Mammalian chondrocytes expanded in the presence of fibroblast growth factor 2 maintain the ability to differentiate and regenerate three-dimensional cartilaginous tissue.

The differentiated phenotype of chondrocytes from hyaline cartilage is gradually lost during expansion in monolayers. Chondrocytes can reexpress their differentiated phenotype by transfer into an environment that prevents cell flattening, but serially passaged cells never completely recover their chondrogenic potential. We report that chondrocytes expanded (up to 2000-fold) in the presence of fibroblast growth factor 2 (FGF-2) dedifferentiated, but fully maintained their potential for redifferentiation in response to environmental changes. After seeding onto three-dimensional polymer scaffolds, chondrocytes expanded in the presence of FGF-2 formed cartilaginous tissue that was histologically and biochemically comparable to that obtained using primary chondrocytes, in contrast to chondrocytes expanded to the same degree but in the absence of FGF-2. The presence of FGF-2 inhibited the formation of thick F-actin structures, which otherwise formed during monolayer expansion, were maintained during tissue cultivation, and were associated with reduced ability of chondrocytes to reexpress their differentiated phenotype. This study provides evidence that FGF-2 maintains the chondrogenic potential during chondrocyte expansion in monolayers, possibly due to changes in the architecture of F-actin elements and allows more efficient utilization of harvested tissue for cartilage tissue engineering. Copyright 1999 Academic Press.