A collaborative research team led by Dr. Lenan Zhuang (Zhejiang University), Dr. Ping Liang (Zhejiang University), and Dr. Xuguang Du (China Agricultural University) has published a landmark study, “Modeling Long-QT Syndrome Using Gene-Edited Miniature Pigs,” in Circulation (1).
This study reports two major advances:
- The generation of the world’s first gene-edited miniature pig model of Long-QT Syndrome (LQTS)
- The integrated use of multimodal electrophysiological approaches—including noninvasive telemetry, electrical mapping, and optical mapping—to validate cardiac phenotypes, investigate disease mechanisms, and evaluate therapeutic interventions in a large-animal model
Background and Rationale
Long-QT Syndrome type 2 (LQT2) is an inherited arrhythmia caused by loss-of-function mutations in KCNH2, which encodes the hERG potassium channel responsible for the rapid delayed rectifier current (IKr), a key determinant of ventricular repolarization. Clinically, LQT2 is characterized by QT prolongation and a high risk of malignant ventricular arrhythmias, including torsades de pointes and sudden cardiac death.
Although rodent and heterologous expression models are widely used, they fail to accurately reproduce human ventricular repolarization because IKr plays only a minor role in rodents. The lack of a physiologically relevant large-animal model has therefore limited translational studies and drug development for LQT2.
Generation of a KCNH2-Knockout Miniature Pig Model
Using CRISPR–Cas9–mediated gene editing, combined with somatic cell nuclear transfer (SCNT) and embryo transplantation, the authors successfully generated the first KCNH2-knockout miniature pig model of LQT2, closely recapitulating the clinical and electrophysiological features of the human disease.
In Vivo Electrophysiological Phenotyping
Continuous 24-hour ambulatory ECG monitoring was performed in conscious, freely moving animals using a noninvasive physiological telemetry system (MappingLab). Compared with wild-type controls, KCNH2-mutant pigs exhibited:
- Marked QT interval prolongation
- Abnormal T-wave morphology
- Increased QT dispersion
- Spontaneous torsades de pointes ventricular tachycardia
These findings closely mirror the human LQT2 phenotype.
Electrical Mapping and Arrhythmia Inducibility
Under anesthesia and open-chest conditions, high-density in vivo electrical mapping (MappingLab) was conducted. Programmed electrical stimulation showed that wild-type hearts returned promptly to sinus rhythm, whereas KCNH2-mutant hearts developed sustained ventricular fibrillation. Activation maps revealed conduction fragmentation and pronounced repolarization heterogeneity, indicating a highly arrhythmogenic substrate.
Optical Mapping Reveals Repolarization and Calcium Handling Defects
High-resolution optical mapping of ventricular tissue demonstrated significant electrophysiological abnormalities in mutant hearts, including:
- Prolonged action potential duration
- Slowed conduction velocity
- Increased repolarization dispersion
- Abnormal calcium transients with transient pauses
Simultaneous voltage- and calcium-sensitive dye imaging provided direct insight into excitation–contraction coupling defects associated with IKr deficiency.
Pharmacological Modulation with Calcium Channel Blockade
Treatment with the calcium channel blocker diltiazem reduced calcium transient pauses, shortened action potential duration, and partially restored repolarization toward wild-type levels. These results provide the first large-animal experimental evidence that calcium channel blockade may reduce arrhythmogenic risk in LQT2.
Cellular and Molecular Validation
Patch-clamp recordings from isolated ventricular cardiomyocytes confirmed a significant reduction in peak and tail IKr current densities in KCNH2-mutant pigs. In parallel, single-nucleus RNA sequencing revealed broad ion-channel remodeling, metabolic suppression, and activation of inflammatory pathways, offering new insights into LQT2 pathophysiology.
Significance and Translational Impact
This study establishes the first gene-edited miniature pig model that faithfully recapitulates human LQT2, representing a major advance beyond existing small-animal models. Given the central role of the hERG channel in both inherited and acquired long-QT syndromes, this platform offers high translational value for:
- Mechanistic studies of ventricular repolarization
- Preclinical drug safety and efficacy testing
- Development of gene- and cell-based therapies
The integrated use of telemetry, electrical mapping, optical mapping, and cellular electrophysiology sets a new benchmark for translational cardiac electrophysiology research.
References:
1. Zhang, Yuan et al. “Modeling Long-QT Syndrome Using Gene-Edited Miniature Pigs.” Circulation vol. 152,23 (2025): 1659-1662. doi:10.1161/CIRCULATIONAHA.125.074681
