Effects of Cytoskeleton Modulation on the Phenotype of Articular Chondrocytes in Monolayer and Pellet Culture

Previous studies have shown that chondrocytes in 2D culture are capable of keeping chondrocytic phenotype when formation of actin stress fiber is chemically restrained by cytochalasin; chondrocytes in 3D culture normally express better chondrogenic phenotype than in 2D, because formation of actin stress fiber is physically inhibited by cell aggregation instead of cell spreading. Besides actin, another cytoskeletal protein vimentin has also been shown to affect chondrocyte phenotype. These findings indicate that the chondrogenic expression of chondrocytes is associated with cytoskeleton organization. To systematically investigate the effects of cytoskeleton modulation on chondrocyte phenotype, here we cultured rabbit articular chondrocytes in 2D monolayer and 3D pellet, disrupted vimentin, tubulin, or actin network respectively, and measured the changes of chondrocyte phenotype. We found that vimentin disruption induced a reduction of type II collagen and aggrecan, and the extent was greater for chondrocytes in 3D than in 2D; tubulin disruption showed little effects on chondrocyte phenotype; actin disruption only promoted the expression of type II collagen for chondrocytes in 2D not in 3D. Our findings suggest a critical role of vimentin in the maintenance of chondrocyte phenotype, and further provide insights toward in vitro phenotype manipulation.