British scientists at the University of Bristol report some success with cell therapy to repair osteoarthritis damage in knees.

Knee cartilage injuries can be effectively repaired by tissue engineering and osteoarthritis does not stop the regeneration process concludes research led by scientists at the University of Bristol.

The study, "Maturation of tissue engineered cartilage implanted in injured and osteoarthritic human knees", published in the July 2006 (Volume 12, Number 7) issue of Tissue Engineering, demonstrates that engineered cartilage tissue can grow and mature when implanted into patients with a knee injury. The novel tissue engineering approach can lead to cartilage regeneration even in knees affected by osteoarthritis.

They grew cells extracted from the same persons they implanted cells back into. This approach avoids immune rejection problems.

The tissue engineering method used in this study involved isolating cells from healthy cartilage removed during surgery from 23 patients with an average age of 36 years. After growing the cells in culture for 14 days, the researchers seeded them onto scaffolds made of esterified hyaluronic acid, grew them for another 14 days on the scaffolds, and then implanted them into the injured knees of the study patients.

Cartilage regeneration was seen in ten of 23 patients, including in some patients with pre-existing early osteoarthritis of the knee secondary to traumatic injury. Maturation of the implanted, tissue-engineered cartilage was evident as early as 11 months after implantation.

Antony Hollander, ARC Professor of Rheumatology & Tissue Engineering at Bristol University who led the study, said: "This is the first time we have shown that tissue-engineered cartilage implanted into knees can mature within 12 months after implantation, even in joints showing signs of osteoarthritis.

Initial tissue engineering successes will accelerate the rate of advance of tissue engineering and stem cell therapies. Experience gained from scaling up and automating cell therapy delivery will lead to discoveries for how to refine and improve processes for handling cells. The revenue from stem cell therapy delivery will fund more development.

Many steps had be worked out to go from extraction to reimplantation of cells.

Although the researchers did not carry out physical tests of the patient’s mobility, these testing techniques have previously been shown to provide a good indicator of the cartilage's function, suggesting movement should be improved too. The reason why not all patients benefited from the engineered cartilage is not yet clear, although Hollander says giving the engineered tissue longer to settle in may help.

The new study is a "textbook example" of how tissue engineering should work, says Julian Chaudhuri, a tissue engineer working on cartilage at Bath University, UK. "Every step is in place from growing the tissue to implanting in patients, and it's been shown to work," he says. "It looks very exciting."

A December 2005 report on Hollander's progress shows he managed to grow human cartilage outside of the body.

Professor Anthony Hollander and his team at Southmead Hospital have successfully grown human cartilage from a patient's own stem cells for the first time ever.

This means people suffering from the severe form of the bone disease osteoarthritis, which leaves them unable to walk, could in the future have cartilage transplant operations.

Scientists took stem cells from the bone marrow of pensioners undergoing NHS replacement operations because they have arthritis.

They took just over a month to grow the cells into a half-inch length of cartilage.

An American team is pursuing a stem cell approach using a single donor for many patients.

Stem cell therapy — a technique that relies on the idea that stem cells can be prompted to turn into cartilage cells that will grow and repair damage — is another possible avenue for future treatment. Johns Hopkins researcher Jennifer Elisseeff has used the method in rats, finding that stem cells can fill in holes in the cartilage.

"These cells have the amazing ability to repair parts of the body," says Thomas Vangsness, an orthopedic surgeon at the University of Southern California in Los Angeles.

Vangsness and his colleagues are testing a stem cell therapy developed by Osiris Therapeutics. The Baltimore company has developed a solution of stem cells taken from a single adult donor. Vangsness and his colleagues injected the stem cell solution into the knees of 55 patients with a torn meniscus, cartilage-like tissue in the knee. They're hoping the stem cells will turn into cartilage cells and repair the injury, but the data are just now being analyzed, Vangsness says.

With multiple teams doing human clinical trials the development of successful joint repair using cell therapies no longer seems a distant prospect.