Fig. 2

Protocol optimization. a Confirmation of the necessity of cardioplegic perfusion. b Optimization of transport solution, University of Wisconsin solution (UW), cardioplegic solution (CS), Histidine-Tryptophan-Ketoglutarate solution (HTK). c Optimization of slice thickness. d Confirmation the necessity of Ca²⁺-free buffer perfusion. e–f Optimization of Ca²⁺-free buffer pH and perfusion time. g Confirmation the necessity of using protease XXIV. h Optimization of collagenase II concentration. Quantification of the rate of rod-shaped myocytes and cell viability. Data show mean ± SD from 4 fields/condition, n = 3 independent experiments. *P < 0.05, **P < 0.01, two-tailed, unpaired Student’s t-test