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 αvβ3 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.

Matricellular protein SPARCL1 regulates tumor microenvironment–dependent endothelial cell heterogeneity in colorectal carcinoma

“…For example, antiangiogenic genes included septin 9 (SEPT9) and protein tyrosine phosphatase, nonreceptor type 23 (PTPN23), which inhibit EC proliferation and migration, respectively (28,30). The antitumorigenic genes included ADAMTS9, which blocks tumor growth by inhibition of Akt activation (25); DYRK1A, which inhibits the growth of AML cells (26), and CAMK2N1, which inhibits prostate cancer progression through androgen receptor-dependent signaling (27).…”

Regulation of Endothelial Cell Adherence and Elastic Modulus by Substrate Stiffness

“…On the other hand, dysfunction of such cells may result in vascular disorders or facilitate tumor angiogenesis (Yeh et al 2012). The biophysical environment of endothelial cells has been considered as an important factor in the normal homeostasis of these cells.…”

“…Vascular endothelial cells are supported by their underlying basement membrane which plays major roles in their normal function. Alterations in different characteristics of such extracellular environment including its stiffness have been observed in the case of some vascular diseases (Baluk et al 2003;Liliensiek et al 2009;Stroka & Aranda-Espinoza 2011a;Yeh et al 2012). Such changes in the stiffness of the underlying substrate of endothelial cells can affect their function.…”

“…While numerous studies have confirmed the importance of surface chemistry in cell-substrate interaction for successful performance of implants or tissue engineered constructs, the impact of mechanical parameters of substrate, such as stiffness on cellular functions has only been studied in the past 10 years Yeung et al 2005;Saha et al 2008;Byfield et al 2009;Stroka & Aranda-Espinoza 2011a;Yeh et al 2012;Huang et al 2013;Ataollahi et al 2015).…”

More than a Scaffold: Extracellular Matrix in Vascular Signaling

“…The matricellular protein CCN1 promotes EC migration and aberrant neovascularization in pancreatic cancer [103]. EC survival during hypoxic conditions is mediated by a matrix-associated protein EGFL7 [104], while different collagens, which are excessively deposited within the stroma, may control EC proliferation through regulation of ECM stiffness [105,106]. Finally, tenascin-C, which is highly expressed in tumor-derived endothelium [107], regulates multiple aspects of vascular sprouting by instructing EC migration, proliferation, and VEGF expression [108,109].…”