In situ localization and quantification of mRNA for 92-kD type IV collagenase and its inhibitor in aneurysmal, occlusive, and normal aorta

W. D. McMillan, B. K. Patterson, R. R. Keen, V. P. Shively, M. Cipollone, W. H. Pearce

Research output: Contribution to journalArticle

134 Scopus citations

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 α-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. Differences in TIMP-1 mRNA levels between tissue types were not significant (AAA, 1.17±0.123; AOD, 1.79±0.351; NL, 0.652±0.378). Cultured AAA and NL aortic VSMCs constitutively expressed mRNA for TIMP-1 but not MMP-9. In situ hybridization of AAA and AOD tissue localized MMP-9 mRNA to adventitial macrophages in areas of neovascularization and TIMP-1 mRNA to adventitial VSMCs. MMP-9 mRNA levels are significantly greater in aneurysmal than normal aorta. Cultured VSMCs constitutively express TIMP-1 but not MMP-9. In the diseased aortic wall, MMP-9 mRNA is found in adventitial macrophages and TIMP-1 mRNA in adventitial VSMCs. Localization of MMP-9 mRNA expression to discrete areas surrounding vasa vasorum suggests that the enzyme is responsible for localized matrix alterations associated with neovascularization.

Original languageEnglish (US)
Pages (from-to)1139-1144
Number of pages6
JournalArteriosclerosis, thrombosis, and vascular biology
Volume15
Issue number8
DOIs
StatePublished - Aug 1995

Keywords

  • TIMP
  • aortic aneurysm
  • metalloproteinase
  • vasorum

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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