The study, published in the Journal of Molecular Medicine, was led by Alejandro Silva-Palacios, Alejandra María Zúñiga-Muñoz, and Cecilia Zazueta of the National Institute of Cardiology Ignacio Chávez in Mexico City, together with collaborators at the National Autonomous University of Mexico and Tecnológico de Monterrey. The researchers set out to test whether cannabidiol, commonly abbreviated as CBD, could protect the heart in an animal model that closely mimics the human condition. They induced HFpEF in mice by combining a high-fat diet with L-NAME, a compound that inhibits nitric oxide synthesis and drives the nitrosative stress considered central to the disease. Over eight weeks, the animals developed the hallmark features of HFpEF: cardiac fibrosis, diastolic dysfunction, and systemic metabolic and inflammatory disturbances. CBD was then administered subcutaneously every three days, a dosing interval chosen to maintain sustained exposure to the compound.

The results were nuanced but striking. CBD did not shrink the enlarged, hypertrophied hearts of the diseased animals; cardiac hypertrophy persisted despite treatment. However, the compound produced meaningful improvements where they mattered most for HFpEF patients. Treated animals showed reduced cardiac fibrosis, the stiffening scar tissue that prevents the heart muscle from relaxing, and their diastolic function improved measurably. The researchers assessed hemodynamic performance using invasive pressure-volume loop analysis, the gold standard for evaluating how the ventricle fills and ejects blood, and complemented these measurements with histological examination and markers of oxidative stress. The improvement in filling dynamics, rather than pumping strength, is precisely the kind of benefit that HFpEF patients need, since their hearts fail not because they pump too weakly but because they cannot relax enough to refill.

To understand how CBD achieved these effects, the team turned their attention to cellular senescence, the state in which cells stop dividing but refuse to die, instead lingering in tissues and secreting a toxic cocktail of inflammatory molecules. This senescence-associated secretory phenotype, or SASP, has emerged as a key driver of age-related diseases, and growing evidence links it to heart failure. In the HFpEF mice, senescent cells had accumulated in the heart, and circulating cytokine levels were elevated, consistent with a body-wide SASP-driven inflammatory state. CBD treatment markedly reduced the accumulation of these senescent cells and lowered systemic cytokine levels. The finding suggests that CBD may act as a partial senotherapeutic, clearing or calming the aged cells that fuel chronic inflammation in the failing heart.

The second major target was the NLRP3 inflammasome, a molecular machine inside immune and cardiac cells that, when activated, triggers caspase-1 and the release of potent proinflammatory cytokines such as interleukin-1 beta. NLRP3 activation has been implicated in cardiac remodeling, pulmonary artery changes, and general inflammation in HFpEF, and pharmacological inhibitors of this inflammasome have already shown benefit in mouse models of the disease. In the current study, CBD suppressed the NLRP3-mediated proinflammatory state, adding to a growing body of evidence that the compound can dampen inflammasome signaling. Previous work had shown that CBD inhibits NLRP3 activation in human monocytes through modulation of the P2X7 receptor, and that cannabinoids can attenuate cytokine storms driven by inflammasome pathways. The new findings extend this anti-inflammatory repertoire into the HFpEF setting.

Perhaps the most novel contribution of the study lies in its third focus: the mitochondria-endoplasmic reticulum contact sites, abbreviated MERCSs. These are microscopic junctions where the membranes of mitochondria, the cell’s power plants, and the endoplasmic reticulum, its protein-folding and calcium-storage factory, come into close apposition. At these contact points, the two organelles exchange calcium, lipids, and stress signals, coordinating everything from energy metabolism to cell death decisions. When MERCSs become excessive or disorganized, calcium overload and mitochondrial destabilization can activate the NLRP3 inflammasome, linking organelle architecture directly to inflammation. Using transmission electron microscopy, immunofluorescence, and RT-qPCR, the researchers found that in HFpEF the integrity of these contact sites was compromised, and that CBD treatment preserved inter-organelle distance and MERCSs structure.

This is the first demonstration, according to the authors, that CBD modulates MERCSs communication to regulate senescence and inflammation in HFpEF. The finding ties together threads that had previously run in parallel. Earlier work from the same group had shown that senotherapy in obese rats could act through a MERCSs/Nrf2 interaction, and other studies had established that disrupted sarcoplasmic reticulum-mitochondrial contacts underlie contractile dysfunction in atrial fibrillation, while enhanced tethering can trigger adaptive cardiac remodeling. In diabetes, hyperglycemia-driven promotion of mitochondria-associated endoplasmic reticulum membranes contributes to cardiomyopathy, and in aged hearts, defective calcium exchange between these organelles impairs function. By preserving the geometry of these junctions, CBD appears to prevent the calcium mishandling and mitochondrial stress that ignite inflammasome activation, thereby interrupting a vicious cycle in which organelle damage feeds inflammation, which in turn accelerates cellular aging.

The implications extend beyond the laboratory. HFpEF accounts for roughly half of all heart failure cases, and its burden is growing with the obesity and diabetes epidemics. Current treatment options remain limited, with recent trials of sodium-glucose cotransporter-2 inhibitors offering only partial benefit, and one such agent, empagliflozin, has been shown to protect against HFpEF partly by inhibiting a senescence-associated signaling axis. Pharmacological clearance of senescent cells has independently been shown to reduce inflammation, endothelial damage, and cardiac fibrosis in HFpEF models. The convergence of these findings suggests that targeting the biology of aging itself—senescent cells, their secretory products, and the organelle networks that control cellular stress—may be a viable therapeutic strategy for a disease that has defied conventional approaches.

CBD brings its own compelling profile to this strategy. Unlike tetrahydrocannabinol, it does not produce intoxication, and it has already been approved for certain forms of epilepsy, giving clinicians experience with its safety profile. Prior animal studies have shown that CBD attenuates cardiac dysfunction, oxidative stress, fibrosis, and inflammatory signaling in diabetic cardiomyopathy, prevents heart failure dysfunction through preservation of mitochondrial function and calcium handling, and promotes cardiomyocyte proliferation after myocardial infarction. A clinical trial, the ARCHER study, is currently evaluating CBD’s impact on myocardial recovery in patients with acute myocarditis. The new HFpEF findings add another potential indication to this expanding list, though the authors caution that the signaling pathways connecting MERCSs preservation to reduced senescence and inflammation still need to be fully characterized.

Important questions remain before CBD can be considered a treatment for HFpEF. The study was conducted in mice, and the dose, route, and timing of administration would need careful translation to humans. The failure to reduce hypertrophy suggests that CBD addresses some but not all of the disease’s pathological drivers, and it is unclear whether starting treatment earlier or later would change the outcome. Nevertheless, by identifying premature senescence, NLRP3-mediated inflammation, and MERCSs integrity as linked, druggable targets in HFpEF, the Mexican team has offered both a mechanistic explanation for CBD’s cardioprotective effects and a roadmap for the next generation of experiments. For a disease that affects millions and has resisted nearly every therapeutic attempt, the idea that a well-tolerated plant-derived compound might restore youthful communication between a cell’s organelles and quiet the inflammatory noise of aging tissue is a prospect worth watching closely.

Subject of Research: The cardioprotective effects of cannabidiol in heart failure with preserved ejection fraction through modulation of cellular senescence, NLRP3 inflammation, and mitochondria-endoplasmic reticulum contact sites.

Article Title: Prospective associations of premature senescence, inflammation, and MERCSs in the cardioprotective effect of CBD in HFpEF

Article References: Silva-Palacios, A., Zúñiga-Muñoz, A. M., Soria-Castro, E., Álvarez-León, E., García-Niño, W. R., Navarrete-Anastasio, G., Raza, D., Aparicio-Trejo, O. E., Ramírez-Carreto, R. J., Salas-Venegas, V., Chavarría, A., Maldonado-Ruíz, R. A., Alves-Figueiredo, H., García-Rivas, G., & Zazueta, C. (2026). Prospective associations of premature senescence, inflammation, and MERCSs in the cardioprotective effect of CBD in HFpEF. Journal of Molecular Medicine, 104(1), Article 109. https://doi.org/10.1007/s00109-026-02715-4

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02715-4

Keywords: heart failure, HFpEF, cannabidiol, cellular senescence, SASP, NLRP3 inflammasome, MERCSs, mitochondria, endoplasmic reticulum, cardiac fibrosis, diastolic dysfunction, inflammation

The research, led by Mathieu Kruska and Volker Liebe of the University Medical Centre Mannheim at Heidelberg University together with colleagues across several German institutions, enrolled eighty-three patients with symptomatic atrial fibrillation who were scheduled for catheter ablation at a single center between October 2020 and March 2022. The cohort had a median age of seventy-two years, and just over one-third of participants were women. Most patients, eighty-two percent, suffered from the paroxysmal form of the arrhythmia, in which episodes come and go rather than persist continuously. Their symptom burden was substantial: the median European Heart Rhythm Association symptom score was three, indicating moderate to severe symptoms, and their average score on a validated quality of life questionnaire was only sixty out of a possible one hundred, underscoring how heavily the condition weighed on daily living.

What sets this study apart is its multimodal approach. Before ablation, each patient underwent pulse wave analysis using an oscillometric device called VascAssist2.0, which measures blood pressure waveforms at the arm and uses a mathematical model of the arterial system to derive a suite of vascular parameters. These include brachial and central blood pressures, pulse wave velocity, augmentation pressure, augmentation index, left ventricular ejection time, and model-based indices of arterial stiffness and vascular resistance. In parallel, patients received transthoracic echocardiography to assess cardiac structure and function, a twelve-lead electrocardiogram, laboratory testing including the heart failure biomarker NT-proBNP, and a detailed quality of life assessment using the AFEQT questionnaire, a disease-specific instrument covering twenty items that captures how atrial fibrillation affects symptoms, daily activities, and treatment satisfaction.

The correlations that emerged were striking. Lower AFEQT scores, indicating worse quality of life, correlated strongly with higher vascular resistance, with a correlation coefficient of minus 0.64, and with increased arterial stiffness, at minus 0.62, both highly statistically significant. Elevated central systolic blood pressure, the pressure actually experienced by the heart and brain rather than the arm, also tracked with poorer quality of life at minus 0.38. On the cardiac side, the strongest association of all was found with reduced left ventricular ejection fraction below fifty percent, which correlated at minus 0.74 with AFEQT scores. Diastolic dysfunction, the inability of the heart’s main pumping chamber to relax and fill properly, correlated at minus 0.34, while a clinical diagnosis of heart failure correlated at minus 0.39 and logarithmically transformed NT-proBNP levels at minus 0.38. Patient-reported quality of life also aligned closely with physician-assessed symptom classification, with EHRA scores correlating at minus 0.91 with AFEQT scores, a reassuring sign that the two instruments are measuring the same underlying phenomenon from different angles.

To understand why stiff arteries should make an abnormal heart rhythm feel worse, the authors turn to the concept of ventricular-arterial and arterial-atrial coupling. When the large arteries lose their elastic cushioning, every heartbeat travels through the vascular tree faster, and reflected pressure waves return to the heart earlier in the cardiac cycle. This raises the central systolic pressure the left ventricle must pump against, increasing afterload and impairing diastolic relaxation. Higher pressures then back up into the left atrium, promoting structural and functional remodeling of that chamber, a process central to atrial cardiomyopathy. The resulting atrial substrate not only facilitates the persistence of atrial fibrillation but may also blunt the atrium’s reservoir function, intensifying symptoms such as fatigue and breathlessness. The same hemodynamic cascade is considered a central driver of heart failure with preserved ejection fraction, tying together several threads of cardiovascular medicine in a single mechanistic framework.

Intriguingly, one conventional measure of arterial health did not follow this pattern. Aortic pulse wave velocity, widely regarded as the reference standard for large-artery stiffness, was within age-adapted reference values in the cohort at a median of 8.6 meters per second and did not correlate significantly with quality of life scores. The authors suggest that pulse wave velocity predominantly reflects the structural properties of the aorta and vascular aging, whereas the model-derived vascular resistance, arterial stiffness index, and central systolic blood pressure may better capture dynamic functional afterload and ventricular-arterial coupling. Those fluctuating hemodynamic loads, they argue, may be more directly connected to the day-to-day symptoms of palpitations, dyspnea, and exercise intolerance than a static measure of aortic structure. Notably, the pulse wave measurements proved robust regardless of rhythm: over ninety percent of patients were in sinus rhythm at the time of testing, and no significant differences were found between measurements taken during sinus rhythm and those taken during atrial fibrillation.

The study also highlights the tangled relationship between atrial fibrillation and heart failure, two conditions that each fuel the other’s progression. Thirty percent of the cohort had heart failure, forty-two percent showed echocardiographic evidence of diastolic dysfunction, and elevated NT-proBNP levels were strongly associated with poorer quality of life. Disentangling which symptoms stem from the arrhythmia and which from the failing heart is notoriously difficult, since dyspnea and fatigue dominate both. Interestingly, heart failure with reduced ejection fraction was associated with impaired quality of life in this analysis, whereas the preserved-ejection-fraction phenotype did not reach statistical significance. That observation echoes earlier findings suggesting that the symptomatic benefits of ablation may be attenuated in patients with heart failure with preserved ejection fraction, possibly because their symptoms are driven more by the stiff, non-compliant cardiovascular system than by the arrhythmia itself.

Beyond the vascular and cardiac measurements, broader comorbidity burden left its mark. Coronary artery disease, older age, arterial hypertension, higher total and LDL cholesterol, and reduced kidney function all correlated inversely with quality of life scores, as did higher CHA2DS2-VASc and HAS-BLED risk scores. Taken together, these associations paint quality of life in atrial fibrillation as a barometer of overall cardiovascular health rather than a simple readout of arrhythmia burden. This aligns with large registry data linking cardiovascular comorbidities to worse patient-reported outcomes, and it reinforces current European Society of Cardiology guidelines that emphasize comprehensive management of risk factors alongside rhythm control strategies.

The authors are careful to frame their findings appropriately. The study was exploratory and hypothesis-generating, conducted at a single center with a modest sample size and no formal a priori power calculation. Because many univariate correlations were performed without adjustment for multiple testing, the reported associations should be interpreted descriptively, and the absence of multivariable modeling means the independent contribution of each vascular parameter cannot be isolated. The single-time-point, observational design precludes any causal inference, and recruitment during the COVID-19 pandemic added logistical strain to elective procedural volumes. Whether pulse wave analysis-derived vascular phenotyping genuinely adds predictive value beyond established clinical evaluation will require prospective validation in larger cohorts.

Even with those caveats, the implications are compelling. If stiff arteries, elevated central pressures, and weakened or stiffened heart muscle account for a substantial share of the suffering attributed to atrial fibrillation, then measuring them before ablation could help clinicians identify patients whose symptoms reflect more than the arrhythmia alone, and tailor treatment accordingly, with intensified blood pressure control, vascular risk management, and heart failure therapy running alongside rhythm control. For patients, the message is equally resonant: the health of the arteries is inseparable from the experience of the arrhythmia. As the authors conclude, reduced quality of life in symptomatic atrial fibrillation reflects a complex interplay between vascular function, myocardial performance, and the rhythm disorder itself, and understanding that interplay may ultimately determine who truly benefits from a procedure that millions pin their hopes on.

Subject of Research: Associations between vascular and cardiac functional parameters and quality of life in atrial fibrillation patients scheduled for catheter ablation

Article Title: Impact of vascular and cardiac parameters on quality of life in patients undergoing catheter ablation for atrial fibrillation

Article References: Kruska, M., Liebe, V., Fastner, C., Kranert, M., Jehle, M., Derda, A., Schumacher, G., Akin, I., Duerschmied, D., & Hohneck, A. (2026). Impact of vascular and cardiac parameters on quality of life in patients undergoing catheter ablation for atrial fibrillation. Clinical Research in Cardiology. https://doi.org/10.1007/s00392-026-03005-2

Image Credits: AI Generated

DOI: 10.1007/s00392-026-03005-2

Keywords: atrial fibrillation, catheter ablation, quality of life, arterial stiffness, vascular resistance, pulse wave analysis, echocardiography, NT-proBNP, heart failure, central blood pressure, AFEQT, diastolic dysfunction

The distinction between active relaxation and passive stiffness is central to understanding why the review’s cautious conclusion matters. Active relaxation is an energy-consuming process: after each heartbeat, calcium must be pumped back into the sarcoplasmic reticulum by SERCA2a, the sarco/endoplasmic reticulum calcium ATPase, and any residual calcium bound to the contractile proteins must be released so that cross-bridges detach and force declines. If calcium removal slows or myofilaments remain activated longer than they should, the ventricle begins to fill while it is still generating tension, and filling pressures rise. Passive stiffness, by contrast, is a property of the relaxed cell itself, determined largely by titin, the giant spring-like protein that spans from the Z-disc to the M-band of the sarcomere. Titin’s stiffness can be tuned by isoform switching, with the more compliant N2BA isoform giving way to the stiffer N2B isoform in some settings, and by phosphorylation of its elastic PEVK and N2B segments through kinases such as protein kinase A and protein kinase G. Hypophosphorylation of titin, oxidative modifications, and shifts in isoform ratio have all been proposed as mechanisms contributing to the elevated diastolic stiffness characteristic of HFpEF.

What makes the review’s framework particularly useful is its insistence on formal statistical testing of sex as a modifier. In experimental biology, it is common to report that females and males differ in some measured quantity, but a simple difference in a single endpoint does not establish that sex modifies the disease process. A true modifier effect requires a statistically significant interaction term, either sex by disease or sex by target, demonstrating that the effect of disease, or the response to an intervention, is itself different between the sexes. This is a much higher bar than demonstrating a baseline difference, and it is the appropriate standard when the clinical question is whether men and women should be classified or treated differently. By applying this standard systematically across the literature on calcium handling, myofilament function, titin, and mitochondrial bioenergetics, the authors converted a sprawling and often contradictory body of work into a much smaller set of defensible claims.

The result is striking in its sparseness. Among all the studies surveyed, the late sodium current emerged as the only active-relaxation-related cellular endpoint with a reported formal sex by disease interaction. The late sodium current is a small, sustained inward flow of sodium ions during the plateau phase of the cardiac action potential, and its pathological augmentation in disease states is thought to drive sodium and calcium overload through the sodium-calcium exchanger, contributing to diastolic tension and arrhythmogenic risk. The drug ranolazine, which suppresses the late current, has been tested clinically in the RALI-DHF trial for diastolic heart failure, making this target one of the few with a direct translational thread running from cellular electrophysiology to human intervention. Yet even here, the review notes that the reported sex interaction was electrophysiological rather than mechanical: the difference appeared in ionic current measurements, not in a demonstrated difference in how relaxation or stiffness responded. Without that mechanical link, the interaction remains an observation about membrane physiology rather than a guide to therapy.

The titin story illustrates a different kind of evidentiary gap. There is little doubt that titin modifications can change diastolic properties; interventions that alter titin phosphorylation or isoform expression have modified passive stiffness and filling in several HFpEF-like animal models, including models combining hypertension and metabolic stress such as the ZSF1 hybrid rat and models using L-NAME to induce nitric oxide synthase inhibition. Protein kinase G signaling, which phosphorylates titin and reduces its stiffness, has been a particularly attractive mechanistic target because it connects nitric oxide biology, cGMP signaling, and the phosphodiesterase pathways that have been explored pharmacologically in HFpEF. But the review’s systematic search found no experiment in which an independent laboratory replicated a sex-modified mechanical response to a titin-directed intervention. In other words, titin is clearly modifiable, and titin stiffness is clearly relevant to HFpEF, but the claim that women’s titin behaves differently from men’s titin in disease, in a way that would justify sex-specific treatment, has not been demonstrated under conditions that meet modern standards of rigor.

Mitochondrial bioenergetics and redox state occupy the connective position in this framework, and the review treats them accordingly. The energetic cost of relaxation is substantial: SERCA2a consumes a large fraction of the ATP generated by the cardiomyocyte, and any impairment of oxidative phosphorylation, NAD+ availability, or mitochondrial quality control can slow calcium reuptake and prolong contraction. Oxidative stress adds a second layer of vulnerability, because reactive oxygen species can modify ryanodine receptors, promote calcium leak, stiffen titin through oxidative cross-linking, and alter myofilament protein function. Pathways such as sirtuin 3, which depends on NAD+ and regulates mitochondrial protein acetylation, and calcium/calmodulin-dependent protein kinase II, which links calcium handling to oxidative stress, have each been implicated in diastolic dysfunction in experimental models. Interventions aimed at restoring NAD+ pools or reducing oxidative damage have improved diastolic phenotypes in some HFpEF-like settings. Yet here again, the review found no replicated demonstration that these bioenergetic interventions produce different mechanical benefits in females versus males, despite the plausible biological reasons to expect such differences, including known sex differences in mitochondrial function, estrogen-dependent regulation of energetics, and redox enzyme expression.

The confounding landscape surrounding this literature is unusually dense, and the review is careful to enumerate it. Findings varied with the animal model employed, the genetic strain, the age of the animals, their reproductive state, the specific disease driver used to induce the HFpEF phenotype, the stage of disease at which measurements were made, and the assay used to assess function. Each of these variables can plausibly interact with sex. Reproductive state is especially important in females, since estrogen status influences calcium handling proteins, mitochondrial enzymes, and titin phosphorylation, and ovariectomy versus intact status can change experimental outcomes. Age interacts with both sex and disease, because HFpEF is predominantly a disease of older adults and many animal models study young animals. Disease drivers matter because hypertension-driven, metabolic-driven, and anemia-driven HFpEF models produce overlapping but distinct cellular phenotypes. A sex difference observed in one combination of these variables may simply not generalize to another, which is precisely the pattern the review documents.

Human evidence, which would ideally anchor the field, is itself fragmented. Studies of ventricular tissue from patients with HFpEF have documented slowed active relaxation, elevated passive stiffness, and metabolic remodeling, including shifts in substrate utilization and mitochondrial protein expression. But these findings come from separate cohorts, often with small sample sizes, and the role of sex within each finding remains unresolved. Human myocardial tissue is difficult to obtain, typically available only from surgical procedures such as valve replacement or from transplant and autopsy material, and the underlying disease etiologies of donors vary widely. Direct comparisons of women and men using the same cellular assays on matched tissue are rare. This means that even the well-documented cellular abnormalities of HFpEF cannot currently be assigned a sex-specific prevalence or magnitude with confidence.

The review also draws a useful methodological distinction among the kinds of comparisons that would actually advance the field. One question is whether disease affects females and males differently, which requires comparing each sex against its own healthy control. A second question is whether a molecular target functions differently within diseased hearts of each sex, which requires testing the target’s contribution in both sexes under disease conditions. A third question is whether any observed difference is specific to disease rather than a baseline sex difference that exists independently of pathology. Many published studies conflate these questions, reporting sex differences without the appropriate controls to determine what kind of difference has been found. Prespecifying sex comparisons and linking them to a relevant functional endpoint, such as relaxation kinetics or passive force, would allow future studies to distinguish genuine modifier effects from incidental observations.

The clinical implications of this cautious conclusion deserve emphasis. If sex alone cannot define calcium-dominant or titin-dominant HFpEF endotypes, then treatment selection based on a patient’s sex would currently lack a mechanistic foundation. This does not mean sex is irrelevant to HFpEF; the epidemiological preponderance of women, differences in ventricular remodeling patterns, and known hormonal influences on cardiovascular physiology all remain real and clinically important. It means instead that the cellular mechanisms underlying any sex-related clinical differences have not been pinned down with the specificity needed to guide endotyping. The practical path forward suggested by the review is to treat sex as a hypothesis-generating variable to be tested in defined experimental and clinical settings, rather than as a classification tool. Until replicated, sex-stratified, mechanically anchored evidence accumulates, the heterogeneous reality of HFpEF, in which multiple cellular defects coexist and vary with context, remains the best available description of the disease for both women and men.

Subject of Research: Sex differences in cardiomyocyte relaxation mechanisms in heart failure with preserved ejection fraction

Article Title: Evaluating sex as a modifier of cardiomyocyte relaxation in heart failure with preserved ejection fraction: calcium handling, titin, and bioenergetics

Article References: Wang, B., & Dai, X.-C. (2026). Evaluating sex as a modifier of cardiomyocyte relaxation in heart failure with preserved ejection fraction: calcium handling, titin, and bioenergetics. Biology of Sex Differences. https://doi.org/10.1186/s13293-026-00993-8

Image Credits: AI Generated

DOI: 10.1186/s13293-026-00993-8

Keywords: HFpEF, cardiomyocyte relaxation, calcium handling, titin, passive stiffness, mitochondrial bioenergetics, sex differences, late sodium current, NAD+, diastolic dysfunction, heart failure, Biology of Sex Differences

Fibrosis stiffens the myocardium by altering the composition, quantity and physical organization of the extracellular matrix surrounding cardiac cells. Collagens provide structural support, but excessive or chemically modified collagen can reduce ventricular compliance and interfere with electrical conduction. In HFpEF, this stiffening is particularly important because the left ventricle must accommodate blood during diastole, the relaxation phase of the heartbeat. When the ventricular wall becomes less compliant, filling pressures rise, blood backs up into the lungs and patients develop exertional shortness of breath. Fibrotic tissue can also create electrical discontinuities that increase vulnerability to atrial and ventricular arrhythmias. Despite its clinical importance, however, fibrosis in HFpEF is not simply a smaller version of the scar formed after a heart attack.

Following myocardial infarction, large numbers of fibroblasts can become activated myofibroblasts, a specialized state associated with contractile proteins and intensive production of scar-forming matrix. These cells help seal and stabilize damaged tissue. In HFpEF, by contrast, the disease usually develops gradually in the setting of obesity, hypertension, diabetes, ageing, kidney disease and systemic inflammation. According to the review, fibrosis in this context appears to arise from the activation of profibrotic programmes across multiple fibroblast states rather than from the dramatic expansion of one classic myofibroblast population. This distinction matters because therapies designed only to eliminate or suppress conventional myofibroblasts may overlook the broader cellular network contributing to chronic myocardial remodelling.

Advances in single-cell RNA sequencing have made it possible to examine gene activity in individual cardiac cells rather than averaging signals across an entire piece of tissue. Spatial transcriptomics adds another layer by mapping those molecular states back to their precise locations within the myocardium. Together, these technologies have revealed that cardiac fibroblasts form a diverse family of cells with distinct transcriptional profiles, anatomical niches and interactions with neighbouring cells. Some populations are closely associated with blood vessels, others with cardiomyocytes or immune cells, and still others appear to specialize in matrix maintenance or inflammatory communication. In HFpEF, different fibroblast states may acquire overlapping disease-associated programmes, allowing the fibrotic response to spread through the cardiac stroma without requiring a single dominant cell type.

One of the important programmes identified in the review involves nitrosative stress. This process develops when reactive nitrogen species, including peroxynitrite, accumulate and chemically modify proteins, lipids and nucleic acids. Nitrosative stress can disrupt signalling pathways, damage cellular structures and alter the behaviour of fibroblasts. Instead of responding appropriately to mechanical or hormonal cues, affected cells may shift toward persistent matrix production and inflammatory communication. The fibroblast response is also linked to disturbed lipid handling. In a metabolically stressed heart, changes in fatty-acid uptake, storage and oxidation can expose stromal cells to toxic lipid intermediates or alter their energy balance. These metabolic abnormalities may reinforce inflammatory and profibrotic signalling, tying the cardiac extracellular matrix to the wider metabolic disturbances that characterize HFpEF.

Fibroblasts do not operate in isolation. Cardiomyocytes, endothelial cells, pericytes, immune cells and vascular smooth-muscle cells continuously exchange signals through cytokines, growth factors, extracellular vesicles and direct cell contact. Mechanical stress caused by hypertension can activate mechanosensitive pathways in fibroblasts, while endothelial dysfunction can change the supply of oxygen, nutrients and vasoactive mediators to the myocardium. Immune cells may release transforming growth factor beta and other signals that promote matrix remodelling, while fibroblasts themselves can influence immune-cell recruitment and persistence. The result is a feedback loop in which inflammation, vascular dysfunction, altered loading conditions and extracellular-matrix stiffness continually amplify one another.

The review further presents the cardiac fibroblast as an integrator of signals arriving from organs far beyond the heart. Adipose tissue can release inflammatory mediators, adipokines and altered lipid species, particularly in obesity and insulin resistance. The bone marrow supplies immune and progenitor cells that may influence myocardial inflammation and repair. Signals originating in the gut, including microbial metabolites and inflammatory products associated with barrier dysfunction, may affect cardiovascular physiology through the circulation. The liver contributes changes in lipid metabolism and circulating proteins, while the lymphatic system regulates immune-cell trafficking and interstitial fluid clearance. Neural inputs, including sympathetic activation, can modify vascular tone, metabolism and inflammatory responses. These pathways suggest that the cardiac stroma is continuously exposed to systemic cardiometabolic stress rather than being governed solely by local cardiac injury.

This interorgan perspective may help explain why HFpEF is so heterogeneous. Two patients with similar ejection fractions can have very different combinations of hypertension, visceral adiposity, renal dysfunction, pulmonary vascular disease, inflammation and atrial arrhythmia. Those differences may produce distinct fibroblast states and distinct patterns of extracellular-matrix remodelling. A therapy that works in one molecularly defined subgroup could therefore fail in another if it targets the wrong pathway or is administered after fibrosis has become structurally entrenched. The emerging challenge is to identify which fibroblast programmes are harmful, which are protective or reparative, and how those programmes change over time.

Early proof-of-concept studies in animal models provide a reason for cautious optimism. Experimental approaches that selectively interfere with fibroblast-associated targets have reduced cardiac fibrosis, improved diastolic performance and lowered susceptibility to arrhythmias in models displaying HFpEF-like features. The therapeutic possibilities include blocking disease-associated signalling pathways, correcting fibroblast metabolism, limiting pathological responses to mechanical stress, and modifying communication between fibroblasts and immune or vascular cells. However, the biological diversity of fibroblasts creates a major safety concern. Broadly suppressing these cells could impair normal matrix maintenance, wound repair or vascular support. Future treatments will likely need to target specific disease-associated states or molecular programmes while preserving essential homeostatic functions.

The authors’ synthesis points toward a new generation of antifibrotic medicine based on precision stromal biology. Rather than viewing fibrosis as an endpoint produced by a single overactive cell type, researchers are beginning to see it as a dynamic system shaped by cellular identity, tissue location, metabolism, inflammation and communication between organs. Mapping these networks in human HFpEF tissue will be essential for determining which findings from animal models translate to patients. Biomarkers capable of identifying active fibroblast programmes, combined with imaging methods that measure diffuse fibrosis and tissue stiffness, could eventually support patient selection and treatment monitoring. If these strategies succeed, fibroblast-directed therapies may do more than reduce collagen deposition: they could interrupt the molecular circuits linking systemic metabolic stress to myocardial dysfunction, offering a targeted way to treat one of heart failure’s most persistent and least understood features.

Subject of Research: Cardiac fibroblast diversity, myocardial fibrosis and interorgan drivers in heart failure with preserved ejection fraction (HFpEF)

Article Title: Cardiac fibroblast diversity in HFpEF: states, niches, interorgan drivers and targets

Article References: Kiyar, M., Pinto, A.R., O’Sullivan, J.F. et al. “Cardiac fibroblast diversity in HFpEF: states, niches, interorgan drivers and targets.” Nature Reviews Cardiology (2026). https://doi.org/10.1038/s41569-026-01335-2

Image Credits: AI Generated

DOI: 10.1038/s41569-026-01335-2

Keywords: HFpEF, cardiac fibroblasts, myocardial fibrosis, extracellular matrix, heart failure, single-cell transcriptomics, spatial transcriptomics, cardiometabolic stress, diastolic dysfunction, antifibrotic therapy