Hypoxic-ischemic
brain injury is a leading cause of neurodevelopmental morbidities in preterm and full-term infants. Blood-brain barrier dysfunction represents an important component of perinatal hypoxic-ischemic
brain injury. The extracellular matrix (ECM) is a vital component of the blood-brain barrier.
Matrix metalloproteinases (
MMPs) and tissue inhibitors of
matrix metalloproteinases (TIMPs) are important ECM components. They contribute to brain development, blood-brain barrier maintenance, and to regenerative and repair processes after hypoxic-ischemic
brain injury. We hypothesized that
ischemia at different durations of reperfusion affects the ECM
protein composition of
MMPs and TIMPs in the cerebral cortex of fetal sheep. Cerebral cortical samples were snap-frozen from
sham control fetuses at 127 days of gestation and from fetuses after exposure to 30-min carotid occlusion and 4-, 24-, and 48-h of reperfusion.
Protein expression of MMP-2, -8, -9, and -13 and
TIMP-1, -2, -3, and -4 was measured by Western immunoblotting along with the gelatinolytic activity of MMP-2 and MMP-9 by zymography. The expression of MMP-8 was increased (Kruskal-Wallis, p = 0.04) in fetuses 48 h after
ischemia. In contrast, changes were not observed in the
protein expression of MMP-2, -9, or -13. The gelatinolytic activity of
pro-MMP-2 was increased (ANOVA, p = 0.02, Tukey HSD, p = 0.05) 24 h after
ischemia.
TIMP-1 and -3 expression levels were also higher (TIMP-1, ANOVA, p = 0.003, Tukey HSD, p = 0.01; TIMP-3, ANOVA, p = 0.006, Tukey HSD, p = 0.01) 24 h after
ischemia compared with both the
sham controls and with fetuses exposed to 4 h of reperfusion. The changes in the expression of
TIMP-1, -2, and -3 correlated with the changes in the MMP-8 and -13
protein expression. We speculate that regulation of MMP-8, MMP-13, and TIMPs contributes to ECM remodeling after is chemic-
reperfusion injury in the fetal brain.