This study is published in the latest issue of the journal Molecular Therapy and the following news article is published by CBC News.

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Tricky tendon injuries may soon be repaired using donated, freeze-dried tendons loaded with genes that will help reorganize the growth of new tissue, a U.S. study has found.

Use of the tendons in lab mice shows promise for repairing flexor tendons in human hands, anterior cruciate ligaments of the knee and rotator cuffs in the shoulders, scientists say.

Tendons connect muscle to bone and allow muscles to flex. Injuries to tendons are common and often lead to complicated surgical interventions in which tendons from other parts of the body are grafted in a process called “autograft,” according to researchers. This can lead to inflammation and infection in both graft sites, causing scar tissue formation, adhesions of normally separated tissue surfaces and limited mobility at a later stage.

Allografts, in which another person donates a tendon, are often rejected by the graft recipient, as the body deems the tissue foreign and attacks it. Gel and fibre-mesh synthetics have failed to match the strength of human tissue, the study’s authors say.

Researchers at the University of Rochester Medical Center in Rochester, NY, studied how the implantation of an allograft that had been genetically rewired would fare in a mouse model. They found the genes in the allografts allowed for more ready acceptance on the part of the animal recipient, while producing fewer adhesions.

The mice with freeze-dried allografts plus gene therapy recovered double the range of motion when compared to the control group 14 days after surgery. Twenty-eight days following the graft, the allograft group had attained almost 65 per cent of the normal range of motion, versus the control group, which had recovered only 35 per cent of the normal range.

“Orthopedic surgeons have been searching for the perfect material to replace tendons, one with the right mix of strength and elasticity and [which] would not cause adhesion,” said Hani Awad, assistant professor of Biomedical Engineering and Orthopedics within the medical centre’s Center for Musculoskeletal Research, in a media release. “We believe the only material to meet these strict requirements is non-living, but structurally intact, tendon. ”

Scientists say that although the mice that received the allografts had to be immobilized to boost healing, in human grafts, people are typically given rehabilitation exercises to heal more quickly. Awad predicts that in the case of humans, who will participate in physiotherapy regimens, the healing will take place much faster.
In the future, pending the results of human tests, grafts may become a portable and easy-to-store solution to tendon injuries, he said.

“[The tendon] could conceivably be freeze-dried, thawed and then freeze-dried again without damaging it,” Awad said. “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.”