By Molly Glass
Christopher Chen was a teenager when he first started thinking seriously about what makes the human body such an amazing machine. An avid runner and soccer player, Chen injured his knee, sidelining him from sports for a while. His knee eventually got better on its own, but during this time of convalescence, Chen mused about replacement surgery—even the best materials, developed with the most cutting-edge technology, would eventually break down. If he had needed a knee replacement, he’d need another surgery at some point, and maybe even another after that.
Why, Chen wondered, doesn’t our cartilage wear down as fast? While the prevalence of knee and hip replacement surgeries in the United States shows that our cartilage certainly does break down, most people will go their entire lives without needing to replace any joints. What makes our biology more resilient than the metal and plastic replacements scientists have developed?
“What I found very frustrating, or puzzling, about it is that all the materials that we make, they wear. The more you use them, the worse they get. That’s just the nature of engineered materials,” says Chen, now the William Fairfield Warren Distinguished Professor of Biomedical Engineering in Boston University’s College of Engineering. “But so many of our materials, like our joints, seem to not wear. Why they don’t is because cells inside those tissues are continuously producing new material to maintain these tissues.”