Loss of Sfrp2 in the Niche Amplifies Stress-Induced Cellular Responses, and Impairs the In Vivo Regeneration of the Hematopoietic Stem Cell Pool.
Sfrp2 is overexpressed in stromal cells which maintain hematopoietic stem cells (HSCs) during in vitro culture. We here showed, that coculture of hematopoetic cells with stromal cells with reduced expression of Sfrp2 increases the number lineage-negative Kit(+) Sca-1(+) (LSK) and progenitor cells in vitro. The LSK cells from these cocultures showed activation of canonical Wnt signaling, higher levels of Ki-67, BrdU incorporation, and the number of γH2A.X positive foci. Total repopulating activity of these cultures was, however, diminished, indicating loss of HSC. To extend these in vitro data, we modelled stress in vivo, i.e., by aging, or 5-FU treatment in Sfrp2(-) (/) (-) mice, or replicative stress in regeneration of HSCs in Sfrp2(-) (/) (-) recipients. In all three in vivo stress situations, we noted an increase of LSK cells, characterized by increased levels of β-catenin and cyclin D1. In the transplantation experiments, the increase in LSK cells in primary recipients was subsequently associated with a progressive loss of HSCs in serial transplantations. Similar to the in vitro coculture stress, in vivo genotoxic stress in 5-FU-treated Sfrp2(-) (/) (-) mice increased cell cycle activity of LSK cells with higher levels of BrdU incorporation, increased expression of Ki-67, and canonical Wnt signaling. Importantly, as noted in vitro, increased cycling of LSKs in vivo was accompanied by a defective γH2A.X-dependent DNA damage response and depolarized localization of acetylated H4K16. Our experiments support the view that Sfrp2 expression in the niche is required to maintain the HSC pool by limiting stress-induced DNA damage and attenuating canonical Wnt-mediated HSC activation. Stem Cells 2016;34:2381-2392.
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Franziska
F
Ruf
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Christina
C
Schreck
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Alina
A
Wagner
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Sandra
S
Grziwok
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Charlotta
C
Pagel
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Sandra
S
Romero
Institute of Medical Genetics, Medical University of Vienna, Vienna, Austria.
Matthias
M
Kieslinger
RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.
Akihiko
A
Shimono
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.|German Cancer Consortium (DKTK) and the German Cancer Research Center (DKFZ), Heidelberg, Germany.
Christian
C
Peschel
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.|German Cancer Consortium (DKTK) and the German Cancer Research Center (DKFZ), Heidelberg, Germany.
Katharina S
KS
Götze
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany.
Rouzanna
R
Istvanffy
3rd Department of Internal Medicine, Klinikum Rechts Der Isar, Technische Universität München, Munich, Germany. robert.oostendorp@tum.de.
Robert A J
RA
Oostendorp
D000375:Aging / Q000378:metabolism; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D060833:Cellular Microenvironment / Q000187:drug effects; D016922:Cellular Senescence / Q000187:drug effects; D018920:Coculture Techniques; D004249:DNA Damage; D005472:Fluorouracil / Q000494:pharmacology; D006410:Hematopoiesis / Q000187:drug effects; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000172:deficiency* / Q000378:metabolism; D008810:Mice, Inbred C57BL; D012038:Regeneration / Q000187:drug effects; D055153:Stem Cell Niche / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism; D000094742:Secreted Frizzled-Related Proteins
D005472:Fluorouracil; D008565:Membrane Proteins; C491628:Sfrp2 protein, mouse; D000094742:Secreted Frizzled-Related Proteins
Cell cycle; HSC; Microenvironment; Model; Niche; SFRP2; Self-renewal; Stress