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Normal development of the outflow tract in the rat
J Ya1, M J van den Hoff, P A de Boer
1Department of Anatomy and Embryology, Academic Medical Center, University of Amsterdam, The Netherlands.
Circulation Research
|March 20, 1998
Summary
The outflow tract
Area of Science:
- Cardiovascular Development
- Developmental Biology
- Cardiac Anatomy
Background:
- The ventriculoarterial connection's development is complex.
- Prevailing rotation models conflict with cell-marking data.
- Understanding outflow tract (OFT) morphogenesis is crucial.
Purpose of the Study:
- To investigate the cellular mechanisms of outflow tract development.
- To clarify the OFT's role in forming the ventriculoarterial junction.
- To reconcile anatomical findings with developmental processes.
Main Methods:
- Immunohistochemistry and in situ hybridization in rat embryos (ED10-P2).
- Bromodeoxyuridine incorporation for DNA replication.
- Annexin V and TUNEL assays for apoptosis.
Main Results:
- Cardiomyocytes in the distal OFT transdifferentiate, not apoptose, starting at ED12.
- Myocardial regression occurs on the dextroposterior side, forming fibrous continuity.
- Myofibroblasts organize into valve anlagen, with some undergoing apoptosis and replacement by cardiomyocytes.
Conclusions:
- OFT myocardial regression and myofibroblast dynamics are key to heart septation.
- The distal OFT boundary shifts, enabling semilunar valve formation at correct positions.
- Differential OFT regression explains the asymmetry of adult heart outlets.