Improvement of multilineage hematopoiesis in hematopoietic stem cell-transferred c-kit mutant NOG-EXL humanized mice.

Human hematopoietic stem cell (HSC)-transferred humanized mice are valuable models for exploring human hematology and immunology. However, sufficient recapitulation of human hematopoiesis in mice requires large quantities of enriched human CD34+ HSCs and total-body irradiation for adequate engraftment. Recently, we generated a NOG mouse strain with a point mutation in the c-kit tyrosine kinase domain (W41 mutant; NOGW mice). In this study, we examined the ability of NOGW mice to reconstitute human hematopoietic cells. Irradiated NOGW mice exhibited high engraftment levels of human CD45+ cells in the peripheral blood, even when only 5,000-10,000 CD34+ HSCs were transferred. Efficient engraftment of human CD45+ cells was also observed in non-irradiated NOGW mice transferred with 20,000-40,000 HSCs. The bone marrow (BM) of NOGW mice exhibited significantly more engrafted human HSCs or progenitor cells (CD34+CD38- or CD34+CD38+ cells) than the BM of NOG mice. Furthermore, we generated a human cytokine (interleukin-3 and granulocyte-macrophage colony-stimulating factor) transgenic NOG-W41 (NOGW-EXL) mouse to achieve multilineage reconstitution with sufficient engraftment of human hematopoietic cells. Non-irradiated NOGW-EXL mice showed significantly higher engraftment levels of human CD45+ and myeloid lineage cells, particularly granulocytes and platelets/megakaryocytes, than non-irradiated NOGW or irradiated NOG-EXL mice after human CD34+ cell transplantation. Serial BM transplantation experiments revealed that NOGW mice exhibited the highest potential for long-term HSC compared with other strains. Consequently, c-kit mutant NOGW-EXL humanized mice represent an advanced model for HSC-transferred humanized mice and hold promise for widespread applications owing to their high versatility.

Platelets constitutively express IL-33 protein and modulate eosinophilic airway inflammation.

BACKGROUND: Although platelets play a key role in allergic inflammation in addition to their well-established role in hemostasis, the precise mechanisms of how platelets modulate allergic inflammation are not fully understood. IL-33 is an essential regulator of innate immune responses and allergic inflammation. OBJECTIVE: We sought to determine the expression of IL-33 protein by platelets and its functional significance in airway inflammation. METHODS: IL-33 protein in human platelets, the human megakaryocyte cell line MEG-01, and bone marrow-derived mouse megakaryocytes was detected by using Western blot analysis and fluorescent immunostaining. We examined the functional relevance of IL-33 protein in platelets by comparing platelet-intact and platelet-depleted groups in a murine model of IL-33-dependent airway eosinophilia elicited by intranasal administration of papain. We further compared the additive effect of administration of platelets derived from wild-type versus IL-33-deficient mice on the papain-induced eosinophilia. RESULTS: Platelets and their progenitor cells, megakaryocytes, constitutively expressed IL-33 protein (31 kDa). Papain-induced IL-33-dependent airway eosinophilia in mice was significantly attenuated by platelet depletion. Conversely, concomitant administration of platelets derived from wild-type mice but not IL-33-deficient mice enhanced the papain-induced airway eosinophilia. CONCLUSIONS: Our novel findings suggest that platelets might be important cellular sources of IL-33 protein in vivo and that platelet-derived IL-33 might play a role in airway inflammation. Therefore platelets might become an attractive novel therapeutic target for asthma and probably allergic inflammation.

Recent advances in understanding the roles of vascular endothelial cells in allergic inflammation.

Allergic disorders commonly involve both chronic tissue inflammation and remodeling caused by immunological reactions to various antigens on tissue surfaces. Due to their anatomical location, vascular endothelial cells are the final responders to interact with various exogenous factors that come into contact with the epithelial surface, such as pathogen-associated molecular patterns (PAMPs) and antigens. Recent studies have shed light on the important roles of endothelial cells in the development and exacerbation of allergic disorders. For instance, endothelial cells have the greatest potential to produce several key molecules that are deeply involved in allergic inflammation, such as periostin and thymus and activation-regulated chemokine (TARC/CCL17). Additionally, endothelial cells were recently shown to be important functional targets for IL-33--an essential regulator of allergic inflammation. Notably, almost all endothelial cell responses and functions involved in allergic inflammation are not suppressed by corticosteroids. These corticosteroid-refractory endothelial cell responses and functions include TNF-α-associated angiogenesis, leukocyte adhesion, IL-33-mediated responses and periostin and TARC production. Therefore, these unique responses and functions of endothelial cells may be critically involved in the pathogenesis of various allergic disorders, especially their refractory processes. Here, we review recent studies, including ours, which have elucidated previously unknown pathophysiological roles of vascular endothelial cells in allergic inflammation and discuss the possibility of endothelium-targeted therapy for allergic disorders.