Longitudinal relaxation time in the rotating frame (T1ρ) was measured using continuous wave irradiation in normal and infarcted mouse myocardium in vivo. Significant increase in T1ρ was found after 7 days of infarction when compared with reference myocardium or in myocardium before infarction. Cine MRI and histology were performed to verify the severity of infarction. The time course of T1ρ in the infarct fits better with granulation and scar tissue formation than necrosis and edema. The results of the study show that T1ρ could potentially be a noninvasive quantitative marker for tissue remodeling after ischemic damage.

Mechanisms of the transition from compensatory hypertrophy to heart failure are poorly understood and the roles of vascular endothelial growth factors (VEGFs) in this process have not been fully clarified. We determined the expression profile of VEGFs and relevant receptors during the progression of left ventricular hypertrophy (LVH). C57BL mice were exposed to transversal aortic constriction (TAC) and the outcome was studied at different time points (1 day, 2, 4, and 10 weeks). A clear compensatory phase (2 weeks after TAC) was seen with following heart failure (4 weeks after TAC). Interestingly, VEGF-C and VEGF-D as well as VEGF receptor-3 (VEGFR-3) were upregulated in the compensatory hypertrophy and VEGF-B was downregulated in the heart failure. After treatment with adeno-associated virus serotype 9 (AAV9)-VEGF-B(186) gene therapy in the compensatory phase for 4 weeks the function of the heart was preserved due to angiogenesis, inhibition of apoptosis, and promotion of cardiomyocyte proliferation. Also, the genetic programming towards fetal gene expression, a known phenomenon in heart failure, was partly reversed in AAV9-VEGF-B(186)-treated mice. We conclude that VEGF-C and VEGF-D are associated with the compensatory LVH and that AAV9-VEGF-B(186) gene transfer can rescue the function of the failing heart and postpone the transition towards heart failure.