Plasminogen activator inhibitor-1 regulates myoendothelial junction formation.
BACKGROUND
Plasminogen activator inhibitor-1 (PAI-1) is a biomarker for several vascular disease states; however, its target of action within the vessel wall is undefined.


OBJECTIVE
Determine the ability of PAI-1 to regulate myoendothelial junction (MEJ) formation.


RESULTS
MEJs are found throughout the vasculature linking endothelial cells (ECs) and vascular smooth muscle cells. Using a vascular cell coculture we isolated MEJ fractions and performed two-dimensional differential gel electrophoresis. Mass spectrometry identified PAI-1 as being enriched within MEJ fractions, which we confirmed in vivo. In the vascular cell coculture, recombinant PAI-1 added to the EC monolayer significantly increased MEJs. Conversely, addition of a PAI-1 monoclonal antibody to the EC monolayer reduced the number of MEJs. This was also observed in vivo where mice fed a high fat diet had increased PAI-1 and MEJs and the number of MEJs in coronary arterioles of PAI-1(-/-) mice was significantly reduced when compared to C57Bl/6 mice. The presence of MEJs in PAI-1(-/-) coronary arterioles was restored when their hearts were transplanted into and exposed to the circulation of C57Bl/6 mice. Application of biotin-conjugated PAI-1 to the EC monolayer in vitro confirmed the ability of luminal PAI-1 to translocate to the MEJ. Functionally, phenylephrine-induced heterocellular calcium communication in the vascular cell coculture was temporally enhanced when recombinant PAI-1 was present, and prolonged when PAI-1 was absent.


CONCLUSIONS
Our data implicate circulating PAI-1 as a key regulator of MEJ formation and a potential target for pharmacological intervention in diseases with vascular abnormalities (eg, diabetes mellitus).
Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. bei6n@virginia.edu
Katherine R
KR
Heberlein
Adam C
AC
Straub
Angela K
AK
Best
Mark A
MA
Greyson
Robin C
RC
Looft-Wilson
Poonam R
PR
Sharma
Akshaya
A
Meher
Norbert
N
Leitinger
Brant E
BE
Isakson
D000818:Animals; D000911:Antibodies, Monoclonal; D001160:Arterioles / Q000378:metabolism; D020013:Calcium Signaling; D002450:Cell Communication; D002478:Cells, Cultured; D018920:Coculture Techniques; D003331:Coronary Vessels / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D016027:Heart Transplantation; D007365:Intercellular Junctions / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000648:ultrastructure; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000648:ultrastructure; D017395:Plasminogen Activator Inhibitor 1 / Q000172:deficiency / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D021381:Protein Transport; D040901:Proteomics / Q000379:methods; D011994:Recombinant Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D053719:Tandem Mass Spectrometry; D013997:Time Factors
D000911:Antibodies, Monoclonal; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; C051321:SERPINE1 protein, human