Association of Mutations Contributing to Clonal Hematopoiesis With Prognosis in Chronic Ischemic Heart Failure

Increased stem cell proliferation in atherosclerosis accelerates clonal hematopoiesis

Clonal hematopoiesis, a condition in which individual hematopoietic stem cell clones generate a disproportionate fraction of blood leukocytes, correlates with higher risk for cardiovascular disease. The mechanisms behind this association are incompletely understood. Here, we show that hematopoietic stem cell division rates are increased in mice and humans with atherosclerosis. Mathematical analysis demonstrates that increased stem cell proliferation expedites somatic evolution and expansion of clones with driver mutations. The experimentally determined division rate elevation in atherosclerosis patients is sufficient to produce a 3.5-fold increased risk of clonal hematopoiesis by age 70. We confirm the accuracy of our theoretical framework in mouse models of atherosclerosis and sleep fragmentation by showing that expansion of competitively transplanted Tet2^-/- cells is accelerated under conditions of chronically elevated hematopoietic activity. Hence, increased hematopoietic stem cell proliferation is an important factor contributing to the association between cardiovascular disease and clonal hematopoiesis.

The vasculature: a therapeutic target in heart failure?

It is well established that the vasculature plays a crucial role in maintaining oxygen and nutrients supply to the heart. Increasing evidence further suggest that the microcirculation has additional roles in supporting a healthy microenvironment. Heart failure is well known to be associated with changes and functional impairment of the microvasculature. The specific ablation of protective signals in endothelial cells in experimental models is sufficient to induce heart failure. Therefore, restoring a healthy endothelium and microcirculation may be a valuable therapeutic strategy to treat heart failure. The present review article will summarize the current understanding of the vascular contribution to heart failure with reduced or preserved ejection fraction. Novel therapeutic approaches including next generation pro-angiogenic therapies and non-coding RNA therapeutics, as well as the targeting of metabolites or metabolic signaling, vascular inflammation and senescence will be discussed.

Healthy Lifestyle and Clonal Hematopoiesis of Indeterminate Potential: Results From the Women's Health Initiative

Background

Presence of clonal hematopoiesis of indeterminate potential (CHIP) is associated with a higher risk of atherosclerotic cardiovascular disease, cancer, and mortality. The relationship between a healthy lifestyle and CHIP is unknown.

Methods and Results

This analysis included 8709 postmenopausal women (mean age, 66.5 years) enrolled in the WHI (Women's Health Initiative), free of cancer or cardiovascular disease, with deep‐coverage whole genome sequencing data available. Information on lifestyle factors (body mass index, smoking, physical activity, and diet quality) was obtained, and a healthy lifestyle score was created on the basis of healthy criteria met (0 point [least healthy] to 4 points [most healthy]). CHIP was derived on the basis of a prespecified list of leukemogenic driver mutations. The prevalence of CHIP was 8.6%. A higher healthy lifestyle score was not associated with CHIP (multivariable‐adjusted odds ratio [OR] [95% CI], 0.99 [0.80–1.23] and 1.13 [0.93–1.37]) for the upper (3 or 4 points) and middle category (2 points), respectively, versus referent (0 or 1 point). Across score components, a normal and overweight body mass index compared with obese was significantly associated with a lower odds for CHIP (OR, 0.71 [95% CI, 0.57–0.88] and 0.83 [95% CI, 0.68–1.01], respectively; P‐trend 0.0015). Having never smoked compared with being a current smoker tended to be associated with lower odds for CHIP.

Conclusions

A healthy lifestyle, based on a composite score, was not related to CHIP among postmenopausal women. However, across individual lifestyle factors, having a normal body mass index was strongly associated with a lower prevalence of CHIP. These findings support the idea that certain healthy lifestyle factors are associated with a lower frequency of CHIP.

Terminally Differentiated CD4+ T Cells Promote Myocardial Inflammaging

The cardiovascular and immune systems undergo profound and intertwined alterations with aging. Recent studies have reported that an accumulation of memory and terminally differentiated T cells in elderly subjects can fuel myocardial aging and boost the progression of heart diseases. Nevertheless, it remains unclear whether the immunological senescence profile is sufficient to cause age-related cardiac deterioration or merely acts as an amplifier of previous tissue-intrinsic damage. Herein, we sought to decompose the causality in this cardio-immune crosstalk by studying young mice harboring a senescent-like expanded CD4+ T cell compartment. Thus, immunodeficient NSG-DR1 mice expressing HLA-DRB1*01:01 were transplanted with human CD4+ T cells purified from matching donors that rapidly engrafted and expanded in the recipients without causing xenograft reactions. In the donor subjects, the CD4+ T cell compartment was primarily composed of naïve cells defined as CCR7+CD45RO-. However, when transplanted into young lymphocyte-deficient mice, CD4+ T cells underwent homeostatic expansion, upregulated expression of PD-1 receptor and strongly shifted towards effector/memory (CCR7- CD45RO+) and terminally-differentiated phenotypes (CCR7-CD45RO-), as typically seen in elderly. Differentiated CD4+ T cells also infiltrated the myocardium of recipient mice at comparable levels to what is observed during physiological aging. In addition, young mice harboring an expanded CD4+ T cell compartment showed increased numbers of infiltrating monocytes, macrophages and dendritic cells in the heart. Bulk mRNA sequencing analyses further confirmed that expanding T-cells promote myocardial inflammaging, marked by a distinct age-related transcriptomic signature. Altogether, these data indicate that exaggerated CD4+ T-cell expansion and differentiation, a hallmark of the aging immune system, is sufficient to promote myocardial alterations compatible with inflammaging in juvenile healthy mice.

Employing the CRISPR-Cas System for Clonal Hematopoiesis Research

Clonal hematopoiesis is a state in which substantial fraction of hematopoietic stem cells acquire mutations in specific driver genes and expand in the absence of an overt hematological malignancy. Recent clinical studies have shown that clonal hematopoiesis increases likelihood of hematological malignancy and cardiovascular disease. While clinical studies have identified countless candidate driver genes associated with clonal hematopoiesis, experimental studies are required to evaluate causal and mechanistic relationships with disease processes. This task is technically difficult and expensive to achieve with traditional genetically engineered mice. The versatility and programmability of CRISPR-Cas system enables investigators to evaluate the pathogenesis of each mutation in experimental systems. Technical refinements have enabled gene editing in a cell type specific manner and at a single base pair resolution. Here, we summarize strategies to apply CRISPR-Cas system to experimental studies of clonal hematopoiesis and concerns that should be addressed.

Clinico-genetic findings in 509 frontotemporal dementia patients

Frontotemporal dementia (FTD) is a clinically and genetically heterogeneous disorder. To which extent genetic aberrations dictate clinical presentation remains elusive. We investigated the spectrum of genetic causes and assessed the genotype-driven differences in biomarker profiles, disease severity and clinical manifestation by recruiting 509 FTD patients from different centers of the German FTLD consortium where individuals were clinically assessed including biomarker analysis. Exome sequencing as well as C9orf72 repeat analysis were performed in all patients. These genetic analyses resulted in a diagnostic yield of 18.1%. Pathogenic variants in C9orf72 (n = 47), GRN (n = 26), MAPT (n = 11), TBK1 (n = 5), FUS (n = 1), TARDBP (n = 1), and CTSF (n = 1) were identified across all clinical subtypes of FTD. TBK1-associated FTD was frequent accounting for 5.4% of solved cases. Detection of a homozygous missense variant verified CTSF as an FTD gene. ABCA7 was identified as a candidate gene for monogenic FTD. The distribution of APOE alleles did not differ significantly between FTD patients and the average population. Male sex was weakly associated with clinical manifestation of the behavioral variant of FTD. Age of onset was lowest in MAPT patients. Further, high CSF neurofilament light chain levels were found to be related to GRN-associated FTD. Our study provides large-scale retrospective clinico-genetic data such as on disease manifestation and progression of FTD. These data will be relevant for counseling patients and their families.

Inflammation in Heart Failure: JACC State-of-the-Art Review

It has long been observed that heart failure (HF) is associated with measures of systemic inflammation. In recent years, there have been significant advancements in our understanding of how inflammation contributes to the pathogenesis and progression of HF. However, although numerous studies have validated the association between measures of inflammation and HF severity and prognosis, clinical trials of anti-inflammatory therapies have proven mostly unsuccessful. On this backdrop emerges the yet unmet goal of targeting precise phenotypes within the syndrome of HF; if such precise definitions can be realized, and with better understanding of the roles played by specific inflammatory mediators, the expectation is that targeted anti-inflammatory therapies may improve prognosis in patients whose HF is driven by inflammatory pathobiology. Here, the authors describe mechanistic links between inflammation and HF, discuss traditional and novel inflammatory biomarkers, and summarize the latest evidence from clinical trials of anti-inflammatory therapies.

Cancer Risk in the Heart Failure Population: Epidemiology, Mechanisms, and Clinical Implications

PURPOSE OF REVIEW

Along with population aging, the incidence of both heart failure (HF) and cancer is increasing. However, little is known about new-onset cancer in HF patients. This review aims at showing recent discoveries concerning this subset of patients.

RECENT FINDINGS

Not only cancer and HF share similar risk factors but also HF itself can stimulate cancer development. Some cytokines produced by the failing heart induce mild inflammation promoting carcinogenesis, as it has been recently suggested by an experimental model of HF in mice. The incidence of new-onset cancer is higher in HF patients compared to the general population, and it significantly worsens their prognosis. Moreover, the management of HF patients developing new-onset cancer is challenging, especially due to the limited therapeutic options for patients affected by both cancer and HF and the higher risk of cardiotoxicity from anticancer drugs.

Common mechanistic pathways in cancer and heart failure. A scientific roadmap on behalf of the Translational Research Committee of the Heart Failure Association (HFA) of the European Society of Cardiology (ESC)

The co-occurrence of cancer and heart failure (HF) represents a significant clinical drawback as each disease interferes with the treatment of the other. In addition to shared risk factors, a growing body of experimental and clinical evidence reveals numerous commonalities in the biology underlying both pathologies. Inflammation emerges as a common hallmark for both diseases as it contributes to the initiation and progression of both HF and cancer. Under stress, malignant and cardiac cells change their metabolic preferences to survive, which makes these metabolic derangements a great basis to develop intersection strategies and therapies to combat both diseases. Furthermore, genetic predisposition and clonal haematopoiesis are common drivers for both conditions and they hold great clinical relevance in the context of personalized medicine. Additionally, altered angiogenesis is a common hallmark for failing hearts and tumours and represents a promising substrate to target in both diseases. Cardiac cells and malignant cells interact with their surrounding environment called stroma. This interaction mediates the progression of the two pathologies and understanding the structure and function of each stromal component may pave the way for innovative therapeutic strategies and improved outcomes in patients. The interdisciplinary collaboration between cardiologists and oncologists is essential to establish unified guidelines. To this aim, pre-clinical models that mimic the human situation, where both pathologies coexist, are needed to understand all the aspects of the bidirectional relationship between cancer and HF. Finally, adequately powered clinical studies, including patients from all ages, and men and women, with proper adjudication of both cancer and cardiovascular endpoints, are essential to accurately study these two pathologies at the same time.

Clonal Hematopoiesis-Driver DNMT3A Mutations Alter Immune Cells in Heart Failure

RATIONALE

Clonal hematopoiesis driven by mutations of DNMT3A (DNA methyltransferase 3a) is associated with increased incidence of cardiovascular disease and poor prognosis of patients with chronic heart failure (HF) and aortic stenosis. Although experimental studies suggest that DNMT3A clonal hematopoiesis-driver mutations may enhance inflammation, specific signatures of inflammatory cells in humans are missing.

OBJECTIVE

To define subsets of immune cells mediating inflammation in humans using single-cell RNA sequencing.

METHODS AND RESULTS

Transcriptomic profiles of peripheral blood mononuclear cells were analyzed in n=6 patients with HF harboring DNMT3A clonal hematopoiesis-driver mutations and n=4 patients with HF and no DNMT3A mutations by single-cell RNA sequencing. Monocytes of patients with HF carrying DNMT3A mutations demonstrated a significantly increased expression of inflammatory genes compared with monocytes derived from patients with HF without DNMT3A mutations. Among the specific upregulated genes were the prototypic inflammatory IL (interleukin) IL1B (interleukin 1B), IL6, IL8, the inflammasome NLRP3, and the macrophage inflammatory proteins CCL3 and CCL4 as well as resistin, which augments monocyte-endothelial adhesion. Silencing of DNMT3A in monocytes induced a paracrine proinflammatory activation and increased adhesion to endothelial cells. Furthermore, the classical monocyte subset of DNMT3A mutation carriers showed increased expression of T-cell stimulating immunoglobulin superfamily members CD300LB, CD83, SIGLEC12, as well as the CD2 ligand and cell adhesion molecule CD58, all of which may be involved in monocyte-T-cell interactions. DNMT3A mutation carriers were further characterized by increased expression of the T-cell alpha receptor constant chain and changes in T helper cell 1, T helper cell 2, T helper cell 17, CD8+ effector, CD4+ memory, and regulatory T-cell-specific signatures.

CONCLUSIONS

This study demonstrates that circulating monocytes and T cells of patients with HF harboring clonal hematopoiesis-driver mutations in DNMT3A exhibit a highly inflamed transcriptome, which may contribute to the aggravation of chronic HF.

Immunometabolic control of hematopoiesis

Hematopoietic stem cells (HSC) lie at the center of the hematopoiesis process, as they bear capacity to self-renew and generate all hematopoietic lineages, hence, all mature blood cells. The ability of HSCs to recognize systemic infection or inflammation or other forms of peripheral stress, such as blood loss, is essential for demand-adapted hematopoiesis. Also of critical importance for HSC function, specific metabolic cues (e.g., associated with changes in energy or O₂ levels) can regulate HSC function and fate decisions. In this regard, the metabolic adaptation of HSCs facilitates their switching between different states, namely quiescence, self-renewal, proliferation and differentiation. Specific metabolic alterations in hematopoietic stem and progenitor cells (HSPCs) have been linked with the induction of trained myelopoiesis in the bone marrow as well as with HSPC dysfunction in aging and clonal hematopoiesis of indeterminate potential (CHIP). Thus, HSPC function is regulated by both immunologic/inflammatory and metabolic cues. The immunometabolic control of HSPCs and of hematopoiesis is discussed in this review along with the translational implications thereof, that is, how metabolic pathways can be therapeutically manipulated to prevent or reverse HSPC dysfunction or to enhance or attenuate trained myelopoiesis according to the needs of the host.

The role of clonal haematopoiesis in cardiovascular diseases: epidemiology and experimental studies

Clonal haematopoiesis results from acquired mutations in haematopoietic stem and progenitor cells (HSPCs). These mutations can confer the HSPC with a competitive advantage, leading to their clonal expansion within the limiting bone marrow niche. This process is often insufficient to produce a haematologic malignancy; however, the expanding HSPC clones increasingly give rise to progeny leucocytes whose phenotypes can be altered by the somatic mutations that they harbour. Key findings from multiple human studies have shown that clonal haematopoiesis in the absence of overt haematologic alterations is common amongst the ageing population and associated with mortality and cardiovascular disease. Key findings from experimental studies have provided evidence for a causative role for clonal haematopoiesis in cardiovascular diseases, and aspects of these mechanisms have been elucidated. Whilst our understanding of the impact and biology of clonal haematopoiesis is in its infancy, analyses of some of the most commonly mutated driver genes suggest promising clinical scenarios involving the development of personalized therapies with immunomodulatory drugs that exploit the perturbation caused by the particular mutation. Herein, we review the accumulating epidemiological and experimental evidence, and summarize our current understanding of the importance of clonal haematopoiesis as a new causal risk factor for atherosclerotic cardiovascular disease and heart failure.

Clonal Hematopoiesis, Cardiovascular Diseases and Hematopoietic Stem Cells

Cardiovascular diseases and cancer, the leading causes of morbidity and mortality in the elderly, share some common mechanisms, in particular inflammation, contributing to their progression and pathogenesis. However, somatic mutagenesis, a driving force in cancer development, has not been generally considered as an important factor in cardiovascular disease pathology. Recent studies demonstrated that during normal aging, somatic mutagenesis occurs in blood cells, often resulting in expansion of mutant clones that dominate hematopoiesis at advanced age. This clonal hematopoiesis is primarily associated with mutations in certain leukemia-related driver genes and, being by itself relatively benign, not only increases the risks of subsequent malignant hematopoietic transformation, but, unexpectedly, has a significant impact on progression of atherosclerosis and cardiovascular diseases. In this review, we discuss the phenomenon of clonal hematopoiesis, the most important genes involved in it, its impact on cardiovascular diseases, and relevant aspects of hematopoietic stem cell biology.

Clonal hematopoiesis and nonhematologic disorders

Clonal expansions of mutated hematopoietic cells, termed clonal hematopoiesis, are common in aging humans. One expected consequence of mutation-associated clonal hematopoiesis is an increased risk of hematologic cancers, which has now been shown in several studies. However, the hematopoietic stem cells that acquire these somatic mutations also give rise to mutated immune effector cells, such as monocytes, granulocytes, and lymphocytes. These effector cells can potentially influence many disease states, especially those with a chronic inflammatory component. Indeed, several studies have now shown that clonal hematopoiesis associates with increased risk of atherosclerotic cardiovascular disease. Emerging data also associate clonal hematopoiesis with other nonhematologic diseases. Here, we will review recent studies linking clonal hematopoiesis to altered immune function, inflammation, and nonmalignant diseases of aging.

Genetics of age-related clonal hematopoiesis and atherosclerotic cardiovascular disease

PURPOSE OF REVIEW

While advanced age is the major risk factor for the development of atherosclerotic cardiovascular disease (ASCVD), we have a poor understanding of how aging promotes the progression of this disease. Recent evidence suggests that the age-dependent accumulation of somatic mutations in hematopoietic cells may represent a new causal risk factor for ASCVD.

RECENT FINDINGS

A hallmark of aging is the accumulation of somatic DNA mutations in all tissues of the body. Accordingly, evidence shows that hematopoietic stem/progenitor cells accumulate somatic mutations as a function of age in nonsymptomatic individuals. When these mutations occur in driver genes that provide a selective advantage to the hematopoietic stem/progenitor cells, they undergo a clonal expansion and progressively give rise to blood leukocytes that harbor these mutations. This phenomenon, referred to as clonal hematopoiesis, has been associated with the increased risk of mortality, hematologic malignancy, ASCVD, and related diseases. Notably, many individuals exhibiting clonal hematopoiesis carry single 'driver' mutations in preleukemic genes including DNA methyltransferase 3a, ten-eleven translocation 2, additional sex combs like 1, and Janus kinase 2. Experimental studies show that these mutations in some of these genes can alter the inflammatory properties of the leukocyte and contribute to the pathogenesis of ASCVD.

SUMMARY

We review recent epidemiological and experimental findings on the association between age-related clonal hematopoiesis and ASCVD by focusing on prevalent driver gene mutations.

IDH1/2 mutations in acute myeloid leukemia patients and risk of coronary artery disease and cardiac dysfunction-a retrospective propensity score analysis

Clonal hematopoiesis of indeterminate potential (CHIP) is linked to leukemia gene mutations and associates with an increased risk for coronary artery disease and poor prognosis in ischemic cardiomyopathy. Two recurrently mutated genes in CHIP and adult acute myeloid leukemia (AML) encode for isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). Global expression of mutant IDH2 in transgenic mice-induced dilated cardiomyopathy and muscular dystrophy. In this retrospective observational study, we investigated whether mutant IDH1/2 predisposes to cardiovascular disease in AML patients. Among 363 AML patients, IDH1 and IDH2 mutations were detected in 26 (7.2%) and 39 patients (10.7%), respectively. Mutant IDH1 patients exhibited a significantly higher prevalence of coronary artery disease (26.1% vs. 6.4%, p = 0.002). Applying inverse probability-weighting analysis, patients with IDH1/2 mutations had a higher risk for a declining cardiac function during AML treatment compared to IDH1/2 wild type patients [left ventricular ejection fraction pretreatment compared to 10 months after diagnosis: 59.2% to 41.9% (p < 0.001) vs 58.5% to 55.4% (p = 0.27), respectively]. Mechanistically, RNA sequencing and immunostaining in hiPS-derived cardiomyocytes indicated that the oncometabolite R-2HG exacerbated doxorubicin mediated cardiotoxicity. Evaluation of IDH1/2 mutation status may therefore help identifying AML patients at risk for cardiovascular complications during cytotoxic treatment.

Differential risk of incident cancer in patients with heart failure: A nationwide population-based cohort study

BACKGROUND

Heart failure (HF) and cancer are currently two leading causes of mortality, and sometimes coexist. However, the relationship between them is not completely elucidated. We aimed to investigate whether patients with HF are predisposed to cancer development using the large Korean National Health Insurance claims database.

METHODS

This study included 128,441 HF patients without a history of cancer and 642,205 age- and sex-matched individuals with no history of cancer and HF between 1 January 2010 and 31 December 2015.

RESULTS

During a median follow-up of 4.06 years, 11,808 patients from the HF group and 40,805 participants from the control were newly diagnosed with cancer (cumulative incidence, 9.2% vs. 6.4%, p < 0.0001). Patients with HF presented a higher risk for cancer development compared to controls in multivariable Cox analysis [hazard ratio (HR) 1.64, 95% confidence interval (CI) 1.61-1.68]. The increased risk was consistent for all site-specific cancers. To minimize potential surveillance bias, additional analysis was performed by eliminating participants who developed cancer within the initial 2 years of HF diagnosis (i.e. 2-year lag analysis). In the 2-year lag analysis, the higher risk of overall cancer remained significant in patients with HF (HR 1.09, 95% CI 1.05-1.13), although the association was weaker. Among the site-specific cancers, three types of cancer (lung, liver/biliary/pancreas, and hematologic malignancy) were consistently at higher risk in patients with HF. An exploratory analysis showed that patients with repeated HF hospitalization had a higher risk of cancer development compared to those without, in a pattern of stepwise increases across the three groups [controls vs. HF without re-hospitalization vs. HF with re-hospitalization ≥1; HR (95% CI), 1.00 (reference) vs. 1.55 (1.51-1.59) vs. 1.96 (1.89-2.03), respectively].

CONCLUSIONS

Cancer incidence is higher in patients with HF than the general population. Active surveillance of coexisting malignancy needs to be considered in these patients.

Integrative Genomic Analysis Reveals Cancer-Associated Gene Mutations in Chronic Myeloid Leukemia Patients with Resistance or Intolerance to Tyrosine Kinase Inhibitor

Introduction

While the acquisition of mutations in the ABL1 kinase domain (KD) has been identified as a common mechanism behind tyrosine kinase inhibitor (TKI) resistance, recent genetic studies have revealed that patients with TKI resistance or intolerance frequently harbor one or more genetic alterations implicated in myeloid malignancies. This suggests that additional mutations other than ABL1 KD mutations might contribute to disease progression.

Methods

We performed targeted-capture sequencing of 127 known and putative cancer-related genes of 63 patients with CML using next-generation sequencing (NGS), including 42 patients with TKI resistance and 21 with TKI intolerance.

Results

The differences in the number of mutations between groups had no statistical significance. This could be explained in part by not all of the patients having achieved major molecular remission in the early period as expected. Overall, 66 mutations were identified in 96.8% of the patients, most frequently in the KTM2C (31.82%), ABL1 (31.82%), FAT1 (25.76%), and ASXL1 (22.73%) genes. CUX1, KIT, and GATA2 were associated with TKI intolerance, and two of them (CUX1, GATA2) are transcription factors in which mutations were identified in 82.61% of patients with TKI intolerance. ASXL1 mutations were found more frequently in patients with ABL1 KD mutations (38.1% vs 15.21%, P=0.041). Although the number of mutations was low, pairwise interaction between mutated genes showed that ABL1 KD mutations cooccurred with SH2B3 mutations (P<0.05). In Kaplan-Meier analyses, only TET2 mutations were associated with shorter progression-free survival (P=0.026).

Conclusion

Our data suggested that the CUX1, KIT, and GATA2 genes may play important roles in TKI intolerance. ASXL1 and TET2 mutations may be associated with poor patient prognosis. NGS helps improving the clinical risk stratification, which enables the identification of patients with TKI resistance or intolerance in the era of TKI therapy.

Clonal Hematopoiesis of Indeterminate Potential: A Multidisciplinary Challenge in Personalized Hematology

Clonal hematopoiesis of indeterminate potential (CHIP) is a common age-related condition that represents a potential pre-phase of hematologic neoplasm. Next-generation sequencing (NGS) is used to detect and monitor clonal hematopoiesis, and the spectrum of mutations substantially overlaps with that of myeloid neoplasms with DNMT3A, TET2, ASXL1, and JAK2 being the most frequently mutated. While, in general, the risk of progression to an overt myeloid neoplasm is only modest, the progression risk increases in patients with unexplained cytopenia or multiple mutations. In addition, CHIP represents a previously unrecognized major risk factor for atherosclerosis and cardiovascular disease (CVD), including coronary heart disease, degenerative aortic valve stenosis, and chronic heart failure; and a causative role of CHIP in the development of CVD has been demonstrated in vitro and in vivo. The management of patients with CHIP is a rapidly emerging topic in personalized medicine, as NGS has become widely available for clinical medicine. It requires a highly multidisciplinary setting, including hematology/oncology, cardiology, (clinical) pathology, and genetics for individualized guidance. Further research is urgently needed to provide robust evidence for future guidelines and recommendations on the management of patients with CHIP in the era of personalized medicine.

The transcriptome of CMML monocytes is highly inflammatory and reflects leukemia-specific and age-related alterations

Chronic myelomonocytic leukemia (CMML) is an aggressive myeloid neoplasm of older individuals characterized by persistent monocytosis. Somatic mutations in CMML are heterogeneous and only partially explain the variability in clinical outcomes. Recent data suggest that cardiovascular morbidity is increased in CMML and contributes to reduced survival. Clonal hematopoiesis of indeterminate potential (CHIP), the presence of mutated blood cells in hematologically normal individuals, is a precursor of age-related myeloid neoplasms and associated with increased cardiovascular risk. To isolate CMML-specific alterations from those related to aging, we performed RNA sequencing and DNA methylation profiling on purified monocytes from CMML patients and from age-matched (old) and young healthy controls. We found that the transcriptional signature of CMML monocytes is highly proinflammatory, with upregulation of multiple inflammatory pathways, including tumor necrosis factor and interleukin (IL)-6 and -17 signaling, whereas age per se does not significantly contribute to this pattern. We observed no consistent correlations between aberrant gene expression and CpG island methylation, suggesting that proinflammatory signaling in CMML monocytes is governed by multiple and complex regulatory mechanisms. We propose that proinflammatory monocytes contribute to cardiovascular morbidity in CMML patients and promote progression by selection of mutated cell clones. Our data raise questions of whether asymptomatic patients with CMML benefit from monocyte-depleting or anti-inflammatory therapies.

Clonal Hematopoiesis in Liquid Biopsy: From Biological Noise to Valuable Clinical Implications

The use of blood liquid biopsy is being gradually incorporated into the clinical setting of cancer management. The minimally invasive nature of the usage of cell-free DNA (cfDNA) and its ability to capture the molecular alterations of tumors are great advantages for their clinical applications. However, somatic mosaicism in plasma remains an immense challenge for accurate interpretation of liquid biopsy results. Clonal hematopoiesis (CH) is part of the normal process of aging with the accumulation of somatic mutations and clonal expansion of hematopoietic stem cells. The detection of these non-tumor derived CH-mutations has been repeatedly reported as a source of biological background noise of blood liquid biopsy. Incorrect classification of CH mutations as tumor-derived mutations could lead to inappropriate therapeutic management. CH has also been associated with an increased risk of developing cardiovascular disease and hematological malignancies. Cancer patients, who are CH carriers, are more prone to develop therapy-related myeloid neoplasms after chemotherapy than non-carriers. The detection of CH mutations from plasma cfDNA analysis should be cautiously evaluated for their potential pathological relevance. Although CH mutations are currently considered as "false-positives" in cfDNA analysis, future studies should evaluate their clinical significance in healthy individuals and cancer patients.

Inflamm-ageing: the role of inflammation in age-dependent cardiovascular disease

The ongoing worldwide increase in life expectancy portends a rising prevalence of age-related cardiovascular (CV) diseases in the coming decades that demands a deeper understanding of their molecular mechanisms. Inflammation has recently emerged as an important contributor for CV disease development. Indeed, a state of chronic sterile low-grade inflammation characterizes older organisms (also known as inflamm-ageing) and participates pivotally in the development of frailty, disability, and most chronic degenerative diseases including age-related CV and cerebrovascular afflictions. Due to chronic activation of inflammasomes and to reduced endogenous anti-inflammatory mechanisms, inflamm-ageing contributes to the activation of leucocytes, endothelial, and vascular smooth muscle cells, thus accelerating vascular ageing and atherosclerosis. Furthermore, inflamm-ageing promotes the development of catastrophic athero-thrombotic complications by enhancing platelet reactivity and predisposing to plaque rupture and erosion. Thus, inflamm-ageing and its contributors or molecular mediators might furnish targets for novel therapeutic strategies that could promote healthy ageing and conserve resources for health care systems worldwide. Here, we discuss recent findings in the pathophysiology of inflamm-ageing, the impact of these processes on the development of age-related CV diseases, results from clinical trials targeting its components and the potential implementation of these advances into daily clinical practice.

Evidence of Clonal Hematopoiesis and Risk of Heart Failure

PURPOSE OF REVIEW

Clonal hematopoiesis of indeterminate potential (CHIP) is characterized by persistent clonal expansion of adult hematopoietic stem cells, which has been increasingly found to be associated with cardiovascular disease and adverse outcomes in heart failure. Here we outline emerging studies on the prevalence of CHIP, and its association with cardiovascular and heart disease.

RECENT FINDINGS

Previous genomic studies have found CHIP mutations to be associated with increased risks of arterial disease, stroke, and mortality. Murine studies exploring TET2, DNMT3A, and JAK2 mutations have shown changes in cellularity that decrease cardiac function after insult, as well as increase inflammasome activation. Mutations in driver genes are associated with worse clinical outcomes in heart failure patients, as a potential result of the proinflammatory selection in clonal hematopoiesis. Advances in the field have yielded therapeutic targets tested in recent clinical studies and may provide a valuable diagnostic of risk in heart failure.

Sex-Specific Programming of Cardiac DNA Methylation by Developmental Phthalate Exposure

Phthalate plasticizers are ubiquitous chemicals linked to several cardiovascular diseases in animal models and humans. Despite this, the mechanisms by which phthalate exposures cause adverse cardiac health outcomes are unclear. In particular, whether phthalate exposures during pregnancy interfere with normal developmental programming of the cardiovascular system, and the resulting implications this may have for long-term disease risk, are unknown. Recent studies suggest that the effects of phthalates on metabolic and neurobehavioral outcomes are sex-specific. However, the influence of sex on cardiac susceptibility to phthalate exposures has not been investigated. One mechanism by which developmental exposures may influence long-term health is through altered programming of DNA methylation. In this work, we utilized an established mouse model of human-relevant perinatal exposure and enhanced reduced representation bisulfite sequencing to investigate the long-term effects of diethylhexyl phthalate (DEHP) exposure on DNA methylation in the hearts of adult male and female offspring at 5 months of age (n = 5-7 mice per sex and exposure). Perinatal DEHP exposure led to hundreds of sex-specific, differentially methylated cytosines (DMCs) and differentially methylated regions (DMRs) in the heart. Pathway analysis of DMCs revealed enrichment for several pathways in females, including insulin signaling, regulation of histone methylation, and tyrosine phosphatase activity. In males, DMCs were enriched for glucose transport, energy generation, and developmental programs. Notably, many sex-specific genes differentially methylated with DEHP exposure in our mouse model were also differentially methylated in published data of heart tissues collected from human heart failure patients. Together, these data highlight the potential role for DNA methylation in DEHP-induced cardiac effects and emphasize the importance of sex as a biological variable in environmental health studies.

Translating Evidence from Clonal Hematopoiesis to Cardiovascular Disease: A Systematic Review

Some random mutations can confer a selective advantage to a hematopoietic stem cell. As a result, mutated hematopoietic stem cells can give rise to a significant proportion of mutated clones of blood cells. This event is known as "clonal hematopoiesis." Clonal hematopoiesis is closely associated with age, and carriers show an increased risk of developing blood cancers. Clonal hematopoiesis of indeterminate potential is defined by the presence of clones carrying a mutation associated with a blood neoplasm without obvious hematological malignancies. Unexpectedly, in recent years, it has emerged that clonal hematopoiesis of indeterminate potential carriers also have an increased risk of developing cardiovascular disease. Mechanisms linking clonal hematopoiesis of indeterminate potential to cardiovascular disease are only partially known. Findings in animal models indicate that clonal hematopoiesis of indeterminate potential-related mutations amplify inflammatory responses. Consistently, clinical studies have revealed that clonal hematopoiesis of indeterminate potential carriers display increased levels of inflammatory markers. In this review, we describe progress in our understanding of clonal hematopoiesis in the context of cancer, and we discuss the most recent findings linking clonal hematopoiesis of indeterminate potential and cardiovascular diseases.

The Clinical Challenge of Clonal Hematopoiesis, a Newly Recognized Cardiovascular Risk Factor

Importance

Despite current standards of cardiovascular care, a considerable residual burden of risk remains in both primary and secondary prevention. Clonal hematopoiesis of indeterminate potential (CHIP) has recently emerged as a common, potent, age-associated, independent risk factor for myocardial infarction, stroke, heart failure events, and survival following percutaneous aortic valve intervention. The presence of CHIP results from the acquisition of somatic mutations in a small number of leukemia driver genes found in bone marrow stem cells, leading to the expansion of leukocytes clones in peripheral blood. The association between CHIP and cardiovascular disease likely involves activation of the inflammasome pathway. More common DNA sequencing identifies individuals with CHIP who then seek advice regarding management of their cardiovascular risk.

Observations

Using clinical vignettes based on real encounters, we highlight some of the diverse presentations of CHIP, ranging from incidental identification to that detected during cancer care, that have brought patients to the attention of cardiovascular practitioners. We illustrate how we have applied a consensus-based approach to the evaluation and management of cardiovascular risk in specific patients with CHIP. Since we currently lack evidence to guide the management of these individuals, we must rely on expert opinion while awaiting data to furnish a firmer foundation for our recommendations.

Conclusions and Relevance

These vignettes illustrate that the management of CHIP should involve an individualized plan based on features such as comorbidities, life expectancy, and other traditional cardiovascular risk factors. Because individuals with CHIP will increasingly seek advice from cardiovascular specialists regarding management, these examples provide a template for approaches based on a multidisciplinary perspective. The current need for reliance on expert opinion illustrates a great need for further investigation into the management of this newly recognized contributor to residual cardiovascular risk, both in patients who are apparently well and those with established cardiovascular or malignant disease.

Putative Mechanisms Underlying Cardiovascular Disease Associated with Clonal Hematopoiesis of Indeterminate Potential

Characterized by the expansion of somatic mutations in the hematopoietic lineages of aging individuals, clonal hematopoiesis of indeterminate potential (CHIP) is a common condition that increases the risk of developing hematological malignancies and cardiovascular disease (CVD). The presence of CHIP-associated mutations in hematopoietic stem and progenitor cells (HSPCs) suggests that these mutations may alter the functions of the diverse hematopoietic lineages, many of which influence the pathogenesis of CVD. Inflammation may be a potential pathogenic mechanism, linking both CVD and hematological malignancy. However, it remains unknown whether CHIP-associated CVD and hematological malignancy are features of a common disease spectrum. The contributions of CHIP-associated mutations to both CVD and hematological malignancy underscore the importance of stem cell biology in pathogenesis and treatment. This review discusses possible mechanisms underlying the contributions of multiple hematopoietic lineages to CHIP-associated CVD and the putative pathogenic links between CHIP-associated CVD and hematological malignancy.

Clonal Hematopoiesis and Mutations of Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are associated with the fewest number of mutations among known cancers. The mutations propelling these malignancies are phenotypic drivers providing an important implement for diagnosis, treatment response monitoring, and gaining insight into the disease biology. The phenotypic drivers of Philadelphia chromosome negative MPN include mutations in JAK2, CALR, and MPL. The most prevalent driver mutation JAK2V617F can cause disease entities such as essential thrombocythemia (ET) and polycythemia vera (PV). The divergent development is considered to be influenced by the acquisition order of the phenotypic driver mutation relative to other MPN-related mutations such as TET2 and DNMT3A. Advances in molecular biology revealed emergence of clonal hematopoiesis (CH) to be inevitable with aging and associated with risk factors beyond the development of blood cancers. In addition to its well-established role in thrombosis, the JAK2V617F mutation is particularly connected to the risk of developing cardiovascular disease (CVD), a pertinent issue, as deep molecular screening has revealed the prevalence of the mutation to be much higher in the background population than previously anticipated. Recent findings suggest a profound under-diagnosis of MPNs, and considering the impact of CVD on society, this calls for early detection of phenotypic driver mutations and clinical intervention.

Clinico-Biological Features and Clonal Hematopoiesis in Patients with Severe COVID-19

Advanced age or preexisting comorbidities have been characterized as risk factors for severe coronavirus disease 2019 (COVID-19) cases requiring hospitalization and intensive care. In recent years, clonal hematopoiesis (CH) of indeterminate potential (CHIP) has emerged as a risk factor for chronic inflammatory background and subsequent aging-associated diseases. The purpose of this study was to identify biological factors (particularly leukocyte subtypes and inflammatory markers) associated with a risk of clinical deterioration (i.e., orotracheal intubation (OTI)) and to determine whether CH was likely to influence clinical and biological behavior in patients with severe COVID-19 requiring hospitalization. Here, we describe clinical and biological features, including the screening of CHIP mutants in a well-annotated cohort of 122 hospitalized patients with a laboratory-confirmed diagnosis of COVID-19 (55% requiring OTI). We showed that elevated white blood cell counts, especially neutrophils and high C-reactive protein (CRP) levels at admission, were associated with an increased requirement of OTI. We noticed a high prevalence of CH (25%, 38%, 56%, and 82% of patients aged <60 years, 60–70 years, 70–80 years, and >80 years) compared to a retrospective cohort of patients free of hematological malignancy explored with the same pipelines (10%, 21%, 37%, and 44%). However, the existence of CH did not significantly impact clinical outcome, including OTI or death, and did not correlate with other laboratory findings.

Cardiac dysfunction in cancer patients: beyond direct cardiomyocyte damage of anticancer drugs: novel cardio-oncology insights from the joint 2019 meeting of the ESC Working Groups of Myocardial Function and Cellular Biology of the Heart

In western countries, cardiovascular (CV) disease and cancer are the leading causes of death in the ageing population. Recent epidemiological data suggest that cancer is more frequent in patients with prevalent or incident CV disease, in particular, heart failure (HF). Indeed, there is a tight link in terms of shared risk factors and mechanisms between HF and cancer. HF induced by anticancer therapies has been extensively studied, primarily focusing on the toxic effects that anti-tumour treatments exert on cardiomyocytes. In this Cardio-Oncology update, members of the ESC Working Groups of Myocardial Function and Cellular Biology of the Heart discuss novel evidence interconnecting cardiac dysfunction and cancer via pathways in which cardiomyocytes may be involved but are not central. In particular, the multiple roles of cardiac stromal cells (endothelial cells and fibroblasts) and inflammatory cells are highlighted. Also, the gut microbiota is depicted as a new player at the crossroads between HF and cancer. Finally, the role of non-coding RNAs in Cardio-Oncology is also addressed. All these insights are expected to fuel additional research efforts in the field of Cardio-Oncology.

Clonal Hematopoiesis of Indeterminate Potential and Cardiovascular Disease

PURPOSE OF REVIEW

The purpose of this review article is to summarize the preclinical and clinical evidence supporting the notion of clonal hematopoiesis of indeterminate potential (CHIP), highlight current knowledge gap, and provide future directions.

RECENT FINDINGS

Epidemiological studies show that advanced age is a major risk factor for the development of cardiovascular disease (CVD) and cancer, the two leading causes of morbidity and mortality worldwide. While the negative effect of aging on CVD is a reflection of cumulative exposure to various established traditional CVD risk factors, genetic sequencing of whole blood-derived DNA recently revealed that clonal mutations in myeloid stem cells are associated with higher risks of cardiovascular events and hematopoietic malignancies. The clinical repercussions of this biological state, termed CHIP, are increasingly appreciated. Historically, CHIP has been associated with an increased risk of hematological malignancies. However, new research is showing that CHIP is also associated with an increased risk of several cardiac-related conditions, including atherosclerosis, myocardial infarction, aortic valve stenosis, and congestive heart failure. CHIP is increasingly being appreciated worldwide as a CVD risk factor, and further studies are needed to better understand the complex relationship between these two disorders.

Bone marrow contribution to the heart from development to adulthood

Cardiac chamber walls contain large numbers of non-contractile interstitial cells, including fibroblasts, endothelial cells, pericytes and significant populations of blood lineage-derived cells. Blood cells first colonize heart tissues a few days before birth, although their recruitment from the bloodstream to the cardiac interstitium is continuous and extends throughout adult life. The bone marrow, as the major hematopoietic site of adult individuals, is in charge of renewing all circulating cell types, and it therefore plays a pivotal role in the incorporation of blood cells to the heart. Bone marrow-derived cells are instrumental to tissue homeostasis in the steady-state heart, and are major effectors in cardiac disease progression. This review will provide a comprehensive approach to bone marrow-derived blood cell functions in the heart, and discuss aspects related to hot topics in the cardiovascular field like cell-based heart regeneration strategies.

The role of molecular mechanism of Ten-Eleven Translocation2 (TET2) family proteins in pathogenesis of cardiovascular diseases (CVDs)

Cardiovascular disease (CVD) is one of the most common diseases worldwide. The underlying pathogenesis of the disease has not yet been determined, but many factors have been identified. Tet methylcytosine dioxygenase 2 (TET2) is one of the epigenetic factors involved in regulating many genes. Therefore, based on the studies shown, this factor plays an important role in preventing the occurrence of CVD. TET2 has been shown to increase angiogenesis by expressing Robo4. It also increases the activity of Matrix metalloproteinases (MMPs) and stimulates the secretion of Vascular endothelial growth factor angiogenesis. On the other hand, it has been shown that TET2 regulates the expression of several genes and the development of the heart during the embryonic period due to its oxygenating role. TET2 has been shown to regulates the expression of the genes such as Ying Yang1 (YY1), Sox9b, Inhbaa and many other genes that ultimately lead to the differentiation of cardiomyocytes. On the other hand, it has been shown that some Long non coding RNA and MicroRNAs reduce TET2 expression and CVD. Finally, it is concluded that inducing TET2 expression can be a good therapeutic strategy to prevent or improve CVD.

Clonal haematopoiesis and COVID-19: A possible deadly liaison

We provide evidence for a linear correlation between the frequency of clonal haematopoiesis and COVID‐19 mortality rate. We discuss the mechanistic explanations for this association mediated by a pathological inflammatory response. Our hypothesis can be tested in COVID‐19‐infected patients and eventually lead to new approaches to risk stratification and therapy.

Clonality in haematopoietic stem cell ageing

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Somatic driver mutations lead to clonal haematopoiesis of indeterminate potential (CHIP) in aged haematopoietic stem cells.

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CHIP is associated with a variety of age-related multimorbidities.

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How environmental and cell-intrinsic factors contribute to CHIP and development of multimorbidities is poorly understood.

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Increased inflammatory signalling with age might be one mechanism driving age-related disease and favouring outgrowth of HSCs carrying specific driver mutations.

Clonal haematopoiesis of indeterminate potential (CHIP) is widespread in the elderly. CHIP is driven by somatic mutations in leukaemia driver genes, such as Janus Kinase 2 (JAK2), Tet methylcytosine dioxygenase 2 (TET2), ASXL Transcriptional Regulator 1 (ASXL1) and DNA (cytosine-5)-methyltransferase 3A (DNMT3A), leading to reduced diversity of the blood pool. CHIP carries an increased risk for leukaemia and cardiovascular disease. Apart from mutations driving CHIP, environmental factors such as chemokines and cytokines have been implicated in age-dependent multimorbidities associated with CHIP. However, the mechanism of CHIP onset and the relationship with environmental and cell-intrinsic factors remain poorly understood. Here we contrast cell-intrinsic and environmental factors involved in CHIP development and disease propagation.

Anti-inflammatory effects of non-statin low-density lipoprotein cholesterol-lowering drugs: an unused potential?

Objectives. Inflammatory responses are closely knit with low-density lipoprotein (LDL)-cholesterol in driving atherosclerosis. Even if LDL-cholesterol is causative to atherosclerotic diseases and LDL-cholesterol lowering reduces hard clinical endpoints, there is a residual risk for clinical events, possibly driven by inflammatory processes, in accordance with its role in autoimmune diseases. Design. As LDL-cholesterol treatment targets are reduced, the use of non-statin lipid-lowering drugs will probably increase. Atherosclerotic plaques evolve through lipid infiltration and modification in the intima, furthermore infiltration of cells including monocytes, macrophages, T-lymphocytes and neutrophils initiating inflammatory signaling. Here we briefly review inflammation in atherosclerosis and the effects of the non-statin lipid-lowering drugs on inflammation. The review is limited to the most common non-statin lipid lowering drugs, i.e. proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors, bile acid sequestrants (BAS) and cholesterol absorption inhibitors. Results. PCSK9 inhibition is mostly studied together with statins and is associated with a reduction of pro-inflammatory cytokines. Furthermore, PCSK9 inhibitors seem to have an effect on monocyte migration trough CCR2. They also have an interaction with sirtuins, possibly offering a therapeutic target. BAS have several interesting effects on inflammation, including reduction of pro-inflammatory cytokines and a reduction of the number of infiltrating macrophages, however there are relatively few reports considering that these drugs have been on the market for decades. Ezetimibe also has effects on inflammation including reduction of pro-inflammatory cytokines and adhesion molecules, however these effects are usually accomplished in tandem with statins. Conclusion. This topic adds an interesting piece to the puzzle of atherosclerosis, indicating that PCSK9 inhibition, BAS and ezetimibe all affect thromboinflammation.

Clonal Hematopoiesis of Indeterminate Potential Reshapes Age-Related CVD: JACC Review Topic of the Week

The incidence of cardiovascular diseases increases with age and is also correlated with increased inflammatory burden. Recently, human genetics provided a new paradigm linking aging, inflammation, and atherosclerotic cardiovascular disease (ASCVD). Next-generation genetic sequencing of whole blood-derived DNA in humans showed that clonal expansion of hematopoietic cells with somatic mutations in leukemogenic genes was associated with age and correlated with increased mortality. This phenomenon, termed clonal hematopoiesis of indeterminate potential (CHIP), was associated with hematologic malignancy as well as ASCVD independently of age and other traditional risk factors. Because the implication of CHIP with ASCVD, genetic loss-of-function studies of Tet2 and Dnmt3a in murine models have supported a mechanistic role for CHIP in promoting vascular disease. Despite the potential contribution of CHIP to myriad cardiovascular and aging-related diseases, the epidemiology and biology surrounding this phenomenon remains incompletely appreciated and understood, especially as applied to clinical practice and prognostication. Here, the authors review this emerging key risk factor, defining its discovery, relationship to cardiovascular diseases, preclinical evidence for causality, and implications for risk prediction and mitigation.

Clonal hematopoiesis in human aging and disease

As people age, their tissues accumulate an increasing number of somatic mutations. Although most of these mutations are of little or no functional consequence, a mutation may arise that confers a fitness advantage on a cell. When this process happens in the hematopoietic system, a substantial proportion of circulating blood cells may derive from a single mutated stem cell. This outgrowth, called "clonal hematopoiesis," is highly prevalent in the elderly population. Here we discuss recent advances in our knowledge of clonal hematopoiesis, its relationship to malignancies, its link to nonmalignant diseases of aging, and its potential impact on immune function. Clonal hematopoiesis provides a glimpse into the process of mutation and selection that likely occurs in all somatic tissues.

Comorbidities cluster with impaired functional capacities and depressive mood and predict adverse outcome in older patients with hematological malignancies

This study evaluates prevalence of comorbidities and their association with impairments in older patients with hematological malignancies at initial diagnosis (n = 209). At least one comorbidity was present in 62.2%, 68.5% and 93.8% as defined by CCI (Charlson Comorbidity Index), Cumulative Illness Rating Scale-Geriatric (CIRS-G) and HCT-Comorbidity Index, respectively. Severe comorbidities (CIRS-G Grade 3/4) were present in 57.9%. The mean number of affected organ systems was 3.6 (CIRS-G categories), with diabetes (18.2%), congestive heart failure and prior solid tumors (each 17.7%) detected most frequently. Comorbidities were significantly correlated with reduced functional and objective physical capacities, impaired performance and depressive mood. Both CCI and CIRS-G were found to be prognostic factors for OS (p < 0.05). CCI scoring of comorbidities, diagnosis MDS/AML and a body mass index <23kg/m² were independent adverse predictors for OS. This first prospective analysis reveals a prognostic significance of comorbidities. Clustering of comorbidities with impairments suggests common mechanisms.

Tet2-mediated clonal hematopoiesis in nonconditioned mice accelerates age-associated cardiac dysfunction

Clonal hematopoiesis of indeterminate potential is prevalent in elderly individuals and associated with increased risks of all-cause mortality and cardiovascular disease. However, mouse models to study the dynamics of clonal hematopoiesis and its consequences on the cardiovascular system under homeostatic conditions are lacking. We developed a model of clonal hematopoiesis using adoptive transfer of unfractionated ten-eleven translocation 2-mutant (Tet2-mutant) bone marrow cells into nonirradiated mice. Consistent with age-related clonal hematopoiesis observed in humans, these mice displayed a progressive expansion of Tet2-deficient cells in multiple hematopoietic stem and progenitor cell fractions and blood cell lineages. The expansion of the Tet2-mutant fraction was also observed in bone marrow-derived CCR2+ myeloid cell populations within the heart, but there was a negligible impact on the yolk sac-derived CCR2- cardiac-resident macrophage population. Transcriptome profiling revealed an enhanced inflammatory signature in the donor-derived macrophages isolated from the heart. Mice receiving Tet2-deficient bone marrow cells spontaneously developed age-related cardiac dysfunction characterized by greater hypertrophy and fibrosis. Altogether, we show that Tet2-mediated hematopoiesis contributes to cardiac dysfunction in a nonconditioned setting that faithfully models human clonal hematopoiesis in unperturbed bone marrow. Our data support clinical findings that clonal hematopoiesis per se may contribute to diminished health span.

Hemoglobin levels and coronary heart disease risk by age, race, and sex in the reasons for geographic and racial differences in stroke study (REGARDS)

Higher and lower hemoglobin concentrations are associated with coronary heart disease (CHD), but whether this risk is consistent across age, sex, and race is unclear. The Reasons for Geographic And Racial Differences in Stroke (REGARDS) study is an observational cohort study of 30 239 black, and white, adults aged 45 and older recruited 2003-7. Participants were included if they had hemoglobin measures, were CHD-free at baseline, and had all baseline variables. The primary outcome was incident CHD. Multivariable Cox proportional hazards models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) for incident CHD by hemoglobin concentration. This was expressed as a continuous variable and divided into age-, sex-, and race-specific quintiles. The 16 332 participants were included, contributing 114 362 person-years of follow-up and 915 incident CHD events. The mean age was 63 years, 35% were male, 41% were black, and the mean baseline hemoglobin was 13.6 g/dL (SD 1.4). A significant non-linear association between hemoglobin and CHD was identified (P < .001). This association differed significantly by race (P = .025) but not by sex or age. In whites, the risk for incident CHD was higher in the lowest (HR 2.28, 95% CI 1.61, 3.33) and highest (HR 1.94, 95% CI 1.35, 2.79) hemoglobin quintiles relative to the third quintile. For blacks, only those in the lowest hemoglobin quintile had an increased risk for incident CHD events (HR 1.70, 95% CI 1.20, 2.41). Hemoglobin is an independent risk factor for CHD in whites and blacks but with different hemoglobin concentrations conferring different risks.

Clonal Hematopoiesis: A New Step Linking Inflammation to Heart Failure

Heart failure is a common disease with poor prognosis that is associated with cardiac immune cell infiltration and dysregulated cytokine expression. Recently, the clonal expansion of hematopoietic cells with acquired (i.e., nonheritable) DNA mutations, a process referred to as clonal hematopoiesis, has been reported to be associated with cardiovascular diseases including heart failure. Mechanistic studies have shown that leukocytes that harbor these somatic mutations display altered inflammatory characteristics that worsen the phenotypes associated with heart failure in experimental models. In this review, we summarize recent epidemiological and experimental evidence that support the hypothesis that clonal hematopoiesis-mediated immune cell dysfunction contributes to heart failure and cardiovascular disease in general.

A new opening on aortic stenosis: predicting prognosis with clonal haematopoiesis

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Clonal hematopoiesis driven by somatic mutations: A new player in atherosclerotic cardiovascular disease

The accumulation of acquired mutations is an inevitable consequence of the aging process, but its pathophysiological relevance has remained largely unexplored beyond cancer. Most of these mutations have little or no functional consequences, but in a few rare instances, a mutation may arise that confers a competitive advantage to a stem cell, leading to its clonal expansion. When such a mutation occurs in hematopoietic stem cells, it leads to a situation of clonal hematopoiesis, which has the potential to affect multiple tissues beyond the bone marrow, as the clonal expansion of the mutant stem cell is extended to circulating blood cells and tissue-infiltrating immune cells. Recent genomics and experimental studies have provided support to the notion that this somatic mutation-driven clonal hematopoiesis contributes to vascular inflammation and the development of atherosclerosis and related cardiovascular and cerebrovascular ischemic events. Here, we review our current understanding of this emerging cardiovascular risk modifier and the mechanisms underlying its connection to atherosclerosis development.