Transforming growth factor‐β1 (TGF‐β1) regulates ATDC5 chondrogenic differentiation and fibronectin isoform expression

Abstract

Regulated splicing of fibronectin (FN) occurs during the mesenchymal to chondrocyte transition and ultimately results in the relative enrichment of an extra domain B (EDB) exon-containing FN isoform with the suggestion that FN isoforms may play a functional role in chondrogenesis. Promotion of chondrogenesis can also be achieved by treatment with transforming growth factor-beta (TGF-beta), which also regulates FN isoform expression. We have examined the effects of TGF-beta treatment on the assumption of the chondrogenic phenotype in the teratoma-derived cell line ATDC5 and tested whether these effects on chondrogenesis are paralleled by appropriate changes in FN isoform expression. ATDC5 cells were maintained in a pre-chondrogenic state and, in this state, treated with 10 ng/ml TGF-beta. The cells started to elaborate a matrix rich in sulfated proteoglycans, such that within the first 12 days of culture, TGF-beta1 treatment appeared to slightly accelerate early acquisition of an Alcian blue-stained matrix, and caused a dose- and time-dependent decrease in collagen type I expression; changes in collagen type II expression were variable. At later times, cells treated with TGF-beta became indistinguishable from those of the controls. Interestingly, TGF-beta treatment caused a significant dose- and time-dependent decrease in the proportion of FN containing the extra domain A (EDA) and the EDB exons. These data suggest that TGF-beta induces the early stages of chondrogenic maturation in this pre-chondrogenic line and that TGF-beta treatment increases expression of FN isoforms that lack the EDA and EDB exons.

Changes in the Chondrocyte and Extracellular Matrix Proteome during Post-natal Mouse Cartilage Development

“…These results support a role for TGF␤1 signaling during early cartilage development in vivo, consistent with the positive effect of TGF␤1 on the differentiation of mesenchymal chondrocyte precursors in vitro (49,50). Altered TGF␤1 signaling is implicated in cartilage degeneration associated with aging and arthritis (51), and pathologic changes in cartilage homeostasis and chondrocyte phenotype include re-expression of early markers of cartilage development.…”

The ShcA PTB Domain Functions as a Biological Sensor of Phosphotyrosine Signaling during Breast Cancer Progression

“…A constant annealing temperature of 60 C was used for all reactions. Expression levels of the FN-EDA and FN-EDB alternatively spliced variants were determined as previously described (14).…”

Activation of epidermal growth factor receptor gene is involved in transforming growth factor-β-mediated fibronectin expression in a chondrocyte progenitor cell line

“…FN expression is increased in areas of cellular condensation that are decreased as cytodifferentiation proceeds (27,28). According to recent studies, isoform switching of Fn mRNA is important for chondrogenic differentiation (29)(30)(31) and that TGF-ß1 treatment during chondrogenic differentiation of ATDC5 cells increases the expression of FN isoforms that lack the extra domainA and B during chondrogenic differentiation of ATDC5 cells (32,33). Regulation of both quantity and quality of FN by TGF-ß1 could be involved in the early stage of chondrogenesis.…”