Murine matrix metalloproteinase 13 and human matrix metalloproteinase 1 are involved in remodelling processes after myocardial infarction
Authors: Brauninger H , Kruger S , Becher P M , Neumann J T , Bacmeister L , Voss S , Kupsch S , Zeller T , Lammle S , El-Armouche A , Kirchhof P , Blankenberg S , Westermann D , Lindner D 
Published: May 2024

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): German Centre for Cardiovascular Research (DZHK)

Background
Cardiovascular diseases such as myocardial infarction (MI) remain a leading cause of death in the world. Matrix metalloproteinases (MMPs) are not only essential for the cleavage of collagen, but are also modifying inflammatory cytokines. Thus, MMPs are playing a substantial role in the context of fibrotic as well as inflammatory processes in tissue remodelling after MI.

Purpose
Mmp13 is the highest expressed collagenase in the murine left ventricle (LV). After ligation of the left anterior descending artery (LAD) in mice, Mmp13 is highly upregulated in the LV. Therefore, the aim of this study was to characterize the role of MMP13 in MI. In the human LV, the highest expressed collagenase is MMP1. Single nucleotide polymorphisms (SNPs) in the promotor region of MMP1 can lead to alterations in gene expression level. Therefore, we analysed the genotype of 3 SNPs in about 2000 patients admitted to the emergency department with suspected MI to reveal associations with the development of MI and outcome after MI.

Methods
A MMP13-knockout (KO) mouse model was examined after induction of MI and gene expression analysis, histological staining, in-situ hybridisation and hemodynamic measurements were conducted. Mmp13 expression in different cardiac cell types was investigated at quiescent stage and under ischaemic conditions, to determine the cellular origin of Mmp13 expression. Out of the human cohort, 2 patient groups (non-MI and MI) were restricted. Hazard ratios adjusted to age and male sex were assessed, to evaluate risk for MI and risk for death after MI in dependency of the SNPs.

Results
After activation with ischaemic secretome of cardiomyocytes, the Mmp13 expression of macrophages (6.6-fold; p=0.0286) and fibroblasts (4.9-fold; p=0.0079) was significantly increased. Under stimulation with ischaemic secretome of fibroblasts, Mmp13 expression of macrophages (4.3-fold; p=0.0286) and leukocytes (2.3-fold; p=0.0260) was significantly elevated. Additionally, in situ hybridisation revealed Mmp13 expression in immune cells in the border zone of the infarct region. While the survival of WT mice was about 50%, only very few KO mice died after MI (p=0.0107). Moreover, KO mice showed benefits in cardiac function compared to WT littermates 28 days post-MI. In the human cohort, risk for death was significantly altered between the examined genotypes in 2 of 3 investigated SNPs, indicating a role of MMP1 in the remodelling process after MI.

Conclusion
High levels of Mmp13 after MI originate mainly from activated macrophages and from activated fibroblasts in the infarct border zone. MMP13-deficiency is beneficial for mice after MI, leading to an improved cardiac function 28 days post-MI compared to WT controls. Analysis of SNPs of the human functional homologue of Mmp13 – MMP1 – revealed an association of MMP1 with remodelling processes after MI.