Quantification of cardiac fibrosis by colour-subtractive computer-assisted image analysis

1. Quantification of fibrosis is a key parameter in the assessment of the severity of cardiovascular disease and efficacy of future candidate therapies. Computer-assisted methods are frequently used to assess cardiac fibrosis in several experimental models. A brief survey indicated that there is a clear dearth of literature outlining detailed methodologies for computer-based assessment of cardiac fibrosis. The purpose of the present study was to provide a reliable method for a systematic assessment of cardiac fibrosis. 2. We induced cardiac fibrosis by isoproterenol (ISO) infusion in adult CD1 male mice and quantified fibrosis using a recently developed colour-subtractive computer-assisted image analysis (CS-CAIA) technique. Here, we provided a detailed description of our methodology to facilitate its wider use by other researchers. 3. We showed that the severity of ISO-induced cardiac fibrosis was similar in the apex, mid-ventricular ring and base of the adult CD1 mouse heart. In contrast with other species, such as rats and dogs, we found that uniform expression of β₁-adrenoceptors between different regions in CD1 mouse hearts correlated well with uniform induction of cardiac fibrosis. 4. A previous study found a negative correlation between levels of myocardial fibrosis and the degree of cardiac hypertrophy in ISO-treated Wistar rats. In contrast, we found a similar degree of cardiac fibrosis in our ISO-treated CD1 mice. 5. Our results suggest that CD1 mice are an ideal model system to study catecholamine-induced cardiac remodelling, as well as to screen candidate antifibrotic agents for future therapies.