Prevention of IGF-1 and TGFbeta stimulated type II collagen and decorin expression by bFGF and identification of IGF-1 mRNA transcripts in articular chondrocytes.
OBJECTIVE
the aim of this investigation was to establish whether the action of bFGF modulated the production of type II collagen, decorin and biglycan induced by IGF-1 or TGFbeta in porcine articular chondrocytes. In addition, the study would establish which multiple transcripts of IGF-1 were present in articular cartilage, and which growth factors influenced their expression.


METHODS
steady state levels of mRNA specific for IGF-1 and matrix proteins were extracted as total RNA from porcine articular chondrocytes and processed for Northern blot analysis. High-density cell monolayers were established in the presence of serum, then maintained in a serum-free state for up to 7 days with increasing doses of either IGF-1 or TGFbeta in the presence or absence of bFGF.


RESULTS
bFGF prevented the stimulation of type II collagen and decorin induced in the presence of IGF-1 or TGFbeta and up-regulated the production of biglycan in cultured chondrocytes without altering the gene expression of IGF-1. Four IGF-1 transcripts were found in cultured adherent chondrocytes, approximately 77% was present as a major 4.7kb transcript with lower levels of 7.6 (4%), 1.3 (11%) and 1.1 (8%) kb forms.


CONCLUSIONS
bFGF acts as an antagonist for the production of type II collagen and decorin and also acts as a strong inducer like IGF 1 and TGFbeta for the expression of biglycan in porcine cultured chondrocytes. The apparent lack of a dose and time effect on expression of the IGF-1 gene was surprising and may be due to the stability of the IGF-1 message.
Sonal
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Department of Matrix Biochemistry, Strangeways Research Laboratory, CB1, 8RN, Cambridge, UK. sonal@desai-abram.org
D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D003094:Collagen / Q000235:genetics*; D058575:Decorin; D004305:Dose-Response Relationship, Drug; D016326:Extracellular Matrix Proteins; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000494:pharmacology*; D011509:Proteoglycans / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D013552:Swine; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D058575:Decorin; D016326:Extracellular Matrix Proteins; D011509:Proteoglycans; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016222:Fibroblast Growth Factor 2; D007334:Insulin-Like Growth Factor I; D003094:Collagen