Dye-Independent Methods Reveal Elevated Mitochondrial Mass in Hematopoietic Stem Cells

Publication date: Available online 30 November 2017
Source:Cell Stem Cell
Author(s): Mariana Justino de Almeida, Larry L. Luchsinger, David J. Corrigan, Linda J. Williams, Hans-Willem Snoeck
Hematopoietic stem cells (HSCs) produce most cellular energy through glycolysis rather than through mitochondrial respiration. Consistent with this notion, mitochondrial mass has been reported to be low in HSCs. However, we found that staining with MitoTracker Green, a commonly used dye to measure mitochondrial content, leads to artefactually low fluorescence specifically in HSCs because of dye efflux. Using mtDNA quantification, enumeration of mitochondrial nucleoids, and fluorescence intensity of a genetically encoded mitochondrial reporter, we unequivocally show here that HSCs and multipotential progenitors (MPPs) have higher mitochondrial mass than lineage-committed progenitors and mature cells. Despite similar mitochondrial mass, respiratory capacity of MPPs exceeds that of HSCs. Furthermore, although elevated mitophagy has been invoked to explain low mitochondrial mass in HSCs, we observed that mitochondrial turnover capacity is comparatively low in HSCs. We propose that the role of mitochondria in HSC biology may have to be revisited in light of these findings.

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Teaser

Snoeck and colleagues show that efflux of a mitochondrial content-reporting dye leads to the erroneous conclusion that HSCs have low mitochondrial content. Using alternative methodologies, they show that HSCs exhibit high mitochondrial content yet possess limited respiratory and turnover capacity. Mitochondria likely perform an essential yet unknown function in HSCs.


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