Multiple modes of proepicardial cell migration require heartbeat.

Area of Science:

• Developmental Biology
• Cardiac Development
• Zebrafish Model Systems

Background:

• The epicardium, the heart's outer layer, originates from proepicardium (PE) progenitors.
• Improper epicardial development is linked to cardiac defects and impaired regeneration.
• Zebrafish are a key model for cardiac research, but epicardium formation mechanisms are unclear.

Purpose of the Study:

• To elucidate the mechanisms of epicardium formation in zebrafish.
• To investigate the role of heartbeat and fluid dynamics in proepicardial development.
• To characterize the cellular heterogeneity of the proepicardium.

Main Methods:

• In vivo imaging and confocal microscopy to track PE cell migration.
• Histology to analyze epicardial layer formation.
• Genetic and pharmacological manipulation of heartbeat.
• In vitro heart culture and co-culture experiments.

Main Results:

• Proepicardium (PE) cells migrate via a cellular bridge and free-floating aggregates.
• PE clusters form independently of heartbeat, but migration requires cardiac contraction.
• Epicardium formation in culture is independent of hydrodynamic forces but dependent on contraction.
• Zebrafish epicardial cells originate from a heterogeneous progenitor pool.

Conclusions:

• Zebrafish epicardium arises from diverse proepicardium (PE) progenitor cells.
• PE cells utilize a cellular bridge and cell clusters for cardiac attachment.
• Heartbeat is crucial for epicardium formation, specifically for PE cell migration.
• Cardiac contraction, not fluid dynamics, is essential for epicardium development.