Changes of aquaporin-4 expressions in experimental rats after intracerebral hemorrhage

Objective To study the relationship between the expression of aquaporin-4 (AQP4) and cerebral edema formation during the pathologic course of hemorrhagic cerebral edema. Methods The intracerebral hemorrhage (ICH) was established by infusing collagenase into rat caudate nucleus. In situ hybridization and immunohistochemistry were respectively used to evaluate AQP4 mRNA and protein expression, and electronic microscopy and microangium perfusion were respectively used to observe the changes of the ultrastructural and local capillaries in perihematomal brain edema. Results As compared with the control group, there appeared a significant increase in AQP4 mRNA and protein expression on the edematous tissue at 6 hours in rats following ICH. AQP4 mRNA expression (optical density, A) was increased from 0.29 to 0.57 (P0.01), and AQP4 protein expression (A) increased from 0.06 to 0.15. At the same time, the light swelling in perihematomal brain tissue was found. At 72 h, the expression of AQP4 mRNA and protein reached at its maximum, AQP4 mRNA expression (A) reached at 0.88 and AQP4 protein expression (A) at 0.25 (P0.01). The brain edema became remarkable; neurons and glias together with endothelial cells were all remarkably swelling and capillaries began to proliferate in perihematomal tissue. At day 7, the expression of AQP4 mRNA and protein in intracerebral hemorrhagic group were still higher than that in the control group, and the brain edema was not remarkable. The AQP4 mRNA expression showed a positive relationship with the AQP4 protein expression during the brain edema formation (r s0.82, P s0.01). Conclusions The increased expression of AQP4 was participated in the course of ICH after hemorrhagic cerebral edema, suggesting that AQP4 should play an important role in the pathological course of the hemorrhagic cerebral edema.