Stanford Advisors


All Publications


  • Integrated Ca2+ flux and AFM force analysis in human iPSC-derived cardiomyocytes. Biological chemistry Malkovskiy, A. V., Ignatyeva, N., Dai, Y., Hasenfuss, G., Rajadas, J., Ebert, A. 2020

    Abstract

    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. Circulation research Ebert, A. n., Joshi, A. U., Andorf, S. n., Dai, Y. n., Sampathkumar, S. n., Chen, H. n., Li, Y. n., Garg, P. n., Toischer, K. n., Hasenfu╬▓, G. n., Mochly Rosen, D. n., Wu, J. C. 2019

    Abstract

    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