Human Induced Pluripotent Stem Cells as an In Vitro model for Human Cardiomyocytes to Study Maturation and Metabolism

This project aimed to generate a mature population of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM) which would have the metabolic phenotype of cardiomyocytes in the adult heart as metabolic disorders are strongly linked with cardiovascular disease. Two published differentiation protocols were assessed, and the Wnt-modulation protocol was chosen as it upregulated the gene expression of cardiac genes. In addition, after introducing some alterations, such as transient hypoxia and the addition of Activin A, spontaneously beating human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) were generated. We characterised the changes in substrate metabolism after differentiation and showed that as hiPSCs are differentiated into beating hiPSC-CMs, there was an increase in both glycolysis and fatty acid oxidation, associated with changes in mRNA expression of glucose and fatty acid metabolism genes. Addition of a PPAR-α agonist (WY14643) to hiPSCs during differentiation did not induce changes in gene expression or substrate metabolism, however addition of the agonist in combination with oleic acid to beating hiPSC-CMs upregulated fatty acid oxidation and respiratory reserve capacity. Interestingly, in beating hiPSC-CM, the addition of oleic acid alone upregulated pyruvate oxidation but not that of oleic acid. There was no change in glycolytic flux with either treatment, suggesting that although activation of PPAR-α increased the capacity of the cells for fatty acid oxidation, they could generate sufficient energy from the high glucose in the culture medium via glycolysis. In conclusion, as hiPSC-CMs are differentiated there is an upregulation in both glycolysis and fatty acid oxidation. This maturation of metabolism can be further enhanced when PPAR-α is activated using WY14643 in the presence of fatty acids. This provides a method to metabolically mature hiPSC-CMs, so that they more closely resemble mature cardiomyocytes.