In vitro cellular models for cardiac development and pharmacotoxicology.

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Stem Cell Biology

Background:

• Permanent cardiac cell cultures lose proliferative and specific properties, limiting study of developing heart biology and pharmacology.
• Pluripotent embryonic carcinoma (EC) and embryonic stem (ES) cells offer a novel approach for in vitro cardiogenic differentiation studies.

Purpose of the Study:

• To investigate cardiogenesis in vitro using EC and ES cells differentiated into cardiomyocytes.
• To characterize developmental stages of cardiomyocyte differentiation using electrophysiological and molecular techniques.
• To evaluate the utility of ES cell-derived cardiomyocytes for pharmacological and embryotoxicological investigations.

Main Methods:

• Differentiation of EC and ES cells into embryoid bodies to induce cardiogenesis.
• Whole-cell patch-clamp technique to measure action potentials and ionic currents at distinct differentiation stages.
• Reverse transcription polymerase chain reaction (RT-PCR) to analyze cardiac-specific gene expression (e.g., myosin heavy chain, MLC-2V, ANF).
• Pharmacological studies assessing chronotropic responses and Ca(2+) channel activity.
• Application of retinoic acid (RA) during embryoid body development to assess its influence on cardiac differentiation.

Main Results:

• Spontaneously beating cardiomyocytes were generated from EC and ES cells via embryoid bodies.
• Three distinct developmental stages of cardiomyocyte differentiation were identified based on electrophysiological properties (action potentials, ionic currents) resembling early, ventricular, atrial, or sinus nodal cells.
• Gene expression analysis confirmed the developmental trajectory, with alpha- and beta-cardiac myosin heavy chain expressed early, and ventricular-specific MLC-2V and atrial-specific ANF expressed at terminal stages.
• Pharmacological responses to compounds affecting cardiac function were consistent with data from living organisms.
• Retinoic acid demonstrated a temporally controlled influence on cardiac differentiation and gene expression.

Conclusions:

• ES cell-derived cardiomyocytes provide an excellent in vitro model for studying early cardiac development.
• This model is suitable for pharmacological investigations and embryotoxicological studies.
• The differentiation process recapitulates key electrophysiological and molecular events of in vivo cardiogenesis.