title: Matrix stiffness regulates endothelial cell proliferation through septin 9.
abstract: Endothelial proliferation, which is an important process in vascular homeostasis, can be regulated by the extracellular microenvironment. In this study we demonstrated that proliferation of endothelial cells (ECs) was enhanced on hydrogels with high stiffness (HSG, 21.5 kPa) in comparison to those with low stiffness (LSG, 1.72 kPa). ECs on HSG showed markedly prominent stress fibers and a higher RhoA activity than ECs on LSG. Blockade of RhoA attenuated stress fiber formation and proliferation of ECs on HSG, but had little effect on ECs on LSG; enhancement of RhoA had opposite effects. The phosphorylations of Src and Vav2, which are positive RhoA upstream effectors, were higher in ECs on HSG. The inhibition of Src/Vav2 attenuated the HSG-mediated RhoA activation and EC proliferation but exhibited nominal effects on ECs on LSG. Septin 9 (SEPT9), the negative upstream effector for RhoA, was significantly higher in ECs on LSG. The inhibition of SEPT9 increased RhoA activation, Src/Vav2 phosphorylations, and EC proliferation on LSG, but showed minor effects on ECs on HSG. We further demonstrated that the inactivation of integrin α(v)β(3) caused an increase of SEPT9 expression in ECs on HSG to attenuate Src/Vav2 phosphorylations and inhibit RhoA-dependent EC proliferation. These results demonstrate that the SEPT9/Src/Vav2/RhoA pathway constitutes an important molecular mechanism for the mechanical regulation of EC proliferation.
authors.affiliation: Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Yeh
authors.forename: Sung Sik
authors.initials: SS
authors.lastname: Hur
authors.forename: Joann
authors.initials: J
authors.lastname: Chang
authors.forename: Kuei-Chun
authors.initials: KC
authors.lastname: Wang
authors.forename: Jeng-Jiann
authors.initials: JJ
authors.lastname: Chiu
authors.forename: Yi-Shuan
authors.initials: YS
authors.lastname: Li
authors.forename: Shu
authors.initials: S
authors.lastname: Chien
mesh_terms: D059447:Cell Cycle Checkpoints; D049109:Cell Proliferation; D003599:Cytoskeleton / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D010766:Phosphorylation; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D058112:Septins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013379:Substrate Specificity; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D039302:Integrin alphaVbeta3; D051567:Proto-Oncogene Proteins c-vav; D034741:RNA, Small Interfering; C093651:VAV2 protein, human; C066737:RHOA protein, human; C474315:SEPTIN9 protein, human; D058112:Septins; D020742:rhoA GTP-Binding Protein