title: Absence of feedback regulation in the synthesis of COL1A1.
abstract: OBJECTIVE
  Recent studies have emphasized the importance of the extracellular microenvironment in modulating cell growth, motility, and signalling. In this study we have evaluated the ability of a fibroblast derived-extracellular matrix (fd-ECM) to regulate type I collagen synthesis and degradation in fibroblasts.
  
  
  METHODS
  Fibroblasts were plated on plastic (control) or on fd-ECM and type I collagen synthesis and degradation was evaluated. MTT, western blotting, real time PCR, zymographic analysis and inhibitor assays were utilised to investigate the molecular mechanism of type I collagen regulation by the fd-ECM.
  
  
  RESULTS
  Fibroblasts plated on fd-ECM showed significant downregulation in the production of type I collagen and COL1A2 messenger ribonucleic acid (mRNA) whilst COL1A1 mRNA remained unchanged. Cells grown on fd-ECM exhibited increased matrix metalloproteases (MMPs) and their corresponding mRNAs. The use of transforming growth factor β (TGF-β) and MMP inhibitors showed that the excess COL1A1 polypeptide chains were degraded by the combined action of MMP-1, MMP-2, MMP-9 and cathepsins.
  
  
  CONCLUSIONS
  These results show the crucial role played by proteases in regulating extracellular matrix protein levels in the feedback regulation of connective tissue gene expression.
authors.affiliation: International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town Component, Wernher and Beit Building (South), UCT Campus, Anzio Road, Observatory 7925, Cape Town, South Africa; Division of Medical Biochemistry and MRC Oesophageal Cancer Unit, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
authors.forename: Kevin
authors.initials: K
authors.lastname: Dzobo
authors.affiliation: Division of Medical Biochemistry and MRC Oesophageal Cancer Unit, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
authors.forename: Virna D
authors.initials: VD
authors.lastname: Leaner
authors.affiliation: International Centre for Genetic Engineering and Biotechnology (ICGEB), Cape Town Component, Wernher and Beit Building (South), UCT Campus, Anzio Road, Observatory 7925, Cape Town, South Africa; Division of Medical Biochemistry and MRC Oesophageal Cancer Unit, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa. Electronic address: iqbal.parker@icgeb.org.
authors.forename: M Iqbal
authors.initials: MI
authors.lastname: Parker
mesh_terms: D002403:Cathepsins / Q000378:metabolism; D002460:Cell Line; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000090602:Collagen Type I, alpha 1 Chain; D005109:Extracellular Matrix / Q000502:physiology*; D025461:Feedback, Physiological; D005347:Fibroblasts / Q000378:metabolism* / Q000648:ultrastructure; D005786:Gene Expression Regulation; D006801:Humans; D020781:Matrix Metalloproteinase 1 / Q000235:genetics / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D061965:Matrix Metalloproteinase Inhibitors; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D002403:Cathepsins; D020782:Matrix Metalloproteinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1
keywords: Collagen turnover; Extracellular matrix; Feedback regulation; Type I collagen synthesis