In Vitro Behavior of Hematopoietic Progenitor Cells Under the Influence of Chemoattractants: Stromal Cell–Derived Factor-1, Steel Factor, and the Bone Marrow Environment

Characterization, immune response and antibacterial mechanism of CXCL12 in black rockfish (Sebastes schlegelii)

Black rockfish (Sebastes schlegelii) is one of the most important mariculture fish in the Western North Pacific. Although the crucial roles of CXCL12 in immune responses against bacterial infection are well-known, the specific mechanisms underlying its involvement in fish immunity remain poorly understood. In this study, we systematically characterized CXCL12a and CXCL12b in Sebastes schlegelii (SsCXCL12a and SsCXCL12b), Firstly, SsCXCL12a/b were ubiquitously expressed across all seven tissues. Both SsCXCL12a/b were significantly differentially expressed in gill, kidney, liver, and spleen after Aeromonas salmonicida infection. Secondly, both rSsCXCL12a/b were observed to possess chemotactic activity towards spleen and peripheral blood leukocytes. Thirdly, the pathogen binding ability of rSsCXCL12a and rSsCXCL12b might be fulfilled through the recognition of PAMPs (Pathogen-Associated Molecular Patterns) on the surface of bacteria. rSsCXCL12a/b showed local agglutination effect to different bacteria. Subsequently, by detecting the permeability of the cell membrane, it was speculated that membrane attack might be one of the mechanisms by which rSsCXCL12a/b exert antimicrobial effects. Finally, it was speculated that CXCL12a/CXCR4b and CXCL12b/CXCR4a might be the major antimicrobial axes in black rockfish using Dual-Luciferase reporter gene assay system. Overall, the CXCL12/CXCR4 axis is critically involved in the immune response of S. schlegelii against bacterial infection.

Advancements in microenvironment-based therapies: transforming the landscape of multiple myeloma treatment

Multiple myeloma (MM) is the most prevalent malignant monoclonal disease of plasma cells. There is mounting evidence that interactions with the bone marrow (BM) niche are essential for the differentiation, proliferation, survival, migration, and treatment resistance of myeloma cells. For this reason, gaining a deeper comprehension of how BM microenvironment compartments interact with myeloma cells may inspire new therapeutic ideas that enhance patient outcomes. This review will concentrate on the most recent findings regarding the mechanisms of interaction between microenvironment and MM and highlight research on treatment targeting the BM niche.

Circadian-clock-controlled endocrine and cytokine signals regulate multipotential innate lymphoid cell progenitors in the bone marrow

Innate lymphoid cells (ILCs), strategically positioned throughout the body, undergo population declines over time. A solution to counteract this problem is timely mobilization of multipotential progenitors from the bone marrow. It remains unknown what triggers the mobilization of bone marrow ILC progenitors (ILCPs). We report that ILCPs are regulated by the circadian clock to emigrate and generate mature ILCs in the periphery. We found that circadian-clock-defective ILCPs fail to normally emigrate and generate ILCs. We identified circadian-clock-controlled endocrine and cytokine cues that, respectively, regulate the retention and emigration of ILCPs at distinct times of each day. Activation of the stress-hormone-sensing glucocorticoid receptor upregulates CXCR4 on ILCPs for their retention in the bone marrow, while the interleukin-18 (IL-18) and RORα signals upregulate S1PR1 on ILCPs for their mobilization to the periphery. Our findings establish important roles of circadian signals for the homeostatic efflux of bone marrow ILCPs.

Understanding the interaction between leukaemia stem cells and their microenvironment to improve therapeutic approaches

Although chemotherapeutic regimens can eliminate blasts in leukaemia patients, such therapies are associated with toxicity and often fail to eliminate all malignant cells resulting in disease relapse. Disease relapse has been attributed to the persistence of leukaemia cells in the bone marrow (BM) with the capacity to recapitulate disease; these cells are often referred to as leukaemia stem cells (LSCs). Although LSCs have distinct characteristics in terms of pathobiology and immunophenotype, they are still regulated by their interactions with the surrounding microenvironment. Thus, understanding the interaction between LSCs and their microenvironment is critical to identify effective therapies. To this end, there are numerous efforts to develop models to study such interactions. In this review, we will focus on the reciprocal interactions between LSCs and their milieu in the BM. Furthermore, we will highlight relevant therapies targeting these interactions and discuss some of the promising in vitro models designed to mimic such relationship. LINKED ARTICLES: This article is part of a themed issue on Cancer Microenvironment and Pharmacological Interventions. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.2/issuetoc.

Aptamer-functionalized hydrogels promote bone healing by selectively recruiting endogenous bone marrow mesenchymal stem cells

Bone regeneration heavily relies on bone marrow mesenchymal stem cells (BMSCs). However, recruiting endogenous BMSCs for in situ bone regeneration remains challenging. In this study, we developed a novel BMSC-aptamer (BMSC-apt) functionalized hydrogel (BMSC-aptgel) and evaluated its functions in recruiting BMSCs and promoting bone regeneration. The functional hydrogels were synthesized between maleimide-terminated 4-arm polyethylene glycols (PEG) and thiol-flanked PEG crosslinker, allowing rapid in situ gel formation. The aldehyde group-modified BMSC-apt was covalently bonded to a thiol-flanked PEG crosslinker to produce high-density aptamer coverage on the hydrogel surface. In vitro and in vivo studies demonstrated that the BMSC-aptgel significantly increased BMSC recruitment, migration, osteogenic differentiation, and biocompatibility. In vivo fluorescence tomography imaging demonstrated that functionalized hydrogels effectively recruited DiR-labeled BMSCs at the fracture site. Consequently, a mouse femur fracture model significantly enhanced new bone formation and mineralization. The aggregated BMSCs stimulated bone regeneration by balancing osteogenic and osteoclastic activities and reduced the local inflammatory response via paracrine effects. This study's findings suggest that the BMSC-aptgel can be a promising and effective strategy for promoting in situ bone regeneration.

Correlation between SDF-1α, CD34 positive hematopoietic stem cells and CXCR4 expression with liver fibrosis in CCl4 rat model

BACKGROUND

One of the most frequent disorders is liver fibrosis. An improved understanding of the different events during the process of liver fibrosis & its reversibility could be helpful in its staging and in finding potential therapeutic agents.

AIM

The goal of this research was to evaluate the relationship among CD34 + HPSCs, SDF-1α, and CXCR4 receptor expression with the percentage of the area of hepatic fibrosis.

MATERIALS AND METHODS

Thirty-six male Sprague-Dawley rats were separated into the control group, liver injury group & spontaneous reversion group. The liver injury was induced by using 2 ml/kg CCl4 twice a week. Flow cytometric examination of CD34 + cells in the blood & liver was performed. Bone marrow & liver samples were taken for evaluation of the SDF-1α mRNA by PCR. Liver specimens were stained for histopathological and CXCR4 immuno-expression evaluation.

RESULTS

In the liver injury group, the hepatic enzymes, fibrosis area percentage, CXCR4 receptor expression in the liver, CD34 + cells in the blood and bone marrow & the level SDF-1α in the liver and its concentration gradient were statistically significantly elevated with the progression of the liver fibrosis. On the contrary, SDF-1α in the bone marrow was statistically significantly reduced with the development of liver fibrosis. During the spontaneous reversion group, all the studied parameters apart from SDF-1α in the bone marrow were statistically substantially decreased compared with the liver injury group. We found a statistically substantial positive correlation between fibrosis area and all of the following: liver enzymes, CXCR4 receptor expression in the liver, CD34 + cells in the blood and liver, and SDF- 1α in the liver and its concentration gradient. In conclusion, in CCl4 rat model, the fibrosis area is significantly correlated with many parameters in the blood, bone marrow, and liver, which can be used during the process of follow-up during the therapeutic interventions.

Molecular and immunological mechanisms of clonal evolution in multiple myeloma

Multiple myeloma (MM) is a hematologic malignancy characterized by the proliferation of clonal plasma cells in the bone marrow (BM). It is known that early genetic mutations in post-germinal center B/plasma cells are the cause of myelomagenesis. The acquisition of additional chromosomal abnormalities and distinct mutations further promote the outgrowth of malignant plasma cell populations that are resistant to conventional treatments, finally resulting in relapsed and therapy-refractory terminal stages of MM. In addition, myeloma cells are supported by autocrine signaling pathways and the tumor microenvironment (TME), which consists of diverse cell types such as stromal cells, immune cells, and components of the extracellular matrix. The TME provides essential signals and stimuli that induce proliferation and/or prevent apoptosis. In particular, the molecular pathways by which MM cells interact with the TME are crucial for the development of MM. To generate successful therapies and prevent MM recurrence, a thorough understanding of the molecular mechanisms that drive MM progression and therapy resistance is essential. In this review, we summarize key mechanisms that promote myelomagenesis and drive the clonal expansion in the course of MM progression such as autocrine signaling cascades, as well as direct and indirect interactions between the TME and malignant plasma cells. In addition, we highlight drug-resistance mechanisms and emerging therapies that are currently tested in clinical trials to overcome therapy-refractory MM stages.

Sex and Circadian Timing Modulate Oxaliplatin Hematological and Hematopoietic Toxicities

Oxaliplatin was nearly twice as hematotoxic, with optimal circadian timing differing by 6 h, in women as compared to men with colorectal cancers. Hence, we investigated sex- and timing-related determinants of oxaliplatin hematopoietic toxicities in mice. Body-weight loss (BWL), blood cell counts, bone marrow cellularity (BMC) and seven flow-cytometry-monitored hematopoietic progenitor populations were evaluated 72 h after oxaliplatin chronotherapy administration (5 mg/kg). In control animals, circadian rhythms of circulating white blood cells showed a peak at ZT5 in both sexes, whereas BMC was maximum at ZT20 in males and ZT13h40 in females. All BM progenitor counts presented robust rhythms with phases around ZT3h30 in females, whereas only three of them rhythmically cycled in males with a ≈ -6 h phase shift. In treated females, chronotoxicity rhythms occurred in BWL, WBC, BMC and all BM progenitors with the best timing at ZT15, ZT21, ZT15h15 and ZT14h45, respectively. In males, almost no endpoints showed circadian rhythms, BWL and WBC toxicity being minimal, albeit with a substantial drop in BM progenitors. Increasing dose (10 mg/kg) in males induced circadian rhythms in BWL and WBC but not in BM endpoints. Our results suggest complex and sex-specific clock-controlled regulation of the hematopoietic system and its response to oxaliplatin.

Dysregulated transforming growth factor-beta mediates early bone marrow dysfunction in diabetes

Diabetes affects select organs such as the eyes, kidney, heart, and brain. Our recent studies show that diabetes also enhances adipogenesis in the bone marrow and reduces the number of marrow-resident vascular regenerative stem cells. In the current study, we have performed a detailed spatio-temporal examination to identify the early changes that are induced by diabetes in the bone marrow. Here we show that short-term diabetes causes structural and molecular changes in the marrow, including enhanced adipogenesis in tibiae of mice, prior to stem cell depletion. This enhanced adipogenesis was associated with suppressed transforming growth factor-beta (TGFB) signaling. Using human bone marrow-derived mesenchymal progenitor cells, we show that TGFB pathway suppresses adipogenic differentiation through TGFB-activated kinase 1 (TAK1). These findings may inform the development of novel therapeutic targets for patients with diabetes to restore regenerative stem cell function.

DEK, a nuclear protein, is chemotactic for hematopoietic stem/progenitor cells acting through CXCR2 and Gαi signaling

Few cytokines/growth modulating proteins are known to be chemoattractants for hematopoietic stem (HSC) and progenitor cells (HPC); stromal cell-derived factor 1α (SDF1α/CXCL12) being the most potent known such protein. DEK, a nuclear DNA-binding chromatin protein with hematopoietic cytokine-like activity, is a chemotactic factor attracting mature immune cells. Transwell migration assays were performed to test whether DEK serves as a chemotactic agent for HSC/HPC. DEK induced dose- and time-dependent directed migration of lineage negative (Lin- ) Sca-1+ c-Kit+ (LSK) bone marrow (BM) cells, HSCs and HPCs. Checkerboard assays demonstrated that DEK's activity was chemotactic (directed), not chemokinetic (random migration), in nature. DEK and SDF1α compete for HSC/HPC chemotaxis. Blocking CXCR2 with neutralizing antibodies or inhibiting Gαi protein signaling with Pertussis toxin pretreatment inhibited migration of LSK cells toward DEK. Thus, DEK is a novel and rare chemotactic agent for HSC/HPC acting in a direct or indirect CXCR2 and Gαi protein-coupled signaling-dependent manner.

Microarrayed human bone marrow organoids for modeling blood stem cell dynamics

In many leukemia patients, a poor prognosis is attributed either to the development of chemotherapy resistance by leukemic stem cells (LSCs) or to the inefficient engraftment of transplanted hematopoietic stem/progenitor cells (HSPCs) into the bone marrow (BM). Here, we build a 3D in vitro model system of bone marrow organoids (BMOs) that recapitulate several structural and cellular components of native BM. These organoids are formed in a high-throughput manner from the aggregation of endothelial and mesenchymal cells within hydrogel microwells. Accordingly, the mesenchymal compartment shows partial maintenance of its self-renewal and multilineage potential, while endothelial cells self-organize into an interconnected vessel-like network. Intriguingly, such an endothelial compartment enhances the recruitment of HSPCs in a chemokine ligand/receptor-dependent manner, reminiscent of HSPC homing behavior in vivo. Additionally, we also model LSC migration and nesting in BMOs, thus highlighting the potential of this system as a well accessible and scalable preclinical model for candidate drug screening and patient-specific assays.

Molecular Impact of the Tumor Microenvironment on Multiple Myeloma Dissemination and Extramedullary Disease

Multiple myeloma (MM) is the most common malignant monoclonal disease of plasma cells. Aside from classical chemotherapy and glucocorticoids, proteasome inhibitors, immunomodulatory agents and monoclonal antibodies are used in the current treatment scheme of MM. The tumor microenvironment (TME) plays a fundamental role in the development and progression of numerous solid and non-solid cancer entities. In MM, the survival and expansion of malignant plasma cell clones heavily depends on various direct and indirect signaling pathways provided by the surrounding bone marrow (BM) niche. In a number of MM patients, single plasma cell clones lose their BM dependency and are capable to engraft at distant body sites or organs. The resulting condition is defined as an extramedullary myeloma (EMM). EMMs are highly aggressive disease stages linked to a dismal prognosis. Emerging literature demonstrates that the dynamic interactions between the TME and malignant plasma cells affect myeloma dissemination. In this review, we aim to summarize how the cellular and non-cellular BM compartments can promote plasma cells to exit their BM niche and metastasize to distant intra-or extramedullary locations. In addition, we list selected therapy concepts that directly target the TME with the potential to prevent myeloma spread.

CD271 antibody-functionalized microspheres capable of selective recruitment of reparative endogenous stem cells for in situ bone regeneration

In the strategy of in situ bone regeneration, it used to be difficult to specifically recruit bone marrow mesenchymal stem cells (BM-MSCs) by a single marker. Recently, CD271 has been considered to be one of the most specific markers to isolate BM-MSCs; however, the effectiveness of CD271 antibodies in recruiting BM-MSCs has not been explored yet. In this study, we developed novel CD271 antibody-functionalized chitosan (CS) microspheres with the aid of polydopamine (PDA) coating to recruit endogenous BM-MSCs for in situ bone regeneration. The CS microspheres were sequentially modified with PDA and CD271 antibody through dopamine self-polymerization and bioconjugation, respectively. In vitro studies showed that the CD271 antibody-functionalized microspheres selectively captured significantly more BM-MSCs from a fluorescently labeled heterotypic cell population than non-functionalized controls. In addition, the PDA coating was critical for supporting stable adhesion and proliferation of the captured BM-MSCs. Effective early recruitment of CD271⁺ stem cells by the functionalized microspheres at bone defect site of SD rat was observed by the CD271/DAPI immunofluorescence staining, which led to significantly enhanced new bone formation in rat femoral condyle defect over long term. Together, findings from this study have demonstrated, for the first time, that the CD271 antibody-functionalized CS microspheres are promising for in situ bone regeneration.

Mitigating oxygen stress enhances aged mouse hematopoietic stem cell numbers and function

Bone marrow (BM) hematopoietic stem cells (HSCs) become dysfunctional during aging (i.e., they are increased in number but have an overall reduction in long-term repopulation potential and increased myeloid differentiation) compared with young HSCs, suggesting limited use of old donor BM cells for hematopoietic cell transplantation (HCT). BM cells reside in an in vivo hypoxic environment yet are evaluated after collection and processing in ambient air. We detected an increase in the number of both young and aged mouse BM HSCs collected and processed in 3% O2 compared with the number of young BM HSCs collected and processed in ambient air (~21% O2). Aged BM collected and processed under hypoxic conditions demonstrated enhanced engraftment capability during competitive transplantation analysis and contained more functional HSCs as determined by limiting dilution analysis. Importantly, the myeloid-to-lymphoid differentiation ratio of aged BM collected in 3% O2 was similar to that detected in young BM collected in ambient air or hypoxic conditions, consistent with the increased number of common lymphoid progenitors following collection under hypoxia. Enhanced functional activity and differentiation of old BM collected and processed in hypoxia correlated with reduced "stress" associated with ambient air BM collection and suggests that aged BM may be better and more efficiently used for HCT if collected and processed under hypoxia so that it is never exposed to ambient air O2.

Role of Stromal Cell-Derived Factor-1 in Endothelial Progenitor Cell-Mediated Vascular Repair and Regeneration

Endothelial progenitor cells (EPCs) are immature endothelial cells that participate in vascular repair and postnatal neovascularization and provide a novel and promising therapy for the treatment of vascular disease. Studies in different animal models have shown that EPC mobilization through pharmacological agents and autologous EPC transplantation contribute to restoring blood supply and tissue regeneration after ischemic injury. However, these effects of the progenitor cells in clinical studies exhibit mixed results. The therapeutic efficacy of EPCs is closely associated with the number of the progenitor cells recruited into ischemic regions and their functional abilities and survival in injury tissues. In this review, we discussed the regulating role of stromal cell-derived factor-1 (also known CXCL12, SDF-1) in EPC mobilization, recruitment, homing, vascular repair and neovascularization, and analyzed the underlying machemisms of these functions. Application of SDF-1 to improve the regenerative function of EPCs following vascular injury was also discussed. SDF-1 plays a crucial role in mobilizing EPC from bone marrow into peripheral circulation, recruiting the progenitor cells to target tissue and protecting against cell death under pathological conditions; thus improve EPC regenerative capacity. SDF-1 are crucial for regulating EPC regenerative function, and provide a potential target for improve therapeutic efficacy of the progenitor cells in treatment of vascular disease.

All in for nuclear PFKP-induced CXCR4 metastasis: a T cell acute lymphoblastic leukemia prognostic marker

Phosphofructokinase 1 (PFK1) is expressed in T cell acute lymphoblastic leukemia (T-ALL), where its upregulation is linked with cancer progression. While PFK1 functions in the glycolysis pathway within the cytoplasm, it is also present in the nucleus where it regulates gene transcription. In this issue of the JCI, Xueliang Gao, Shenghui Qin, et al. focus their mechanism-based investigation on the nucleocytoplasmic shuttling aspect of the PFK1 platelet isoform, PFKP. Functional nuclear export and localization sequences stimulated CXC chemokine receptor type 4 (CXCR4) expression to promote T-ALL invasion that involved cyclin D3/CDK6, c-Myc, and importin-9. Since the presence of nuclear PFKP is associated with poor survival in T-ALL, nuclear PFKP-induced CXCR4 expression might serve as a prognostic marker for T-ALL. More promising, though, are the mechanistic insights suggesting that approaches to dampening metastatic migration may have application to benefit patients with T-ALL.

The Impact of Sedentary Lifestyle, High-fat Diet, Tobacco Smoke, and Alcohol Intake on the Hematopoietic Stem Cell Niches

Hematopoietic stem and progenitor cells maintain hematopoiesis throughout life by generating all major blood cell lineages through the process of self-renewal and differentiation. In adult mammals, hematopoietic stem cells (HSCs) primarily reside in the bone marrow (BM) at special microenvironments called “niches.” Niches are thought to extrinsically orchestrate the HSC fate including their quiescence and proliferation. Insight into the HSC niches mainly comes from studies in mice using surface marker identification and imaging to visualize HSC localization and association with niche cells. The advantage of mouse models is the possibility to study the 3-dimensional BM architecture and cell interactions in an intact traceable system. However, this may not be directly translational to human BM. Sedentary lifestyle, unhealthy diet, excessive alcohol intake, and smoking are all known risk factors for various diseases including hematological disorders and cancer, but how do lifestyle factors impact hematopoiesis and the associated niches? Here, we review current knowledge about the HSC niches and how unhealthy lifestyle may affect it. In addition, we summarize epidemiological data concerning the influence of lifestyle factors on hematological disorders and malignancies.

Role and Therapeutic Targeting of SDF-1α/CXCR4 Axis in Multiple Myeloma

Simple Summary

The SDF-1α/CXCR4 axis plays crucial roles in proliferation, survival, invasion, dissemination, and drug resistance in multiple myeloma. This review summarizes the pleiotropic role of the SDF-1α/CXCR4 axis in multiple myeloma and introduces the SDF-1α/CXCR4 axis-targeted therapies in multiple myeloma.

Abstract

The C-X-C chemokine receptor type 4 (CXCR4) is a pleiotropic chemokine receptor that is expressed in not only normal hematopoietic cells but also multiple myeloma cells. Its ligand, stromal cell-derived factor 1α (SDF-1α) is produced in the bone marrow microenvironment. The SDF-1α/CXCR4 axis plays a pivotal role in the major physiological processes associated with tumor proliferation, survival, invasion, dissemination, and drug resistance in myeloma cells. This review summarizes the pleiotropic role of the SDF-1α/CXCR4 axis in multiple myeloma and discusses the future perspective in the SDF-1α/CXCR4 axis-targeted therapies in multiple myeloma.

Endometriosis stromal cells induce bone marrow mesenchymal stem cell differentiation and PD-1 expression through paracrine signaling

Endometriosis is an estrogen-dependent, inflammatory gynecological disorder characterized by the growth of endometrial cells in lesions outside the uterus. Bone marrow-derived cells (BMDCs) engraft lesions and increase lesion size. Do endometriosis cells regulate differentiation of engrafted BMDCs in the pathogenesis and growth of endometriosis? Here, we report endometriosis derived stromal cells promote the differentiation of BMDCs to stromal, epithelial and leukocyte cell fates through paracrine signaling. In-vitro studies demonstrated that both mRNA and protein levels of vimentin, cytokeratin and PD-1 were significantly increased in BMDCs cocultured with stromal cells from endometriosis (ENDO) patients compared to stromal cells from normal endometrium (CNTL). Increased expression of PD-1 has been reported in malignancy where it promotes T cell quiescence and immune tolerance. Increased PD-1 was also confirmed in-vivo where we showed that PD-1 expression was induced in BMDCs engrafted into endometriotic lesions in a murine model of endometriosis. AMD3100, an antagonist for CXCR4 receptor inhibited PD-1 expression in BMDCs suggesting that PD-1 induction requires CXCL12. These results suggest that endometriosis stimulated BMDC differentiation through paracrine signaling and increased T cell PD-1 expression. Increased PD-1 expression may be one mechanism by which endometriosis avoids immune surveillance.

Progress towards improving homing and engraftment of hematopoietic stem cells for clinical transplantation

PURPOSE OF REVIEW

Hematopoietic cell transplantation (HCT) is a life-saving treatment for a variety of hematological and nonhematological disorders. Successful clinical outcomes after transplantation rely on adequate hematopoietic stem cell (HSC) numbers, and the homing and subsequent short-term and long-term engraftment of these cells in the bone marrow. Enhancing the homing capability of HSCs has the potential for high impact on improving HCT and patient survival.

RECENT FINDINGS

There are a number of ways to enhance HSC engraftment. Neutralizing negative epigenetic regulation by histone deacetylase 5 (HDAC5) increases surface CXCR4 expression and promotes human HSC homing and engraftment in immune-deficient NSG (NOD.Cg-Prkdc IL2rgt/Sz) mice. Short-term treatment of cells with glucocorticoids, pharmacological stabilization of hypoxia-inducible factor (HIF)-1α, increasing membrane lipid raft aggregation, and inhibition of dipeptidyl peptidase 4 (DPP4) facilitates HSC homing and engraftment. Added to these procedures, modulating the mitochondria permeability transition pore (MPTP) to mitigate ambient air-induced extra physiological oxygen stress/shock (EPHOSS) by hypoxic harvest and processing, or using cyclosporine A during air collection increases functional HSC numbers and improves HSC engraftment.

SUMMARY

A better understanding of the regulation of human HSC homing mediated by various signaling pathways will facilitate development of more efficient means to enhance HCT efficacy.

The IL-33 Receptor/ST2 acts as a positive regulator of functional mouse bone marrow hematopoietic stem and progenitor cells

There is a paucity of information on a potential role for the IL-33 receptor/ST2 in the regulation of mouse bone marrow (BM) hematopoietic stem (HSC) and progenitor (HPC) cells. Comparing the BM of st2^−/− and wild type (WT) control mice using functional assays, it was found that st2^−/− BM cells had poorer engrafting capacity than WT BM in a competitive repopulating assay using congenic mice, with no changes in reconstitution of B-, T- and myeloid cells following transplantation. The BM of st2^−/− mice also had fewer granulocyte-macrophage, erythroid, and multipotential progenitors than that of WT BM and these st2^−/− HPC were in a slow cycling state compared to that of the rapidly cycling HPC of the WT mice. While functional assessment of HSC and HPC demonstrated that ST2 has a positive influence on regulation of HSC, we could not pick up differences in st2^−/− compared to WT BM using only phenotypic analysis of HSC and HPC populations prior to transplantation, again demonstrating that phenotypic analysis of HSC and HPC do not always recapitulate the functional assessments of these immature hematopoietic cells.

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ST2 is a positive modulator of hematopoiesis.

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ST2^-/- is a positive modulator of hematopoiesis

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Immunophenotyping of st2^-/- hematopoietic stem cell numbers does not recapitulate functional capability of these cells.

Stromal cell-derived factor-1 (SDF-1) expression in very preterm human lungs: potential relevance for stem cell therapy for bronchopulmonary dysplasia

Background: The axis formed by CXC chemokine receptor 4 (CXCR4), expressed on mesenchymal stromal cells (MSCs), and stromal cell-derived factor-1 (SDF-1), expressed in recipient organs, is a critical mediator of MSC migration in non-pulmonary injury models. The role and regulation of SDF-1 expression in preterm lungs, of potential relevance for MSC-based cell therapy for bronchopulmonary dysplasia (BPD), is unknown. The aim of this study was to determine the spatiotemporal pattern of CXCR4/SDF-1 expression in lungs of extremely preterm infants at risk for BPD.Methods: Postmortem lung samples were collected from ventilated extremely preterm infants who died between 23 and 29 wks ("short-term ventilated") or between 36 and 39 wks ("long-term ventilated") corrected postmenstrual age. Results were compared with age-matched infants who had lived <12 h or stillborn infants ("early" and "late" controls). CXCR4 and SDF-1 expression was studied by immunohistochemistry, immunofluorescence/confocal microscopy, and qRT-PCR analysis.Results: Compared with age-matched controls without antenatal infection, lungs of early control infants with evidence of intrauterine infection/inflammation showed significant upregulation of SDF-1 expression, localized to the respiratory epithelium, and of CXCR4 expression, localized to stromal cells. Similarly, pulmonary SDF-1 mRNA levels were significantly higher in long-term ventilated ex-premature infants with established BPD than in age-matched controls. The pulmonary vasculature was devoid of SDF-1 expression at all time points. Endogenous CXCR4-positive stromal cells were preferentially localized along the basal aspect of SDF-1-positive bronchial and respiratory epithelial cells, suggestive of functionality of the CXCR4/SDF-1 axis.Conclusions: Incipient and established neonatal lung injury is associated with upregulation of SDF-1 expression, restricted to the respiratory epithelium. Knowledge of the clinical associations, time-course and localization of pulmonary SDF-1 expression may guide decisions about the optimal timing and delivery route of MSC-based cell therapy for BPD.

EMA Recommendation for the Pediatric Indications of Plerixafor (Mozobil) to Enhance Mobilization of Hematopoietic Stem Cells for Collection and Subsequent Autologous Transplantation in Children with Lymphoma or Malignant Solid Tumors

On March 28, 2019, the Committee for Medicinal Products for Human Use adopted a positive opinion recommending the marketing authorization for the medicinal product plerixafor. The marketing authorization holder for this medicinal product is Genzyme Europe B.Th. The adoption was for an extension of the existing adult indication in combination with granulocyte colony-stimulating factor (G-CSF) to pediatric patients (aged 1 year to <18 years) to enhance mobilization of hematopoietic stem cells to the peripheral blood for collection and subsequent autologous transplantation in children with lymphoma or solid malignant tumors. This treatment is indicated either preemptively, when circulating stem cell count on the predicted day of collection after adequate mobilization with G-CSF (with or without chemotherapy) is expected to be insufficient with regard to desired hematopoietic stem cells yield, or in children who previously failed to collect sufficient hematopoietic stem cells. The efficacy and safety of plerixafor were evaluated in an open label, multicenter, phase I/II, dose-ranging, and randomized controlled study (DFI12860) in pediatric patients with solid tumors, including neuroblastoma, sarcoma, Ewing sarcoma, or lymphoma, who were eligible for autologous hematopoietic stem cell transplantation. Forty-five patients (aged 1 year to <18 years) were randomized, 2:1, using 0.24 mg/kg of plerixafor plus standard mobilization (G-CSF with or without chemotherapy) versus control (standard mobilization alone). The primary analysis showed that 80% of patients in the plerixafor arm experienced at least a doubling of the peripheral blood (PB) CD34+ count, observed from the morning of the day preceding the first planned apheresis to the morning prior to apheresis, versus 28.6% of patients in the control arm (p = .0019). The median increase in PB CD34+ cell counts from baseline to the day of apheresis was 3.2-fold in the plerixafor arm versus by 1.4-fold in the control arm. The observed safety profile in the pediatric population was consistent with that in adults, with adverse events mainly related to injection site reactions, hypokalemia, and increased blood bicarbonate. Importantly, plerixafor exposure did not seem to negatively affect transplant efficiency. This article summarizes the scientific review of the application leading to regulatory approval in the European Union. IMPLICATIONS FOR PRACTICE: This review of the marketing authorization of plerixafor will raise awareness of pediatric indication granted for this medicinal product.

Bone marrow-derived cells or C-X-C motif chemokine 12 (CXCL12) treatment improve thin endometrium in a mouse model

Successful implantation and pregnancy is dependent on sufficient endometrial growth during each reproductive cycle. Here, we report the therapeutic effect of either bone marrow-derived cells (BMDCs) or the stem cell chemo-attractant C-X-C motif chemokine 12 (CXCL12) on endometrial receptivity in a murine ethanol induced thin endometrium model. Endometrial epithelial area was significantly increased in mice treated with BMDCs, CXCL12, or by co-treatment with both compared with PBS-treated controls. Ki-67 and CD31 immunoreactivity was significantly higher in mice treated with either BMDCs, CXCL12, or both. The mRNA expression levels of endometrial receptivity markers leukemia inhibitory factor, interleukin-1β, and integrin beta-3 were increased in mice treated with either BMDCs, CXCL12, or both. The mRNA levels of matrix metalloproteinase-2 and -9 were significantly decreased by BMDCs but not by CXCL12. Pregnancy rates and litter size were increased after either treatment. Both BMDCs and CXCL12 displayed a comparable efficacy on endometrial regeneration in mice with thin endometrium. Our findings indicate the potential therapeutic effects of BMDCs and CXCL12 on infertility related to thin endometrium. Bone marrow-derived cells and CXCL12 displayed a comparable efficacy on endometrial regeneration in mice with thin endometrium.

Incorporation of Stromal Cell-Derived Factor-1α in Three-Dimensional Hydroxyapatite/Polyacrylonitrile Composite Scaffolds for Bone Regeneration

Bone regeneration strategies rely on biomaterial constructs with stem cells or growth factors. By comparison, cell homing strategies employ chemokines to recruit the host endogenous stem or progenitor cells to the defect site to support endogenous healing. In the present study, we used a novel fluffy hydroxyapatite/polyacrylonitrile (HA/PAN) composite scaffold to provide a better three-dimensional cell culture microenvironment. These HA/PAN composite scaffolds loaded with stromal cell-derived factor-1α (SDF-1α) provided a diffusion-controlled SDF-1α release profile and endowed the scaffolds with cell homing capabilities. Furthermore, the scaffolds significantly stimulated bone marrow stromal cell (BMSC) recruitment, facilitated BMSC osteogenic differentiation, and promoted ectopic bone formation. Our results suggest that a HA/PAN composite scaffold loaded with SDF-1α offers a clinically beneficial bone repair strategy.

Pathological roles of the homeostatic chemokine CXCL12

CXCL12 is a CXC chemokine that traditionally has been classified as a homeostatic chemokine. It contributes to physiological processes such as embryogenesis, hematopoiesis and angiogenesis. In contrast to these homeostatic functions, increased expression of CXCL12 in general, or of a specific CXCL12 splicing variant has been demonstrated in various pathologies. In addition to this increased or differential transcription of CXCL12, also upregulation of its receptors CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) contributes to the onset or progression of diseases. Moreover, posttranslational modification of CXCL12 during disease progression, through interaction with locally produced molecules or enzymes, also affects CXCL12 activity, adding further complexity. As CXCL12, CXCR4 and ACKR3 are broadly expressed, the number of pathologies wherein CXCL12 is involved is growing. In this review, the role of the CXCL12/CXCR4/ACKR3 axis will be discussed for the most prevalent pathologies. Administration of CXCL12-neutralizing antibodies or small-molecule antagonists of CXCR4 or ACKR3 delays disease onset or prevents disease progression in cancer, viral infections, inflammatory bowel diseases, rheumatoid arthritis and osteoarthritis, asthma and acute lung injury, amyotrophic lateral sclerosis and WHIM syndrome. On the other hand, CXCL12 has protective properties in Alzheimer's disease and multiple sclerosis, has a beneficial role in wound healing and has crucial homeostatic properties in general.

Immunological effects of a low-dose cytarabine, aclarubicin and granulocyte-colony stimulating factor priming regimen on a mouse leukemia model

The low-dose cytarabine, aclarubicin and granulocyte-colony stimulating factor (G-CSF) (CAG) priming regimen is an effective treatment for patients with relapsed or refractory acute myeloid leukemia (AML) and advanced myelodysplastic syndrome (MDS). G-CSF influences the bone marrow microenvironment (BMM) by mobilizing regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), as well as by reducing the expression of stromal cell-derived factor-1α (SDF-1α). In the present study, a WEHI-3-grafted BALB/c mouse AML model (AML-M4) was employed to determine how the BMM was altered by different treatment regimens. It was evident that CAG regimen decreased and increased the proportion of Tregs and MDSCs in the bone marrow and spleen, respectively. Furthermore, the CAG regimen downregulated SDF-1α levels in the bone marrow and peripheral blood. However, hematoxylin and eosin staining of the main organs revealed that leukemic cells infiltrated the liver following treatment with the CAG regimen. The present study indicates that the CAG regimen has a positive effect on the immunosuppressive microenvironment in AML and relieves AML-associated BMM immune suppression by decreasing Tregs and MDSCs in the bone marrow and downregulating the SDF-1α/CXCR4 axis in the bone marrow and peripheral blood.

Natural nitration of CXCL12 reduces its signaling capacity and chemotactic activity in vitro and abrogates intra-articular lymphocyte recruitment in vivo

The chemokine CXCL12/stromal cell-derived factor-1 is important for leukocyte migration to lymphoid organs and inflamed tissues and stimulates tumor development. In vitro, CXCL12 activity through CXCR4 is abolished by proteolytic processing. However, limited information is available on in vivo effects of posttranslationally modified CXCL12. Natural CXCL12 was purified from the coculture supernatant of stromal cells stimulated with leukocytes and inflammatory agents. In this conditioned medium, CXCL12 with a nitration on Tyr⁷, designated [3-NT⁷]CXCL12, was discovered via Edman degradation. CXCL12 and [3-NT⁷]CXCL12 were chemically synthesized to evaluate the biological effects of this modification. [3-NT⁷]CXCL12 recruited β-arrestin 2 and phosphorylated the Akt kinase similar to CXCL12 in receptor-transfected cells. Also the affinity of CXCL12 and [3-NT⁷]CXCL12 for glycosaminoglycans, the G protein-coupled chemokine receptor CXCR4 and the atypical chemokine receptor ACKR3 were comparable. However, [3-NT⁷]CXCL12 showed a reduced ability to enhance intracellular calcium concentrations, to generate inositol triphosphate, to phosphorylate ERK1/2 and to induce monocyte and lymphocyte chemotaxis in vitro. Moreover, nitrated CXCL12 failed to induce in vivo extravasation of lymphocytes to the joint. In summary, nitration on Tyr⁷ under inflammatory conditions is a novel natural posttranslational regulatory mechanism of CXCL12 which may downregulate the CXCR4-mediated inflammatory and tumor-promoting activities of CXCL12.

Caffeic acid phenethyl ester promotes haematopoietic stem/progenitor cell homing and engraftment

Background

Several studies have suggested that caffeic acid phenethyl ester (CAPE) can induce the expression of hypoxia inducible factor-1α (HIF-1α) protein. We determined whether CAPE has a novel function in improving the homing and engraftment of haematopoietic stem/progenitor cells (HSPCs) by regulating HIF-1α gene expression in the bone marrow (BM) niche.

Methods

For survival experiments, lethally irradiated C57BL/6 mice were injected with a low number of BM mononuclear cells (MNCs) and CAPE according to the indicated schedule. Homing efficiency analysis was conducted using flow cytometry and colony-forming unit (CFU) assays. The influence of intraperitoneal injection of CAPE on short-term and long-term engraftment of HSPCs was evaluated using competitive and non-competitive mouse transplantation models. To investigate the mechanism by which CAPE enhanced HSPC homing, we performed these experiments including Q-PCR, western blot, immunohistochemistry and CFU assays after in-vivo HIF-1α activity blockade.

Results

CAPE injection significantly increased the survival rate of recipient mice after lethal irradiation and transplantation of a low number of BM MNCs. Using HSPC homing assays, we found that CAPE notably increased donor HSPC homing to recipient BM. The subsequent short-term and long-term engraftment of transplanted HSPCs was also improved by the optimal schedule of CAPE administration. Mechanistically, we found that CAPE upregulated the expression of HIF-1α, vascular endothelial growth factor-A (VEGF-A) and stromal cell-derived factor 1α (SDF-1α). The HIF-1α inhibitor PX-478 blocked CAPE-enhanced HSPC homing, which supported the idea that HIF-1α is a key target of CAPE.

Conclusions

Our results showed that CAPE administration facilitated HSPC homing and engraftment, and this effect was primarily dependent on HIF-1α activation and upregulation of SDF-1α and VEGF-A expression in the BM niche.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0708-x) contains supplementary material, which is available to authorized users.

The unique structural and functional features of CXCL12

The CXC chemokine CXCL12 is an important factor in physiological and pathological processes, including embryogenesis, hematopoiesis, angiogenesis and inflammation, because it activates and/or induces migration of hematopoietic progenitor and stem cells, endothelial cells and most leukocytes. Therefore, CXCL12 activity is tightly regulated at multiple levels. CXCL12 has the unique property of existing in six splice variants in humans, each having a specific tissue distribution and in vivo activity. Controlled splice variant transcription and mRNA stability determine the CXCL12 expression profile. CXCL12 fulfills its functions in homeostatic and pathological conditions by interacting with its receptors CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) and by binding to glycosaminoglycans (GAGs) in tissues and on the endothelium to allow a proper presentation to passing leukocytes. Homodimerizaton and heterodimerization of CXCL12 and its receptors can alter their signaling activity, as exemplified by the synergy between CXCL12 and other chemokines in leukocyte migration assays. Receptor binding may also initiate CXCL12 internalization and its subsequent removal from the environment. Furthermore, CXCL12 activity is regulated by posttranslational modifications. Proteolytic removal of NH₂- or COOH-terminal amino acids, citrullination of arginine residues by peptidyl arginine deiminases or nitration of tyrosine residues reduce CXCL12 activity. This review summarizes the interactions of CXCL12 with the cellular environment and discusses the different levels of CXCL12 activity regulation.

Celastrol attenuates pain and cartilage damage via SDF-1/CXCR4 signalling pathway in osteoarthritis rats

OBJECTIVES

Celastrol has attracted wide interests for its anticancer and anti-inflammation properties, and studies have demonstrated that celastrol negatively modulates the stromal cell-derived factor-1 (SDF-1) and receptor C-X-C chemokine receptor type 4 (CXCR4) signalling. We aim in this study to investigate the effects of celastrol in osteoarthritis (OA) in vivo and explored the underlying molecular mechanisms.

METHODS

We established a monoiodoacetate (MIA)-induced rat OA model and evaluated the joint pain and cartilage damage with or without celastrol treatments. We further assessed the alterations of the SDF-1/CXCR4 pathway and cartilage-specific genes, at both mRNA and protein levels.

KEY FINDINGS

Celastrol significantly attenuated the joint pain and cartilage damage induced by MIA in OA rats and suppressed the upregulation of SDF-1/CXCR4 and associated genes caused by MIA injections. Furthermore, MIA induced a decrease in cartilage-specific genes which was also prevented by celastrol treatments.

CONCLUSIONS

Celastrol ameliorate OA in vivo as evidenced by the attenuated joint pain and less cartilage damage in OA rats given celastrol treatments, an effect mediated via suppression of the SDF-1/CXCR4 pathway.

RhoA and RhoC are involved in stromal cell-derived factor-1-induced cell migration by regulating F-actin redistribution and assembly

Stromal cell-derived factor-1 (SDF-1) signaling is important to the maintenance and progression of T-cell acute lymphoblastic leukemia by inducing chemotaxis migration. To identify the mechanism of SDF-1 signaling in the migration of T-ALL, Jurkat acute lymphoblastic leukemia cells were used. Results showed that SDF-1 induces Jurkat cell migration by F-actin redistribution and assembly, which is dependent on Rho activity. SDF-1 induced RhoA and RhoC activation, as well as reactive oxygen species (ROS) production, which was inhibited by Rho inhibitor. The Rho-dependent ROS production led to subsequent cytoskeleton redistribution and assembly in the process of migration. Additionally, RhoA and RhoC were involved in SDF-1-induced Jurkat cell migration. Taken together, we found a SDF-1/CXCR4-RhoA and RhoC-ROS-cytoskeleton pathway that regulates Jurkat cell migration in response to SDF-1. This work will contribute to a clearer insight into the migration mechanism of acute lymphoblastic leukemia.

New agents in HSC mobilization

Mobilized peripheral blood (PB) is the most common source of hematopoietic stem cells (HSC) for autologous transplantation. Granulocyte colony stimulating factor (G-CSF) is the most commonly used mobilization agent, yet despite its widespread use, a considerable number of patients still fail to mobilize. Recently, a greater understanding of the interactions that regulate HSC homeostasis in the bone marrow (BM) microenvironment has enabled the development of new molecules that mobilize HSC through specific inhibition, modulation or perturbation of these interactions. AMD3100 (plerixafor), a small molecule that selectively inhibits the chemokine receptor CXCR4 is approved for mobilization in combination with G-CSF in patients with Non-Hodgkin's lymphoma and multiple myeloma. Nevertheless, identifying mobilization strategies that not only enhance HSC number, but are rapid and generate an optimal "mobilized product" for improved transplant outcomes remains an area of clinical importance. In recent times, new agents based on recombinant proteins, peptides and small molecules have been identified as potential candidates for therapeutic HSC mobilization. In this review, we describe the most recent developments in HSC mobilization agents and their potential impact in HSC transplantation.

Extracellular molecules in hematopoietic stem cell mobilisation

Hematopoietic stem cells are a remarkable resource currently used for the life saving treatment, hematopoietic stem cell transplantation. Today, hematopoietic stem cells are primarily obtained from mobilized peripheral blood following treatment of the donor with the cytokine G-CSF, and in some settings, chemotherapy and/or the CXCR4 antagonist plerixafor. The collection of hematopoietic stem cells is contingent on adequate and timely mobilization of these cells into the peripheral blood. The use of healthy donors, particularly when unrelated to the patient, requires mobilization strategies be safe for the donor. While current mobilization strategies are largely successful, adequate mobilization fails to occur in a significant portion of donors. Understanding the mechanisms involved in the egress of stem cells from the bone marrow provides opportunities to further improve the process of collecting hematopoietic stem cells. Here, the role extracellular components of the blood and bone marrow in the mobilization process are discussed.

Activation of Nrf2-ARE signaling mitigates cyclophosphamide-induced myelosuppression

Myelosuppression is the most common dose-limiting adverse effect of chemotherapies. In the present study, we investigated the involvement of nuclear erythroid 2-related factor 2 (Nrf2) in cyclophosphamide-induced myelosuppression in mice, and evaluated the potential of activating Nrf2 signaling as a preventive strategy. The whole blood from Nrf2^-/- mice exhibited decreased antioxidant capacities, while the bone marrow cells, peripheral blood mononuclear cells and granulocytes from Nrf2^-/- mice were more susceptible to acrolein-induced cytotoxicity than those from wild type mice. Single dosage of cyclophosphamide induced significantly severer acute myelosuppression in Nrf2^-/- mice than in wild type mice. Furthermore, Nrf2^-/- mice exhibited greater loss of peripheral blood nucleated cells and recovered slower from myelosuppression nadir upon multiple consecutive dosages of cyclophosphamide than wild type mice did. This was accompanied with decreased antioxidant and detoxifying gene expressions and impaired colony formation ability of Nrf2^-/- bone marrow cells. More importantly, activation of Nrf2 signaling by CDDO-Me significantly alleviated cyclophosphamide-induced myelosuppression, while this alleviation was diminished in Nrf2^-/- mice. In conclusion, the present study shows that Nrf2 plays a protective role in cyclophosphamide-induced myelosuppression and activation of Nrf2 is a promising strategy to prevent or treat chemotherapy-induced myelosuppression.

HIF-1α-PDK1 axis-induced active glycolysis plays an essential role in macrophage migratory capacity

In severely hypoxic condition, HIF-1α-mediated induction of Pdk1 was found to regulate glucose oxidation by preventing the entry of pyruvate into the tricarboxylic cycle. Monocyte-derived macrophages, however, encounter a gradual decrease in oxygen availability during its migration process in inflammatory areas. Here we show that HIF-1α-PDK1-mediated metabolic changes occur in mild hypoxia, where mitochondrial cytochrome c oxidase activity is unimpaired, suggesting a mode of glycolytic reprogramming. In primary macrophages, PKM2, a glycolytic enzyme responsible for glycolytic ATP synthesis localizes in filopodia and lammelipodia, where ATP is rapidly consumed during actin remodelling processes. Remarkably, inhibition of glycolytic reprogramming with dichloroacetate significantly impairs macrophage migration in vitro and in vivo. Furthermore, inhibition of the macrophage HIF-1α-PDK1 axis suppresses systemic inflammation, suggesting a potential therapeutic approach for regulating inflammatory processes. Our findings thus demonstrate that adaptive responses in glucose metabolism contribute to macrophage migratory activity.

Migration to the inflamed tissue demands energy production in an increasingly hypoxic environment. Here the authors show that during migration, HIF1α-induced PDK1 uniquely adapts macrophage metabolism to mild hypoxia by promoting glycolysis while preserving cytochrome c oxidase activity.

Mild Heat Treatment Primes Human CD34(+) Cord Blood Cells for Migration Toward SDF-1α and Enhances Engraftment in an NSG Mouse Model

Simple efforts are needed to enhance cord blood (CB) transplantation. We hypothesized that short-term exposure of CD34(+) CB cells to 39.5°C would enhance their response to stromal-derived factor-1 (SDF-1), by increasing lipid raft aggregation and CXCR4 expression, thus leading to enhanced engraftment. Mild hyperthermia (39.5°C) significantly increased the percent of CD34(+) CB that migrated toward SDF-1. This was associated with increased expression of CXCR4 on the cells. Mechanistically, mild heating increased the percent of CD34(+) cells with aggregated lipid rafts and enhanced colocalization of CXCR4 within lipid raft domains. Using methyl-β-cyclodextrin (MβCD), an agent that blocks lipid raft aggregation, it was determined that this enhancement in chemotaxis was dependent upon lipid raft aggregation. Colocalization of Rac1, a GTPase crucial for cell migration and adhesion, with CXCR4 to the lipid raft was essential for the effects of heat on chemotaxis, as determined with an inhibitor of Rac1 activation, NSC23766. Application-wise, mild heat treatment significantly increased the percent chimerism as well as homing and engraftment of CD34(+) CB cells in sublethally irradiated non-obese diabetic severe combined immunodeficiency IL-2 receptor gamma chain d (NSG) mice. Mild heating may be a simple and inexpensive means to enhance engraftment following CB transplantation in patients.

SDF-1/CXCL12 modulates mitochondrial respiration of immature blood cells in a bi-phasic manner

SDF-1/CXCL12 is a potent chemokine required for the homing and engraftment of hematopoietic stem and progenitor cells. Previous data from our group has shown that in an SDF-1/CXCL12 transgenic mouse model, lineage(-) Sca-1(+) c-Kit(+) (LSK) bone marrow cells have reduced mitochondrial membrane potential versus wild-type. These results suggested that SDF-1/CXCL12 may function to keep mitochondrial respiration low in immature blood cells in the bone marrow. Low mitochondrial metabolism helps to maintain low levels of reactive oxygen species (ROS), which can influence differentiation. To test whether SDF-1/CXCL12 regulates mitochondrial metabolism, we employed the human leukemia cell line HL-60, that expresses high levels of the SDF-1/CXCL12 receptor, CXCR4, as a model of hematopoietic progenitor cells in vitro. We treated HL-60 cells with SDF-1/CXCL12 for 2 and 24h. Oxygen consumption rates (OCR), mitochondrial-associated ATP production, mitochondrial mass, and mitochondrial membrane potential of HL-60 cells were significantly reduced at 2h and increased at 24h as compared to untreated control cells. These biphasic effects of SDF-1/CXCL12 were reproduced with lineage negative primary mouse bone marrow cells, suggesting a novel function of SDF-1/CXCL12 in modulating mitochondrial respiration by regulating mitochondrial oxidative phosphorylation, ATP production and mitochondrial content.

Dimethyl Sulfoxide (DMSO) Increases Percentage of CXCR4(+) Hematopoietic Stem/Progenitor Cells, Their Responsiveness to an SDF-1 Gradient, Homing Capacities, and Survival

Cryopreservation of bone marrow (BM), mobilized peripheral blood (mPB), and cord blood (CB) hematopoietic stem/progenitor cells (HSPCs) is a routine procedure before transplantation. The most commonly used cryoprotectant for HSPCs is dimethyl sulfoxide (DMSO). The objective of this study was to evaluate the influence of DMSO on surface receptor expression and chemotactic activities of HSPCs. We found that 10 min of incubation of human mononuclear cells (MNCs) with 10% DMSO significantly increases the percentage of CXCR4(+), CD38(+), and CD34(+) cells, resulting in an increase of CD34(+), CD34(+)CXCR4(+), and CD34(+)CXCR4(+)CD38(-) subpopulations. Furthermore, DMSO significantly increased chemotactic responsiveness of MNCs and CXCR4(+) human hematopoietic Jurkat cell line to a stromal cell-derived factor-1 (SDF-1) gradient. Furthermore, we demonstrated enhanced chemotaxis of human clonogenic progenitor cells to an SDF-1 gradient, which suggests that DMSO directly enhances the chemotactic responsiveness of early human progenitors. DMSO preincubation also caused lower internalization of the CXCR4 receptor. In parallel experiments, we found that approximately 30% more of DMSO-preincubated human CD45(+) and CD45(+)CD34(+) cells homed to the mouse BM 24 h after transplantation in comparison to control cells. Finally, we demonstrated considerably higher (25 days) survival of mice transplanted with DMSO-exposed MNCs than those transplanted with the control cells. We show in this study an unexpected beneficial influence of DMSO on HSPC homing and suggest that a short priming with DMSO before transplantation could be considered a new strategy to enhance cell homing and engraftment.

Superior long-term repopulating capacity of G-CSF+plerixafor-mobilized blood: implications for stem cell gene therapy by studies in the Hbb(th-3) mouse model

High numbers of genetically modified hematopoietic stem cells (HSCs) equipped with enhanced engrafting potential are required for successful stem cell gene therapy. By using thalassemia as a model, we investigated the functional properties of hematopoietic stem and progenitor cells (HSPCs) from Hbb(th3)/45.2(+) mice after mobilization with G-CSF, plerixafor, or G-CSF+plerixafor and the engraftment kinetics of primed cells after competitive primary and noncompetitive secondary transplantation. G-CSF+plerixafor yielded the highest numbers of HSPCs, while G-CSF+plerixafor-mobilized Hbb(th3)/45.2(+) cells, either unmanipulated or transduced with a reporter vector, achieved faster hematologic reconstitution and higher levels of donor chimerism over all other types of mobilized cells, after competitive transplantation to B6.BoyJ/45.1(+) recipients. The engraftment benefit observed in the G-CSF+plerixafor group was attributed to the more primitive stem cell phenotype of G-CSF+plerixafor-LSK cells, characterized by higher CD150(+)/CD48 expression. Moreover, secondary G-CSF+plerixafor recipients displayed stable or even higher chimerism levels as compared with primary engrafted mice, thus maintaining or further improving engraftment levels over G-CSF- or plerixafor-secondary recipients. Plerixafor-primed cells displayed the lowest competiveness over all other mobilized cells after primary or secondary transplantation, probably because of the higher frequency of more actively proliferating LK cells. Overall, the higher HSC yields, the faster hematological recovery, and the superiority in long-term engraftment indicate G-CSF+plerixafor-mobilized blood as an optimal graft source, not only for thalassemia gene therapy, but also for stem cell gene therapy applications in general.

Retinoic Acid Differentially Regulates the Migration of Innate Lymphoid Cell Subsets to the Gut

Distinct groups of innate lymphoid cells (ILCs) such as ILC1, ILC2, and ILC3 populate the intestine, but how these ILCs develop tissue tropism for this organ is unclear. We report that prior to migration to the intestine ILCs first undergo a "switch" in their expression of homing receptors from lymphoid to gut homing receptors. This process is regulated by mucosal dendritic cells and the gut-specific tissue factor retinoic acid (RA). This change in homing receptors is required for long-term population and effector function of ILCs in the intestine. Only ILC1 and ILC3, but not ILC2, undergo the RA-dependent homing receptor switch in gut-associated lymphoid tissues. In contrast, ILC2 acquire gut homing receptors in a largely RA-independent manner during their development in the bone marrow and can migrate directly to the intestine. Thus, distinct programs regulate the migration of ILC subsets to the intestine for regulation of innate immunity.

Human Tfh and Tfr cells: identification and assessment of their migration potential

The ability of follicular T cells to migrate into B-cell follicles is central for them to participate in germinal center responses. The chemokine receptor CXCR5 is expressed by both Tfh and Tfr cells and is the defining marker for follicular T cells. In addition, Tfh and Tfr cells express additional chemokine receptors to enable them to interact with B cells and other cell types. CXCR5(+) Tfh and Tfr cells are divided into CCR7(+) perifollicular cells and CCR7(-) follicular cells. Most of the CXCR5(+) CCR7(-) Tfh cells reside in germinal centers and are called GC T cells. The methods to identify human Tfh and Tfr cell subsets based on chemokine receptors and other antigens and assess their migration potential are provided in this article.

Advances in umbilical cord blood manipulation-from niche to bedside

The use of umbilical cord blood (UCB) as an alternative haematopoietic cell source in lieu of bone marrow for haematopoietic reconstitution is increasingly becoming a mainstay treatment for both malignant and nonmalignant diseases, as most individuals will have at least one available, suitably HLA-matched unit of blood. The principal limitation of UCB is the low and finite number of haematopoietic stem and progenitor cells (HSPC) relative to the number found in a typical bone marrow or mobilized peripheral blood allograft, which leads to prolonged engraftment times. In an attempt to overcome this obstacle, strategies that are often based on native processes occurring in the bone marrow microenvironment or 'niche' have been developed with the goal of accelerating UCB engraftment. In broad terms, the two main approaches have been either to expand UCB HSPC ex vivo before transplantation, or to modulate HSPC functionality to increase the efficiency of HSPC homing to the bone marrow niche after transplant both of which enhance the biological activities of the engrafted HSPC. Several early phase clinical trials of these approaches have reported promising results.

SDF-1 inhibition targets the bone marrow niche for cancer therapy

Bone marrow (BM) metastasis remains one of the main causes of death associated with solid tumors as well as multiple myeloma (MM). Targeting the BM niche to prevent or modulate metastasis has not been successful to date. Here, we show that stromal cell-derived factor-1 (SDF-1/CXCL12) is highly expressed in active MM, as well as in BM sites of tumor metastasis and report on the discovery of the high-affinity anti-SDF-1 PEGylated mirror-image l-oligonucleotide (olaptesed-pegol). In vivo confocal imaging showed that SDF-1 levels are increased within MM cell-colonized BM areas. Using in vivo murine and xenograft mouse models, we document that in vivo SDF-1 neutralization within BM niches leads to a microenvironment that is less receptive for MM cells and reduces MM cell homing and growth, thereby inhibiting MM disease progression. Targeting of SDF-1 represents a valid strategy for preventing or disrupting colonization of the BM by MM cells.