Clonal haematopoiesis across the age spectrum of vasculitis patients with Takayasu's arteritis, ANCA-associated vasculitis and giant cell arteritis

OBJECTIVES

Ageing and inflammation are associated with clonal haematopoiesis (CH), the emergence of somatic mutations in haematopoietic cells. This study details CH in patients with systemic vasculitis in association with clinical, haematological and immunological parameters.

METHODS

Patients with three forms of vasculitis were screened for CH in peripheral blood by error-corrected sequencing. Relative contributions of age and vasculitis on CH prevalence were calculated using multivariable logistic regression. Clonal hierarchies were assessed by proteogenomic single-cell DNA sequencing, and functional experiments were performed in association with CH status.

RESULTS

Patients with Takayasu's arteritis (TAK; n=70; mean age=33.2 years), antineutrophil cytoplasmic antibody-associated vasculitis (AAV; n=47; mean age=55.3 years) and giant cell arteritis (GCA; n=59; mean age=71.2 years) were studied. CH, most commonly in DNMT3A and TET2, was detected in 34% (60/176) of patients versus 18% (28/151) of age-matched controls (p<0.01). Prevalence of CH was independently associated with age (standardised B=0.96, p<0.01) and vasculitis (standardised B=0.46, p<0.01), occurring in 61%, 32% and 13% of patients with GCA, AAV and TAK, respectively. Both branched and linear clonal trajectories showed myeloid-lineage bias, and CH was associated with markers of cellular activation. In GCA, mutations were detected in temporal artery biopsies, and clinical relapse correlated with CH in a dose-dependent relationship with clone size.

CONCLUSIONS

Age was more strongly associated with CH prevalence than inflammation in systemic vasculitis. Clonal profile was dominated by DNMT3A mutations which were associated with relapse in GCA. CH is not likely a primary causal factor in systemic vasculitis but may contribute to inflammation.

Clonal hematopoiesis and autoimmunity

Clonal hematopoiesis (CH) has been associated with aging, occurring in about 10% of individuals aged >70 years, and immune dysfunction. Aged hematopoietic stem and progenitor cells exhibit pathological changes in immune function and activation of inflammatory pathways. CH clones commonly harbor a loss of function mutation in DNMT3A or TET2, which causes increased expression of inflammatory signaling genes, a proposed mechanism connected to CH and the development of age-related diseases. Additionally, inflammation may stress the hematopoietic compartment, driving the expansion of mutant clones. While the epidemiologic overlap between CH, hematologic malignancies, and atherosclerotic cardiovascular diseases has been reported, the mechanisms linking these concepts are largely unknown and merit much further investigation. Here, we review studies highlighting the interplay between CH, inflamm-aging, the immune system, and the prevalence of CH in autoimmune diseases.

Molecular and clinical aspects relevant for counseling individuals with clonal hematopoiesis of indeterminate potential

Clonal hematopoiesis of indeterminate potential (CHIP) has fascinated the medical community for some time. Discovered about a decade ago, this phenomenon links age-related alterations in hematopoiesis not only to the later development of hematological malignancies but also to an increased risk of early-onset cardiovascular disease and some other disorders. CHIP is detected in the blood and is characterized by clonally expanded somatic mutations in cancer-associated genes, predisposing to the development of hematologic neoplasms such as MDS and AML. CHIP-associated mutations often involve DNA damage repair genes and are frequently observed following prior cytotoxic cancer therapy. Genetic predisposition seems to be a contributing factor. It came as a surprise that CHIP significantly elevates the risk of myocardial infarction and stroke, and also contributes to heart failure and pulmonary hypertension. Meanwhile, evidence of mutant clonal macrophages in vessel walls and organ parenchyma helps to explain the pathophysiology. Besides aging, there are some risk factors promoting the appearance of CHIP, such as smoking, chronic inflammation, chronic sleep deprivation, and high birth weight. This article describes fundamental aspects of CHIP and explains its association with hematologic malignancies, cardiovascular disorders, and other medical conditions, while also exploring potential progress in the clinical management of affected individuals. While it is important to diagnose conditions that can lead to adverse, but potentially preventable, effects, it is equally important not to stress patients by confronting them with disconcerting findings that cannot be remedied. Individuals with diagnosed or suspected CHIP should receive counseling in a specialized outpatient clinic, where professionals from relevant medical specialties may help them to avoid the development of CHIP-related health problems. Unfortunately, useful treatments and clinical guidelines for managing CHIP are still largely lacking. However, there are some promising approaches regarding the management of cardiovascular disease risk. In the future, strategies aimed at restoration of gene function or inhibition of inflammatory mediators may become an option.

The Role of Clonal Hematopoiesis of Indeterminant Potential and DNA (Cytosine-5)-Methyltransferase Dysregulation in Pulmonary Arterial Hypertension and Other Cardiovascular Diseases

DNA methylation is an epigenetic mechanism that regulates gene expression without altering gene sequences in health and disease. DNA methyltransferases (DNMTs) are enzymes responsible for DNA methylation, and their dysregulation is both a pathogenic mechanism of disease and a therapeutic target. DNMTs change gene expression by methylating CpG islands within exonic and intergenic DNA regions, which typically reduces gene transcription. Initially, mutations in the DNMT genes and pathologic DNMT protein expression were found to cause hematologic diseases, like myeloproliferative disease and acute myeloid leukemia, but recently they have been shown to promote cardiovascular diseases, including coronary artery disease and pulmonary hypertension. We reviewed the regulation and functions of DNMTs, with an emphasis on somatic mutations in DNMT3A, a common cause of clonal hematopoiesis of indeterminant potential (CHIP) that may also be involved in the development of pulmonary arterial hypertension (PAH). Accumulation of somatic mutations in DNMT3A and other CHIP genes in hematopoietic cells and cardiovascular tissues creates an inflammatory environment that promotes cardiopulmonary diseases, even in the absence of hematologic disease. This review summarized the current understanding of the roles of DNMTs in maintenance and de novo methylation that contribute to the pathogenesis of cardiovascular diseases, including PAH.

Philadelphia chromosome-negative myeloproliferative chronic neoplasms: is clonal hematopoiesis the main determinant of autoimmune and cardio-vascular manifestations?

In this article, we reviewed the possible mechanisms linking the clonal hematopoiesis of indeterminate potential (CHIP) to chronic myeloproliferative neoplasms (MPNs), autoimmune diseases (ADs), and cardiovascular diseases (CADs). CHIP is characterized by the presence of clonal mutations with an allelic frequency >2% in the peripheral blood without dysplasia, overt hematological neoplasms, or abnormalities in blood cell count. The prevalence may reach 20% of elderly healthy individuals and is considered a risk factor for myelodysplastic neoplasms and acute leukemia. In MPNs, CHIP is often associated with mutations such as JAK2V617F or DNMT3A, TET2, or ASXL1, which exhibit a 12.1- and 1.7-2-fold increase in CADs. Specifically, JAK2-mutated cells produce excessive cytokines and reactive oxygen species, leading to proinflammatory modifications in the bone marrow microenvironment. Consequently, the likelihood of experiencing thrombosis is influenced by the variant allele frequency (VAF) of the JAK2V617F mutation, which also appears to be correlated with anti-endothelial cell antibodies that sustain thrombosis. However, DNMT3A mutations induce pro-inflammatory T-cell polarization and activate the inflammasome complex, while TET2 downregulation leads to endothelial cell autophagy and inflammatory factor upregulation. As a result, in patients with TET2 and DNMT3A-related CHIP, the inflammasome hyperactivation represents a potential cause of CADs. CHIP also occurs in patients with large and small vessel vasculitis, while ADs are more frequently associated with MPNs. In these diseases, monocytes and neutrophils play a key role in the formation of neutrophil extracellular trap (NET) as well as anti-endothelial cell antibodies, resulting in a final procoagulant effect. ADs, such as systemic lupus erythematosus, psoriasis, and arthritis, are also characterized by an overexpression of the Rho-associated coiled-coil containing protein kinase 2 (ROCK2), a serine/threonine kinase that can hyperactivate the JAK-STAT pathway. Interestingly, hyperactivation of ROCK2 has also been observed in myeloid malignancies, where it promotes the growth and survival of leukemic cells. In summary, the presence of CHIP, with or without neoplasia, can be associated with autoimmune manifestations and thrombosis. In the presence of these manifestations, it is necessary to consider a "disease-modifying therapy" that may either reduce the clonal burden or inhibit the clonally activated JAK pathway.

Aging, Inflammation, and Comorbidity in Cancers-A General In Silico Study Exemplified by Myeloproliferative Malignancies

(1) Background: We consider dormant, pre-cancerous states prevented from developing into cancer by the immune system. Inflammatory morbidity may compromise the immune system and cause the pre-cancer to escape into an actual cancerous development. The immune deficiency described is general, but the results may vary across specific cancers due to different variances (2) Methods: We formulate a general conceptual model to perform rigorous in silico consequence analysis. Relevant existing data for myeloproliferative malignancies from the literature are used to calibrate the in silico computations. (3) Results and conclusions: The hypothesis suggests a common physiological origin for many clinical and epidemiological observations in relation to cancers in general. Examples are the observed age-dependent prevalence for hematopoietic cancers, a general mechanism-based explanation for why the risk of cancer increases with age, and how somatic mutations in general, and specifically seen in screenings of citizens, sometimes are non-increased or even decrease when followed over time. The conceptual model is used to characterize different groups of citizens and patients, describing different treatment responses and development scenarios.

An update on VEXAS syndrome

INTRODUCTION

VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is a recently described, late-onset, acquired autoinflammatory disorder caused by mutations in the UBA1 gene. The various clinical manifestations of VEXAS broadly divided into inflammatory or haematological. VEXAS defines a new disease category - the hematoinflammatory disorders triggered by somatic mutations restricted to blood but causing systemic inflammation with multi-organ involvement and associated with aberrant bone marrow status. VEXAS causes significant morbidity and reduced life expectancy, but the optimum standard of care remains undefined.

AREAS COVERED

This review describes the discovery of VEXAS, relevant genetic causes and immunopathology of the disease. A detailed account of its various clinical manifestations and disease mimics is provided. Current treatment and management options are discussed.

EXPERT OPINION

New rare variants in UBA1 and VEXAS-like UBA1 negative cases are reported. Consensus diagnostic criteria might be required to define VEXAS and its related disorders. Investigation of sporadic, VEXAS-like cases will require the application of deep sequencing using DNA obtained from various cellular or tissue locations. Prospective studies are needed to define the optimal supportive and treatment options for patients with varying disease severity and prognosis. VEXAS-specific hematopoietic stem cell transplant selection criteria also require development.

Clonal hematopoiesis of indeterminate potential and cardiovascular disease

Age is the most important risk factor for cardiovascular disease and appears to be more than a marker of cumulative exposure to other risk factors such as dyslipidemia and hypertension. With aging, genetic mutations occur that are not present in our germline DNA, observed as somatic mosaicism. Hematopoietic stem cells have an increased chance of developing mosaicism because they are highly proliferative, and mutations with survival benefits can establish clonal populations. Age-related clonal hematopoiesis resulting from somatic mutations was first described ∼25 years ago. The subset of clonal hematopoiesis in which a driver mutation with variant allele frequency of at least 2% occurs in a gene implicated in hematologic malignancies but in the absence of known hematologic malignancy or other clonal disorder is termed clonal hematopoiesis of indeterminate potential (CHIP). Large-scale exome-sequencing projects have recently enabled the study of CHIP frequency, gene-specific analyses, and longitudinal clinical consequences of CHIP, including an observed increased risk for cardiovascular disease. Animal models provide insight into the mechanisms by which CHIP increases cardiovascular disease risk, and combined animal, clinical, and epidemiological data suggest therapeutic implications for CHIP in cardiovascular disease prevention.

Clinical Significance of Clonal Hematopoiesis of Indeterminate Potential in Hematology and Cardiovascular Disease

Liquid profiling uses circulating tumor DNA (ctDNA) for minimal invasive tumor mutational profiling from peripheral blood. The presence of somatic mutations in peripheral blood cells without further evidence of a hematologic neoplasm defines clonal hematopoiesis of indeterminate potential (CHIP). CHIP-mutations can be found in the cell-free DNA (cfDNA) of plasma, are a potential cause of false positive results in liquid profiling, and thus limit its usage in screening settings. Various strategies are in place to mitigate the effect of CHIP on the performance of ctDNA assays, but the detection of CHIP also represents a clinically significant incidental finding. The sequelae of CHIP comprise the risk of progression to a hematologic neoplasm including therapy-related myeloid neoplasms. While the hematological risk increases with the co-occurrence of unexplained blood count abnormalities, a number of non-hematologic diseases have independently been associated with CHIP. In particular, CHIP represents a major risk factor for cardiovascular disease such as atherosclerosis or heart failure. The management of CHIP requires an interdisciplinary setting and represents a new topic in the field of cardio-oncology. In the future, the information on CHIP may be taken into account for personalized therapy of cancer patients.

Myelodysplastic syndrome and autoimmune disorders: two sides of the same coin?

Systemic inflammatory and autoimmune diseases and myelodysplastic syndromes have been linked in individual patients and in larger case series for at least 25 years. These associations frequently include thyroid disease, neutrophilic dermatoses, polyarthritis, connective tissue diseases, vasculitis, and autoimmune cytopenias. Studies have found that autoimmune disease (or its therapy) is a risk factor for the development of myelodysplastic syndromes, but such syndromes might also be an instigator of autoimmune disease. Epidemiological studies examining disease risk in myelodysplastic syndromes with and without comorbid autoimmune illness have reached mixed conclusions. The pathophysiology of myelodysplastic syndromes is tightly linked to excessive inflammatory activity in the bone marrow microenvironment, which could promote systemic inflammatory and autoimmune diseases directly or by stimulation of the adaptive immune response. Alternatively, autoimmune diseases could promote clonal evolution and disordered bone marrow growth, promoting the development of myeloid malignancy. Additionally, therapy-related myeloid neoplasms-including myelodysplastic syndromes-have been diagnosed after treatment of autoimmune diseases with immunosuppressant therapies. These associations raise the following question: are myelodysplastic syndromes and systemic inflammatory and autoimmune diseases two sides of the same coin-that is, do they share an underlying disease state that can manifest as a myeloid neoplasm, an autoinflammatory illness, or both? VEXAS syndrome, which was first reported in 2020, is caused by a mutation that affects myeloid-restricted cells and manifests with both myelodysplasia and autoinflammation, and could give insight into this biological possibility. We note that systemic inflammatory and autoimmune diseases are often steroid-dependent; however, studies have also evaluated the roles of other immunomodulating therapies. In this Viewpoint, we critically appraise and review the literature on the epidemiology, pathophysiology, and management of systemic inflammatory and autoimmune diseases that are associated with myelodysplastic syndromes and related diseases.

Advances in understanding the molecular basis of clonal hematopoiesis

Hematopoietic stem cells (HSCs) are polyfunctional, regenerating all blood cells via hematopoiesis throughout life. Clonal hematopoiesis (CH) is said to occur when a substantial proportion of mature blood cells is derived from a single dominant HSC lineage, usually because these HSCs have somatic mutations that confer a fitness and expansion advantage. CH strongly associates with aging and enrichment in some diseases irrespective of age, emerging as an independent causal risk factor for hematologic malignancies, cardiovascular disease, adverse disease outcomes, and all-cause mortality. Defining the molecular mechanisms underlying CH will thus provide a framework to develop interventions for healthy aging and disease treatment. Here, we review the most recent advances in understanding the molecular basis of CH in health and disease.

Clonal hematopoiesis of indeterminate potential and cardiovascular events in systemic lupus erythematosus (HEMATOPLUS study)

OBJECTIVE

The detection of somatic mutations in genes of myeloid cells in asymptomatic patients - defining clonal hematopoiesis of indeterminate potential (CHIP) - predisposes to cardiovascular events (CVE) in the general population. We aimed to determine whether CHIP was associated with CVE in SLE patients.

METHODS

The study is an ancillary study of the randomized, double-blind, placebo-controlled, multicenter trial PLUS study conducted from June 2007 through August 2010 at 37 centers in France involving 573 SLE patients. The search for somatic mutations by high-throughput sequencing of 53 genes involved in clonal hematopoiesis was performed on genomic DNA collected at PLUS inclusion. The CHIP prevalence was assessed in SLE and in a retrospective cohort of 479 patients free of hematological malignancy. The primary outcome was the incident CVE in SLE.

RESULTS

Screening for CHIP was performed in 438 SLE patients (38 [29-47] years, 91·8% female). Overall, 63 somatic mutations were identified in 47 patients defining a CHIP prevalence of 10·7% in SLE. Most SLE patients (78·7%) carried a single mutation. Most variants (62·5%) were located in the DNMT3A gene. CHIP was associated with age, age at SLE diagnosis and a lower frequency of antiphospholipid antibodies. CHIP occurred more than 20-years earlier (p < 0·00001) in SLE than in controls. The detection of CHIP at inclusion was not associated with the occurrence of CVE during follow up (HR = 0·42 (0·06 - 3·21), p = 0·406).

CONCLUSION

The prevalence of CHIP is high in SLE with respect to age but was not associated with incident CVE.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, https://clinicaltrials.gov, NCT05146414.

Somatic Mutations in Rheumatologic Diseases: VEXAS Syndrome and Beyond

Discovery of the VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome demonstrates that somatic mutations in hematologic precursor cells can cause adult-onset, complex inflammatory disease. Unlike germline mutations, somatic mutations occur throughout the lifespan, are restricted to specific tissue types, and may play a causal role in non-heritable rheumatologic diseases, especially conditions that start in later life. Improvements in sequencing technology have enabled researchers and clinicians to detect somatic mutations in various tissue types, especially blood. Understanding the relationships between cell-specific acquired mutations and inflammation is likely to yield key insights into causal factors that underlie many rheumatologic diseases. The objective of this review is to detail how somatic mutations are likely to be relevant to clinicians who care for patients with rheumatologic diseases, with particular focus on the pathogenetic mechanisms of the VEXAS syndrome.

Clonal hematopoiesis of indeterminate potential (CHIP): Linking somatic mutations, hematopoiesis, chronic inflammation and cardiovascular disease

Clonal hematopoiesis of indeterminate potential (CHIP) is the presence of a clonally expanded hematopoietic stem cell caused by a leukemogenic mutation in individuals without evidence of hematologic malignancy, dysplasia, or cytopenia. CHIP is associated with a 0.5-1.0% risk per year of leukemia. Remarkably, it confers a two-fold increase in cardiovascular risk independent of traditional risk factors. Roughly 80% of patients with CHIP have mutations in epigenetic regulators DNMT3A, TET2, ASXL1, DNA damage repair genes PPM1D, TP53, the regulatory tyrosine kinase JAK2, or mRNA spliceosome components SF3B1, and SRSF2. CHIP is associated with a pro-inflammatory state that has been linked to coronary artery disease, myocardial infarction, and venous thromboembolic disease, as well as prognosis among those with aortic stenosis and heart failure. Heritable and acquired risk factors are associated with increased CHIP prevalence, including germline variation, age, unhealthy lifestyle behaviors (i.e. smoking, obesity), inflammatory conditions, premature menopause, HIV and exposure to cancer therapies. This review aims to summarize emerging research on CHIP, the mechanisms underlying its important role in propagating inflammation and accelerating cardiovascular disease, and new studies detailing the role of associated risk factors and co-morbidities that increase CHIP prevalence.

Inflammatory and Immune Disorders Associated with Myelodysplastic Syndromes

Systemic auto-inflammatory or autoimmune diseases (SIADs) develop in up to a quarter of patients with myelodysplastic syndromes (MDS) or chronic myelomonocytic leukemia (CMML). With or without the occurrence of SIADs, the distribution of MDS subtypes and the international or CMML-specific prognostic scoring systems have been similar between MDS/CMML patients. Moreover, various SIADs have been described in association with MDS, ranging from limited clinical manifestations to systemic diseases affecting multiple organs. Defined clinical entities including systemic vasculitis, connective tissue diseases, inflammatory arthritis and neutrophilic diseases are frequently reported; however, unclassified or isolated organ impairment can also be seen. Although the presence of SIADs does not impact the overall survival nor disease progression to acute myeloid leukemia, they can help with avoiding steroid dependence and make associated adverse events of immunosuppressive drugs challenging. While therapies using steroids and immunosuppressive treatment remain the backbone of first-line treatment, increasing evidence suggests that MDS specific therapy (hypomethylating agents) and sparing steroids may be effective in treating such complications based on their immunomodulatory effect. The aim of this review was to analyze the epidemiological, pathophysiological, clinical and therapeutic factors of systemic inflammatory and immune disorders associated with MDS.

Myeloproliferative neoplasms and clonal hematopoiesis in patients with giant cell arteritis: a case-control and exploratory study

OBJECTIVES

Giant cell arteritis (GCA) is a large vessel vasculitis for which triggering factors remain unknown. Clonal hematopoiesis (CH) was associated with atherosclerosis through the induction of inflammation in myeloid cells, and data suggest that CH expansion and inflammation may support each other to induce a proinflammatory loop. Our objective was to describe the impact of JAK2p.V617F-mutated myeloproliferative neoplasms (MPN) on GCA and to screen MPN-free patients for CH mutations.

METHODS

We performed a retrospective case-control study comparing characteristics of 21 GCA patients with MPN and 42 age and gender-matched GCA patients without MPN. Also, 18 GCA patients were screened for CH through Next Generation Sequencing.

RESULTS

The most frequent associated MPN was essential thrombocythemia (ET) (n = 11). Compared to controls, GCA patients with MPN had less frequent cephalic symptoms (71.4 vs. 97.6%, p = 0.004) and higher platelets count at baseline [485 (346-586) vs. 346 [IQR 296-418] x 109/L, p = 0.02). There was no difference between groups for other clinical features. Overall survival was significantly shorter in patients with MPN compared to controls [HR 8.2 (95% CI 1.2-56.6), p = 0.03]. Finally, screening for CH using NGS in 15 GCA patients without MPN revealed CH in 33%.

CONCLUSION

GCA patients with MPN display higher platelets count and shorter overall survival than controls. This association could not be fortuitous given the possible pathophysiological relationship between the two diseases. CH was found in one third of GCA patients, which may be higher than the expected prevalence for similar age, what should be confirmed in a larger cohort.

Fate of Hematopoiesis During Aging. What Do We Really Know, and What are its Implications?

There is an ongoing shift in demographics such that older persons will outnumber young persons in the coming years, and with it age-associated tissue attrition and increased diseases and disorders. There has been increased information on the association of the aging process with dysregulation of hematopoietic stem (HSC) and progenitor (HPC) cells, and hematopoiesis. This review provides an extensive up-to date summary on the literature of aged hematopoiesis and HSCs placed in context of potential artifacts of the collection and processing procedure, that may not be totally representative of the status of HSCs in their in vivo bone marrow microenvironment, and what the implications of this are for understanding aged hematopoiesis. This review covers a number of interactive areas, many of which have not been adequately explored. There are still many unknowns and mechanistic insights to be elucidated to better understand effects of aging on the hematopoietic system, efforts that will take multidisciplinary approaches, and that could lead to means to ameliorate at least some of the dysregulation of HSCs and HPCs associated with the aging process. Graphical Abstract.