Deletion of Krüppel-like factor 4 in endothelial and hematopoietic cells enhances neointimal formation following vascular injury.
BACKGROUND
Krüppel-like factor 4 (Klf4) is involved in a variety of cellular functions by activating or repressing the transcription of multiple genes. Results of previous studies showed that tamoxifen-inducible global deletion of the Klf4 gene in mice accelerated neointimal formation following vascular injury, in part via enhanced proliferation of smooth muscle cells (SMCs). Because Klf4 is also expressed in non-SMCs including endothelial cells (ECs), we determined if Tie2 promoter-dependent deletion of Klf4 in ECs and hematopoietic cells affected injury-induced neointimal formation.


RESULTS
Klf4 conditional knockout (cKO) mice were generated by breeding Tie2-Cre mice and Klf4 floxed mice, and their phenotype was analyzed after carotid ligation injury. Results showed that injury-induced repression of SMC differentiation markers was unaffected by Tie2 promoter-dependent Klf4 deletion. However, of interest, neointimal formation was significantly enhanced in Klf4-cKO mice 21 days following carotid injury. Moreover, Klf4-cKO mice exhibited an augmented proliferation rate, enhanced accumulation of macrophages and T lymphocytes, and elevated expression of cell adhesion molecules including vascular cell adhesion molecule-1 (Vcam1) and E-selectin in injured arteries. Mechanistic analyses in cultured ECs revealed that Klf4 inhibited tumor necrosis factor-α-induced expression of Vcam1 through blocking the binding of nuclear factor-κB to the Vcam1 promoter.


CONCLUSIONS
These results provide evidence that Klf4 in non-SMCs such as ECs regulates neointimal formation by repressing arterial inflammation following vascular injury.
Apheresis and Dialysis Center, School of Medicine, Keio University, Tokyo, 160-8582, Japan.
Tadashi
T
Yoshida
Maho
M
Yamashita
Chihiro
C
Horimai
Matsuhiko
M
Hayashi
D000818:Animals; D001665:Binding Sites; D002339:Carotid Arteries / Q000378:metabolism* / Q000473:pathology; D020212:Carotid Artery Injuries / Q000209:etiology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D019040:E-Selectin / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D020022:Genetic Predisposition to Disease; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000473:pathology; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency* / Q000235:genetics; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D058426:Neointima; D010641:Phenotype; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D042787:Receptor, TIE-2 / Q000235:genetics; D013601:T-Lymphocytes / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism
D019040:E-Selectin; C000715467:KLF4 protein, human; C000715468:Klf4 protein, mouse; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D042787:Receptor, TIE-2; C079086:Tek protein, mouse
cell adhesion molecules; endothelium; krüppel‐like factors; smooth muscle; vascular injury