Stem cell highways: signalling beats trafficking?

Abstract

This editorial refers to ‘Migratory activity of circulating progenitor cells and serum SDF-1α predict adverse events in patients with myocardial infarction’ by O. Fortunato et al. , pp. 192–200, this issue. After the oocyte is fertilized, the resulting one-cell zygote gives rise to all stem cell progenies. During the developmental process, these cells are necessary to generate all specialized tissues. However, some of them elude the specification cues and remain quiescent in the adult tissue, as long as the organism does not suffer from injury, illness, or specific cell-type depletion. Most adult stem cells are quiescent,1 others, such as the intestinal stem cells, are very active and feature intense self-renewal kinetics.2 Nevertheless, when these adult stem cells are awakened by an injury or alerted upon the body's request, they need to move on and reach the damaged area using special routs known as cellular highways ( Figure 1 ). The more advanced the illness, the less the number of stem cells remaining in stock. Their ability to migrate effectively into damaged or diseased tissues makes the stem cells promising candidates for cell therapy. Unfortunately, cellular highways can also be used by cancer (stem-) cells during metastasis, e.g. when CXCR4-expressing tumour cells migrate into the lung, liver, bone marrow, and brain, matching high levels of presented SDF-1α.3 Figure 1 SDF-1α/CXCR4 cellular highway. Chemokines control cellular traffic by directing cells that express certain chemokine receptors to specific locations where their ligands are abundant. Besides PCs (circulating progenitor cells) other stem cell types could be recruited in specific cellular highways according to their chemokine receptor expression. ESCs, embryonic stem cells; iPSCs, induced pluripotent stem cells; MABs, mesoangioblasts; MADS, multipotent adipose-derived stem cells. Fortunato et al. 4 explore the SDF-1α/CXCR4 cellular highway in the context of cardiac damage, highlighting the correlation between SDF-1α plasma concentration and …