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Updated: Sep 3, 2026
Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation
Published on: May 31, 2016
Evidence for altered balance between matrix metalloproteinases and their inhibitors in human aortic diseases
J B Knox1, G K Sukhova, A D Whittemore
1Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA.
Background:
Although abdominal aortic aneurysms (AAAs) exhibit increased expression of matrix metalloproteinases (MMPs), the functional balance between MMPs and their tissue inhibitors (TIMPs) remains uncertain. This report compares the proteolytic activity in normal aorta, aorto-occlusive disease (AOD), and AAA by use of a novel in situ zymographic technique.
Methods And Results:
Infrarenal aortic specimens were obtained from 25 patients undergoing surgery for AOD or AAA and were compared with normal aortic tissue (n = 7) obtained from cadavers. Immunohistochemical staining was performed for collagenase (MMP-1), gelatinase A (MMP-2), stromelysin (MMP-3), TIMP-1, and TIMP-2. Net proteolytic activity was determined with in situ zymography whereby aortic sections were incubated on fluorescently labeled substrate. Proteolytic activity was detected under epifluorescent examination. Compared with normal aortic tissue, AOD and AAA tissue demonstrated marked increases in MMP-1 and MMP-3 immunoreactivity, predominantly in the neointima, and modest increases in TIMP-1. MMP-2 was increased in the diseased aortas, and TIMP-2 was abundant in normal, AOD, and AAA samples. Zymography revealed proteolytic activity in AOD and AAA tissues with active digestion of casein and gelatin substrate, particularly on the luminal portion of the specimens. Normal specimens exhibited no lytic activity. Comparison of AOD and AAA specimens revealed no difference in MMP/TIMP immunoreactivity or net proteolytic activity.
Conclusions:
MMP expression is markedly increased in AOD and AAA samples, and an imbalance between MMPs and their inhibitors results in similar proteolytic activity. The eventual formation of aneurysmal or occlusive lesions appears not to result from an ongoing difference in the proteolytic pattern.
Insights
Matrix metalloproteinases (MMPs) and tissue inhibitors (TIMPs) show increased expression in abdominal aortic aneurysms (AAAs) and aorto-occlusive disease (AOD). Proteolytic activity is similar in both conditions, suggesting no difference in the underlying proteolytic pattern.
Area of Science:
- Vascular Biology
- Biochemistry
- Pathology
Background:
- Abdominal aortic aneurysms (AAAs) show increased matrix metalloproteinase (MMP) expression, but the balance with tissue inhibitors (TIMPs) is unclear.
- This study investigates proteolytic activity in normal aorta, AAA, and aorto-occlusive disease (AOD).
Purpose of the Study:
- To compare proteolytic activity in normal aorta, AOD, and AAA using in situ zymography.
- To assess the expression of specific MMPs (MMP-1, MMP-2, MMP-3) and TIMPs (TIMP-1, TIMP-2) in these conditions.
Main Methods:
- Aortic specimens from 25 patients (AOD/AAA) and 7 cadavers (normal) were analyzed.
- Immunohistochemistry was used to detect MMPs and TIMPs.
- In situ zymography assessed net proteolytic activity on casein and gelatin substrates.
Main Results:
- AOD and AAA tissues showed increased MMP-1 and MMP-3 immunoreactivity, predominantly in the neointima.
- MMP-2 was elevated in diseased aortas, while TIMP-2 was abundant in all samples.
- Zymography revealed significant proteolytic activity in AOD and AAA, absent in normal tissue.
- No significant difference in MMP/TIMP levels or proteolytic activity was found between AOD and AAA.
Conclusions:
- MMP expression is significantly increased in AOD and AAA.
- An imbalance between MMPs and TIMPs leads to comparable proteolytic activity in both conditions.
- The formation of aneurysmal or occlusive lesions does not appear to stem from distinct proteolytic patterns.
