Touching Lives - September 2003
Growing your own knee cartilage!
Dr Mohammed Akmal is a surgeon who is also involved in developing tissue engineering techniques. With Action Medical Research funding, he and his team have successfully developed a technique to grow knee cartilage.
Cartilage is a tough, fibrous connective tissue with excellent shock absorbing qualities. It is also found in other joints such as the ankle, hip and shoulders and provides a smooth protective surface for ease of movement.
Damage to cartilage in the knee usually happens when people are playing sports and they twist or fall badly. Around 10,000 people each year suffer from cartilage damage as a result of injury, often from football, tennis or skiing.
It has been long recognised that once damaged, cartilage fails to heal or renew itself due mainly to an absence of blood supply. In the worst scenario it can lead to osteoarthritis where the bones rub against one another — a hugely painful condition.
But total knee replacement is not a satisfactory solution in young people as the prosthesis is prone to infection and wear which may lead ultimately to more extensive and risky revision surgery. Current techniques to deal with cartilage damage involve creating bleeding within the joint which results in a blood clot on the surface of the bone.
Under the stimulus of movement and weight the blood clot transforms into a form of primitive cartilage, but because it is not the same quality as the original cartilage it does not last very long but will provide some relief to the patient.
In the bioreactor
With only these inadequate options, the race was on to find a way to grow cartilage more effectively. The team at Stanmore found that such growth is best promoted by using a special device called a bio-reactor.
A small number of cartilage cells are harvested from a non-weightbearing portion of the knee joint during the patient’s initial examination. These cells are then cultured in the laboratory to produce much larger numbers before being re-implanted into the defective area of the knee joint.
Using your own cells for the operation has the advantage of lessening the risk of infection and preventing rejection. The cells grow within the bio-reactor in a compartment that holds special ‘food’ which the cells need to grow. The machine revolves constantly and this motion stimulates cells to grow in the best way as they receive the right amount of nutrients.
Millions of cells
Once matured the culture process produces new cartilage-like pellets which may be used for implantation. It takes up to two and a half weeks to grow enough cells to be transplanted and many millions of cells are needed to repair just a small defect.
Dr Akmal told Touching Lives, “This Action Medical Research grant has really helped us to better understand what cells do and thereby improve the techniques of growing them for the purpose of implantation.
“The traditional method of growing cells involves having them in static flat culture plates, but this means that cells fail to get enough food for normal development. Using the bioreactor enables us to successfully grow a much greater number of cells which are of much better quality and resemble those of normal joint cartilage.
“Having the best cartilage to work with means that patients should have a better outcome. And the cost of making the cells, the operation and the rehabilitation is about the same as having a total knee replacement. But ^the real advantage of using a patient’s own cells in this way is that it is a far less invasive procedure and patients should be up and about much quicker^.
“The technology that we have developed could also be applied to other body tissues and may prove to be a critical step in human tissue engineering. Skin, kidney and liver cells can already be grown with great success and there is also progress in using a patient’s own stem cells from the bone marrow. The potential to repair spinal discs in patients with backpain is now on the horizon, which we intend to investigate.”