Trajectories of Circulating Monocyte Subsets After ST-Elevation Myocardial Infarction During Hospitalization: Latent Class Growth Modeling for High-Risk Patient Identification

Macrophage heterogeneity in myocardial infarction: Evolution and implications for diverse therapeutic approaches

Given the extensive participation of myeloid cells (especially monocytes and macrophages) in both inflammation and resolution phases post-myocardial infarction (MI) owing to their biphasic role, these cells are considered as crucial players in the disease pathogenesis. Multiple studies have agreed on the significant contribution of macrophage polarization theory (M2 vs. M1) while determining the underlying reasons behind the observed biphasic effects; nevertheless, this simplistic classification attracts severe drawbacks. The advent of multiple advanced technologies based on OMICS platforms facilitated a successful path to explore comprehensive cellular signatures that could expedite our understanding of macrophage heterogeneity and plasticity. While providing an overall basis behind the MI disease pathogenesis, this review delves into the literature to discuss the current knowledge on multiple macrophage clusters, including the future directions in this research arena. In the end, our focus will be on outlining the possible therapeutic implications based on the emerging observations.

Monocyte heterogeneity in cardiovascular disease

Monocytes circulate the vasculature at steady state and are recruited to sites of inflammation where they differentiate into macrophages (MФ) to replenish tissue-resident MФ populations and engage in the development of cardiovascular disease (CVD). Monocytes display considerable heterogeneity, currently reflected by a nomenclature based on their expression of cluster of differentiation (CD) 14 and CD16, distinguishing CD14++CD16- classical (cMo), CD14++CD16+ intermediate (intMo) and CD14+CD16++ non-classical (ncMo) monocytes. Several reports point to shifted subset distributions in the context of CVD, with significant association of intMo numbers with atherosclerosis, myocardial infarction, and heart failure. However, clear indications of their causal involvement as well as their predictive value for CVD are lacking. As recent high-parameter cytometry and single-cell RNA sequencing (scRNA-Seq) studies suggest an even higher degree of heterogeneity, better understanding of the functionalities of these subsets is pivotal. Considering their high heterogeneity, surprisingly little is known about functional differences between MФ originating from monocytes belonging to different subsets, and implications thereof for CVD pathogenesis. This paper provides an overview of recent findings on monocyte heterogeneity in the context of homeostasis and disease as well as functional differences between the subsets and their potential to differentiate into MФ, focusing on their role in vessels and the heart. The emerging paradigm of monocyte heterogeneity transcending the current tripartite subset division argues for an updated nomenclature and functional studies to substantiate marker-based subdivision and to clarify subset-specific implications for CVD.

Patterns of Circulating Microbiota during the Acute Phase Following ST-Segment Elevation Myocardial Infarction Predict Long-Term Cardiovascular Events

Limited information exists regarding whether circulating microbiota could predict long-term clinical outcomes following ST-segment elevation myocardial infarction (STEMI). A total of 244 consecutive patients with STEMI were followed for 2.8 years, and 64 first major adverse cardiovascular events (MACEs) were recorded. Both microbiota abundance [Corynebacterium tuberculostearicum (HR, 1.28; 95% CI, 1.03-1.58) and Staphylococcus aureus (S. aureus) (HR, 1.16; 95% CI, 1.02-1.33) ] and microbiota clusters (Cluster 2 versus Cluster 1: HR, 1.84; 95% CI, 1.04-3.27) could independently predict MACE. Furthermore, a model based on established independent predictors alone was significantly improved by the addition of different microbiota patterns. In addition, CD14⁺⁺CD16⁺ monocytes (Mon2) had a significant mediation effect on the microbiota patterns → MACE association. The present study demonstrated that the abundance and clusters of circulating microbiota are associated with future adverse cardiovascular events independent of traditional risk factors, which were partially mediated by an increase in Mon2.

Synergistic role of circulating CD14++CD16+ monocytes and fibrinogen in predicting the cardiovascular events after myocardial infarction

BACKGROUND

Monocytes and fibrinogen (FIB) play important roles in driving acute and reparative inflammatory pathways after myocardial infarction (MI). In humans, there are three subsets of monocytes, namely, CD14++CD16- (Mon1), CD14++CD16+ (Mon2), and CD14+CD16++ (Mon3). During the inflammatory response, monocyte subsets express high levels of integrin α_M β₂ and protease-activated receptors 1 and 3 to interact with FIB.

HYPOTHESIS

However, whether there is a synergistic role of FIB combined with Mon2 counts in prioritizing patients at high risk of future major adverse cardiovascular events (MACEs) after MI remains unknown.

METHODS

The MI patients who treated with primary percutaneous coronary intervention were enrolled. MI patients were categorized into four groups, that is, low FIB/low Mon2, low FIB/high Mon2, high FIB/low Mon2, and high FIB/high Mon2, according to cutoff values of 3.28 g/L for FIB and 32.20 cells/μL for Mon2. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the risk of MACEs of MI patients during a median follow-up of 2.7 years. Mediating effects of high FIB levels and MACEs associated with high monocyte subsets were calculated by mediation analysis.

RESULTS

High FIB/high Mon2 group had the highest risk of MACEs during a median follow-up of 2.7 years. Moreover, mediation analysis showed that a high FIB level could explain 24.9% (p < .05) of the increased risk of MACEs associated with Mon2.

CONCLUSION

This work provides evidence indicating the translational potential of a synergistic role of FIB combined with Mon2 in prioritizing patients at high risk of future MACEs after MI.

Dynamic changes of monocytes subsets predict major adverse cardiovascular events and left ventricular function after STEMI

We explored how dynamic changes in monocyte subset counts (as opposed to static values to specific time points), and their phagocytic and NFκB activity relate to major adverse cardiovascular events (MACE) and left ventricular ejection fraction (LVEF) in patients with ST-elevation myocardial infarction (STEMI). Changes in counts, phagocytic activity and intracellular levels of inhibitory κB kinase β (IKKβ) (a marker of NFκB activity) of monocyte subsets (CD14⁺⁺CD16^-CCR2⁺ [Mon1], CD14⁺⁺CD16⁺CCR2⁺ [Mon2] and CD14⁺CD16⁺⁺CCR2^- [Mon3]) were measured by flow cytometry in patients with STEMI at baseline, and again after one week, two weeks, and one month. LVEF was measured by echocardiography at baseline and six months after STEMI. Baseline data included 245 patients (mean ± SD age 60 ± 12 years; 22% female), who were followed for a median of 46 (19-61) months. Multivariate Cox regression demonstrated that more prominent dynamic reduction in Mon2 by week 1 (n = 37) was independently associated with fewer MACE (HR 0.06, 95% CI 0.01-0.55, p = 0.01). Also, less prominent reduction in Mon2 at month 1 (n = 24) was independently predictive of 6-month LVEF. None of the other dynamic changes in monocyte subsets were associated with changes in survival from MACE. Neither phagocytic activity nor IKKβ were associated with survival for each monocyte subset. We showed how distinct pattern of dynamic changes in Mon2 are related to both MACE risk and recovery of cardiac contractility. Further research is needed to understand the mechanism of the monocyte effect and possibilities of their pharmacological manipulation.

Phenotypic and Functional Heterogeneity of Monocyte Subsets in Chronic Heart Failure Patients

Chronic heart failure (CHF) results when the heart cannot consistently supply the body's tissues with oxygen and required nutrients. CHF can be categorized as heart failure (HF) with preserved ejection fraction (HFpEF) or HF with reduced ejection fraction (HFrEF). There are different causes and mechanisms underlying HF pathogenesis; however, inflammation can be regarded as one of the factors that promotes both HFrEF and HFpEF. Monocytes, a subgroup of leukocytes, are known to be cellular mediators in response to cardiovascular injury and are closely related to inflammatory reactions. These cells are a vital component of the immune system and are the source of macrophages, which participate in cardiac tissue repair after injury. However, these monocytes are not as homogenous as thought and can present different functions under different cardiovascular disease conditions. In addition, there is still an open question regarding whether the functions of monocytes and macrophages should be regarded as causes or consequences in CHF development. Therefore, the aim of this work was to summarize current studies on the functions of various monocyte subsets in CHF with a focus on the role of a certain monocyte subset in HFpEF and HFrEF patients, as well as the subsets' relationship to inflammatory markers.

Modelling of longitudinal data to predict cardiovascular disease risk: a methodological review

OBJECTIVE

The identification of methodology for modelling cardiovascular disease (CVD) risk using longitudinal data and risk factor trajectories.

METHODS

We screened MEDLINE-Ovid from inception until 3 June 2020. MeSH and text search terms covered three areas: data type, modelling type and disease area including search terms such as "longitudinal", "trajector*" and "cardiovasc*" respectively. Studies were filtered to meet the following inclusion criteria: longitudinal individual patient data in adult patients with ≥3 time-points and a CVD or mortality outcome. Studies were screened and analyzed by one author. Any queries were discussed with the other authors. Comparisons were made between the methods identified looking at assumptions, flexibility and software availability.

RESULTS

From the initial 2601 studies returned by the searches 80 studies were included. Four statistical approaches were identified for modelling the longitudinal data: 3 (4%) studies compared time points with simple statistical tests, 40 (50%) used single-stage approaches, such as including single time points or summary measures in survival models, 29 (36%) used two-stage approaches including an estimated longitudinal parameter in survival models, and 8 (10%) used joint models which modelled the longitudinal and survival data together. The proportion of CVD risk prediction models created using longitudinal data using two-stage and joint models increased over time.

CONCLUSIONS

Single stage models are still heavily utilized by many CVD risk prediction studies for modelling longitudinal data. Future studies should fully utilize available longitudinal data when analyzing CVD risk by employing two-stage and joint approaches which can often better utilize the available data.

Admission Low-Density Lipoprotein Cholesterol Stratified by Circulating CD14++CD16+ Monocytes and Risk for Recurrent Cardiovascular Events Following ST Elevation Myocardial Infarction: Lipid Paradox Revised

Lower level of low-density lipoprotein cholesterol (LDL-C) is paradoxically associated with increased mortality in ST elevation myocardial infarction (STEMI) patients. The underlying mechanism remains unclear. In a cohort of 220 de novo STEMI patients receiving timely primary percutaneous coronary intervention, admission LDL-C was negatively associated with circulating CD14++CD16+ monocyte counts. Moreover, admission LDL-C < 85 mg/dL was associated with increased risk for major adverse cardiovascular events (MACE) during a median follow-up of 2.7 years. After categorizing the patients according to the cutoff values of 85 mg/dL for LDL-C and the median for CD14++CD16+ monocytes, low LDL-C-associated MACE risk was only observed in those with high CD14++CD16+ monocyte counts (low LDL-C/high CD14++CD16+ monocytes vs. low LDL-C/low CD14++CD16+ monocytes: hazard ratio 5.38, 95% confidence interval 1.52 to 19.06, P = 0.009). This work provided the proof-of-principle evidence indicating a role of CD14++CD16+ monocytes in risk stratification of STEMI patients presenting with low LDL-C level. Graphical abstract.

Monocyte subsets predict mortality after cardiac arrest

After successful cardiopulmonary resuscitation (CPR), many patients show signs of an overactive immune activation. Monocytes are a heterogeneous cell population that can be distinguished into 3 subsets by flow cytometry (classical monocytes [CM: CD14⁺⁺CD16^‐], intermediate monocytes [IM: CD14⁺⁺CD16⁺CCR2⁺] and non‐classical monocytes [NCM: CD14⁺CD16⁺⁺CCR2^‐]). Fifty‐three patients admitted to the medical intensive care unit (ICU) after cardiac arrest were included. Blood was taken on admission and after 72 h. The primary endpoint of this study was survival at 6 months and the secondary endpoint was neurological outcome as determined by cerebral performance category (CPC)‐score at 6 months. Median age was 64.5 (49.8‐74.3) years and 75.5% were male. Six‐month mortality was 50.9% and survival with good neurological outcome was 37.7%. Monocyte subset distribution upon admission to the ICU did not differ according to survival. Seventy‐two hours after admission, patients who died within 6 months showed a higher percentage of the pro‐inflammatory subset of IM (8.3% [3.8‐14.6]% vs. 4.1% [1.5–8.2]%; P = 0.025), and a lower percentage of CM (87.5% [79.9–89.0]% vs. 90.8% [85.9–92.7]%; P = 0.036) as compared to survivors. In addition, IM were predictive of outcome independent of time to ROSC and witnessed cardiac arrest, and correlated with CPC‐score at 6 months (R = 0.32; P = 0.043). These findings suggest a possible role of the innate immune system in the pathophysiology of post cardiac arrest syndrome.

Circulating monocyte subsets and heart failure prognosis

Monocytes are a heterogeneous population of effector cells with key roles in tissue integrity restoration and maintenance. Here, we explore the association of monocyte subsets and prognosis in patients with ambulatory heart failure (HF). Monocyte subsets were classified as classical (CD14++/CD16-), intermediate (CD14++/CD16+), or non-classical (CD14+/CD16++). Percentage distribution and absolute cell count were assessed in each subset, and multivariable Cox regression analyses were performed with all-cause death, HF-related hospitalization, and the composite end-point of both as dependent variables. 400 patients were consecutively included (72.8% male, age 69.4±12.2 years, 45.5% from ischemic aetiology, left ventricle ejection fraction (LVEF) 41.6% ±14.5, New York Heart Association (NYHA) class II 62.8% and III 30.8%). During a mean follow-up of 2.6±0.9 years, 107 patients died, 99 had a HF-related hospitalization and 160 suffered the composite end-point of all-cause death or HF-related hospitalization. Monocyte subsets assessed in percentages were not independently associated to any of the end-points. When considering number of cells/μL, intermediate subset was independently associated with an increase of all-cause death (HR 1.25 [95% CI 1,02-1.52], p = 0.03), and the composite end-point HR 1.20 [95% CI 1,03-1.40], p = 0.02). The presented findings show that absolute cell count of monocyte subsets was preferred over monocyte percentage for prognosis stratification for outpatients with HF. The intermediate monocyte subset provides information on increased risk of all-cause death and the composite end-point.

The relationships among monocyte subsets, miRNAs and inflammatory cytokines in patients with acute myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) causes irreversible myocardial damage and release of inflammatory mediators, including cytokines, chemokines and miRNAs. We aimed to investigate changes in the levels of cytokines (IL-6, TNF-α and IL-10), miRNAs profiles (miR-146 and miR-155) and distribution of different monocyte subsets (CD14++CD16-, CD14++CD16+, CD14+CD16++) in the acute and post-healing phases of AMI.

METHODS

In eighteen consecutive AMI patients (mean age 56.78 ± 12.4 years, mean left ventricle ejection fraction - LVEF: 41.9 ± 9.8%), treated invasively, monocyte subsets frequencies were evaluated (flow cytometry), cytokine concentrations were analyzed (ELISA) as well as plasma miRNAs were isolated twice - on admission and after 19.2 ± 5.9 weeks of follow-up. Measurements were also performed among healthy volunteers.

RESULTS

AMI patients presented significantly decreased frequencies of classical cells in comparison to healthy controls (median 71.22% [IQR: 64.4-79.04] vs. 84.35% [IQR: 81.2-86.7], p = 0.001) and higher percent of both intermediate and non-classical cells, yet without statistical significance (median 6.54% [IQR: 5.14-16.64] vs. 5.87% [IQR: 4.48-8.6], p = 0.37 and median 5.99% [IQR: 3.39-11.5] vs. 5.26% [IQR: 3.62-6.2], p = 0.42, respectively). In AMI patients both, analyzed plasma miRNA concentrations were higher than in healthy subjects (miR-146: median 5.48 [IQR: 2.4-11.27] vs. 1.84 [IQR: 0.87-2.53], p = 0.003; miR-155: median 25.35 [IQR: 8.17-43.15] vs. 8.4 [IQR: 0.08-16.9], p = 0.027, respectively), and returned back to the values found in the control group in follow-up. miR-155/miR-146 ratio correlated with the frequencies of classical monocytes (r=0.6, p = 0.01) and miR-155 correlated positively with the concentration of inflammatory cytokines - IL-6 and TNF-α.

CONCLUSIONS

These results may suggest cooperation of both pro-inflammatory and anti-inflammatory signals in AMI in order to promote appropriate healing of the infarcted myocardium.