Ribosome Collisions Trigger General Stress Responses to Regulate Cell Fate.

Problems arising during translation of mRNAs lead to ribosome stalling and collisions that trigger a series of quality control events. However, the global cellular response to ribosome collisions has not been explored. Here, we uncover a function for ribosome collisions in signal transduction. Using translation elongation inhibitors and general cellular stress conditions, including amino acid starvation and UV irradiation, we show that ribosome collisions activate the stress-activated protein kinase (SAPK) and GCN2-mediated stress response pathways. We show that the MAPKKK ZAK functions as the sentinel for ribosome collisions and is required for immediate early activation of both SAPK (p38/JNK) and GCN2 signaling pathways. Selective ribosome profiling and biochemistry demonstrate that although ZAK generally associates with elongating ribosomes on polysomal mRNAs, it specifically auto-phosphorylates on the minimal unit of colliding ribosomes, the disome. Together, these results provide molecular insights into how perturbation of translational homeostasis regulates cell fate.

A Zpr1 co-chaperone mediates folding of eukaryotic translation elongation factor 1A via a GTPase cycle.

General protein folding is mediated by chaperones that utilize ATP hydrolysis to regulate client binding and release. Zinc-finger protein 1 (Zpr1) is an essential ATP-independent chaperone dedicated to the biogenesis of eukaryotic translation elongation factor 1A (eEF1A), a highly abundant GTP-binding protein. How Zpr1-mediated folding is regulated to ensure rapid Zpr1 recycling remains an unanswered question. Here, we use yeast genetics and microscopy analysis, biochemical reconstitution, and structural modeling to reveal that folding of eEF1A by Zpr1 requires GTP hydrolysis. Furthermore, we identify the highly conserved altered inheritance of mitochondria 29 (Aim29) protein as a Zpr1 co-chaperone that recognizes eEF1A in the GTP-bound, pre-hydrolysis conformation. This interaction dampens Zpr1⋅eEF1A GTPase activity and facilitates client exit from the folding cycle. Our work reveals that a bespoke ATP-independent chaperone system has mechanistic similarity to ATPase chaperones but unexpectedly relies on client GTP hydrolysis to regulate the chaperone-client interaction.

Zinc-finger protein Zpr1 is a bespoke chaperone essential for eEF1A biogenesis.

The conserved regulon of heat shock factor 1 in budding yeast contains chaperones for general protein folding as well as zinc-finger protein Zpr1, whose essential role in archaea and eukaryotes remains unknown. Here, we show that Zpr1 depletion causes acute proteotoxicity driven by biosynthesis of misfolded eukaryotic translation elongation factor 1A (eEF1A). Prolonged Zpr1 depletion leads to eEF1A insufficiency, thereby inducing the integrated stress response and inhibiting protein synthesis. Strikingly, we show by using two distinct biochemical reconstitution approaches that Zpr1 enables eEF1A to achieve a conformational state resistant to protease digestion. Lastly, we use a ColabFold model of the Zpr1-eEF1A complex to reveal a folding mechanism mediated by the Zpr1's zinc-finger and alpha-helical hairpin structures. Our work uncovers the long-sought-after function of Zpr1 as a bespoke chaperone tailored to the biogenesis of one of the most abundant proteins in the cell.

High-Resolution Ribosome Profiling Defines Discrete Ribosome Elongation States and Translational Regulation during Cellular Stress.

Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to differently sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show, using various genetic and environmental perturbations, that short 20-22 or classical 27-29 nucleotide RPFs correspond to ribosomes with open or occupied ribosomal A sites, respectively. These distinct states of translation elongation are readily discerned by ribosome profiling in all eukaryotes we tested, including fungi, worms, and mammals. This high-resolution ribosome profiling approach reveals mechanisms of translation-elongation arrest during distinct stress conditions. Hyperosmotic stress inhibits translocation through Rck2-dependent eEF2 phosphorylation, whereas oxidative stress traps ribosomes in a pre-translocation state, independent of Rck2-driven eEF2 phosphorylation. These results provide insights and approaches for defining the molecular events that impact translation elongation throughout biology.

Venous and arterial thrombosis in patients with VEXAS syndrome.

ABSTRACT: VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, caused by somatic mutations in UBA1, is an autoinflammatory disorder with diverse systemic manifestations. Thrombosis is a prominent clinical feature of VEXAS syndrome. The risk factors and frequency of thrombosis in VEXAS syndrome are not well described, due to the disease's recent discovery and the paucity of large databases. We evaluated 119 patients with VEXAS syndrome for venous and arterial thrombosis and correlated their presence with clinical outcomes and survival. Thrombosis occurred in 49% of patients, mostly venous thromboembolism (VTE; 41%). Almost two-thirds of VTEs were unprovoked, 41% were recurrent, and 20% occurred despite anticoagulation. The cumulative incidence of VTE was 17% at 1 year from symptom onset and 40% by 5 years. Cardiac and pulmonary inflammatory manifestations were associated with time to VTE. M41L was positively associated specifically with pulmonary embolism by univariate (odds ratio [OR]: 4.58, confidence interval [CI] 1.28-16.21, P = .02) and multivariate (OR: 16.94, CI 1.99-144.3, P = .01) logistic regression. The cumulative incidence of arterial thrombosis was 6% at 1 year and 11% at 5 years. The overall survival of the entire patient cohort at median follow-up time of 4.8 years was 88%, and there was no difference in survival between patients with or without thrombosis (P = .8). Patients with VEXAS syndrome are at high risk of VTE; thromboprophylaxis should administered be in high-risk settings unless strongly contraindicated.

Yeast translation elongation factor eEF3 promotes late stages of tRNA translocation.

In addition to the conserved translation elongation factors eEF1A and eEF2, fungi require a third essential elongation factor, eEF3. While eEF3 has been implicated in tRNA binding and release at the ribosomal A and E sites, its exact mechanism of action is unclear. Here, we show that eEF3 acts at the mRNA-tRNA translocation step by promoting the dissociation of the tRNA from the E site, but independent of aminoacyl-tRNA recruitment to the A site. Depletion of eEF3 in vivo leads to a general slowdown in translation elongation due to accumulation of ribosomes with an occupied A site. Cryo-EM analysis of native eEF3-ribosome complexes shows that eEF3 facilitates late steps of translocation by favoring non-rotated ribosomal states, as well as by opening the L1 stalk to release the E-site tRNA. Additionally, our analysis provides structural insights into novel translation elongation states, enabling presentation of a revised yeast translation elongation cycle.

Differential diagnosis of bone marrow failure syndromes guided by machine learning.

The choice to postpone treatment while awaiting genetic testing can result in significant delay in definitive therapies in patients with severe pancytopenia. Conversely, the misdiagnosis of inherited bone marrow failure (BMF) can expose patients to ineffectual and expensive therapies, toxic transplant conditioning regimens, and inappropriate use of an affected family member as a stem cell donor. To predict the likelihood of patients having acquired or inherited BMF, we developed a 2-step data-driven machine-learning model using 25 clinical and laboratory variables typically recorded at the initial clinical encounter. For model development, patients were labeled as having acquired or inherited BMF depending on their genomic data. Data sets were unbiasedly clustered, and an ensemble model was trained with cases from the largest cluster of a training cohort (n = 359) and validated with an independent cohort (n = 127). Cluster A, the largest group, was mostly immune or inherited aplastic anemia, whereas cluster B comprised underrepresented BMF phenotypes and was not included in the next step of data modeling because of a small sample size. The ensemble cluster A-specific model was accurate (89%) to predict BMF etiology, correctly predicting inherited and likely immune BMF in 79% and 92% of cases, respectively. Our model represents a practical guide for BMF diagnosis and highlights the importance of clinical and laboratory variables in the initial evaluation, particularly telomere length. Our tool can be potentially used by general hematologists and health care providers not specialized in BMF, and in under-resourced centers, to prioritize patients for genetic testing or for expeditious treatment.

Spectrum of clonal hematopoiesis in VEXAS syndrome.

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome is caused by somatic mutations in UBA1 (UBA1mut) and characterized by heterogenous systemic autoinflammation and progressive hematologic manifestations, meeting criteria for myelodysplastic syndrome (MDS) and plasma cell dyscrasias. The landscape of myeloid-related gene mutations leading to typical clonal hematopoiesis (CH) in these patients is unknown. Retrospectively, we screened 80 patients with VEXAS for CH in their peripheral blood (PB) and correlated the findings with clinical outcomes in 77 of them. UBA1mut were most common at hot spot p.M41 (median variant allele frequency [VAF] = 75%). Typical CH mutations cooccurred with UBA1mut in 60% of patients, mostly in DNMT3A and TET2, and were not associated with inflammatory or hematologic manifestations. In prospective single-cell proteogenomic sequencing (scDNA), UBA1mut was the dominant clone, present mostly in branched clonal trajectories. Based on integrated bulk and scDNA analyses, clonality in VEXAS followed 2 major patterns: with either typical CH preceding UBA1mut selection in a clone (pattern 1) or occurring as an UBA1mut subclone or in independent clones (pattern 2). VAF in the PB differed markedly between DNMT3A and TET2 clones (median VAF of 25% vs 1%). DNMT3A and TET2 clones associated with hierarchies representing patterns 1 and 2, respectively. Overall survival for all patients was 60% at 10 years. Transfusion-dependent anemia, moderate thrombocytopenia, and typical CH mutations, each correlated with poor outcome. In VEXAS, UBA1mut cells are the primary cause of systemic inflammation and marrow failure, being a new molecularly defined somatic entity associated with MDS. VEXAS-associated MDS is distinct from classical MDS in its presentation and clinical course.

Imaging Early Life Cardiovascular Phenotype.

The growing epidemics of obesity, hypertension, and diabetes, in addition to worsening environmental factors such as air pollution, water scarcity, and climate change, have fueled the continuously increasing prevalence of cardiovascular diseases (CVDs). This has caused a markedly increasing burden of CVDs that includes mortality and morbidity worldwide. Identification of subclinical CVD before overt symptoms can lead to earlier deployment of preventative pharmacological and nonpharmacologic strategies. In this regard, noninvasive imaging techniques play a significant role in identifying early CVD phenotypes. An armamentarium of imaging techniques including vascular ultrasound, echocardiography, magnetic resonance imaging, computed tomography, noninvasive computed tomography angiography, positron emission tomography, and nuclear imaging, with intrinsic strengths and limitations can be utilized to delineate incipient CVD for both clinical and research purposes. In this article, we review the various imaging modalities used for the evaluation, characterization, and quantification of early subclinical cardiovascular diseases.

eIF5A Functions Globally in Translation Elongation and Termination.

The eukaryotic translation factor eIF5A, originally identified as an initiation factor, was later shown to promote translation elongation of iterated proline sequences. Using a combination of ribosome profiling and in vitro biochemistry, we report a much broader role for eIF5A in elongation and uncover a critical function for eIF5A in termination. Ribosome profiling of an eIF5A-depleted strain reveals a global elongation defect, with abundant ribosomes stalling at many sequences, not limited to proline stretches. Our data also show ribosome accumulation at stop codons and in the 3' UTR, suggesting a global defect in termination in the absence of eIF5A. Using an in vitro reconstituted translation system, we find that eIF5A strongly promotes the translation of the stalling sequences identified by profiling and increases the rate of peptidyl-tRNA hydrolysis more than 17-fold. We conclude that eIF5A functions broadly in elongation and termination, rationalizing its high cellular abundance and essential nature.

Molecular mechanism of translational stalling by inhibitory codon combinations and poly(A) tracts.

Inhibitory codon pairs and poly(A) tracts within the translated mRNA cause ribosome stalling and reduce protein output. The molecular mechanisms that drive these stalling events, however, are still unknown. Here, we use a combination of in vitro biochemistry, ribosome profiling, and cryo-EM to define molecular mechanisms that lead to these ribosome stalls. First, we use an in vitro reconstituted yeast translation system to demonstrate that inhibitory codon pairs slow elongation rates which are partially rescued by increased tRNA concentration or by an artificial tRNA not dependent on wobble base-pairing. Ribosome profiling data extend these observations by revealing that paused ribosomes with empty A sites are enriched on these sequences. Cryo-EM structures of stalled ribosomes provide a structural explanation for the observed effects by showing decoding-incompatible conformations of mRNA in the A sites of all studied stall- and collision-inducing sequences. Interestingly, in the case of poly(A) tracts, the inhibitory conformation of the mRNA in the A site involves a nucleotide stacking array. Together, these data demonstrate a novel mRNA-induced mechanisms of translational stalling in eukaryotic ribosomes.

Treatment of refractory/relapsed Diamond-Blackfan anaemia with eltrombopag.

Diamond-Blackfan anaemia (DBA) is a rare, inherited bone marrow failure syndrome with a ribosomal defect causing slowed globin chain production with normal haem synthesis, causing an overabundance of reactive iron/haem and erythroid-specific cellular toxicity. Eltrombopag, a non-peptide thrombopoietin receptor agonist, is a potent intracellular iron chelator and induced a robust durable response in an RPS19-mutated DBA patient on another trial. We hypothesized eltrombopag would improve RBC production in DBA patients. We conducted a single-centre, single-arm pilot study (NCT04269889) assessing safety and erythroid response of 6 months of daily, fixed-dose eltrombopag for DBA patients. Fifteen transfusion-dependent (every 3-5 weeks) patients (median age 18 [range 2-56]) were treated. One responder had sustained haemoglobin improvement and >50% reduction in RBC transfusion frequency. Of note, 7/15 (41%) patients required dose reductions or sustained discontinuation of eltrombopag due to asymptomatic thrombocytosis. Despite the low response rate, eltrombopag has now improved erythropoiesis in several patients with DBA with a favourable safety profile. Dosing restrictions due to thrombocytosis may cause insufficient iron chelation to decrease haem production and improve anaemia in most patients. Future work will focus on erythropoiesis dynamics in patients and use of haem synthesis inhibitors without an impact on other haematopoietic lineages.

Safety and efficacy of immunosuppressive therapy for elderly patients with severe aplastic anaemia.

Uncertainty remains regarding the safety and tolerability of immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG) and cyclosporine (CSA) in older patients. We retrospectively analysed two prospective clinical trials of IST in treatment-naïve severe aplastic anaemia (SAA) to assess safety in older compared to younger patients. Patients ≥18 years of age who had received IST with ATG and CSA +/- eltrombopag (EPAG) were included. Pre-treatment baseline characteristics and co-morbidities were assessed as predictors of therapy-related complications in younger (<60 years) versus older (≥60 years) patients. Out of 245 eligible patients, 54 were older and 191 were younger. Older patients had a similar frequency of SAEs, ICU admissions and hospital length of stay compared to younger patients. Older patients had a higher frequency of cardiac events related to IST, but none resulted in death. Older patients had worse long-term overall survival, and more relapse and clonal evolution post-IST. However, older patients who responded to IST had a similar survival at a median follow-up to younger patients. Disease-related factors and limited therapeutic options in refractory disease likely contribute to poorer outcomes in older patients, not complications of upfront IST. Therefore, IST should be considered first-line therapy for most older SAA patients.

Long-term outcomes in patients with severe aplastic anemia treated with immunosuppression and eltrombopag: a phase 2 study.

Patients with severe aplastic anemia (SAA) are either treated with bone marrow transplant (BMT) or immunosuppression (IST) depending on their age, comorbidities, and available donors. In 2017, our phase 2 trial reported improved hematologic responses with the addition of eltrombopag (EPAG) to standard IST for SAA when compared with a historical cohort treated with IST alone. However, the rates and characteristics of long-term complications, relapse, and clonal evolution, previously described in patients treated with IST alone, are not yet known with this new regimen, IST and EPAG. Patients were accrued from 2012 to 2020, with a total of 178 subjects included in this secondary endpoint analysis. With double the sample size and a much longer median follow-up (4 years) since the original publication in 2017, we report a cumulative relapse rate of 39% in responding patients who received cyclosporine (CSA) maintenance and clonal evolution of 15% in all treated patients at 4 years. Relapse occurred at distinct timepoints: after CSA dose reduction and EPAG discontinuation at 6 months, and after 2 years when CSA was discontinued. Most relapsed patients were retreated with therapeutic doses of CSA +/- EPAG, and two-thirds responded. Clonal evolution to a myeloid malignancy or chromosome 7 abnormality (high-risk) was noted in 5.7% of patients and conferred a poorer overall survival. Neither relapse nor high-risk evolution occurred at a higher rate than was observed in a historical comparator cohort, but the median time to both events was earlier in IST and EPAG treated patients. This trial was registered at www.clinicaltrials.gov as #NCT01623167.

An evolutionarily conserved ribosome-rescue pathway maintains epidermal homeostasis.

Ribosome-associated mRNA quality control mechanisms ensure the fidelity of protein translation1,2. Although these mechanisms have been extensively studied in yeast, little is known about their role in mammalian tissues, despite emerging evidence that stem cell fate is controlled by translational mechanisms3,4. One evolutionarily conserved component of the quality control machinery, Dom34 (in higher eukaryotes known as Pelota (Pelo)), rescues stalled ribosomes 5 . Here we show that Pelo is required for mammalian epidermal homeostasis. Conditional deletion of Pelo in mouse epidermal stem cells that express Lrig1 results in hyperproliferation and abnormal differentiation of these cells. By contrast, deletion of Pelo in Lgr5-expressing stem cells has no effect and deletion in Lgr6-expressing stem cells induces only a mild phenotype. Loss of Pelo results in accumulation of short ribosome footprints and global upregulation of translation, rather than affecting the expression of specific genes. Translational inhibition by rapamycin-mediated downregulation of mTOR (mechanistic target of rapamycin kinase) rescues the epidermal phenotype. Our study reveals that the ribosome-rescue machinery is important for mammalian tissue homeostasis and that it has specific effects on different stem cell populations.

Individual- and Neighborhood-Level Disparities in Audio-Only Telemedicine Utilization Across a Large Academic Health System.

Introduction: The objective of this study was to understand whether use of audio-only telemedicine visits differed by individual- and neighborhood-level patient characteristics during the COVID-19 pandemic. Methods: We conducted a retrospective cross-sectional study of telemedicine encounter data from a large academic health system. The primary outcome was rate of audio-only versus video visits. The exposures of interest were individual- (age, race, insurance, preferred language) and neighborhood-level (Social Deprivation Index [SDI]) patient characteristics. Results: Our study included 1,054,465 patient encounters from January 1, 2020 to December 31, 2021, of which 18.33% were completed via audio-only. Encounters among adults 75 years or older, Black patients, Spanish-speakers, and those with public insurance were more frequently conducted by audio-only (p < 0.001). Overall, populations showed decreasing rates of audio-only visits over time. We also observed an increase in the rate of audio-only encounters as SDI scores increased. Discussion: We found that audio-only disparities exist in telemedicine utilization by individual and zip code level characteristics. Though these disparities have improved over time as seen by our temporal analysis, marginalized and minority groups still showed the lowest rates of video utilization. In conclusion, access to audio-only care is a critical component to ensure that telemedicine is accessible to all populations. State and federal policy should support continued reimbursement of audio-only care to ensure equitable access to care while the implications of different care modalities are further studied.

Multi-Ethnic Study of Atherosclerosis: Relationship between Left Ventricular Shape at Cardiac MRI and 10-year Outcomes.

Background Left ventricular (LV) subclinical remodeling is associated with adverse outcomes and indicates mechanisms of disease development. Standard metrics such as LV mass and volumes may not capture the full range of remodeling. Purpose To quantify the relationship between LV three-dimensional shape at MRI and incident cardiovascular events over 10 years. Materials and Methods In this retrospective study, 5098 participants from the Multi-Ethnic Study of Atherosclerosis who were free of clinical cardiovascular disease underwent cardiac MRI from 2000 to 2002. LV shape models were automatically generated using a machine learning workflow. Event-specific remodeling signatures were computed using partial least squares regression, and random survival forests were used to determine which features were most associated with incident heart failure (HF), coronary heart disease (CHD), and cardiovascular disease (CVD) events over a 10-year follow-up period. The discrimination improvement of adding LV shape to traditional cardiovascular risk factors, coronary artery calcium scores, and N-terminal pro-brain natriuretic peptide levels was assessed using the index of prediction accuracy and time-dependent area under the receiver operating characteristic curve (AUC). Kaplan-Meier survival curves were used to illustrate the ability of remodeling signatures to predict the end points. Results Overall, 4618 participants had sufficient three-dimensional MRI information to generate patient-specific LV models (mean age, 60.6 years ± 9.9 [SD]; 2540 women). Among these participants, 147 had HF, 317 had CHD, and 455 had CVD events. The addition of LV remodeling signatures to traditional cardiovascular risk factors improved the mean AUC for 10-year survival prediction and achieved better performance than LV mass and volumes; HF (AUC, 0.83 ± 0.01 and 0.81 ± 0.01, respectively; P < .05), CHD (AUC, 0.77 ± 0.01 and 0.75 ± 0.01, respectively; P < .05), and CVD (AUC, 0.78 ± 0.0 and 0.76 ± 0.0, respectively; P < .05). Kaplan-Meier analysis demonstrated that participants with high-risk HF remodeling signatures had a 10-year survival rate of 56% compared with 95% for those with low-risk scores. Conclusion Left ventricular event-specific remodeling signatures were more predictive of heart failure, coronary heart disease, and cardiovascular disease events over 10 years than standard mass and volume measures and enable an automatic personalized medicine approach to tracking remodeling. © RSNA, 2022 Online supplemental material is available for this article.

HLA associations, somatic loss of HLA expression, and clinical outcomes in immune aplastic anemia.

Immune aplastic anemia (AA) features somatic loss of HLA class I allele expression on bone marrow cells, consistent with a mechanism of escape from T-cell-mediated destruction of hematopoietic stem and progenitor cells. The clinical significance of HLA abnormalities has not been well characterized. We examined the somatic loss of HLA class I alleles and correlated HLA loss and mutation-associated HLA genotypes with clinical presentation and outcomes after immunosuppressive therapy in 544 AA patients. HLA class I allele loss was detected in 92 (22%) of the 412 patients tested, in whom there were 393 somatic HLA gene mutations and 40 instances of loss of heterozygosity. Most frequently affected was HLA-B*14:02, followed by HLA-A*02:01, HLA-B*40:02, HLA-B*08:01, and HLA-B*07:02. HLA-B*14:02, HLA-B*40:02, and HLA-B*07:02 were also overrepresented in AA. High-risk clonal evolution was correlated with HLA loss, HLA-B*14:02 genotype, and older age, which yielded a valid prediction model. In 2 patients, we traced monosomy 7 clonal evolution from preexisting clones harboring somatic mutations in HLA-A*02:01 and HLA-B*40:02. Loss of HLA-B*40:02 correlated with higher blood counts. HLA-B*07:02 and HLA-B*40:01 genotypes and their loss correlated with late-onset of AA. Our results suggest the presence of specific immune mechanisms of molecular pathogenesis with clinical implications. HLA genotyping and screening for HLA loss may be of value in the management of immune AA. This study was registered at clinicaltrials.gov as NCT00001964, NCT00061360, NCT00195624, NCT00260689, NCT00944749, NCT01193283, and NCT01623167.

Granulocyte transfusions in severe aplastic anemia.

Patients with severe aplastic anemia (SAA) are at high risk for morbidity and mortality due to severe infections. We aimed to characterize the role of granulocyte transfusion (GT) in SAA. Primary outcomes were survival from first GT, including overall survival (OS) at last follow up, survival to discharge, and receipt of HSCT. Secondary outcomes included evaluation of clinical response at 7 and 30 days after GT initiation based on a clinical scoring system incorporating microbiological and radiographic response. Twenty-eight SAA patients underwent 30 GT courses with a per-dose median of 1.28 x 109 granulocyte cells/kilogram (range 0.45-4.52 x 109). OS from initial GT to median last follow up (551 days) was 50%, with 39% (11/28) alive at last follow up. Sixty-four percent (18/28) of all patients survived to hospital discharge. Patients with complete, partial, or stable response at 30 days had significantly improved OS compared to non-responders (p=0.0004). Eighty-six percent (18/21) of patients awaiting HSCT during GT underwent transplant and 62% (13/21) survived to post-HSCT discharge. Sex, type of infection, or percentage of days with absolute neutrophil count > 0.2x109/L during GT course were not predictive of survival (p=0.52, p=0.7, p=0.28). Nine of 28 (32%) patients developed new or increased human leukocyte antigen (HLA) alloimmunization during their GT course. GTs in SAA may impact survival in those with improvement or stabilization of their underlying infection. Alloimmunization can occur and OS in this population remains poor, but GTs may be a useful tool to bridge patients to curative treatment with HSCT.

Thoracic Aortic Volume as a Predictor of Cardiovascular Events: The Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: It is unclear whether thoracic aortic volume (TAV) is useful for cardiovascular (CV) disease prognosis and risk assessment. PURPOSE: This study evaluated cross-sectional associations of TAV with CV risk factors, and longitudinal association with incident CV events in the multiethnic study of atherosclerosis. STUDY TYPE: Retrospective cohort analysis of prospective data. POPULATION: 1182 participants (69 ± 9 years, 54% female, 37% Caucasian, 18% Chinese, 31% African American, 14% Hispanic, 60% hypertensive, and 20% diabetic) without prior CV disease. FIELD STRENGTH AND SEQUENCES: Axial black-blood turbo spin echo or bright blood steady-state free precession images on 1.5T scanners. ASSESSMENT: TAV was calculated using Simpson's method from axial images, and included the ascending arch and descending segments. Traditional CV risk factors were assessed at the time of MRI. CV outcomes over a 9-year follow-up period were recorded and represented a composite of stroke, stroke death, coronary heart disease (CHD), CHD death, atherosclerotic death, and CVD death. STATISTICAL TESTS: Multivariable linear regression models adjusted for height and weight were used to determine the relationship (ß coefficient) between TAV and CV risk factors. Cox regression models assessed the association of TAV and incident CV events. A P-value of <0.05 was deemed statistically significant. RESULTS: Mean TAV was = 139 ± 41 mL. In multivariable regression, TAV was directly associated with age (ß = 1.6), male gender (ß = 23.9), systolic blood pressure (ß = 0.1), and hypertension medication use (ß = 7.9); and inversely associated with lipid medication use (ß = -5.3) and treated diabetes (ß = -8.9). Compared to Caucasians, Chinese Americans had higher TAV (ß = 11.4), while African Americans had lower TAV (ß = -7.0). Higher TAV was independently associated with incident CV events (HR: 1.057 per 10 mL). CONCLUSION: Greater TAV is associated with incident CV events, increased age, and hypertension in a large multiethnic population while treated diabetes and lipid medication use were associated with lower TAV. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.