Michael J. Yaszemski ’77 ’78G, an orthopedic surgeon at Mayo Clinic in Minnesota, is renowned for his groundbreaking treatments of patients with skeletal defects requiring reconstruction. He performs spinal surgery and oncologic surgery of the spine, sacrum and pelvis. Yaszemski also directs Mayo’s Tissue Engineering and Biomaterials Laboratory, where he builds biodegradable scaffold polymers and uses tissue engineering strategies to promote bone and spinal cord regeneration. Yaszemski holds an M.D. from Georgetown University School of Medicine, as well as B.S./M.S. (Lehigh) and Ph.D. (MIT) degrees in chemical engineering. A retired U.S. Air Force brigadier general, he served in Afghanistan and Iraq. In 2016, he was elected to the National Academy of Medicine.
Q: Beyond scientific and mathematical intelligence, what are the fundamental qualities necessary to be a good researcher?
A: Integrity is highest. You have to be honest in everything you do. Curiosity is incredibly important. And persistence. In surgery, we want to be prepared for every aspect of an operation, and we expect it will go as planned 100 percent of the time. In the lab, we expect mostly failures. If we have a success one out of 100 times, we’re ecstatic. With persistence, we learn from failures and eventually succeed.
Q: How does an engineering education prepare one to become a medical researcher or a physician?
A: Engineering teaches problem-solving. That’s what we do in medicine. We’re given problems and we have to sort out a plan to solve them. Engineering also gives us quantitative technical skills to measure the quality of our work. To be a researcher, those same things are important. I received a great education at Lehigh, and that has had a lot to do with my being able to do this job.
Q: To what extent is your research informed and improved by the surgeries you perform?
A: Everything we do in our lab is based on a research question formulated from an unmet clinical need. We start from where we as clinicians fail, we bring it to the lab, make a research question, try to get an answer and then take it back to the clinic.
Q: What types of tissue engineering strategies do you employ to promote spinal cord regeneration?
A: We synthesize novel polymers. We do 3D fabrication of those polymers into scaffolds. We use a variety of 3D printing techniques. Most cells that regenerate tissue are anchorage-dependent; they have to find a surface they like and will attach to. The scaffold serves as an anchorage for cells and as a temporary structural entity to provide the load-bearing function of bone. We haven’t yet enabled paralyzed animals to walk. But we have made nerves grow in an injured spinal cord.
Q: What kind of biodegradable polymers do you work with in bone scaffolds?
A: The one we use for bone is polypropylene fumarate. When we put the scaffold in the body, we have to keep it in a water-free environment. But in the body, it encounters water tissue and simply goes back to equilibrium. That’s how it degrades. The base material for this was my Ph.D. thesis. It worked out well, and we’re still using it 20-some years later.
Q: How do you engineer these polymers to function in these scaffolds?
A: We engineer the rate of degradation so that it is slower than the growth of bone being regenerated. Bones heal at different rates. A finger bone can heal in six weeks; a thigh bone (femur) can take up to a year. If you put a scaffold in a thigh bone, it can’t go away before the bone is ready. We also engineer the surfaces to be friendly for the anchorage of cells. Cells will anchor, or not, depending on several surface properties, like roughness and chemical composition.
Q: What kind of composite materials do you work with and how effective are they at regenerating bone?
A: We use metals, ceramics and polymers. Our group’s core competence is polymers, and they are what we use most. To make the composite material mimic the specialized bone-tendon junctions of the body, called entheses, we use a composite scaffold. Composite scaffolds have interdigitating sections that will each support the formation of a specific tissue type. In this application, the two different scaffold sections represent the normal bone-tendon anatomy of the enthesis.
Q: How do polymers reconnect segmental nerve defects?
A: A nerve scaffold is a tube. When a nerve injury results in a missing segment of nerve tissue, a new nerve has to grow through this tube to reach the nerve-muscle junction. The tube channels need reserve space to keep scar tissue out so that nerve fibers can grow through it. When the injured part of the nerve crosses a joint, the tube-shaped scaffold must bend as the joint bends, and the tube must maintain a circular cross-section as it bends. We changed the tube synthesis and fabrication parameters until we arrived at a manufacturing process that produced a tube that can bend 130 degrees before it flattens at the apex of the bend. That’s enough for most joints.
Q: Your colleagues say you are exceptionally dedicated to your patients. What inspires this devotion?
A: One of my mentors said we should take care of every patient according to the F2 rule: treat them like friends and family. I think most of us here take that to heart. It’s what I would want of someone taking care of me.
Q: How has medicine improved the lives of persons with spinal cord injuries or diseases? How much more improvement do you foresee 10 years from now?
A: In the past 10-15 years, we’ve made good progress in methods to decrease the secondary injury after a spinal cord injury, and in the rehabilitation of spinal cord injury patients, but not in the ability to get a spinal cord that’s not working to start working again. The secondary injury is the response to the primary injury: the swelling and inflammation of the tissues in the vicinity of the primary injury site. I will stop short of predicting the future, but I hope that cell-based, stem-cell-based, molecule-based and regenerative medicine technologies let us see some improvement in the healing of an injured spinal cord.
Q: Mayo has a successful partnership with Lehigh’s Healthcare Systems Engineering program. What role can systems engineers play in healthcare delivery?
A: Under the Affordable Care Act, physicians are moving from being compensated for how much of something we do to being compensated for the quality we deliver. We have to measure that, and it has to be a quantitative measure. Systems engineering can play an important role so that we don’t duplicate things and that we optimize resources and processes in the operating room and clinic.
At Mayo, we have transitioned our Rochester campus and our surrounding healthcare system, which has more than 70 practices in the upper Midwest, into a single operating company. Some of the patients from these regional practices come to Rochester for consultations and/or surgical procedures, then go back home to receive support from family, friends, and their local physicians. A systems engineering approach can help optimize that process.
Q: You give much credit for your success to the teams you work with at Mayo. How does the leader of a team instill a spirit of teamwork?
A: First is integrity, then trust. A leader who has earned trust has done so because his or her team members believe that she/he behaves with integrity. People must believe the leader wants the team to succeed and values their contributions. You have to leave your ego at the door and choose the right person to do the job. Look for discrete and early wins. Make goals reasonable. Accept failure in all team members, including yourself. No one will ever try something new again if you punish them for failing. If they have prepared, planned, considered the risks and given their best—but fail, thank them, and ask what we’ve learned and where we’re going.
Interview by William Tavani
