Single-cell genomics in acquired bone marrow failure syndromes.

Mechanistic studies of immune bone marrow failure are difficult because of the scarcity of residual cells, the involvement of multiple cell types, and the inherent complexities of hematopoiesis and immunity. Single-cell genomic technologies and bioinformatics allow extensive, multidimensional analysis of a very limited number of cells. We review emerging applications of single-cell techniques, and early results related to disease pathogenesis: effector and target cell populations and relationships, cell-autonomous and nonautonomous phenotypes in clonal hematopoiesis, transcript splicing, chromosomal abnormalities, and T-cell receptor usage and clonality. Dense and complex data from single-cell techniques provide insights into pathophysiology, natural history, and therapeutic drug effects.

Efficacy of JAK1/2 inhibition in murine immune bone marrow failure.

Immune aplastic anemia (AA) is a severe blood disease characterized by T-lymphocyte- mediated stem cell destruction. Hematopoietic stem cell transplantation and immunosuppression are effective, but they entail costs and risks, and are not always successful. The Janus kinase (JAK) 1/2 inhibitor ruxolitinib (RUX) suppresses cytotoxic T-cell activation and inhibits cytokine production in models of graft-versus-host disease. We tested RUX in murine immune AA for potential therapeutic benefit. After infusion of lymph node (LN) cells mismatched at the major histocompatibility complex [C67BL/6 (B6)⇒CByB6F1], RUX, administered as a food additive (Rux-chow), attenuated bone marrow hypoplasia, ameliorated peripheral blood pancytopenia, preserved hematopoietic progenitors, and prevented mortality, when used either prophylactically or therapeutically. RUX suppressed the infiltration, proliferation, and activation of effector T cells in the bone marrow and mitigated Fas-mediated apoptotic destruction of target hematopoietic cells. Similar effects were obtained when Rux-chow was fed to C.B10 mice in a minor histocompatibility antigen mismatched (B6⇒C.B10) AA model. RUX only modestly suppressed lymphoid and erythroid hematopoiesis in normal and irradiated CByB6F1 mice. Our data support clinical trials of JAK/STAT inhibitors in human AA and other immune bone marrow failure syndromes.

Overlooked Role of Coexistent Hydrogen Peroxide in Activated Peracetic Acid by Cu(II) for Enhanced Oxidation of Organic Contaminants.

Cu(II)-catalyzed peracetic acid (PAA) processes have shown significant potential to remove contaminants in water treatment. Nevertheless, the role of coexistent H2O2 in the transformation from Cu(II) to Cu(I) remained contentious. Herein, with the Cu(II)/PAA process as an example, the respective roles of PAA and H2O2 on the Cu(II)/Cu(I) cycling were comprehensively investigated over the pH range of 7.0-10.5. Contrary to previous studies, it was surprisingly found that the coexistent deprotonated H2O2 (HO2-), instead of PAA, was crucial for accelerating the transformation from Cu(II) to Cu(I) (kHO2-/Cu(II) = (0.17-1) × 106 M-1 s-1, kPAA/Cu(II) < 2.33 ± 0.3 M-1 s-1). Subsequently, the formed Cu(I) preferentially reacted with PAA (kPAA/Cu(I) = (5.84 ± 0.17) × 102 M-1 s-1), rather than H2O2 (kH2O2/Cu(I) = (5.00 ± 0.2) × 101 M-1 s-1), generating reactive species to oxidize organic contaminants. With naproxen as the target pollutant, the proposed synergistic role of H2O2 and PAA was found to be highly dependent on the solution pH with weakly alkaline conditions being more conducive to naproxen degradation. Overall, this study systematically investigated the overlooked but crucial role of coexistent H2O2 in the Cu(II)/PAA process, which might provide valuable insights for better understanding the underlying mechanism in Cu-catalyzed PAA processes.

Constructing Hierarchical Zeolites with Highly Complete Framework via Controlled Desilication.

Desilication in alkaline medium has been widely used in construction of hierarchical zeolites for industrially relevant catalytic processes. The built of hierarchy in zeolites, especially with low aluminum stability or high Si/Al ratio, often suffers from uncontrolled destruction of zeolitic framework, accompanied by a significant loss of microporous domains and intrinsic acidity after desilication. Here, we report a novel and simple methodology for preparation of hierarchical zeolites with highly complete framework and minimum sacrifice of microporosity and acidity. The pre-impregnated amines in zeolite micropores act as inner pore-directing agents (iPDAs), largely protecting the zeolitic framework and moderating the silicon extraction during the alkaline treatment. The resulting hierarchical zeolites exhibit high crystallinity, tunable hierarchy, stable framework, and well-preserved acidity, endowing them with significantly improved mass transport properties and enhanced activities in catalytic conversion of methanol or furfural.

Somatic Mutations in UBA1 and Severe Adult-Onset Autoinflammatory Disease.

BACKGROUND: Adult-onset inflammatory syndromes often manifest with overlapping clinical features. Variants in ubiquitin-related genes, previously implicated in autoinflammatory disease, may define new disorders. METHODS: We analyzed peripheral-blood exome sequence data independent of clinical phenotype and inheritance pattern to identify deleterious mutations in ubiquitin-related genes. Sanger sequencing, immunoblotting, immunohistochemical testing, flow cytometry, and transcriptome and cytokine profiling were performed. CRISPR-Cas9-edited zebrafish were used as an in vivo model to assess gene function. RESULTS: We identified 25 men with somatic mutations affecting methionine-41 (p.Met41) in UBA1, the major E1 enzyme that initiates ubiquitylation. (The gene UBA1 lies on the X chromosome.) In such patients, an often fatal, treatment-refractory inflammatory syndrome develops in late adulthood, with fevers, cytopenias, characteristic vacuoles in myeloid and erythroid precursor cells, dysplastic bone marrow, neutrophilic cutaneous and pulmonary inflammation, chondritis, and vasculitis. Most of these 25 patients met clinical criteria for an inflammatory syndrome (relapsing polychondritis, Sweet's syndrome, polyarteritis nodosa, or giant-cell arteritis) or a hematologic condition (myelodysplastic syndrome or multiple myeloma) or both. Mutations were found in more than half the hematopoietic stem cells, including peripheral-blood myeloid cells but not lymphocytes or fibroblasts. Mutations affecting p.Met41 resulted in loss of the canonical cytoplasmic isoform of UBA1 and in expression of a novel, catalytically impaired isoform initiated at p.Met67. Mutant peripheral-blood cells showed decreased ubiquitylation and activated innate immune pathways. Knockout of the cytoplasmic UBA1 isoform homologue in zebrafish caused systemic inflammation. CONCLUSIONS: Using a genotype-driven approach, we identified a disorder that connects seemingly unrelated adult-onset inflammatory syndromes. We named this disorder the VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. (Funded by the NIH Intramural Research Programs and the EU Horizon 2020 Research and Innovation Program.).

CAISC: A software to integrate copy number variations and single nucleotide mutations for genetic heterogeneity profiling and subclone detection by single-cell RNA sequencing.

BACKGROUND: Although both copy number variations (CNVs) and single nucleotide variations (SNVs) detected by single-cell RNA sequencing (scRNA-seq) are used to study intratumor heterogeneity and detect clonal groups, a software that integrates these two types of data in the same cells is unavailable. RESULTS: We developed Clonal Architecture with Integration of SNV and CNV (CAISC), an R package for scRNA-seq data analysis that clusters single cells into distinct subclones by integrating CNV and SNV genotype matrices using an entropy weighted approach. The performance of CAISC was tested on simulation data and four real datasets, which confirmed its high accuracy in sub-clonal identification and assignment, including subclones which cannot be identified using one type of data alone. Furthermore, integration of SNV and CNV allowed for accurate examination of expression changes between subclones, as demonstrated by the results from trisomy 8 clones of the myelodysplastic syndromes (MDS) dataset. CONCLUSIONS: CAISC is a powerful tool for integration of CNV and SNV data from scRNA-seq to identify clonal clusters with better accuracy than obtained from a single type of data. CAISC allows users to interactively examine clonal assignments.

Development of a Two-Dimensional Liquid Chromatography-Mass Spectrometry Platform for Simultaneous Multi-Attribute Characterization of Adeno-Associated Viruses.

Adeno-associated viruses (AAVs) are non-enveloped, single-stranded DNA viruses that have recently emerged as an attractive vector for delivering genetic materials to hosts for gene therapy applications. Due to their ability to transduce a wide range of species and tissues in vivo, low risk of immunotoxicity, and mild innate and adaptive immune responses, AAVs are currently used in research and clinical studies as a monotherapy or with other biomolecules to perform gene editing, replacement, addition, and silencing. As AAVs are a new and complex therapeutic modality with molecular weights into the megadalton range, new analytical techniques are therefore needed to support process development, product characterization, and release. In this study, an online two-dimensional liquid chromatography-mass spectrometry (2DLC-MS) method was developed for AAV characterization. Our method uses high-resolution anion-exchange chromatography (AEX) in the first dimension to separate and measure empty and full capsids in AAV samples, followed by reversed-phase liquid chromatography coupled with mass spectrometry (RPLC-MS) to separate and characterize viral proteins. In this technique, online denaturation and removal of MS-incompatible salt were performed following AEX. The viral proteins present in the peak of interest after first-dimensional AEX are subjected to intact protein separation on the second-dimensional RPLC column and then characterized by MS. The 2DLC-MS method demonstrated in this study allows for high-throughput and multi-attribute AAV characterization in a single run, with minimal sample handling required for different AAV serotypes.

Sirolimus augments hematopoietic stem and progenitor cell regeneration following hematopoietic insults.

The role of mammalian target of rapamycin and its suppressor sirolimus in the regulation of hematopoietic stem and progenitor cells (HSPCs) is controversial. We show here that sirolimus enhanced regeneration of HSPCs in mice exposed to sublethal total body irradiation (TBI) and other regenerative stressors. Sorted Lin- CD150+ bone marrow cells from sirolimus-treated TBI mice had increased expression of c-Kit and other hematopoietic genes. HSPCs from sirolimus-treated TBI mice were functionally competent when tested by competitive engraftment in vivo. Postradiation regeneration of HSPCs in mice treated with sirolimus was accompanied by decreased γ-H2AX levels detected by flow cytometry and increased expression of DNA repair genes by quantitative polymerase chain reaction. Reduction of cell death and DNA damage post-radiation by sirolimus was associated with enhanced clearance of cellular reactive oxygen species (ROS) in HSPCs. Increased HSPC recovery with sirolimus was also observed in mice injected with hematoxic agents, busulfan and 5-fluorouracil. In contrast, sirolimus showed no effect on HSPCs in normal mice at steady state, but stimulated HSPC expansion in mice carrying the Wv mutation at the c-Kit locus. In human to mouse xenotransplantation, sirolimus enhanced engraftment of irradiated human CD34+ cells. In summary, our results are consistent with sirolimus' acceleration of HSPC recovery in response to hematopoietic stress, associated with reduced DNA damage and ROS. Sirolimus might have clinical application for the treatment and prevention of hematopoietic injury.

Epigenetic silencing and tumor suppressor gene of HAND2 by targeting ERK signaling in colorectal cancer.

BACKGROUND: The screening biomarkers for early detection of colorectal cancer (CRC) is lacking. The aim is to identify epigenetic silenced genes and clarify its roles and underlying mechanism in CRC. We conducted integrative analyses of epigenome-wide Human Methylation 450 K arrays and transcriptome to screen out candidate epigenetic driver genes with transcription silencing. Methylated silencing HAND2 were identified and verified in large CRC cohort. The mechanism of HAND2 expression by promoter inhibition were clarified both in vitro and vivo assays. Cell biofunctional roles of HAND2 methylation was investigated in CRC cells. HAND2 reconstitution were constructed by lentivirus plasmid and tumor xenograft model of HAND2 were built subcutaneously. Genomic mRNA analysis by RNA-sequencing and subsequent GSEA analysis were performed to identify potential target of HAND2 and qPCR/WB was conducted to identify the results. RESULTS: We firstly reported high frequency of HAND2 methylation in promoter in CRC and hypermethylation was negatively correlated with expression silencing and leaded to poor survival in several CRC cohort patients. 5-Aza treatment to demethylated HAND2 could revert its expression in CRC cells. Functionally, HAND2 reconstitution can inhibit cell proliferation, invasion and migration in vitro. In tumor xenograft, HAND2 reconstruction significantly repressed tumor growth when compared to control vector. Thousands of aberrant expressed genes were observed in the heatmap of RNA-sequencing data. HAND2 reconstitution could bind to ERK and reduce its phosphorylation by CoIP assay. These above results showed HAND2 reconstitution perturbed the activation of MAPK/ERK signaling by reduction of ERK phosphorylation. CONCLUSIONS: HAND2 is one tumor suppressor by targeting ERK signaling and one potential epigenetic driver gene in CRC. Video Abstract.

Effects of Etco2 on the Minimum Alveolar Concentration of Sevoflurane that Blunts the Adrenergic Response to Surgical Incision: A Prospective, Randomized, Double-Blinded Trial.

BACKGROUND: CO2 has anesthetic potency and effectively influences the circulatory system. We investigated the effects of Etco2 on the minimum alveolar concentration of sevoflurane that blunts the adrenergic response to surgical incision (MAC-BAR) in patients undergoing radical surgery for gastric carcinoma. METHODS: Ninety patients undergoing radical gastric-carcinoma surgery under general anesthesia were enrolled and randomly assigned into 3 groups. After intubation, the Etco2 in group L (n = 30), group N (n = 30), and group H (n = 30) was adjusted to 25 mm Hg ≤ Etco2 <30 mm Hg, 30 mm Hg ≤ Etco2 < 40 mm Hg, and 40 mm Hg ≤ Etco2 < 45 mm Hg, respectively, by changes in controlled ventilation. Hemodynamics and depth of anesthesia were observed before and after skin incision. The MAC-BAR of sevoflurane for each group was determined using an up-and-down sequential-allocation technique. RESULTS: To obtain 7 crossovers, 25, 26, and 26 patients were used in group L, group N, and group H, respectively. The MAC-BAR of sevoflurane using the up-and-down method for group H was significantly lower than that for group L (2.3% [95% confidence interval {CI}, 2.2-2.4] vs 2.9% [95% CI, 2.7-3.0]; difference, -0.6% [95% CI, -0.7 to -0.4], P < .001) and group N (2.3% [95% CI, 2.2-2.4] vs 2.8% [95% CI, 2.8-2.9]; difference, -0.5% [95% CI, -0.7 to -0.4], P < .001), while no significant difference was found between group L and group N (P = 1.000). CONCLUSIONS: Higher Etco2 levels (Etco2 values equal to 40 mm Hg or higher) can effectively decrease the MAC-BAR of sevoflurane in patients undergoing radical surgery for gastric carcinoma.

Effects of an Intraoperative Intravenous Bolus Dose of Dexmedetomidine on Remifentanil-Induced Postinfusion Hyperalgesia in Patients Undergoing Thyroidectomy: A Double-Blind Randomized Controlled Trial.

BACKGROUND: Consecutive exposure to high-dose remifentanil during anesthesia may induce remifentanil-induced postinfusion hyperalgesia (RPH). Dexmedetomidine, a highly selective α2-adrenergic receptor agonist, may have synergistic effects with opioids and aid in perioperative pain management. In this study, we hypothesized that an intraoperative bolus dose of intravenous dexmedetomidine could alleviate RPH in patients undergoing thyroidectomy under general anesthesia. METHODS: Ninety patients undergoing thyroidectomy were randomly assigned to 1 of 3 groups: placebo, normal saline (group P); low-dose dexmedetomidine 0.2 µg·kg-1 (group LD); or high-dose dexmedetomidine 0.5 µg·kg-1 (group HD). Remifentanil was infused at a rate of 0.30 µg·kg-1·minute-1. Mechanical pain thresholds were measured using an Electronic von Frey device preoperatively and at 30 minutes, 6 hours, 24 hours, and 48 hours after surgery and were analyzed with 2-way repeated-measures analysis of variance (ANOVA) followed by Bonferroni post hoc comparison. We also recorded postoperative pain scores, the incidence of receiving rescue analgesics, and side effects up to 48 hours after surgery. RESULTS: The mechanical pain thresholds around the skin incision were significantly higher in group LD compared to group P 30 minutes and 6 hours after surgery (mean ± standard deviation: [65.0 ± 25.2] vs [49.6 ± 24.4] g, mean difference [95% confidence interval]: 15.4 [0.3-30.5] g, P = .045 at 30 minutes; [65.9 ± 24.5] vs [49.3 ± 26.1] g, 16.6 [1.1-32.1] g, P = .032 at 6 hours). The pain thresholds around the skin incision were significantly higher in group HD compared to group P 30 minutes and 6 hours after surgery ([67.8 ± 21.7] vs [49.6 ± 24.4] g, 18.2 [3.1-33.3] g, P = .013 at 30 minutes; [68.3 ± 22.5] vs [49.3 ± 26.1] g, 19.0 [3.5-34.5] g, P = .011 at 6 hours). The incidence of hyperalgesia around the skin incision was lower in group HD than in group P 30 minutes and 6 hours after surgery (4 [13%] vs 14 [48%], P = .012 at 30 minutes, 4 [13%] vs 12 [41%], P = .045 at 6 hours), although no significant difference was observed between group LD and group P. Postoperative pain scores, the incidence of rescue analgesic demand, and postoperative side effects were not significantly different between the groups. CONCLUSIONS: An intraoperative intravenous bolus dose of dexmedetomidine 0.5 µg·kg-1 alleviates remifentanil-induced hyperalgesia in patients undergoing thyroidectomy without a significant difference in side effects.

Zeolite-Tailored Active Site Proximity for the Efficient Production of Pentanoic Biofuels.

Biofuel production can alleviate reliance on fossil resources and thus carbon dioxide emission. Hydrodeoxygenation (HDO) refers collectively to a series of important biorefinery processes to produce biofuels. Here, well-dispersed and ultra-small Ru metal nanoclusters (ca. 1 nm), confined within the micropores of zeolite Y, provide the required active site intimacy, which significantly boosts the chemoselectivity towards the production of pentanoic biofuels in the direct, one-pot HDO of neat ethyl levulinate. Crucial for improving catalyst stability is the addition of La, which upholds the confined proximity by preventing zeolite lattice deconstruction during catalysis. We have established and extended an understanding of the "intimacy criterion" in catalytic biomass valorization. These findings bring new understanding of HDO reactions over confined proximity sites, leading to potential application for pentanoic biofuels in biomass conversion.

Top-Down Proteomics Reveals Myofilament Proteoform Heterogeneity among Various Rat Skeletal Muscle Tissues.

Heterogeneity in skeletal muscle contraction time, peak power output, and resistance to fatigue, among others, is necessary to accommodate the wide range of functional demands imposed on the body. Underlying this functional heterogeneity are a myriad of differences in the myofilament protein isoform expression and post-translational modifications; yet, characterizing this heterogeneity remains challenging. Herein, we have utilized top-down liquid chromatography (LC)-mass spectrometry (MS)-based proteomics to characterize myofilament proteoform heterogeneity in seven rat skeletal muscle tissues including vastus lateralis, vastus medialis, vastus intermedius, rectus femoris, soleus, gastrocnemius, and plantaris. Top-down proteomics revealed that myofilament proteoforms varied greatly across the seven different rat skeletal muscle tissues. Subsequently, we quantified and characterized myofilament proteoforms using online LC-MS. We have comprehensively characterized the fast and slow skeletal troponin I isoforms, which demonstrates the ability of top-down MS to decipher isoforms with high sequence homology. Taken together, we have shown that top-down proteomics can be used as a robust and high-throughput method to characterize the molecular heterogeneity of myofilament proteoforms from various skeletal muscle tissues.

MASH Explorer: A Universal Software Environment for Top-Down Proteomics.

Top-down mass spectrometry (MS)-based proteomics enable a comprehensive analysis of proteoforms with molecular specificity to achieve a proteome-wide understanding of protein functions. However, the lack of a universal software for top-down proteomics is becoming increasingly recognized as a major barrier, especially for newcomers. Here, we have developed MASH Explorer, a universal, comprehensive, and user-friendly software environment for top-down proteomics. MASH Explorer integrates multiple spectral deconvolution and database search algorithms into a single, universal platform which can process top-down proteomics data from various vendor formats, for the first time. It addresses the urgent need in the rapidly growing top-down proteomics community and is freely available to all users worldwide. With the critical need and tremendous support from the community, we envision that this MASH Explorer software package will play an integral role in advancing top-down proteomics to realize its full potential for biomedical research.

Comprehensive network modeling from single cell RNA sequencing of human and mouse reveals well conserved transcription regulation of hematopoiesis.

BACKGROUND: Presently, there is no comprehensive analysis of the transcription regulation network in hematopoiesis. Comparison of networks arising from gene co-expression across species can facilitate an understanding of the conservation of functional gene modules in hematopoiesis. RESULTS: We used single-cell RNA sequencing to profile bone marrow from human and mouse, and inferred transcription regulatory networks in each species in order to characterize transcriptional programs governing hematopoietic stem cell differentiation. We designed an algorithm for network reconstruction to conduct comparative transcriptomic analysis of hematopoietic gene co-expression and transcription regulation in human and mouse bone marrow cells. Co-expression network connectivity of hematopoiesis-related genes was found to be well conserved between mouse and human. The co-expression network showed "small-world" and "scale-free" architecture. The gene regulatory network formed a hierarchical structure, and hematopoiesis transcription factors localized to the hierarchy's middle level. CONCLUSIONS: Transcriptional regulatory networks are well conserved between human and mouse. The hierarchical organization of transcription factors may provide insights into hematopoietic cell lineage commitment, and to signal processing, cell survival and disease initiation.

Divergent Synthesis of Tunable Cyclopentadienyl Ligands and Their Application in Rh-Catalyzed Enantioselective Synthesis of Isoindolinone.

A series of rhodium complexes bearing sterically and electronically tunable cyclopentadienyl ligands, prepared by utilizing Co2(CO)8-mediated [2+2+1] cyclization as a key step, were synthesized. In the presence of 2.5 mol% of CpmRh4, unprecedented enantioselective [4+1] annulation reaction of benzamides and alkenes was achieved with a broad substrate scope under mild reaction conditions, providing a variety of isoindolinones with excellent regio- and enantioselectivity (up to 94% yield, 97:3 er). Preliminary mechanistic studies suggest that the reaction involves an oxidative Heck reaction and an intramolecular enantioselective alkene hydroamination reaction.

Rapid Analysis of Reduced Antibody Drug Conjugate by Online LC-MS/MS with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Antibody drug conjugates (ADCs), which harness the high targeting specificity of monoclonal antibodies (mAb) with the potency of small molecule therapeutics, are one of the fastest growing pharmaceutical classes. Nevertheless, ADC conjugation techniques and processes may introduce intrinsic heterogeneity including primary sequence variants, varied drug-to-antibody ratio (DAR) species, and drug positional isomers, which must be monitored to ensure the safety and efficacy of ADCs. Liquid chromatography coupled to mass spectrometry (LC-MS) is a powerful tool for characterization of ADCs. However, the conventional bottom-up MS analysis workflows require an enzymatic digestion step which can be time consuming and may introduce artifactual modifications. Herein, we develop an online LC-MS/MS method for rapid analysis of reduced ADCs without digestion, enabling determination of DAR, characterization of the primary sequence, and localization of the drug conjugation site of the ADC using high-resolution Fourier transform ion cyclotron resonance (FTICR) MS. Specifically, a model cysteine-linked ADC was reduced to generate six unique subunits: light chain (Lc) without drug (Lc0), Lc with 1 drug (Lc1), heavy chain (Hc) without drug (Hc0), and Hc with 1-3 drugs (Hc1-3, respectively). A concurrent reduction strategy is applied to assess ADC subunits in both the partially reduced (intrachain disulfide bonds remain intact) and fully reduced (all disulfide bonds are cleaved) forms. The entire procedure including the sample preparation and LC-MS/MS takes less than 55 min, enabling rapid multiattribute analysis of ADCs.

Attenuation of immune-mediated bone marrow damage in conventionally housed mice.

In humans, bone marrow (BM) failure syndromes, both constitutional and acquired, predispose to myeloid malignancies. We have modeled acquired immune aplastic anemia, the paradigmatic disease of these syndromes, in the mouse by infusing lymph node cells from specific pathogen-free (SPF) CD45.1 congenic C57BL/6 (B6) donors into hybrid CByB6F1 recipients housed either in conventional (CVB) or SPF facilities. The severity of BM damage was reduced in CVB recipients; they also had reduced levels of CD44+ CD62L- effector memory T cells, reduced numbers of donor-type CD44+ T cells, and reduced expansion of donor-type CD8 T cells carrying T-cell receptor ß-variable regions 07, 11, and 17. Analyses of fecal samples through 16S ribosomal RNA amplicon sequencing revealed greater gut microbial alpha diversity in CVB mice relative to that of SPF mice. Thus, the presence of a broader spectrum of gut microorganisms in CVB-housed CByB6F1 could have primed recipient animal's immune system leading to suppression of allogeneic donor T-cell activation and expansion and attenuation of host BM destruction. These results suggest the potential benefit of diverse gut microbiota in patients receiving BM transplants.

Macrophage TNF-α licenses donor T cells in murine bone marrow failure and can be implicated in human aplastic anemia.

Interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) have been implicated historically in the immune pathophysiology of aplastic anemia (AA) and other bone marrow (BM) failure syndromes. We recently defined the essential roles of IFN-γ produced by donor T cells and the IFN-γ receptor in the host in murine immune-mediated BM failure models. TNF-α has been assumed to function similarly to IFN-γ. We used our murine models and mice genetically deficient in TNF-α or TNF-α receptors (TNF-αRs) to establish an analogous mechanism. Unexpectedly, infusion of TNF-α-/- donor lymph node (LN) cells into CByB6F1 recipients or injection of FVB LN cells into TNF-αR-/- recipients both induced BM failure, with concurrent marked increases in plasma IFN-γ and TNF-α levels. Surprisingly, in TNF-α-/- recipients, BM damage was attenuated, suggesting that TNF-α of host origin was essential for immune destruction of hematopoiesis. Depletion of host macrophages before LN injection reduced T-cell IFN-γ levels and reduced BM damage, whereas injection of recombinant TNF-α into FVB-LN cell-infused TNF-α-/- recipients increased T-cell IFN-γ expression and accelerated BM damage. Furthermore, infusion of TNF-αR-/- donor LN cells into CByB6F1 recipients reduced BM T-cell infiltration, suppressed T-cell IFN-γ production, and alleviated BM destruction. Thus, TNF-α from host macrophages and TNF-αR expressed on donor effector T cells were critical in the pathogenesis of murine immune-mediated BM failure, acting by modulation of IFN-γ secretion. In AA patients, TNF-α-producing macrophages in the BM were more frequent than in healthy controls, suggesting the involvement of this cytokine and these cells in human disease.

Conventional Co-Housing Modulates Murine Gut Microbiota and Hematopoietic Gene Expression.

Specific-pathogen-free (SPF) mice have improved hematopoietic characteristics relative to germ-free mice, however, it is not clear whether improvements in hematopoietic traits will continue when the level of microorganism exposure is further increased. We co-housed SPF C57BL/6 mice in a conventional facility (CVT) and found a significant increase in gut microbiota diversity along with increased levels of myeloid cells and T cells, especially effector memory T cells. Through single cell RNA sequencing of sorted KL (c-Kit+Lin-) cells, we imputed a decline in long-term hematopoietic stem cells and an increase in granulocyte-monocyte progenitors in CVT mice with up-regulation of genes associated with cell survival. Bone marrow transplantation through competitive repopulation revealed a significant increase in KSL (c-Kit+Sca-1+Lin-) cell reconstitution in recipients of CVT donor cells which occurred when donors were co-housed for both one and twelve months. However, there was minimal to no gain in mature blood cell engraftment in recipients of CVT donor cells relative to those receiving SPF donor cells. We conclude that co-housing SPF mice with mice born in a conventional facility increased gut microbiota diversity, augmented myeloid cell production and T cell activation, stimulated KSL cell reconstitution, and altered hematopoietic gene expression.