Perfusion bioreactor studies of chondrocyte growth in alginate-chitosan capsules

The combination of progenitor cells, cell-friendly scaffold, and a three-dimensional culture system has been investigated for the culture of cartilage tissue. We have assessed chondrogenesis of alginate-chitosan-encapsulated STRO-1-isolated human mesenchymal progenitor cells. In addition, ATDC-5 cells and human articular chondrocytes were also evaluated. We have used a novel 3D bioreactor system that enabled perfusion of the capsules with culture medium up to 28 days. Results from culturing all cell types indicated chondrogenesis, both in static and bioreactor culture. The expression of SOX-9 and type II collagen was examined as a marker of differentiation. ATDC-5s expressed both SOX-9 and type II collagen under perfused and static culture conditions. In monolayer cell culture, human articular chondrocytes did not express either SOX-9 or type II collagen and STRO-1 expressed alkaline phosphatase, indicating osteogenesis. However, when these cells were encapsulated in alginate-chitosan, both expressed SOX-9 under static and perfused cultures, but type II collagen was only expressed under perfused culture conditions. We have also noted that the perfusion rates used were too low to ensure a significant advantage over static culture, but that use of the bioreactor eliminated the need for manual feeding and intervention of the cells over the 28-day period.