Engel, D. R. | bioRxiv Science

bioRxiv2019

Relocation of macrophages maintains the barrier function of the urothelium and protects against persistent infection

Macrophages perform essential functions during bacterial infections, such as phagocytosis of pathogens and elimination of neutrophils to reduce spreading of infection, inflammation and tissue damage. The spatial distribution of macrophages is critical to respond to tissue specific adaptations upon infections. Using a novel algorithm for correlative mass spectrometry imaging and state-of-the-art multiplex microscopy, we report here that macrophages within the urinary bladder are positioned in the connective tissue underneath the urothelium. Invading uropathogenic E.coli induced an IL-6-dependent CX3CL1 expression by urothelial cells, facilitating relocation of macrophages from the connective tissue into the urothelium. These cells phagocytosed UPECs and eliminated neutrophils to maintain barrier function of the urothelium, preventing persistent and recurrent urinary tract infection. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY GRAPHICAL ABSTRACT C_FIG_DISPLAY

immunology↗

bioRxiv2019

Dose-dependent role of Gfi1 in murine hematopoietic stem cell self-renewal and differentiation

Gfi1 (Growth factor independence 1) is a transcription factor that influences the stem cell capacity of hematopoietic stem cells (HSCs) as well as their differentiation into the myeloid and lymphoid lineage. Loss of Gfi1 impedes the repopulation capacity of HSCs and leads to a block in granulocyte generation causing severe neutropenia and monocytosis. Competitive transplantation assays showed that Gfi1-deficient cells were not able to reconstitute myeloid and lymphoid hematopoiesis in competition with Gfi1-wildtype (GFI1-36S) cells. Low Gfi1 levels (GFI1-knockdown = GFI1-KD) in blasts of myelodysplastic neoplasms, acute and chronic myeloid leukemia patients are associated with poor patient survival. To understand how reduced levels or loss of Gfi1 contribute to hematopoiesis, we analyzed the effect of GFI1-KD and Gfi1-KO on HSCs and more mature cell types in mice. GFI1-KD and Gfi1-KO led to strong decrease in HSC numbers, while the numbers of early progenitors (Lin- Sca1+cKit+ cells) were slightly increased. Competitive transplantation assays showed that GFI1-KD and Gfi1-KO HSCs can still engraft and expand, but they cannot contribute to myeloid and lymphoid differentiation.

molecular biology↗