunits of SWI/SNF act as mitotic bookmarks to safeguard cell identity during cell division. The SWI/SNF core subunits SMARCE1 and SMARCB1 are displaced from enhancers but are bound to promoters during mitosis, and we show that this binding is required for appropriate reactivation of bound genes after mitotic exit. Ablation of SMARCE1 during a single mitosis in mouse embryonic stem cells is sufficient to disrupt gene expression, impair the occupancy of several established bookmarks at a subset of their targets and cause aberrant neural differentiation. Thus, SWI/SNF subunit SMARCE1 has a mitotic bookmarking role and is essential for heritable epigenetic fidelity during transcriptional reprogramming.

Genomewide CRISPR knockout screen identified PLAC8 as an essential factor for SADS-CoVs infection.

Zoonotic transmission of coronaviruses poses an ongoing threat to human populations. Endemic outbreaks of swine acute diarrhea syndrome coronavirus (SADS-CoV) have caused severe economic losses in the pig industry and have the potential to cause human outbreaks. Currently, there are no vaccines or specific antivirals against SADS-CoV, and our limited understanding of SADS-CoV host entry factors could hinder prompt responses to a potential human outbreak. Using a genomewide CRISPR knockout screen, we identified placenta-associated 8 protein (PLAC8) as an essential host factor for SADS-CoV infection. Knockout of PLAC8 abolished SADS-CoV infection, which was restored by complementing PLAC8 from multiple species, including human, rhesus macaques, mouse, pig, pangolin, and bat, suggesting a conserved infection pathway and susceptibility of SADS-CoV among mammals. Mechanistically, PLAC8 knockout does not affect viral entry; rather, knockout cells displayed a delay and reduction in viral subgenomic RNA expression. In a swine primary intestinal epithelial culture (IEC) infection model, differentiated cultures have high levels of PLAC8 expression and support SADS-CoV replication. In contrast, expanding IECs have low levels of PLAC8 expression and are resistant to SADS-CoV infection. PLAC8 expression patterns translate in vivo; the immunohistochemistry of swine ileal tissue revealed high levels of PLAC8 protein in neonatal compared to adult tissue, mirroring the known SADS-CoV pathogenesis in neonatal piglets. Overall, PLAC8 is an essential factor for SADS-CoV infection and may serve as a promising target for antiviral development for potential pandemic SADS-CoV.

SARS-CoV-2 infection of airway cells causes intense viral and cell shedding, two spreading mechanisms affected by IL-13.

Muco-obstructive lung diseases are typically associated with high risks of COVID-19 severity; however, allergic asthma showed reduced susceptibility. To investigate viral spread, primary human airway epithelial (HAE) cell cultures were infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and host­virus interactions were examined via electron microscopy, immunohistochemistry, RNA in situ hybridization, and gene expression analyses. In HAE cell cultures, angiotensin-converting enzyme 2 (ACE2) expression governed cell tropism and viral load and was up-regulated by infection. Electron microscopy identified intense viral egress from infected ciliated cells and severe cytopathogenesis, culminating in the shedding of ciliated cells packed with virions, providing a large viral reservoir for spread and transmission. Intracellular stores of MUC5AC, a major airway mucin involved in asthma, were rapidly depleted, likely to trap viruses. To mimic asthmatic airways, HAE cells were treated with interleukin-13 (IL-13), which reduced viral titers, viral messenger RNA, and cell shedding, and significantly diminished the number of infected cells. Although mucus hyperproduction played a shielding role, IL-13­treated cells maintained a degree of protection despite the removal of mucus. Using Gene Expression Omnibus databases, bulk RNA-sequencing analyses revealed that IL-13 up-regulated genes controlling glycoprotein synthesis, ion transport, and antiviral processes (albeit not the typical interferon-induced genes) and down-regulated genes involved in cilial function and ribosomal processing. More precisely, we showed that IL-13 reduced ACE2 expression, intracellular viral load, and cell-to-cell transmission while increasing the cilial keratan sulfate coating. In conclusion, intense viral and cell shedding caused by SARS-CoV-2 infection was attenuated by IL-13, which affected viral entry, replication, and spread.

A Pathogenic Missense Mutation in Kainate Receptors Elevates Dendritic Excitability and Synaptic Integration through Dysregulation of SK Channels.

Numerous rare variants that cause neurodevelopmental disorders (NDDs) occur within genes encoding synaptic proteins, including ionotropic glutamate receptors. However, in many cases, it remains unclear how damaging missense variants affect brain function. We determined the physiological consequences of an NDD causing missense mutation in the GRIK2 kainate receptor (KAR) gene, that results in a single amino acid change p.Ala657Thr in the GluK2 receptor subunit. We engineered this mutation in the mouse Grik2 gene, yielding a GluK2(A657T) mouse, and studied mice of both sexes to determine how hippocampal neuronal function is disrupted. Synaptic KAR currents in hippocampal CA3 pyramidal neurons from heterozygous A657T mice exhibited slow decay kinetics, consistent with incorporation of the mutant subunit into functional receptors. Unexpectedly, CA3 neurons demonstrated elevated action potential spiking because of downregulation of the small-conductance Ca2+ activated K+ channel (SK), which mediates the post-spike afterhyperpolarization. The reduction in SK activity resulted in increased CA3 dendritic excitability, increased EPSP-spike coupling, and lowered the threshold for the induction of LTP of the associational-commissural synapses in CA3 neurons. Pharmacological inhibition of SK channels in WT mice increased dendritic excitability and EPSP-spike coupling, mimicking the phenotype in A657T mice and suggesting a causative role for attenuated SK activity in aberrant excitability observed in the mutant mice. These findings demonstrate that a disease-associated missense mutation in GRIK2 leads to altered signaling through neuronal KARs, pleiotropic effects on neuronal and dendritic excitability, and implicate these processes in neuropathology in patients with genetic NDDs.SIGNIFICANCE STATEMENT Damaging mutations in genes encoding synaptic proteins have been identified in various neurodevelopmental disorders, but the functional consequences at the cellular and circuit level remain elusive. By generating a novel knock-in mutant mouse, this study examined the role of a pathogenic mutation in the GluK2 kainate receptor (KAR) subunit, a subclass of ionotropic glutamate receptors. Analyses of hippocampal CA3 pyramidal neurons determined elevated action potential firing because of an increase in dendritic excitability. Increased dendritic excitability was attributable to reduced activity of a Ca2+ activated K+ channel. These results indicate that a pathogenic KAR mutation results in dysregulation of dendritic K+ channels, which leads to an increase in synaptic integration and backpropagation of action potentials into distal dendrites.

Clustered mutations in the GRIK2 kainate receptor subunit gene underlie diverse neurodevelopmental disorders.

Kainate receptors (KARs) are glutamate-gated cation channels with diverse roles in the central nervous system. Bi-allelic loss of function of the KAR-encoding gene GRIK2 causes a nonsyndromic neurodevelopmental disorder (NDD) with intellectual disability and developmental delay as core features. The extent to which mono-allelic variants in GRIK2 also underlie NDDs is less understood because only a single individual has been reported previously. Here, we describe an additional eleven individuals with heterozygous de novo variants in GRIK2 causative for neurodevelopmental deficits that include intellectual disability. Five children harbored recurrent de novo variants (three encoding p.Thr660Lys and two p.Thr660Arg), and four children and one adult were homozygous for a previously reported variant (c.1969G>A [p.Ala657Thr]). Individuals with shared variants had some overlapping behavioral and neurological dysfunction, suggesting that the GRIK2 variants are likely pathogenic. Analogous mutations introduced into recombinant GluK2 KAR subunits at sites within the M3 transmembrane domain (encoding p.Ala657Thr, p.Thr660Lys, and p.Thr660Arg) and the M3-S2 linker domain (encoding p.Ile668Thr) had complex effects on functional properties and membrane localization of homomeric and heteromeric KARs. Both p.Thr660Lys and p.Thr660Arg mutant KARs exhibited markedly slowed gating kinetics, similar to p.Ala657Thr-containing receptors. Moreover, we observed emerging genotype-phenotype correlations, including the presence of severe epilepsy in individuals with the p.Thr660Lys variant and hypomyelination in individuals with either the p.Thr660Lys or p.Thr660Arg variant. Collectively, these results demonstrate that human GRIK2 variants predicted to alter channel function are causative for early childhood development disorders and further emphasize the importance of clarifying the role of KARs in early nervous system development.

Retrograde intramedullary nailing of the femur: identifying the true anatomic axis for the ideal start point.

PURPOSE: Retrograde femoral intramedullary nailing (IMN) is commonly used to treat distal femur fractures. There is variability in the literature regarding the ideal starting point for retrograde femoral IMN in the coronal plane. The objective of this study was to identify the ideal starting point, based on radiographs, relative to the intercondylar notch in the placement of a retrograde femoral IMN. METHODS: A consecutive series of 48 patients with anteroposterior long-leg radiographs prior to elective knee arthroplasty from 2017 to 2021 were used to determine the femoral anatomic axis. The anatomic center of the isthmus was identified and marked. Another point 3 cm distal from the isthmus was marked in the center of the femoral canal. A line was drawn connecting the points and extended longitudinally through the distal femur. The distance from the center of the intercondylar notch to the point where the anatomic axis of the femur intersected the distal femur was measured. RESULTS: On radiographic review, the distance from the intercondylar notch to where the femoral anatomic axis intersects the distal femur was normally distributed with an average distance of 4.1 mm (SD, 1.7 mm) medial to the intercondylar notch. CONCLUSION: The ideal start point, based on radiographs, for retrograde femoral intramedullary nailing is approximately 4.1 mm medial to the intercondylar notch. Medialization of the starting point for retrograde intramedullary nailing in the coronal plane aligns with the anatomic axis. These results support the integration of templating into preoperative planning prior to retrograde IMN of the femur, with the knowledge that, on average, the ideal start point will be slightly medial. Further investigation via anatomic studies is required to determine whether a medial start point is safe and efficacious in patients with distal femur fractures treated with retrograde IMNs.

Contemporary outcomes of open repair of acute complicated type B aortic dissection.

OBJECTIVE: Open repair of acute complicated type B aortic dissection (ACTBAD), required when endovascular repair is not possible, is historically considered high-risk. We analyze our experience with this high-risk cohort compared with the standard cohort. METHODS: We identified consecutive patients undergoing descending thoracic or thoracoabdominal aortic aneurysm (TAAA) repair from 1997 to 2021. Patients with ACTBAD were compared with those having surgery for other reasons. Logistic regression was used to identify associations with major adverse events (MAEs). Five-year survival and competing risk of reintervention were calculated. RESULTS: Of 926 patients, 75 (8.1%) had ACTBAD. Indications included rupture (25/75), malperfusion (11/75), rapid expansion (26/75), recurrent pain (12/75), large aneurysm (5/75), and uncontrolled hypertension (1/75). The incidence of MAEs was similar (13.3% [10/75] vs 13.7% [117/851], P = .99). Operative mortality was 5.3% (4/75) vs 4.8% (41/851) (P = .99). Complications included tracheostomy (8%, 6/75), spinal cord ischemia (4%, 3/75), and new dialysis (2.7%, 2/75). Renal impairment, urgent/emergent operation, forced expiratory volume in 1 second ≤50%, and malperfusion were associated with MAEs, but not ACTBAD (odds ratio: 0.48, 95% confidence interval [CI]: [0.20-1.16], P = .1). At 5 and 10 years, there was no difference in survival (65.8% [95% CI: 54.6-79.2] vs 71.3% [95% CI: 67.9-74.9], P = .42, and 47.3% [95% CI: 34.5-64.7] vs 53.7% [95% CI: 49.3-58.4], P = .29, respectively) or 10-year reintervention (12.5% [95% CI: 4.3-25.3] vs 7.1% [95% CI: 4.7-10.1], P = .17, respectively). CONCLUSIONS: In an experienced center, open repair of ACTBAD can be performed with low rates of operative mortality and morbidity. Outcomes similar to elective repair are achievable even in high-risk patients with ACTBAD. In patients unsuitable for endovascular repair, transfer to a high-volume center experienced in open repair should be considered.

Mitigating the Isolation of Minoritized Faculty in Academic Medicine.

Increasing numbers of faculty who are underrepresented in medicine has been a focus of academic health systems. Understanding the experiences of these faculty helps in creating environments that are inclusive and supportive, promoting faculty success. When compared with non-minoritized faculty, minoritized faculty face racism, isolation, diversity efforts disparities, clinical efforts disparities, lack of faculty development, and promotion disparities. While there have been contributions to the literature to better characterize disparities faced by minoritized faculty, little has been written about isolation. Isolation occurs when faculty underrepresented in medicine do not feel like part of the department or institution. They may feel excluded from mainstream culture as if they are invisible. They may be excluded from conversations, group chats, get togethers, or other work-related or social functions. These feelings can manifest as imposter syndrome and impact work performance and decision-making. In this article, the author shares how to recognize and mitigate isolation to promote an inclusive environment for all faculty.

Alveolar, Endothelial, and Organ Injury Marker Dynamics in Severe COVID-19.

Rationale: Alveolar and endothelial injury may be differentially associated with coronavirus disease (COVID-19) severity over time. Objectives: To describe alveolar and endothelial injury dynamics and associations with COVID-19 severity, cardiorenovascular injury, and outcomes. Methods: This single-center observational study enrolled patients with COVID-19 requiring respiratory support at emergency department presentation. More than 40 markers of alveolar (including receptor for advanced glycation endproducts [RAGE]), endothelial (including angiopoietin-2), and cardiorenovascular injury (including renin, kidney injury molecule-1, and troponin-I) were serially compared between invasively and spontaneously ventilated patients using mixed-effects repeated-measures models. Ventilatory ratios were calculated for intubated patients. Associations of biomarkers with modified World Health Organization scale at Day 28 were determined with multivariable proportional-odds regression. Measurements and Main Results: Of 225 patients, 74 (33%) received invasive ventilation at Day 0. RAGE was 1.80-fold higher in invasive ventilation patients at Day 0 (95% confidence interval [CI], 1.50-2.17) versus spontaneous ventilation, but decreased over time in all patients. Changes in alveolar markers did not correlate with changes in endothelial, cardiac, or renal injury markers. In contrast, endothelial markers were similar to lower at Day 0 for invasive ventilation versus spontaneous ventilation, but then increased over time only among intubated patients. In intubated patients, angiopoietin-2 was similar (fold difference, 1.02; 95% CI, 0.89-1.17) to nonintubated patients at Day 0 but 1.80-fold higher (95% CI, 1.56-2.06) at Day 3; cardiorenovascular injury markers showed similar patterns. Endothelial markers were not consistently associated with ventilatory ratios. Endothelial markers were more often significantly associated with 28-day outcomes than alveolar markers. Conclusions: Alveolar injury markers increase early. Endothelial injury markers increase later and are associated with cardiorenovascular injury and 28-day outcome. Alveolar and endothelial injury likely contribute at different times to disease progression in severe COVID-19.

Noonan syndrome associated with hypoplastic left heart syndrome.

Noonan syndrome is an inherited disorder caused by alterations in the RAS-MAPK pathway. There have been several identified genotype-phenotype associations made with respect to congenital cardiac lesions and Noonan syndrome variants, but limited data exist regarding single ventricle disease in this population. Here, we report two patients with PTPN11-related Noonan syndrome and hypoplastic left heart syndrome variants.

Radiographic and histologic characterisation of white matter injury in a sheep model of CHD.

Nearly one in five children with CHD is born with white matter injury that can be recognised on postnatal MRI by the presence of T1 hyperintense lesions. This pattern of white matter injury is known to portend poor neurodevelopmental outcomes, but the exact aetiology and histologic characterisation of these lesions have never been described. A fetal sheep was cannulated at gestational age 110 days onto a pumpless extracorporeal oxygenator via the umbilical vessels and supported in a fluid environment for 14.5 days. The fetus was supported under hypoxic conditions (mean oxygen delivery 16 ml/kg/day) to simulate the in utero conditions of CHD. At necropsy, the brain was fixed, imaged with MRI, and then stained to histologically identify areas of injury. Under hypoxemic in utero conditions, the fetus developed a T1 hyperintense lesion in its right frontal lobe. Histologically, this lesion was characterised by microvascular proliferation and astrocytosis without gliosis. These findings may provide valuable insight into the aetiology of white matter injury in neonates with CHD.

Are committee experiences of minoritized family medicine faculty part of the minority tax? a qualitative study.

BACKGROUND AND OBJECTIVES: Because much of the work in academic medicine is done by committee, early career URiM faculty, are often asked to serve on multiple committees, including diversity work that may not be recognized as important. They may also be asked to serve on committees to satisfy a diversity "check box," and may be asked more often than their non-URiM peers to serve in this capacity. We sought to describe the committee experiences of early career URiM faculty, hypothesizing that they may see committee service as a minority tax. METHODS: Participants in the Leadership through Scholarship Fellowship (LTSF) were asked to share their experiences with committee service in their careers after participating in a faculty development discussion. Their responses were analyzed and reported using qualitative, open, axial, and abductive reasoning methods. RESULTS: Four themes, with eight sub-themes (in parenthesis), emerged from the content analysis of the LTSF fellows responses to the prompt: Time commitment (Timing of committee work and lack of protected time for research and scholarship), URiM Committee service (Expectation that URiM person will serve on committees and consequences for not serving), Mentoring issues (no mentoring regarding committee service, faculty involvement is lacking and the conflicting nature of committee work) and Voice (Lack of voice or acknowledgement). CONCLUSIONS: Early career URiM faculty reported an expectation of serving on committees and consequences for not serving related to their identity, but other areas of committee service they shared were not connected to their URiM identity. Because most of the experiences were not connected to the LTSF fellows' URiM identity, this group has identified areas of committee service that may affect all early career faculty. More research is necessary to determine how committee service affects URiM and non-URiM faculty in academic family medicine.

Treatment of cystic fibrosis airway cells with CFTR modulators reverses aberrant mucus properties via hydration.

QUESTION: Cystic fibrosis (CF) is characterised by the accumulation of viscous adherent mucus in the lungs. While several hypotheses invoke a direct relationship with cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction (i.e. acidic airway surface liquid (ASL) pH, low bicarbonate (HCO3 -) concentration, airway dehydration), the dominant biochemical alteration of CF mucus remains unknown. MATERIALS/METHODS: We characterised a novel cell line (CFTR-KO Calu3 cells) and the responses of human bronchial epithelial (HBE) cells from subjects with G551D or F508del mutations to ivacaftor and elexacaftor-tezacaftor-ivacaftor. A spectrum of assays such as short-circuit currents, quantitative PCR, ASL pH, Western blotting, light scattering/refractometry (size-exclusion chromatography with inline multi-angle light scattering), scanning electron microscopy, percentage solids and particle tracking were performed to determine the impact of CFTR function on mucus properties. RESULTS: Loss of CFTR function in Calu3 cells resulted in ASL pH acidification and mucus hyperconcentration (dehydration). Modulation of CFTR in CF HBE cells did not affect ASL pH or mucin mRNA expression, but decreased mucus concentration, relaxed mucus network ultrastructure and improved mucus transport. In contrast with modulator-treated cells, a large fraction of airway mucins remained attached to naïve CF cells following short apical washes, as revealed by the use of reducing agents to remove residual mucus from the cell surfaces. Extended hydration, but not buffers alkalised with sodium hydroxide or HCO3 -, normalised mucus recovery to modulator-treated cell levels. CONCLUSION: These results indicate that airway dehydration, not acidic pH and/or low [HCO3 -], is responsible for abnormal mucus properties in CF airways and CFTR modulation predominantly restores normal mucin entanglement.

Implementing High-Quality Primary Care Through a Health Equity Lens.

The COVID-19 pandemic highlighted the importance of centering health equity in future health system and primary care reforms. Strengthening primary care will be needed to correct the longstanding history of mistreatment of First Nations/Indigenous and racialized people, exclusion of health care workers of color, and health care access and outcome inequities further magnified by the COVID-19 pandemic. The National Academies of Sciences, Engineering, and Medicine (NASEM) released a report on Implementing High-Quality Primary Care: Rebuilding the Foundation of Health Care, that provided a framework for defining high-quality primary care and proposed 5 recommendations for implementing that definition. Using the report's framework, we identified health equity challenges and opportunities with examples from primary care systems in the United States and Canada. We are poised to reinvigorate primary care because the recent pandemic and the attention to continued racialized police violence sparked renewed conversations and collaborations around equity, diversity, inclusion, and health equity that have been long overdue. The time to transition those conversations to actionable items to improve the health of patients, families, and communities is now.Appeared as Annals "Online First" article.

Chronic foetal hypoxaemia does not cause elevation of serum markers of brain injury.

OBJECTIVES: The objective of this study was to investigate changes in serum biomarkers of acute brain injury, including white matter and astrocyte injury during chronic foetal hypoxaemia. We have previously shown histopathological changes in myelination and neuronal density in fetuses with chronic foetal hypoxaemia at a level consistent with CHD. METHODS: Mid-gestation foetal sheep (110 ± 3 days gestation) were cannulated and attached to a pumpless, low-resistance oxygenator circuit, and incubated in a sterile fluid environment mimicking the intrauterine environment. Fetuses were maintained with an oxygen delivery of 20-25 ml/kg/min (normoxemia) or 14-16 ml/kg/min (hypoxaemia). Myelin Basic Protein and Glial Fibrillary Acidic Protein serum levels in the two groups were assessed by ELISA at baseline and at 7, 14, and 21 days of support. RESULTS: Based on overlapping 95% confidence intervals, there were no statistically significant differences in either Myelin Basic Protein or Glial Fibrillary Acidic Protein serum levels between the normoxemic and hypoxemic groups, at any time point. No statistically significant correlations were observed between oxygen delivery and levels of Myelin Basic Protein and Glial Fibrillary Acidic Protein. CONCLUSION: Chronic foetal hypoxaemia during mid-gestation is not associated with elevated serum levels of acute white matter (Myelin Basic Protein) or astrocyte injury (Glial Fibrillary Acidic Protein), in this model. In conjunction with our previously reported findings, our data support the hypothesis that the brain dysmaturity with impaired myelination found in fetuses with chronic hypoxaemia is caused by disruption of normal developmental pathways rather than by direct cellular injury.

Towards a common lexicon for equity, diversity, and inclusion work in academic medicine.

Differential rewarding of work and experience has been a longtime feature of academic medicine, resulting in a series of academic disparities. These disparities have been collectively called a cultural or minority "tax," and, when considered beyond academic medicine, exist across all departments, colleges, and schools of institutions of higher learning-from health sciences to disciplines located on university campuses outside of medicine and health. A shared language can provide opportunities for those who champion this work to pool resources for larger impacts across the institution. This article aims to catalog the terms used across academic medicine disciplines to establish a common language describing the inequities experienced by Black, Latinx, American Indian/Alaska Native and Native Hawaiian/Other Pacific Islander, Women, and other underrepresented people as well as queer, disabled, and other historically marginalized or excluded groups. These ideas are specific to academic medicine in the United States, although many can be used in academic medicine in other countries. The terms were selected by a team of experts in equity, diversity, and inclusion, (EDI) who are considered national thought leaders in EDI and collectively have over 100 years of scholarship and experience in this area.

Mucins and CFTR: Their Close Relationship.

Mucociliary clearance is a critical defense mechanism for the lungs governed by regionally coordinated epithelial cellular activities, including mucin secretion, cilia beating, and transepithelial ion transport. Cystic fibrosis (CF), an autosomal genetic disorder caused by the dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) channel, is characterized by failed mucociliary clearance due to abnormal mucus biophysical properties. In recent years, with the development of highly effective modulator therapies, the quality of life of a significant number of people living with CF has greatly improved; however, further understanding the cellular biology relevant to CFTR and airway mucus biochemical interactions are necessary to develop novel therapies aimed at restoring CFTR gene expression in the lungs. In this article, we discuss recent advances of transcriptome analysis at single-cell levels that revealed a heretofore unanticipated close relationship between secretory MUC5AC and MUC5B mucins and CFTR in the lungs. In addition, we review recent findings on airway mucus biochemical and biophysical properties, focusing on how mucin secretion and CFTR-mediated ion transport are integrated to maintain airway mucus homeostasis in health and how CFTR dysfunction and restoration of function affect mucus properties.

Contrast-Enhanced Brain Ultrasound Perfusion Metrics in the EXTra-Uterine Environment for Neonatal Development (EXTEND): Correlation With Hemodynamic Parameters.

OBJECTIVES: Contrast-enhanced ultrasound (CEUS) can provide quantitative perfusion metrics and may be useful to detect cerebral pathology in neonates and premature infants, particularly in extrauterine environments. The effect of hemodynamics on cerebral perfusion metrics is unknown, which limits the clinical application of this technology. We aimed to determine associations between systemic hemodynamics and concurrently measured brain perfusion parameters in an animal model of extrauterine support. METHODS: Nine fetal lambs were transferred to an extrauterine support device. Lumason® ultrasound contrast (0.1-0.3 ml) was administered via the umbilical vein and 90-second cine clips were obtained. Time-intensity-curves (TICs) were generated and time-dependent and area-under-curve (AUC) parameters were derived. Associations between brain perfusion metrics and hemodynamics including heart rate (HR) and mean arterial pressure (MAP) were evaluated by multilevel linear mixed-effects models. RESULTS: Eighty-six ultrasound examinations were performed and 72 examinations were quantifiable. Time-dependent measurements were independent of all hemodynamic parameters (all p ≥.05). Oxygen delivery and mean blood flow were correlated with AUC measurements (all p ≤.01). Physiologic HR and MAP were not correlated with any measurements (all p ≥.05). CONCLUSION: Detected aberrations in time-dependent CEUS measurements are not correlated with hemodynamic parameters and are thought to reflect the changes in cerebral blood flow, thus providing a promising tool for evaluation of brain perfusion. CEUS brain perfusion parameters are not correlated with physiologic HR and MAP, but AUC-dependent measurements are correlated with oxygen delivery and blood flow, suggesting that CEUS offers additional value over standard monitoring. Overall, these findings enhance the applicability of this technology.

Immersion in Raloxifene does not significantly improve bone toughness or screw pull-out strength in multiple in vitro models.

BACKGROUND: Failure of surgical fixation in orthopaedic fractures occurs at a significantly higher rate in osteoporotic patients due to weakened osteoporotic bone. A therapy to acutely improve the mechanical properties of bone during fracture repair would have profound clinical impact. A previous study has demonstrated an increase in mechanical properties of acellular cortical canine bone after immersion in raloxifene. The goal of this study was to determine if similar treatment yields the same results in cancellous fetal bovine bone and whether this translates into a difference in screw pull-out strength in human cadaveric tissue. METHODS: Cancellous bone from fetal bovine distal femora underwent quasi-static four-point bending tests after being immersed in either raloxifene (20 µM) or phosphate-buffered saline as a control for 7 days (n = 10). Separately, 5 matched pairs of human osteoporotic cadaveric humeral heads underwent the same procedure. Five 3.5 mm unicortical cancellous screws were then inserted at standard surgical fixation locations to a depth of 30 mm and quasi-static screw pull-out tests were performed. RESULTS: In the four-point bending tests, there were no significant differences between the raloxifene and control groups for any of the mechanical properties - including stiffness (p = 0.333) and toughness (p = 0.546). In the screw pull-out tests, the raloxifene soaked samples and control samples had pullout strengths of 122 ± 74.3 N and 89.5 ± 63.8 N, respectively. CONCLUSIONS: Results from this study indicate that cancellous fetal bovine samples did not demonstrate an increase in toughness with raloxifene treatment, which is in contrast to previously published data that studied canine cortical bone. In vivo experiments are likely required to determine whether raloxifene will improve implant fixation.

Quantitative contrast-enhanced ultrasound of the brain on twin fetal lambs maintained by the extrauterine environment for neonatal development (EXTEND): initial experience.

BACKGROUND: With the development of an artificial environment to support the extremely premature infant, advanced imaging techniques tested in this extrauterine system might be beneficial to evaluate the fetal brain. OBJECTIVE: We evaluated the feasibility of (a) performing contrast-enhanced ultrasound (CEUS) and (b) quantifying normal and decreased brain perfusion in fetal lambs maintained on the extrauterine environment for neonatal development (EXTEND) system. MATERIALS AND METHODS: Twin premature fetal lambs (102 days of gestational age) were transferred to the EXTEND system. Twin B was subjected to sub-physiological flows (152 mL/kg/min) and oxygen delivery (15.9 mL/kg/min), while Twin A was maintained at physiological levels. We administered Lumason contrast agent into the oxygenator circuit and performed serial CEUS examinations. We quantified perfusion parameters and generated parametric maps. We also recorded hemodynamic parameters, serum blood analysis, and measurements across the oxygenator. Postmortem MRIs were performed. RESULTS: No significant changes in hemodynamic variables were attributable to CEUS examinations. On gray-scale images, Twin B demonstrated ventriculomegaly and progressive parenchymal volume loss culminating in hydranencephaly. By CEUS, Twin B demonstrated decreased peak enhancement and decreased overall parenchymal perfusion when compared to Twin A by perfusion parameters and parametric maps. Changes in perfusion parameters were detected immediately following blood transfusion. Postmortem MRI confirmed ultrasonographic findings in Twin B. CONCLUSION: In this preliminary experience, we show that CEUS of the brain is feasible in fetal lambs maintained on the EXTEND system and that changes in perfusion can be quantified, which is promising for the application of CEUS in this extrauterine system supporting the premature infant.