A Novel Method for Acquired Sex Chromosome Mosaicism

The phenomenon of sex chromosome loss from hematopoietic cells is an emerging indicator of biological aging. While many methods to detect this loss have been developed, enhancing the field, these existing methods often suffer from being labor-intensive, expensive, and not sufficiently sensitive. To bridge this gap, a novel and more efficient technique is developed, named the SinChro assay. This method employs multiplexed single-cell droplet PCR, designed to detect cells with sex chromosome loss at single-cell resolution. Through the SinChro assay, the age-dependent increase in Y chromosome loss in male blood is successfully mapped. The age-dependent loss of the X chromosome in female blood is also identified, a finding that has been challenging with existing methods. The advent of the SinChro assay marks a significant breakthrough in the study of age-related sex mosaicism. Its utility extends beyond blood analysis, applicable to a variety of tissues, and it holds the potential to deepen the understanding of biological aging and related diseases.

Why Y matters? The implication of loss of Y chromosome in blood and cancer

Hematopoietic mosaic loss of Y chromosome (mLOY) has emerged as a potential male-specific accelerator of biological aging, increasing the risk of various age-related diseases, including cancer. Importantly, mLOY is not confined to hematopoietic cells; its presence has also been observed in nonhematological cancer cells, with the impact of this presence previously unknown. Recent studies have revealed that, whether occurring in leukocytes or cancer cells, mLOY plays a role in promoting the development of an immunosuppressive tumor microenvironment. This occurs through the modulation of tumor-infiltrating immune cells, ultimately enabling cancer cells to evade the vigilant immune system. In this review, we illuminate recent progress concerning the effects of hematopoietic mLOY and cancer mLOY on cancer progression. Examining cancer progression from the perspective of LOY adds a new layer to our understanding of cancer immunity, promising insights that hold the potential to identify innovative and potent immunotherapy targets for cancer.

Erratum: Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande [Phys. Rev. Lett. 130, 031802 (2023)]

This corrects the article DOI: 10.1103/PhysRevLett.130.031802.

Clonal Hematopoiesis in Clinical and Experimental Heart Failure With Preserved Ejection Fraction

BACKGROUND

Clonal hematopoiesis (CH), which results from an array of nonmalignant driver gene mutations, can lead to altered immune cell function and chronic disease, and has been associated with worse outcomes in patients with heart failure (HF) with reduced ejection fraction. However, the role of CH in the prognosis of HF with preserved ejection fraction (HFpEF) has been understudied. This study aimed to characterize CH in patients with HFpEF and elucidate its causal role in a murine model.

METHODS

Using a panel of 20 candidate CH driver genes and a variant allele fraction cutoff of 0.5%, ultradeep error-corrected sequencing identified CH in a cohort of 81 patients with HFpEF (mean age, 71±6 years; ejection fraction, 63±5%) and 36 controls without a diagnosis of HFpEF (mean age, 74±7 years; ejection fraction, 61.5±8%). CH was also evaluated in a replication cohort of 59 individuals with HFpEF.

RESULTS

Compared with controls, there was an enrichment of TET2-mediated CH in the HFpEF patient cohort (12% versus 0%, respectively; P=0.02). In the HFpEF cohort, patients with CH exhibited exacerbated diastolic dysfunction in terms of E/e' (14.9 versus 11.7, respectively; P=0.0096) and E/A (1.69 versus 0.89, respectively; P=0.0206) compared with those without CH. The association of CH with exacerbated diastolic dysfunction was corroborated in a validation cohort of individuals with HFpEF. In accordance, patients with HFpEF, an age ≥70 years, and CH exhibited worse prognosis in terms of 5-year cardiovascular-related hospitalization rate (hazard ratio, 5.06; P=0.042) compared with patients with HFpEF and an age ≥70 years without CH. To investigate the causal role of CH in HFpEF, nonconditioned mice underwent adoptive transfer with Tet2-wild-type or Tet2-deficient bone marrow and were subsequently subjected to a high-fat diet/L-NAME (Nω-nitro-l-arginine methyl ester) combination treatment to induce features of HFpEF. This model of Tet2-CH exacerbated cardiac hypertrophy by heart weight/tibia length and cardiomyocyte size, diastolic dysfunction by E/e' and left ventricular end-diastolic pressure, and cardiac fibrosis compared with the Tet2-wild-type condition.

CONCLUSIONS

CH is associated with worse heart function and prognosis in patients with HFpEF, and a murine experimental model of Tet2-mediated CH displays greater features of HFpEF.

Development of a Mouse Model of Hematopoietic Loss of Y Chromosome

This protocol describes the generation of chimeric mice in which the Y chromosome is deleted from a proportion of blood cells. This model recapitulates the phenomenon of hematopoietic mosaic loss of Y chromosome (mLOY), which is frequently observed in the blood of aged men. To construct mice with hematopoietic Y chromosome loss, lineage-negative cells are isolated from the bone marrow of ROSA26-Cas9 knock-in mice. These cells are transduced with a lentivirus vector encoding a guide RNA (gRNA) that targets multiple repeats of the Y chromosome centromere, effectively removing the Y chromosome. These cells are then transplanted into lethally irradiated wildtype C57BL6 mice. Control gRNAs are designed to target either no specific region or the fourth intron of Actin gene. Transduced cells are tracked by measuring the fraction of blood cells expressing the virally encoded reporter gene tRFP. This model represents a clinically relevant model of hematopoietic mosaic loss of Y chromosome, which can be used to study the impact of mLOY on various age-related diseases. Graphical overview.

Clonal hematopoiesis: the nonhereditary genetics of age-associated cardiovascular disease

PURPOSE OF REVIEW

Somatic mutations, described as noninherited changes in DNA that arise and are passed on to descendant cells, are well known to cause cancers; however, it is increasingly appreciated that the propagation of somatic mutations within a tissue may have a role in causing nonneoplastic disorders and abnormalities in elderly individuals. The nonmalignant clonal expansion of somatic mutations in the hematopoietic system is termed clonal hematopoiesis. This review will briefly discuss how this condition has been linked to various age-related diseases outside the hematopoietic system.

RECENT FINDINGS

Clonal hematopoiesis, resulting from leukemic driver gene mutations or mosaic loss of the Y chromosome in leukocytes, is associated with the development of various forms of cardiovascular disease, including atherosclerosis and heart failure, in a mutation-dependent manner.

SUMMARY

Accumulating evidence shows that clonal hematopoiesis represents a new mechanism for cardiovascular disease and a new risk factor that is as prevalent and consequential as the traditional risk factors that have been studied for decades.

Mosaic Loss of Y Chromosome in White Blood Cells: Its Impact on Men's Health

We present a brief introduction of loss of Y chromosome (LOY) in blood, and describe the known risk factors for this condition. We then overview the associations between LOY and age-related disease traits. Finally, we discuss murine models and potential mechanisms by which LOY contributes to disease.

Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande

We report a search for cosmic-ray boosted dark matter with protons using the 0.37  megaton×years data collected at Super-Kamiokande experiment during the 1996-2018 period (SKI-IV phase). We searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the Galactic Center. No such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. This is the first experimental search for boosted dark matter with hadrons using directional information. The results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 10^{-33}cm^{2} and 10^{-27}cm^{2} for dark matter mass from 1  MeV/c^{2} to 300  MeV/c^{2}.

Hematopoietic loss of Y chromosome leads to cardiac fibrosis and heart failure mortality

Hematopoietic mosaic loss of Y chromosome (mLOY) is associated with increased risk of mortality and age-related diseases in men, but the causal and mechanistic relationships have yet to be established. Here, we show that male mice reconstituted with bone marrow cells lacking the Y chromosome display increased mortality and age-related profibrotic pathologies including reduced cardiac function. Cardiac macrophages lacking the Y chromosome exhibited polarization toward a more fibrotic phenotype, and treatment with a transforming growth factor β1-neutralizing antibody ameliorated cardiac dysfunction in mLOY mice. A prospective study revealed that mLOY in blood is associated with an increased risk for cardiovascular disease and heart failure-associated mortality. Together, these results indicate that hematopoietic mLOY causally contributes to fibrosis, cardiac dysfunction, and mortality in men.

Somatic Mosaicism in Biology and Disease

Contrary to earlier beliefs, every cell in the individual is genetically different due to somatic mutations. Consequently, tissues become a mixture of cells with distinct genomes, a phenomenon termed somatic mosaicism. Recent advances in genome sequencing technology have unveiled possible causes of mutations and how they shape the unique mutational landscape of the tissues. Moreover, the analysis of sequencing data in combination with clinical information has revealed the impacts of somatic mosaicism on disease processes. In this review, we discuss somatic mosaicism in various tissues and its clinical implications for human disease.

Abstract MP258: The Cell Surface Receptors Ror1/2 Control Cardiac Myofibroblast Differentiation

Background: A hallmark of heart failure is cardiac fibrosis, which results from the injury-induced differentiation response of resident fibroblasts to myofibroblasts that deposit extracellular matrix. During myofibroblast differentiation, fibroblasts progress through polarization stages of early pro-inflammation, intermediate proliferation, and late maturation, but the regulators of this progression are poorly understood. Planar cell polarity receptors, receptor tyrosine kinase like orphan receptor 1 and 2 (Ror1/2), can function to promote cell differentiation and transformation. In this study, we investigated the role of the Ror1/2 in a model of heart failure with emphasis on myofibroblast differentiation.

Methods and Results: The role of Ror1/2 during cardiac myofibroblast differentiation was studied in cell culture models of primary murine cardiac fibroblast activation and in knockout mouse models that underwent transverse aortic constriction (TAC) surgery to induce cardiac injury by pressure overload. Expression of Ror1 and Ror2 were robustly and exclusively induced in fibroblasts in hearts after TAC surgery, and both were rapidly upregulated after early activation of primary murine cardiac fibroblasts in culture. Cultured fibroblasts isolated from Ror1/2-KO mice displayed a pro-inflammatory phenotype indicative of impaired myofibroblast differentiation. Although the combined ablation of Ror1/2 in mice did not result in a detectable baseline phenotype, TAC surgery led to the death of all mice by day 6 that was associated with myocardial hyper-inflammation and vascular leakage.

Conclusions: Together, these results show that Ror1/2 are essential for the progression of myofibroblast differentiation and for the adaptive remodeling of the heart in response to pressure overload.

The Cancer Therapy-Related Clonal Hematopoiesis Driver Gene Ppm1d Promotes Inflammation and Non-Ischemic Heart Failure in Mice

[Figure: see text].

TP53-mediated therapy-related clonal hematopoiesis contributes to doxorubicin-induced cardiomyopathy by augmenting a neutrophil-mediated cytotoxic response

Therapy-related clonal hematopoiesis (t-CH) is often observed in cancer survivors. This form of clonal hematopoiesis typically involves somatic mutations in driver genes that encode components of the DNA damage response and confer hematopoietic stem and progenitor cells (HSPCs) with resistance to the genotoxic stress of the cancer therapy. Here, we established a model of TP53-mediated t-CH through the transfer of Trp53 mutant HSPCs to mice, followed by treatment with a course of the chemotherapeutic agent doxorubicin. These studies revealed that neutrophil infiltration in the heart significantly contributes to doxorubicin-induced cardiac toxicity and that this condition is amplified in the model of Trp53-mediated t-CH. These data suggest that t-CH could contribute to the elevated heart failure risk that occurs in cancer survivors who have been treated with genotoxic agents.

The Cell Surface Receptors Ror1/2 Control Cardiac Myofibroblast Differentiation

Background A hallmark of heart failure is cardiac fibrosis, which results from the injury-induced differentiation response of resident fibroblasts to myofibroblasts that deposit extracellular matrix. During myofibroblast differentiation, fibroblasts progress through polarization stages of early proinflammation, intermediate proliferation, and late maturation, but the regulators of this progression are poorly understood. Planar cell polarity receptors, receptor tyrosine kinase-like orphan receptor 1 and 2 (Ror1/2), can function to promote cell differentiation and transformation. In this study, we investigated the role of the Ror1/2 in a model of heart failure with emphasis on myofibroblast differentiation. Methods and Results The role of Ror1/2 during cardiac myofibroblast differentiation was studied in cell culture models of primary murine cardiac fibroblast activation and in knockout mouse models that underwent transverse aortic constriction surgery to induce cardiac injury by pressure overload. Expression of Ror1 and Ror2 were robustly and exclusively induced in fibroblasts in hearts after transverse aortic constriction surgery, and both were rapidly upregulated after early activation of primary murine cardiac fibroblasts in culture. Cultured fibroblasts isolated from Ror1/2 knockout mice displayed a proinflammatory phenotype indicative of impaired myofibroblast differentiation. Although the combined ablation of Ror1/2 in mice did not result in a detectable baseline phenotype, transverse aortic constriction surgery led to the death of all mice by day 6 that was associated with myocardial hyperinflammation and vascular leakage. Conclusions Together, these results show that Ror1/2 are essential for the progression of myofibroblast differentiation and for the adaptive remodeling of the heart in response to pressure overload.

Murine models of clonal hematopoiesis to assess mechanisms of cardiovascular disease

Clonal hematopoiesis (CH) is a phenomenon whereby somatic mutations confer a fitness advantage to hematopoietic stem and progenitor cells (HSPC) and thus facilitate their aberrant clonal expansion. These mutations are carried into progeny leukocytes leading to a situation whereby a substantial fraction of an individual's blood cells originate from the HSPC mutant clone. Although this condition rarely progresses to a hematological malignancy, circulating blood cells bearing the mutation have the potential to affect other organ systems as they infiltrate into tissues under both homeostatic and disease conditions. Epidemiological and clinical studies have revealed that CH is highly prevalent in the elderly and is associated with an increased risk of cardiovascular disease and mortality. Recent experimental studies in murine models have assessed the most commonly mutated "driver" genes associated with CH, and have provided evidence for mechanistic connections between CH and cardiovascular disease. A deeper understanding of the mechanisms by which specific CH mutations promote disease pathogenesis is of importance, as it could pave the way for individualized therapeutic strategies targeting the pathogenic CH gene mutations in the future. Here, we review the epidemiology of CH and the mechanistic work from studies using murine disease models, with a particular focus on the strengths and limitations of these experimental systems. We intend for this review to help investigators select the most appropriate models to study CH in the setting of cardiovascular disease.

Clonal haematopoiesis and cardiovascular disease: how low can you go?

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Bone Marrow Transplantation Procedures in Mice to Study Clonal Hematopoiesis

Clonal hematopoiesis is a prevalent age-associated condition that results from the accumulation of somatic mutations in hematopoietic stem and progenitor cells (HSPCs). Mutations in driver genes, that confer cellular fitness, can lead to the development of expanding HSPC clones that increasingly give rise to progeny leukocytes harboring the somatic mutation. Because clonal hematopoiesis has been associated with heart disease, stroke, and mortality, the development of experimental systems that model these processes is key to understanding the mechanisms that underly this new risk factor. Bone marrow transplantation procedures involving myeloablative conditioning in mice, such as total-body irradiation (TBI), are commonly employed to study the role of immune cells in cardiovascular diseases. However, simultaneous damage to the bone marrow niche and other sites of interest, such as the heart and brain, is unavoidable with these procedures. Thus, our lab has developed two alternative methods to minimize or avoid possible side effects caused by TBI: 1) bone marrow transplantation with irradiation shielding and 2) adoptive BMT to non-conditioned mice. In shielded organs, the local environment is preserved allowing for the analysis of clonal hematopoiesis while the function of resident immune cells is unperturbed. In contrast, the adoptive BMT to non-conditioned mice has the additional advantage that both the local environments of the organs and the hematopoietic niche are preserved. Here, we compare three different hematopoietic cell reconstitution approaches and discuss their strengths and limitations for studies of clonal hematopoiesis in cardiovascular disease.

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.

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.

TET2-Loss-of-Function-Driven Clonal Hematopoiesis Exacerbates Experimental Insulin Resistance in Aging and Obesity

Human aging is frequently accompanied by the acquisition of somatic mutations in the hematopoietic system that induce clonal hematopoiesis, leading to the development of a mutant clone of hematopoietic progenitors and leukocytes. This somatic-mutation-driven clonal hematopoiesis has been associated with an increased incidence of cardiovascular disease and type 2 diabetes, but whether this epidemiological association reflects a direct, causal contribution of mutant hematopoietic and immune cells to age-related metabolic abnormalities remains unexplored. Here, we show that inactivating mutations in the epigenetic regulator TET2, which lead to clonal hematopoiesis, aggravate age- and obesity-related insulin resistance in mice. This metabolic dysfunction is paralleled by increased expression of the pro-inflammatory cytokine IL-1β in white adipose tissue, and it is suppressed by pharmacological inhibition of NLRP3 inflammasome-mediated IL-1β production. These findings support a causal contribution of somatic TET2 mutations to insulin resistance and type 2 diabetes.

Nitroxide-enhanced MRI of cardiovascular oxidative stress

BACKGROUND

In vivo imaging of oxidative stress can facilitate the understanding and treatment of cardiovascular diseases. We evaluated nitroxide-enhanced MRI with 3-carbamoyl-proxyl (3CP) for the detection of myocardial oxidative stress.

METHODS

Three mouse models of cardiac oxidative stress were imaged, namely angiotensin II (Ang II) infusion, myocardial infarction (MI), and high-fat high-sucrose (HFHS) diet-induced obesity (DIO). For the Ang II model, mice underwent MRI at baseline and after 7 days of Ang II (n = 8) or saline infusion (n = 8). For the MI model, mice underwent MRI at baseline (n = 10) and at 1 (n = 8), 4 (n = 9), and 21 (n = 8) days after MI. For the HFHS-DIO model, mice underwent MRI at baseline (n = 20) and 18 weeks (n = 13) after diet initiation. The 3CP reduction rate, K_red , computed using a tracer kinetic model, was used as a metric of oxidative stress. Dihydroethidium (DHE) staining of tissue sections was performed on Day 1 after MI.

RESULTS

For the Ang II model, K_red was higher after 7 days of Ang II versus other groups (p < 0.05). For the MI model, K_red , in the infarct region was significantly elevated on Days 1 and 4 after MI (p < 0.05), whereas K_red in the noninfarcted region did not change after MI. DHE confirmed elevated oxidative stress in the infarct zone on Day 1 after MI. After 18 weeks of HFHS diet, K_red was higher in mice after diet versus baseline (p < 0.05).

CONCLUSIONS

Nitroxide-enhanced MRI noninvasively quantifies tissue oxidative stress as one component of a multiparametric preclinical MRI examination. These methods may facilitate investigations of oxidative stress in cardiovascular disease and related therapies.

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.

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.

Talbot-Lau interferometry-based x-ray imaging system with retractable and rotatable gratings for nondestructive testing

We develop an x-ray imaging system based on Talbot-Lau interferometry equipped with a mechanical structure for retracting and rotating gratings from the optical axis, which enables not only x-ray phase contrast imaging but also conventional x-ray imaging with high-magnification such as microcomputed tomography (μCT). We investigate the characterization of carbon fiber reinforced plastic (CFRP) laminates using this apparatus. Microcracks and fiber orientations are visualized in the dark-field images. Compared with the obtained μCT images, the relationship between the CFRP microstructures and the contrasts in the dark-field images are recognizable.

Cardiovascular Disease, Aging, and Clonal Hematopoiesis

Traditional risk factors are incompletely predictive of cardiovascular disease development, a leading cause of death in the elderly. Recent epidemiological studies have shown that human aging is associated with an increased frequency of somatic mutations in the hematopoietic system, which provide a competitive advantage to a mutant cell, thus allowing for its clonal expansion, a phenomenon known as clonal hematopoiesis. Unexpectedly, these mutations have been associated with a higher incidence of cardiovascular disease, suggesting a previously unrecognized connection between somatic mutations in hematopoietic cells and cardiovascular disease. Here, we provide an up-to-date review of clonal hematopoiesis and its association with aging and cardiovascular disease. We also give a detailed report of the experimental studies that have been instrumental in understanding the relationship between clonal hematopoiesis and cardiovascular disease and have shed light on the mechanisms by which hematopoietic somatic mutations contribute to disease pathology.

Lentiviral CRISPR/Cas9-Mediated Genome Editing for the Study of Hematopoietic Cells in Disease Models

Manipulating genes in hematopoietic stem cells using conventional transgenesis approaches can be time-consuming, expensive, and challenging. Benefiting from advances in genome editing technology and lentivirus-mediated transgene delivery systems, an efficient and economical method is described here that establishes mice in which genes are manipulated specifically in hematopoietic stem cells. Lentiviruses are used to transduce Cas9-expressing lineage-negative bone marrow cells with a guide RNA (gRNA) targeting specific genes and a red fluorescence reporter gene (RFP), then these cells are transplanted into lethally-irradiated C57BL/6 mice. Mice transplanted with lentivirus expressing non-targeting gRNA are used as controls. Engraftment of transduced hematopoietic stem cells are evaluated by flow cytometric analysis of RFP-positive leukocytes of peripheral blood. Using this method, ~90% transduction of myeloid cells and ~70% of lymphoid cells at 4 weeks after transplantation can be achieved. Genomic DNA is isolated from RFP-positive blood cells, and portions of the targeted site DNA are amplified by PCR to validate the genome editing. This protocol provides a high-throughput evaluation of hematopoiesis-regulatory genes and can be extended to a variety of mouse disease models with hematopoietic cell involvement.

P5387CRISPR/dCas9 Activated Expression of Cardiomyocyte Differentiation Factors in CDCs in Myocardial Infarctions

Background

Existing therapies against myocardial infarction (MI) involve disease management by preventing additional damage to the heart muscle. However, new treatment strategies are in greater demand, which deems to focus on restoring cardiac function by replacing the damaged cells after MI, rather than merely manage the disease. Cardiosphere-derived cells (CDCs) have emerged as a potential source of cardiac regenerative therapy. In spite of being a promising option, the poor differentiation potential of CDCs to develop into a functional population of cardiomyocytes has always been a significant setback.

Purpose

The purpose of the present study centers to overcome the aforementioned setback by enhancing the efficiency of rat CDCs to develop into a large population of cardiomyocytes by intrinsic activation of cardio-specific differentiation factors (TNNT2, GATA4, Mef2c) by Crispr/dcas9 assisted transcriptional enhancement system.

Methods

In the foremost step, an exhaustive screening was performed to identify the specific sequences in endogenous regulatory regions (enhancers and promoters) responsible for transcriptional activation of the TNNT2 gene. Once, potential regulatory regions at proximal and distal end of TNNT2 were identified, crRNAs were designed complementing these regions for recruiting Crispr/dcas9 system fused with transcriptional activator like VP64 (CRISPR-dCas9-VP64). Two distinct plasmids were constructed with crRNA (RFP fused) inserts and CRISPR-dCas9-VP64 (GFP fused) followed by transfection in CDCs those isolated from the heart of a neonatal rat. Post transfection, CDCs were then analyzed for the quantitative expression of cardiomyocyte differentiation factors as well as for fibroblast differentiation factors in comparison with un-transfected CDCs.

Results

We identified a panel of specific crRNA targeting the enhancers and promoters which demonstrated significantly higher expression of differentiation factors like troponin, GATA4, and Mef2c. Further, the fluorescent visualization with GFP and RFP was prominent in the CDCs confirming that these panel of crRNA enhanced the expression of differentiation factors compared to the un-transfected counterparts. Interestingly, the same panel crRNA, in contrast, demonstrated diminished expression of fibroblast differentiation factors like Col1A1, clearly emphasizing that the CRISPR dCas9 system recruitment at regulatory regions forms an efficient molecular targeting system for enhancing the differentiation potential of CDCs into cardiomyocytes.

Conclusion

We have identified endogenous regulatory regions responsible for an intrinsic activation of cardio-specific differentiation factors assisted by Crispr/dcas9 gene transcriptional system. We anticipate the method developed herein can enhance and cardiomyogenic efficiency of CDCs to differentiate into a large population of cardiomyocytes to treat Ischemic heart diseases.

JAK2 V617F -Mediated Clonal Hematopoiesis Accelerates Pathological Remodeling in Murine Heart Failure

Janus kinase 2 (valine to phenylalanine at residue 617) (JAK2 ^V617F ) mutations lead to myeloproliferative neoplasms associated with elevated myeloid, erythroid, and megakaryocytic cells. Alternatively these same mutations can lead to the condition of clonal hematopoiesis with no impact on blood cell counts. Here, a model of myeloid-restricted JAK2 ^V617F expression from lineage-negative bone marrow cells was developed and evaluated. This model displayed greater cardiac inflammation and dysfunction following permanent left anterior descending artery ligation and transverse aortic constriction. These data suggest that JAK2 ^V617F mutations arising in myeloid progenitor cells may contribute to cardiovascular disease by promoting the proinflammatory properties of circulating myeloid cells.

Tet2-Mediated Clonal Hematopoiesis Accelerates Heart Failure Through a Mechanism Involving the IL-1β/NLRP3 Inflammasome

BACKGROUND

Recent studies have shown that hematopoietic stem cells can undergo clonal expansion secondary to somatic mutations in leukemia-related genes, thus leading to an age-dependent accumulation of mutant leukocytes in the blood. This somatic mutation-related clonal hematopoiesis is common in healthy older individuals, but it has been associated with an increased incidence of future cardiovascular disease. The epigenetic regulator TET2 is frequently mutated in blood cells of individuals exhibiting clonal hematopoiesis.

OBJECTIVES

This study investigated whether Tet2 mutations within hematopoietic cells can contribute to heart failure in 2 models of cardiac injury.

METHODS

Heart failure was induced in mice by pressure overload, achieved by transverse aortic constriction or chronic ischemia induced by the permanent ligation of the left anterior descending artery. Competitive bone marrow transplantation strategies with Tet2-deficient cells were used to mimic TET2 mutation-driven clonal hematopoiesis. Alternatively, Tet2 was specifically ablated in myeloid cells using Cre recombinase expressed from the LysM promoter.

RESULTS

In both experimental heart failure models, hematopoietic or myeloid Tet2 deficiency worsened cardiac remodeling and function, in parallel with increased interleukin-1beta (IL-1β) expression. Treatment with a selective NLRP3 inflammasome inhibitor protected against the development of heart failure and eliminated the differences in cardiac parameters between Tet2-deficient and wild-type mice.

CONCLUSIONS

Tet2 deficiency in hematopoietic cells is associated with greater cardiac dysfunction in murine models of heart failure as a result of elevated IL-1β signaling. These data suggest that individuals with TET2-mediated clonal hematopoiesis may be at greater risk of developing heart failure and respond better to IL-1β-NLRP3 inflammasome inhibition.

Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions

The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3  GeV/c) direct-photon yields from Au+Au collisions at sqrt[s_{NN}]=39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrt[s_{NN}]=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1  GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5  GeV/c), but when results from different collision energies are compared, an additional sqrt[s_{NN}]-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.

Wnt5a-Mediated Neutrophil Recruitment Has an Obligatory Role in Pressure Overload-Induced Cardiac Dysfunction

BACKGROUND

Although the complex roles of macrophages in myocardial injury are widely appreciated, the function of neutrophils in nonischemic cardiac pathology has received relatively little attention.

METHODS

To examine the regulation and function of neutrophils in pressure overload-induced cardiac hypertrophy, mice underwent treatment with Ly6G antibody to deplete neutrophils and then were subjected to transverse aortic constriction.

RESULTS

Neutrophil depletion diminished transverse aortic constriction-induced hypertrophy and inflammation and preserved cardiac function. Myeloid deficiency of Wnt5a, a noncanonical Wnt, suppressed neutrophil infiltration to the hearts of transverse aortic constriction-treated mice and produced a phenotype that was similar to the neutropenic conditions. Conversely, mice overexpressing Wnt5a in myeloid cells displayed greater hypertrophic growth, inflammation, and cardiac dysfunction. Neutrophil depletion reversed the Wnt5a overexpression-induced cardiac pathology and eliminated differences in cardiac parameters between wild-type and myeloid-specific Wnt5a transgenic mice.

CONCLUSIONS

These findings reveal that Wnt5a-regulated neutrophil infiltration has a critical role in pressure overload-induced heart failure.

Self-reactive CD4+ IL-3+ T cells amplify autoimmune inflammation in myocarditis by inciting monocyte chemotaxis

Acquisition of self-reactive effector CD4⁺ T cells is a major component of the autoimmune response that can occur during myocarditis, an inflammatory form of cardiomyopathy. Although the processes by which self-reactive T cells gain effector function have received considerable attention, how these T cells contribute to effector organ inflammation and damage is less clear. Here, we identified an IL-3-dependent amplification loop that exacerbates autoimmune inflammation. In experimental myocarditis, we show that effector organ-accumulating autoreactive IL-3⁺ CD4⁺ T cells stimulate IL-3R⁺ tissue macrophages to produce monocyte-attracting chemokines. The newly recruited monocytes differentiate into antigen-presenting cells that stimulate local IL-3⁺ CD4⁺ T cell proliferation, thereby amplifying organ inflammation. Consequently, Il3 ^-/- mice resist developing robust autoimmune inflammation and myocardial dysfunction, whereas therapeutic IL-3 targeting ameliorates disease. This study defines a mechanism that orchestrates inflammation in myocarditis, describes a previously unknown function for IL-3, and identifies IL-3 as a potential therapeutic target in patients with myocarditis.

Clonal Hematopoiesis and Its Impact on Cardiovascular Disease

A number of recent epidemiological studies have associated the clonal expansion of hematopoietic cells, a process referred to as clonal hematopoiesis, with increased mortality. Clonal hematopoiesis increases the risk of hematological cancer, but this overall risk cannot account for the increase in mortality in the general population. Surprisingly, these mutations have also been associated with higher rates of cardiovascular disease, suggesting a previously unrecognized link between somatic mutations in hematopoietic cells and chronic disease. Here, we review recent epidemiological and experimental studies on clonal hematopoiesis that relate to cardiovascular disease.

CRISPR-Mediated Gene Editing to Assess the Roles of Tet2 and Dnmt3a in Clonal Hematopoiesis and Cardiovascular Disease

RATIONALE

Clonal hematopoiesis has been associated with increased mortality and cardiovascular disease. This condition can arise from somatic mutations in preleukemic driver genes within hematopoietic stem/progenitor cells. Approximately 40 candidate driver genes have been identified, but mutations in only 1 of these genes, TET2 (ten-eleven translocation-2), has been shown to casually contribute to cardiovascular disease in murine models.

OBJECTIVE

To develop a facile system to evaluate the disease characteristics of different clonal hematopoiesis driver genes using lentivirus vector and CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9) methodology. Using this methodology, evaluate whether Dnmt3a (DNA [cytosine-5]-methyltransferase 3a)-a commonly occurring clonal hematopoiesis driver gene-causally contributes to cardiovascular disease.

METHODS AND RESULTS

Lentivirus vectors were used to deliver Cas9 and guide RNA to introduce inactivating mutations in Tet2 and Dnmt3a in lineage-negative bone marrow cells. After implantation into lethally irradiated mice, these cells were engrafted and gave rise to labeled blood cell progeny. When challenged with an infusion of Ang II (angiotensin II), mice with inactivating mutations in Tet2 or Dnmt3a displayed greater cardiac hypertrophy, diminished cardiac function, and greater cardiac and renal fibrosis. In comparison with Tet2, inactivation of Dnmt3a did not lead to detectable expansion of the mutant hematopoietic cells during the time course of these experiments. Tet2 inactivation promoted the expression of IL (interleukin) 1β, IL-6, and Ccl5, whereas Dnmt3a inactivation promoted the expression of Cxcl1 (CXC chemokine ligand), Cxcl2, IL-6, and Ccl5 in a lipopolysaccharide-stimulated macrophage cell line.

CONCLUSIONS

Experiments using lentivirus vector/CRISPR methodology provided evidence suggesting that inactivating DNMT3A mutations in hematopoietic cells contributes to cardiovascular disease. Comparative analyses showed that inactivation of Tet2 and Dnmt3 was similar in their ability to promote Ang II-induced cardiac dysfunction and renal fibrosis in mice. However, gene-specific actions were indicated by differences in kinetics of hematopoietic stem/progenitor cell expansion and different patterns of inflammatory gene expression.