In vitro differentiation of neonatal foreskin fibroblasts to chondrocytes

Successful tissue engineering of articular cartilage is hampered by the lack of an abundant source of chondrocytic cells. To determine if differentiated cells can be "re-differentiated" to a chondrocytic phenotype, neonatal fibroblastic foreskin cells were cultured in monolayers on wells coated with either the cartilage proteoglycan aggrecan in PBS, or with PBS alone. Cells were cultured for four weeks, with weekly data collection points. Cells were examined for mRNA expression of collagen type II and aggrecan, matrix protein expression by Safranin O staining and Col II protein expression by immunohistochemistry. Results show that cells cultured on aggrecan initiate mRNA expression of the matrix proteins by one week. Safranin O staining is also positive, although Col II protein levels are low. At two weeks, cells maintain the mRNA expression and Safranin O staining and the Col II protein levels are seen to increase. At the three and four week periods, the message and protein levels appear stable, while the morphology of the cells changes somewhat. Smaller aggregates are either incorporated into larger existing aggregates, increase their attachments to the culture surface or die. The physiologically relevant levels of Col II message and protein can be determined by comparison with native tissue.