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To investigate the presence of viable myocardium in mice with acute myocardial infarction (MI) using a molecular targeted probe.
Super paramagnetic iron oxide (SPIO) nanoparticles and tenascin-C antibody were conjugated as an MRI probe. Fifteen mice with infarction were injected with SPIO-anti-tenascin-C (3 days [d], 5d, 7d after infarction; n = 5 for each group). Another five mice with infarction (5d, n = 5) were injected with SPIO for comparison. In vivo MR (7 Tesla, fast low-angle shot multi-slice T2* sequence) was performed for tracing. Histological analysis was used to compare surviving cardiomyocytes with signal changes on MR.
The mRNA expression of tenascin-C increased directly after MI and peaked at the fifth day (5d 24.29 ± 1.41 versus 3d 10.63 ± 0.72, 7d 6.56 ± 0.12; P < 0.01). T2 relaxation rate of synthesized SPIO-anti-tenascin-C was r2 = 338 mM-1 s-1. After MR, the signal changes (contrast-to-noise ratio) of the research group were 3d 6.51 ± 1.13 versus 5d 14.06 ± 3.19 versus 7d 5.02 ± 2.65, P < 0.05. The MR signal showed a small decrease in the contrast group on 5d (research group 14.06 ± 3.19 versus contrast group 1.75 ± 0.59, P < 0.05).
Tenascin-C was expressed by surviving cardiomyocytes within the infarcted region. MR imaging with SPIO-anti-tenascin-C might be used to evaluate myocardial viability of MI patients before therapy.