title: Proliferation of human primary vascular smooth muscle cells depends on serum response factor.
abstract: Smooth muscle cells (SMCs) can switch between a differentiated/contractile and an alternative proliferative phenotype. The transcription factor serum response factor (SRF) has been implicated in the regulation of gene expression profiles determining both phenotypes. Whereas strong evidence exists for a role of SRF in SMC differentiation, the contribution of SRF to SMC proliferation is less well defined. For primary human vascular SMCs in particular, existing data are non-conclusive. To study SRF functions in primary human vascular SMCs, we used an siRNA approach. siRNA-mediated SRF suppression affected the expression of established SRF target genes such as smooth muscle alpha-actin (ACTA2) or SM22alpha (TAGLN) and decreased both F-actin formation and cell migration. Furthermore, SRF knockdown caused a cell-cycle arrest in G1 associated with reduced hyperphosphorylated pRB, cyclin A and SKP2 levels, and increased p27(kip1) (CDKN1B) protein levels. SRF-depleted cells expressed senescence-associated beta-galactosidase indicating an irreversible G1 arrest. siRNA-mediated suppression of SKP2 triggered senescence to a similar extent as SRF depletion, indicating that SRF knockdown-induced senescence may be dependent on a decrease in SKP2. Thus, SRF is an essential regulator of primary human vascular SMC proliferation and senescence. Interfering with SRF function may therefore be a promising strategy for the treatment of hyperproliferative SMC disorders such as atherosclerosis and in-stent restenosis.
authors.affiliation: Department of Molecular Biology, Interfaculty Institute for Cell Biology, Eberhard Karls University of Tübingen, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Werth
authors.forename: Gabriele
authors.initials: G
authors.lastname: Grassi
authors.forename: Nina
authors.initials: N
authors.lastname: Konjer
authors.forename: Barbara
authors.initials: B
authors.lastname: Dapas
authors.forename: Rossella
authors.initials: R
authors.lastname: Farra
authors.forename: Carlo
authors.initials: C
authors.lastname: Giansante
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kandolf
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Guarnieri
authors.forename: Alfred
authors.initials: A
authors.lastname: Nordheim
authors.forename: Olaf
authors.initials: O
authors.lastname: Heidenreich
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D055785:Gene Knockdown Techniques; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D026362:Serum Response Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D026362:Serum Response Factor