Plasminogen activator inhibitor-1 deposition in the extracellular matrix of cultured human mesangial cells.
Human mesangial cells secrete tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1), the latter being secreted in large excess in vitro. We demonstrate that PAI-1 is a major component of the extracellular matrix of cultured human mesangial cells, where its deposition is dependent on cell density. By immunogold silver staining, epipolarization microscopy and dispersive X-ray spectrometry, we have shown that matrix-associated PAI-1 is synthesized by spreading human mesangial cells, as indicated by the time-dependent accumulation of PAI-1 and the inhibitory effect of cycloheximide. Furthermore, by in situ hybridization, PAI-1 mRNA was detected in cultured mesangial cells. t-PA is present inside the cells, or at the cell surface, but is never associated with the extracellular matrix. Exogenous t-PA can remove matrix-associated PAI-1 without affecting cell adhesion. A similar effect was obtained by addition of urokinase-type plasminogen activator (u-PA) but not with fibrinolysis unrelated enzymes. In conclusion, PAI-1 is synthesized by human cultured mesangial cells and is deposited in the extracellular matrix by nonconfluent cells, whereas less PAI-1 is seen between confluent cells. This can explain the absence of detectable PAI-1 in normal human kidney biopsies. t-PA released by mesangial cells can bind and detach matrix PAI-1.
Hagège
J
J
INSERM U64, Hôpital Tenon, Paris, France.
Peraldi
M N
MN
Rondeau
E
E
Adida
C
C
Delarue
F
F
Medcalf
R
R
Schleuning
W D
WD
Sraer
J D
JD
D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D010450:Endopeptidases / Q000494:pharmacology; D005109:Extracellular Matrix / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000378:metabolism; D005920:Glomerular Mesangium / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008855:Microscopy, Electron, Scanning; D009693:Nucleic Acid Hybridization; D015849:Plasminogen Inactivators / Q000032:analysis* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology
D016326:Extracellular Matrix Proteins; D015849:Plasminogen Inactivators; D012333:RNA, Messenger; D003513:Cycloheximide; D010450:Endopeptidases; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator