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Last Updated: Saturday, 12 January 2008, 00:02 GMT
Gene therapy implants for tendons
Tendon injuries can be difficult to treat
Freeze-dried implants loaded with gene therapy solution are being developed which may help repair injured and difficult-to-treat tendons.

Early trials in the US suggest the implants could accelerate healing, and help restore a wide range of movement.

They have been tested in mice with injuries similar to those found in the flexor tendon of human hands, which can be very tough to treat effectively.

The University of Rochester work is featured in Molecular Therapy.

Gene therapy is a field which is going to take off in a serious way over the next five to 10 years
Dr Steve Bollen
British Orthopaedic Sports Trauma Association

The researchers say the technique holds out promise of effective new treatments for a range on injuries, including those to the anterior cruciate ligament and the rotator cuff.

Tendons are elastic cords that anchor muscle to bone and enable flexing muscle to move limbs.

Inflammation risk

In many standard repair attempts, surgeons implant an autograft, a piece of tendon from elsewhere in the same patient.

However, this technique carries a risk of inflammation and scarring, which can cause the implanted tendon to stick to the joint, rather than to glide across it.

These tendon adhesions can be painful, and permanently limit range of motion.

Attempts to use grafts from a donor have been bedevilled by problems with rejection.

And synthetic scaffolds have failed to match the mechanical strength of human tissue.

The latest technique uses donated, freeze dried implants, known as allografts, loaded with a gene therapy solution, which directed the recipient's cells to accept the graft and remodel it into living tissue.

The mice experiments showed that the use of allografts loaded with gene therapy solution led to significantly fewer adhesions.

At 28 days after surgery, the mice who received these implants had recovered nearly 65% of the normal range of motion.

In contrast, animals given an allograft loaded with a non-therapeutic gene had recovered only 35% of the normal range.

Work to do

Dr Regis O'Keefe, who also worked on the study, said: "Tendon is very durable.

"It could conceivably be freeze-dried, thawed and then freeze-dried again without damaging it.

"It could be left on shelves at tissue banks indefinitely and then shipped long distances."

"To get it ready for surgery, you would thaw it in a solution containing growth factors, cut it to size on the spot and implant it.

"While we acknowledge that this work is in mice, that there are differences between species and that more work needs to be done, we believe these results promise practical yet dramatic improvements in reconstructive surgery."

Dr Steve Bollen, president of the British Orthopaedic Sports Trauma Association, said allografts were used in the UK, but only for complex reconstruction and revision cases, and not accompanied by gene therapy.

He agreed that treatment to flexor tendon injuries in particular were plagued by adhesion problems.

He said: "Gene therapy is a field which is going to take off in a serious way over the next five to 10 years.

"It holds great promise for being to able to manipulate tissue to become more like that of the host, but it is still very early days."


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