Chronic mild hypoxia (CMH) upregulates endothelial α5 integrin expression in spinal cord blood vessels. Dual-IF was performed on frozen sections of spinal cord white matter (A) or gray matter (C) taken from mice exposed to normoxia or 2, 4 or 7 days hypoxia using antibodies specific for CD31 (AlexaFluor-488) and α5 integrin (Cy-3). Scale bar = 100 µm. High power (HP) images, scale bar = 25 µm. B and D. Quantification of endothelial α5 integrin signal at different time-points of CMH in white matter (B) and gray matter (D). Results are expressed as the mean ± SEM (n = 3 mice/group). Note that under normoxic conditions, endothelial expression of α5 integrin is low, but after 4 or 7 days CMH, α5 integrin expression is strongly increased, both in white and gray matter. * p < 0.05, ** p < 0.01 vs. normoxia (0 days hypoxia).