TGF-beta1-induced cardiac myofibroblasts are nonproliferating functional cells carrying DNA damages.
TGF-beta1 induces differentiation and total inhibition of cardiac MyoFb cell division and DNA synthesis. These effects of TGF-beta1 are irreversible. Inhibition of MyoFb proliferation is accompanied with the expression of Smad1, Mad1, p15Ink4B and total inhibition of telomerase activity. Surprisingly, TGF-beta1-activated MyoFbs are growth-arrested not only at G1-phase but also at S-phase of the cell cycle. Staining with TUNEL indicates that these cells carry DNA damages. However, the absolute majority of MyoFbs are non-apoptotic cells as established with two apoptosis-specific methods, flow cytometry and caspase-dependent cleavage of cytokeratin 18. Expression in MyoFbs of proliferative cell nuclear antigen even in the absence of serum confirms that these MyoFbs perform repair of DNA damages. These results suggest that TGF-beta1-activated MyoFbs can be growth-arrested by two checkpoints, the G1/S checkpoint, which prevents cells from entering S-phase and the intra-S checkpoint, which is activated by encountering DNA damage during the S phase or by unrepaired damage that escapes the G1/S checkpoint. Despite carrying of the DNA damages TGF-beta1-activated MyoFbs are highly functional cells producing lysyl oxidase and contracting the collagen matrix.
Petrov
Victor V
VV
Department of Heart Diseases, University of Leuven (KULeuven), Leuven, Belgium. victor.petrov@med.kuleuven.be
van Pelt
Jos F
JF
Vermeesch
Joris R
JR
Van Duppen
Viktor J
VJ
Vekemans
Katrien
K
Fagard
Robert H
RH
Lijnen
Paul J
PJ
D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D003094:Collagen / Q000378:metabolism; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004249:DNA Damage; D053938:DNA Fragmentation / Q000187:drug effects; D004587:Electrophoresis, Agar Gel; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D016193:G1 Phase / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000166:cytology* / Q000201:enzymology; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D051898:Smad1 Protein / Q000378:metabolism; D019098:Telomerase / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000378:metabolism
D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D019394:Ki-67 Antigen; D018809:Proliferating Cell Nuclear Antigen; D051898:Smad1 Protein; D053773:Transforming Growth Factor beta1; D003094:Collagen; D008249:Protein-Lysine 6-Oxidase; D019098:Telomerase; D001616:beta-Galactosidase