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.

中文翻译：

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独立于染料的方法可揭示造血干细胞中线粒体质量的升高。

造血干细胞（HSC）通过糖酵解而非线粒体呼吸产生大部分细胞能量。与这一观点一致，据报道HSCs中线粒体的质量很低。但是，我们发现使用MitoTracker Green（一种用于测量线粒体含量的常用染料）染色会由于染料外流而导致人造荧光降低，尤其是在HSC中。使用mtDNA定量，线粒体核苷酸的枚举以及遗传编码的线粒体报道分子的荧光强度，我们在这里明确表明，HSC和多能祖细胞（MPP）的线粒体质量高于谱系提交的祖细胞和成熟细胞。尽管线粒体质量相似，但MPP的呼吸能力却超过了HSC。此外，尽管已经通过提高线粒体吞噬来解释HSC中的线粒体质量低，但我们观察到HSC中的线粒体周转能力相对较低。我们建议，鉴于这些发现，可能必须重新探讨线粒体在HSC生物学中的作用。