title: Reversible and irreversible differentiation of cardiac fibroblasts.
abstract: OBJECTIVE
  Differentiation of cardiac fibroblasts (Fbs) into myofibroblasts (MyoFbs) is responsible for connective tissue build-up in myocardial remodelling. We examined MyoFb differentiation and reversibility.
  
  
  RESULTS
  Adult rat cardiac Fbs were cultured on a plastic substratum providing mechanical stress, with conditions to obtain different levels of Fb differentiation. Fb spontaneously differentiated to proliferating MyoFb (p-MyoFb) with stress fibre formation decorated with alpha-smooth muscle actin (α-SMA). Transforming growth factor-β1 (TGF-β1) promoted differentiation into α-SMA-positive MyoFb showing near the absence of proliferation, i.e. non-p-MyoFb. SD-208, a TGF-β-receptor-I (TGF-β-RI) kinase blocker, inhibited p-MyoFb differentiation as shown by stress fibre absence, low α-SMA expression, and high proliferation levels. Fb seeded in collagen matrices induced no contraction, whereas p-MyoFb and non-p-MyoFb induced 2.5- and four-fold contraction. Fb produced little collagen but high levels of interleukin-10. Non-p-MyoFb had high collagen production and high monocyte chemoattractant protein-1 and tissue inhibitor of metalloproteinases-1 levels. Transcriptome analysis indicated differential activation of gene networks related to differentiation of MyoFb (e.g. paxilin and PAK) and reduced proliferation of non-p-MyoFb (e.g. cyclins and cell cycle regulation). Dedifferentiation of p-MyoFb with stress fibre de-polymerization, but not of non-p-MyoFb, was induced by SD-208 despite maintained stress. Stress fibre de-polymerization could also be induced by mechanical strain release in p-MyoFb and non-p-MyoFb (2-day cultures in unrestrained 3-D collagen matrices). Only p-MyoFb showed true dedifferentiation after long-term 3-D cultures.
  
  
  CONCLUSIONS
  Fb, p-MyoFb, and non-p-MyoFb have a distinct gene expression, ultrastructural, and functional profile. Both reduction in mechanical strain and TGF-β-RI kinase inhibition can reverse p-MyoFb differentiation but not non-p-MyoFb.
authors.affiliation: Department of Cardiovascular Diseases, Division of Experimental Cardiology, University of Leuven, KU Leuven, Campus Gasthuisberg O/N1 Box 704, Herestraat 49, Leuven B-3000, Belgium.
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Driesen
authors.forename: Chandan K
authors.initials: CK
authors.lastname: Nagaraju
authors.forename: Joëlle
authors.initials: J
authors.lastname: Abi-Char
authors.forename: Tamara
authors.initials: T
authors.lastname: Coenen
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lijnen
authors.forename: Robert H
authors.initials: RH
authors.lastname: Fagard
authors.forename: Karin R
authors.initials: KR
authors.lastname: Sipido
authors.forename: Victor V
authors.initials: VV
authors.lastname: Petrov
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D008297:Male; D058628:Myofibroblasts / Q000166:cytology / Q000378:metabolism*; D011621:Pteridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D013312:Stress, Physiological; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: D011621:Pteridines; D018125:Receptors, Transforming Growth Factor beta; C511004:SD-208; D053773:Transforming Growth Factor beta1; D003094:Collagen
keywords: Cardiac fibroblast; Dedifferentiation; Myofibroblast