Related Experiment Video
Updated: Jun 13, 2025
Visualization of Cell Cycle Variations and Determination of Nucleation in Postnatal Cardiomyocytes
Published on: February 24, 2017
Quantitative label-free digital holographic imaging of cardiomyocyte optical volume, nucleation, and cell division
Herman Huang1, Sangsoon Park2, Ines Ross1
1Department of Biological Sciences, San Jose State University, San Jose, CA 95192, USA.
Insights
Newborn cardiomyocyte proliferation is lost post-birth. This study uses digital holographic imaging to show that while both mononucleated and binucleated cardiomyocytes divide after CHIR99021 treatment, binucleated cells divide less frequently, potentially due to size limitations.
Area of Science:
- Cardiovascular Biology
- Cell Biology
- Developmental Biology
Background:
- Mammalian cardiac regeneration is limited after the first week of postnatal development.
- Cardiomyocytes transition from hyperplasia to hypertrophy, withdraw from the cell cycle, and become binucleated, losing proliferative capacity.
- The impact of cell size and nucleation on cardiomyocyte proliferation remains unclear.
Purpose of the Study:
- To investigate the proliferative responses of mononucleated and binucleated cardiomyocytes using digital holographic imaging.
- To evaluate the role of cell size and nucleation in cardiomyocyte cell cycle control.
- To understand the mechanisms underlying the loss of cardiac regenerative capacity in mammals.
Main Methods:
- Application of the Holomonitor M4 digital holographic microscope for label-free, real-time tracking of primary cardiomyocyte dynamics.
- Quantitative analysis of cardiomyocyte volume and nucleation status.
- Assessment of cardiomyocyte proliferation following treatment with CHIR99021, a GSK3 inhibitor.
Main Results:
- CHIR99021 treatment induced high-frequency cell division in both mononucleated and binucleated cardiomyocytes.
- Both cell types reached a similar size-increase threshold before attempting division.
- Binucleated cardiomyocytes exhibited lower division frequency compared to mononucleated cells, possibly linked to insufficient size increase.
Conclusions:
- Digital holographic imaging provides a novel method for real-time, single-cell resolution tracking of cardiomyocyte dynamics.
- Cardiomyocyte size and nucleation are critical factors influencing cell cycle progression and division.
- Understanding these factors may elucidate the loss of mammalian cardiac regenerative potential post-birth.
Abstract:
Cardiac regeneration in newborn rodents depends on the ability of pre-existing cardiomyocytes to proliferate and divide. This capacity is lost within the first week of postnatal development when these cells rapidly switch from hyperplasia to hypertrophy, withdraw from the cell cycle, become binucleated, and increase in size. How these dynamic changes in cell size and nucleation impact cardiomyocyte proliferative potential is not well understood. In this study, we innovate the application of a commercially available digital holographic imaging microscope, the Holomonitor M4, to evaluate the proliferative responses of mononucleated and binucleated cardiomyocytes after CHIR99021 treatment, a model proliferative stimulus. This system enables long-term label-free quantitative tracking of primary cardiomyocyte dynamics in real-time with single-cell resolution. Our results confirm that chemical inhibition of glycogen synthase kinase 3 with CHIR99021 promotes complete cell division of both mononucleated and binucleated cardiomyocytes with high frequency. Quantitative tracking of cardiomyocyte volume dynamics during these proliferative events revealed that both mononucleated and binucleated cardiomyocytes reach a similar size-increase threshold prior to attempted cell division. Binucleated cardiomyocytes attempt to divide with lower frequency than mononucleated cardiomyocytes, which may be associated with inadequate increases in cell size. By defining the interrelationship between cardiomyocyte size, nucleation, and cell cycle control, we may better understand the cellular mechanisms that drive the loss of mammalian cardiac regenerative capacity after birth.
