title: Depolarization of Cellular Resting Membrane Potential Promotes Neonatal Cardiomyocyte Proliferation In Vitro.
abstract: Cardiomyocytes (CMs) undergo a rapid transition from hyperplastic to hypertrophic growth soon after birth, which is a major challenge to the development of engineered cardiac tissue for pediatric patients. Resting membrane potential (Vmem) has been shown to play an important role in cell differentiation and proliferation during development. We hypothesized that depolarization of neonatal CMs would stimulate or maintain CM proliferationin vitro. To test our hypothesis, we isolated postnatal day 3 neonatal rat CMs and subjected them to sustained depolarization via the addition of potassium gluconate or Ouabain to the culture medium. Cell density and CM percentage measurements demonstrated an increase in mitotic CMs along with a ~2 fold increase in CM numbers with depolarization. In addition, depolarization led to an increase in cells in G2 and S phase, indicating increased proliferation, as measured by flow cytometry. Surprisingly depolarization of Vmemwith either treatment led to inhibition of proliferation in cardiac fibroblasts. This effect is abrogated when the study was carried out on postnatal day 7 neonatal CMs, which are less proliferative, indicating that the likely mechanism of depolarization is the maintenance of the proliferating CM population. In summary, our findings suggest that depolarization maintains postnatal CM proliferation and may be a novel approach to encourage growth of engineered tissue and cardiac regeneration in pediatric patients.
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA 02155 USA.
authors.forename: Jen-Yu
authors.initials: JY
authors.lastname: Lan
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA 02155 USA.
authors.forename: Corin
authors.initials: C
authors.lastname: Williams
authors.affiliation: Department of Biology, Tufts University, Medford, MA 02155 USA ; Center for Regenerative and Developmental Biology, Tufts University, Medford, MA 02155 USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Levin
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA 02155 USA ; Cellular, Molecular and Developmental Biology Program, Sackler Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111 USA.
authors.forename: Lauren Deems
authors.initials: LD
authors.lastname: Black
keywords: Akt pathway; Cardiac Fibroblasts; Cell cycle; ouabain; potassium gluconate