Collagen‐Targeted Peptides for Molecular Imaging of Diffuse Cardiac Fibrosis

Abstract

Background Cardiac fibrosis is the excessive deposition of extracellular matrix in the heart, triggered by a cardiac insult, aging, genetics, or environmental factors. Molecular imaging of the cardiac extracellular matrix with targeted probes could improve diagnosis and treatment of heart disease. However, although this technology has been used to demonstrate focal scarring arising from myocardial infarction, its capacity to demonstrate extracellular matrix expansion and diffuse cardiac fibrosis has not been assessed. Methods and Results Here, we report the use of collagen‐targeted peptides labeled with near‐infrared fluorophores for the detection of diffuse cardiac fibrosis in the β2‐AR (β‐2‐adrenergic receptor) overexpressing mouse model and in ischemic human hearts. Two approaches were evaluated, the first based on a T peptide that binds matrix metalloproteinase‐2‐proteolyzed collagen IV, and the second on the cyclic peptide EP‐3533, which targets collagen I. The systemic and cardiac uptakes of both peptides (intravenously administered) were quantified ex vivo by near‐infrared imaging of whole organs, tissue sections, and heart lysates. The peptide accumulation profiles corresponded to an immunohistochemically‐validated increase in collagen types I and IV in hearts of transgenic mice versus littermate controls. The T peptide could encouragingly demonstrate both the intermediate (7 months old) and severe (11 months old) cardiomyopathic phenotypes. Co‐immunostainings of fluorescent peptides and collagens, as well as reduced collagen binding of a control peptide, confirmed the collagen specificity of the tracers. Qualitative analysis of heart samples from patients with ischemic cardiomyopathy compared with nondiseased donors supported the collagen‐enhancement capabilities of these peptides also in the clinical settings. Conclusions Together, these observations demonstrate the feasibility and translation potential of molecular imaging with collagen‐binding peptides for noninvasive imaging of diffuse cardiac fibrosis.

Assessment of the epi-pericardial fibrotic substrate by collagen-targeted probes

“…Our data exemplify the possibility of fluorescence imaging to visualize atrial fibrosis by means of molecular tracers. In particular, the findings hold promising implication for right ventricular imaging (as we have previously shown 12 ), which is especially challenging given the thin nature of structures in the right heart. Notably, the right ventricle is larger in volume than its left counterpart, but has smaller mass and thinner wall, which impedes CMRI-LGE imaging.…”

“…Here, we describe potential optical materials to detect atrial-pericardial and interstitial fibrosis in the clinic. Importantly, we previously reported based on histological examination and rapid blood clearance sampling in mice that the peptides were not toxic 12 . However, peptides biotoxicity assessment could further benefit from whole blood biochemical analysis, analysing electrolyte levels and liver function after peptide administration.…”

“…The cyclic peptide was previously shown to be effective for collagen I targeting 23 , 42 – 44 and was evaluated for in vitro collagen affinity 23 . For supplemental information on reagents and methods see 12 .…”

“…Our newly developed molecular tracers 12 target and bind to collagens. These tracers were deployed to quantify myocardial interstitial diffuse fibrosis to demonstrate near-infrared (NIR) visualization of atrial fibro-pericardial lesions at the level of active or less organised lesional collagen deposition.…”

A Type I Collagen-Targeted MR Imaging Probe for Staging Fibrosis in Crohn’s Disease

“…Therefore, an accurate imaging technique for fibrosis analysis is desired. Recently, several studies have also shown that the use of ColI-targeted imaging probe in MR imaging can benefit the fibrosis diagnosis in Duchenne muscular dystrophy ( Murphy et al, 2021 ), nonalcoholic steatohepatitis ( Zhou et al, 2020 ), diffuse cardiac fibrosis ( Ezeani et al, 2021 ) and pancreatic cancer ( Polasek et al, 2017 ). In this study, we generated an CD fibrosis rat model to evaluate the strategy of targeting ColI for staging fibrosis in CD and to compare its efficiency with Gd-DTPA, which is a common MR imaging contrast medium.…”