"Adhesion rates and chondrocyte phenotype in monolayer cultures under the influence of Collagen type II and IGF-I "

Abstract

When grown in monolayer culture at low density and with the addition of serum, cartilage cells dedifferentiate or are overgrown by fibroblast-like cells. The aim of this study was to optimize the cultivation of chondrocytes in monolayer culture and to slow down their transformation or their overgrowth by fibroblast-like cells. The interaction between chondrocytes and cartilage-specifc matrix is mediated largely by the β1 subfamily of integrin receptors. This interaction can be regulated or synergized by growth factors, such as IGF-I, which stimulates many chondrocyte functions.For this reason isolated chondrocytes of cartilage anlagen from 17- day old mouse embryos were grown on collagen type II-coated substrates with or without the addition of IGF-I (Insulin like Growth Factor-I) Using this model chondrocytes grown on collagen type II with or without IGF-I maintained their round phenotype until the end of cultivation. The neutral red assay revealed that chondrocytes cultivated on collagen type II in the presence of exogenous IGF-I, showed a significantly higher density of chondrocye adhesion from the beginnig of cultivation onwards in comparison to chondrocytes cultivated on collagen type II without IGF-I treatment. The cartilage-specific surface receptors (integrins of the β1- group) could also be demonstrated on the membrane of these cells. Chondrocytes cultivated on plastic with or without treatment with IGF-I, resulted in mixed cultures consisting of fibroblast-like cells and round chondrocytes as observed from the beginning of cultivation onwards. After a 3 to 5 culture period, flat fibroblast-like cells predominated.Hence, collagen type II and IGF-I prevent chondrocyte dedifferentiation to fibroblastike cells and this model allows a pure chondrocyte culture.