SPARC expression by cerebral microvascular endothelial cells in vitro and its influence on blood-brain barrier properties.

Abstract

BACKGROUND:

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.

METHODS:

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.

RESULTS:

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.

CONCLUSIONS:

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: Samir Alkabie, Jayasree Basivireddy, Lixin Zhou, Jane Roskams, Peter Rieckmann, Jacqueline A Quandt
• Journal: Journal of neuroinflammation (J Neuroinflammation) Vol. 13 Issue 1 Pg. 225 (08 31 2016) ISSN: 1742-2094 [Electronic] England
• PMID: 27581191 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Osteonectin
• SPARC protein, human

Topics

• Blood-Brain Barrier (drug effects, metabolism)
• Cell Proliferation (drug effects, physiology)
• Cerebrovascular Circulation (drug effects, physiology)
• Endothelial Cells (drug effects, metabolism)
• Gene Expression
• Humans
• Microvessels (drug effects, metabolism)
• Osteonectin (biosynthesis, genetics, pharmacology)