Opportunity
Cardiac arrhythmia, a life-threatening condition characterized by irregular heartbeats, is a significant safety concern in drug development, as over 50 therapeutic compounds have shown potential to induce unexpected cardiac arrhythmias, leading to market withdrawals. Current preclinical screening methods face major limitations. Traditional patch clamp electrophysiology, while accurate, is low-throughput and skill-intensive. In vitro cell culture models lack the complex physiological environment of living systems, limiting their predictive value for human cardiotoxicity. In vivo mammalian models (e.g., guinea pigs, dogs, primates) are costly, raise ethical issues, and are not efficient for high-throughput screening. Although zebrafish have emerged as a promising model due to genetic similarity, transparency, and high fecundity, existing methods to measure their cardiac function—such as manual heartbeat counting or complex image analysis of the heart—are time-consuming, labor-intensive, and low-throughput. There is a clear unmet need for a cost-effective, high-throughput, and physiologically relevant in vivo screening platform to reliably identify compounds that may cause cardiac arrhythmia, thereby improving drug safety assessment.
Technology
This patent presents a novel high-throughput method using teleost fish (preferably zebrafish or medaka embryos/larvae) as an in vivo model to screen agents for cardiotoxic effects, specifically alterations in heart rate and rhythm. The innovation lies in a non-invasive video imaging and analysis system that quantifies cardiac function by analyzing blood cell circulation dynamics, rather than directly imaging the heart. The process involves exposing teleosts to test agents, immobilizing them in agarose, and recording videos of blood circulation (preferably in the tail) using a microscope connected to a digital camera. A key algorithmic innovation analyzes these videos: consecutive video frames are subtracted to detect moving blood cells, generating a data series of "differential pixels" that corresponds to blood flow speed oscillations. This data is then processed using power spectral analysis (via discrete Fourier transform) to extract two critical parameters. The basic frequency component of the spectrum directly correlates with heart rate, while a novel "cardiac rhythmicity index"—calculated as the ratio of the power of the basic frequency component to the total spectral power—quantitatively measures the regularity of heart rhythm. A decrease in this index indicates increased arrhythmia. This automated, software-driven approach transforms a simple video of tail blood flow into precise, quantitative measures of cardiotoxicity.
Advantages
- High-Throughput & Efficiency: Enables rapid screening of many compounds simultaneously, overcoming the low-throughput limitations of patch clamp and manual zebrafish assays.
- Cost-Effective: Utilizes inexpensive zebrafish embryos, reducing costs compared to mammalian in vivo models.
- In Vivo Relevance: Provides a whole-organism physiological context that in vitro cell-based assays cannot replicate, improving predictive accuracy for human cardiotoxicity.
- Non-Invasive & Objective: Measures cardiac function via blood flow in the tail, avoiding invasive procedures and eliminating observer bias through automated software analysis.
- Quantitative & Sensitive: Generates precise numerical data for both heart rate and a novel "cardiac rhythmicity index" for beat regularity, detecting subtle arrhythmogenic effects.
- Ethical Advantage: Uses early-stage teleost embryos, which are subject to less stringent ethical regulations than adult mammals.
- Proven Validation: Demonstrated capability to detect known cardiotoxic effects (e.g., decreased heart rate and regularity induced by haloperidol).
Applications
- Pharmaceutical Safety Screening: Preclinical assessment of new drug candidates for potential cardiotoxic side effects, particularly hERG channel blockade and arrhythmia risk.
- Toxicology Testing: Evaluation of environmental toxins, chemicals, or industrial compounds for cardiac toxicity.
- Drug Repurposing Studies: Screening existing drug libraries for unexpected cardiotoxic profiles.
- Basic Cardiovascular Research: Studying the mechanisms of cardiac arrhythmia and the effects of genetic modifications on heart function in zebrafish models. Academic & Industrial R&D: Providing a versatile tool for research laboratories and biotech companies involved in drug discovery and safety pharmacology.
