Esophageal disorders such as esophageal cancer and gastroesophageal reflux disease (GERD) are difficult to treat without properly understanding the tube-like organ’s mechanical properties and its unique connection between humans’ mouths and stomachs. GERD, for example, is suffered by 1 in 5 US adults and can negatively impact lives by causing chronic heartburn, sleep disturbances, and difficulty eating, leading to discomfort and reduced quality of life.

Recent work from a team led by Northwestern Engineering’s Horacio D. Espinosa and Neelesh A. Patankar uncovers new insights into the mechanical characteristics of the esophagus that could pave the way for better treatments and surgical outcomes for esophageal disorders. 

Horacio D. Espinosa, Neelesh A. Patankar

In “Ex-Vivo Mechano-Structural Characterization of Fresh Diseased Human Esophagus,” published online on February 26 in the academic journal Acta Biomaterialia, Espinosa, Patankar, and a multi-institutional research team – including members from the Feinberg School of Medicine and the University of Wisconsin-Madison – reports a detailed mechanical and structural characterization of human esophageal muscular layers obtained from living patients. The researchers explored how the circular and longitudinal muscle layers of the human esophagus behave differently when stretched.

While previous studies have relied on single-direction testing, or preserved tissue, to evaluate esophageal function, the team used living samples and tested them in multiple directions, providing a more realistic picture of how the organ works.

They analyzed muscle fiber patterns using tests that stretch a material in one direction to measure its mechanical properties alongside ones that stretch it in two perpendicular directions simultaneously to observe how the esophagus behaves under multi-directional forces on the smooth muscle layers. They also used histological imaging techniques to examine the tissue at a microscopic level before and after each test.

The research will help better explain important functions of the esophagus, like how it moves food downward and adjusts to different pressures. Furthermore, “it places the mechanical findings within the context of real esophageal function, helping to refine diagnostic tools like high-resolution manometry and FLIP (Functional Lumen Imaging Probe),” Patankar, professor of mechanical engineering at the McCormick School of Engineering, said about a clinical test developed by John Pandolfino, Hans Popper Professor of Medicine at the Feinberg School of Medicine, and a co-author of this work.

“These findings establish a baseline for understanding esophageal mechanics in both healthy and diseased states, providing insights that can aid in computational modeling, diagnostics, and surgical planning,” said Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at the McCormick School of Engineering.

Multi-directional testing has the potential to overcome the limitations of previous single-direction studies, offering a more accurate view of the esophagus as a complex, flexible tissue.

These findings establish a baseline for understanding esophageal mechanics in both healthy and diseased states, providing insights that can aid in computational modeling, diagnostics, and surgical planning. Horacio D. Espinosa

Because of this work, the researchers were able to expand the existing database of mechanical parameters for computational modeling and lay the foundation for future studies on the esophagus’s active mechanical properties.

Looking ahead, this research could have important biomedical applications, helping to create more accurate computer models for surgical training and regenerative medicine. Since esophageal diseases are common, a better understanding of how esophageal tissue behaves could lead to improved treatments and more successful surgeries for diseases, such as esophageal cancer and nerve damage that causes achalasia – a rare disorder where the esophagus cannot properly move food and liquid to the stomach.

The benefits could also go beyond the esophagus.

“The study combines advanced imaging and testing techniques that could be applied to other soft tissues, skin, muscles, tendon, cartilage, broadening its impact beyond gastroenterology,” Espinosa said.

Moving forward, researchers will focus on how smooth muscle actively contracts and relaxes. Expanded testing, including inflation-extension experiments, will offer a more complete picture of esophageal mechanics. Additionally, studying the effects of temperature could potentially help refine understanding of how the esophagus functions in different conditions.

“The findings provide a valuable database for clinicians and researchers working on esophageal mechanics and related disorders,” Espinosa said.

The research is supported by the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases and the Kenneth C. Griffin Esophageal Center.