Abstract Background Injecting human induced pluripotent stem (iPS) cell-derived cardiomyocytes directly into the heart muscle holds promise as a treatment for heart failure. Achieving better engraftment is crucial for maximizing therapeutic effectiveness. Collagen peptide (CP) is a form of hydrolyzed gelatin known for its resistance to solidification. By adjusting its concentration, the viscosity of CP can be easily managed, potentially influencing the retention and engraftment efficiency of transplanted cells. Purpose We investigated the impact of different CP concentrations as a solvent for intramyocardial injection of human iPS cell-derived cardiomyocytes. Methods Initially, we examined the leakage of CP solution from the injection site using chicken meat and ex vivo rat heart. Subsequently, an in vivo experiment was conducted using beating rat myocardium injected with CP solution and Indian ink to assess CP diffusion in dynamic heart tissue. Finally, we performed intramyocardial injections of human iPS cell-derived cardiomyocytes onto a myocardial infarction model in immunosuppressed rats (1.0×107 cells/rat), followed by echocardiographic evaluation of cardiac function four weeks post-transplantation (N=3-6). Results There was less leakage from the injection site at lower CP concentration (10%) compared to higher concentration (20%), particularly in chicken or ex vivo rat heart tissue under static, non-beating conditions (chicken; 10% vs. 20% CP: 3.2±0.7% vs. 11.6±0.8%, P=0.01 / rat heart; 1.5±0.9% vs. 6.8±1.1%, P=0.0072). However, when examining fluid leakage from the cross-section of ex vivo rat hearts, we observed significantly higher leakage, regardless of CP concentration (10% CP: 45.7±2.7%, 20% CP: 59.1±8.1%), suggesting that CP diffusion within myocardial tissues had a greater influence on local retention than leakage from the injection site. Subsequently, in an experiment using beating rat myocardium and Indian ink, we observed significant suppression of diffusion in tissues treated with CP solution, with the 20% concentration showing a tendency to remain at the injection site (0% CP: 24.5±6.2 mm2, 10% CP: 6.9±7.1 mm2, 20% CP: 10.6±3.3 mm2, P=0.005). This indicates that 20% CP, rather than 10% CP, may be more suitable for local retention in tissues experiencing intra-tissue pressure, such as the beating myocardium. Finally, in vivo experiment using a myocardial infarction model of rat, there was no significant difference in left ventricular ejection fraction (LVEF) when cardiomyocytes were transplanted with 10% CP (0% CP: 56.1±8.9%, 10%CP: 61.9±5.2%, P=0.92). However, there was a trend towards improved LVEF with the 20% CP solution (0% CP: 56.1±8.9%, 20%CP: 68.8±7.9%, P=0.13), Conclusion Twenty-percent CP may be more beneficial for treating myocardial ischemia due to enhanced retention and engraftment of transplanted cardiomyocytes.
Read full abstract