Joseph Wu, Postdoctoral Faculty Sponsor
Integrated Ca2+ flux and AFM force analysis in human iPSC-derived cardiomyocytes.
We developed a new approach for combined analysis of calcium (Ca2+) handling and beating forces in contractile cardiomyocytes. We employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from dilated cardiomyopathy (DCM) patients carrying an inherited mutation in the sarcomeric protein troponin T (TnT), and isogenic TnT-KO iPSC-CMs generated via CRISPR/Cas9 gene editing. In these cells, Ca2+ handling as well as beating forces and-rates using single-cell atomic force microscopy (AFM) were assessed. We report impaired Ca2+ handling and reduced contractile force in DCM iPSC-CMs compared to healthy WT controls. TnT-KO iPSC-CMs display no contractile force or Ca2+ transients but generate Ca2+ sparks. We apply our analysis strategy to Ca2+ traces and AFM deflection recordings to reveal maximum rising rate, decay time, and duration of contraction with a multi-step background correction. Our method provides adaptive computing of signal peaks for different Ca2+ flux or force levels in iPSC-CMs, as well as analysis of Ca2+ sparks. Moreover, we report long-term measurements of contractile force dynamics on human iPSC-CMs. This approach enables deeper and more accurate profiling of disease-specific differences in cardiomyocyte contraction profiles using patient-derived iPSC-CMs.
View details for DOI 10.1515/hsz-2020-0212
View details for PubMedID 33108335
Proteasome-Dependent Regulation of Distinct Metabolic States During Long-Term Culture of Human iPSC-Derived Cardiomyocytes.
The immature presentation of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is currently a challenge for their application in disease modeling, drug screening, and regenerative medicine. Long-term culture is known to achieve partial maturation of iPSC-CMs. However, little is known about the molecular signaling circuitries that govern functional changes, metabolic output, and cellular homeostasis during long-term culture of iPSC-CMs.We aimed to identify and characterize critical signaling events that control functional and metabolic transitions of cardiac cells during developmental progression, as recapitulated by long-term culture of iPSC-CMs.We combined transcriptomic sequencing with pathway network mapping in iPSC-CMs that were cultured until a late time point, day 200 (D200), in comparison to a medium time point, day 90 (D90), and an early time point, day 30 (D30). Transcriptomic landscapes of long-term cultured iPSC-CMs allowed mapping of distinct metabolic stages during development of maturing iPSC-CMs. Temporally divergent control of mitochondrial metabolism was found to be regulated by cAMP/protein kinase A (PKA)- and proteasome-dependent signaling events. The PKA/proteasome-dependent signaling cascade was mediated downstream by heat shock protein 90 (Hsp90), which in turn modulated mitochondrial respiratory chain proteins and their metabolic output. During long-term culture, this circuitry was found to initiate upregulation of iPSC-CM metabolism, resulting in increased cell contractility that reached a maximum at the D200 time point.Our results reveal a PKA/proteasome- and Hsp90-dependent signaling pathway that regulates mitochondrial respiratory chain proteins and determines cardiomyocyte energy production and functional output. These findings provide deeper insight into signaling circuitries governing metabolic homeostasis in iPSC-CMs during developmental progression.
View details for DOI 10.1161/CIRCRESAHA.118.313973
View details for PubMedID 31104567