title: Micron-scale voltage and [Ca(2+)]i imaging in the intact heart.
abstract: Studies in isolated cardiomyocytes have provided tremendous information at the cellular and molecular level concerning regulation of transmembrane voltage (Vm) and intracellular calcium ([Ca(2+)]i). The ability to use the information gleaned to gain insight into the function of ion channels and Ca(2+) handling proteins in a more complex system, e.g., the intact heart, has remained a challenge. We have developed laser scanning fluorescence microscopy-based approaches to monitor, at the sub-cellular to multi-cellular level in the immobilized, Langendorff-perfused mouse heart, dynamic changes in [Ca(2+)]i and Vm. This article will review the use of single- or dual-photon laser scanning microscopy [Ca(2+)]i imaging in conjunction with transgenic reporter technology to (a) interrogate the extent to which transplanted, donor-derived myocytes or cardiac stem cell-derived de novo myocytes are capable of forming a functional syncytium with the pre-existing myocardium, using entrainment of [Ca(2+)]i transients by the electrical activity of the recipient heart as a surrogate for electrical coupling, and (b) characterize the Ca(2+) handling phenotypes of cellular implants. Further, we will review the ability of laser scanning fluorescence microscopy in conjunction with a fast-response voltage-sensitive to resolve, on a subcellular level in Langendorff-perfused mouse hearts, Vm dynamics that typically occur during the course of a cardiac action potential. Specifically, the utility of this technique to measure microscopic-scale voltage gradients in the normal and diseased heart is discussed.
authors.affiliation: Riley Heart Research Center, Department of Pediatrics, Wells Center for Pediatric Research, Indiana University School of Medicine Indianapolis, IN, USA.
authors.forename: Xiao-Long
authors.initials: XL
authors.lastname: Lu
authors.affiliation: Riley Heart Research Center, Department of Pediatrics, Wells Center for Pediatric Research, Indiana University School of Medicine Indianapolis, IN, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Rubart
keywords: Langendorff-perfused heart; laser scanning microscopy; optical [Ca2+]i mapping; optical voltage mapping; stem cell transplantation