Serial cardiac MR assessment and histopathological evaluation of doxorubicin-induced cardiomyopathy in a miniature swine model

Figures

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  Fig. 1. (A) Experimental Design and Doxorubicin Administration in a Miniature Swine Model of Doxorubicin-Induced Cardiomyopathy. The top section shows doxorubicin preparation, with the powdered form dissolved to the required concentration for administration. The middle section illustrates the animal model setup for doxorubicin infusion, detailing the dose (60 mg/m²), cycle (every two weeks), administration site (alternating left and right auricular veins), and rate (0.5 mg/min). The bottom section presents the study timeline over 32 weeks, indicating doxorubicin administration at weeks 0, 2, 4, and 6, serial cardiac MR evaluations, and scheduled cardiac pathology sampling at specified intervals. (B)Flow chart of the experimental procedure. Eighteen pigs treated with doxorubicin were euthanized and sampled at predefined intervals: three each at 4, 8, 12, 20, and 32 weeks. One pig died at 6 weeks and two at 23 weeks, excluding them from ultrastructural analysis. Two control pigs, untreated, were euthanized at baseline for reference data

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  Fig. 2. Time Trend Analysis of LVEF, LV global Strain, and T2 Relaxation Time in Doxorubicin-Treated Miniature Pigs. The top row shows temporal changes during active doxorubicin administration, and the bottom row shows changes during the post-treatment follow-up period. LVEF: Left Ventricular Ejection Fraction; LV GLS: Left Ventricular Global Longitudinal Strain; LV GCS: Left Ventricular Global Circumferential Strain; LV GRS: Left Ventricular Global Radial Strain; T2: T2 relaxation time. Predicted values represent model-fitted values derived from the GEE models with natural cubic splines for time, based on the available longitudinal observations

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  Fig. 3. Representative images of left ventricular strain changes in miniature pigs during follow-up after doxorubicin administration. The images illustrate longitudinal (GLS), circumferential (GCS), and radial (GRS) strain at 8 weeks and 32 weeks post-treatment. Top row shows strain maps and corresponding strain curves at 8 weeks, with GLS = -11.4%, GCS = -14.6%, and GRS = 16.9%. Bottom row shows strain measurements at 32 weeks, with GLS = -12.3%, GCS = -9.4%, and GRS = 3.9%. Abbreviations are consistent with Fig. 2

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  Fig. 4. Representative cardiac pathology images at 0, 4, 8, and 32 weeks after doxorubicin administration. The top row shows HE-stained sections (200x): at baseline (0 weeks), the myocardium appears normal; at 4 weeks, HE staining shows no significant changes; at 8 weeks, some myocytes display vacuolization (indicated by blue arrows); and at 32 weeks, HE staining continues to reveal structural integrity. The bottom row shows Masson-stained sections (200x): at baseline, fibrous tissue comprises approximately 1.7% of the myocardial tissue; at 4 weeks, fibrous tissue increases slightly to about 1.9%; at 8 weeks, it decreases to 1.5%; and at 32 weeks, the fibrous tissue percentage is approximately 1.8%

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  Fig. 5. Mitochondrial Damage and T2 Changes in Myocardium Post-Doxorubicin. The top row (A1-A5) shows myocardial electron microscopy images (2000x), with detailed insets at the bottom right of A2-A4 (8000x). At 4 weeks, mitochondria display mild swelling and cristae disruption, with intact myofibrils. By 8 weeks, swelling and cristae damage are more pronounced, while myofibrils remain intact. Swelling decreases at 12 and 20 weeks. By 32 weeks, mild mitochondrial vacuolization appears, with some myofibrils showing uneven thickness and distribution, but no breaks. The bottom row (B1-B5) displays corresponding cardiac magnetic resonance T2 relaxation time images, showing a trend consistent with mitochondrial damage observed in electron microscopy