Hematopoietic stem cells (HSCs) balance self-renewal and differentiation to maintain homeostasis. With aging, the frequency of polar HSCs decreases. Cell polarity in HSCs is controlled by the activity of the small RhoGTPase cell division control protein 42 (Cdc42). Here we demonstrate—using a comprehensive set of paired daughter cell analyses that include single-cell 3D confocal imaging, single-cell transplants, single-cell RNA-seq, and single-cell transposase-accessible chromatin sequencing (ATAC-seq)—that the outcome of HSC divisions is strongly linked to the polarity status before mitosis, which is in turn determined by the level of the activity Cdc42 in stem cells. Aged apolar HSCs undergo preferentially self-renewing symmetric divisions, resulting in daughter stem cells with reduced regenerative capacity and lymphoid potential, while young polar HSCs undergo preferentially asymmetric divisions. Mathematical modeling in combination with experimental data implies a mechanistic role of the asymmetric sorting of Cdc42 in determining the potential of daughter cells via epigenetic mechanisms. Therefore, molecules that control HSC polarity might serve as modulators of the mode of stem cell division regulating the potential of daughter cells.

Human plasmacytoid dendritic cells (pDCs) are crucially involved in the modulation of adaptive T-cell responses in the course of neoplastic, viral, and autoimmune disorders. In several of these diseases elevated extracellular levels of the serine protease granzyme B (GrB) are observed. Here we demonstrate that human pDCs can be an abundant source of GrB and that such GrB ؉ pDCs potently suppress T-cell proliferation in a GrBdependent, perforin-independent manner, a process reminiscent of regulatory T cells. Moreover, we show that GrB expression is strictly regulated on a transcriptional level involving Janus kinase 1 (JAK1), signal transducer and activator of transcription 3 (STAT3), and STAT5 and that interleukin-3 (IL-3), a cytokine secreted by activated T cells, plays a central role for GrB induction. Moreover, we find that the immunosuppressive cytokine IL-10 enhances, while Toll-like receptor agonists and CD40 ligand strongly IntroductionPlasmacytoid dendritic cells (pDCs) represent a central link between innate and adaptive immunity and play a crucial role in viral, autoimmune, and neoplastic diseases. [1][2][3][4] One of their most prominent features is the ability of pDCs to produce and secrete large amounts of type I interferons (IFNs), thereby initiating and orchestrating antiviral immune responses. 1,5 pDCs can also function as antigen-presenting cells and stimulate effector T-cell responses. 6 However, pDC effects on T-cell subsets can include both T-cell activation (immunogenic function) 7 and induction of T-cell anergy (tolerogenic function). 7,8 pDCs therefore play an important role in fine-tuning cellular immune responses depending on the microenvironment. Several studies suggest that both the activated T cell-derived cytokine interleukin-3 (IL-3) 9 and the immunosuppressive cytokine IL-10 induce a rather tolerogenic pDC phenotype associated with suppression of T-cell responses. [10][11][12] In contrast, activation of pDCs in the presence of ligands for the pDC-characteristic Toll-like receptors (TLRs) TLR7 and TLR9 1 and for CD40 10 results in an immunogenic phenotype with such pDC triggering a proinflammatory immune response including T-cell activation and cytotoxicity. 6,13,14 Several inflammatory diseases including viral and autoimmune diseases have been found to be associated with elevated levels of extracellular granzyme B (GrB). Granzymes including GrB have been found to be locally elevated in bronchoalveolar lavage fluid from patients with chronic allergic asthma and in synovial fluid from patients with rheumatoid arthritis. 15 Infections with cytomegalovirus after renal transplantation, with the dengue fever virus or with HIV, have been associated with high serum levels of GrB. 15 Granzymes such as GrB represent a major constituent of the granules of cytotoxic cells, including cytotoxic T lymphocyte (CTL) and natural killer (NK) cells. The classical function of GrB is induction of apoptosis in target cells recognized by CTLs. 16,17 Evidence is growing that apart from its cytotoxic effec...

With ageing, intrinsic haematopoietic stem cell (HSC) activity decreases, resulting in impaired tissue homeostasis, reduced engraftment following transplantation and increased susceptibility to diseases. However, whether ageing also affects the HSC niche, and thereby impairs its capacity to support HSC function, is still widely debated. Here, by using in-vivo long-term labelretention assays we demonstrate that aged label-retaining HSCs, which are, in old mice, the most quiescent HSC subpopulation with the highest regenerative capacity and cellular polarity, reside predominantly in perisinusoidal niches. Furthermore, we demonstrate that sinusoidal niches are uniquely preserved in shape, morphology and number on ageing. Finally, we show that myeloablative chemotherapy can selectively disrupt aged sinusoidal niches in the long term, which is linked to the lack of recovery of endothelial Jag2 at sinusoids. Overall, our data characterize the functional alterations of the aged HSC niche and unveil that perisinusoidal niches are uniquely preserved and thereby protect HSCs from ageing.

Many interferometry-based quantitative phase contrast imaging techniques require a separately generated coherent reference wave. This results in a low phase stability and the demand for a precise adjustment of the intensity ratio between object and reference wave. To overcome these problems, the performance of a Michelson interferometer approach for digital holographic microscopy was analyzed that avoids a separately generated reference wave by superposition of different image areas. It is shown that this simplified arrangement yields improved phase stability. Furthermore, results from time-lapse investigations on living pancreas tumor cells demonstrate the capability of the method for reliable quantitative phase contrast imaging.

Digital holographic microscopy (DHM) enables quantitative multifocus phase contrast imaging for nondestructive technical inspection and live cell analysis. Time-lapse investigations on human brain microvascular endothelial cells demonstrate the use of DHM for label-free dynamic quantitative monitoring of cell division of mother cells into daughter cells. Cytokinetic DHM analysis provides future applications in toxicology and cancer research.

BackgroundThe decline of hematopoietic stem cell (HSC) function upon aging contributes to aging-associated immune remodeling and leukemia pathogenesis. Aged HSCs show changes to their epigenome, such as alterations in DNA methylation and histone methylation and acetylation landscapes. We previously showed a correlation between high Cdc42 activity in aged HSCs and the loss of intranuclear epigenetic polarity, or epipolarity, as indicated by the specific distribution of H4K16ac.ResultsHere, we show that not all histone modifications display a polar localization and that a reduction in H4K16ac amount and loss of epipolarity are specific to aged HSCs. Increasing the levels of H4K16ac is not sufficient to restore polarity in aged HSCs and the restoration of HSC function. The changes in H4K16ac upon aging and rejuvenation of HSCs are correlated with a change in chromosome 11 architecture and alterations in nuclear volume and shape. Surprisingly, by taking advantage of knockout mouse models, we demonstrate that increased Cdc42 activity levels correlate with the repression of the nuclear envelope protein LaminA/C, which controls chromosome 11 distribution, H4K16ac polarity, and nuclear volume and shape in aged HSCs.ConclusionsCollectively, our data show that chromatin architecture changes in aged stem cells are reversible by decreasing the levels of Cdc42 activity, revealing an unanticipated way to pharmacologically target LaminA/C expression and revert alterations of the epigenetic architecture in aged HSCs.Electronic supplementary materialThe online version of this article (10.1186/s13059-018-1557-3) contains supplementary material, which is available to authorized users.

Digital holographic microscopy (DHM) enables a quantitative multifocus phase contrast imaging that has been found suitable for technical inspection and quantitative live cell imaging. The combination of DHM with fast and robust autofocus algorithms enables subsequent automated focus realignment by numerical propagation of the digital holographically reconstructed object wave. In combination with a calibrated optical imaging system, the obtained propagation data quantify axial displacements of the investigated sample. The evaluation of quantitative DHM phase contrast images also enables an effective determination of lateral cell displacements. Thus, 3-D displacement data are provided. Results from investigations on sedimenting red blood cells and HT-1080 fibrosarcoma cells in a collagen tissue model demonstrate that DHM enables marker-free automated quantitative dynamic 3-D cell tracking without mechanical focus adjustment.

Plasmacytoid dendritic cell (PDC)-derived IFN-α plays a central role in antiviral defense and in Th1-driven autoimmune diseases, such as systemic lupus erythematosus (SLE). In the current study, we explored how PGE2 effects the phenotype of PDCs from healthy and SLE subjects. Although PGE2 is considered to mediate mainly proinflammatory effects, we show that PGE2 and PG analogs potently inhibit secretion of IFN-α by TLR-activated PDCs. This effect is mainly mediated by PG receptors E-prostanoid 2 and E-prostanoid 4 and involves inhibition of IFN regulatory factor 7 expression. Of note, profound IFN-α inhibition by PGE2 is also seen in PDCs from SLE subjects, independent of age, disease activity, and therapy. We show that TLR9-activated PDCs treated with PGE2 exhibit DC2-like characteristics with enhanced expression of CD86 and CD62L, and decreased expression of CD80 and MHC class I. Consequently, PGE2-treated PDCs suppress secretion of Th1 cytokines by T cells while increasing the secretion of Th2 cytokines. Prevention of CpG-induced CD62L downregulation by PGE2 suggests that it may induce the retreat of PDCs from inflamed tissues. Our data on the effects of PGE2 on PDCs may explain occasional reports about the induction of SLE-like symptoms by cyclooxygenase inhibitors as well as improvement of such symptoms by treatment with PG analogs. In conclusion, our data suggest that PGE2 and certain PG analogs, some of which are already in clinical use, should be evaluated as a novel and inexpensive treatment approach for patients with SLE and other IFN-α–dependent, Th1-driven autoimmune diseases.