Neuropilin-1 Is an Important Niche Component and Exerts Context-Dependent Effects on Hematopoietic Stem Cells.

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

• Level A · Stronger Clinical Evidence
• Level B · Emerging clinical evidence with positive signals
• Level C · Early human research exploring benefits
• Level D · Scientific groundwork from lab and animal studies
• Emerging · Emerging topic under active research

Abstract (original English)

Marrow adipocytes pose a significant problem in post-transplant regeneration of hematopoiesis owing to their negative effects on regeneration of hematopoiesis. However, the precise mechanism operative in this negative regulation is not clear. In this study, we show that marrow adipocytes express neuropilin-1 (NRP1) as a function of differentiation and inhibit regeneration of hematopoiesis by three principal mechanisms: one, by inducing apoptosis in hematopoietic stem/progenitor cells (HSPCs) through the death receptor-mediated pathway; two, by downregulating CXCR4 expression on the HSPCs through ligand-mediated internalization; and three, by secreting copious amounts of transforming growth factor β1 (TGFβ1), a known inhibitor of hematopoiesis. Silencing of NRP1 in these adipocytes rescued the apoptosis of cocultured HSPCs and boosted the CXCR4 surface expression on them, showing an active role of NRP1 in these processes. However, such silencing had no effect on TGFβ1 secretion and consequent inhibition of hematopoiesis by them, showing that secretion of TGFβ1 by adipocytes is independent of NRP1 expression by them. Surprisingly, mesenchymal stromal cells modified with NRP1 supported expansion of HSPCs having enhanced functionality, suggesting that NRP1 exerts a context-dependent effect on hematopoiesis. Our data demonstrate that NRP1 is an important niche component and exerts c

Evidence level

Evidence from laboratory and animal studies provides groundwork for understanding mechanisms and potential before human studies continue.

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