title: Enrichment of cardiac pacemaker-like cells: neuregulin-1 and cyclic AMP increase I(f)-current density and connexin 40 mRNA levels in fetal cardiomyocytes.
abstract: Generation of a large number of cells belonging to the cardiac pacemaker system would constitute an important step towards their utilization as a biological cardiac pacemaker system. The aim of the present study was to identify factors, which might induce transformation of a heterogenous population of fetal cardiomyocytes into cells with a pacemaker-like phenotype. Neuregulin-1 (alpha- and beta-isoform) or the cAMP was added to fresh cell cultures of murine embryonic cardiomyocytes. Quantitative northern blot analysis and flowcytometry were performed to detect the expression of connexins 40, 43 and 45. Patch clamp recordings in the whole cell configuration were performed to determine current density of I (f), a characteristic ion current of pacemaker cells. Fetal cardiomyocytes without supplement of neuregulin or cAMP served as control group. Neuregulin and cAMP significantly increased mRNA levels of connexin 40 (Cx-40), a marker of the early differentiating conduction system in mice. On the protein level, flowcytometry revealed no significant differences between treated and untreated groups with regard to the expression of connexins 40, 43 and 45. Treatment with cAMP (11.2 +/- 2.24 pA/pF; P < 0.001) and neuregulin-1-beta (6.23 +/- 1.07 pA/pF; P < 0.001) significantly increased the pacemaker current density compared to control cardiomyocytes (1.76 +/- 0.49 pA/pF). Our results indicate that neuregulin-1 and cAMP possess the capacity to cause significant transformation of a mixed population of fetal cardiomyocytes into cardiac pacemaker-like cells as shown by electrophysiology and increase of Cx-40 mRNA. This method may allow the development of a biological cardiac pacemaker system when applied to adult or embryonic stem cells.
authors.affiliation: Department of Cardiac Surgery, University of Heidelberg, Heidelberg, Germany. Arjang.Ruhparwar@med.uni-heidelberg.de
authors.forename: Arjang
authors.initials: A
authors.lastname: Ruhparwar
authors.forename: Fikret
authors.initials: F
authors.lastname: Er
authors.forename: Ulrich
authors.initials: U
authors.lastname: Martin
authors.forename: Kristin
authors.initials: K
authors.lastname: Radke
authors.forename: Ina
authors.initials: I
authors.lastname: Gruh
authors.forename: Michael
authors.initials: M
authors.lastname: Niehaus
authors.forename: Matthias
authors.initials: M
authors.lastname: Karck
authors.forename: Axel
authors.initials: A
authors.lastname: Haverich
authors.forename: Uta C
authors.initials: UC
authors.lastname: Hoppe
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D015152:Blotting, Northern / Q000379:methods; D002454:Cell Differentiation; D002478:Cells, Cultured; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology*; D053595:Embryonic Stem Cells / Q000378:metabolism*; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D032383:Myocytes, Cardiac / Q000378:metabolism*; D020890:Neuregulin-1 / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D000097003:Gap Junction alpha-5 Protein
chemical_list: D015415:Biomarkers; D018031:Connexin 43; D017630:Connexins; D000242:Cyclic AMP; D020890:Neuregulin-1; D015221:Potassium Channels; D012333:RNA, Messenger; D000097003:Gap Junction alpha-5 Protein; C082920:connexin 45