Evaluating Seeding Density Effects on Cardiac Organoid Health and Functionality for Toxicity Studies

Area of Science:

• Stem cell biology
• Cardiovascular research
• Drug discovery and toxicology

Background:

• Human induced pluripotent stem cell-derived cardiac organoids are crucial for studying heart physiology and drug toxicity.
• Optimal culture conditions, especially the role of non-cardiomyocytes and seeding density, remain unclear for self-aggregating cardiac organoids.

Purpose of the Study:

• To determine optimal seeding densities for human induced pluripotent stem cell-derived cardiac organoids to improve cardiac maturity and drug toxicity assessment.
• To evaluate the impact of seeding density on organoid morphology, gene expression, functionality, viability, and metabolic activity over time.

Main Methods:

• Cardiac organoids were generated using human induced pluripotent stem cells at varying seeding densities (e.g., 20,000 and 80,000 cells).
• Organoids were assessed for morphology, gene expression, beating functionality, cell viability (apoptosis), and mitochondrial activity.
• The model's sensitivity to doxorubicin-induced cardiotoxicity was compared to 2D cultures.

Main Results:

• Organoid size stabilized by 7 days regardless of seeding density.
• Organoids seeded with 20,000 cells exhibited enhanced cardiac signature, maturity, and reduced fibrosis, with minimal apoptosis and higher metabolic activity after 7 days.
• The 20,000-cell organoid model demonstrated over a tenfold larger selectivity index and improved sensitivity to doxorubicin-induced cardiotoxicity compared to 2D cultures.

Conclusions:

• Seeding 20,000 cells and culturing for 7 days yields cardiac organoids with optimal morphology, transcriptional profile, viability, and beating kinetics.
• This optimized organoid model provides a more sensitive and accurate platform for evaluating drug-induced cardiotoxicity, reflecting in vivo conditions better than 2D cultures.