Abstract 17301: AMP-Dependent Protein Kinase Regulates Mitochondrial Reprogramming and Differentiation Potential of Cardiac Progenitor Cells
Activation and participation of cardiac progenitor cells (CPCs) in regeneration are critical for effective repair in the wake of pathologic injury. The process of stem cell activation and commitment involves increased energy demand and mitochondrial biogenesis. However, significant gaps exist in our knowledge of CPC differentiation, and little attention has been paid to alterations in mitochondria during differentiation. In this study, we have investigated the mechanisms of mitochondrial maturation integral to the execution of a cardiac differentiation program. We found that uncommitted c-kit+ CPCs contain an under-developed network of few mitochondria that localize in the perinuclear region. In contrast, after incubation in differentiation medium, mitochondria displayed a dramatic change with increased mitochondrial mass and formation of a large network as the CPCs grew in size. Expansion of the mitochondrial network correlated with cardiac lineage commitment as detected by real time PCR for GATA4, MEF2C and Actinin. Moreover, differentiation induced expression of mitochondrial biogenesis proteins PGC-1α, NRF-1 and Tfam, which correlated with an increase in the number of mitochondria as well as enhanced oxidative capacity and cellular ATP levels. AMP-dependent protein kinase (AMPK) is an energy sensor that is activated in response to increased energy demand in cells. Since differentiation requires energy and PGC-1α is a known downstream target of AMPK, we examined the role of AMPK in regulating mitochondrial expansion and differentiation in CPCs in vivo and in vitro. We found that AMPK protein levels and phosphorylation drastically increased during differentiation of CPCs in vitro. Moreover, CPCs are known to migrate to the border zone after myocardial infarction (MI), where they proliferate and differentiate into distinct cardiac lineages. We found that a majority of the c-kit+ cells in the border zone were positive for p-AMPK after MI. Inhibiting AMPK with Compound C prevented both expansion of the mitochondrial network and differentiation in CPCs in vitro. These data suggest that mitochondrial expansion by AMPK and PGC-1α play an essential role in CPC differentiation and defects in this process will impair their repair capacity.
- © 2012 by American Heart Association, Inc.