Researchers from Tufts University have announced that they have developed a tissue engineering strategy to repair one of the most common knee injuries -ruptured anterior cruciate ligaments (ACL) – by mechanically and biologically engineering new ones. This ligament at the centre of the knee connects the leg to the thigh and stabilises the knee joint in leg extension and flexion.
The Tufts team is developing a patented ACL product that can be custom-engineered from a patient’s or donor’s adult stem cells, which may be readily obtained from bone marrow. Researcher Greg Altman has also formed a company, Tissue Regeneration Inc. (TRI), to develop and market the product.
In the process, ligaments are grown and ‘banked’ prior to knee trauma so they will be readily available at the time of reconstruction.
‘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.’
Approximately 200,000 ACL surgeries were done in the US last year, costing an estimated $3.5 billion, plus another $200 million for subsequent therapy. Worldwide, another 400,000 people last year injured this ligament. The costs associated with surgery can range from $10,000 to $25,000 per procedure, and up to $1,200 in physical therapy.
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 by the patient or donor and then implanted immediately following knee joint trauma.
To date, no human clinical trials have been reported with tissue-engineered ACLs. Altman plans a long-term, US Food and Drug Administration (FDA) relevant 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. Other common post-surgery problems have been infection and disease transmission, including gangrene.