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Hoyer, Friedrich

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Hoyer, Friedrich

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Author's Publications: search.filters.isAuthorOfPublication.ed61f191-aacb-4427-bc86-95cf8eb6e691

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    Macrophages retain hematopoietic stem cells in the spleen via VCAM-1
    (The Rockefeller University Press, 2015) Dutta, Partha; Hoyer, Friedrich; Grigoryeva, Lubov S.; Sager, Hendrik B.; Leuschner, Florian; Courties, Gabriel; Borodovsky, Anna; Novobrantseva, Tatiana; Ruda, Vera M.; Fitzgerald, Kevin; Iwamoto, Yoshiko; Wojtkiewicz, Gregory; Sun, Yuan; Da Silva, Nicolas; Libby, Peter; Anderson, Daniel; Swirski, Filip; Weissleder, Ralph; Nahrendorf, Matthias
    Splenic myelopoiesis provides a steady flow of leukocytes to inflamed tissues, and leukocytosis correlates with cardiovascular mortality. Yet regulation of hematopoietic stem cell (HSC) activity in the spleen is incompletely understood. Here, we show that red pulp vascular cell adhesion molecule 1 (VCAM-1)+ macrophages are essential to extramedullary myelopoiesis because these macrophages use the adhesion molecule VCAM-1 to retain HSCs in the spleen. Nanoparticle-enabled in vivo RNAi silencing of the receptor for macrophage colony stimulation factor (M-CSFR) blocked splenic macrophage maturation, reduced splenic VCAM-1 expression and compromised splenic HSC retention. Both, depleting macrophages in CD169 iDTR mice or silencing VCAM-1 in macrophages released HSCs from the spleen. When we silenced either VCAM-1 or M-CSFR in mice with myocardial infarction or in ApoE−/− mice with atherosclerosis, nanoparticle-enabled in vivo RNAi mitigated blood leukocytosis, limited inflammation in the ischemic heart, and reduced myeloid cell numbers in atherosclerotic plaques.
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    Myocardial Infarction Activates CCR2+ Hematopoietic Stem and Progenitor Cells
    (Elsevier BV, 2015) Dutta, Partha; Sager, Hendrik B; Stengel, Kristy R.; Nahrendorf, Kamila; Courties, Gabriel; Saez, Borja; Silberstein, Lev; Heidt, Timo; Sebas, Matthew; Sun, Yuan; Wojtkiewicz, Gregory; Feruglio, Paolo Fumene; King, Kevin Robert; Baker, Joshua N.; van der Laan, Anja M.; Borodovsky, Anna; Fitzgerald, Kevin; Hulsmans, Maarten; Hoyer, Friedrich; Iwamoto, Yoshiko; Vinegoni, Claudio; Brown, Dennis; Di Carli, Marcelo; Libby, Peter; Hiebert, Scott W.; Scadden, David; Swirski, Filip; Weissleder, Ralph; Nahrendorf, Matthias
    Following myocardial infarction (MI), myeloid cells derived from the hematopoietic system drive a sharp increase in systemic leukocyte levels that correlates closely with mortality. The origin of these myeloid cells, and the response of hematopoietic stem and progenitor cells (HSPCs) to MI, however, is unclear. Here, we identify a CCR2+CD150+CD48− LSK hematopoietic subset as the most upstream contributor to emergency myelopoiesis after ischemic organ injury. This subset has 4-fold higher proliferation rates than CCR2−CD150+CD48− LSK cells, displays a myeloid differentiation bias, and dominates the migratory HSPC population. We further demonstrate that the myeloid translocation gene 16 (Mtg16) regulates CCR2+ HSPC emergence. Mtg16−/− mice have decreased levels of systemic monocytes and infarct-associated macrophages and display compromised tissue healing and post-MI heart failure. Together, these data provide insights into regulation of emergency hematopoiesis after ischemic injury and identify potential therapeutic targets to modulate leukocyte output after MI.