On the macrophage contribution to stress erythropoiesis: when less is enough.

On the macrophage contribution to stress erythropoiesis: when less is enough.

Blood. 2016 Aug 19;

Authors: Ulyanova T, Phelps SR, Papayannopoulou T

Abstract
Although the importance of native bone marrow and spleen macrophages in enhancing baseline and stress erythropoiesis has been emphasized over several decades, their kinetic and phenotypic changes during a variety of stress responses have been unclear. Furthermore, whether monocyte-derived recruited macrophages can functionally substitute for inadequate or functionally impaired native macrophages has been controversial and seem to be not only tissue- but also stress-type dependent. To provide further insight into these issues, we made detailed observations at baseline and post-Erythroid stress in two mouse models with genetically depressed macrophage numbers and compared them to their controls. We documented that, irrespective of the stress induced (hemolytic, or post-Epo) treatment, only native CD11b(lo) splenic macrophages expand dramatically post-stress in normal mice without significant changes in the monocyte-derived CD11b(hi) subset. The latter remained a minority and did not change post-stress in two genetic models lacking either Spi-C or VCAM-1 with impaired native macrophage proliferative expansion. Although CD11b(lo) macrophages in these mice were 1/5(th) of normal at their peak response, surprisingly, their erythroid response was not compromised and was similar to controls. Thus, despite the prior emphasis on numerical macrophage reliance to provide functional rescue from Erythroid stress, our data highlight the importance of previously described non-macrophage dependent pathways activated under certain stress conditions to compensate for low macrophage numbers.

PMID: 27543439 [PubMed - as supplied by publisher]

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