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(Circulation Research. 2003;92:1176.)
© 2003 American Heart Association, Inc.

Editorials

Cell-to-Cell Coupling Between Host and Donor Cells in the In Situ Myocardium

André G. Kléber

From the Department of Physiology, University of Bern, Switzerland.

Correspondence to André G. Kléber, MD, Department of Physiology, University of Bern, Bühlplatz5, CH-3012 Bern, Switzerland. E-mail kleber@pyl.unibe.ch

Key Words: cell transplantation • intercellular junctions • connexins • Ca²⁺ transients

An extract of the first 250 words of the full text is provided, because this article has no abstract.

A trial and ventricular working myocardium consists of individual myocytes. Normal electrical and probably metabolic function implicates the presence of connexin (Cx) proteins that ensure intercellular current flow during cardiac electrical excitation. The biophysical properties, the molecular structure, and the responsiveness of connexins to metabolites, drugs, and ions have been relatively well characterized.¹ Both diffusion experiments with fluorescent molecules of varying size and double-voltage clamp experiments have shown that the pores of connexins are relatively large and allow diffusion of molecules up to a size of approximately 1000 M_r.² Connexin channels present interesting and unique features that are distinct from ion channels embedded in the cell surface membrane. Each connexin channel is formed by the docking of 2 juxtaposed connexons synthesized by the adjacent cells, and each connexon is formed by 6 connexin proteins. In heart, 3 types of connexins play a major role in different regions, Cx43, Cx40, and Cx45 (eg,^3,4). Double-immunohistochemical staining has shown that connexins are often colocalized in gap junctions. This colocalization may reflect heterotypic and/or heteromeric connexon formation. In vitro, such formation has shown to produce a multitude of electric conductance states (eg,⁵), but the exact role of mixed channels in vivo remains to be clarified.

In this issue of Circulation Research, Rubart et al demonstrate in an elegant way that embryonic cardiomyocytes (embryonic day 13), when injected into the left ventricle of adult mice of the same genetic background, fully integrate into the tissue matrix of the adult host cells . . . [Full Text of this Article]

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