Mandibular Condyle Created from Rat Stem Cells

In a new feat of tissue engineering, a team of clinicians, dentists, surgeons, cell biologists, and materials scientists has created a mandibular condyle from rat stem cells that is the precise three-dimensional shape of the human joint. Their work was reported in the December 2003 issue of the Journal of Dental Research.

A mandibular condyle is the knobbed ending of the lower jaw that joins the lower jaw to the temporal bone of the skull on both sides of the head at the temporomandibular joint (TMJ). The team isolated adult mesenchymal stem cells from rat bone marrow, then treated them in the laboratory to differentiate into either bone or cartilage-producing cells called osteoblasts and chondrocytes. Each adult mesenchymal stem cell can produce thousands of osteoblasts or chondrocytes.

Next, the team seeded the differentiated cells into a hydrogel polymer solution and placed the creation in a polyurethane mold made from a human mandibular condyle. The team then implanted three small molded structures just below the skin of severe combined immunodeficient (SCID) mice. Each implant was encapsulated in a hydrogel coat subdivided into layers seeded either with osteoblasts or chondrocytes. Eight weeks later, the team harvested the three tissue-engineered condyles from the mice. The implants had formed on their own into structures that retained the precise shape and three-dimensional structure of the molded human mandibular condyle. Within the layer of implants were mineral deposits in island structures, a sign that the osteoblasts had followed their biologic program and produced bone.

"We began our research using mice that were not larger than a human hand, and obviously it wasn't possible to engineer a large human tibia or femur that way,” explained Adel Alhadlaq, D.D.S., M.S., a coauthor of the paper who is a scientist at the University of Illinois at Chicago (USA; www.uic.edu). "Because the mandibular condyle is smaller and could be transplanted into a mouse, it was just a practical structure to try and engineer.”




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