INSTITUTE OF ENGINEERING IN MEDICINE

One area of Dr. Chien’s work that has had enormous impact has been his research in the cardiovascular system and in particular the fluid dynamics of blood flow. His research has led to the understanding of sickle-cell anemia and other ailments that affect the proper flow of blood. Blood is what delivers the necessary nutrients to the body’s organs, and without proper delivery of these necessary nutrients (such as oxygen), the organs begin to fail.

In 1967, perhaps his annus mirabilis, Dr. Chien published three seminal papers in Science that radically advanced the understanding of the physics behind the flow of red blood cells. Red blood cells are the most dominant blood cell (numbered anywhere between 4.5 and 5.5 million per cubic millimeter in humans) and are responsible for the transportation of oxygen and carbon dioxide. In humans these cells take a disc-like shape and lack a nucleus. Chien and his colleagues were able to explore the flow properties of red blood cells through various experiments involved with filtering red blood cells through plastic porous sieves. One key finding was that the flow of red blood cells does not follow Newtonian behavior and this characteristic is fundamental in aiding red blood cells to squeeze through capillaries.

Chien and his colleagues further discovered the importance of the “malleability” of red blood cells to pass through tiny pores smaller than the cells’ diameter. To put in another way, a healthy normal red blood cell is able to “squeeze” by deforming its shape and pass through small pores. In addition, this deformation helps lower the viscosity of blood and facilitate flow. A crucial property of blood, and in fact for any liquid, is its viscosity or its ability to flow. A liquid with low viscosity, such as tap water, can flow easily, but a liquid with high viscosity, such as honey, cannot. When red blood cells harden, this deformation property is lost and can prevent proper blood flow.

Another important discovery that determines the viscosity of blood is the ability of red blood cells to aggregate to form rouleaux (like stacks of coins) due to their disc like shape. Chien and his colleagues discovered that this was a crucial factor in modulating viscosity and regulate blood flow and elucidated the mechanical, electrical and biochemical basis of this process. These discoveries show that the shape of red blood cells is not accidental, but rather a highly engineered design meant for efficient transportation.

Dr. Chien’s major research focus in the last two decades is on the elucidation of the mechanisms by which mechanical forces such as pressure and flow regulate the behaviors of the cells in blood vessels, including the endothelial cells lining the vessel lumen and the smooth muscle cells in the vessel interior and their interactions. His work has led to the understanding how forces with a clear direction (as seen in the straight parts of the vascular tree) can protect the vessels from atherosclerosis and how forces without a clear direction (as seen in the branch points) make the vessels vulnerable to atherosclerosis. More recently, he has developed novel approaches to assess the optimum microenvironment for the growth and differentiation of stem cells.

These discoveries have lead to fundamental and crucial understanding of the cardiovascular system. Over the past four decades, Dr. Chien has continued to make groundbreaking research at the cutting edge of biology and engineering. He has also provided a great deal of community service to the field of bioengineering and related fields. He has been President of the American Physiological Society, Biomedical Engineering Society, Microcirculatory Society, and International Society of Biorheology, as well as two large umbrella organizations in biomedical science and engineering: the Federation of American Societies in Experimental Biology (FASEB) and American Institute of Medical and Biological Engineering (AIMBE). He is one of eight scholars who are a member of all three U.S. national academies: the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine, as well as the American Academy of Arts and Sciences. In 1988 he was recruited to join UCSD and his efforts and leadership have advanced the Bioengineering Department to be the number one institution of its kind in the world. In 2008 he founded the Institute of Engineering in Medicine to synergize the outstanding research capabilities in Schools of Medicine and Engineering, as well as other units in UCSD, other institutions in La Jolla, and the industry, to advance new discoveries for the improvement of health care.

For more information on Dr. Chien’s life see the following article from the San Diego Union Tribune:
http://www.signonsandiego.com/news/2011/oct/15/obama-honor-ucsds-chien-improving-publics-health/