Functional assessment of myoblast transplantation for cardiac repair with magnetic resonance imaging

Background: Contraction of transplanted myoblasts and their effects on function and remodeling after myocardial infarction remain controversial. Aim: We used magnetic resonance imaging (MRI) to study wall thickening and left ventricular (LV) function and geometry after myoblast transplantation. Methods and results: Three weeks after cryo-infarction rabbits were randomized to receive an injection of ∼2×10⁸ myoblasts (n=8) or medium (n=9) into the scar. Cine MRI and contrast enhanced (ce) MRI images were acquired before injection (baseline) and 4 weeks later (endpoint). Regional wall thickening was measured at the site of transmural hyperenhancement. In the control group, regional wall thickening decreased to -15.3±8.6% at baseline, which further decreased to -18.3±5.7% at endpoint. Further, end-diastolic volume increased from 3.96±0.27 to 5.00±0.46 ml and end-systolic volume from 2.23±0.19 to 2.96±0.30 ml (both P<0.05 vs. baseline), which was accompanied by increased LV wall volumes (P<0.05 vs. baseline). In contrast, myoblast transplantation increased regional wall thickening from -11.9±15.9% at baseline to 26.9±17.0% (P<0.05 vs. control), which resulted in significantly improved two-dimensional ejection fractions at the infarct level and prevented the increase in end-diastolic and end-systolic volumes and wall volume. Conclusion: Intracardiac myoblast transplantation after myocardial infarction improves regional wall thickening and prevents progressive left ventricular remodeling.