Nuclear Paraspeckles Sequester Fth1 mRNA to Trigger Ferroptotic Heart Failure

Pathological myocardial hypertrophy serves as a critical harbinger of heart failure (HF) and can be triggered by external stimuli such as pressure overload or heightened sympathetic nervous activity. Although liquid-liquid phase separation (LLPS) represents a fundamental cellular stress-response mechanism implicated in diverse disease etiologies, its precise role in heart failure has remained elusive. Of particular interest are paraspeckles—membrane-less nuclear organelles formed via LLPS driven by the long non-coding RNA Neat1.

Recently, researchers published a study online in the European Heart Journal titled "Paraspeckles as a target for myocardial hypertrophy." This landmark study provides the first direct evidence of paraspeckles within cardiomyocytes and elucidates their pivotal role in pressure overload-induced myocardial hypertrophy and HF.

Pathological stimuli promote paraspeckle assembly in cardiomyocytes, which sequesters Fth1 mRNA inside the nucleus. This nuclear retention suppresses ferritin heavy chain (FTH1) expression, thereby disrupting iron homeostasis, triggering ferroptosis, and ultimately driving myocardial hypertrophy and cardiac dysfunction. Remarkably, AAV9-mediated cardiomyocyte-specific knockdown of Neat1-2 effectively halts paraspeckle assembly, significantly mitigating transverse aortic constriction (TAC)-induced myocardial hypertrophy and HF.

Liquid-Liquid Phase Separation and Nuclear Paraspeckles in Cardiac Biology

Liquid-liquid phase separation (LLPS) is a physical phenomenon driven by complex interactions among proteins, RNA, DNA, and small molecules, culminating in the formation of intracellular membrane-less structures. These liquid condensates facilitate cellular compartmentalization, promote catalytic activity, and enable dynamic responses to microenvironmental stress. Emerging evidence highlights that LLPS is essential for cardiac physiology, regulating myocardial function, influencing pathological remodeling, and safeguarding cardiomyocytes against acute injury.

Although RNAs—particularly long non-coding RNAs (lncRNAs)—are known to serve as molecular scaffolds that recruit specific proteins to drive phase separation, the precise mechanistic contributions of RNA-mediated LLPS to cardiac function and disease remodeling remain largely unmapped.

Paraspeckles represent a prototypical RNA-mediated phase-separated structure that depends strictly on the nuclear assembly of Neat1-2 (the long isoform of the lncRNA Neat1). Playing a vital role in disease pathogenesis and progression, paraspeckles capture and sequester specific transcripts and proteins, thereby modulating post-transcriptional processing, mRNA stability, and nucleocytoplasmic transport—processes paramount to cellular stress responses and homeostasis.

While earlier studies noted that Neat1 expression surges following myocardial infarction and exacerbates ischemic injury by acting as a microRNA sponge, whether Neat1 actively drives pathological hypertrophy and heart failure through the formation of paraspeckle condensates via LLPS remained unknown.

A Novel Pathogenic Axis: Paraspeckles, Fth1 Retention, and Ferroptosis

In this study, researchers present the first definitive evidence confirming the existence of RNA-mediated paraspeckle condensates in cardiomyocytes, underscoring their crucial regulatory involvement in pathological cardiac hypertrophy and heart failure.

Figure 1. Schematic diagram of the mechanism.

Mechanistically, paraspeckles induce cardiomyocyte ferroptosis by retaining Fth1 mRNA within the nuclear compartment, thereby driving pathological cardiac remodeling. Disruption of Neat1 effectively abolishes paraspeckle assembly, and targeted knockdown of Neat1-2 in cardiomyocytes using adeno-associated virus serotype 9 (AAV9) significantly attenuates pressure overload-induced myocardial hypertrophy.

Clinical Significance and Therapeutic Implications

These findings establish a novel therapeutic target for heart failure. By demonstrating that nuclear paraspeckle condensation directly links mechanical stress to ferroptotic cell death in cardiomyocytes, the study reveals that modulating paraspeckle assembly and function represents a promising biophysical strategy to combat pathological cardiac remodeling and heart failure.