title: Role of Myoendothelial Gap Junctions in the Regulation of Human Coronary Artery Smooth Muscle Cell Differentiation by Laminar Shear Stress.
abstract: OBJECTIVE
  Smooth muscle cells may dedifferentiate into the synthetic phenotype and promote atherosclerosis. Here, we explored the role of myoendothelial gap junctions in phenotypic switching of human coronary artery smooth muscle cells (HCASMCs) co-cultured with human coronary artery endothelial cells (HCAECs) exposed to shear stress.
  
  
  METHODS
  HCASMCs and HCAECs were seeded on opposite sides of Transwell inserts, and HCAECs were exposed to laminar shear stress of 12 dyn/cm2 or 5 dyn/cm2. The myoendothelial gap junctions were evaluated by using a multi-photon microscope.
  
  
  RESULTS
  In co-culture with HCAECs, HCASMCs exhibited a contractile phenotype, and maintained the expression of differentiation markers MHC and H1-calponin. HCASMCs and HCAECs formed functional intercellular junctions, as evidenced by colocalization of connexin(Cx)40 and Cx43 on cellular projections inside the Transwell membrane and biocytin transfer from HCAECs to HCASMCs. Cx40 siRNA and 18-α-GA attenuated protein expression of MHC and H1-calponin in HCASMCs. Shear stress of 5 dyn/cm2 increased Cx43 and decreased Cx40 expression in HCAECs, and partly inhibited biocytin transfer from HCAECs to HCASMCs, which could be completely blocked by Cx43 siRNA or restored by Cx40 DNA transfected into HCAECs. The exposure of HCAECs to shear stress of 5 dyn/cm2 promoted HCASMC phenotypic switching, manifested by morphological changes, decrease in MHC and H1-calponin expression, and increase in platelet-derived growth factor (PDGF)-BB release, which was partly rescued by Cx43 siRNA or Cx40 DNA or PDGF receptor signaling inhibitor.
  
  
  CONCLUSIONS
  The exposure of HCAECs to shear stress of 5 dyn/cm2 caused the dysfunction of Cx40/Cx43 heterotypic myoendothelial gap junctions, which may be replaced by homotypic Cx43/Cx43 channels, and induced HCASMC transition to the synthetic phenotype associated with the activation of PDGF receptor signaling, which may contribute to shear stress-associated arteriosclerosis.
authors.affiliation: Department of Cardiology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Zongqi
authors.initials: Z
authors.lastname: Zhang
authors.forename: Yizhu
authors.initials: Y
authors.lastname: Chen
authors.forename: Tiantian
authors.initials: T
authors.lastname: Zhang
authors.forename: Lingyu
authors.initials: L
authors.lastname: Guo
authors.forename: Wenlong
authors.initials: W
authors.lastname: Yang
authors.forename: Junfeng
authors.initials: J
authors.lastname: Zhang
authors.forename: Changqian
authors.initials: C
authors.lastname: Wang
mesh_terms: D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D018920:Coculture Techniques; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D003331:Coronary Vessels / Q000166:cytology; D042783:Endothelial Cells / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D017629:Gap Junctions / Q000502:physiology*; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009119:Muscle Contraction / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D034622:RNA Interference; D013314:Stress, Mechanical; D000096985:Calponins
chemical_list: D002135:Calcium-Binding Proteins; D018031:Connexin 43; D008840:Microfilament Proteins; D018995:Myosin Heavy Chains; D000096985:Calponins