It’s easy to injure a knee. If a football player has his cleats planted solidly in the turf and gets tackled from the side – BOOM! Knee injury. The knee is shoved one way, but the foot doesn’t move.
When you play sports, cartilage wedges (called menisci) in your knees absorb the shocks of each step, jump and tackle. Cartilage is built to take abuse, but if a tackle from the side hits the knee just right, the meniscus can tear.
It’s easy to injure a knee, but it’s difficult to fix one. A torn meniscus is the number one reason football players go in for surgery. Doctors can stitch up small tears, remove the meniscus or replace the knee with a metal or plastic joint. Unfortunately, removing the meniscus (meniscectomy) can lead to bone damage and a decreased range of motion, and joint replacements only last 10 to 15 years.
Dr. Kyriacos Athanasiou, a professor at UC Davis and chair of the department of biomedical engineering, is working on a way to grow cartilage in his lab and turn it into a permanent solution for meniscus injuries.
Athanasiou’s research is important because cartilage, unlike muscle or bone, can’t repair itself. Athanasiou said there are two reasons why cartilage doesn’t have a healing response. First, cartilage is white, which means there is no blood running through the tissue.
“If you don’t have blood, that means you’re not going to have nutrients or stem cells in the tissue,” Athanasiou said.
Nutrients are the fuel for tissue repair, and stem cells are the building supplies. Without blood in the tissue, there are no materials available for the healing process.
The second reason cartilage can’t heal itself is that cartilage cells are spaced far apart in the tissue. The cells are held together by collagen that forms an “extracellular matrix.” Athanasiou said the distance between cells limits their communication – cells can’t mount a healing response if they can’t communicate that tissue is damaged.
“If those cells are completely oblivious to what is going on around them, then they can’t respond,” Athanasiou said.
Athanasiou said to imagine a person at the Medical Sciences complex trying to yell a message to someone at the Silo – a big communication problem.
The National Football League recently gave Athanasiou’s research group a $125,000 grant to study new forms of knee repair. The grant is one of many that fund Athanasiou’s research into biological methods of meniscus replacement.
Athanasiou’s team has found a way to grow cartilage in the laboratory using stem cells and special kinds of skin cells. There are not a lot of all-purpose cells in the human body, so Athanasiou must make copies of the cells.
“We take that small number of cells, multiply them and convert them into cartilage,” Athanasiou said.
To convert cells into cartilage, the all-purpose cells are prodded through chemical and mechanical means to form “cartilage-like” tissue. The new cartilage is grown into meniscus shapes using special molds.
It will be years before Athanasiou’s lab-made menisci end up in human knees. Once the lab research is complete, the tissue will be tested in small animals like mice or rabbits and then large animals like goats or sheep. Then there will be a clinical study using the cartilage in humans. The entire process takes time and lots of money, but eventually, Athanasiou hopes to get FDA approval for his discovery.
Someday, surgeons may implant cartilage grown from stem and skin cells into an NFL player’s knee and send him back to the field. Athanasiou is excited to be part of that process.
“Joints are so pivotal – no pun intended – in everything we do,” Athanasiou said.
MADELINE MCCURRY-SCHMIDT dislocated her left kneecap in high school P.E. It was a horrible experience, until the paramedics arrived with morphine. Send her column ideas at memschmidt@ucdavis.edu.
