title: Conditional deletion of Krüppel-like factor 4 delays downregulation of smooth muscle cell differentiation markers but accelerates neointimal formation following vascular injury.
abstract: Phenotypic switching of smooth muscle cells (SMCs) plays a key role in vascular proliferative diseases. We previously showed that Krüppel-like factor 4 (Klf4) suppressed SMC differentiation markers in cultured SMCs. Here, we derive mice deficient for Klf4 by conditional gene ablation and analyze their vascular phenotype following carotid injury. Klf4 expression was rapidly induced in SMCs of control mice after vascular injury but not in Klf4-deficient mice. Injury-induced repression of SMC differentiation markers was transiently delayed in Klf4-deficient mice. Klf4 mutant mice exhibited enhanced neointimal formation in response to vascular injury caused by increased cellular proliferation in the media but not an altered apoptotic rate. Consistent with these findings, cultured SMCs overexpressing Klf4 showed reduced cellular proliferation, in part, through the induction of the cell cycle inhibitor, p21(WAF1/Cip1) via increased binding of Klf4 and p53 to the p21(WAF1/Cip1) promoter/enhancer. In vivo chromatin immunoprecipitation assays also showed increased Klf4 binding to the promoter/enhancer regions of the p21(WAF1/Cip1) gene and SMC differentiation marker genes following vascular injury. Taken together, we have demonstrated that Klf4 plays a critical role in regulating expression of SMC differentiation markers and proliferation of SMCs in vivo in response to vascular injury.
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, 415 Lane Rd, Charlottesville, VA 22908, USA. ty2c@virginia.edu
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Klaus H
authors.initials: KH
authors.lastname: Kaestner
authors.forename: Gary K
authors.initials: GK
authors.lastname: Owens
mesh_terms: D000818:Animals; D020212:Carotid Artery Injuries / Q000503:physiopathology*; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D003433:Crosses, Genetic; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006965:Hyperplasia; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008026:Ligation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D014158:Transcription, Genetic / Q000502:physiology; D017539:Tunica Intima / Q000473:pathology*
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D011993:Recombinant Fusion Proteins; D013629:Tamoxifen; C016601:afimoxifene