Expressions of matrix metalloproteinase-9 (MMP-9) and occludin in brain tissue of hypoxic-ischemic neonatal rats

Objective To investigate the effect of MMP-9 mRNA and occludin mRNA expressions after hypoxic-ischemic brain damage( HIBD). Methods Neonatal 7-day-old Sprague Dawley rats were ran-domly divided into control group,HIBD 3 h,6 h,24 h,48 h and 72 h groups (n =6 per group). The ligated cerebral hemisphere was observed for the morphological changes. The expression of MMP-9 mRNA and oc-cludin mRNA were measured by Real-time Q-PCR. Results (1)The ligated cerebral hemisphere of neonatal rats showed obvious edema from 24 h to 48 h after hypoxia-ischemia. (2) As compared to HIBD groups,the expression of MMP-9 mRNA was lower in control group (0. 7933 ± 0.0859) (P＜ 0.05). In the group of HIBD,it began to increase at 3h(l.1533 ±0.1291) ,and peaked at 24 h(3.4883 ±0.1759) .maintained the high level at 72 h(1.625 0±0. 1157). (3) The expression of occludin mRNA was higher in the control group(2.1780 ±0.0773) (P＜0.05), while in the group of HIBD, it began to decrease at 3 h(1.718 6 ± 0.1168) ,was lowest at 24 h(0.9066 ±0.0602) ,and maintained the low level at 72 h( 1.5966 ±0.0799). (4) The expression of MMP-9 mRNA negatively correlated with the expression of occludin mRNA (r = -0.815, P ＜0.05). Conclusion The increased expression of MMP-9 mRNA and the decreased expression of occlu-din mRNA after HIBD may play a role in the pathogenesis of HIBD in neonatal rats. Key words: Hypoxic-ischemia, brain;  Matrix metalloproteinase-9;  Tight junction protein;  Occludin;  Neonatal rats