The adaptive response to hypertrophy is a complex process which is difficult to evaluate in terms of discrete cellular or extracellular components.
The aim of this research project is to evaluate any alterations in the mechanical characteristics and function of cells isolated from pressure overloaded hypertrophic and myopathic hearts. This will permit the evaluation of key cellular components involved in the mechanical adaptations documented in whole and multicellular heart preparations with these cardiomyopathies. Specifically, we seek to reveal any pathological changes in the three-dimensional sarcomere organization, the passive elastic properties of the cytoskeleton, and the force generating capability of the cells and their myofibrils. These properties are measured without significant contributions from any extracellular components. The A- & I-band striation patterns from optically discrete focal planes within normal and cardiomyopathic cells are projected by a microscope objective onto charge-coupled device (CCD) cameras interfaced to a digital computer. Striation patterns are digitally enhanced and reconstructed to determine individual striation positions of the myocytes. Free (unrestrained) myocytes with intact membrane systems are examined at rest or during electrically paced contractions to evaluate sarcomere lengths, domain organization and their dynamics. Contractile behavior will be modified by loading with highly viscous bathing media or osmotic stress. Other experiments will evaluate the passive and active force-length relations from chemically skinned myocytes constrained at each end with double-barrelled suction/glue pipettes. An index of force and stiffness is obtained with small induced oscillatory perturbations while overall length is externally controlled by the computer. Concurrent 2-D imaging provides a high-resolution striation monitor. The regional sarcomere length distributions are evaluated to determine the magnitude of internal cellular elastic strains that influence sarcomere uniformity and contractile kinetics under activated conditions. Comparison between cell data from normal and cardiomyopathic hearts will permit a better understanding of the role of cellular components in hypertrophic adaptation to hypertension.
| Roos, Kenneth P; Palmer, Roy E; Miller, Terrence W (2002) The role of microtubules in structural remodeling and the progression to heart failure. J Card Fail 8:S300-10 |
| Lin, G; Palmer, R E; Pister, K S et al. (2001) Miniature heart cell force transducer system implemented in MEMS technology. IEEE Trans Biomed Eng 48:996-1006 |
| Palmer, R E; Roos, K P (1997) Extent of radial sarcomere coupling revealed in passively stretched cardiac myocytes. Cell Motil Cytoskeleton 37:378-88 |
| Delbridge, L M; Roos, K P (1997) Optical methods to evaluate the contractile function of unloaded isolated cardiac myocytes. J Mol Cell Cardiol 29:11-25 |
| Palmer, R E; Brady, A J; Roos, K P (1996) Mechanical measurements from isolated cardiac myocytes using a pipette attachment system. Am J Physiol 270:C697-704 |
