Kavita Bisht

Biomanufactured cell therapies are delivering a step-change in modern medicine, but their high costs have prevented widespread adoption. Cultured red blood cells (cRBCs) are one type of cell therapy in clinical trials for off-the-shelf blood transfusion but remain limited by the exorbitant costs of manufacturing trillions of RBCs required for a blood transfusion. These costs could be mitigated if culture platforms could grow cells at higher density, like those found in the bone marrow, requiring less media and lower concentrations of expensive growth factors per cell. We engineered melt electrowritten (MEW) polycaprolactone (PCL) scaffolds in geometries which imitate marrow trabeculae structures and were then plasma-treated to enable peripheral blood mononuclear cells (PB MNC) attachment. PB MNC monocytes first adhered to the scaffold and rapidly differentiated into CD68 ⁺ macrophage-like cells. These macrophage-loaded scaffolds adhered CD71 ⁺ erythroblasts, which then grew from 10 to 25% between days 4 and 8 and produced CD235a ⁺ erythroid cells by day 20, under erythrogenic culture conditions. MEW PCL scaffolds in trabecular-like geometries had greater surface area, adhered more macrophages, and generated more erythroblasts than traditional MEW crosshatch geometries. The MEW scaffolds continuously released less-adherent cells to the supernatant, providing a 74% increase in supernatant cell numbers versus liquid suspension controls with identical cell seeding numbers and media volumes. High-cell-density scaffolds exhibited increased metabolism and endogenous production of self-supportive cytokines, which may offer cost-saving opportunities through future media optimisation. This study reports marrow trabeculae-mimetic MEW PCL designs capable of selectively adhering PB MN cells to develop macrophage-coated scaffolds, which provided physical and paracrine support for cRBC production. This high-cell-density culture platform may be useful for future cell therapy biomanufacturing protocols.

Anemia is one of the most debilitating and frequent complications of inflammatory bowel diseases (IBD) and is often treated with iron supplementation, which has limited efficacy. Damaged intestinal barrier function is a hallmark of IBD and causes the translocation of endotoxins from gut bacteria into the bloodstream. In a previous study in mice, we reported that endotoxin suppresses erythropoiesis by reprogramming erythroblastic island macrophages (EBI Mφ). Here, we show that IBD patients and mice with acute colitis developed endotoxemia associated with anemia. Endotoxemia in IBD patients was negatively correlated with blood erythrocyte counts. In line with this, mice with acute colitis caused by drinking water containing dextrin sodium sulphate (DSS) had endotoxemia together with anemia characterized by reduced red blood cell counts, hemoglobin content and hematocrit., and reduced medullary erythropoiesis which was in part compensated by increased extramedullary erythropoiesis. As the endotoxin receptor TLR4 is expressed by CD169 ⁺ gut-resident macrophages and erythroid island macrophages in the bone marrow, we tested the hypothesis that TLR4 expressed by these CD169 ⁺ macrophages mediate both inflammatory colitis and anemia. Indeed, mice with conditional deletion of the Tlr4 gene specifically in CD169 ⁺ tissue-resident macrophages were protected from DSS-induced anemia and colitis. In addition, treatment of DSS mice with the TLR4 inhibitor C34 abated inflammation and anemia. These results suggest that endotoxins leaking from the inflamed gut may play a crucial role in IBD and associated anemia and that drugs targeting TLR4 may protect against IBD-associated anemia. Key points: Patients with IBD and mice with acute colitis are anemic with increased endotoxemia and inflammation. Endotoxemia is inversely correlated with blood erythrocyte counts in IBD patients. Conditional deletion of endotoxin receptor gene Tlr4 specifically in CD169 ⁺ tissue-resident macrophages or administration of synthetic TLR4 inhibitor significantly reduced colitis-induced anemia in mice.

Objectives: Histone deacetylase 7 (HDAC7), a classical HDAC family member, promotes LPS-inducible glycolysis and inflammatory mediator production in macrophages, innate immune cells that contribute to pathology in metabolic diseases. Here, we investigated myeloid HDAC7 functions in obesity-driven metabolic disease. Methods: We used gain- and loss-of-function genetic approaches in mice to investigate myeloid HDAC7 functions in hepatic inflammation and metabolic disease, as well as associations with hepatic gene signatures characteristic of advanced chronic liver disease (CLD). Results: Transgenic expression of Hdac7 in myeloid cells increased liver inflammation and liver mRNA levels of Ccl2 and Il1b , key inflammatory mediators linked to CLD. Liver glycogen levels were also decreased, another feature of CLD. Transgenic expression of Hdac7 in myeloid cells mimicked the hepatic inflammatory phenotype that was observed in mice fed a high fat, high cholesterol, and high sucrose (HFHCHS) diet, an obesity model that mimics some features of metabolic dysfunction-associated steatotic liver disease. In myeloid Hdac7 transgenic mice fed a HFHCHS diet, relative weight gain was increased, fasted glucose levels were elevated and glucose tolerance was dysregulated by comparison to control mice. Conversely, fasted blood glucose levels were reduced and glucose tolerance was improved in myeloid Hdac7 -deleted mice on a HFHCHS diet. HDAC7 mRNA levels were also elevated in the livers of people with advanced CLD and spatial transcriptomics revealed that myeloid HDAC7 directs hepatic gene signatures characteristic of advanced CLD. Conclusions: Myeloid HDAC7 contributes to hepatic inflammation and systemic glucose dysregulation in a mouse model of obesity and liver inflammation.

Stem cell antigen-1 (SCA1) is widely used to identify mouse hematopoietic stem cells (HSC) and multipotent progenitors (MPP) among lineage-negative KIT ⁺ (LK) cells. However, SCA1 is expressed only in a few inbred mouse strains and becomes strongly upregulated on LK cells following in vivo challenge with interferons, lipopolysaccharide (LPS) or pathogens leading to incorrect analysis of HSC function subsets and delineation of HSC, MPP and lineage-restricted progenitor subsets. Endothelial protein C receptor CD201can be used as an alternative marker for mouse and even human HSC. However, whether CD201 expression changes following infectious challenge is unknown. Unlike SCA1, CD201 expression did not change on mouse LK cells in response to LPS in vivo. Long-term competitive transplantations with CD201 ⁺ , CD201 ⁻ or SCA1 ⁺ LK cells showed that most reconstituting HSCs are within the LK CD201 ⁺ population after LPS challenge. However long-term competitive repopulation potential of LK SCA1 ⁺ cells from LPS-treated mice was much more severely reduced than that of LK CD201 ⁺ cells from the same LPS-treated donors suggesting that the LK SCA1 ⁺ population in challenged donors becomes contaminated with CD201 ⁻ progenitors devoid of long-term repopulation potential. Based on CD201 gating strategy, we re-assessed the effect of LPS on HSC and MPP cycling and mobilization, and their dependency on MY88 and TRIF adaptors. In conclusion, CD201 enables a more accurate analysis of mouse HSC and MPP subsets in all inbred strains in septic conditions or steady-state. Highlights: SCA1 expression is markedly enhanced on MPPs and myeloid progenitors in vivo following LPS treatment whereas CD201 expression is not. Over 90% of the long-term competitive repopulation potential resides within LK CD201+ cells after LPS treatment. LK CD201+ cells sorted from LPS-treated mice give 4.4-fold higher multi-lineage chimerism than LK SCA1+ cells. SCA1 upregulation leads to overestimation of LT-HSC and MPP subsets, and underestimation of myeloid progenitors in femoral BM of LPS-treated mice.

We show that pro-inflammatory oncostatin M (OSM) is an important regulator of hematopoietic stem cell (HSC) niches in the bone marrow (BM). Treatment of healthy humans and mice with granulocyte colony-stimulating factor (G-CSF) dramatically increases OSM release in blood and BM. Using mice null for the OSM receptor (OSMR) gene, we demonstrate that OSM provides a negative feed-back acting as a brake on HSPC mobilization in response to clinically relevant mobilizing molecules G-CSF and CXCR4 antagonist. Likewise, injection of a recombinant OSM molecular trap made of OSMR complex extracellular domains enhances HSC mobilization in poor mobilizing C57BL/6 and NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ mice. Mechanistically, OSM attenuates HSC chemotactic response to CXCL12 and increases HSC homing to the BM signaling indirectly via BM endothelial and mesenchymal cells which are the only cells expressing OSMR in the BM. OSM up-regulates E-selectin expression on BM endothelial cells indirectly increasing HSC proliferation. RNA sequencing of HSCs from Osmr^−/− and wild-type mice suggest that HSCs have altered cytoskeleton reorganization, energy usage and cycling in the absence of OSM signaling in niches. Therefore OSM is an important regulator of HSC niche function restraining HSC mobilization and anti-OSM therapy combined with current mobilizing regimens may improve HSPC mobilization for transplantation.

Biliverdin reductase (BVR)-A is a pleotropic enzyme converting biliverdin to bilirubin and a signaling molecule that has cytoprotective and immunomodulatory effects. We recently showed that biliverdin inhibits the expression of complement activation fragment 5a receptor one (C5aR1) in RAW 264.7 macrophages. In this study, we investigated the role of BVR-A in determining macrophage inflammatory phenotype and function via regulation of C5aR1. We assessed expression of C5aR1, M1-like macrophage markers, including chemokines (RANTES, IP-10), as well as chemotaxis in response to LPS and C5a in bone marrow–derived macrophages from BVR^fl/fl and LysM-Cre:BVR^fl/fl mice (conditional deletion of BVR-A in myeloid cells). In response to LPS, macrophages isolated from LysM-Cre:BVR^fl/fl showed significantly elevated levels of C5aR1 as well as chemokines (RANTES, IP10) but not proinflammatory markers, such as iNOS and TNF. An increase in C5aR1 expression was also observed in peritoneal macrophages and several tissues from LysM-Cre:BVR^fl/fl mice in a model of endotoxemia. In addition, knockdown of BVR-A resulted in enhanced macrophage chemotaxis toward C5a. Part of the effects of BVR-A deletion on chemotaxis and RANTES expression were blocked in the presence of a C5aR1 neutralizing Ab, confirming the role of C5a–C5aR1 signaling in mediating the effects of BVR. In summary, BVR-A plays an important role in regulating macrophage chemotaxis in response to C5a via modulation of C5aR1 expression. In addition, macrophages lacking BVR-A are characterized by the expression of M1 polarization–associated chemokines, the levels of which depend in part on C5aR1 signaling. Key points Myeloid-specific conditional deletion of BVR-A results in increased response to LPS. Macrophages isolated from LysM-Cre:BVR^fl/fl showed elevated levels of C5aR1. Deletion of BVR-A resulted in enhanced macrophage chemotaxis toward C5a. BVR-A–modulated chemotaxis and RANTES levels are dependent in part on C5aR1. Visual Abstract

Key Points. VEGFR1/2 kinase inhibitor and neutralizing anti-VEGFR2 antibody block PHD inhibitor FG-4497–mediated increase in HSPC mobilization.The inhibitory ef

Sepsis is a multi-system syndrome that remains the leading cause of mortality and critical illness worldwide, with hemodynamic support being one of the cornerstones of the acute management of sepsis. We used an ovine model of endotoxemic shock to determine if 0.9% saline resuscitation contributes to lung inflammation and injury in acute respiratory distress syndrome, which is a common complication of sepsis, and investigated the potential role of matrix metalloproteinases in this process. Endotoxemic shock was induced in sheep by administration of an escalating dose of lipopolysaccharide, after which they subsequently received either no fluid bolus resuscitation or a 0.9% saline bolus. Lung tissue, bronchoalveolar fluid (BAL) and plasma were analysed by real-time PCR, ELISA, flow cytometry and immunohistochemical staining to assess inflammatory cells, cytokines, hyaluronan and matrix metalloproteinases. Endotoxemia was associated with decreased serum albumin and total protein levels, with activated neutrophils, while the glycocalyx glycosaminoglycan hyaluronan was significantly increased in BAL. Quantitative real-time PCR studies showed higher expression of IL-6 and IL-8 with saline resuscitation but no difference in matrix metalloproteinase expression. BAL and tissue homogenate levels of IL-6, IL-8 and IL-1β were elevated. This data shows that the inflammatory response is enhanced when a host with endotoxemia is resuscitated with saline, with a comparatively higher release of inflammatory cytokines and endothelial/glycocalyx damage, but no change in matrix metalloproteinase levels.