The Expression And Significance Of MMP-2 And MMP-9 In Human Abdominal Aortic Aneurysm

Abstract Objective To measure the expression of matrix metalloproteinase -2(MMP-2) and matrix metalloproteinase-9(MMP-9) in human abdominal aortic aneurysm (AAA) of various diameters and ruptured abdominal aortic aneurysm (RAAA), detect the source of MMP-2 and MMP-9 and the importance of MMP-2 and MMP-9 in the formation, development and rupture of AAA. Method Immunohistochemistry was applied to detect the expressions of MMP-2 and MMP-9 in the tissue specimens of 30 AAA tissues of various diameters (6 small AAA:＜5.0cm, 12 moderate-diameter AAA: 5.0～7.0cm, 6 large AAA:≥7.0cm and 6 RAAA) and 7 cases of normal human abdominal aorta in the control group. Results MMP-2 mainly expressed in smooth muscle cell(SMC)in the media ofAAA. MMP-9showed reactivity in both SMC and macrophages. The numbers of SMC in large AAA and RAAA were less than those in normal abdominal aorta, small and moderate-diameter AAA (P＜0.01). While the numbers of macrophage in large AAA and RAAA were more than those in normal abdominal aorta, small and moderate-diameter AAA (P＜0.01). The expressions of MMP-2 in AAA and ruptured AAA were significantly higher than those in normal abdominal aorta tissues (P＜0.01). Meanwhile, there were higher expressions of MMP-2 in small and moderate-diameter AAA than in large AAA and RAAA(P＜0.01 ). The expressions of MMP-9 in moderate-diameter, large AAA and RAAA were higher than those in small AAA and normal abdominal aorta tissues (P＜0.01), but there was no significant difference between the expression of MMP-9 in small AAA and normal abdominalaorta tissues (P＞0.05 ). Also, the expression of MMP-9 had no significant difference among moderate- diameter, large AAA and RAAA(P＞0.05). Additionally, there was no significant difference in diameter between RAAA and moderate-diameter or large AAA(P＞0.05). Conclusions In AAA, MMP-2 is mainly produced by SMC in the media; while MMP-9 is chiefly produced by SMC and macrophage. In large AAA and RAAA, MMP-9 mainly comes from SMC and macrophage, while in moderate-diameter AAA, it is mainly produced by SMC. MMP-2 may account for the formation and expansion of AAA while MMP-9 may be responsible for expansion and rupture of AAA. High levels of MMp-9 in moderate-diameter or large AAA may indicate rapid expansion and high rupture rate.