biostudies-literatureKim JWNational Institute of Diabetes and Digestive and Kidney DiseasesNIDDK NIH HHSNHLBI NIH HHSNational Institutes of Health104147https://www.ebi.ac.uk/biostudies/studies/S-EPMC10939783biostudies-literatureUnknown131Hematopoietic stem cell transplantation requires the collection of hematopoietic cells from patients or stem cell donors. Granulocyte colony-stimulating factor (G-CSF) is widely used in the clinic to mobilize hematopoietic stem and progenitor cells (HSPCs) from the adult bone marrow niche into circulation, allowing a collection of HSPCs from the blood. The mechanism by which G-CSF acts to mobilize HSPCs is unclear, with some studies showing a direct stimulation of stem cells and others suggesting that myeloid cells are required. In this study, we developed a heat-inducible G-CSF transgenic zebrafish line to study HSPC mobilization in vivo. Live imaging of HSPCs after G-CSF induction revealed an increase in circulating HSPCs, demonstrating a successful HSPC mobilization. These mobilized HSPCs went on to prematurely colonize the kidney marrow, the adult zebrafish hematopoietic niche. We eliminated neutrophils or macrophages using a nitroreductase-based cell ablation system and found that G-CSF still mobilizes HSPCs from the niche. Our findings indicate that neutrophils and macrophages are not required for G-CSF-induced HSPC mobilization from the embryonic hematopoietic niche.Experimental hematologyG-CSF-induced hematopoietic stem cell mobilization from the embryonic hematopoietic niche does not require neutrophils and macrophages.PMC10939783RC2 DK120535R01 HL048801R01 HL144780P01 HL131477RC2DK120535Fedorov EAZon LIKim JWfalseG-CSF-induced hematopoietic stem cell mobilization from the embryonic hematopoietic niche does not require neutrophils and macrophages.Hematopoietic stem cell transplantation requires the collection of hematopoietic cells from patients or stem cell donors. Granulocyte colony-stimulating factor (G-CSF) is widely used in the clinic to mobilize hematopoietic stem and progenitor cells (HSPCs) from the adult bone marrow niche into circulation, allowing a collection of HSPCs from the blood. The mechanism by which G-CSF acts to mobilize HSPCs is unclear, with some studies showing a direct stimulation of stem cells and others suggesting that myeloid cells are required. In this study, we developed a heat-inducible G-CSF transgenic zebrafish line to study HSPC mobilization in vivo. Live imaging of HSPCs after G-CSF induction revealed an increase in circulating HSPCs, demonstrating a successful HSPC mobilization. These mobilized HSPCs went on to prematurely colonize the kidney marrow, the adult zebrafish hematopoietic niche. We eliminated neutrophils or macrophages using a nitroreductase-based cell ablation system and found that G-CSF still mobilizes HSPCs from the niche. Our findings indicate that neutrophils and macrophages are not required for G-CSF-induced HSPC mobilization from the embryonic hematopoietic niche.2024-01-01T00:00:00Z2024 Mar2025-04-04T01:12:37.579Z2025-04-04T01:12:37.579ZS-EPMC109397833816099410.1016/j.exphem.2023.104147