Increased NETosis in heart failure patients is associated with macrophage activation towards a proinflammatory Mf1-like phenotype, with a statistically significant positive correlation (r = +0.79, p < 0.01) between proinflammatory macrophages and the proportion of NETosis.
Key Findings
Results
NETosis was substantially elevated in all heart failure groups compared to controls, with the highest proportion observed in inflammatory cardiomyopathy.
NETosis was quantified using CD66b+/citrullinated histone 3+/myeloperoxidase+ neutrophil markers in ventricular biopsies
Proportion of neutrophils undergoing NETosis: 49.4% [IQR 45–52] in inflammatory cardiomyopathy (InfCM), 45.3% [39–46] in ischemic cardiomyopathy (ICM), 41.5% [37–45] in dilated cardiomyopathy (DCM)
Control group showed only 4% [IQR 3.8–4.2] NETosis, markedly lower than all HF groups
Proinflammatory macrophages (Mf1) were significantly more abundant in all heart failure groups compared to controls, with the highest proportion in inflammatory cardiomyopathy.
Mf1 cells were identified as CD66b+/TNF-α+ macrophages
Proportion of Mf1: 78.5% [IQR 70–85] in InfCM, 53.1% [48.4–54.4] in DCM, 54.5% [51–60] in ICM
InfCM Mf1 proportion differed significantly from DCM and ICM (p < 0.05)
Control group Mf1 proportion was only 3% [IQR 1.6–5.5], differing significantly from all HF groups (p < 0.01)
Results
Anti-inflammatory macrophages (Mf2) were elevated in all heart failure groups compared to controls but did not differ significantly among heart failure subtypes.
Mf2 cells were identified as CD66b+/CD206+ macrophages
Proportion of Mf2: 20.9% [IQR 17.9–27.7] in DCM, 21.1% [IQR 17.8–22.8] in ICM, 23.2% [IQR 21.2–25.1] in InfCM
Control group Mf2 proportion was 6.5% [IQR 4.8–7.6], differing significantly from all HF groups (p < 0.01)
Mf2 proportions were similar across all three HF etiologies with no significant differences between groups
Results
There was a statistically significant positive correlation between proinflammatory macrophage (Mf1) proportion and NETosis proportion across heart failure patients.
Correlation coefficient r = +0.79, p < 0.01 between Mf1 and the proportion of NETosis
This positive correlation suggests that greater NETosis is associated with greater macrophage polarization toward a proinflammatory phenotype
No significant correlation was found between Mf2 and NETosis (r = -0.12, p = 0.28)
The contrasting correlations indicate specificity of the NETosis–Mf1 relationship over NETosis–Mf2
Conclusions
Accumulation of neutrophils and macrophages in the myocardium is a common feature of chronic heart failure regardless of its etiology.
All three heart failure etiologies (DCM, ICM, InfCM) showed elevated proportions of both NETosis and macrophage subpopulations compared to controls
The finding was consistent across dilated, ischemic, and inflammatory cardiomyopathy subtypes
Authors concluded that 'the accumulation of N and Mf cells is a typical feature of chronic myocardial inflammation in HF, regardless of its aetiology'
Ventricular biopsies were used for immunohistochemical quantification across all groups
What This Means
This research suggests that in patients with heart failure—whether caused by inflammation, blocked arteries, or enlarged heart muscle—a specific type of immune cell death called NETosis is occurring at much higher rates than in people without heart failure. NETosis happens when neutrophils (a type of white blood cell) release their DNA as sticky webs called neutrophil extracellular traps (NETs). In the heart tissue of heart failure patients, about 41–49% of neutrophils were undergoing this process, compared to only 4% in healthy control tissue. At the same time, the heart tissue of heart failure patients contained many more activated macrophages (another type of immune cell) that were behaving in an inflammatory, 'attack mode' manner.
The study found a strong statistical link between the amount of NETosis occurring and the number of pro-inflammatory macrophages present (correlation r = +0.79), suggesting these two processes may be fueling each other. By contrast, there was no meaningful link between NETosis and the anti-inflammatory type of macrophage, indicating that the relationship is specific to the harmful, inflammation-promoting immune response. Inflammatory cardiomyopathy showed the highest levels of pro-inflammatory macrophages (about 78%), while the proportion was somewhat lower but still elevated in ischemic and dilated cardiomyopathy (around 53–54%).
This research suggests that chronic inflammation driven by neutrophil NETosis and macrophage activation may be a shared feature of heart failure across different underlying causes, not just in inflammatory forms of the disease. Understanding this immune interaction could help explain why heart failure tends to worsen over time and might point toward new therapeutic targets aimed at reducing this inflammatory cycle in the heart. However, the study was small (7 patients per heart failure group and 5 controls), so larger studies are needed to confirm and extend these findings.
Kostin S, Cabrera-Fuentes H, Richter M, Krizanic F, Ritter O, Boisvert W, et al.. (2026). Increased NETosis in Patients With Heart Failure Is Associated With Macrophage Activation Towards a Proinflammatory Phenotype.. Journal of cellular and molecular medicine. https://doi.org/10.1111/jcmm.71306