The Differential Expression of Matrix Metalloproteinases and Tissue Inhibitors of Matrix Metalloproteinases in a Porcine Model of Coarctation-induced Abdominal Aortic Aneurysm

  • 陳 玲麗

Student thesis: Master's Thesis

Abstract

Abdominal Aortic Aneurysm (AAA) is a life-threatening cardiovascular disease that affects 4% to 8% of the population over 65 years old AAA usually remains asymptomatic but causes a mortality rate over 80% when rupture occurs Up to now surgery is the sole effective treatment for AAA and new therapeutics are urgently needed AAA tissues obtained at surgery are characterized by chronic inflammation destructive remodeling of the extracellular matrix (ECM) and depletion of vascular smooth muscle cells (VSMCs) However mechanisms underlying the initial AAA formation and further progression remain poorly understood To address this problem our laboratory established a coarctation-induced AAA model in Taiwanese Lanyu mini pigs in which coarctation of an infrarenal abdominal aorta (AA) segment for 12 weeks induces AAA formation in the distal segment Matrix metalloproteinases (MMPs) degrade ECM proteins particularly elastin and collagen which maintain the elasticity and strength of the aorta MMP activities are in turn regulated by endogenous tissue inhibitors of matrix metalloproteinases (TIMPs) Therefore this study is aimed to examine the temporal and spatial expression of MMPs and TIMPs during coarctation-induced AAA formation The expression of MMPs and TIMPs was examined at 4 weeks (4w) 8 weeks (8w) and 12 weeks (12w) post-coarctation in the AA segments proximal and distal to coarctation using suprarenal AA segment as a reference Sham group which received similar surgical procedure without coarctation was used as the control Via real-time polymerase chain reaction (PCR) analysis the mRNA levels of MMP3 MMP7 MMP9 MMP13 and MMP19 were elevated in the distal AA segment at 4w compared to either one or both of the other two segments In addition MMP19 mRNA was elevated in the experimental group at 4w compared with sham group In contrast MMP15 mRNA exhibited an increase in the suprarenal AA segment compared with the proximal AA segment and sham group at 4w post-coarctation Protein expression of MMP2 MMP9 and MMP13 was further investigated with immunoblotting No apparent change was detected for MMP2 and MMP13 which are constitutively expressed in the aorta An apparent increase was detected for MMP9 expression and gelatinolytic activity in the distal AA segment over the investigation period though the increase did not reach significant level as a result of large variation among experimental animals In contrast neither MMP9 protein expression nor gelatinolytic activity was detected in the suprarenal AA segment Among four TIMPs mRNA expression of TIMP2 and TIMP3 were upregulated in the suprarenal AA at 4w post-coarctation compared with the other two segments and TIMP3 mRNA remained high at 8w post-coarctation In contrast no change in TIMP3 protein level was detected with immunoblotting after coarctation Double immunofluorescence staining was performed to detect the cell types that express MMP9 and/or TIMP3 The results showed that MMP9 was colocalized with infiltrated macrophages in the adventitia at 4w 8w and 12w post-coarctation In contrast no MMP9 was detected in VSMCs of the aortic wall Immunoreactivity of TIMP3 was detected in the outer media and the adventitia of all AA segments of the sham group and was prominent in the vasa vasorum Co-localization of MMP9 and TIMP3 was observed in some vasa vasorum of the distal AA segment however the co-localization rate was low and may not be sufficient to protect the distal AA from aneurysm progression Overall these results clearly showed that MMPs and TIMPs are differentially expressed during coarctation-induced AAA formation and these changes may contribute to AAA development and/or progression
Date of Award2014 Oct 14
Original languageEnglish
SupervisorMeei-Jyh Jiang (Supervisor)

Cite this

'