Objective To investigate the effect of aquaporin4(AQP4) RNAi on brain edema resulting from brain explosive injury.  Methods Totally 150 Wistar adult rats were randomly divided into explosive injury group

AQP4 RNAi group before explosive injury

AQP4 RNAi after explosive injury

AQP4 RNAi group and sham operation group (n=30 in each group). We reconstructed a short hairpin plasmid vector pGenSil that can specifically suppress AQP4 expression

then injected this plasmid into right lateral ventricle 7 days before explosive injury and 1 h after explosive injury. Detonators (80 mg) were exploded at 5-cm distance after skull about 1 cm in diameter was removed on right temporal bone and parietal bone. Expression of AQP4

water content and pathological changes of injured brain were observed on 4 h

12 h

1 d

2 d

5 d

and 7 d after injury.  Results Area and degree of brain edema in AQP4 RNAi group before explosive injury and AQP4 RNAi after explosive injury were less than those in explosive group. Water content of injuried brain showed no difference among AQP4 RNAi group before explosive injury

AQP4 RNAi after explosive injury and explosive injury group (P0.05). Water content of AQP4 RNAi group was less than that of explosive group at the same time point during 12 h-7 d after injury (P0.01). Water content of injuried brain in AQP4 RNAi group before explosive injury reached its peak on 12 h after injury

that in AQP4 RNAi group after explosive injury on day 1 after injury

and that in explosive injury group on day 2 after injury. The peak value of water content of injuried brain in AQP4 RNAi group was lower than that in explosive injury group

that in AQP4 RNAi group before explosive injury lower than that in AQP4 RNAi after explosive injury.  Conclusion AQP4 RNAi reduces brain edema following brain explosive injury. AQP4 may have no influence on brain edema formation at early stage after brain explosive injury

but it possibly takes part in aggravation of brain edema at later stage.