Wnt modulators, SFRP-1, and SFRP-2 are expressed in osteoblasts and differentially regulate hematopoietic stem cells.
Wnt signaling has been implicated in the self-renewal of hematopoietic stem cells (HSCs). Secreted frizzled-related proteins (SFRPs) are a family of soluble proteins containing a region homologous to a receptor for Wnt, Frizzled, and are thought to act as endogenous modulators for Wnt signaling. This study examined the role of SFRPs in HSC regulation. Among the four family members, SFRP-1 and SFRP-2 are specifically induced in the bone marrow in response to myelosuppression, and immunostaining revealed that both proteins were expressed in osteoblasts. Interestingly, SFRP-1 reduced the number of multipotent progenitors in in vitro culture of CD34(-)KSL cells, while SFRP-2 did not. Furthermore, SFRP-1 compromised the long-term repopulating activity of HSCs, whereas SFRP-2 did not affect or even enhanced it in the same setting. These results indicate that although both SFRP-1 and SFRP-2 act as inhibitors for Wnt signaling in vitro, they differentially affect the homeostasis of HSCs.
Nakajima
Hideaki
H
Division of Hematology, Department of Internal Medicine, Keio University School of Medicine, Tokyo 160-8582, Japan. hnakajim@sc.itc.keio.ac.jp
Ito
Miyuki
M
Morikawa
Yoshihiro
Y
Komori
Tadasuke
T
Fukuchi
Yumi
Y
Shibata
Fumi
F
Okamoto
Shinichiro
S
Kitamura
Toshio
T
D000818:Animals; D002454:Cell Differentiation; D019070:Cell Lineage; D049109:Cell Proliferation; D005472:Fluorouracil / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000378:metabolism*; D051153:Wnt Proteins / Q000378:metabolism*; D060508:Wnt3 Protein; D000094742:Secreted Frizzled-Related Proteins
D005472:Fluorouracil; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051153:Wnt Proteins; D060508:Wnt3 Protein; C485539:Sfrp1 protein, mouse; D000094742:Secreted Frizzled-Related Proteins; C491628:Sfrp2 protein, mouse