title: SPARC expression by cerebral microvascular endothelial cells in vitro and its influence on blood-brain barrier properties.
abstract: SPARC (secreted protein acidic and rich in cysteine) is a nonstructural, cell-matrix modulating protein involved in angiogenesis and endothelial barrier function, yet its potential role in cerebrovascular development, inflammation, and repair in the central nervous system (CNS) remains undetermined.
  
  
  
  This study examines SPARC expression in cultured human cerebral microvascular endothelial cells (hCMEC/D3)-an in vitro model of the blood-brain barrier (BBB)-as they transition between proliferative and barrier phenotypes and encounter pro-inflammatory stimuli. SPARC protein levels were quantified by Western blotting and immunocytochemistry and messenger RNA (mRNA) by RT-PCR.
  
  
  
  Constitutive SPARC expression by proliferating hCMEC/D3s is reduced as cells mature and establish a confluent monolayer. SPARC expression positively correlated with the proliferation marker Ki-67 suggesting a role for SPARC in cerebrovascular development. The pro-inflammatory molecules tumor necrosis factor-α (TNF-α) and endotoxin lipopolysaccharide (LPS) increased SPARC expression in cerebral endothelia. Interferon gamma (IFN-γ) abrogated SPARC induction observed with TNF-α alone. Barrier function assays show recombinant human (rh)-SPARC increased paracellular permeability and decreased transendothelial electrical resistance (TEER). This was paralleled by reduced zonula occludens-1 (ZO-1) and occludin expression in hCMEC/D3s exposed to rh-SPARC (1-10 μg/ml) compared with cells in media containing a physiological dose of SPARC.
  
  
  
  Together, these findings define a role for SPARC in influencing cerebral microvascular properties and function during development and inflammation at the BBB such that it may mediate processes of CNS inflammation and repair.
authors: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors: Samir
authors: S
authors: Alkabie
authors: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors: Jayasree
authors: J
authors: Basivireddy
authors: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.
authors: Lixin
authors: L
authors: Zhou
authors: Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
authors: Jane
authors: J
authors: Roskams
authors: Department of Medicine, Division of Neurology, University of British Columbia, Vancouver, BC, Canada.|Sozialstiftung Bamberg, Klinikum am Bruderwald, Neurologische Klinik, Buger Str. 80, Bamberg, 96049, Germany.
authors: Peter
authors: P
authors: Rieckmann
authors: Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada. jquandt@pathology.ubc.ca.
authors: Jacqueline A
authors: JA
authors: Quandt
mesh_terms: D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D055806:Microvessels / Q000187:drug effects / Q000378:metabolism*; D015676:Osteonectin / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology
chemical_list: D015676:Osteonectin; C577241:SPARC protein, human