One-year outcome of robotical vs. manual percutaneous coronary intervention.

BACKGROUND: Robotic-assisted percutaneous coronary intervention (R-PCI) is a promising technology for optimizing the treatment of patients with coronary heart disease. For a better understanding of the potential of R-PCI in clinical routine compared to conventional manual PCI (M-PCI) both initial treatment success of the index procedure and long-term outcome have to be analysed. METHODS: Prospective evaluation from the FRiK (DRKS00023868) registry of all R-PCI cases with the CorPath GRX Cardiology by Siemens Healthineers and Corindus in the Freiburg University Heart Center between 04/2022 and 03/2023. Index procedure success and safety, radiation dose of patients and personnel, and 1-year outcome will be reported. Findings will be compared to a prospective control group of M-PCI patients treated by the same team of interventionalists during the same observation period. RESULTS: Seventy patients received R-PCI and were included in the registry. PCI success rate was 100%, with 19% requiring manual assistance. No complications (MACE-major adverse cardiovascular events) occurred. Compared with 70 matched-pair M-PCI patients, there was a higher median procedural time (103 min vs. 67 min, p < 0.001) and fluoroscopy time (18 min vs. 15 min, p = 0.002), and more contrast volume was used (180 ml vs. 160 ml, p = 0.041) in R-PCI vs. M-PCI patients. However, there was no significant difference of the dose-area product (4062 vs. 3242 cGycm2, p = 0.361). One year after the intervention, there was no difference in mortality, rehospitalisation, unscheduled PCI or target vessel failure. Health-related quality of life evaluation 6 and 12 months after the index procedure (NYHA, CCS, SAQ7 and EQ-5D-5L) was similar in both groups. CONCLUSION: R-PCI is feasible and safe. Compared to M-PCI, index procedure success rate is high, safety profile is favourable, and manual assistance was required in only few cases. At 1-year follow-up results for R-PCI vs. M-PCI considering mortality, rehospitalisation, morbidity and target vessel failure were equal.

Combination of high resolution MRI with 3D-printed needle guides for ex vivo myocardial biopsies.

Magnetic resonance imaging (MRI) provides a multitude of techniques to detect and characterize myocardial infarction. To correlate MRI findings with histology, in most cases terminal animal studies are performed; however, precise extraction and spatial correlation of myocardial tissue samples to MRI image data is difficult. In this proof of concept study, we present a 3D-printing technique to facilitate the extraction of tissue samples from myocardial regions. Initially, seven pig hearts embedded in formaldehyde were imaged on a clinical 3 T system to define biopsy targets on high resolution ex vivo images. Magnitude images and R2*-maps acquired with a 3D multi-echo gradient echo sequence and 0.58 mm isotropic resolution were used to create digital models of the cardiac anatomy. Biopsy guides were 3D-printed to steer the extraction of myocardial samples. In total, 61 tissue samples were extracted with an average offset of the tissue sample location from the target location of 0.59 ± 0.36 mm. This offset was not dependent on the distance of the target point to the epicardial surface. Myocardial tissue could be extracted from all samples. The presented method enables extraction of myocardial tissue samples that are selected by ex vivo MRI with submillimeter precision.

Nonpreferential but Detrimental Accumulation of Macrophages With Clonal Hematopoiesis-Driver Mutations in Cardiovascular Tissues-Brief Report.

BACKGROUND: Clonal hematopoiesis of indeterminate potential (CHIP) is an acquired genetic risk factor for both leukemia and cardiovascular disease. It results in proinflammatory myeloid cells in the bone marrow and blood; however, how these cells behave in the cardiovascular tissue remains unclear. Our study aimed at investigating whether CHIP-mutated macrophages accumulate preferentially in cardiovascular tissues and examining the transcriptome of tissue macrophages from DNMT3A (DNA methyltransferase 3 alpha) or TET2 (Tet methylcytosine dioxygenase 2) mutation carriers. METHODS: We recruited patients undergoing carotid endarterectomy or heart surgeries to screen for CHIP mutation carriers using targeted genomic sequencing. Myeloid and lymphoid cells were isolated from blood and cardiovascular tissue collected during surgeries using flow cytometry. DNA and RNA extracted from these sorted cells were subjected to variant allele frequency measurement using droplet digital polymerase chain reaction and transcriptomic profiling using bulk RNA sequencing, respectively. RESULTS: Using droplet digital polymerase chain reaction, we detected similar variant allele frequency of CHIP in monocytes from blood and macrophages from atheromas and heart tissues, even among heart macrophages with and without CCR2 (C-C motif chemokine receptor 2) expression. Bulk RNA sequencing revealed a proinflammatory gene profile of myeloid cells from DNMT3A or TET2 mutation carriers compared with those from noncarriers. CONCLUSIONS: Quantitatively, CHIP-mutated myeloid cells did not preferentially accumulate in cardiovascular tissues, but qualitatively, they expressed a more disease-prone phenotype.

A comparative gene expression matrix in Apoe-deficient mice identifies unique and atherosclerotic disease stage-specific gene regulation patterns in monocytes and macrophages.

BACKGROUND AND AIMS: Atherosclerosis is a systemic and chronic inflammatory disease propagated by monocytes and macrophages. Yet, our knowledge on how transcriptome of these cells evolves in time and space is limited. We aimed at characterizing gene expression changes in site-specific macrophages and in circulating monocytes during the course of atherosclerosis. METHODS: We utilized apolipoprotein E-deficient mice undergoing one- and six-month high cholesterol diet to model early and advanced atherosclerosis. Aortic macrophages, peritoneal macrophages, and circulating monocytes from each mouse were subjected to bulk RNA-sequencing (RNA-seq). We constructed a comparative directory that profiles lesion- and disease stage-specific transcriptomic regulation of the three cell types in atherosclerosis. Lastly, the regulation of one gene, Gpnmb, whose expression positively correlated with atheroma growth, was validated using single-cell RNA-seq (scRNA-seq) of atheroma plaque from murine and human. RESULTS: The convergence of gene regulation between the three investigated cell types was surprisingly low. Overall 3245 differentially expressed genes were involved in the biological modulation of aortic macrophages, among which less than 1% were commonly regulated by the remote monocytes/macrophages. Aortic macrophages regulated gene expression most actively during atheroma initiation. Through complementary interrogation of murine and human scRNA-seq datasets, we showcased the practicality of our directory, using the selected gene, Gpnmb, whose expression in aortic macrophages, and a subset of foamy macrophages in particular, strongly correlated with disease advancement during atherosclerosis initiation and progression. CONCLUSIONS: Our study provides a unique toolset to explore gene regulation of macrophage-related biological processes in and outside the atheromatous plaque at early and advanced disease stages.

P2Y12-dependent activation of hematopoietic stem and progenitor cells promotes emergency hematopoiesis after myocardial infarction.

Emergency hematopoiesis is the driving force of the inflammatory response to myocardial infarction (MI). Increased proliferation of hematopoietic stem and progenitor cells (LSK) after MI enhances cell production in the bone marrow (BM) and replenishes leukocyte supply for local cell recruitment to the infarct. Decoding the regulation of the inflammatory cascade after MI may provide new avenues to improve post-MI remodeling. In this study, we describe the influence of adenosine diphosphate (ADP)-dependent P2Y12-mediated signaling on emergency hematopoiesis and cardiac remodeling after MI. Permanent coronary ligation was performed to induce MI in a murine model. BM activation, inflammatory cell composition and cardiac function were assessed using global and platelet-specific gene knockout and pharmacological inhibition models for P2Y12. Complementary in vitro studies allowed for investigation of ADP-dependent effects on LSK cells. We found that ADP acts as a danger signal for the hematopoietic BM and fosters emergency hematopoiesis by promoting Akt phosphorylation and cell cycle progression. We were able to detect P2Y12 in LSK, implicating a direct effect of ADP on LSK via P2Y12 signaling. P2Y12 knockout and P2Y12 inhibitor treatment with prasugrel reduced emergency hematopoiesis and the excessive inflammatory response to MI, translating to lower numbers of downstream progeny and inflammatory cells in the blood and infarct. Ultimately, P2Y12 inhibition preserved cardiac function and reduced chronic adverse cardiac remodeling after MI. P2Y12-dependent signaling is involved in emergency hematopoiesis after MI and fuels post-ischemic inflammation, proposing a novel, non-canonical value for P2Y12 antagonists beyond inhibition of platelet-mediated atherothrombosis.

P2X4 deficiency reduces atherosclerosis and plaque inflammation in mice.

Extracellular adenosine-5'-triphosphate (ATP) acts as an import signaling molecule mediating inflammation via purinergic P2 receptors. ATP binds to the purinergic receptor P2X4 and promotes inflammation via increased expression of pro-inflammatory cytokines. Because of the central role of inflammation, we assumed a functional contribution of the ATP-P2X4-axis in atherosclerosis. Expression of P2X4 was increased in atherosclerotic aortic arches from low-density lipoprotein receptor-deficient mice being fed a high cholesterol diet as assessed by real-time polymerase chain reaction and immunohistochemistry. To investigate the functional role of P2X4 in atherosclerosis, P2X4-deficient mice were crossed with low-density lipoprotein receptor-deficient mice and fed high cholesterol diet. After 16 weeks, P2X4-deficient mice developed smaller atherosclerotic lesions compared to P2X4-competent mice. Furthermore, intravital microscopy showed reduced ATP-induced leukocyte rolling at the vessel wall in P2X4-deficient mice. Mechanistically, we found a reduced RNA expression of CC chemokine ligand 2 (CCL-2), C-X-C motif chemokine-1 (CXCL-1), C-X-C motif chemokine-2 (CXCL-2), Interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) as well as a decreased nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)-inflammasome priming in atherosclerotic plaques from P2X4-deficient mice. Moreover, bone marrow derived macrophages isolated from P2X4-deficient mice revealed a reduced ATP-mediated release of CCL-2, CC chemokine ligand 5 (CCL-5), Interleukin-1ß (IL-1ß) and IL-6. Additionally, P2X4-deficient mice shared a lower proportion of pro-inflammatory Ly6Chigh monocytes and a higher proportion of anti-inflammatory Ly6Clow monocytes, and expressend less endothelial VCAM-1. Finally, increased P2X4 expression in human atherosclerotic lesions from carotid endarterectomy was found, indicating the importance of potential implementations of this study's findings for human atherosclerosis. Collectively, P2X4 deficiency reduced experimental atherosclerosis, plaque inflammation and inflammasome priming, pointing to P2X4 as a potential therapeutic target in the fight against atherosclerosis.

Genetic Deficiency of TRAF5 Promotes Adipose Tissue Inflammation and Aggravates Diet-Induced Obesity in Mice.

Objective: The accumulation of inflammatory leukocytes is a prerequisite of adipose tissue inflammation during cardiometabolic disease. We previously reported that a genetic deficiency of the intracellular signaling adaptor TRAF5 (TNF [tumor necrosis factor] receptor-associated factor 5) accelerates atherosclerosis in mice by increasing inflammatory cell recruitment. Here, we tested the hypothesis that an impairment of TRAF5 signaling modulates adipose tissue inflammation and its metabolic complications in a model of diet-induced obesity in mice. Approach and Results: To induce diet-induced obesity and adipose tissue inflammation, wild-type or Traf5-/- mice consumed a high-fat diet for 18 weeks. Traf5-/- mice showed an increased weight gain, impaired insulin tolerance, and increased fasting blood glucose. Weight of livers and peripheral fat pads was increased in Traf5-/- mice, whereas lean tissue weight and growth were not affected. Flow cytometry of the stromal vascular fraction of visceral adipose tissue from Traf5-/- mice revealed an increase in cytotoxic T cells, CD11c+ macrophages, and increased gene expression of proinflammatory cytokines and chemokines. At the level of cell types, expression of TNF[alpha], MIP (macrophage inflammatory protein)-1[alpha], MCP (monocyte chemoattractant protein)-1, and RANTES (regulated on activation, normal T-cell expressed and secreted) was significantly upregulated in Traf5-deficient adipocytes but not in Traf5-deficient leukocytes from visceral adipose tissue. Finally, Traf5 expression was lower in adipocytes from obese patients and mice and recovered in adipose tissue of obese patients one year after bariatric surgery. Conclusions: We show that a genetic deficiency of TRAF5 in mice aggravates diet-induced obesity and its metabolic derangements by a proinflammatory response in adipocytes. Our data indicate that TRAF5 may promote anti-inflammatory and obesity-preventing signaling events in adipose tissue.

Inhibition of macrophage proliferation dominates plaque regression in response to cholesterol lowering.

Statins induce plaque regression characterized by reduced macrophage content in humans, but the underlying mechanisms remain speculative. Studying the translational APOE*3-Leiden.CETP mouse model with a humanized lipoprotein metabolism, we find that systemic cholesterol lowering by oral atorvastatin or dietary restriction inhibits monocyte infiltration, and reverses macrophage accumulation in atherosclerotic plaques. Contrary to current believes, none of (1) reduced monocyte influx (studied by cell fate mapping in thorax-shielded irradiation bone marrow chimeras), (2) enhanced macrophage egress (studied by fluorescent bead labeling and transfer), or (3) atorvastatin accumulation in murine or human plaque (assessed by mass spectrometry) could adequately account for the observed loss in macrophage content in plaques that undergo phenotypic regression. Instead, suppression of local proliferation of macrophages dominates phenotypic plaque regression in response to cholesterol lowering: the lower the levels of serum LDL-cholesterol and lipid contents in murine aortic and human carotid artery plaques, the lower the rates of in situ macrophage proliferation. Our study identifies macrophage proliferation as the predominant turnover determinant and an attractive target for inducing plaque regression.

Nationwide outcomes of aortic valve replacement for pure aortic regurgitation in Germany 2008-2015.

BACKGROUND: Transcatheter aortic valve replacement (TAVR) is routinely used in patients with severe aortic stenosis at increased operative risk. Due to potential technical difficulties, TAVR is not recommended for pure aortic regurgitation (AR). Smaller studies reported its use in AR, but data from big registries are lacking. The present study analyzes the nationwide use of surgical aortic valve replacement (SAVR) and TAVR in patients with AR from 2008 until 2015. METHODS: We identified 138,237 cases of aortic valve replacement in Germany based on ICD and OPS codes. RESULTS: Of 13.2% SAVR-cases and 1.3% of TAVR cases were performed in AR. AR patients undergoing SAVR were younger with lower logistic EuroSCORE (stenosis: 6.1 ± 5.6; AR: 4.5 ± 4.9). Nevertheless, stroke rates, bleedings, prolonged mechanical ventilation, and in-hospital mortality were higher (mortality: stenosis 2.6%, AR: 4.7%). In the TAVR group, patients with AR were at higher operative risk (logistic EuroSCORE: transfemoral (TF)-TAVR: stenosis: 14.3 ± 10.4; AR: 17.3 ± 13.3. Transapical (TA)-TAVR: stenosis: 16.1 ± 11.4; AR: 15.7 ± 12.2). Stroke rates were lower, but bleedings and prolonged ventilation occurred more frequently after TF-TAVR in AR compared to stenosis. The mortality varied markedly (TF-TAVR: 15.2% in 2011; 2.8% in 2015; TA-TAVR: 17.7% in 2012 and 0% in 2014). CONCLUSION: TAVR is off-label used in AR in clinical practice. TAVR seems to be a safe option for AR with regard to in-hospital outcomes. However, further research evaluating long-term outcomes is required to establish the feasibility of TAVR in pure AR.

Psychiatric Presentation of Anti-NMDA Receptor Encephalitis.

Background: Anti-N-methyl D-aspartate (NMDA) receptor encephalitis is an autoimmune condition characterized by neuropsychiatric symptoms, including epileptic seizures, movement disorders, autonomic instability, disturbances of consciousness, paranoia, delusions, and catatonia. Ovarian teratomas and viral infections, typically Herpes simplex viruses, have previously been demonstrated to precipitate anti-NMDA receptor encephalitis, but in many cases, the trigger remains unclear. The detection of anti-NMDA receptor antibodies in cerebrospinal fluid (CSF), in combination with other CSF, electroencephalography (EEG), or magnetic resonance imaging (MRI) abnormalities, typically leads to diagnostic clarification. Case Presentation: We present the case of a 22-year-old female patient who developed an acute polymorphic psychotic episode 3 days after receiving a booster vaccination against tetanus, diphtheria, pertussis, and polio (Tdap-IPV). Her psychiatric symptoms were initially diagnosed as a primary psychiatric disorder. Her MRI, EEG, and CSF results were non-specific. Anti-NMDA receptor IgG antibodies against the GluN1 subunit were detected in her serum (with a maximum titer of 1:320), but not in her CSF. [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) showed pronounced relative hypermetabolism of her association cortices and a relative hypometabolism of the primary cortices, on the basis of which an anti-NMDA receptor encephalitis diagnosis was made, and treatment with a steroid pulse was initiated. The treatment led to fast and convincing clinical improvement with normalization of neuropsychological findings, considerable improvement of FDG-PET findings, and decreasing antibody titers. Conclusion: The patient's psychiatric symptoms were most likely caused by anti-NMDA receptor encephalitis. Her polymorphic psychotic symptoms first occurred after she had received a Tdap-IPV booster vaccination. Although the vaccination cannot have caused the initial antibody formation since IgG serum antibodies were detected only 3 days after administration of the vaccine, the vaccine may have exerted immunomodulatory effects. MRI, EEG, and CSF findings were non-specific; however, FDG-PET identified brain involvement consistent with anti-NMDA receptor encephalitis. This case shows the importance of implementing a multimodal diagnostic work-up in similar situations. The negative CSF antibody finding furthermore fits to the hypothesis that the brain may act as an immunoprecipitator for anti-NMDA receptor antibodies.

Risk-Adjusted Comparison of In-Hospital Outcomes of Transcatheter and Surgical Aortic Valve Replacement.

Background Transfemoral transcatheter aortic valve replacement (TF-TAVR) is recommended for patients suffering from aortic valve stenosis at increased operative risk. Beyond that, patients with different comorbidities could benefit from TF-TAVR. The present study compares real-world in-hospital outcomes of surgical aortic valve replacement and TF-TAVR. Methods and Results For all 33 789 isolated TF-TAVR and surgical aortic valve replacement procedures performed in Germany in 2014 and 2015, comorbidities and in-hospital outcomes were identified by International Classification of Diseases (ICD)- and OPS (Operation and procedure key)-codes. Patients undergoing TF-TAVR were older and at increased estimated risk. Outcomes were risk-adjusted to allow comparison. TF-TAVR was associated with a lower risk for acute kidney injuries (odds ratio [OR] 0.62, P<0.001), for bleeding (OR 0.17, P<0.001), and for prolonged mechanical ventilation (>48 hours, OR 0.21, P<0.001). Risk for stroke was similar (OR 1.07, P=0.558). As expected, the risk for pacemaker implantations was higher after TF-TAVR (OR 4.61, P<0.001). In all patients, none of the treatment strategies had a clear advantage on the risk for in-hospital mortality (OR 0.83, P=0.068). However, in patients aged >80 years and at high operative risk undergoing TF-TAVR in-hospital mortality was lower (TF-TAVR versus surgical aortic valve replacement 80-84, OR 0.55; P=0.002; ≥85 years, OR 0.42, P=0.006; EuroSCORE (European System for Cardiac Operative Risk Evaluation) >9: OR 0.62, P=0.001). TF-TAVR was superior in patients with renal failure and in NYHA (New York Heart Association)-Class III/IV. Other risk groups were not found to be factors favoring a treatment strategy. Conclusions The present study indicates a superiority of TF-TAVR in clinical practice for patients at increased operative risk, aged >80 years, in NYHA-Class III/IV, and with renal failure.

Purinergic receptor Y2 (P2Y2)- dependent VCAM-1 expression promotes immune cell infiltration in metabolic syndrome.

Sterile inflammation of visceral fat, provoked by dying adipocytes, links the metabolic syndrome to cardiovascular disease. Danger-associated molecular patterns, such as adenosine triphosphate (ATP), are released by activated or dying cells and orchestrate leukocyte infiltration and inflammation via the purinergic receptor P2Y2. The gene expression of ATP receptor P2Y2 did not change in several tissues in the course of obesity, but was increased within epididymal fat. Adipose tissue from P2Y 2-/- mice consuming high-fat diet (HFD) contained less crown-like structures with a reduced frequency of adipose tissue macrophages (ATMs). This was likely due to decreased leukocyte migration because of missing VCAM-1 exposition on P2Y2 deficient hypertrophic adipose tissue endothelial cells. Accordingly, P2Y 2-/- mice showed blunted traits of the metabolic syndrome: they gained less weight compared to P2Y 2+/+ controls, while intake of food and movement behaviour remained unchanged. Liver and adipose tissue were smaller in P2Y 2-/- animals. Insulin tolerance testing (ITT) performed in obese P2Y 2-/- mice revealed a better insulin sensitivity as well as lower plasma C-peptide and cholesterol levels. We demonstrate that interfering with somatic P2Y2 signalling prevents excessive immune cell deposition in diet-induced obesity (DIO), both attenuating adipose tissue inflammation and ameliorating the metabolic phenotype. Thus, blocking the P2Y2 cascade may be a promising strategy to limit metabolic disease and its sequelae.

Risk factors and outcome of postoperative delirium after transcatheter aortic valve replacement.

BACKGROUND: POD is associated with a worse postoperative course in patients after cardiac surgery, but its incidence and effects after TAVR are not well-understood. The aim of the present study was to analyze incidence, risk factors, and in-hospital outcomes of postoperative delirium (POD) after transfemoral (TF-AVR) and transapical (TA-AVR) transcatheter aortic valve replacement (TAVR) in a nationwide cohort. METHODS AND RESULTS: Administrative data on all patients undergoing isolated TAVR in Germany in 2014 were analyzed. 9038 TF-AVR and 2522 TA-AVR procedures were performed. POD incidence was 7% after TF-AVR and 12% after TA-AVR. Atrial fibrillation (TF: OR 1.35, p < 0.001; TA: OR 1.53, p = 0.001) and NYHA III/IV (TF: OR 1.23, p = 0.017, TA: OR 1.51, p = 0.001) were independent risk factors for POD. Dementia was a risk factor only in TF-AVR (OR 3.04, p < 0.001). Female sex was protective (TF: OR 0.56, p < 0.001, TA: OR 0.51, p < 0.001). We found the occurrence of POD to be associated with more postoperative complications such as stroke and bleeding. Consequently, patients with POD were ventilated and hospitalized longer and suffered an increased risk of in-hospital mortality (unadjusted OR TF: 1.83, p = 0.001, TA: 1.82, p = 0.01). After adjusting for postoperative events and comorbidities, POD's effect on in-hospital mortality disappeared. In contrast, stroke and bleeding remained independent predictors for mortality irrespective of POD. CONCLUSIONS: Patients with POD after TAVR are at increased risk for in-hospital mortality. However, after adjusting for postoperative events and comorbidities, stroke and bleeding, but not POD, are independent mortality predictors.

Inflammatory Pathways Regulated by Tumor Necrosis Receptor-Associated Factor 1 Protect From Metabolic Consequences in Diet-Induced Obesity.

RATIONALE: The coincidence of inflammation and metabolic derangements in obese adipose tissue has sparked the concept of met-inflammation. Previous observations, however, suggest that inflammatory pathways may not ultimately cause dysmetabolism. OBJECTIVE: We have revisited the relationship between inflammation and metabolism by testing the role of TRAF (tumor necrosis receptor-associated factor)-1, an inhibitory adapter of inflammatory signaling of TNF (tumor necrosis factor)-α, IL (interleukin)-1ß, and TLRs (toll-like receptors). METHODS AND RESULTS: Mice deficient for TRAF-1, which is expressed in obese adipocytes and adipose tissue lymphocytes, caused an expected hyperinflammatory phenotype in adipose tissue with enhanced adipokine and chemokine expression, increased leukocyte accumulation, and potentiated proinflammatory signaling in macrophages and adipocytes in a mouse model of diet-induced obesity. Unexpectedly, TRAF-1-/- mice were protected from metabolic derangements and adipocyte growth, failed to gain weight, and showed improved insulin resistance-an effect caused by increased lipid breakdown in adipocytes and UCP (uncoupling protein)-1-enabled thermogenesis. TRAF-1-dependent catabolic and proinflammatory cues were synergistically driven by ß3-adrenergic and inflammatory signaling and required the presence of both TRAF-1-deficient adipocytes and macrophages. In human obesity, TRAF-1-dependent genes were upregulated. CONCLUSIONS: Enhancing TRAF-1-dependent inflammatory pathways in a gain-of-function approach protected from metabolic derangements in diet-induced obesity. These findings identify TRAF-1 as a regulator of dysmetabolism in mice and humans and question the pathogenic role of chronic inflammation in metabolism.

Proliferation and Recruitment Contribute to Myocardial Macrophage Expansion in Chronic Heart Failure.

RATIONALE: Macrophages reside in the healthy myocardium, participate in ischemic heart disease, and modulate myocardial infarction (MI) healing. Their origin and roles in post-MI remodeling of nonischemic remote myocardium, however, remain unclear. OBJECTIVE: This study investigated the number, origin, phenotype, and function of remote cardiac macrophages residing in the nonischemic myocardium in mice with chronic heart failure after coronary ligation. METHODS AND RESULTS: Eight weeks post MI, fate mapping and flow cytometry revealed that a 2.9-fold increase in remote macrophages results from both increased local macrophage proliferation and monocyte recruitment. Heart failure produced by extensive MI, through activation of the sympathetic nervous system, expanded medullary and extramedullary hematopoiesis. Circulating Ly6C(high) monocytes rose from 64±5 to 108±9 per microliter of blood (P<0.05). Cardiac monocyte recruitment declined in Ccr2(-/-) mice, reducing macrophage numbers in the failing myocardium. Mechanical strain of primary murine and human macrophage cultures promoted cell cycle entry, suggesting that the increased wall tension in post-MI heart failure stimulates local macrophage proliferation. Strained cells activated the mitogen-activated protein kinase pathway, whereas specific inhibitors of this pathway reduced macrophage proliferation in strained cell cultures and in the failing myocardium (P<0.05). Steady-state cardiac macrophages, monocyte-derived macrophages, and locally sourced macrophages isolated from failing myocardium expressed different genes in a pattern distinct from the M1/M2 macrophage polarization paradigm. In vivo silencing of endothelial cell adhesion molecules curbed post-MI monocyte recruitment to the remote myocardium and preserved ejection fraction (27.4±2.4 versus 19.1±2%; P<0.05). CONCLUSIONS: Myocardial failure is influenced by an altered myeloid cell repertoire.

RNAi targeting multiple cell adhesion molecules reduces immune cell recruitment and vascular inflammation after myocardial infarction.

Myocardial infarction (MI) leads to a systemic surge of vascular inflammation in mice and humans, resulting in secondary ischemic complications and high mortality. We show that, in ApoE(-/-) mice with coronary ligation, increased sympathetic tone up-regulates not only hematopoietic leukocyte production but also plaque endothelial expression of adhesion molecules. To counteract the resulting arterial leukocyte recruitment, we developed nanoparticle-based RNA interference (RNAi) that effectively silences five key adhesion molecules. Simultaneously encapsulating small interfering RNA (siRNA)-targeting intercellular cell adhesion molecules 1 and 2 (Icam1 and Icam2), vascular cell adhesion molecule 1 (Vcam1), and E- and P-selectins (Sele and Selp) into polymeric endothelial-avid nanoparticles reduced post-MI neutrophil and monocyte recruitment into atherosclerotic lesions and decreased matrix-degrading plaque protease activity. Five-gene combination RNAi also curtailed leukocyte recruitment to ischemic myocardium. Therefore, targeted multigene silencing may prevent complications after acute MI.

Atheroprotection through SYK inhibition fails in established disease when local macrophage proliferation dominates lesion progression.

Macrophages in the arterial intima sustain chronic inflammation during atherogenesis. Under hypercholesterolemic conditions murine Ly6C(high) monocytes surge in the blood and spleen, infiltrate nascent atherosclerotic plaques, and differentiate into macrophages that proliferate locally as disease progresses. Spleen tyrosine kinase (SYK) may participate in downstream signaling of various receptors that mediate these processes. We tested the effect of the SYK inhibitor fostamatinib on hypercholesterolemia-associated myelopoiesis and plaque formation in Apoe(-/-) mice during early and established atherosclerosis. Mice consuming a high cholesterol diet supplemented with fostamatinib for 8 weeks developed less atherosclerosis. Histologic and flow cytometric analysis of aortic tissue showed that fostamatinib reduced the content of Ly6C(high) monocytes and macrophages. SYK inhibition limited Ly6C(high) monocytosis through interference with GM-CSF/IL-3 stimulated myelopoiesis, attenuated cell adhesion to the intimal surface, and blocked M-CSF stimulated monocyte to macrophage differentiation. In Apoe(-/-) mice with established atherosclerosis, however, fostamatinib treatment did not limit macrophage accumulation or lesion progression despite a significant reduction in blood monocyte counts, as lesional macrophages continued to proliferate. Thus, inhibition of hypercholesterolemia-associated monocytosis, monocyte infiltration, and differentiation by SYK antagonism attenuates early atherogenesis but not established disease when local macrophage proliferation dominates lesion progression.

Targeting Interleukin-1ß Reduces Leukocyte Production After Acute Myocardial Infarction.

BACKGROUND: Myocardial infarction (MI) is an ischemic wound that recruits millions of leukocytes. MI-associated blood leukocytosis correlates inversely with patient survival, yet the signals driving heightened leukocyte production after MI remain incompletely understood. METHODS AND RESULTS: With the use of parabiosis surgery, this study shows that soluble danger signals, among them interleukin-1ß, increase bone marrow hematopoietic stem cell proliferation after MI. Data obtained in bone marrow reconstitution experiments reveal that interleukin-1ß enhances hematopoietic stem cell proliferation by both direct actions on hematopoietic cells and through modulation of the bone marrow's hematopoietic microenvironment. An antibody that neutralizes interleukin-1ß suppresses these effects. Anti-interleukin-1ß treatment dampens the post-MI increase in hematopoietic stem cell proliferation. Consequently, decreased leukocyte numbers in the blood and infarct reduce inflammation and diminish post-MI heart failure in ApoE(-/-) mice with atherosclerosis. CONCLUSIONS: The presented insight into post-MI bone marrow activation identifies a mechanistic target for muting inflammation in the ischemically damaged heart.

Myocardial Infarction Activates CCR2(+) Hematopoietic Stem and Progenitor Cells.

Following myocardial infarction (MI), myeloid cells derived from the hematopoietic system drive a sharp increase in systemic leukocyte levels that correlates closely with mortality. The origin of these myeloid cells, and the response of hematopoietic stem and progenitor cells (HSPCs) to MI, however, is unclear. Here, we identify a CCR2(+)CD150(+)CD48(-) LSK hematopoietic subset as the most upstream contributor to emergency myelopoiesis after ischemic organ injury. This subset has 4-fold higher proliferation rates than CCR2(-)CD150(+)CD48(-) LSK cells, displays a myeloid differentiation bias, and dominates the migratory HSPC population. We further demonstrate that the myeloid translocation gene 16 (Mtg16) regulates CCR2(+) HSPC emergence. Mtg16(-/-) mice have decreased levels of systemic monocytes and infarct-associated macrophages and display compromised tissue healing and post-MI heart failure. Together, these data provide insights into regulation of emergency hematopoiesis after ischemic injury and identify potential therapeutic targets to modulate leukocyte output after MI.

Ischemic stroke activates hematopoietic bone marrow stem cells.

RATIONALE: The mechanisms leading to an expanded neutrophil and monocyte supply after stroke are incompletely understood. OBJECTIVE: To test the hypothesis that transient middle cerebral artery occlusion (tMCAO) in mice leads to activation of hematopoietic bone marrow stem cells. METHODS AND RESULTS: Serial in vivo bioluminescence reporter gene imaging in mice with tMCAO revealed that bone marrow cell cycling peaked 4 days after stroke (P<0.05 versus pre tMCAO). Flow cytometry and cell cycle analysis showed activation of the entire hematopoietic tree, including myeloid progenitors. The cycling fraction of the most upstream hematopoietic stem cells increased from 3.34%±0.19% to 7.32%±0.52% after tMCAO (P<0.05). In vivo microscopy corroborated proliferation of adoptively transferred hematopoietic progenitors in the bone marrow of mice with stroke. The hematopoietic system's myeloid bias was reflected by increased expression of myeloid transcription factors, including PU.1 (P<0.05), and by a decline in lymphocyte precursors. In mice after tMCAO, tyrosine hydroxylase levels in sympathetic fibers and bone marrow noradrenaline levels rose (P<0.05, respectively), associated with a decrease of hematopoietic niche factors that promote stem cell quiescence. In mice with genetic deficiency of the ß3 adrenergic receptor, hematopoietic stem cells did not enter the cell cycle in increased numbers after tMCAO (naive control, 3.23±0.22; tMCAO, 3.74±0.33, P=0.51). CONCLUSIONS: Ischemic stroke activates hematopoietic stem cells via increased sympathetic tone, leading to a myeloid bias of hematopoiesis and higher bone marrow output of inflammatory Ly6C(high) monocytes and neutrophils.