Imaging the Extracellular Matrix in Prevalent Cardiovascular Diseases

The extracellular matrix (ECM) is a highly complex macromolecular network present in all tissues and organs. The ECM is continuously remodelling under an orchestrated process facilitated by many matrix-degrading and matrix-synthesising enzymes in both health and disease. Disturbance of this balance can be the result of or can lead to various diseases. In cardiovascular diseases (CVDs), changes to the ECM are evident in conditions including: atherosclerosis, myocardial infarction (MI), venous thromboembolism (VTE) and abdominal aortic aneurysm (AAA). ECM proteins and ECM regulating enzymes are differently expressed in various CVDs. Most importantly, the altered deposition, macromolecule arrangement and activity of the ECM makes it an attractive marker of disease onset, pathogenesis and progression. Many medical imaging modalities allow disease assessment by exploiting native image contrast, by using non-targeted or by using protein or cell specific (targeted) imaging probes. However, the ability to directly visualise and quantify changes in specific ECM proteins enhances our understanding of the biological role of these proteins, enables monitoring of disease progression and response to treatment and may improve patient diagnosis and allocation of personalised therapies. This review focuses on the biochemistry of the major extracellular matrix proteins and advancements in the development of ECM-targeted probes for molecular imaging of CVD, particularly for applications of molecular magnetic resonance imaging (MRI) and position emission tomography (PET) imaging.