Hematopoietic stem cell regeneration through paracrine regulation of the Wnt5a/Prox1 signaling axis
Qiqi Lin, Limei Wu, Srinivas Chatla, Fabliha A. Chowdhury, Neha Atale, Jonathan Joseph, Wei Du
Qiqi Lin, Limei Wu, Srinivas Chatla, Fabliha A. Chowdhury, Neha Atale, Jonathan Joseph, Wei Du
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Research Article Cell biology Hematology

Hematopoietic stem cell regeneration through paracrine regulation of the Wnt5a/Prox1 signaling axis

Abstract

The crosstalk between the BM microenvironment (niche) and hematopoietic stem cells (HSCs) is critical for HSC regeneration. Here, we show that in mice, deletion of the Fanconi anemia (FA) genes Fanca and Fancc dampened HSC regeneration through direct effects on HSCs and indirect effects on BM niche cells. FA HSCs showed persistent upregulation of the Wnt target Prox1 in response to total body irradiation (TBI). Accordingly, lineage-specific deletion of Prox1 improved long-term repopulation of the irradiated FA HSCs. Forced expression of Prox1 in WT HSCs mimicked the defective repopulation phenotype of FA HSCs. WT mice but not FA mice showed significant induction by TBI of BM stromal Wnt5a protein. Mechanistically, FA proteins regulated stromal Wnt5a expression, possibly through modulating the Wnt5a transcription activator Pax2. Wnt5a treatment of irradiated FA mice enhanced HSC regeneration. Conversely, Wnt5a neutralization inhibited HSC regeneration after TBI. Wnt5a secreted by LepR+CXCL12+ BM stromal cells inhibited β-catenin accumulation, thereby repressing Prox1 transcription in irradiated HSCs. The detrimental effect of deregulated Wnt5a/Prox1 signaling on HSC regeneration was also observed in patients with FA and aged mice. Irradiation induced upregulation of Prox1 in the HSCs of aged mice, and deletion of Prox1 in aged HSCs improved HSC regeneration. Treatment of aged mice with Wnt5a enhanced hematopoietic repopulation. Collectively, these findings identified the paracrine Wnt5a/Prox1 signaling axis as a regulator of HSC regeneration under conditions of injury and aging.

Authors

Qiqi Lin, Limei Wu, Srinivas Chatla, Fabliha A. Chowdhury, Neha Atale, Jonathan Joseph, Wei Du

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Figure 2

FA deficiency dampens HSC regeneration after irradiation.

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FA deficiency dampens HSC regeneration after irradiation. (A) Donor (CD4...
(A) Donor (CD45.2+) cell engraftment at 16 weeks in recipient CD45.1+ mice that were transplanted with 100 BM SLAM cells from nonirradiated and irradiated WT, Fanca–/–, and Fancc–/– mice, along with 2 × 105 competing CD45.1+ WT BM cells. Representative flow cytometry analysis (left) and quantification (right) are shown (WT TBI–: n = 6; WT TBI+: n = 8; Fanca–/– TBI–: n = 6; Fancc–/– TBI+: n = 7; Fancc–/–: n = 6). (B) Donor myeloid (Mac1/Gr1), B cell (B220), and T cell (CD3ε) engraftment levels at 16 weeks are shown (WT TBI–: n = 6; WT TBI+: n = 8; Fanca–/– TBI–: n = 6; Fancc–/– TBI+: n = 7; Fancc–/–: n = 6). (C) Donor HSC engraftment at 16 weeks. Mean percentages of CD45.2+ SLAM cells are shown for each group (WT TBI–: n = 6; WT TBI+: n = 8; Fanca–/– TBI–: n = 6; Fancc–/– TBI+: n = 7; Fancc–/–: n = 6). (D and E) Mean levels of donor CD45.2+ cell (D) and lineage engraftment (E) in secondary recipient CD45.1+ mice at 16 weeks after competitive transplantation with BM cells from the primary mice in A (WT TBI–: n = 8; WT TBI+: n = 10; Fanca–/–: n = 8; Fancc–/–: n = 8 in D; WT TBI–: n = 8; WT TBI+: n = 10; Fanca–/–: n = 8; Fancc–/–: n = 8 in E). Statistics were performed in the indicated groups: 2-tailed, paired t test (parametric). *P < 0.05; **P < 0.01.