Association Between MR Elastography Liver Stiffness and Histologic Liver Fibrosis in Children and Young Adults With Autoimmune Liver Disease.

Background: Liver fibrosis is an important clinical endpoint of progression of autoimmune liver disease (AILD); its monitoring would benefit from noninvasive imaging tools. Objective: To assess the relationship between MR elastography (MRE) liver stiffness measurements and histologic liver fibrosis, as well as to evaluate the performance of MRE and biochemical-based clinical markers for stratifying histologic liver fibrosis severity, in children and young adults with AILD. Methods: This retrospective study used an existing institutional registry of children and young adults diagnosed with AILD [primary sclerosing cholangitis (PSC), ASC (autoimmune sclerosing cholangitis), or AIH (autoimmune hepatitis)]. The registry was searched to identify patients who underwent both a research abdominal 1.5-T MRI that included liver MRE (performed for registry enrollment) and a clinically indicated liver biopsy within a 6-month interval. MRE used a 2D gradient-recalled echo sequence. One analyst measured mean liver shear stiffness (kPa) for each examination. Laboratory markers of liver fibrosis [aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 score (FIB-4)] were recorded. For investigational purposes, one pathologist determined histologic METAVIR liver fibrosis stage, blinded to clinical and MRI data. Spearman rank-order correlation was calculated between MRE liver stiffness and METAVIR liver fibrosis stage. ROC analysis was used to evaluate diagnostic performance for identifying advanced fibrosis (i.e., differentiating METAVIR F0-F1 from F2-F4 fibrosis), calculating sensitivity and specificity at the Youden's index. Results: The study included 46 patients (median [IQR] age, 16.6 [13.7-17.8] years; 20 female, 26 male); 12 had PSC, 10 had ASC, and 24 had AIH. Median MRE liver stiffness was 2.9 kPa (IQR: 2.2-4.0 kPa). MRE liver stiffness and METAVIR fibrosis stage showed strong positive correlation (rho=0.68). For identifying advanced liver fibrosis, MRE liver stiffness had AUC of 0.81, with sensitivity of 65.4% and specificity of 90.0%; APRI had AUC of 0.72, with sensitivity of 60.0% and specificity of 85.0%; and FIB-4 had AUC of 0.71, with sensitivity of 64.0% and 85.0%. Conclusion: MRE liver stiffness measurements were associated with histologic liver fibrosis severity. Clinical Impact: The findings support a role for MRE in noninvasive monitoring of liver stiffness, a surrogate for fibrosis, in children and young adults with AILD.

Induced pluripotent stem cell (iPSC) modeling validates reduced GBE1 enzyme activity due to a novel variant, p.Ile694Asn, found in a patient with suspected glycogen storage disease IV.

Background: Glycogen Storage disease type 4 (GSD4), a rare disease caused by glycogen branching enzyme 1 (GBE1) deficiency, affects multiple organ systems including the muscles, liver, heart, and central nervous system. Here we report a GSD4 patient, who presented with severe hepatosplenomegaly and cardiac ventricular hypertrophy. GBE1 sequencing identified two variants: a known pathogenic missense variant, c.1544G>A (p.Arg515His), and a missense variant of unknown significance (VUS), c.2081T>A (p. Ile694Asn). As a liver transplant alone can exacerbate heart dysfunction in GSD4 patients, a precise diagnosis is essential for liver transplant indication. To characterize the disease-causing variant, we modeled patient-specific GBE1 deficiency using CRISPR/Cas9 genome-edited induced pluripotent stem cells (iPSCs). Methods: iPSCs from a healthy donor (iPSC-WT) were genome-edited by CRISPR/Cas9 to induce homozygous p.Ile694Asn in GBE1 (iPSC-GBE1-I694N) and differentiated into hepatocytes (iHep) or cardiomyocytes (iCM). GBE1 enzyme activity was measured, and PAS-D staining was performed to analyze polyglucosan deposition in these cells. Results: iPSCGBE1-I694N differentiated into iHep and iCM exhibited reduced GBE1 protein level and enzyme activity in both cell types compared to iPSCwt. Both iHepGBE1-I694N and iCMGBE1-I694N showed polyglucosan deposits correlating to the histologic patterns of the patient's biopsies. Conclusions: iPSC-based disease modeling supported a loss of function effect of p.Ile694Asn in GBE1. The modeling of GBE1 enzyme deficiency in iHep and iCM cell lines had multi-organ findings, demonstrating iPSC-based modeling usefulness in elucidating the effects of novel VUS in ultra-rare diseases.

Cardiac atrial pathology in Duchenne muscular dystrophy.

INTRODUCTION/AIMS: Duchenne muscular dystrophy (DMD) is characterized by fibrofatty replacement of muscle. This has been documented in the ventricular myocardium of DMD patients, but there is limited description of atrial involvement. The purpose of this study is to examine the arrhythmia and ectopy burden in patients with DMD and non-DMD dilated cardiomyopathy (DCM) and to characterize the cardiac histopathologic changes in DMD patients across the disease spectrum. METHODS: This was a retrospective analysis of age-matched patients with DMD and non-DMD DCM who received a Holter monitor and cardiac imaging within 100 days of each other between 2010 and 2020. Twenty-four-hour Holter monitors were classified based on the most recent left ventricular ejection fraction at the time of monitoring. Cardiac histopathologic specimens from whole-heart examinations at the time of autopsy from three DMD patients and one DCM patient were reviewed. RESULTS: A total of 367 patients with 1299 Holter monitor recordings were included over the study period, with 94% representing DMD patients and 6% non-DMD DCM. Patients with DMD had more atrial ectopy across the cardiac function spectrum (p < 0.05). There was no difference in ventricular ectopy. Four DMD patients developed symptomatic atrial arrhythmias. Autopsy specimens from DMD patients demonstrated fibrofatty infiltration of both atrial and ventricular myocardium. DISCUSSION: The atrial myocardium in patients with DMD is unique. Autopsy specimens reveal fibofatty replacement of the atrial myocardium, which may be a nidus for both ectopy and arrhythmias in DMD patients.

Comprehensive cardiac magnetic resonance T1, T2, and extracellular volume mapping to define Duchenne cardiomyopathy.

BACKGROUND: Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD). Cardiac magnetic resonance (CMR) parametric mapping sequences offer insights into disease pathophysiology. We propose a novel approach by leveraging T2 mapping in conjunction with T1 and extracellular volume (ECV) mapping to perform a virtual myocardial biopsy. While previous work has attempted to describe myocardial changes in DMD, our inclusion of T2 mapping enables comprehensive categorization of myocardial tissue characteristics of fibrosis, edema, and fat to better understand the pathological composition of the myocardium with disease progression. METHODS: DMD patients (n = 49; median: 12 years-old) underwent CMR, including T1, T2, and ECV. Categories were defined as normal, isolated high T1 (normal ECV, high T1, normal T2), fibrosis (high ECV, normal or high T1, normal T2), edema (normal or high ECV, normal or high T1, high T2), fat (normal ECV, low T1, high T2) or fibrofatty (high ECV, low T1, high T2). RESULTS: Median left ventricular ejection fraction (LVEF) was 59% with 27% having LVEF < 55%. Those with normal LVEF and no late gadolinium enhancement (37%) were younger in age (10.5 ± 2.6 vs. 15.0 ± 4.3 years-old, p < 0.001). Native T1 was elevated in at least one slice in 82% of patients. Those with high T2 at any slice (27%) were older (p = 0.005) and had lower LVEF (p = 0.005) compared with subjects with normal T2 (73%). The most common myocardial characterization was fibrosis (43%) followed by isolated high T1 (24%). Of the 13 with high T2, ten were categorized as edema, two as fibrofatty, and one as fat. CONCLUSION: CMR parametric mapping sequences offer insights into Duchenne cardiomyopathy pathophysiology, which should drive development of therapeutic interventions aimed at these targets. Myocardial fibrosis is common in DMD. Patients with elevated T2 were older and had lower LVEF. Though fat infiltration was present, the majority of subjects with elevated T2 met criteria for myocardial edema.

Exogenous nitric oxide delivery protects against cardiopulmonary bypass-associated acute kidney injury: Histologic and serologic evidence from an ovine model.

OBJECTIVE: Several human studies have associated nitric oxide administration via the cardiopulmonary bypass circuit with decreased incidence of cardiopulmonary bypass-associated acute kidney injury, but histopathologic and serologic evidence of nitric oxide efficacy for acute kidney injury attenuation are lacking. METHODS: By using a survival ovine model (72 hours), acute kidney injury was induced by implementing low-flow cardiopulmonary bypass for 2 hours, followed by full-flow cardiopulmonary bypass for 2 hours. The nitric oxide cohort (n = 6) received exogenous nitric oxide through the cardiopulmonary bypass circuit via the oxygenator, and the control group (n = 5) received no nitric oxide. Serial serologic biomarkers and renal histopathology were obtained. RESULTS: Baseline characteristics (age, weight) and intraoperative parameters (cardiopulmonary bypass time, urine output, heart rate, arterial pH, and lactate) were equivalent (P > .10) between groups. Postoperatively, urine output, heart rate, respiratory rate, and peripheral arterial saturation were equivalent (P > .10) between groups. Post-cardiopulmonary bypass creatinine elevations from baseline were significantly greater in the control group versus the nitric oxide group at 16, 24, and 48 hours (all P < .05). Histopathologic evidence of moderate/severe acute kidney injury (epithelial necrosis, tubular slough, cast formation, glomerular edema) occurred in 60% (3/5) of the control group versus 0% (0/6) of the nitric oxide group. Cortical tubular epithelial cilia lengthening (a sensitive sign of cellular injury) was significantly greater in the control group than in the nitric oxide group (P = .012). CONCLUSIONS: In a survival ovine cardiopulmonary bypass model, nitric oxide administered with cardiopulmonary bypass demonstrated serologic and histologic evidence of renal protection from acute kidney injury. These results provide insight into 1 potential mechanism for cardiopulmonary bypass-associated acute kidney injury and supports continued study of nitric oxide via cardiopulmonary bypass circuit for prevention of acute kidney injury.

Vulnerability of the ventricular conduction axis during transcatheter aortic valvar implantation: A translational pathologic study.

The ventricular components of the conduction axis remain vulnerable following transcatheter aortic valvar replacement. We aimed to describe features which may be used accurately by interventionalists to predict the precise location of the conduction axis, hoping better to avoid conduction disturbances. We scanned eight normal adult heart specimens by 3T magnetic resonance, using the images to simulate histological sections in order accurately to place the conduction axis back within the heart. We then used histology, tested in two pediatric hearts, to prepare sections, validated by the magnetic resonance images, to reveal the key relationships between the conduction axis and the aortic root. The axis was shown to have a close relationship to the nadir of the right coronary leaflet, in particular when the aortic root was rotated in counterclockwise fashion. The axis was more vulnerable in the setting of a narrow inferoseptal recess, when the inferior margin of the membranous septum was above the plane of the virtual basal ring, and when minimal myocardium was supporting the right coronary sinus. The features identified in our study are in keeping with the original description provided by Tawara, but at variance with more recent accounts. They suggest that the vulnerability of the axis during transcatheter valvar replacement can potentially be inferred on the basis of knowledge of the position of the aortic root within the ventricular base. If validated by clinical studies, our findings may better permit avoidance of new-onset left bundle branch block following transcatheter aortic valvar replacement.

Corrected T1 Mapping in Children and Young Adults With Autoimmune Liver Disease: Correlation With Histology.

The purpose of this study was to assess relationships between liver-corrected T1 (cT1) values (adjusted for T2* effect, MRI system manufacturer, and field strength) and histologic inflammation and fibrosis in 35 participants (15 women and girls, 20 boys and men; median age, 16.0 years) with autoimmune liver disease. At multivariable analysis, inflammation score (ß = 15.5) and sex (ß = 56.0 [female]) were independent predictors of cT1, and fibrosis score (ß = 32.3) and age (ß = 5.5) were independent predictors of cT1 IQR. Liver T1 may have relevance for assessing liver inflammatory activity and fibrosis stage.

Establishing an Endoscopic Chronic Subglottic Stenosis Rabbit Model.

OBJECTIVES/HYPOTHESIS: To develop a reproducible and consistent chronic subglottic stenosis (SGS) in an endoscopic animal model. STUDY DESIGN: Prospective study. METHODS: We conducted a prospective study using New Zealand white rabbits. Chronic SGS was induced endoscopically by Bugbee electrocautery to 50% to 75% of the subglottic area's circumference, followed by 4-hour endotracheal intubation. The rabbit airways were endoscopically assessed and sized with uncuffed endotracheal tubes (ETTs) before the injury, during follow-up, and at the endpoints. There were four endpoints: 2, 4, 6, and 8 weeks post SGS induction. Animals were humanely euthanized for histopathological examination of the subglottic injury site and microscopic measurement of the cricoid lumen. RESULTS: Twenty-two rabbits reached the endpoints, and 18 rabbits developed chronic SGS. ETT size significantly decreased by 0.5 from preinjury to the endpoint in all groups, P < .001. Control median cricoid lumen measurements were 20.48 mm2 , the median cricoid lumen measurement for the 2 weeks endpoint was 14.3 mm2 , 4 weeks 11.69 mm2 , 6 weeks 16.03 mm2 , and 8 weeks endpoint median was 16.33 mm2 . Histopathological examination showed chronic scar tissue and new cartilage formation at the cricoid level, mainly at the posterior subglottic injury site starting from 4 weeks postinjury. Collagen staining revealed substantial amounts of organized collagen and different collagen orientation starting 4 weeks postinjury lasting until 8 weeks postinjury. CONCLUSION: We developed an animal model to study chronic SGS. This model will be utilized to compare different endoscopic treatment interventions in acute SGS versus chronic SGS and further define the molecular basis of SGS. LEVEL OF EVIDENCE: NA Laryngoscope, 132:1909-1915, 2022.

Antithymocyte globulin induction therapy and myocardial complement deposition in pediatric heart transplantation.

BACKGROUND: Antithymocyte globulin (ATG) consists of polyclonal antibodies directed primarily against human T lymphocytes but may contain antibodies with affinity for other tissues in the transplanted organ, resulting in complement (C4d) deposition. This phenomenon has been demonstrated in endomyocardial biopsies (EMBs) of adult cardiac transplants. We examined the relationship of induction immunosuppression with ATG and C4d deposition in EMB of pediatric cardiac transplants. METHODS: Results of C4d immunohistochemistry were available from all EMB of patients transplanted at our center between June 2012 and April 2018 (n = 48) who received induction immunosuppression with either ATG (n = 20) or basiliximab (n = 28) as the standard of care. RESULTS: C4d deposition in the first year post-heart transplant was more commonly seen among patients who received ATG induction (20% of EMBs in ATG group vs 1% of EMBs in basiliximab group; p < .0001). C4d deposition related to ATG was observed early post-transplant (50% ATG vs 0% basiliximab on first EMB; p < .0001 and 35% ATG vs 0% basiliximab on the second EMB; p = .0012). While this difference waned by the third EMB (5% ATG vs 0% basiliximab; p = .41), positive C4d staining persisted to the sixth EMB in the ATG group only (6%). CONCLUSION: C4d deposition is common on EMB up to 1 year post-pediatric cardiac transplant following ATG induction. This high rate of positive C4d staining in the absence of histologic AMR after ATG induction therapy must be accounted for in making clinical decisions regarding cardiac allograft rejection diagnosis and treatment.

Abnormal Peyer patch development and B-cell gut homing drive IgA deficiency in Kabuki syndrome.

BACKGROUND: Kabuki syndrome (KS) is commonly caused by mutations in the histone-modifying enzyme lysine methyltransferase 2D (KMT2D). Immune dysfunction is frequently observed in individuals with KS, but the role of KMT2D in immune system function has not been identified. OBJECTIVE: We sought to understand the mechanisms driving KS-associated immune deficiency (hypogammaglobulinemia [low IgA], splenomegaly, and diminished immunization responses). METHODS: We performed a comprehensive evaluation of humoral immunity and secondary lymphoid tissues in an established KS (Kmt2d+/ßGeo) mouse model and validated select findings in a patient with KS. RESULTS: Compared with wild-type littermates, Kmt2d+/ßGeo mice demonstrated deficiencies in multiple B-cell lineages and reduced serum IgA and elevated IgM levels across multiple ages. The bone marrow, spleen, and intestine of Kmt2d+/ßGeo mice contained diminished numbers of IgA-secreting cells, while elevated germinal center B cells were found in the mesenteric lymph node and Peyer patches. Kmt2d+/ßGeo mice have decreased size and numbers of Peyer patches, a finding confirmed in human samples. We identified deficiency of Itgb7 RNA and protein expression, a gene encoding an adhesion protein that mediates intestinal homing, and we demonstrated KMT2D-dependent control of ITGB7 expression in a human cell line. CONCLUSIONS: Kmt2d haploinsufficiency has broad deleterious effects on B-cell differentiation, specifically hampering gut lymphocyte homing and IgA+ plasma cell differentiation. Intestinal lymphoid defects caused by ITGB7 deficiency have not previously been recognized in KS, and these results provide new mechanistic insights into the pathogenesis of KS-associated immune deficiency.

Sedative and cardiopulmonary effects of buccally administered detomidine gel and reversal with atipamezole in dogs.

OBJECTIVE To evaluate hemodynamic, respiratory, and sedative effects of buccally administered detomidine gel and reversal with atipamezole in dogs. ANIMALS 8 adult purpose-bred dogs. PROCEDURES Arterial and venous catheters were placed. Baseline heart rate, respiratory rate, cardiac output (determined via lithium dilution with pulse contour analysis), oxygen delivery, systemic vascular resistance, arterial blood gas values, and sedation score were obtained. Detomidine gel (2.0 mg/m2) was administered on the buccal mucosa. Cardiopulmonary data and sedation scores were obtained at predetermined times over 180 minutes. Atipamezole (0.1 mg/kg) was administered IM at 150 minutes. Reversal of sedation was timed and scored. Data were analyzed with an ANOVA. RESULTS Compared with baseline values, heart rate was lower at 45 to 150 minutes, cardiac output and oxygen delivery were lower at 30 to 150 minutes, and systemic vascular resistance was increased at 30 to 150 minutes. There were no significant changes in Paco2, Pao2, or lactate concentration at any time point, compared with baseline values, except for lactate concentration at 180 minutes. All dogs became sedated; maximum sedation was detected 75 minutes after administration of detomidine. Mean ± SD time to recovery after atipamezole administration was 7.55 ± 1.89 minutes; sedation was completely reversed in all dogs. No adverse events were detected. CONCLUSIONS AND CLINICAL RELEVANCE Buccally administered detomidine gel was associated with reliable and reversible sedation in dogs, with hemodynamic effects similar to those induced by other α2-adrenoceptor agonists. Buccally administered detomidine gel could be an alternative to injectable sedatives in healthy dogs.