Scientists have created mandibular condyles from rat adult stem cells that are the precise three-dimensional shape of the human joint, according to a study published in the December issue of the Journal of Dental Research.
Studies in tissue engineering—using the body’s own biological materials to repair, regenerate and replace damaged organs and tissues, including bone and cartilage—have focused on the initial step of repairing a small area of damaged tissue.
Two years ago, Dr. Jeremy Mao, study co-author and a scientist at the University of Illinois at Chicago, and colleagues took the next step and engineered a mandibular condyle. They isolated adult mesenchymal stem cells from rat bone marrow, and then treated the cells in the laboratory to differentiate them into either bone-producing or cartilage-producing cells called osteoblasts and chondrocytes, respectively.
Researchers then seeded the differentiated cells into a hydrogel polymer solution in stratified layers. The seeded solution was molded into the shape of a human mandibular condyle. Researchers implanted three small molded structures just below the skin of immunodeficient mice.
At eight weeks, researchers harvested the three tissue-engineered condyles from the mice. They found that the implants had formed on their own into "firm" structures that retained the precise shape and three-dimensional structure of the molded human mandibular condyle.
They also found that the osteoblasts had produced bone, and they identified "sparse chondrocyte-like cells within abundant extracellular matrix" that expressed certain proteins characteristic of cartilage.
Stressing that their findings are preliminary, researchers said they are hopeful because they produced the structures from a single population of stem cells and prompted them to form two distinct layers of bone and cartilage. They plan to attempt to enhance the biological and mechanical properties of the tissue-engineered condyles. Dr. Mao, however, said that these results are just the start of a much bigger scientific challenge.
"It is no small task to recapitulate what nature does perfectly during development," he said. "Although we understand many of these cues during natural development, we need to learn how to utilize them to tissue engineer mandibular condyles."
