title: Simulated Microgravity Promotes Angiogenesis through RhoA-Dependent Rearrangement of the Actin Cytoskeleton.
abstract: OBJECTIVE
  Microgravity leads to hydrodynamic alterations in the cardiovascular system and is associated with increased angiogenesis, an important aspect of endothelial cell behavior to initiate new vessel growth. Given the critical role of Rho GTPase-dependent cytoskeleton rearrangement in cell migration, small GTPase RhoA might play a potential role in microgravity-induced angiogenesis.
  
  
  METHODS
  We examined the organization of actin filaments by FITC-conjugated phalloidin staining, as well as the expression and activity of RhoA by quantitative PCR and Western blot, in human umbilical vein endothelial cells (HUVECs) under normal gravity and simulated microgravity. Effect of simulated microgravity on the wound closure and tube formation in HUVECs, and their dependence on RhoA, were also analyzed by cell migration and tube formation assays.
  
  
  RESULTS
  We show that in HUVECs actin filaments are disorganized and RhoA activity is reduced by simulated microgravity. Blocking RhoA activity either by C3 transferase Rho inhibitor or siRNA knockdown mimicked the effect of simulated microgravity on inducing actin filament disassembly, followed by enhanced wound closure and tube formation in HUVECs, which closely resembled effects seen on microgravity-treated cells. In contrast, overexpressing RhoA in microgravity-treated HUVECs restored the actin filaments, and decreased wound closure and tube formation abilities.
  
  
  CONCLUSIONS
  These results suggest that RhoA inactivation is involved in the actin rearrangement-associated angiogenic responses in HUVECs during simulated microgravity.
authors.forename: Fei
authors.initials: F
authors.lastname: Shi
authors.forename: Yong-Chun
authors.initials: YC
authors.lastname: Wang
authors.forename: Ze-Bing
authors.initials: ZB
authors.lastname: Hu
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Xiao-Tao
authors.initials: XT
authors.lastname: Li
authors.forename: Chang-Bin
authors.initials: CB
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Xie
authors.forename: Cheng-Fei
authors.initials: CF
authors.lastname: Li
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Jiang-Dong
authors.initials: JD
authors.lastname: Zhao
authors.forename: Xin-Sheng
authors.initials: XS
authors.lastname: Cao
authors.forename: Xi-Qing
authors.initials: XQ
authors.lastname: Sun
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology*; D000199:Actins / Q000378:metabolism*; D002465:Cell Movement; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008856:Microscopy, Fluorescence; D018919:Neovascularization, Physiologic / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018474:Weightlessness Simulation; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D034741:RNA, Small Interfering; D020742:rhoA GTP-Binding Protein
keywords: Angiogenesis; Cytoskeleton dynamics; Migration; Rho GTPase; Simulated microgravity