United States

Background
Prior research has shown disparities in lung transplantation rates between racial groups, with Asian patients having lower rates of transplantation from the waitlist compared to Hispanic, Black, and White patients. While studies have delved into the characteristics of patients from other racial groups, little is known about the characteristics of Asian patients on the waitlist. This study aims to reveal key characteristics of Asian patients on the lung transplant waitlist using the UNOS/OPTN database to guide future interventions.

Methods
The UNOS/OPTN database was used to evaluate and compare the demographic and clinical characteristics of patients on the lung transplant waitlist. Transplant data were used from October 1987 until June 2023. Pediatric patients (age &lt;18 years) and patients of ethnicities other than White or Asian were excluded from the study. Descriptive analysis was performed, and data was evaluated for statistical significance using Chi-Square for categorical variables and the Kruskal-Wallis test for non-normal continuous variables. The analysis was conducted using R (Version 4.3.1).


Results
A total of 56,530 White patients and 1375 Asian patients from the UNOS database met the study criteria. Asian patients were less likely than White patients to receive a transplant (64.4% vs 70.5%; p&lt;.001) while also having a higher median Lung Allocation Score of 42.35 [IQR 36.96-54.44] compared to 37.21 [IQR 33.60-44.61] for White patients (p&lt;.001). Waitlist mortality was higher in Asian patients at 10.5% compared to 8.4% for White patients (p=.006). Asian patients were more likely to have a college degree (53.5% vs 27.4%; p&lt;.001) and had lower rates of obesity at time of listing (6.8% vs 14.8%; p&lt;.001) but higher rates of diabetes (26.3% vs 15.8%; p&lt;.001). Primary diagnosis differed between Asian and White patients, with the top three primary diagnoses being Idiopathic Pulmonary Fibrosis (39.5% vs 27.7%), COPD/Emphysema (5.2% vs 26.9%), Cystic Fibrosis (1.2% vs 11.8%) respectively (p&lt;.001). There was no statistical difference in the percentage of Asian patients compared to White patients with private insurance (58.8% vs 56.7%, p=.142).

Conclusion
This study suggests that disparities exist for Asian patients on the waitlist for lung transplant. Despite higher median Lung Allocation Scores, Asians patients are less likely to be transplanted and have increased waitlist mortality compared to White patients. More research is needed on the effect of primary diagnosis and other factors that could cause this disparity.

2023 AMA Research Challenge

Disparities and Characteristics of Asian Patients on the Lung Transplant Waitlist

Background
Prior research has shown disparities in lung transplantation rates between racial groups, with Asian patients having lower rates of transplantation from the waitlist compared to Hispanic, Black, and White patients. While studies have delved into the characteristics of patients from other racial groups, little is known about the characteristics of Asian patients on the waitlist. This study aims to reveal key characteristics of Asian patients on the lung transplant waitlist using the UNOS/OPTN database to guide future interventions.

Methods
The UNOS/OPTN database was used to evaluate and compare the demographic and clinical characteristics of patients on the lung transplant waitlist. Transplant data were used from October 1987 until June 2023. Pediatric patients (age <18 years) and patients of ethnicities other than White or Asian were excluded from the study. Descriptive analysis was performed, and data was evaluated for statistical significance using Chi-Square for categorical variables and the Kruskal-Wallis test for non-normal continuous variables. The analysis was conducted using R (Version 4.3.1).


Results
A total of 56,530 White patients and 1375 Asian patients from the UNOS database met the study criteria. Asian patients were less likely than White patients to receive a transplant (64.4% vs 70.5%; p<.001) while also having a higher median Lung Allocation Score of 42.35 [IQR 36.96-54.44] compared to 37.21 [IQR 33.60-44.61] for White patients (p<.001). Waitlist mortality was higher in Asian patients at 10.5% compared to 8.4% for White patients (p=.006). Asian patients were more likely to have a college degree (53.5% vs 27.4%; p<.001) and had lower rates of obesity at time of listing (6.8% vs 14.8%; p<.001) but higher rates of diabetes (26.3% vs 15.8%; p<.001). Primary diagnosis differed between Asian and White patients, with the top three primary diagnoses being Idiopathic Pulmonary Fibrosis (39.5% vs 27.7%), COPD/Emphysema (5.2% vs 26.9%), Cystic Fibrosis (1.2% vs 11.8%) respectively (p<.001). There was no statistical difference in the percentage of Asian patients compared to White patients with private insurance (58.8% vs 56.7%, p=.142).

Conclusion
This study suggests that disparities exist for Asian patients on the waitlist for lung transplant. Despite higher median Lung Allocation Scores, Asians patients are less likely to be transplanted and have increased waitlist mortality compared to White patients. More research is needed on the effect of primary diagnosis and other factors that could cause this disparity.

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Background 

Heart disease is the leading cause of death of in the US. A key part of decreasing mortality is decreasing major cardiovascular (CVD) risk factors— hypertension (HTN), diabetes (DM), and hypercholesterolemia (HLD)— which often requires regular visits to a healthcare provider. Despite wider access to health insurance with the Affordable Care Act (ACA), healthcare costs continue to significantly impact patient decision-making and engagement. Health insurance has evolved: high-deductible health plans, which can have high out-of-pocket costs, have become more popular. In 2021, costs led half of US adults to skip health/dental care, and almost a third to skip medication doses. The effect of this phenomenon—underinsurance—should be explored.​ 



While there was focus on uninsurance prior to ACA, there is far less literature on underinsurance. An examination of insurance’s impact on disease progression is also absent from the literature. This study explores associations between self-reported health insurance status, chronic health conditions, acute coronary syndrome (ACS) events, and CVD risk factor progression. 



Methods 

This study utilizes 2021 national data from the Center for Disease Control’s Behavioral Risk Factor Surveillance System, a cross-sectional study performed as a telephone survey with 358,899 completed records over the 50 states, DC and Guam. After applying complex sampling weights, Rao-Scott chi-squared tests, 95% confidence intervals, and relative risk ratios were calculated with SAS. 

Results 

Inability to see a doctor due to cost in the past year was associated with insurance type (p < 0.0001), with the Indian Health Service, state sponsored health plans, and Medicaid performing the worst. Perceived underinsurance significantly correlated with increased MI, stroke, and diabetes(p<0.001) but decreased awareness of having HTN, HLD, and angina/CAD(p<0.001). This also correlated with increased CVD events amongst those with known risk factors by 3-5%. 

Conclusion 

The impact that insurance has upon willingness to access care highlights the underperformance of the Indian Health Service, state sponsored health plans, and Medicaid amongst others.​ While patient-perceived underinsurance was associated with worsened outcomes and progression of risk factors, the reduced awareness of HLD or HTN highlights that financially-driven lack of care may stop patients from being aware of risk factors before a serious health event occurs. These findings emphasize the need to advocate for improved insurance coverage as a standard and further research to investigate possible cost-effective improvements for the healthcare system: changes in how physicians and social workers counsel patients, how insurers set benefit designs, and how policy is influenced.

Past the Fine Print: The Impact of Insurance Status on the Relationship Between ACS Risk Factors and Events

Background: Triple negative breast cancer (TNBC) is a highly invasive breast cancer subtype that disproportionately occurs in young Black women and those with Breast Cancer 1 (BRCA1) germline mutations. Although TNBC incidence is highest in Black women, germline BRCA1 mutation prevalence is lower in Black women than in White women. Black communities are exposed to environmental pollutants, including heavy metals, because of historical housing discrimination. Current TNBC disparities may be, in part, explained by increased heavy metal exposure. Cadmium (Cd) is a metalloestrogenic heavy metal and clastogen that causes cancer. DNA double strand breaks (DSBs) contribute to genomic instability that drives cancer development. DSBs are repaired primarily by either homologous recombination (HR) or classical non-homologous end joining (cNHEJ) repair. Loss of HR or cNHEJ leads to increased use of error-prone alternative NHEJ (aNHEJ) which promotes genetic instability that can inactivate tumor suppressor genes or activate oncogenes to drive carcinogenesis. The DNA Damage Response (DDR) is a signaling cascade that coordinates both cell cycle arrest and DSB repair. Several DDR proteins require Zn to function and Cd can displace Zn from Zn coordinating proteins. Based on this evidence, we hypothesized that chronic Cd exposure promotes TNBC initiation by disrupting the DNA Damage Response.
Methods: Immortalized breast epithelial cells (MCF 10A) were exposed to 0 or 2.5 µM Cd for 8 weeks. Neutral COMET assays were performed to detect DSBs and quantified using OpenComet ImageJ software. Immunoblotting was performed for proteins important for HR and cNHEJ signaling, including activated (phosphorylated) and total H2AX, ATM, DNA-PKcs, CHEK2, P53, BRCA1, BRCA2, RB1, and total CDKN1A and MDM2. Data were analyzed using unpaired student’s two-tailed t-test with Welch’s correction (immunoblotting) or Mann Whitney test (COMET assay).
Results: Chronic Cd exposure induced DSB accumulation, reduced BRCA1 phosphorylation and CDKN1A expression, and induced TP53 phosphorylation, TP53 protein levels and RB1 phosphorylation.
Conclusion: The DDR normally signals cell cycle arrest in response to DSBs. Decreased activation of BRCA1 likely contributes to decreased repair and increased accumulation of DSBs. Chronic Cd exposure significantly disrupted the DDR at the cell cycle control level by decreasing CDKN1A expression. CDKN1A normally inhibits CDK-dependent phosphorylation of RB1 and RB1 phosphorylation promotes cell cycle progression despite the increase in DSBs. 





Chronic Cadmium Exposure Suppresses the DNA Damage Response

HuBMAP is a research consortium aiming to develop a framework for mapping the human body at single cell resolution. Through molecular analysis technologies and computational tools, an atlas composed of 3D tissue maps will be created to accelerate our understanding of the function and relationships among cells in accordance with our health. Though operative, it remains challenging for metadata to maintain FAIR standards without enforced, controlled vocabularies and internal linkages to ontologies and metadata standards. To be considered FAIR, metadata must be findable, accessible, interoperable, and reusable. In efforts to create such metadata, we have collaborated with the Center for Enhanced Data Annotation and Retrieval (CEDAR) to develop metadata templates linked to ontologies and standards present in the NCBO Bioportal. This study investigated whether existing HuBMAP metadata can be integrated into CEDAR templates to simplify the workflow of data submission, processing, validation, and publication to optimize the metadata pathway. Using the HuBMAP Sample Data v2b Spreadsheet (an Excel spreadsheet containing data on how the tissue sample was collected, processed, and stored), 3 templates were created in CEDAR: Sample Block, Sample Section, and Sample Suspension. There were various concepts in the sample data spreadsheet that could not found the BioPortal repository. For those concepts, vocabularies were created using Excel, converted into RDF files through SKOS Play, and submitted as new ontologies into BioPortal. With the newly available ontologies, templates were created and published in CEDAR. Our results show that this metadata management framework supports authoring, curation, validation, management, and sharing of HuBMAP metadata. CEDAR technology allows users to guarantee their input metadata are FAIR prior to submission for public release. We hope to expose limitations in our model and issues in the metadata being collected by HuBMAP to identify problems in how the experiment is being described. Upon integrating the submission of all these components into one submission tool and workflow, we aim to significantly simplify the workflow of HuBMAP dataset submission, processing, validation, registration, and publication to optimize the metadata pathway from submission to discovery and allow more datasets to become cross-searchable.

A Computational Approach to Making Data F.A.I.R.

Background: Acinetobacter baumannii is one of the world’s most multi-drug resistant (MDR) pathogens. Traditionally responsible for causing nosocomial pneumonia, bacteremia, and soft tissue infections in critically ill and immunocompromised patients, A. baumannii has evolved to propagate a growing number of atypical infections, including fatal cases of necrotizing fasciitis (NF; i.e., flesh-eating disease), over the past decade. Concerningly, these NF A. baumannii (NFAb) isolates display enhanced virulence and antibiotic resistance uncharacteristic of type strains, resulting in limited efficacy of current therapeutics. As such, understanding of mechanisms by which these strains evade host defenses, environmental stress, and previously effective antibiotics is imperative, yet remains scant. Our lab has obtained two MDR NFAb isolates from a case of NF that led to sepsis and death over 36-hours. The present study sought to elucidate resistance mechanisms of these isolates for the identification of new drug targets to treat MDR A. baumannii infections.

Methods: To determine if NFAb resistance and propagation of infection involves the mechanism of host immune cell entry, NFAb isolates (i.e., NFAb-1 collected pre-mortem from blood and NFAb-2 collected post-mortem from tissue) were co-incubated with human-derived THP-1 macrophages with or without pre-treatment with Cytochalasin D, an inhibitor of phagocytosis. A colistin-protection assay was performed to isolate viable intracellular bacteria, which were quantified by colony forming units (CFUs) after 24 hours. To assess resistance to desiccation, dried NFAb isolates and type strains were resuspended, and surviving cells were quantified by CFUs at 1, 5, and 7 day intervals. Lastly, transformation efficiency was assessed using selective media and fluorescence via flow cytometry, then reported as transformant CFU:total CFU.

Results: Similar to type strains, NFAb isolates were found to primarily enter macrophages via macrophage-mediated phagocytosis; however, both NFAb isolates displayed greater intracellular entry and survival in the host immune cells than type strains. Interestingly, NFAb-1 demonstrated greater resistance to desiccation than NFAb-2 over the course of 7 days. Although previous studies highlighted genomic differences between NFAb-1 and NFAb-2, no differences were observed in transformation efficiency between NFAb isolates and type strains.

Conclusion: Collectively, these results suggest NFAb isolates utilize a variety of resistance strategies to survive, and possess a profound ability to rapidly adapt, even within the context of a single infection. Moving forward, we aim to identify the genes propagating the intracellular survival and infection demonstrated by these isolates to serve as potential targets for novel therapeutics.

Utilizing Atypical Isolates of Acinetobacter baumannii to Uncover Novel Mechanisms of Resistance

Background
The COVID-19 pandemic resulted in over 6.8 million deaths worldwide. Although the WHO recently declared an end to the COVID-19 global health emergency, the long-term health impacts from SARS-CoV-2 infection remain unknown. Notably, patients with cardiovascular disease are at increased risk for severe illness and mortality with COVID-19. We sought to understand the inflammatory mechanisms associated with cardiovascular disease that drive severity of COVID-19. To model inflammation in the context of COVID-19, we generated a novel, “humanized” ACE2 (hACE2) mouse that is susceptible to SARS-CoV-2 infection.

Methods
Using CRISPR-Cas9 technology, we inserted the human ACE2 cDNA sequence into the native mouse ACE2 locus, under regulation of the native promoter. Using a combination of RT-qPCR, ELISA, and histology, we validated hACE2 expression in the new strain. Mice underwent intranasal inoculation with SARS-CoV-2 and infection patterns were compared to wild-type mice and the previously characterized K18-hACE2 overexpression model of severe infection. Cultured bone marrow-derived macrophages were subjected to inflammatory stimulation and the dynamic expression of ACE2 expression was assessed for dependence on the NF-kB transcriptional cofactor, Rac1, and the NF-kB-dependent inflammatory cytokine, IL-1β. Chromatin immunoprecipitation (ChIP) was carried out using NF-kB to confirm binding to the ACE2 promoter.

Results
hACE2 mice express human ACE2 mRNA and protein under regulation of the native mouse promoter. Unlike the K18-hACE2, hACE2 mice survived infection with SARS-CoV-2 and maintained stable body weights. Histopathology from the hACE2 mice revealed inflammatory infiltrate and pulmonary consolidation with alveolar hemorrhage, comparable to the K18-hACE2 mice, and immunohistochemistry confirmed presence of viral nucleocapsid in lung consolidations. Infected hACE2 mice demonstrated a unique plasma cytokine profile relative to K18-hACE2 mice, including elevated levels of IL-1β, IL-1α, and VEGF-A, but decreased IL-6 and TNF-α. Bone marrow-derived macrophages revealed increased ACE2 expression in the context of “M1” inflammatory stimulation, and ACE2 expression was dependent on both Rac1 and IL-1β ChIP confirmed NF-kB binding to the ACE2 promoter region. 

Conclusion
We have established a novel model of COVID-19 that survives infection and may facilitate mechanistic studies aimed at understanding the role of inflammation in severity of infection. Macrophages express ACE2 in a dynamic manner and may play a role as a reservoir for ongoing infection during inflammation. Defining Rac1-NF-kB-IL-1β signaling mechanisms driving severity of SARS-CoV-2 infection may identify new targets for inhibiting viral uptake and replication in cells, leading to new therapeutic treatments for patients with COVID-19.


Validation of a Novel Humanized ACE2 Mouse Model of COVID-19

To mount a robust immune response, naïve T cells must differentiate into cytokine producing effector T cells. However, if T cell activation and differentiation is poorly controlled, excess inflammation can occur, resulting in allergy or autoimmune disease. Thus, protective immunity is dependent on a fine tuning of differentiation and cytokine production by T cells. This can be accomplished by E3 Ubiquitin Ligases, as these enzymes regulate the levels of cellular proteins. We performed a screen to identify Cullin E3 ubiquitin ligases that were active in T cells and identified Cullin 5 (Cul 5) as being the most dynamically activated Cullin during T cell activation. While it is known that Cul 5 aids in the formation of the CRL5 complex (for Cullin Ring Ligase), whether and how Cul 5 regulates immune system function is unknown. We have now generated mice that lack Cul 5 in T cells. Initial characterization of these Cul 5 fl/fl CD4-Cre mice revealed that Cul 5 is critical in preventing spontaneous and allergen-induced inflammation in the lungs by inhibiting Th2 differentiation in CD4 T cells. To see if this protective effect of Cullin 5 was important at other mucosal surfaces, we employed a colitis model, known as DSS-induced colitis to experimentally mimic Inflammatory Bowel Disease (IBD). We found that mice that lack Cul5 in T cells showed significantly more weight loss and colon pathology than their wild type counterparts. Surprisingly, the mice did not show increased cytokine production by CD4 T cells, rather, they showed high numbers of CD8+ T cells, that while activated, were less likely to produce IFN-γ. Taken together, our preliminary data support that Cullin 5 may regulate CD8 T cells responses either by limiting cytotoxic activity or by promoting IFN-γ production to facilitate macrophage bactericidal activity. Our data support that Cul 5 prevents colitis by regulating CD8 T cell numbers and/or function.

Cullin 5 Limits Disease Severity in DSS-Colitis

Pseudomonas aeruginosa (PA) is a gram-negative pathogen that causes bacteremia and septicemia in severely burned patients; a situation that often leads to multiorgan failure and death. Despite our extensive knowledge of PA wound infection, there are several gaps in our understanding of the PA response to the blood environment. We recently showed that upon its growth in human blood or human serum (HS), PA strain PAO1 alters the expression of more than 1,000 genes. Many of these alterations may occur through the PA-outer membrane proteins (PA-OMPs). OMPs contribute significantly to the pathogenesis of gram-negative pathogens. We hypothesized that HS alters the production of PA-OMPs. To test this, we grew PAO1, which causes sepsis and death in the murine model of thermal injury, in Luria-Bertani broth (LBB) or LBB containing 10% HS, extracted the OMPs, and analyzed their profile using SDS-polyacrylamide gel electrophoresis. Analysis of the silver-stained gels revealed that 10% HS repressed the production of at least six OMPs with molecular weights (MW) of 68.2, 34.5, 23.8, 17.9, 13.7, and 11.9 kDa but induced the production of at least five others (MW 66.1, 41, 28.5, 22.8, and 22 kDa). Similar to PA-PAOI1, PA-PA14 causes sepsis and death. However, its genome is larger than that of PAO1 and it carries several additional virulence genes. Therefore, we also compared the OMP profile of PAO1 and PA14. Although the two strains share multiple common proteins, each strain has its own unique ones. As with PAO1, HS manipulated the production of several PA14 OMPs. These results suggest that 1) in response to different components of HS, PA varies the production of its OMPs, 2) virulent PA strains differ in their OMPs, and 3) HS-induced OMPs may be targeted in future investigations designed to produce potential serum therapies for PA infected/severely burned patients. 


Human serum alters the production of several Pseudomonas aeruginosa outer membrane proteins.

Background:
Annually, over 300 million patients undergo surgery requiring the administration of a combination of anesthetic pharmacologic compounds (APCs). Surgery is associated with significant tissue trauma, triggering a complex inflammatory response that engages the innate and adaptive branches of the immune system. Complications, including end-organ damage, infections, and protracted recovery, arise as pro-inflammatory and immune-suppressive responses tilt out of balance. Accumulating evidence suggests that, in addition to desired anesthetic properties, many APCs have immune-modulatory properties that can positively or negatively impact surgical recovery. However, the effect of APCs on specific innate and
adaptive immune cell functions warrants further exploration to personalize anesthetic choice based on individual patient and surgery needs. We hypothesize that APCs alter critical immune cell responses and effector functions implicated in the human immune response to trauma and injury.

Methods:
We developed a high-throughput multiplex mass-tag barcoding (MCB) assay to screen 16 commonly administered APCs for their capacity to modulate trauma-related immune and adaptive immune responses. These include general and local anesthetics, narcotic and benzodiazepine analgesics, neuromuscular blocking agents, and NSAIDs. We also selected ten additional compounds frequently used in anesthesia settings: antiemetics, diuretics, antidotes, catecholamines, and beta blockers. Using single-cell mass cytometry, we quantify the effect of each APC on 1500 intracellular signaling responses in 25 innate and adaptive immune cell subsets in whole blood samples (500µL) across a range of drug concentrations and stimulation conditions, including lipopolysaccharide (LPS), interferon alpha (IFNa), and a cocktail of interleukins 2, 4, and 6.

Results:
A first MCB screen was completed using flunisolide, a glucocorticoid compound with a known immunosuppressive effect, allowing for assay optimization. This identified marked changes in protein phosphorylation of inflammatory pathways between immune cells exposed and not exposed to flunisolide. These results show that flunisolide inhibited adaptive immune cell subsets to a greater extent than innate immune cell subsets in a cell-type and signaling response-specific manner.

Conclusion:
Having established the MCB experimental framework, the next experiments will systematically evaluate the immune-modulatory properties of the proposed library of APCs. Eventually, the MCB assay could be utilized clinically to determine the immune-modulatory effect of a complex anesthesia regimen – a first step toward personalized anesthesia.

A High-Throughput Mass Cytometry Assay to Investigate Immune Cell Modulation of Anesthetic Drugs

Background: Pulmonary hypertension (PH) is a fatal disease associated with pulmonary vascular remodeling that leads to right ventricular (RV) failure and death. While miR-10b-5p exerts pro-proliferative effects in various cancers via inhibition of its targets cell adhesion molecule 1 (CADM1) and apoptotic peptidase activating factor 1 (APAF1), its role in PH is elusive. We hypothesize that PH is associated with upregulation of lung miR10b-5p and downregulation of its targets CADM1 and APAF1. Further, miR10b-5p inhibition may rescue pre-existing PH.

Methods: PH was induced in male rats by monocrotaline (MCT; 60mg/kg sc; n=4; followed for 30-days) or Sugen/Hypoxia (SuHx; SU5416; 20mg/kg sc and 10% O2 hypoxia for 3-wks followed by normoxia for 2-wks; n=3). In vivo inhibition of miR10b-5p was performed from day14-30 after MCT (5 intratracheal injections of antagomir every 3-4 days; 5nM/ injection; n=3). PBS treated MCT rats served as controls (n=5). Rats were followed by echo. RV catheterization was performed terminally, and RV hypertrophy index was calculated. MiRNA microarray was performed to assess miR10b in rat lungs. Lungs were stained to quantify vascular remodeling. RT-PCR was performed to assess gene expression. Human pulmonary artery smooth muscle cells (HPASMCs) were incubated with miR10b mimic for 24h to assess proliferation. Data are mean±SEM. 

Results: MCT and SuHx rats developed severe PH. MiRNA microarray revealed a 3-fold increase in miR10b in MCT rat lungs. PCR validated increased miR10b in MCT and SuHx rat lungs. Further, there was a significant downregulation of miR10b targets CADM1 (MCT 1.64-fold; SuHx 1.48-fold) and APAF1 (MCT 1.23-fold; SuHx 1.21-fold) in lungs. In vivo knockdown of miR10b resulted in rescue of PH in MCT rats (RVSP: 50.7±4.42 in antagomir vs. 95.81±3.70 mmHg in placebo; p<0.005; RV hypertrophy index: 0.52±0.02 in antagomir vs. 0.80±0.07; p<0.05; RVID: diastolic 2.44±0.68 in antagomir vs. 4.55±0.42 mm; p<0.05). PCR demonstrated 30% decrease in lung miR10b and histology revealed reduced pulmonary arteriolar medial wall thickness (32.72±1.12 in antagomir vs. 42.24±3.26% in placebo, p<0.005) in rats treated with antagomir. Finally, miR10b overexpression resulted in HPASMC proliferation in a dose-dependent manner.

Conclusion: Pre-clinical PH is associated with an increase in miR10b-5p expression and decrease in its targets CADM1 and APAF1. miR10b-5p inhibition rescues experimental PH and may serve as a novel therapeutic target.

MicroRNA10b-5p Inhibition as a Novel Therapeutic Strategy for Severe Pulmonary Hypertension

Background
Ventricular arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF) are dangerous heart rhythms given their potential to lead to sudden cardiac death. Ventricular arrhythmias are most often associated with ischemic heart disease, but may also arise from heart failure or ion channel abnormalities. Why some hearts affected with such risk factors develop VT or VF while others do not is an open question. Many risk factors for arrhythmia such as ischemia, heart failure, hypertension, diabetes, and aging are associated with increased reactive oxygen species (ROS). Mitochondria are tightly intertwined with the regulation of ROS, and are a prominent organelle in the energy-intensive myocardium. In a mouse model of atrial fibrillation (AF), mitochondria in the atria show swelling, reduced cristae density, and increased mitochondrial degradation known as mitophagy when compared to controls. Reducing ROS and mitophagy leads to a 50-fold reduction in AF burden. Herein, we evaluated whether ventricular arrhythmias are associated with mitochondrial changes in the ventricle. 

Methods
The lab has established transgenic mice expressing a F1795A mutation in the human cardiac Nav1.5 channel gene SCN5A, leading to persistent Na+ current, and demonstrated spontaneous VT and VF in these mice. Wild-type (n=2) and double transgenic (dTG) mice (n=4) expressing human F1759A-Nav1.5 channels as well as reverse tet-transactivator protein had their ventricles sectioned and underwent transmission electron microscopy. Images acquired at 15000x and 50000x magnification were quantified using ImageJ. 

Results
Mitochondria in transgenic F1759A mice ventricles were of significantly smaller area than mitochondria of control mice (345080  4982 nm2 vs. 409409  9516 nm2, p<0.0001) (n=2191, 801 mitochondria respectively). Ventricles of transgenic mice also show greater number of mitochondria per field when compared to controls (73.03  2.884 vs. 58.46  4.32, p=0.008) (n=13, 30 fields). Furthermore, imaging revealed a population of mitochondria with membrane disruption and absence of cristae consistent with mitophagy. The percentage of mitochondria undergoing mitophagy was significantly increased in F1759A mice compared to controls (11.80%  2.256 vs. 0.33%  0.33, p=0.0019).

Conclusion
Transmission electron microscopy of the ventricles of F1759A mice with spontaneous ventricular arrhythmias reveals smaller and increased number of mitochondria undergoing mitophagy. These results suggest mitochondria may be involved in the pathogenesis of VT and VF. Further work will be needed to determine if mitochondrial changes are upstream of ventricular arrhythmogenesis and whether targeting mitochondrial quality can prevent arrhythmias.

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