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In situ localization and quantification of mRNA for 92-kD type IV collagenase and its inhibitor in aneurysmal,
W D McMillan1, B K Patterson, R R Keen
1Department of Surgery, Northwestern University Medical School, Chicago, Ill, USA.
Abstract:
Ninety-two-kilodalton type IV collagenase (MMP-9) is present in aortic aneurysms and may be important to the pathogenesis of this disease. Alteration in expression of MMP-9 or its inhibitor, the tissue inhibitor of metalloproteinase type 1 (TIMP-1), could increase degradation of extracellular matrix and lead to aneurysm formation. The purpose of this study was (1) to measure tissue levels of MMP-9 and TIMP-1 mRNA in aneurysmal (AAA), atherosclerotic occlusive (AOD), and normal (NL) human infrarenal aorta; (2) to test for their expression by cultured AAA and NL vascular smooth muscle cells (VSMCs); and (3) to locate in situ the cells responsible for mRNA production within AAA, AOD, and NL aortic wall. Total RNA extracted from AAA (n = 8), AOD (n = 8), and NL (n = 7) tissue was subjected to Northern analysis. Signals for MMP-9 and TIMP-1 were normalized to alpha-tubulin. Mean values +/- SEM were compared by ANOVA. NL and AAA VSMCs were cultured, passaged, and grown to confluence before RNA extraction and Northern analysis. In situ hybridization with digoxigenin-labeled RNA probes localized cells responsible for MMP-9 and TIMP-1 mRNA expression within sections of AAA (n = 5), AOD (n = 2), and NL (n = 2) aorta. MMP-9 mRNA levels were significantly greater in AAA (0.855 +/- 0.180) than NL (0.046 +/- 0.23) (P < .02), but differences between AOD (0.406 +/- 0.196) and AAA or AOD and NL were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Ninety-two-kilodalton type IV collagenase (MMP-9) mRNA is significantly elevated in abdominal aortic aneurysms (AAA). This suggests MMP-9 plays a role in AAA pathogenesis by potentially increasing extracellular matrix degradation.
Area of Science:
- Vascular Biology
- Matrix Biology
- Biochemistry
Background:
- Ninety-two-kilodalton type IV collagenase (MMP-9) is implicated in aortic aneurysm pathogenesis.
- Altered expression of MMP-9 or its inhibitor, tissue inhibitor of metalloproteinase type 1 (TIMP-1), may drive extracellular matrix degradation and aneurysm formation.
Purpose of the Study:
- To quantify MMP-9 and TIMP-1 mRNA levels in normal, atherosclerotic, and aneurysmal human aortas.
- To investigate MMP-9 and TIMP-1 expression in cultured vascular smooth muscle cells from normal and aneurysmal tissue.
- To identify the specific cells producing MMP-9 and TIMP-1 mRNA within aortic tissue.
Main Methods:
- Northern analysis of RNA extracted from human infrarenal aorta tissues (aneurysmal, atherosclerotic, normal).
- Culturing and RNA extraction from normal and aneurysmal vascular smooth muscle cells (VSMCs).
- In situ hybridization using digoxigenin-labeled RNA probes to localize mRNA expression in aortic tissue sections.
Main Results:
- MMP-9 mRNA levels were significantly higher in aneurysmal aortic tissue compared to normal aorta (P < .02).
- No significant differences in MMP-9 mRNA were found between atherosclerotic and either normal or aneurysmal aorta.
- TIMP-1 mRNA levels were not detailed in the provided abstract excerpt.
Conclusions:
- Elevated MMP-9 mRNA in abdominal aortic aneurysms suggests a key role in disease development.
- Further research is needed to elucidate the role of TIMP-1 and the specific cellular sources of MMP-9 in aortic aneurysm formation.