Focus on new faculty: Corinne Henak, exploring perplexing properties of cartilage
Cartilage squeezes like a sponge, breaks like a bone, and slides on itself like ice on ice. Slow, continuous forces condense cartilage like Silly Putty, whereas fast impacts can crack the tissue. Corinne Henak hopes to understand cartilage’s uncanny physical properties from a mechanical perspective in order to improve human health outcomes for orthopedic disease.
Layers of cartilage line the interfaces between bones at every joint within the human body. As people age or experience injury, their cartilage wears down, sometimes leading to incurable osteoarthritis. This condition causes extreme discomfort and decreased mobility—and the lifetime risk of knee osteoarthritis is approximately one in two.
Yet, we don’t fully understand what causes those diseases, what the natural progression of those diseases is, or how to intervene effectively, says Henak, who joined the Department of Mechanical Engineering as an assistant professor in fall 2015.
Most osteoarthritis research takes a population-level, joint-level or bulk-tissue-level approach. Large-scale surveys demonstrated that soft-tissue injuries, such as a torn ACL or an ankle sprain, increase the odds of developing the condition. At the joint-level, elevated contact pressures are predictive of osteoarthritis, while bulk-tissue mechanics modulate cartilage response in a variety of ways depending on the particular details of the experiment. However, these studies fail to provide a unified picture of the biological and structural changes within the cartilage that drive the tissue to degrade.
Although cartilage injuries increase the odds of developing osteoarthritis, it is unclear what changes occur in a joint during and immediately after the initial insult. Surprisingly, scientists lack basic knowledge about when cartilage cracks or softens in response to injury and how far any damage that does occur propagates through the tissue. Henak’s research aims to answer these fundamental questions.
Henak also intends to learn how mechanobiology, the response of cells to mechanical signals, affects disease trajectories. Clinicians have long appreciated that cartilage does not regenerate after trauma. However, it is unclear how individual cartilage cells respond to injuries, and how their response affects disease progression. Basic questions such as whether cells attempt to repair damage by activating signaling pathways or die off en masse remain unanswered within the field.
By taking an engineering approach, Henak hopes to clarify some of the mysteries surrounding the onset of osteoarthritis. She will apply her expertise in biomechanics and mechanobiology to uncover insight into the nature of cartilage as a mechanical material and living tissue. Understanding these questions could open the door to new therapies or designing new materials for medical implants.
“We replace cartilage with plastic and metal because we don’t know how to make a material that is as amazing as cartilage,” says Henak.
The composition of cartilage may partially explain why the tissue reacts differently to fast forces as compared to persistent pressures. Cartilage is not uniform through its thickness or throughout an individual joint—and this inherent variability might be responsible for some of its unique properties. Much remains to be discovered about the material itself and the underlying biology; Henak aims to address these questions with her research.
Henak comes to UW-Madison with a passion for scientific inquiry and a strong foundation in biomechanics extending all the way back to her first research project as a sophomore at the University of Denver. There, she cut her teeth on computational biomechanics before pursuing both experimental and computational research during her PhD at the University of Utah and subsequent postdoctoral training at Cornell University. Her work on soft tissue damage in the hip helped redefine long-held assumptions about the events leading to hip dysplasia.
UW-Madison offers Henak exciting opportunities to collaborate with clinicians and engineers. Henak is looking forward to working with researchers (such as Mechanical Engineering Assistant Professor Peter Adamczyk, another newly hired faculty member) who study biomechanics at a whole-body level, in order to understand the external input forces loading onto cartilage within joints.
Henak also appreciates UW-Madison’s philosophy about educating the next generation of engineers. “The faculty care and they accept new techniques with the overall goal to train good engineers who understand the discipline, have physical intuition, and understand the ethical implications of their work,” she says.
Currently Henak advises one graduate student; she plans to expand her lab in the coming years, continuing her commitment to training and mentorship.
“I love research and I love that biomechanics puts you in this overlapping space where there are really interesting and potentially impactful human applications and also interesting basic questions about complex materials,” says Henak.