OBJECTIVESTo detect the expression of Cathepsin B (CatB) in the intracranial aneurysm wall and its effect to the apoptosis of vascular smooth muscle cells, aimed at clarifying the pathological formation mechanism of intracranial aneurysm.

METHODSFrom November 2006 to February 2009, 20 intracranial aneurysm samples were collected as the experimental group, and 6 cases of normal pallium artery samples were collected as the control group. Immunohistochemical technique was used to evaluate the expressions of CatB, alpha-smooth muscle actin (alpha-SMA) and Caspase-3. The expression of CatB mRNA was evaluated by real-time PCR. The ultrastructure of intracranial aneurysms were observed by using the transmission electronic microscope.

RESULTSCompared with the normal pallium artery specimens, the expression of CatB and Caspase-3 both significantly increased in the intracranial aneurysm walls where alpha-SMA decreased (P < 0.05). The mean expression of CatB mRNA in intracranial aneurysm samples was about 3.8-folds than that in control group (P < 0.01). There were excessive apoptotic vascular smooth muscle cells (VSMCs) in the tunica median, and typical apoptotic body were observed in some aneurysm walls.

CONCLUSIONCathepsin B may be involved in the formation and the progression of intracranial aneurysm.