Plasminogen activator inhibitor-1 gene-deficient mice: I. generation by homologous recombination and characterization

Homozygous plasminogen activator inhibitor-1 (PAI-1)-deficient (PAI-1^-/-) mice were generated by homologous recombination in D₃ embryonic stem cells. Deletion of the genomic sequences encompassing the transcription initiation site and the entire coding regions of murine PAI-1 was demonstrated by Southern blot analysis. A 3.0-kb PAI-1-specific mRNA was identified by Northern blot analysis in liver from PAI-1 wild type (PAI-1^+/+) but not from PAI-1^-/- mice. Plasma PAI-1 levels, measured 2-4 h after endotoxin (2.0 mg/kg) injection were 63±2 ng/ml, 30±10 ng/ml, and undetectable (< 2 ng/ ml) in PAI-1^+/+, heterozygous (PAI-1^+/-) and PAI-1^-/- mice, respectively (mean±SEM, n = 4-11). PAI-1-specific immunoreactivity was demonstrable in kidneys of PAI-1^+/+ but not of PAI-1^-/- mice. SDS-gel electrophoresis of plasma incubated with ¹²⁵I-labeled recombinant human tissue-type plasminogen activator revealed an ∼ 115,000-M_r. component with plasma from endotoxin-stimulated (0.5 mg/kg) PAI-1^+/+ but not from PAI-1^-/- mice, which could be precipitated with a polyclonal anti-PAI-1 antiserum. PAI-1^-/- mice were viable, produced similar sizes of litters as PAI-1^+/+ mice, and showed no apparent macroscopic or microscopic histological abnormalities.