Journal
JOURNAL OF ENDOCRINOLOGY
Volume 220, Issue 3, Pages 277-289Publisher
BIOSCIENTIFICA LTD
DOI: 10.1530/JOE-13-0305
Keywords
oxytocin elongated form; embryo; cardiac side population; oxytocin receptor; cardiac differentiation
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Funding
- Canadian Institutes of Health Research [MOP-97992, MOP-62901]
- Canadian Heart and Stroke Foundation
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The functional oxytocin (OT) system is expressed in the human and rodent hearts. OT stimulates differentiation of cardiac stem cells into contracting cardiomyocytes (CM). In this study, we investigated OT receptors (OTR) expressed in the cells of cardiac side population (SP) and the abilities of these cells to differentiate into CM in response to the treatment with OT-Gly-Lys-Arg (OT-GKR), a dominant and biologically active form of OT, in the fetal rodent heart. Immunocytochemistry of whole rat embryo at mid gestation (E11) revealed parallel staining in the heart of OTR and the ATP-binding cassette sub-family G member 2 (brcp1) antigen the marker of the SP phenotype. Using flow cytometry, the SP cells were selected from the newborn CM stained with Hoechst 33342: 5.32%+/- 0.06% of SP and 15.2%+/- 1.10 of main population expressed OTR on the cell surface. The OTR was detected in CD29 (6.6%) and then in CD31 (4.7%) but less frequently in CD45 (0.7%) positive SP cell subpopulations. Specifically, the phenotype of SP CD31- cell, but not SP CD31+ cells, proliferates in the presence of OT-GKR and develops large cell aggregates. Then, OT-GKR treatment induced the apparition of beating cell colonies after 11 days (10 +/- 2.78%), which increased until day 16 (52 +/- 1.21%). The cells in contractile colonies expressed the markers of a CM phenotype, such as troponin, cardiac myosin light chain-2, and actinin. Finally, SP cells stimulated by OT-GKR induced endothelial phenotype. These results suggest that the C-terminally extended OT molecule stimulates cardiac differentiation of SP CD31K - cells and is involved in heart growth.
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