Washington, June 5 : Bioengineers at Rice University are on the path to providing relief to millions of arthritis sufferers with the development of a new method to regenerate cartilage cells from existing cells.
The scientists led by Kyriacos Athanasiou, Rice's Karl F. Hasselmann Professor of Bioengineering, have said that intense pressure -- similar to what someone would experience more than a half-mile beneath the ocean's surface -- stimulates cartilage cells to grow new tissue and that too without using stem cells.
"This tissue-engineering method holds promise not only for cartilage but also for tissues to repair bladders, blood vessels, kidneys, heart valves, bones and more," said Athanasiou.
Cartilage is a tissue in the human body that cannot heal itself, and has long been a target of tissue engineers. Cartilage is the skeleton's shock absorber, and its stiffness, strength and other mechanical properties derive not from living cartilage cells but from the densely woven matrix of collagen and proteoglycan that surrounds them. This extracellular matrix, or ECM, is produced during cartilage development in children, but cannot be repaired following injury in adulthood.
Usually, injured cartilage is the main reason for causing arthritis, so tissue engineers have long sought a means of growing new cartilage that can be transplanted into adults to repair damaged joints before arthritis can develop. However, cartilage is difficult to engineer as there are no natural healing processes to mimic.
For more than 10 years, Athanasiou has studied cartilage in his Musculoskeletal Bioengineering Laboratory, and said that the new process is the first one to produce cartilage that's almost identical to the body's own tissue.
"The combination of hydrostatic pressure and growth factors used in this process result in an engineered cartilage ECM with properties nearly identical to that of native cartilage. This research appears very promising for treating arthritis, as cartilage can now be produced in our lab that is almost identical in composition to native tissue," he said.
Till date, the bioengineers have only tried this method in cells from cows and according to Athanasiou, it will still take a long time to be tested in humans. However, the new findings are based on three years of data collected by graduate student Benjamin Elder.
In the study, Elder took small samples of cartilage from calves' knees, dissolved the ECM and isolated the living cartilage cells, or chondrocytes. Then the used the calf chondrocytes to create tissue-engineered cartilage, which was then placed into a chemical bath of growth factors and sealed inside soft plastic containers that were placed inside a chamber connected to a hydraulic press. This was followed by squeezing the bags at intense pressures for one hour per day.
"Our knees are filled with fluid, and when we walk or run the hydrostatic pressure on the cartilage cells in the knee approaches the pressures we used in our experiments. But in daily activities, these pressures are fleeting, just a second or so at a time," said Elder.
Majority of current strategies in tissue engineering, aim at reproducing the conditions that cells experience in the body, while Athanasiou said that the unconventional approach of using unnaturally high-pressure stemmed from insights gained during years of previous experiments.
Elder said: "By combining high pressure and growth factors, we were able to more than triple the biomechanical properties of the cartilage. We're not sure why they reinforce one another, but we do not get the same results when we apply them independently."
The findings of the study appear in the journal PLoS ONE.