Osteocytes are the most abundant (90-95%) cells in bone and have emerged as an important regulator of hematopoiesis, but their role in neutrophil development and the underlying mechanisms remain unclear.… Click to show full abstract
Osteocytes are the most abundant (90-95%) cells in bone and have emerged as an important regulator of hematopoiesis, but their role in neutrophil development and the underlying mechanisms remain unclear. Interleukin (IL)-19 produced predominantly by osteocytes stimulated granulopoiesis and neutrophil formation, which stimulated IL-19 receptor (IL-20Rb)/Stat3 signaling in neutrophil progenitors to promote their expansion and neutrophil formation. Mice with constitutive activation of the mechanistic target of rapamycin complex (mTORC1) signaling in osteocytes (Dmp1-Cre) exhibited a dramatic increase in IL-19 production and promyelocytes/myelocytic expansion, while mTORC1 inactivation in osteocytes reduced IL-19 production and neutrophil number in mice. We showed that IL-19 administration stimulated neutrophil development, while neutralizing endogenous IL-19 or depletion of its receptor inhibited the process. Importantly, low dose IL-19 reversed chemotherapy, irradiation, or chloramphenicol-induced neutropenia in mice more efficiently than G-CSF. These evidence indicated that IL-19 was an essential regulator of neutrophil development and a potent cytokine for neutropenia treatment.
               
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