The researchers made five kinds of sheets. Those filled with: sparsely cross-linked microspheres containing growth factor, highly cross-linked microspheres containing growth factor, sparsely cross-linked microspheres with no growth factor, highly cross-linked microspheres with no growth factor, and a control with no microspheres. The last three were grown in baths containing growth factor.
After three weeks in a petri dish, all sheets containing microspheres were thicker and more resilient than the control sheet. The sheet with sparsely crosslinked microspheres grew into the thickest and most resilient neocartilage.
The results indicate that the sparsely cross-linked microspheres, which degraded more rapidly by cell-secreted enzymes, provided a continuous supply of growth factor throughout the sheets that enhanced the uniformity, extent, and rate of stem cell differentiation into cartilage cells, or chondrocytes.
The tissue appeared grossly similar to articular cartilage, the tough cartilage found in the knee: rounded cells surrounded by large amounts of a matrix containing glycosaminoglycans. Called GAG for short, the carbohydrate locks water ions in the tissue, which makes the tissue pressure-resistant.
Testing also showed that this sheet had the highest amount of type II collagen the main protein component of articular cartilage.
Although the sheet was significantly stiffer than control sheets, the mechanics still fell short of native cartilage. Alsberg's team is now working on a variety of ways to optimize the process and make replacement cartilage tough enough for the wear and tear of daily life.
One major advantage of this system is that it may avoid the troubles and expense of growing
|Contact: Kevin Mayhood|
Case Western Reserve University