Fig. 1.

Mild hypoxic stress triggers vascular leak in spinal cord blood vessels associated with microglial clustering. Frozen sections of lumbar spinal cord taken from mice exposed to normoxia or 7-d hypoxia (8% O₂) were stained for the following markers: the endothelial marker CD31 (Alexa Fluor 488) and fibrinogen (Cy-3) (A); fibrinogen (Cy-3) and Mac-1 (Alexa Fluor 488) (C); CD31 (Alexa Fluor 488), fibrinogen (abbreviated to Fbg in E) Cy-5 (blue) and Mac-1 (Cy-3) (D and E); and Mac-1 (Alexa Fluor 488) (F). (B) Quantification of the number of leaky (fibrinogen-positive) vessels/FOV. (G) Quantification of the morphological categorization of microglia under different conditions. Results are expressed as the mean ± SEM (n = 6 mice per group). *P < 0.05, **P < 0.01 vs. normoxic conditions. One-way ANOVA followed by Tukey’s multiple comparison test. Note that CMH induced transient vascular leak in spinal cord blood vessels that was associated with wrapping of Mac-1–positive microglial processes around the damaged vessel (high power images in E) and with morphological switch from ramified to activated morphology (F). (Scale bars, 50 μm; except for E, 25 μm.)