The Midwest Mechanics Seminar continues with a talk entitled “Mechanics, Mechanobiology, and Mechanical Homeostasis in Soft Tissue” by Yale University Professor Jay D. Humphrey.at 3:30 p.m. on Wednesday, March 22. The talk will be held on Zoom.

Biography: J.D. Humphrey is John C. Malone Professor of Biomedical Engineering at Yale University. He received the Ph.D. in Engineering Science and Mechanics from Georgia Institute of Technology and completed a post-doctoral fellowship in Medicine – Cardiovascular at Johns Hopkins University. His research and teaching focuses on vascular mechanics and mechanobiology, with particular interest in development, hypertension, aneurysms, vascular aging, and tissue engineering. He has authored a graduate textbook (Cardiovascular Solid Mechanics), an undergraduate textbook (An Introduction to Biomechanics), and a handbook (Style and Ethics of Communication in Science and Engineering), and published 350+ archival journal papers. He served for 10 years as founding co-editor for the journal Biomechanics and Modeling in Mechanobiology, for 12 years on the World Council for Biomechanics, including as Chair of the Technical Program of the 2014 World Congress in Biomechanics, and served for two years as Chair of the US National Committee on Biomechanics. He lives with Rita, his wife of 41 years, in Branford, CT.

Abstract: Cells within load-bearing soft tissues sense and respond to diverse stimuli, particularly mechanical. Data collected across micro- to macro-scales reveal that many of these responses can be understood within the context of “mechanical homeostasis,” that is, a ubiquitous process by which particular mechanical quantities are regulated to remain, within a range, near a preferred value, often called a set point. As an example, both blood flow-induced wall shear stress and blood pressure-induced intramural stress tend to be mechano-regulated to remain close to region-specific set-points in vascular mechanics.

In this talk, we will consider arteries as an archetype of soft tissues for they exhibit the characteristic nonlinearly anisotropic responses seen in most soft tissues. Moreover, we will consider three examples to illustrate how mechanics can inform models of the associated mechanobiology. These examples include the development of local dilatations of the arterial wall, referred to as aneurysms, the response of the arterial wall to sustained elevations in blood pressure, known as hypertension, and the design and use of a tissue engineered conduit for treating children with congenital heart conditions. In each of these cases, we will use a common theoretical framework referred to as a constrained mixture model, which reveals the need for three classes of constitutive relations – those for the production, removal, and mechanical response of individual structurally significant constituents that endow the arterial wall with stiffness and strength. The interested reader is also referred to the following references:

• Humphrey JD (2021) Constrained mixture models of tissue growth and remodeling – Twenty years after. J Elasticity 145:49-75.
• Humphrey JD, Schwartz MA (2021) Vascular mechanobiology: homeostasis, adaptation, and disease. Annu Rev Biomed Engr 23:1-27.
• Drews J, Pepper VA, Best CA, Szafron JM, …, Humphrey JD, Shinoka T, Breuer CK (2020) Spontaneous reversal of stenosis in tissue-engineered vascular grafts. Sci Transl Med 12:eaax6919.