Contraction-relaxation function and mechano-chemical coupling of myofibrils

Investigations of human, human pluripotent stem cell-derived cardiomyocytes and animal contractile models in non-pathologic and pathologic conditions



Contraction-relaxation function and mechano-chemical coupling of myofibrils.

The main function of cardiomyocytes (CMs) to generate force and shorten their length occurs when the subcellular myofibrils contract due to multiple interactions between ATPase-driven myosin motors and actin filaments. Myofibrils consist in many sarcomeres arranged in series driving directly the contraction-relaxation events of CMs upon cyclical variation of the intracellular Ca2+ concentration. Therefore, isolated myofibrils represent a contractile model used to understand sarcomeric protein-related processes that determine contractile function of CMs in the absence of Ca2+ handling systems and of upstream signaling.

Myofibrils can be investigated using fast kinetic micromechanical and chemical techniques because they are thin and in rapid diffusional equilibrium with their surrounding environment. We have established a micromechanical setup that uses an atomic force cantilever as a nN-sensitive force sensor. This setup allows rapid changes of the solutions to which myofibrils are exposed, and the force kinetic parameters of myofibrillar activation and relaxation at different Ca2+ concentrations can be analyzed with high time resolution. Different established biochemical methods can assess the steady-state or transient ATPase activity of the sarcomeric myosin motor using mechanical unloaded, native myofibrils or using myofibrils prevented from shortening by chemical cross-linking few of their myosin heads to the actin filaments. These investigations can allow correlating the biochemical events to the mechanical events during cross-bridge cycling based on isoform composition of sarcomeric proteins.

Subcellular myofibrils can be obtained from human (e.g., biopsies), human-derived and non-human cardiac and skeletal small muscle samples (e.g., mouse, rat, rabbit, zebrafish and hESC-/hiPSC-CMs).


In vitro-differentiated cardiomyocytes.

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) hold great potential for the treatment of cardiovascular diseases by cell transplantation or engineered cardiac tissue, for assessing efficiency and toxicity of pharmacological compounds, or to be used as cellular disease models in vitro. hPSC-CMs exhibit a series of immature features compared to ventricular CMs of an adult human heart. Therefore, characterization of hPSC-CMs at different hierarchically interrelated levels (molecular, subcellular, cellular and multicellular levels) and understanding how extracellular environment and intracellular factors may affect subcellular myofibrils and cell maturation of hPSC-CMs, in pathologic and non-pathologic conditions, represents important research objectives to us.


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Group members:

Shared personal:   

     - Meißner Joachim (molecular and cell biology)

     - Birgit Piep (proteins analysis)

     - Alexander Lingk (mechanics)

     - Torsten Beier (optics and optoelectronics)

     - Uwe Krumm (electronics)






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