Mitochondrial functions in stem cells.

Mitochondria fulfill multiple cellular functions beyond ATP production, including several functions that are specialized for distinct tissue types (thermogenesis, steroidogenesis). Recent evidence indicates that mitochondrial activities are regulated within cell lineages, and through incompletely understood mechanisms, are important for specification of cell fate. Stem cells represent the apex of cell lineages, capable of self-renewal and multi-potential differentiation into cells with limited proliferative capacity, and are of intense interest in regenerative medicine. Examples of stem cells include embryonic stem cells and adult somatic stem cells. Tumor-initiating cells are also often described as cancer stem cells. For all of these cell types, the association of mitochondrial bioenergetic function or other mitochondrial phenotypes raises interesting questions about the regulation of 'stemness'.