Objective        To investigate the significance of matrix metalloproteinase-9 (MMP-9) expression in astrocytes after oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro.       Methods        Astrocytes were divided into control group

OGD/R group and GM6001 group. Astrocytes in OGD/R group were treated with OGD for 3

5

and 7 h

respectively

and then reoxygenated for 24 h. In GM6001 group

astroctyes were treated with the inhibitor of matrix metalloproteinase (GM6001

10 μmol/ml) during 5 hours’ OGD/R. The expression of MMP-9 at mRNA and protein levels in the astrocytes were detected after 24 hours’ reoxygenation by RT-PCR and ELISA. The morphological alterations of cells in each group were observed by light microscopy. The cell injury was inspected by LDH activity (LDH %) and Cell Counting Kit-8 (CCK-8).       Results      Compared with normal group

as the OGD time prolonged

the expression of MMP-9 at mRNA and protein levels were increased gradually (P0.05) after OGD/R

which were further increase with time elapse. OGD resulted in in significant swelling astrocytes and obviously injured with time prolonged

and some cells seemed to be coagulation necrosis

the LDH % was increased (P0.01) and the survival rate was decreased severely (P0.05

P0.01). Protein level of MMP-9 in the supernatant was positively correlated with LDH % (r=0.693

P0.05). Compared with OGD/R group

cell injury following 5 hours’ OGD/R was remarkably decreased

as survival rate was raised significantly.       Conclusion        Over-expression of MMP-9 might be a important factor in OGD/R-induced cell injury.