High-Dimensional Single-Cell Multimodal Landscape of Human Carotid Atherosclerosis

BACKGROUND

Atherosclerotic plaques are complex tissues composed of a heterogeneous mixture of cells. However, our understanding of the comprehensive transcriptional and phenotypic landscape of the cells within these lesions is limited.

METHODS

To characterize the landscape of human carotid atherosclerosis in greater detail, we combined cellular indexing of transcriptomes and epitopes by sequencing and single-cell RNA sequencing to classify all cell types within lesions (n=21; 13 symptomatic) to achieve a comprehensive multimodal understanding of the cellular identities of atherosclerosis and their association with clinical pathophysiology.

RESULTS

We identified 25 cell populations, each with a unique multiomic signature, including macrophages, T cells, NK (natural killer) cells, mast cells, B cells, plasma cells, neutrophils, dendritic cells, endothelial cells, fibroblasts, and smooth muscle cells (SMCs). Among the macrophages, we identified 2 proinflammatory subsets enriched in IL-1B (interleukin-1B) or C1Q expression, 2 TREM2-positive foam cells (1 expressing inflammatory genes), and subpopulations with a proliferative gene signature and SMC-specific gene signature with fibrotic pathways upregulated. Further characterization revealed various subsets of SMCs and fibroblasts, including SMC-derived foam cells. These foamy SMCs were localized in the deep intima of coronary atherosclerotic lesions. Utilizing cellular indexing of transcriptomes and epitopes by sequencing data, we developed a flow cytometry panel, using cell surface proteins CD29, CD142, and CD90, to isolate SMC-derived cells from lesions. Lastly, we observed reduced proportions of efferocytotic macrophages, classically activated endothelial cells, and contractile and modulated SMC-derived cells, while inflammatory SMCs were enriched in plaques of clinically symptomatic versus asymptomatic patients.

CONCLUSIONS

Our multimodal atlas of cell populations within atherosclerosis provides novel insights into the diversity, phenotype, location, isolation, and clinical relevance of the unique cellular composition of human carotid atherosclerosis. These findings facilitate both the mapping of cardiovascular disease susceptibility loci to specific cell types and the identification of novel molecular and cellular therapeutic targets for the treatment of the disease.

ADAMTS7 Promotes Smooth Muscle Cell Foam Cell Expansion in Atherosclerosis

Human genetic studies have repeatedly associated SNPs near the gene ADAMTS7 with atherosclerotic cardiovascular disease. Subsequent investigations in mice demonstrated that ADAMTS7 is proatherogenic, induced in response to vascular injury, and alters smooth muscle cell function. However, the mechanisms governing this function and its relationship to atherosclerosis remain unclear. Here, we report the first conditional Adamts7 transgenic mouse in which the gene can be conditionally overexpressed in smooth muscle cells, mimicking its induction in atherosclerosis. We observed that smooth muscle cell Adamts7 overexpression results in a 3.5-fold increase in peripheral atherosclerosis, coinciding with an expansion of smooth muscle foam cells. RNA sequencing of Adamts7 overexpressed primary smooth muscle cells revealed an upregulation in the expression of lipid uptake genes. Subsequent experiments in primary smooth muscle cells demonstrated that increased Spi1 and Cd36 expression leads to increased smooth muscle cell oxLDL uptake. To uncover ADAMTS7 expression in human disease, we have interrogated the largest scRNA-seq dataset of human carotid atherosclerosis. This analysis discovered that endothelial cells had the highest expression level of ADAMTS7 with lesser expression in smooth muscle cells, fibroblasts, and mast cells. Subsequent conditional knockout studies in smooth muscle cells surprisingly showed no change in atherosclerosis, suggesting redundant expression of this secreted factor in the vessel wall. Finally, mice overexpressing Adamts7 in endothelial cells also exhibit increased atherosclerosis, suggesting that multiple vascular cell types can contribute to ADAMTS7-mediated foam cell expansion. In summary, Adamts7 is expressed by multiple vascular cell types in atherosclerosis, and ADAMTS7 promotes oxLDL uptake in smooth muscle cells, increasing smooth muscle foam cell formation and peripheral atherosclerosis in mice.

Operational changes to the lupus intervention fatigue trial as a result of COVID-19: An update to the study protocol

Background

The coronavirus disease 2019 (COVID-19) global pandemic drastically impacted the health system and the research community. As a result, research institutions and funding agencies recommended a moratorium on conducting in-person research and study enrollment until protocol changes to protect participant safety were approved and implemented. We detail the operational modifications made to the Lupus Intervention Fatigue Trial (LIFT) protocol and summarize how we met the varied challenges created by COVID-19.

Methods

We evaluated study protocols and determined that scheduling, acquiring consent, in-person assessments and intervention baseline visits, patient reported outcomes, and data processing procedures needed modification.

Results

Operational modifications were made to ensure study progress while adhering to COVID-19 restrictions. Major changes included electronic consent, remote baseline visits for those in the intervention, self-report outcome measures at home via emailed weblinks, and telemedicine physician assessment visits. The collection of safety labs presented the largest challenge since this required an in-person visit to a laboratory. The study team elected to delay this up to one month after the physician assessment. All follow-up visits were completed, and no participants withdrew from the study.

Conclusion

LIFT was severely impacted by COVID-19. We provide insight into how our study protocol was modified without compromising the integrity of the primary and secondary outcomes of the study. The modifications utilized by the LIFT study resulted in efficiencies that will be included in a revised protocol and may serve as a useful example for other behavioral interventions to adapt their research studies.

ADAMTS7: a Novel Therapeutic Target in Atherosclerosis

PURPOSE OF REVIEW

Genome-wide association studies have repeatedly linked the metalloproteinase ADAMTS7 to coronary artery disease. Here we aim to highlight recent findings surrounding the human genetics of ADAMTS7, novel mouse models that investigate ADAMTS7 function, and potential substrates of ADAMTS7 cleavage.

RECENT FINDINGS

Recent genome-wide association studies in coronary artery disease have replicated the GWAS signal for ADAMTS7 and shown that the signal holds true even across different ethnic groups. However, the direction of effect in humans remains unclear. A recent novel mouse model revealed that the proatherogenicity of ADAMTS7 is derived from its catalytic functions, while at the translational level, vaccinating mice against ADAMTS7 reduced atherosclerosis. Finally, in vitro proteomics approaches have identified extracellular matrix proteins as candidate substrates that may be causal for the proatherogenicity of ADAMTS7. ADAMTS7 represents an enticing target for therapeutic intervention. The recent studies highlighted here have replicated prior findings, confirming the genetic link between ADAMTS7 and atherosclerosis, while providing further evidence in mice that ADAMTS7 is a targetable proatherogenic enzyme.

High-Dimensional Single-Cell Multimodal Landscape of Human Carotid Atherosclerosis

Background

Atherosclerotic plaques are complex tissues composed of a heterogeneous mixture of cells. However, we have limited understanding of the comprehensive transcriptional and phenotypical landscape of the cells within these lesions.

Methods

To characterize the landscape of human carotid atherosclerosis in greater detail, we combined cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) and single-cell RNA sequencing (scRNA-seq) to classify all cell types within lesions (n=21; 13 symptomatic) to achieve a comprehensive multimodal understanding of the cellular identities of atherosclerosis and their association with clinical pathophysiology.

Results

We identified 25 distinct cell populations each having a unique multi-omic signature, including macrophages, T cells, NK cells, mast cells, B cells, plasma cells, neutrophils, dendritic cells, endothelial cells, fibroblasts, and smooth muscle cells (SMCs). Within the macrophage populations, we identified 2 proinflammatory subsets that were enriched in IL1B or C1Q expression, 2 distinct TREM2 positive foam cell subsets, one of which also expressed inflammatory genes, as well as subpopulations displaying a proliferative gene expression signature and one expressing SMC-specific genes and upregulation of fibrotic pathways. An in-depth characterization uncovered several subsets of SMCs and fibroblasts, including a SMC-derived foam cell. We localized this foamy SMC to the deep intima of coronary atherosclerotic lesions. Using CITE-seq data, we also developed the first flow cytometry panel, using cell surface proteins CD29, CD142, and CD90, to isolate SMC-derived cells from lesions. Last, we found that the proportion of efferocytotic macrophages, classically activated endothelial cells, contractile and modulated SMC-derived cell types were reduced, and inflammatory SMCs were enriched in plaques of clinically symptomatic vs. asymptomatic patients.

Conclusions

Our multimodal atlas of cell populations within atherosclerosis provides novel insights into the diversity, phenotype, location, isolation, and clinical relevance of the unique cellular composition of human carotid atherosclerosis. This facilitates both the mapping of cardiovascular disease susceptibility loci to specific cell types as well as the identification of novel molecular and cellular therapeutic targets for treatment of the disease.

A150 MODERATE AGREEMENT IN ENDOSCOPIC DISEASE SCORING OF PEDIATRIC EOSINOPHILIC ESOPHAGITIS AMONG PEDIATRIC GASTROENTEROLOGISTS IN CANADA

Background

Endoscopy is an important tool in assessing the severity of gastrointestinal diseases including Eosinophilic Esophagitis (EoE). Agreement regarding endoscopy outcomes is important when using tools such as the Endoscopic Reference Score for EoE (EREFS).

Purpose

Our goal was to determine interrater and intrarater agreement of EREFS among Canadian pediatric gastroenterologists.

Method

Survey-based study of interrater and intrarater reliability amongst pediatric gastroenterologists with interest in pediatric EoE. Participants were sourced from the Canadian Pediatric EoE Network. Participants were asked how many years of training they’ve had with endoscopy for pediatric EoE and their comfort in disease scoring for pediatric EoE. Pediatric EoE cases were identified from the pediatric EoE registry at the Stollery Children’s Hospital with an endoscopic video associated with each case. Participants were asked to score each video using the EREFS questionnaire for the proximal, middle and distal segments of the esophagus. 15 endoscopic videos were evaluated, with 3 cases provided each week over a period of 5 weeks. Additional data included ratings of the video quality and endoscopy quality. Of 15 cases, 12 were unique cases, distributed evenly in severity between no active disease to severe disease. 3 cases were repeated to assess intrarater reliability. The maximum grade of the proximal, middle and distal segments of the esophagus for each component endoscopic finding (edema, rings, exudates, furrows, strictures) were used for reliability calculations. Fleiss Kappa was calculated for all EREFS items and for each component endoscopic finding. Cohen’s Kappa was calculated to assess intrarater reliability.

Result(s)

Fifteen participants were recruited for the study. The participants had a median of 12 years (IQR: 7, 19) of clinical experience in endoscopy for pediatric EoE. The majority of participants were “comfortable” (i.e., 4 on 5-point scale) with EREFS scoring for pediatric EoE. Fleiss Kappa for all EREFS items was 0.481. For each component endoscopic finding (edema, rings, exudates, furrows, strictures), Fleiss Kappa was 0.365, 0.293, 0.548, 0.263, 0.445 respectively. Cohen’s Kappa had a median of 0.620 (IQR: 0.593, 0.704). The majority of raters rated video quality and endoscopy quality as “good” (i.e., 4 on 5-point scale).

Conclusion(s)

There is moderate interrater reliability in EREFS scoring for pediatric EoE. Interrater reliability was between fair to moderate for each component endoscopic finding. Intrarater reliability was good. This study shows there is room for improvement in disease scoring for pediatric EoE. This could be in the form of additional training, expert-defined conventions, or centralized reading which have reduced variability in endoscopic reporting for adult GI disease in past studies and could be used in a follow-up study to attempt to improve agreement. Additionally, incorporating EREFS into routine clinical practice may increase agreement amongst endoscopists.

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Disclosure of Interest

None Declared

537 Oro-Nasal Fistula: A Very Rare Complication Following Routine Palatal Biopsy

Biopsies of the palate are generally well-tolerated with known complications of pain, bleeding, or infection, that can usually be well-controlled. We report a case of a 63-year-old male who developed a rare complication following a biopsy of an ulcer on the junction between hard and soft palate. Despite an uneventful routine biopsy, the patient presented with an oro-nasal fistula and complaints of nasal discharge. The cause of the fistula was unclear, and the histopathology results excluded malignancy. The possible hypotheses considered for this very rare and unusual complication were infection, vascularity, and underlying systemic co-morbidities. We believe in this case that the cause of wound breakdown was secondary to loss of vascularity of the mucosa from his CPAP device. The patient has since been referred to a tertiary unit for consideration of surgical repair. To the author's knowledge, there are no similar published reports of such complications following routine palatal biopsy.

Abstract 524: Single-cell Rna Sequencing Of Early Atherosclerosis In Mice Reveals The Early Emergence Of A Dedifferentiated Smooth Muscle Cell Population

Single Cell RNA Sequencing (scRNA-seq) has proven to be a powerful technique to uncover heterogeneity from otherwise homogeneous tissues. Multiple studies have utilized scRNA-seq to examine the composition of atherosclerotic plaques in both humans and mice. However, most of these studies occurred in advanced atherosclerosis. We sought to expand this knowledge base by performing single-cell RNA sequencing at early atherosclerosis in mice. We crossed the Ldlr-/- hyperlipidemic mouse model to a smooth muscle cell (SMC) lineage tracing mouse (ROSA26:LSL-ZsGreen; MyH11-CreERT2). When treated with tamoxifen, SMCs expressing Myh11 are labeled green. At seven weeks of age, we treated these mice with five IP injections of 40mg/kg of tamoxifen. After one week of rest, we initiated the mice on a western diet. We dissected out the whole aorta at the time of harvest and digested the aorta for one hour with a cocktail of DNase, Hyaluronidase, and Liberase. Subsequently, we FACS sorted out both ZsGreen negative and ZsGreen positive cells and performed single-cell RNA seq using the 10x Genomics pipeline. We performed scRNA-seq with pools of three mice at four time points: after 1, 2, 3, and 4 weeks of western diet feeding. Clustering with CarDEC revealed three SMC populations. At four weeks of western diet, we observed an emergence of a SMC cluster characterized by increased expression of Vcam1, Dcn, Mgp, and Egr1. As expected, Gene Ontology analysis of the top 20 differentially expressed genes revealed this population to contain reduced markers of SMC differentiation. In addition, this population had reduced expression of Pura, a protein known to influence serum response factor and regulate smooth muscle actin expression. In summary, our studies indicate changes within SMCs, and the emergence of a dedifferentiated smooth muscle cell population after four weeks of western diet feeding. This study highlights that remodeling of the vasculature occurs even with short durations of hyperlipidemia. Further ongoing studies include expanding time points to longer durations of western diet and elucidating master regulators of this population with Virtual Inference of Protein activity by Enriched Regulon (VIPER).

Abstract 103: Smooth Muscle Cell Specific Overexpression Of Adamts7 Drives Atherosclerosis Development Through The Remodeling Of The Extracellular Matrix

Genome-wide association studies in humans link ADAMTS7 with coronary artery disease. Subsequent studies in mice showed ADAMTS7 to be proatherogenic, as whole-body knockout (KO) reduced atherosclerosis independent of lipid-lowering. Further studies show that Adamts7 expression is temporarily induced in response to vascular injury, and Adamts7 KO reduces primary smooth muscle cell (SMC) migration ex vivo. However, both the mechanism through which ADAMTS7 influences atherosclerosis progression and the responsible cell type remain unclear.

As ADAMTS7 is secreted, we sought to determine its cleavage targets. We generated an immortalized human SMC line with doxycycline-inducible expression of GFP or ADAMTS7. We analyzed conditioned media from these cells via terminal amine isotopic labeling of substrates (TAILS) proteomics. This method labels new protein N termini, enabling the identification of cleavage products. Overexpression of Adamts7 enriched extracellular matrix (ECM) peptides such as Col1a1, Col1a2, Col4a2, and fibronectin. Furthermore, KEGG analysis identified ECM receptor interaction and focal adhesion formation as highly enriched pathways in the dataset. These results suggest ADAMTS7 alters SMCs by modulating signaling between cell and ECM.

To examine the cell type that confers the proatherogenic effects of Adamts7, we generated a conditional transgenic ADAMTS7 mouse on the Ldlr knockout background. Given previously described roles for ADAMTS7 in SMC migration and vascular reendothelialization, we crossed these mice to either the Tie2-Cre or Myh11-CreERT2 to overexpress ADAMTS7 in endothelial and SMCs respectively. We found >3-fold increase (p = 0.0002) in plaque burden by en face staining in overexpression of Adamts7 in SMCs compared to controls. In contrast, transgenic overexpression of Adamts7 in endothelial cells is embryonic or perinatally lethal (Chi-squared = 0.0018).

In summary, our transgenic study affirms the proatherogenic effect of increased Adamts7 expression in SMCs in vivo. Furthermore, our TAILS data suggests a dynamic role of ADAMTS7 in cleaving ECM. These studies fill critical knowledge gaps in our understanding of ADAMTS7 biology and help inform potential therapeutic avenues to targeting this enzyme.

1212 A Systematic Assessment Of Engagement, Functionality, Aesthetics, Information, And Recommendation Features In Sleep Mobile Applications

Introduction

Initial download and use of sleep tracking is very high, but prolonged use is very low. Poor prolonged use may be attributable to several factors such as engagement, functionality, aesthetics, information, and recommendation. We appraised these five factors in 16 consumer- and research/medical- grade digital sleep devices.

Methods

Three reviewers independently assessed 16 consumer- and medical-grade sleep digital devices using the Mobile Application Rating Scale (MARS) App quality ratings, which measures engagement (engagement, entertainment, interest, customization, interactivity, target group), functionality (functionality, performance, ease of use, navigation, gestural design), aesthetics (layout, graphics, visual appeal), information (Accuracy. Goals, Quality of information, Quantity of information, Visual information, Credibility, and Evidence base) and recommended on a Likert scale, with 1- Inadequate to 5 Excellent. Each subcategory is rated on a 1-5 Likert scale which is summed for each category: engagement (30), functionality (25), aesthetics (15), information (35) and recommended (yes or no).

Results

Devices that had the highest engagement score were Fitbit (27), Apple Watch (27), Garmin (27), and Dreem 2 headband (25.5). Apple Watch (30) had highest score; while Fitbit (13), Apple Watch (13), Garmin (13), Samsung Gear (13) had highest aesthetic score. While for information, ActiGraph (35), SOMNOwatch plus (35), CleveMed SleepView Monitor (35), CleveMed Sapphire PSG (35), SOMNOscreen plus (35), Nox T3 Sleep Monitor (35) and Nox A1 PSG System (35) had the highest ratings. The Dreem 2 headband has the potential induce prolong use among users with and without sleep disorders, based on high scores on engagement (25.5), Functionality (20.5), and Information (26.5).

Conclusion

Consumer- and research-grade digital devices that measure sleep have varying levels of engagement, functionality, aesthetics, information and recommendations to facilitate prolong use. Consumer grade devices had higher engagement, functionality and aesthetics scores, while research grade devices had higher information and recommendation scores. If consumer- and research-grade devices are to have prolonged use, standardization is needed across the five MARS components.

Support

K01HL135452, R01MD007716, R01HL142066, and K07AG052685

0995 Nightcap For School-nights: Association Between Milk Intake And Sleep Duration In First-graders

Introduction

Insufficient sleep has been identified as an obesity risk factor due to mechanistic pathways contributing to higher carbohydrate intake, including in children. Dietary intake of macronutrients, such as fats and protein found in milk, may serve as a modifiable risk factor for adequate sleep. We hypothesize that milk intake among a sample of urban first-graders may be associated with sleep duration.

Methods

Cross-sectional analysis of parent reports of an adapted version of the Child Sleep Health Questionnaire (CSHQ) and Block Dietary Data Systems Food Frequency Questionnaire (FFQ) were analyzed among a sample of 837 Black children in Brooklyn, New York. Summary scores were created for milk type. Milk intake was classified by fat content: whole milk and 2% categorized as high-fat, and 1% and skim as low-fat. Independent t-test, correlations and regression analysis to identify associations between parent reports of child’s sleep duration and milk intake were conducted.

Results

On average, children were 7.3 + 0.6 years old and 52% female. Nearly 57% of parents were immigrants. Children’s mean BMI was 17.27, approximately at the 85th BMI percentile according to CDC index-for-age percentiles. On average, FFQ data reported children consumed high-fat milk 6 days a week. Linear variable regression analysis between high-fat milk intake and sufficient sleep were significant (β =, 0.090, p < 0.05). BMI was significantly associated with high-fat milk intake (β= 0.17, p<0.05). However, high-fat milk intake was not significantly associated with (in)sufficient sleep, after controlling for BMI, sex and age. No difference was reported between immigrant parents and U.S. born parents.

Conclusion

Plausibly, high-fat milk is contributing to satiety and longer sleep duration. Future studies should include more comprehensive measurement of milk consumption (i.e. time of day and volume) to consider possible effects on children’s sleep. Actigraphy measures and sleep diaries should also be considered.

Support

Bezos Grant and Community Service Plan grant.

0964 Out Like a Light: Preliminary Results of Parent-Child Dyad Use of an Audio-Based Mobile Application Aiding Bedtime Routine and Sleep Health

Introduction

Adequate sleep is essential for a child’s growth and development. However, a growing number of children are experiencing trouble falling asleep. Smartphone audio-based mobile applications with soothing melodies and calming nighttime stories may improve sleep onset. Our study examined the efficacy of Moshi Twilight, an app designed to improve sleep onset, among children ages 3-8 years old using a parent-child dyadic approach.

Methods

Our within-subjects pre-post study design focused on healthy children studied over 10 days, spanning 3 weeknights and 2 weekend nights. During the baseline (Days 1-5) and exposure (Days 6-10) conditions the Child Sleep Health Questionnaire was used to measure children’s sleep behavior. The PROMIS and Pittsburgh Sleep Quality Index were used to assess parents’ sleep quality. Parents exposed their child to 1 story per night (15-20 minutes) during the exposured condition. Statistical analysis was based on paired t-tests, independent t-tests, and correlations.

Results

On average, participating parents were 37 (SD +9.6) year-old mothers. The sample was: 60% Black; 20% White, 20% other race/ethnicity. On average, children were 4 (SD + 0.78) years old and 50% male. Paired t-tests showed significant differences in children’s sleep onset within 20 minutes (t=2.582, 95% CI 0.116, 2.634, p= 0.036). Significant correlations were noted for children’s bedtime consistency (r = -0.755, p = 0.030), falling asleep in own bed (r = 0.735, p=0.015) and sleep duration (r = -0.715, p=0.046,) Significant correlations and paired t-test in parents’ sleep onset were also found (r = 0.744, p = 0.014); (mean= -1.2, t= -3.674, 95% CI -1.939, -0.461, p=0.005)

Conclusion

Our results showed that the audio-based sleep app, Moshi Twilight, might be useful in improving sleep health among both children and parents. This could be included in enhance bedtime routine among preschool-aged children.

Support

Bezos Grant and Community Service Plan grant.

Cushioned-Density Gradient Ultracentrifugation (C-DGUC) improves the isolation efficiency of extracellular vesicles

Ultracentrifugation (UC) is recognized as a robust approach for the isolation of extracellular vesicles (EVs). However, recent studies have highlighted limitations of UC including low recovery efficiencies and aggregation of EVs that could impact downstream functional analyses. We tested the benefit of using a liquid cushion of iodixanol during UC to address such shortcomings. In this study, we compared the yield and purity of EVs isolated from J774A.1 macrophage conditioned media by conventional UC and cushioned-UC (C-UC). We extended our study to include two other common EV isolation approaches: ultrafiltration (UF) and polyethylene glycol (PEG) sedimentation. After concentrating EVs using these four methods, the concentrates underwent further purification by using OptiPrep density gradient ultracentrifugation (DGUC). Our data show that C-DGUC provides a two-fold improvement in EV recovery over conventional UC-DGUC. We also found that UF-DGUC retained ten-fold more protein while PEG-DGUC achieved similar performance in nanoparticle and protein recovery compared to C-DGUC. Regarding purity as assessed by nanoparticle to protein ratio, our data show that EVs isolated by UC-DGUC achieved the highest purity while C-DGUC and PEG-DGUC led to similarly pure preparations. Collectively, we demonstrate that the use of a high-density iodixanol cushion during the initial concentration step improves the yield of EVs derived from cell culture media compared to conventional UC. This enhanced yield without substantial retention of protein contaminants and without exposure to forces causing aggregation offers new opportunities for the isolation of EVs that can subsequently be used for functional studies.

exRNA Atlas Analysis Reveals Distinct Extracellular RNA Cargo Types and Their Carriers Present across Human Biofluids

To develop a map of cell-cell communication mediated by extracellular RNA (exRNA), the NIH Extracellular RNA Communication Consortium created the exRNA Atlas resource (https://exrna-atlas.org). The Atlas version 4P1 hosts 5,309 exRNA-seq and exRNA qPCR profiles from 19 studies and a suite of analysis and visualization tools. To analyze variation between profiles, we apply computational deconvolution. The analysis leads to a model with six exRNA cargo types (CT1, CT2, CT3A, CT3B, CT3C, CT4), each detectable in multiple biofluids (serum, plasma, CSF, saliva, urine). Five of the cargo types associate with known vesicular and non-vesicular (lipoprotein and ribonucleoprotein) exRNA carriers. To validate utility of this model, we re-analyze an exercise response study by deconvolution to identify physiologically relevant response pathways that were not detected previously. To enable wide application of this model, as part of the exRNA Atlas resource, we provide tools for deconvolution and analysis of user-provided case-control studies.

Abstract P2-09-07: Preoperative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable triple-negative breast cancer (TNBC)

Background: Radiation therapy (RT) induces immune-mediated cell death and could generate a rich supply of tumor antigens if administered in the pre-operative, curative-intent setting. The addition of PD-1 mediated checkpoint blockade to pre-operative RT could thus, generate robust anti-tumor immune responses, induce long-term tumor-specific memory, and ultimately, improve cure rates. This study aims to establish the safety of pre-operative pembrolizumab (pembro)-mediated immune modulation with a RT “boost” equivalent in patients with operable triple negative breast cancer (TNBC) for whom lumpectomy and adjuvant RT are planned (NCT03366844). Serial research biopsies permit interrogation of conventional biomarkers including tumor infiltrating lymphocytes (TILs) and novel immune correlates as potential predictors of response to pembro alone versus pembro with RT.

Methods: Ten women with operable, primary TNBC >2cm for whom breast-conserving therapy is planned are being enrolled in this single-institution pilot study. Study treatment consists of 1 cycle of pre-operative pembro (200 mg IV) alone, followed 3 weeks later by a RT boost (24 Gy/3 fractions) to the primary breast tumor concurrently with pembro (+/- 5 days). Curative-intent, standard-of-care, neoadjuvant chemotherapy (NAC) or breast-conserving surgery is then undertaken within 8 weeks of study enrollment (i.e. within 5 weeks of pembro #2). Adjuvant RT is administered per standard-of-care after surgery, but without a boost dose. Research blood and fresh tumor biopsies are obtained at baseline and after cycles 1 and 2 of pembro. Co-primary endpoints are: 1) safety/tolerability, as defined by the number of patients who do not necessitate a delay in standard-of-care chemotherapy or surgery and 2) change in TIL score. Secondary endpoints include safety/toxicity up to 19 weeks after study enrollment, pCR rates and disease-free survival. Correlative analysis will include single-cell RNA sequencing of the tumor immune infiltrate and multispectral immunohistochemistry

Results: Seven patients enrolled between 12/19/17 and 7/1/18. As of 7/1/18, 5 patients have completed the experimental pembro/RT phase of the trial and are currently completing standard-of-care NAC; 1 patient is currently being treated in the experimental pembro/RT phase; and 1 patient with a cT2N0 tumor at baseline achieved a pathologic complete response (pCR, ypT0/Tis ypN0) after completing the experimental pembro/RT phase followed by anthracycline- and taxane-based NAC. No grade 3 or 4 toxicities have been observed during pembro/RT in the 6 patients completing the experimental phase to date. Three additional patients will be enrolled

Conclusions: This is the first trial of curative-intent, pre-operative checkpoint blockade with RT in breast cancer and the strategy appears to be well tolerated to date. At the time of presentation, safety, change in TIL score, and pCR rates for all patients completing the experimental and NAC phases of the study will be reported.

Citation Format: McArthur HL, Basho R, Shiao SL, Park D, Mita M, Chung A, Arnold B, Martin C, Dang C, Karlan S, Knott S, Giuliano A, Ho A. Preoperative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-07.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Abstract 262: Circulating Exosomes from PAD Patients Modulate Vascular Repair and Inflammation

Objectives: Peripheral arterial disease (PAD) is a chronic disease characterized by inflammation. Recent work suggests that circulating exosomes may contribute to vascular injury and remodeling. We hypothesize that exosomes from PAD subjects negatively modulate vascular repair via miRNA and bioactive lipid mediators (LM).

Methods: Exosomes (particle size 30-100nm) were isolated from plasma of healthy (n=6) and PAD (n=6) subjects. Exosome miRNA was isolated and assessed by qPCR. Targeted metabolo-lipidomics was performed by liquid-chromatography-tandem mass spectrometry. VSMC and EC migration were assessed via scratch assay. Monocyte-derived macrophage gene expression after exposure to exosomes was assessed via RT-qPCR.

Results: Compared to healthy subjects, exosomes from PAD subjects contained lower levels of pro-angiogenic miR-126 and miR-210 (25.2±6.4 vs 8.3±1.7, p<0.05 and 0.29±0.07 vs 0.08±0.02, p<0.05, respectively). Exosomes contained arachidonic acid, eicosapentaenoic acid and docosapentanoic acid, as well as both pro-inflammatory and pro-resolving bioactive LMs and their pathway markers, including prostaglandins, leukotrienes, lipoxins, resolvins (D- and E-series) and maresins. By principle component analysis, exosome LM profiles differed significantly between healthy and PAD subjects. Exosomes from PAD subjects increased VSMC migration (1.5±.09-fold vs 1.0±.09-fold wound closure, p<0.005) and decreased EC migration (1.5±.04-fold vs. 1.8±.06-fold wound closure, p<0.005) compared to healthy controls. Both PAD and healthy exosomes increased MDM expression of pro-inflammatory genes TNF-α and MCP-1.

Conclusion: Plasma-derived exosomes from PAD patients contain an altered profile of vascular-active miRNA and LMs and confer effects on VSMCs and ECs that may impair vessel remodeling. We describe the first known evidence that plasma exosomes contain pro-resolving LMs. Collectively these data suggest that circulating exosome-based signaling may modulate vascular inflammation and repair in PAD patients.

Abstract 408: ApoE Regulation of Hematopoiesis Suppresses Atherosclerosis by Reducing Adaptive Immunity in Hyperlipidemic Mice

Background and Purpose: Apolipoprotein (apo) E suppresses atherosclerosis by exerting a profound control over cells of the innate immune system including monocytes and macrophages. In mice with hyperlipidemia, apoE also prevents an exaggerated proliferation of hematopoietic stem and progenitor cells (HSPC) to further limit the expansion of innate immune cells. However, apoE’s control over hematopoiesis and its subsequent shaping of adaptive immunity remains unexplored.

Methods: We explored this question by studying HypoE mice deficient in the LDL receptor ( Apoe h/h Ldlr –/– mice) that display plasma lipid levels similar to those of Apoe -/- Ldlr -/- mice when fed a chow diet, but accumulate apoE in plasma and display reduced atherosclerosis. Populations of HSPC were examined in the bone marrow (BM) and spleen, while populations of mature immune cells and their levels of cellular activation were examined in the blood, spleen, lymph nodes and aorta of twenty-week-old mice.

Results: Our findings show that apoE suppressed the expansion of HSPC in both the spleen and BM of Apoe h/h Ldlr -/- mice, which remained similar to levels seen in normal wildtype mice. Specifically, in the spleens of Apoe h/h Ldlr -/- mice, apoE reduced the expansion of a population of multi-potent progenitors termed MPP4 responsible for lineages of lymphoid cells. Accordingly, Apoe h/h Ldlr -/- mice displayed smaller spleens and lymph nodes that contained fewer myeloid- and lymphoid-derived leukocytes compared to Apoe -/- Ldlr -/- mice. The spleens and lymph nodes of Apoe h/h Ldlr -/- mice had a higher percentage of T cells that displayed a naïve phenotype, while the percentage of effector T cells was decreased and produced 50% less IFN-γ. Dendritic cells isolated from spleens of Apoe h/h Ldlr -/- mice showed reduced levels of CD86 that plays a key role in T cell activation. Digested aortas of Apoe h/h Ldlr -/- mice revealed a decrease in both T cell and myeloid cell number that also displayed a lower percentage of the pro-inflammatory CD11b + subtype but a higher percentage of the anti-inflammatory CD103 + subtype.

Conclusion: Collectively, our findings show that the control of hematopoiesis exerted by apoE results in reduced adaptive immunity to suppress atherosclerosis in hyperlipidemic mice.

Abstract 184: Hyperglycemia Enhances Pro-inflammatory Properties of Macrophage-derived Exosomes to Drive Hematopoiesis in Apolipoprotein E-deficient Mouse

Background and Purpose: Diabetes is recognized to enhance the frequency and severity of atherosclerosis and cardiovascular disease. Recent studies have shown that hyperglycemia is associated with enhanced hematopoiesis and macrophage accumulation in atherosclerotic lesions. We explored whether high glucose concentrations can enhance intercellular communication between mature macrophages and hematopoietic progenitors via exosomes to promote inflammation and diabetic atherosclerosis.

Methods: Bone marrow derived macrophages (BMDM) from C57BL/6 mice were cultured with normal (5mM) or high glucose concentrations (25mM). Exosomes were isolated with our cushioned-density gradient ultracentrifugation method followed by nanoparticle tracking and western blot analysis. Pro-inflammatory properties of high glucose exosomes (HGexo) were tested in vitro by exposing them to BMDM cultured in normal low glucose. The capacity for BMDM-derived exosomes to alter systemic and vascular inflammation were next tested by infusing 25-30 weeks-old ApoE -/- mice fed a chow diet with 3 x 10 10 exosomes three times a week, for four weeks.

Results: Our data show that HGexo can stimulate the expression of inflammatory cytokines (IL-6, IL-1ß) as well as NADPH oxidases (Nox-1 and Nox-4) in cultured BMDM. Furthermore, our findings show that intraperitoneally injected exosomes distribute to numerous organs and tissues including the bone marrow and the spleen. Lastly, HGexo enhance the expansion of multipotent and lineage committed hematopoietic progenitors.

Conclusions: We identify that exosomes derived from cultured BMDM exposed to high glucose have the capacity to exert intercellular communication in vitro , and in vivo. Our findings suggest that exosomes produced by macrophages exposed to hyperglycemia could represent an unsuspected source of inflammation to accelerate atherosclerosis in diabetes.

Randomised clinical trial: efficacy, safety and dosage of adjunctive allopurinol in azathioprine/mercaptopurine nonresponders (AAA Study)

BACKGROUND

Thiopurine hypermethylation towards 6-methylmercaptopurine (6MMP) instead of 6-thioguanine nucleotides (6TGN) is associated with inefficacy in patients with IBD. Allopurinol reverses such hypermethylation.

AIMS

To prospectively determine efficacy of allopurinol-thiopurine combination and to compare 2 doses of allopurinol.

DESIGN

In a multicentre, double-blind trial, patients with clinically active or steroid-dependent IBD and thiopurine shunting were randomised to 50 or 100 mg/d allopurinol and 25% of their screening thiopurine dose, which was subsequently optimised, aiming for 6TGN of 260-500 pmol/8x10⁸ RBCs. The primary endpoint was steroid-free clinical remission at 24 weeks.

RESULTS

Of 73 patients, 39 (53% [95% CI 42-65]) achieved steroid-free remission, (54% with 50 mg/d and 53% with 100 mg/d). 81% were able to discontinue steroids. Therapeutic 6TGN levels were achieved in both groups. Final thiopurine doses were lower with 100 mg/d allopurinol (P < 0.005). 6MMP: 6TGN ratio decreased from mean 64 to 4 (P < 0.001), being higher with 50 mg/d (6 ± 1.83) than for 100 mg/d ([1 ± 0.16], P = 0.003). Three patients on 50 mg/d failed to sustain low ratios at 24 weeks. Toxicity was minimal; three patients on 50 mg/d allopurinol developed transient leukopenia. Alanine aminotransferase concentrations decreased (P < 0.001) similarly in both arms. Faecal calprotectin levels at study end were lower in patients who achieved the primary endpoint (median 171 [85-541] vs 821[110-5892] ug/g, P = 0.03).

CONCLUSIONS

Low-dose allopurinol-thiopurine combination safely reverses shunting and optimises 6TGN with associated improvement in disease activity. 100 mg/d allopurinol is preferable due to greater metabolite profile stability and lower thiopurine dose without additional toxicity.

Trends in child and adolescent obesity prevalence in economically advanced countries according to socioeconomic position: a systematic review

Recent obesity trends in children and adolescents suggest a plateau. However, it is unclear whether such trends have been experienced across socioeconomic groups. We analysed whether recent trends in child and adolescent overweight and obesity differ by socioeconomic position (SEP) across economically advanced countries. Eligible studies reported overweight and obesity prevalence in children and/or adolescents (2-18 years), for at least two time points since 1990, stratified by SEP. Socioeconomic differences in trends in child and adolescent overweight and obesity over time were analysed. Differences in trends between SEP groups were observed across a majority of studies. Over half the studies indicated increasing prevalence among low SEP children and adolescents compared to a third of studies among children and adolescents with a high SEP. Around half the studies indicated widening socioeconomic inequalities in overweight and obesity. Since 2000 a majority of studies demonstrated no change or a decrease in prevalence among both high and low SEP groups. However around 40% of studies indicated widening of socioeconomic inequalities post-2000. While our study provides grounds for optimism, socioeconomic inequalities in overweight and obesity continue to widen. These findings highlight the need for greater consideration of different population groups when implementing obesity interventions.

Abstract P6-17-05: A corrole nanobiologic crosses the blood-brain-barrier and recognizes triple negative breast cancer: Implications for targeting brain metastases

Patients with breast cancer metastases to the brain on average survive less than one year. These tumors tend to be resistant to current therapies, and the majority of targeted therapeutics are unable to breach the blood brain barrier (BBB) to reach these tumors, thus improved alternatives are urgently needed.

Elevated cell surface levels of the human epidermal growth factor receptor subunit 3 (HER3) is associated with metastatic breast tumors, including those that spread to the brain. Elevated HER3 is also associated with resistance to a number of targeted therapies currently used in the clinic, including inhibitors of EGFR (lapatinib), HER2 (lapatinib, trastuzumab, T-DM1), HER2-3 (pertuzumab), and combination therapy.

Whereas a number of targeted therapies are currently used to combat peripheral breast tumors, the delivery of these molecules to brain metastases is limited by the blood brain barrier (BBB). This is exemplified by HER2+ breast tumors that metastasize to the brain: these tumors, while targetable outside of the central nervous system (CNS) by HER2 antibodies such as trastuzumab, are unreachable by these same antibodies because the HER2 subunit, though present on the brain endothelium, does not mediate antibody transcytosis across the blood vessel wall.

HER3, on the other hand, undergoes rapid transcytosis across the brain endothelium upon ligand binding, which normally occurs to mediate the delivery of neuregulin growth factors for neural growth and maintenance. We have developed a self-assembling nanobiological particle, HerMn, which uses HER3 as a portal for targeted entry of toxic molecules into tumor cells.

HerMn is a 10-20 nm diameter serum-stable particle comprised of a HER3-targeted cell penetration protein non-covalently assembled with a sulfonated manganese(III) corrole (S2Mn or Mn-corrole). Tumor-targeted toxicity by HerMn occurs by mitochondria membrane disruption and superoxide-mediated damage to the cytoskeleton. HerMn can also elicit tumor-selective detection by magnetic resonance imaging (MRI) due to the paramagnetic property of the corrole. HerMn distributes to the brain after systemic injection in mice, in addition to showing preferential homing and toxicity to subcutaneous tumors expressing the HER2-3 dimer. Interestingly, the Mn corrole is known to exhibit neuroprotective effects due to its antioxidant activity on normal tissue. Consistent with this, we have found that HerMn supports human cardiac cell survival ex vivo. Our studies interrogating the therapeutic potential of HerMn suggest that this nanobiologic bears the capacity for targeting toxicity to brain-metastatic breast tumors while sparing off-target tissue due to both its targeting capacity and ability to provide beneficial protective effects to normal tissue such as the brain and heart.

Citation Format: Medina-Kauwe L, Sims J, Taguiam M, Hanson C, Alonso-Valenteen F, Cui X, Wagner S, Sorasaenee K, Moats R, Marban E, Chung A, Gray H, Gross Z, Giuliano A. A corrole nanobiologic crosses the blood-brain-barrier and recognizes triple negative breast cancer: Implications for targeting brain metastases. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-17-05.

Abstract P3-07-37: Quantitative analysis of T cell and macrophage immune markers in Her2-positive breast cancer

Purpose/Objectives:

Her2-neu positive breast cancers have a good overall prognosis with the advent of Her2-directed therapies such as trastuzumab. However, despite the increased efficacy with Her-2-directed therapies 20-30% of patients still have local and/or distant failure despite being Her-2 amplified on pathology. The etiology of this local failure remains unknown. Recent evidence has suggested that there may be immune factors that contribute to the progression of breast cancer and the response to therapy so we undertook a study to examine the relationship between immune-based markers and traditional pathologic and clinical markers of outcome.

Materials/Methods:

Paraffin-embedded sections were generation and clinical records were reviewed for 88 patients, age ≥ 18 years, with pathologically-proven Her2-neu+ breast cancer who were treated at a single institution from 01/2001 to 12/2013. Single-color immunohistochemical staining was performed for CK5/6, CK14 and EGFR and scored by a breast pathologist. Adjacent sections were also then stained for CD45, CD4, CD8 and CD68 using a multi-color immunohistochemical approach. Slides were scanned using the Vectra Automated Quantitative Pathology Imaging System and analyzed using an in-house algorithm to quantitate the number of immune cells within the tumor, tumor margin and within 2 mm outside the tumor. We then compared the level of CK5/6, CK14, EGFR with the number of immune cells. The number of different immune cells were also analyzed with respect to other clinical parameters including age, tumor size, nodal status, hormone receptor status, time to progression, progression-free survival and overall survival.

Results:

At a median follow-up of 66.5 months, 20 (22.7%) patients had progressed. We found that the number of CD45+ leukocytes at the margin correlates with the expression of CK5/6 (p = 0.015) which predicted for local failure. Further, we found that the ratio of CD8 to CD4 cells within the tumor and margin highly correlates with the expression of the hormone receptors (p = 0.01).

Conclusions:

Our preliminary results suggest that immune markers may be important predictors of a basal-like phenotype as defined by CK5/6 expression in Her2+ breast cancers which itself correlated with significantly higher local failure. Further higher CD8 to CD4 ratios were highly correlated with hormone receptor expression, particularly PR expression suggesting that in the Her2+ population the more favorable prognosis for the "triple-positive" subtype of Her2+ cancers may be in part due to a more favorable immune microenvironment.

Citation Format: Shiao SL, Gertych A, Ma Z, Zhang X, Burnison CM, Mirhadi AJ, Giuliano A, Knudsen BS, Chung A. Quantitative analysis of T cell and macrophage immune markers in Her2-positive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-37.

Abstract P6-13-10: Therapeutic efficacy of HER3-targeted nanobiologics on resistant tumors

Elevated cell surface levels of the human epidermal growth factor receptor subunit 3 (HER3) are associated with resistance to a number of signal-blocking breast cancer treatments, including inhibitors of EGF-R (lapatinib), HER2 (lapatinib, trastuzumab, T-DM1), HER2-3 (pertuzumab), and combination therapy. Additionally, HER3 elevation has been identified on "untarget-able" tumors such as triple-negative breast cancer (TNBC), including TNBC with acquired resistance to EGF-R inhibition. Patients with such refractory tumors currently have limited treatment options and a poor prognosis. Moreover, as up to 70% of cases resist or acquire resistance to signal-blocking therapies, an alternative approach addressing this important clinical problem has the potential for significant clinical impact.

We have developed a protein construct, HerPBK10, which self-assembles with a variety of payloads (including nucleic acids, chemotherapy agents, and imaging agents) and uses HER3 as a portal for targeted entry into cells. In contrast to receptor-targeted antibodies and tyrosine kinase inhibitors currently used in the clinic, HerPBK10 circumvents the need to modulate signaling by inducing rapid entry of toxic molecules into tumor cells through receptor-mediated endocytosis and membrane penetration.

We have previously shown that nanobiological particles formed between HerPBK10 and therapeutic payloads can elicit targeted toxicity to HER2+ tumors due to the prevalence of HER2-3 heterodimers on the tumor cell surface, while sparing heart and liver tissue. The particles that form (20-40 nm dia.) exhibit stability in serum and no detectable immunogenicity. Here we show that such particles resolve breast tumor cells with acquired resistance to HER2 and/or EGFR inhibitors in contrast to trastuzumab, pertuzumab, and combination treatment. Additionally, therapeutic efficacy is augmented on resistant over parental tumor cells, due in part to the elevated HER3 expression associated with resistance to these inhibitors. Our studies in preclinical models show that these nanoparticles ablate the growth of tumors with both acquired and pre-existing resistance to trastuzumab. Moreover, we have found that signal-inhibitors currently used in the clinic, such as trastuzumab, effectively augment the efficacy of our nanobiologic on both naïve and inherently-resistant breast tumor cells, in part through induced elevation of HER3. Thus, current targeted molecules such as trastuzumab or lapatinib may act as adjuvants to enhance tumor cell-sensitivity to HerPBK10-particles. Such an approach may address the tumor-heterogeneity associated with resistance, and corner tumors for attack by our particles.

Citation Format: Medina-Kauwe L, Sims J, Taguiam M, Hanson C, Alonso-Valenteen F, Cui X, Chung A, Gray H, Gross Z, Giuliano A. Therapeutic efficacy of HER3-targeted nanobiologics on resistant tumors. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-13-10.