Engineering Cartilage for the Jaw Joint

Arthritis of the temporomandibular joint (TMJ; the jaw joint) can restrict mouth movement, making eating, talking and yawning severely painful. Engineering cartilage and bone to replace the damaged mandibular condyle – the tip of the lower jaw bone that comes in contact with the skull base – is a goal for the future, the initial stages of which have already begun.

What Problem Was Studied?

To engineer cartilage tissue, cells are seeded onto a scaffold, placed in a medium that encourages their growth and maturation into adult cartilage cells, and inserted into the joint to replace the damaged cartilage. Arthritis Foundation-funded scientist Michael S. Detamore, PhD, of the University of Kansas in Lawrence, and colleagues have set out to determine the best cells to use for seeding the scaffold.

Mature chondrocytes (cartilage cells) can be harvested from one joint, seeded onto a matrix or scaffold and grown for potential replacement into another joint. This method is limited for a few reasons: It requires two invasive procedures; a sufficient amount of cartilage is difficult to obtain; and chondrocytes have a limited ability to grow in the lab. Adult mesenchymal stem cells derived from bone marrow can differentiate into several different cell types, including bone and cartilage, when exposed to specific growth factors. These cells grow well in culture, but the trouble is that harvesting bone marrow stem cells requires a painful surgical procedure and the cells are in limited supply. It has also been shown that stem cells from human umbilical cord matrix (HUCM) may have the capacity to differentiate into bone and cartilage cells. HUCM stem cells have several advantages – they are easily obtained, are in abundant supply, the donor has no pain or injury, and they can be grown in culture and stored frozen for years.

Detamore and colleagues ran an experiment to compare mature chondrocytes and HUCM stem cells to determine which holds more promise for engineering cartilage for the jaw joint.

What Was Done in the Study?

Human umbilical cords were obtained from an obstetrician and HUCM stem cells were separated and retained. A hog’s mandibular condyle was obtained from a butcher and the chondrocytes were separated and retained. The HUCM cells were divided into two batches, one was grown in a control medium and one was grown in a growth medium that encourages the cells to differentiate into chondrocytes. Likewise, the mature chondrocytes were divided into two batches and grown under the same conditions as the HUCM cells. After an initial incubation, the cells were seeded onto scaffolds and allowed to grow in their respective media again.

What Were the Study Results?

Despite beginning with equivalent cell numbers, the HUCM stem cell cultures grew to about twice the number of cells of the chondrocyte cell cultures by the end of the experiment. The cells grew in the control medium and the growth factor medium equally well. Detamore was also able to determine that HUCM stem cells had a greater potential to produce an extracellular matrix – as estimated by the amount of collagen and glycosaminoglycans (GAGs) produced by the cells – than did the chondrocyte cells. The extracellular matrix gives the cartilage its structure and strength.

What Does This Mean for the Future of Tissue Engineering?

According to Detamore, “The higher amount of collagen and GAGs present in the HUCM cultures, in addition to the higher cell numbers in the HUCM constructs, indicate that the HUCM stem cells may be a better candidate for cartilage tissue engineering applications than the TMJ condylar chondrocytes. Based on the difficulty in obtaining donor cartilage for tissue engineering applications, and the superior biosynthetic activity by HUCM stem cells,” Detamore concludes, “HUCM stem cells may have a significant potential therapeutic value for tissue engineering applications in the future.” The research team’s next steps will be to refine the growth factor medium for the HUCM cells and to compare those cells to stem cells derived from bone marrow.

Bailey MM,Wand L, Bode CJ, Mitchell KE, Detamore MS. A comparison of human umbilical cord matrix stem cells and temporomandibular joint condylar chondrocytes for tissue engineering temporomandibular joint condylar cartilage. Tissue Engineering 2007; 13:2003–10.

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