To test the implants, researchers injected them into the backs of rats. They then tested several ratios of the hyaluronic acid and polyethylene glycol, examining how long each lasted. The various blends have different levels of elasticity and durability, allowing clinicians to fine-tune the physical properties of an implant for their needs. The longest-lasting implants made it for almost 500 days before being completely resorbed into the rats’ bodies. This means the implants may have to be replaced after a year or so, although Elisseeff hopes that they will act as a scaffolding for new tissue to grow on.
The researchers staged a pilot clinical study in Canada. They injected small implants in the stomachs of three patients scheduled to undergo “tummy tucks.” The implants lasted about 12 weeks, with the only problem being inflammation around the implant. Elisseeff says the inflammation could be a result of irritation caused by the rigidity of the implants, a reaction to the chemicals in the implant, or a by-product of the fat tissue surrounding the implant site. She thinks the problem will be “relatively easy to overcome.”
The next step, says Elisseeff, is a full-scale clinical trial. She’s also working on ways to make soft-tissue implants with minimal synthetic components. “The long view is trying to bring these [tissue engineering] technologies forward to clinical practice,” she says. Although it’s typically taken a long time to get such techniques into use, she’s confident her current work will move to the clinic because “it’s designed to address clinical needs.”
Melissa Knothe Tate, a professor in Case Western University’s Department of Biomedical Engineering, is optimistic. “Getting functional tissue in the right place at the right time has been a major hurdle in the field of tissue engineering,” she says. She adds that this and other recently published technologies could indicate “a new age of regenerative medicine, mimicking the body’s capacity to build new tissue.”
Khademhosseini also finds the results encouraging. “I am hopeful that the paper will yield to a new generation of biomaterials-based applications in soft-tissue replacement,” he says.