Make your own ACL

Homegrown ligaments could repair debilitating knee injuries

Tufts researchers have developed a method for repairing one of the most common and devastating knee injuriesÑruptured anterior cruciate ligaments (ACL)Ñby biologically engineering new ligaments.

Tissue-engineered ACL ligament strands

Greg Altman, a doctoral student in engineering at Tufts, presented the findings February 11 at the 48th annual meeting of the Orthopaedic Research Society in Dallas, Texas. Altman has been conducting the research under the guidance of David Kaplan, director of Tufts' Bioengineering Center, and Dr. John C. Richmond, professor of orthopedic surgery at Tufts School of Medicine.

The Tufts team is developing a patented ACL product that can be engineered from a patient or donor's adult stem cells, which are readily obtained from bone marrow. Altman has formed a company, Tissue Regeneration Inc. (TRI), to develop and market the product. The company already has received seed capital from government grants, including from the National Institutes of Health.

With the new technology, ACL ligaments are grown and "banked" prior to knee trauma so they will be readily available in case surgery is needed. The ACL connects the leg to the thigh and stabilizes the knee joint in leg extension and flexion.

"The technology for this tissue repair and ligament growth could fundamentally change the way we treat this very common injury," said Altman. "And since the ACL has poor healing capabilities, our new ligament tissue could significantly reduce the recovery time to just weeksÑrather than monthsÑfor professional athletes and sports enthusiasts, compared with current surgical practices."

Approximately 200,000 ACL surgeries were done in the United States last year, costing an estimated $3.5 billion; another $200 million was spent on follow-up physical therapy. In addition, the cost to individual sports teams or players also is significantÑincluding lost championships and declining ticket revenues.

The research may be particularly significant for women athletes because recent studies show that female soccer and basketball players are three to four times more likely to suffer an ACL injury than men.

"Orthopedic surgeons and active people all over the world will find great hope in this research," said Richmond, chief of adult orthopedics and sports medicine at Tufts-New England Medical Center. "We look forward to the day when we'll be able to replace a damaged ligament with a healthy new one, grown from our own tissue."

To create the custom-made ligaments, the team of tissue engineers cultures cells in vitro in a specially designed bioreactor with a collagen or other suitable biodegradable matrix. The cells are then stimulated with multi-dimensional, mechanical forces that mimic ligament movement in the body to develop into living tissue. The bioengineered ligaments can be stored until needed and then implanted following knee joint trauma.

To date, no human clinical trials have been reported with tissue-engineered ACLs. Altman plans a long-term trial of ACL implants in goats later this year.

"Neither reconstructive surgery nor biological or synthetic prostheses can restore complete functionality to the knee without associated debilitating side effects such as pain, tendonitis, muscle atrophy and loss of function," said Altman, who, as a Tufts undergraduate and All-American offensive tackle, suffered a season-ending ACL injury in 1996.

"Following ACL surgery, most people are on crutches for two weeks, can jog after two or three months and can return to athletics after six months," said Altman. "But you don't feel like you have your knee back until 12 or 18 months after surgery. And 15 percent of those with an injured ACL never return to pre-injury activity levels."