title: MMP-2 expression by fibroblasts is suppressed by the myofibroblast phenotype.
abstract: During wound healing, fibroblasts transition from quiescence to a migratory state, then to a contractile myofibroblast state associated with wound closure. We found that the myofibroblast phenotype, characterized by the expression of high levels of contractile proteins, suppresses the expression of the pro-migratory gene, MMP-2. Fibroblasts cultured in a 3-D collagen lattice and allowed to develop tension showed increased contractile protein expression and decreased MMP-2 levels in comparison to a stress-released lattice. In 2-D cultures, factors that promote fibroblast contractility, including serum or TGF-β, down-regulated MMP-2. Pharmacologically inducing F-actin disassembly or reduced contractility increased MMP-2 expression, while conditions that promote F-actin assembly suppressed MMP-2 expression. In all cases, changes in MMP-2 levels were inversely related to changes in the contractile marker, smooth muscle α-actin. To determine if the mechanisms involved in contractile protein gene expression play a direct role in MMP-2 regulation, we used RNAi-mediated knock-down of the myocardin-like factors, MRTF-A and MRTF-B, which induced the down-regulation of contractile protein genes by fibroblasts under both serum-containing and serum-free conditions. In the presence of serum or TGF-β, MRTF-A/B knock-down resulted in the up-regulation of MMP-2; serum-free conditions prevented this increased expression. Together, these results indicate that, while MMP-2 expression is suppressed by F-actin formation, its up-regulation is not simply a consequence of contractile protein down-regulation.
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. eric-howard@ouhsc.edu
authors.forename: Eric W
authors.initials: EW
authors.lastname: Howard
authors.forename: Beverly J
authors.initials: BJ
authors.lastname: Crider
authors.forename: Dawn L
authors.initials: DL
authors.lastname: Updike
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Bullen
authors.forename: Eileen E
authors.initials: EE
authors.lastname: Parks
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Haaksma
authors.forename: David M
authors.initials: DM
authors.lastname: Sherry
authors.forename: James J
authors.initials: JJ
authors.lastname: Tomasek
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D020778:Matrix Metalloproteinase 2 / Q000235:genetics* / Q000378:metabolism*; D008954:Models, Biological; D058628:Myofibroblasts / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D010641:Phenotype; D055503:Protein Multimerization; D034622:RNA Interference; D051381:Rats; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics; D014945:Wound Healing / Q000235:genetics / Q000502:physiology
chemical_list: D000199:Actins; D007334:Insulin-Like Growth Factor I; D020778:Matrix Metalloproteinase 2; D014157:Transcription Factors; C557977:myocardin-related transcription factor-A, rat; C569168:myocardin-related transcription factor-B, rat; C498862:Acta2 protein, rat; C522363:Mmp2 protein, rat