Optimization of Fluorescent Labeling for In Vivo Nanoimaging of Sarcomeres in the Mouse Heart

The present study was conducted to systematically investigate the optimal viral titer as well as the volume of the adenovirus vector (ADV) that expresses alpha-actinin-AcGFP in the Z-disks of myocytes in the left ventricle (LV) of mice. An injection of 10 mu L ADV at viral titers of 2 to 4 x 10(11) viral particles per mL (VP/mL) into the LV epicardial surface consistently expressed alpha-actinin-AcG FP in myocytes in vivo, with the fraction of AcG FP-expressing myocytes at similar to 10%. Our analysis revealed that SI, was similar to 1.90-2.15 mu m upon heart arrest via deep anesthesia. Likewise, we developed a novel fluorescence labeling method of the T-tubular system by treating the LV surface with CellMask Orange (CellMask). We found that the T-tubular distance similar to 2.10-2.25 mu m, similar to SL, in the healthy heart in vivo. Therefore, the present high-precision visualization method for the Z-disks or the T-tubules is beneficial to unveiling the mechanisms of myocyte contraction in health and disease in vivo.