Asymmetric Chromatid Segregation in Cardiac Progenitor Cells Is Enhanced by Pim-1 Kinase
Rationale: Cardiac progenitor cells (CPCs) in the adult heart are used for cell-based treatment of myocardial damage, but factors determining stemness, self-renewal, and lineage commitment are poorly understood. Immortal DNA strands inherited through asymmetrical chromatid segregation correlate with self-renewal of adult stem cells, but the capacity of CPCs for asymmetrical segregation to retain immortal strands is unknown. Cardioprotective kinase Pim-1 increases asymmetrical cell division in vivo, but the ability of Pim-1 to enhance asymmetrical chromatid segregation is unknown.
Objective: We aimed to demonstrate immortal strand segregation in CPCs and the enhancement of asymmetrical chromatid distribution by Pim-1 kinase.
Methods and Results: Asymmetrical segregation is tracked by incorporation of bromodeoxyuridine. The CPC DNA was labeled for several generations and then blocked in second cytokinesis during chase to determine distribution of immortal versus newly synthesized strands. Intensity ratios of binucleated CPCs with bromodeoxyuridine of ≥70:30 between daughter nuclei indicative of asymmetrical chromatid segregation occur with a frequency of 4.57%, and asymmetrical chromatid segregation is demonstrated at late mitotic phases. Asymmetrical chromatid segregation is significantly enhanced by Pim-1 overexpression in CPCs (9.19% versus 4.79% in eGFP-expressing cells; P=0.006).
Conclusions: Asymmetrical segregation of chromatids in CPCs is increased nearly two-fold with Pim-1 kinase overexpression, indicating that Pim-1 promotes self-renewal of stem cells.
- asymmetrical cell division
- asymmetrical chromatid segregation
- cytochalasin B
- immortal DNA strand hypothesis
- Received February 22, 2012.
- Revision received March 12, 2012.
- Accepted March 13, 2012.
- © 2012 American Heart Association, Inc.