Study Of The Role And Pathogenesis Of Angiopoietins And Shear Stress In The Development And Rupture Of The Intracranial Aneurysms

Objectives: (1) Study the pathology and investigate the expression ofangiopoietin-1 and angiopoietin-2 of the heman intracranial aneuyrsmal tissueso as to elucidate the role and significance of the angiopoieitins in thepathogenesis of the human saccular intracranial aneurysms ; (2) establish thein vitro EA. Hy926 cell model exposure to high shear stress; (3) investigatethe effect of high shear stress on the expression of angiopoientin-2 in theendothelial cells, and analyse the significance and of shear stress in thepathogenesis of human intracranial aneyrsms.Methods: (1) The histopathological morphological alterations ofhuman intracranial aneurismal tissue were observed with conventional lightmicroscope. The expression of ang-1 and ang-2 were investigated viaimmunohistochemistrial method. (2) The transcription of ang-2 in theEA.hy926 cells , which were exposed to high shear stress (36.14dyne/cm~2)0.5h, 1h, 2h, 4h separately, was detected with real-time RT-PCR quantitativemethod. (3) The transcription of ang-2 in the EA.hy926 cells exposed to different shear stress level (15.28 dyne/cm~2, 25.89 dyne/cm~2, 36.14dyne/cm~2)was detected with real-time RT-PCR quantitative method.Results: (1) Study with optic microscope showed that the thickness ofthe wall of the human intracranial aneurysm became uneven: some parts wereextremely thin and only layers of non-cellular structure remained, whilesome parts presented with hyperplasia of the subendothelial layer. Thrombosisand fibrosis could be seen in some samples. The inner elastic layer vanishedcompletely in 34 samples, and degenerated in the other 3 samples. Layer ofsmooth muscle became thinner or even disappear and the number of muscularcells decreased remarkably. Hyalinization could be observed in many samples.Infiltration of inflammatory cells presented in 78.4% samples. (2) Ang-2 IODvalue of human intracranial aneurysm slices was 15685.32±8175.58, whichwas lower than the IOD value of STA slices (p＜0.05 ). (3) Ang-2 IOD valueof human intracranial aneurysm slices was 7187.12±4666.55, while Ang-2expression couldn't be detected in STA samples. The difference between twogroups had statistical significance. (4) The Ang-2 expression in the EA.hy926cells exposed to high shear stress (36.14dyne/cm~2) 0.5h and 1h was a littlelower than the control group. And the expression of Ang-2 was up-regulatedprogressively (2h, 4h) by the high shear stress (p＜0.05). (5) When theexposing time course was equal (4h), the expression level of Ang-2 wasrelated to the level of the shear stress. The expression of Ang-2 was mostactive in 36.14dyne/cm~2 group, while least in 15.28dyne/cm~2group.Conclusions: (1) The histopathological morphological alterations ofhuman intracranial aneurismal tissue were very complicated, and thesignificance of many pathological representation was unclear. Besides, there were no grade or scale systems to describe the pathological representations.Further histopathological research was need urgently. (2) We investigated theexpression of Ang-1 in the human intracranial aneurysm tissue, and theexperiment revealed the expression of Ang-1 in the human I.A. was lower thanthe normal STA. No related research were reported before. (3)Our experimentrevealed the expression of Ang-2 was detected in the human I.A. tissue, whilenot in the normal STA sample. No similar research were reported by now. (4)Decreasing of the expression of Ang-1 and increasing of the expression ofAng-2 play a role synergistically in the pathogenesis of I.A. via regulating thecell apoptosis, inflammation and activity of a series of proteins. (5) EA. Hy926cells posses the morphological and functional characters of endothelial cells,and can be cultured easily in vitro. Allowing for the their stable character, EA.Hy926 cells is fit for establishment of the in vitro model exposing to highshear stress. (6) Shear stress with different magnitude (15.28dyne/cm~2, 25.89dyne/cm~2, 36.14 dyne/cm~2) can induce the expression of Ang-2 in endothelialcells. (7) The expression of Ang-2 in endothelial cells can be regulated by highshear stress via time- and magnitude-dependent pattern. (8) Combining twoparts of the present experiment, we proposed that continued high shear stressin the local cerebral artery could induce the form, development and rupture ofthe human intracranial aneurysm, via up-regulate the Ang-2 expression in thelocal vascular endothelial cells.