May 23, 2005
A team of NIDCR grantees last year reported engineering a properly shaped articular condyle, the ball of bone and cartilage that inserts into the socket of a joint, from a single population of rat adult stem cells. The scientists noted that the findings served as “a primitive proof of concept,” and, with further refinement, the approach could one day provide the scientific basis for tissue engineered replacement joints. One of the questions that jumped out at them from their feasability study was: How densely must they encapsulate the stem cells within the shape-producing, three-dimensional hydrogel mold to form a functional articular condyle? Finding the answer would help them attain the needed mechanical strength of the condyle, a major requirement for a tissue engineered structure. As published in the May 20 issue of the Journal of Bone and Joint Surgery, the scientists reported increasing their single population of stem cells to 20 million per milliliter - a substantial increase from the 5 million per milliliter in the initial study. The scientists then implanted the more cell-dense condyle into mice for 12 weeks compared to four weeks in their earlier study. The group found at the end of the 12-week period that the condyle showed signs of greater tissue maturation than the tissue engineered structure in their previous work. The authors noted that “much additional work is warranted on several fronts” but their results mark another step forward on the road to a tissue engineered articular condyle.