Abstract Body (Do not enter title and authors here): Background: Persistent scarring after myocardial infarction (MI) is a major driver of heart failure in mammals. However, unlike mammals, zebrafish exhibit a remarkable ability to resorb scar, which consists predominantly of collagen in both species.
Aims: We aimed here to develop a toolbox of techniques to characterize the nature of collagen in infarcted mammalian and zebrafish hearts. Specifically, we aimed to characterize the early and late cross-links that form in collagen and determine whether differences in these cross-links exist in zebrafish and mammals.
Methods To characterize the initial oxidation and cross-linking of collagen we developed a novel fluorescent probe (TMR-O) that binds to lysine aldehydes on collagen and inform on the degree of collagen cross-linking. Additionally, we used high performance liquid chromatography (HPLC) to quantify degradation-resistant mature collagen cross-links, such as pyridinoline (Pyd), and its precursor, hydroxylysine.
Results: TMR-O imaging revealed similar overall CCL levels in both zebrafish and mouse infarcts. However, the irreversible cross-link pyridinoline (Pyd) was abundant in mouse infarcts but completely absent in zebrafish (p<0.0001). High Pyd levels in mice were accompanied by a dynamic increase in lysine hydoxylation (>200%), which was not observed in zebrafish (<10%).
Conclusions: While collagen in mammalian and zebrafish infarcts may appear histologically similar, marked biochemical differences exist. Mature degradation-resistant collagen cross-links, such as Pyd form, in murine but not zebrafish infarcts and likely explains why zebrafish can resorb myocardial scar. Targeting Pyd formation in mammals could pave the way for novel therapeutic strategies to promote scar resolution and improve cardiac function after MI.