Normal neutrophil maturation is associated with selective loss of MAP kinase activation by G-CSF

SIRT1-SIRT7 Expression in Patients with Lymphoproliferative Disorders Undergoing Hematopoietic Stem Cell Mobilization

Sirtuins are involved in the fate of hematopoietic stem cells (HSCs), including their metabolism, stress response, differentiation, migration, and apoptosis. The aim of this study was to explore SIRT1-7 expression during HSC mobilization. The study included 50 patients with lymphoproliferative disorders (39 multiple myeloma, 11 lymphoma). Samples were taken before mobilization (day 0) and on the day of first apheresis (day A). The sirtuin expression was evaluated by the Droplet Digital PCR (ddPCR) method. A significant increase of the SIRT1, SIRT2, SIRT3, SIRT5, SIRT6, and SIRT7 levels measured at day A as compared to baseline was observed. The study revealed a positive correlation between SIRT5, SIRT6, and SIRT7 expression and the CD34+ peak value in peripheral blood and the number of CD34+ cells collected on day A. Patients from the SIRT7 “high expressors” group collected more CD34+ cells on day A than “low expressors”. Upregulated expressions of SIRT3 and SIRT7 on the day of first apheresis were observed in patients in complete remission status (CR) as compared to the non-CR group. Our results suggest that the investigated sirtuins may influence the HSC migration and hematopoietic landscape during mobilization. SIRT5, SIRT6, and SIRT7 may be associated with the efficacy of HSC mobilization.

Shp1 function in myeloid cells

The motheaten mouse was first described in 1975 as a model of systemic inflammation and autoimmunity, as a result of immune system dysregulation. The phenotype was later ascribed to mutations in the cytoplasmic tyrosine phosphatase Shp1. This phosphatase is expressed widely throughout the hematopoietic system and has been shown to impact a multitude of cell signaling pathways. The determination of which cell types contribute to the different aspects of the phenotype caused by global Shp1 loss or mutation and which pathways within these cell types are regulated by Shp1 is important to further our understanding of immune system regulation. In this review, we focus on the role of Shp1 in myeloid cells and how its dysregulation affects immune function, which can impact human disease.

Differentiation of induced pluripotent stem cell-derived neutrophil granulocytes from common marmoset monkey (Callithrix jacchus)

BACKGROUND

Inherited and acquired marrow failure syndromes most commonly lead to defect in myeloid and/or neutrophil differentiation and/or function. Besides this, neutropenia induced by cancer-adjusted chemotherapy is a frequent clinical problem. In both cases, cell replacement therapy is a well-established, but due to necessity of donors limited and perilous procedure. Therefore, autologous cell replacement from patients' own marrow-derived cells lowers risk and bares new possibilities for therapy. Since the immune system of the marmoset monkey is known to show high similarity to humans, preclinical studies with these animals bare high hopes for immunologic research and cell replacement therapy.

STUDY DESIGN AND METHODS

Marmoset-induced pluripotent stem (iPS) cells (cj-iPSC) were first cultivated on mouse embryonic feeder cells in medium containing recombinant human vascular endothelial growth factor. After 13 days, CD34+/vascular endothelial growth factor receptor-2 (VEGFR2)- cells were sorted, treated with interleukin (IL-3), thrombopoietin, and stem cell factor for 20 days and further cultivated with granulocyte-colony-stimulating factor (G-CSF) and IL-3 for 10 days.

RESULTS

CD34+/VEGFR2- cells could be generated in high amounts (39.65 ± 6.01%; 2.31 × 10⁵ cells). Afterward, these hematopoietic progenitors could be successfully differentiated into mature cj-iPSC-derived neutrophils showing similar morphology, specific surface antigens, and neutrophil-specific gene products and in vitro phagocytic activity.

CONCLUSION

cj-iPSC-derived neutrophils bare high hopes in hematologic cell replacement therapy. They exhibit high morphologic similarity to native neutrophils and present neutrophil-specific surface antigens, antimicrobial proteins, and gene products yielding an auspicious approach for continuative experiments including tests in living animals.

Orientation-specific signalling by thrombopoietin receptor dimers

Ligand binding to the thrombopoietin receptor is thought to stabilize an active receptor dimer that regulates megakaryocyte differentiation and platelet formation, as well as haematopoietic stem cell renewal. By fusing a dimeric coiled coil in all seven possible orientations to the thrombopoietin receptor transmembrane (TM)-cytoplasmic domains, we show that specific biological effects and in vivo phenotypes are imparted by distinct dimeric orientations, which can be visualized by cysteine mutagenesis and crosslinking. Using functional assays and computational searches, we identify one orientation that represents the inactive dimeric state and another similar to a physiologically activated receptor. Several other dimeric orientations are identified that induce proliferation and in vivo myeloproliferative and myelodysplastic disorders, indicating the receptor can signal from several dimeric interfaces. The set of dimeric thrombopoietin receptors with different TM orientations may offer new insights into the activation of distinct signalling pathways by a single receptor and suggests that subtle differences in cytokine receptor dimerization provide a new layer of signalling regulation that is relevant for disease.

Ligation of CD200R by CD200 is not required for normal murine myelopoiesis

CD200R is an inhibitory receptor involved in the regulation of myeloid cells. It recruits Dok-1 and Dok-2, which are potent inhibitors of the Ras signalling pathway used by colony-stimulating factor (CSF) receptors. Dok-1/Dok-2 double knockout (DKO) mice develop leukaemia at 10-12 months of age. We investigated whether disturbed CD200R signalling could be responsible for this phenotype. Therefore, we studied whether CD200(-/-) mice have altered myelopoiesis and develop leukaemia. We report that CD200R is expressed on haematopoietic progenitor cells. However, CD200(-/-) mice have normal numbers of myeloid progenitors in the bone marrow and these cells have normal proliferative capacity. These results indicate that the development of leukaemia in Dok-1/Dok-2 DKO mice is not solely due to an absence of CD200R signalling. In addition, we show that the previously reported enhanced numbers of myeloid cells do not occur in all CD200(-/-) mice. We determined whether variations in the numbers of peripheral myeloid cells were due to an enhanced response to granulocyte-CSF (G-CSF) or an inflammatory stimulus. Mobilisation of immature neutrophils via G-CSF and infiltration of mature neutrophils and macrophages upon thioglycolate injection were not altered in CD200(-/-) mice. We conclude that CD200(-/-) mice exhibit normal myelopoiesis and that development of leukaemia in Dok-1/Dok-2 DKO mice is not caused by a lack of CD200-mediated CD200R signalling.

Impairment of SHP-1 down-regulation in the lipid rafts of human neutrophils under GM-CSF stimulation contributes to their age-related, altered functions

It has been shown that the functions and the rescue from apoptosis by proinflammatory mediators of polymorphonuclear leukocytes (PMN) tend to diminish with aging. Here, we investigated the role of protein tyrosine phosphatases (PTP), especially Src homology domain-containing protein tyrosine phosphatase-1 (SHP-1), in the age-related, altered PMN functions under granulocyte macrophage-colony stimulating factor (GM-CSF) stimulation. The inhibition of PTP suggested a differential effect of GM-CSF on phosphatase activity in modulating PMN functions with aging. The down-regulation of phosphatase activity of immunopurified SHP-1 from lipid rafts of PMN of young donors was found significantly altered at 1 min of stimulation with aging. In young donors, SHP-1 is displaced from lipid rafts at 1 min of stimulation, whereas in the elderly, SHP-1 is constantly present. We assessed in PMN lipid rafts the phosphorylation of tyrosine and serine residues of SHP-1, which regulates its activity. We observed an alteration in the phosphorylation of tyrosine and serine residues of SHP-1 in PMN of elderly subjects, suggesting that GM-CSF was unable to inhibit SHP-1 activity by serine phosphorylation. GM-CSF activates Lyn rapidly, and we found alterations in its activation and translocation to the lipid rafts with aging. We also demonstrate that SHP-1 in the PMN of elderly is constantly recruited to Lyn, which cannot be relieved by GM-CSF. In contrast, in the young, the resting recruitment could be relieved by GM-CSF. Our results suggest an alteration of the SHP-1 modulation by GM-CSF in lipid rafts of PMN with aging. These alterations could contribute to the decreased GM-CSF effects on PMN.