Location of the anterior cruciate ligament between the femur (thigh bone) and tibia (shin bone). The drawing at right depicts how the ACL can be twisted and torn. (After ‘The cruciate ligaments of the knee.’ Girgis FG, Marshall JL, St Monajem ARS: Clin Orthop 1975;106:216-231)
NASA assists ligament replacement research
As Olympic skiers and skaters raced for medals in Utah, many TV viewers at home winced with each turn and jump as they remembered knee injuries they sustained while skiing, playing soccer, or just stepping off a curb the wrong way. Repairing the human knee is complex because cartilage and ligament do not heal or regenerate. For athletes, that can mean warming the bench for weeks or months — or forever — after injuries like a torn anterior cruciate ligament (ACL).
Reconstruction involves removing part of the knee tendon to replace the ACL and involves long therapy periods. The ideal would be to have a spare ACL already grown and ready for implant, thus speeding recuperation and improving the chances of returning to peak performance. That’s the concept behind research being conducted by a Tufts University scientist who was a pre-season All-American football player at Tufts in the fall of 1996 when he had his own season-ending ACL injury.
Greg Altman, who will receive his doctorate in biotechnology engineering at Tufts this May, discussed his research at the 48th annual meeting of the Orthopaedic Research Society in Dallas on Feb. 12. Altman’s work is partially supported by funding from NASA’s Office of Biological and Physical Research, and draws on results from research using NASA Bioreactors.
Altman’s advisors are Dr. David L. Kaplan, director of Tufts’ Bioengineering Center, and Dr. Gordana Vunjak-Novakovic, a principal scientist at the Massachusetts Institute of Technology. Both are involved in NASA Bioreactor research.
"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 weeks–rather than months–for professional athletes and sports enthusiasts compared with current surgery practices." The research may also be particularly meaningful to female athletes, as recent studies show that female soccer and basketball athletes are three to four times more likely to injure their ACL than males.
Approximately 200,000 ACL surgeries were done in the U.S. last year, costing an estimated $3.5 billion, plus another $200 million for subsequent therapy.
In Altman’s process, ligaments are grown from an athlete’s own bone marrow stem cells and then "banked" in case they are needed for ACL reconstruction. To create the custom-made ligaments, the team of tissue engineers cultures cells in a specially designed bioreactor with a collagen or other suitable biodegradable matrix. The cells are stimulated with multi-dimensional, mechanical forces that mimic ligament movement in the body to develop into living tissue.
The ligaments can be stored until needed by the patient or donor and then implanted immediately following knee joint trauma. Because the replacement would come from the patient’s own body, the risk of rejection is virtually nil.
Altman plans a long-term, FDA-relevant preclinical trial of ACL implants later this year.
Edited by Dave Dooling, Infinity Technology. This story draws on a release by Tufts University. For additional information and high-resolution images, visit the Tufts University web site at: http://www.tufts.edu/communications/altman.htm (non-NASA link)
Source: NASA, May 16, 2005