A research team from Umeå University in Sweden has used cartilage cells isolated from the knee joints of cows engineer joint-specific cartilage. Such a technique might lead to a novel stem cell-based tissue engineering treatment for osteoarthritis.
Hyaline cartilage is a specific type of cartilage found at joints where bones come together. Hyaline cartilage is a tough, pliable shock absorber, but because it is poorly supplied by blood vessels its capacity to regenerate is also poor. Knee injuries and the everyday wear-and-tear wear down cartilage tissue and might lead to a condition called osteoarthritis. In Sweden along, 26.6 percent of all people age 45 years or older were diagnosed with osteoarthritis. According to the Centers for Disease Control, in the United States, osteoarthritis affects 13.9% of adults aged 25 years and older and 33.6% (12.4 million) of those older than 65 in 2005; an estimated 26.9 million US adults in 2005 up from 21 million in 1990 (believed to be conservative estimate). Serious osteoarthritis cases can involve the loss of practically the entire cartilage tissue in the joint. Osteoarthritis causes pain and immobility in patients, but it also burdens society with accumulated medical costs.
“There is currently no good cure for osteoarthritis,” says Janne Ylärinne, doctoral student at the Department of Integrative Medical Biology. “Surgical treatments may help when the damage to the cartilage is relatively minor, whereas joint replacement surgery is the only available solution for people with larger cartilage damage. However, artificial joints only last for a couple of decades, making the surgery unsuitable for young persons. So we need a more permanent solution.”
Fortunately, tissue engineering might provide way to successfully treat osteoarthritis. Ylärinne and his colleagues developed new methods to produce cartilage-like “neotissues” in the laboratory.
Normally, tissue engineering methods that grow cartilage use cartilage-making cells, signaling molecules such a growth factors, and some sort of three-dimensional scaffold that acts as an artificial support system that makes the culture system more realistic for the cells. Unfortunately, such protocols are difficult, inexact, and generate respectable variation in what they produce. Consequently, it is also unclear whether stem cells or primary cells are best suited for cartilage tissue engineering experiments.
In these experiments, Ylärinne and others used primary cow chondrocytes (cartilage-making cells from cows) to which they successfully devised improved methods for growing cartilage tissue in a laboratory environment. The cartilage made by Ylärinne and others is similar to that normally present in the human joints.
In the future, protocols like this one might help the development of neocartilage production for actual cartilage repair. If this protocol or others like it can be adapted to stem cells rather than primary cartilage cells, then perhaps these cells can be grown to provide unlimited amount of material for tissue engineering. However, despite the hopefulness of this research, more research is needed to improve the tissue quality and make it more structurally similar to the hyaline cartilage found at human joints.