The blood, by night and day

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Science  28 Sep 2018:
Vol. 361, Issue 6409, pp. 1351-1352
DOI: 10.1126/science.361.6409.1351-b

Many developmental events have now been associated with the daily cycle. But what is happening physiologically during the hours of light and dark? Bone turnover, immunity, and stem cell migration from the bone marrow are certainly affected. Golan et al. observed two peaks in bone marrow hematopoietic stem and progenitor cells (HSPCs) after transient increases of norepinephrine and tumor necrosis factor. The nighttime peak increases melatonin secretion to maintain and replenish HSPCs and to reduce differentiation. By contrast, the morning peak increases differentiation and vascular permeability for blood replenishment. Hence, light and dark provide different signals that are crucial for blood cell activity and overall health.

Cell Stem Cell 10.1016/j.stem.2018.08.002 (2018).

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