title: Reduced serum content and increased matrix stiffness promote the cardiac myofibroblast transition in 3D collagen matrices.
abstract: BACKGROUND
  The fibroblast-myofibroblast transition is an important event in the development of cardiac fibrosis and scar formation initiated after myocardial ischemia. The goals of the present study were to better understand the contribution of environmental factors to this transition and determine whether myofibroblasts provide equally important feedback to the surrounding environment.
  
  
  METHODS
  The influence of matrix stiffness and serum concentration on the myofibroblast transition was assessed by measuring message levels of a panel of cardiac fibroblast phenotype markers using quantitative reverse transcriptase polymerase chain reaction. Cell-mediated gel compaction measured the influence of environmental factors on cardiac fibroblast contractility. Immunohistochemistry characterized alpha-smooth muscle actin expression and cell morphology, while static and dynamic compression testing evaluated the effect of the cell response on the mechanical properties of the cell-seeded collagen hydrogels.
  
  
  RESULTS
  Both reduced serum content and increased matrix stiffness contributed to the myofibroblast transition, as indicated by contractile compaction of the gels, increased message levels of col3α1 and alpha-smooth muscle actin, and a less stellate morphology. However, the effects of serum and matrix stiffness were not additive. Mechanical testing indicated that reduced serum content increased the initial elastic modulus of cell-seeded gels and that gels lost their viscous character with time.
  
  
  CONCLUSIONS
  The results suggest that reduced serum and increased matrix stiffness promote the myofibroblast phenotype in the myocardium. This transition both enhances and is promoted by matrix stiffness, indicating the presence of positive feedback that may contribute to the pathogenesis of cardiac fibrosis.
authors.affiliation: Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Galie
authors.forename: Margaret V
authors.initials: MV
authors.lastname: Westfall
authors.forename: Jan P
authors.initials: JP
authors.lastname: Stegemann
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D018929:Cell Culture Techniques; D048430:Cell Shape; D054338:Cell Transdifferentiation / Q000235:genetics; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000378:metabolism; D055119:Elastic Modulus; D025461:Feedback, Physiological; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D005355:Fibrosis; D005786:Gene Expression Regulation; D005819:Genetic Markers; D020100:Hydrogels; D007150:Immunohistochemistry; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D058628:Myofibroblasts / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044967:Serum / Q000378:metabolism*; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000235:genetics; D014783:Viscosity
chemical_list: D000199:Actins; D003094:Collagen; D003470:Culture Media; D005819:Genetic Markers; D020100:Hydrogels; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; C498862:Acta2 protein, rat