Murine serum obtained from bone marrow-transplanted mice promotes the proliferation of hematopoietic stem cells by co-culture with MS-5 murine stromal cells

Inhibition of CSF-1R and IL-6R prevents conversion of cDC2s into immune incompetent tumor-induced DC3s boosting DC-driven therapy potential

The human dendritic cell (DC) family has recently been expanded by CD1c+CD14+CD163+ DCs, introduced as DC3s. DC3s are found in tumors and peripheral blood of cancer patients. Here, we report elevated frequencies of CD14+ cDC2s, which restore to normal frequencies after tumor resection, in non-small cell lung cancer patients. These CD14+ cDC2s phenotypically resemble DC3s and exhibit increased PD-L1, MERTK, IL-10, and IDO expression, consistent with inferior T cell activation ability compared with CD14- cDC2s. In melanoma patients undergoing CD1c+ DC vaccinations, increased CD1c+CD14+ DC frequencies correlate with reduced survival. We demonstrate conversion of CD5+/-CD1c+CD14- cDC2s to CD14+ cDC2s by tumor-associated factors, whereas monocytes failed to express CD1c under similar conditions. Targeted proteomics identified IL-6 and M-CSF as dominant drivers, and we show that IL-6R and CSF1R inhibition prevents tumor-induced CD14+ cDC2s. Together, this indicates cDC2s as direct pre-cursors of DC3-like CD1c+CD14+ DCs and provides insights into the importance and modulation of CD14+ DC3s in anti-tumor immune responses.

The gp130 Cytokine Interleukin-11 Regulates Engraftment of Vav1-/- Hematopoietic Stem and Progenitor Cells in Lethally Irradiated Recipients

During bone marrow transplantation, hematopoietic stem and progenitor cells (HSPCs) respond to signals from the hematopoietic microenvironment by coordinately activating molecular pathways through Rho GTPases, including Rac. We have previously shown that deletion of Vav1, a hematopoietic-specific activator of Rac, compromises engraftment of transplanted adult HSPCs without affecting steady-state hematopoiesis in adult animals. Here, we show that Vav1^-/- fetal HSPCs can appropriately seed hematopoietic tissues during ontogeny but cannot engraft into lethally irradiated recipients. We demonstrate that the engraftment defect of Vav1^-/- HSPCs is abrogated in the absence of irradiation and demonstrate that Vav1 is critical for the response of HSPCs to the proinflammatory cytokine interleukin-11 (IL-11) that is upregulated in the marrow of irradiated recipients. Vav1^-/- HSPCs display abnormal proliferative responses to IL-11 in vitro and dysregulated activation of pathways critical to engraftment of HSPCs. The engraftment of Vav1^-/- HSPCs can be partially rescued in irradiated recipients treated with an anti-IL-11 antibody. These data suggest that HSPCs may respond to different functional demands by selective usage of the IL-11-Vav-Rac pathway, contextualizing further the recent view that HSPCs capable of reconstituting the blood system following transplantation might be distinct from those supporting hematopoiesis during homeostatic conditions. Stem Cells 2018; 36:446-457.

Establishment of a sticky, large, oval-shaped thrombocyte cell line from tree frog as an ancestor of mammalian megakaryocytes

Maintenance of blood vessels is important for homeostasis. Many types of cells and cytokines are involved in angiogenesis and blood vessel repair. In mammals, platelets, which are produced from megakaryocytes, play a major role in hemostasis. Other vertebrates have no platelets in their bloodstream. In these animals, thrombocytes aggregate to form a thrombus. Therefore, I established a frog hematopoietic cell line to elucidate the mechanism of hematopoiesis in this species. The frog-derived thrombocytic cell line was established from a long-term bone marrow culture of Hyla japonica and was designated as a frog-derived unique hematopoietic non-adherent (FUHEN) cell line. The FUHEN cells had unique characteristics in that they proliferated in suspension culture without adherence to the culture flask, and the shapes of the FUHEN cells changed drastically to become very large ovals with growth. These cells reached more than 40 µm in length and had multi-lobed nuclei. The FUHEN cells expressed CD41, a specific surface marker of thrombocytes. These results indicated that the FUHEN cells were thrombocytes. Deprivation of divalent ions quickly induced adherence of the cells to the petri dish. This characteristic may be important for hemostasis. Furthermore, some of the FUHEN cells survived at 16 °C for 1 month and re-established proliferation when the cells were moved to 28 °C. Taken together, this new thrombocytic frog cell line, as an ancestor of mammalian megakaryocytes, could provide useful material to study the functions of thrombocytes and the hemostasis mechanism of amphibians.

High level in vitro expansion of murine hematopoietic stem cells

Development of strategies to extensively expand hematopoietic stem cells (HSCs) in vitro will be a major factor in enhancing the success of a range of transplant-based therapies for malignant and genetic disorders. In addition to potential clinical applications, the ability to increase the number of HSCs in culture will facilitate investigations into the mechanisms underlying self-renewal. In this unit, we describe a robust strategy for consistently achieving over 1000-fold net expansion of HSCs in short-term in vitro culture by using novel engineered fusions of the N-terminal domain of nucleoporin 98 (NUP98) and the homeodomain of the hox transcription factor, HOXA10 (so called NUP98-HOXA10hd fusion). We also provide a detailed protocol for monitoring the magnitude of HSC expansion in culture by limiting dilution assay of competitive lympho-myeloid repopulating units (CRU Assay). These procedures provide new possibilities for achieving significant numbers of HSCs in culture, as well as for studying HSCs biochemically and genetically.

Near-maximal expansions of hematopoietic stem cells in culture using NUP98-HOX fusions

OBJECTIVE

Strategies to expand hematopoietic stem cells (HSCs) ex vivo are of key interest. The objective of this study was to resolve if ability of HOXB4, previously documented to induce a significant expansion of HSCs in culture, may extend to other HOX genes and also to further analyze the HOX sequence requirements to achieve this effect.

METHODS

To investigate the ability of Nucleoporin98-Homeobox fusion genes to stimulate HSC self-renewal, we evaluated their presence in 10- to 20-day cultures of transduced mouse bone marrow cells. Stem cell recovery was measured by limiting-dilution assay for long-term competitive repopulating cells (CRU Assay).

RESULTS

These experiments revealed remarkable expansions of Nucleoporin98-Homeobox-transduced HSCs (1000-fold to 10,000-fold over input) in contrast to the expected decline of HSCs in control cultures. Nevertheless, the Nucleoporin98-Homeobox-expanded HSCs displayed no proliferative senescence and retained normal lympho-myeloid differentiation activity and a controlled pool size in vivo. Analysis of proviral integration patterns showed the cells regenerated in vivo were highly polyclonal, indicating they had derived from a large proportion of the initially targeted HSCs. Importantly, these effects were preserved when all HOX sequences flanking the homeodomain were removed, thus defining the homeodomain as a key and independent element in the fusion.

CONCLUSION

These findings create new possibilities for investigating HSCs biochemically and genetically and for achieving clinically significant expansion of human HSCs.