Establishing a new human hypertrophic cardiomyopathy-specific model using human embryonic stem cells

Area of Science:

• Cardiovascular Biology
• Stem Cell Biology
• Genetics

Background:

• Mutations in cardiac troponin T (TNNT2) cause hypertrophic cardiomyopathy (HCM), often leading to sudden cardiac death despite mild symptoms.
• The TNNT2 R92Q mutation is a known hotspot in HCM, but human disease models are lacking.

Purpose of the Study:

• To generate human disease models for TNNT2 R92Q-associated HCM using human embryonic stem cells (hESCs).
• To investigate the cellular and molecular mechanisms underlying HCM development in these models.
• To evaluate the utility of these models for drug screening and cardiotoxicity testing.

Main Methods:

• Generation of TNNT2 R92Q mutant hESC lines (heterozygote and homozygote) via TALEN-mediated homologous recombination.
• Directed cardiac differentiation of mutant hESCs into cardiomyocytes.
• Characterization of cardiomyocyte phenotypes, including cell size, gene expression, calcium handling, and contractility.
• Construction of engineered heart tissues (EHTs) using mutant cardiomyocytes and decellularized heart matrix.
• RNA-sequencing analysis of mutant cardiomyocytes.

Main Results:

• TNNT2 R92Q mutant hESC-cardiomyocytes exhibited larger cell size and altered expression of key cardiac genes (ANP, BNP, SERCA2a, MEF2c, MYH7/MYH6 ratio).
• Mutant cardiomyocytes showed increased calcium sensitivity and contractility.
• EHTs derived from heterozygous R92Q mutant cardiomyocytes mimicked patient drug responses and showed increased sensitivity to caspofungin-induced cardiotoxicity.
• RNA-sequencing indicated calcium dysregulation in early hypertrophy development.

Conclusions:

• hESC-derived TNNT2 R92Q mutant cardiomyocytes and EHTs serve as valuable in vitro human disease models for HCM.
• These models facilitate the study of early hypertrophic development and enable effective drug screening and toxicity testing.