Fig. 1

Schematic illustration of the study design and quantification of the microvasculature in randomly selected areas of preterm fetal sheep cerebral cortex and white matter from saline control and LPS-treated subjects. a After recovery from surgery at 103–104 days of gestation, the preterm fetal sheep were given either normal saline infusions/boluses (saline controls, n = 8) or LPS infusion/boluses (n = 7). LPS was infused at 100 ng/kg (50 ng/mL at 83 μL/h) for the first 24 h followed by 250 ng/kg/24 h (50 ng/mL at 207.5 μL/h) for the next 96 h. Boluses were administered as 1 μg LPS at 48, 72, and 96 h from the start of infusion. Normal saline controls received equivalent volumes of saline for both infusions and boluses. Ten days after the start of the infusions at 113–114 days of gestation, the fetal brains were collected for further immunohistochemical analysis. b Representative images of collagen type IV staining (green) in the cerebral cortex and white matter of saline control and LPS-exposed animals. × 10 (top row) and × 20 (bottom row) magnifications are shown, scale bar = 100 μm. White arrows indicate collagen IV-positive microvessels. DAPI (blue) is utilized as a counterstain. c Graphs representing the microvessel density expressed as the percent area of the fields (total area) segmented on anti-collagen type IV-stained sections in the cerebral cortex and white matter of the saline and LPS-exposed fetal sheep. An average of 15–20 fields on two slides per animal and n = 8 in the saline-exposed group and n = 7 in the LPS-exposed group were analyzed. Statistical analysis by Kruskal-Wallis test followed by Dunn’s post hoc test, *P < 0.05; **P < 0.01. d A schematically represented coronal cross-section of the sheep brain. The Roman numeral numbered boxes indicate the areas from which the images were taken in b and quantified in c