Taking "chemical photographs" of the cartilage between joints and comparing them to engineered versions could lead to better implants, say researchers.
Articular cartilage is the smooth, white tissue that covers the ends of bones where they come together to form joints, allowing the bones to glide over each other with little friction. In the UK, 8.75 million people suffer osteoarthritis, which is associated with damage to their articular cartilage and can lead to a range of treatments, including joint replacements.
In regenerative medicine, scientists are exploring ways of growing cartilage-like material that could replace damaged real cartilage. However, researchers have so far not been able to successfully mimic the complex structure of natural articular cartilage in the lab.
Scientists led by Molly Stevens, professor of biomedical materials and regenerative medicine at Imperial College London, have been growing cartilage-like material using cells seeded onto scaffolds made from a biologically compatible material. Now, they are using Raman spectroscopy, a form of biochemical analysis using the properties of light, to compare how close their engineered cartilage is to the real thing.
Raman spectroscopy involves using lasers to image the structural and chemical composition of samples at the molecular level. The team compared 10 natural articular cartilage samples with 18 engineered cartilage samples and was able to accurately map human cartilage, which they compared to the engineered cartilage at various stages while it is being grown in the lab.
Articular cartilage has previously been classified as having three distinct zones but, using Raman spectroscopy, the team was able to image at least six different layers. They mapped the distribution throughout the layers of the three main components in human cartilage—water, a group of sugars called glycosaminoglycan and collagen—and were also able to image how the collagen fibers were oriented, which is important for understanding cartilage’s mechanical properties.
Using Raman spectroscopy, the researchers were also able to determine at very high resolutions the chemical composition of each engineered sample. They looked at important indicators during the growth of the engineered cartilage samples, such as the amounts of collagen and water compared to the real samples, which indicate how closely they approximate actual cartilage.
The next step will see the team utilizing Raman spectroscopy to systematically evaluate the conditions in the lab that can influence the growth of articular cartilage. They hope that this will allow them to identify the settings that improve conditions for engineering tissue so that it conforms more accurately to the structure of natural cartilage.