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SarcTrack
Christopher N Toepfer1,2,3, Arun Sharma1, Marcelo Cicconet4
1From the Department of Genetics (C.N.T., A.S., A.C.G., M.N., J.A.L.W., R.A., M.S., J.R., O.P., J.G.S., C.E.S.), Harvard Medical School, Boston, MA.
Insights
A new software, SarcTrack, directly tracks sarcomeres in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This tool enables rapid, automated analysis of cardiac muscle contraction for disease modeling and drug screening.
Area of Science:
- Cardiovascular Biology
- Stem Cell Research
- Biotechnology
Background:
- Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are valuable for studying cardiac conditions.
- Immature sarcomeres in hiPSC-CMs pose challenges for accurate contractility analysis.
- Current methods for assessing cardiomyocyte contractility are often low-throughput or indirect.
Purpose of the Study:
- To develop a direct, rapid, and automated platform for tracking sarcomeres in beating hiPSC-CMs.
- To enable quantitative assessment of sarcomere content, contraction, and relaxation parameters.
- To facilitate high-throughput analysis of cardiomyocyte contractile function.
Main Methods:
- Developed SarcTrack, a MatLab software utilizing fluorescently tagged sarcomeres.
- Algorithm quantifies sarcomere content, length, contraction, and relaxation rates.
- Validated SarcTrack using drug-treated hiPSC-CMs and a MYBPC3 hypertrophic cardiomyopathy model.
Main Results:
- SarcTrack rapidly measures hundreds of sarcomeres per cell, generating large datasets.
- Confirmed known drug effects on contractility (CK-1827452, MYK-461, verapamil, propranolol).
- Recapitulated hypertrophic cardiomyopathy phenotypes in MYBPC3 hiPSC-CMs, with normalization by MYK-461.
Conclusions:
- SarcTrack offers a direct and efficient method for quantitative sarcomere function assessment.
- The platform overcomes technical limitations in hiPSC-CM contractility analysis.
- SarcTrack accelerates research on sarcomere-regulating therapeutics and human cardiac genetic variants.
Rationale:
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in combination with CRISPR/Cas9 genome editing provide unparalleled opportunities to study cardiac biology and disease. However, sarcomeres, the fundamental units of myocyte contraction, are immature and nonlinear in hiPSC-CMs, which technically challenge accurate functional interrogation of contractile parameters in beating cells. Furthermore, existing analysis methods are relatively low-throughput, indirectly assess contractility, or only assess well-aligned sarcomeres found in mature cardiac tissues.
Objective:
We aimed to develop an analysis platform that directly, rapidly, and automatically tracks sarcomeres in beating cardiomyocytes. The platform should assess sarcomere content, contraction and relaxation parameters, and beat rate.
Methods And Results:
We developed SarcTrack, a MatLab software that monitors fluorescently tagged sarcomeres in hiPSC-CMs. The algorithm determines sarcomere content, sarcomere length, and returns rates of sarcomere contraction and relaxation. By rapid measurement of hundreds of sarcomeres in each hiPSC-CM, SarcTrack provides large data sets for robust statistical analyses of multiple contractile parameters. We validated SarcTrack by analyzing drug-treated hiPSC-CMs, confirming the contractility effects of compounds that directly activate (CK-1827452) or inhibit (MYK-461) myosin molecules or indirectly alter contractility (verapamil and propranolol). SarcTrack analysis of hiPSC-CMs carrying a heterozygous truncation variant in the myosin-binding protein C ( MYBPC3) gene, which causes hypertrophic cardiomyopathy, recapitulated seminal disease phenotypes including cardiac hypercontractility and diminished relaxation, abnormalities that normalized with MYK-461 treatment.
Conclusions:
SarcTrack provides a direct and efficient method to quantitatively assess sarcomere function. By improving existing contractility analysis methods and overcoming technical challenges associated with functional evaluation of hiPSC-CMs, SarcTrack enhances translational prospects for sarcomere-regulating therapeutics and accelerates interrogation of human cardiac genetic variants.