Abstract 17345: Striated Preferentially Expressed Gene is Important for Cardiac Progenitor Cell Function
Introduction: Myosin light chain kinases are a family of proteins known to be important for myocyte function, and the striated preferentially expressed gene (Speg) is a member of this family. Disruption of the Speg gene locus in mice leads to a dilated cardiomyopathy. Also, hearts of Speg-/- mice show a reduced number of cells per mm3 of tissue, suggesting an alteration in the formation of cardiac parenchymal cells. Hypotheses: Speg is important for cardiac progenitor cell (CPC) function and the formation of cardiomyocytes, and cardiac dysfunction in Speg-/- mice can be rescued by exogenous CPCs.
Methods: c-kit+ CPCs were isolated from Speg+/+ and Speg-/- mice using fluorescence-activated cell sorting (FACS) or magnetic beads. CPCs were assessed for efficiency of clone formation, and for CPC growth and differentiation. CPCs were also injected into hearts at embryonic (E) day 13 .5, using micro-ultrasound guidance, and echocardiograms were performed on day 1 after birth.
Results: Using limited dilution assays, c-kit+ CPCs from Speg+/+ hearts demonstrated a clone formation efficiency of 6.8% after 40 days in culture, while CPCs from Speg-/- mice had a clone formation of 0.27%. In addition, Speg-/- clones were significantly smaller. Growth curves, 5 days after plating, showed that Speg+/+ CPCs generated 5-fold more cells (301±70 cells/mm2) than Speg-/- CPCs (57±9 cells/mm2). Under differentiation conditions, α-sarcomeric actin staining of CPCs revealed that 80% of Speg+/+ CPCs differentiated into cardiomyocytes in vitro, while 3% of Speg-/- CPCs were able to acquire a cardiomyocyte phenotype. To determine whether dysfunctional CPCs may contribute to the phenotype of Speg-/- mice, we administered wild-type CPCs into the hearts of Speg-/- and Speg+/+ mice, and then assessed ejection fraction (EF). We originally showed that Speg-/- mice had an EF of 23±3% compared with 74±2% for Speg+/+ hearts. After injection of exogenous CPCs, cardiac EF of Speg-/- mice was 64±8% compared with 73±4% for Speg+/+ mice.
Conclusions: These data suggest that Speg is critical for clone formation, growth potential, and differentiation of mouse CPCs. Administration of exogenous CPCs is able to rescue Speg-/- mice from the development of heart failure.
- © 2012 by American Heart Association, Inc.