title: Cross-bridge cycling gives rise to spatiotemporal heterogeneity of dynamic subcellular mechanics in cardiac myocytes probed with atomic force microscopy.
abstract: To study how the dynamic subcellular mechanical properties of the heart relate to the fundamental underlying process of actin-myosin cross-bridge cycling, we developed a novel atomic force microscope elastography technique for mapping spatiotemporal stiffness of isolated, spontaneously beating neonatal rat cardiomyocytes. Cells were indented repeatedly at a rate close but unequal to their contractile frequency. The resultant changes in pointwise apparent elastic modulus cycled at a predictable envelope frequency between a systolic value of 26.2 +/- 5.1 kPa and a diastolic value of 7.8 +/- 4.1 kPa at a representative depth of 400 nm. In cells probed along their major axis, spatiotemporal changes in systolic stiffness displayed a heterogeneous pattern, reflecting the banded sarcomeric structure of underlying myofibrils. Treatment with blebbistatin eliminated contractile activity and resulted in a uniform apparent modulus of 6.5 +/- 4.8 kPa. This study represents the first quantitative dynamic mechanical mapping of beating cardiomyocytes. The technique provides a means of probing the micromechanical effects of disease processes and pharmacological treatments on beating cardiomyocytes, providing new insights and relating subcellular cardiac structure and function.
authors.affiliation: Department of Biomedical Engineering, Columbia University, New York, NY 10029, USA.
authors.forename: Evren U
authors.initials: EU
authors.lastname: Azeloglu
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Costa
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001696:Biomechanical Phenomena; D002478:Cells, Cultured; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism / Q000648:ultrastructure; D009218:Myosins / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D000199:Actins; D006576:Heterocyclic Compounds, 4 or More Rings; C472645:blebbistatin; D009218:Myosins