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Myocardial Infarction in Neonatal Mice, A Model of Cardiac Regeneration
Published on: May 24, 2016
Depolarization of Cellular Resting Membrane Potential Promotes Neonatal Cardiomyocyte Proliferation In Vitro
Jen-Yu Lan1, Corin Williams1, Michael Levin2
1Department of Biomedical Engineering, Tufts University, Medford, MA 02155 USA.
Insights
Depolarizing cardiomyocytes (CMs) in neonatal rats promotes their proliferation, offering a potential strategy for cardiac tissue engineering and regeneration in children. This method also inhibits cardiac fibroblast growth.
Area of Science:
- Cardiology
- Developmental Biology
- Biomedical Engineering
Background:
- Cardiomyocytes transition from hyperplasia to hypertrophy post-birth, complicating pediatric cardiac tissue engineering.
- Resting membrane potential (Vmem) influences cell differentiation and proliferation during development.
Purpose of the Study:
- To investigate if depolarization of neonatal cardiomyocytes stimulates or maintains their proliferation in vitro.
- To explore the potential of Vmem modulation for enhancing engineered cardiac tissues and pediatric cardiac regeneration.
Main Methods:
- Neonatal rat cardiomyocytes (postnatal day 3) were cultured with sustained depolarization using potassium gluconate or Ouabain.
- Cell proliferation was assessed by cell density, CM percentage, and flow cytometry (G2 and S phase analysis).
- Effects on cardiac fibroblast proliferation were also evaluated.
Main Results:
- Depolarization increased cardiomyocyte numbers by approximately two-fold and promoted mitotic activity.
- Flow cytometry confirmed increased cardiomyocyte proliferation, with more cells in G2 and S phases.
- Unexpectedly, depolarization inhibited cardiac fibroblast proliferation, an effect absent in older (postnatal day 7) cardiomyocytes.
Conclusions:
- Sustained depolarization of resting membrane potential maintains postnatal cardiomyocyte proliferation.
- This approach may offer a novel strategy for promoting growth in engineered cardiac tissues and aiding cardiac regeneration in pediatric patients.
- Depolarization selectively inhibits cardiac fibroblast proliferation, suggesting a targeted benefit for cardiomyocyte expansion.
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 proliferation in 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 Vmem with 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.
