Check Up: University of Pennsylvania researchers regrowing cartilage in lab

Eagles fans are in a tizzy, and bad cartilage is to blame. Last month, AnnArbor.com broke the news that defensive end Brandon Graham had microfracture knee surgery in December 2010.

The surgery involves drilling tiny holes in the bone, releasing blood and clotting molecules to heal the site. Scar tissue made this way is a poor stand-in for real cartilage, but few options exist.

At the University of Pennsylvania, professors Jason Burdick and Robert Mauck are regrowing cartilage in the lab, which could lead to better treatments.

Cartilage is composed of cells called chondrocytes and the connective tissue they make. In joints, cartilage helps to distribute weight and allow bones to glide past one another during motion.

Damage to cartilage occurs with age, obesity-related stress, and acute injuries. Unlike muscle, cartilage gets no blood supply, which limits healing. Cartilage damage can be excruciating as uncushioned bones grind against one another.

Researchers can already grow chondrocytes in the lab, but coaxing them to make high-quality connective tissue is tricky. Burdick says the team has made a breakthrough by culturing cells in conditions that mimic the body's environment.

The team grows chondrocytes from bone-marrow-derived adult stem cells, embedded in a gel of hyaluronic acid - a growth-promoting molecule in natural cartilage. Next, these gels are compressed by tiny metal pistons that Mauck has developed. These enhance tissue development by simulating physical activity.

Mauck says the team can now make cartilage that is almost as good as the real thing. In the next month, he will be testing the system in pigs to see how it integrates into the body and withstands physical activity.

Eric Kropf, an orthopedic surgeon at Temple University Hospital, says this technique likely won't apply to pervasive cartilage damage, but he sees promise for contained injuries that can be plugged by the gel.

The Phillies' assistant team physician, Steven Cohen, who also is a sports-medicine surgeon at the Rothman Institute, treats many such cartilage injuries. Regrowing cartilage, he says, "would certainly be exciting and useful."