Astrocyte-derived plasminogen activator inhibitor type 1 (PAI-1) promoted the migration of microglia. Primary astrocytes were left untreated or treated with lipopolysaccharide (LPS; 100 ng/ml) and interferon (IFN)-γ (50 U/ml) for 12 hours. Cells were then washed twice with PBS, and cultured in fresh DMEM for an additional 24 hours. The astrocyte-conditioned medium (ACM) was then collected. BV-2 microglial cells were treated for 24 hours with ACM in the presence or absence of PAI-1 neutralizing antibody (PAI-1 Ab; 2 μg/ml), or normal rabbit serum (2 μg/ml) as control. Microglial migration was assessed by wound-healing assay as described in Figure 2. At 0 and 24 hours, phase-contrast images of the wounds at three different locations were taken (upper panel, original magnification, × 150), and then fold increase in migration distance from three independent experiments was measured (lower panel). Results are given as mean ± SD (n = 3). *P < 0.05, **P < 0.01, NS = not significant.