Mechanics of Early Heart and Eye Morphogenesis

Friday, Sept 20, 11:00 a.m.
T.I. Auditorium (ECSS 2.102)

Dr. Larry Taber
Washington University in St. Louis

ABSTRACT: Although the molecular and genetic aspects of embryonic development are well-studied, scientists need to further explore the physical mechanisms that create tissues and organs. This talk focuses on the mechanics of heart and eye formation in the early embryo.

As the first functioning organ in the developing human embryo, the heart begins to beat about three weeks post-conception. The heart is initially a single muscle-wrapped tube that loops into a curved tube to lay out the basic plan of the future four-chambered pump. Abnormal looping is thought to underlie many of the congenital heart defects that threaten the health of the developing embryo.

Researchers have proposed new hypotheses for heart tube formation and the first phase of looping called c-looping, as the tube bends and twists into a c-shaped tube. Experiments and models suggest that regional differences in growth play a major role in both processes. During c-looping, differential growth may cause the heart tube to bend, while torsion is driven primarily by forces exerted by neighboring tissues. The physical plausibility of this hypothesis was examined using a computational model for the heart based on realistic geometry. The behavior of the model is in reasonable agreement with experimental results from control and perturbed chick embryos, offering support for the hypothesis.

The eyes form initially as a pair of relatively spherical optic vesicles that grow outward from the sides of the primitive forebrain. Each optic vesicle grows until it contacts and adheres to an overlying membrane, or surface ectoderm, via extracellular matrix. The optic vesicle and surface ectoderm then thicken and bend inward to create the optic cup or future retina and lens vesicle that will become the future lens. The speaker’s experiments and models show that inward turning of the optic vesicle is driven by matrix-constrained growth, whereas contraction causes the surface ectoderm to turn inward. The results also suggest that regional cell death or apoptosis is required to close the lens vesicle into a complete fluid-filled shell.

These studies provide new insight into the forces that drive early heart and eye development. The speaker will address how understanding the mechanics of morphogenesis could one day lead to new strategies for tissue engineering, tissue regeneration and the prevention and treatment of congenital malformations.

BIOGRAPHY: Dr. Larry Taber is a senior professor of biomedical engineering and of mechanical engineering and materials science at Washington University in St. Louis. From 2007 until his retirement in 2017, he was the Dennis and Barbara Kessler Professor of Biomedical Engineering. Previously, he spent four years at the General Motors Research Laboratories and 15 years at the University of Rochester. He has published more than 100 journal articles on a wide range of topics including cochlear mechanics, nonlinear shell theory, cardiovascular mechanics and the mechanics of growth and development.

Taber has pioneered studies of the biomechanics of organogenesis, as his work has integrated theoretical modeling with experiments on embryos to study the mechanics of heart, brain and eye morphogenesis. He is a fellow of the American Society of Mechanical Engineers and the American Institute for Medical and Biological Engineering.

Taber won the Richard Skalak Award for the best paper published in the Journal of Biomechanical Engineering in 2004, 2007 and 2015. From 2011 — 2016, he served as co-editor-in-chief of the journal Biomechanics and Modeling in Mechanobiology. He holds a bachelor’s degree in aerospace engineering from Georgia Tech and a PhD in aerospace engineering from Stanford University.