Stromal-derived factor-1/CXCR4 signaling: indispensable role in homing and engraftment of hematopoietic stem cells in bone marrow

A Multifunctional Nanostructured Hydrogel as a Platform for Deciphering Niche Interactions of Hematopoietic Stem and Progenitor Cells

For over half a century, hematopoietic stem cells (HSCs) have been used for transplantation therapy to treat severe hematologic diseases. Successful outcomes depend on collecting sufficient donor HSCs as well as ensuring efficient engraftment. These processes are influenced by dynamic interactions of HSCs with the bone marrow niche, which can be revealed by artificial niche models. Here, a multifunctional nanostructured hydrogel is presented as a 2D platform to investigate how the interdependencies of cytokine binding and nanopatterned adhesive ligands influence the behavior of human hematopoietic stem and progenitor cells (HSPCs). The results indicate that the degree of HSPC polarization and motility, observed when cultured on gels presenting the chemokine SDF-1α and a nanoscale-defined density of a cellular (IDSP) or extracellular matrix (LDV) α4β1 integrin binding motif, are differently influenced on hydrogels functionalized with the different ligand types. Further, SDF-1α promotes cell polarization but not motility. Strikingly, the degree of differentiation correlates negatively with the nanoparticle spacing, which determines ligand density, but only for the cellular-derived IDSP motif. This mechanism potentially offers a means of predictably regulating early HSC fate decisions. Consequently, the innovative multifunctional hydrogel holds promise for deciphering dynamic HSPC-niche interactions and refining transplantation therapy protocols.

Injectable decellularized extracellular matrix hydrogel promotes salivary gland regeneration via endogenous stem cell recruitment and suppression of fibrogenesis

Saliva is key to the maintenance of oral homeostasis. However, several forms of salivary gland (SG) disorders, followed by hyposalivation, often result in dental caries, oral infection, and decreased taste, which dramatically affect the quality of patient's life. Functional biomaterials hold great potential for tissue regeneration in damaged or dysfunctional SGs and maintaining the good health of oral cavity. Herein, we prepared an injectable hydrogel derived from decellularized porcine submandibular glands (pDSG-gel), the material and biological properties of the hydrogel were systematically investigated. First, good biocompatibility and bioactivities of the pDSG-gel were validated in 2D and 3D cultures of primary submandibular gland mesenchymal stem cells (SGMSCs). Especially, the pDSG-gel effectively facilitated SGMSCs migration and recruitment through the activation of PI3K/AKT signaling pathway, suggested by transcriptomic analysis and immunoblotting. Furthermore, proteomic analysis of the pDSG revealed that many extracellular matrix components and secreted factors were preserved, which may contribute to stem cell homing. The recruitment of endogenous SG cells was confirmed in vivo, upon in situ injection of the pDSG-gel into the defective SGs in rats. Acinar and ductal-like structures were evident in the injury sites after pDSG-gel treatment, suggesting the reconstruction of functional SG units. Meanwhile, histological characterizations showed that the administration of the pDSG-gel also significantly suppressed fibrogenesis within the injured SG tissues. Taken together, this tissue-specific hydrogel provides a pro-regenerative microenvironment for endogenous SG regeneration and holds great promise as a powerful and bioactive material for future treatments of SG diseases. STATEMENT OF SIGNIFICANCE: Decellularized extracellular matrix (dECM) has been acknowledged as one of the most promising biomaterials that recapitalizes the microenvironment in native tissues. Hydrogel derived from the dECM allows in situ administration for tissue repair. Herein, a tissue-specific dECM hydrogel derived from porcine salivary glands (pDSG-gel) was successfully prepared and developed for functional reconstruction of defective salivary gland (SG) tissues. The pDSG-gel effectively accelerated endogenous SG stem cells migration and their recruitment for acinar- and ductal-like regeneration, which was attributed to the activation of PI3K/AKT signaling pathway. Additionally, the introduction of the pDSG-gel resulted in highly suppressed fibrogenesis in the defective tissues. These outcomes indicated that the pDSG-gel holds great potential in clinical translation toward SG regeneration through cell-free treatments.

Graft conditioning with fluticasone propionate reduces graft-versus-host disease upon allogeneic hematopoietic cell transplantation in mice

Hematopoietic cell transplantation (HCT) treats many blood conditions but remains underused due to complications such as graft-versus-host disease (GvHD). In GvHD, donor immune cells attack the patient, requiring powerful immunosuppressive drugs like glucocorticoids (GCs) to prevent death. In this study, we tested the hypothesis that donor cell conditioning with the glucocorticoid fluticasone propionate (FLU) prior to transplantation could increase hematopoietic stem cell (HSC) engraftment and reduce GvHD. Murine HSCs treated with FLU had increased HSC engraftment and reduced severity and incidence of GvHD after transplantation into allogeneic hosts. While most T cells died upon FLU treatment, donor T cells repopulated in the hosts and appeared less inflammatory and alloreactive. Regulatory T cells (Tregs) are immunomodulatory and survived FLU treatment, resulting in an increased ratio of Tregs to conventional T cells. Our results implicate an important role for Tregs in maintaining allogeneic tolerance in FLU-treated grafts and suggest a therapeutic strategy of pre-treating donor cells (and not the patients directly) with GCs to simultaneously enhance engraftment and reduce GvHD upon allogeneic HCT.

Efficacy of Rectal Systemic Administration of Mesenchymal Stem Cells to Injury Sites via the CXCL12/CXCR4 Axis to Promote Regeneration in a Rabbit Skeletal Muscle Injury Model

Mesenchymal stem cells (MSCs) have been transplanted directly into lesions or injected intravenously. The administration of MSCs using these delivery methods requires specialized knowledge, techniques, and facilities. Here, we describe intrarectal systemic administration of MSCs, a simple, non-invasive route for homing to the injury sites to promote the regeneration of skeletal muscle injuries. Using a cardiotoxin (CTX)-induced rabbit skeletal muscle injury model, homing to the site of muscle injury was confirmed by intrarectal administration of MSCs; the time required for homing after intrarectal administration was approximately 5 days. In addition, the C-X-C chemokine ligand 12 (CXCL12)/C-X-C chemokine receptor-4 (CXCR4) axis was found to be involved in the homing process. Histopathological examinations showed that skeletal muscle regeneration was promoted in the MSCs-administered group compared to the CTX-only group. Myosin heavy polypeptide 3 (Myh3) expression, an indicator of early muscle regeneration, was detected earlier in the intrarectal MSCs group compared to the CTX-only group. These findings indicate that intrarectal administration of MSCs is effective in homing to the injured area, where they promote injury repair. Since intrarectal administration is a simple and non-invasive delivery route, these findings may be valuable in future research on stem cell therapy.

Magnetically empowered bone marrow cells as a micro-living motor can improve early hematopoietic reconstitution

BACKGROUND AIMS

Bone marrow-derived hematopoietic stem cell transplantation/hematopoietic progenitor cell transplantation (HSCT/HPCT) is widely used and one of the most useful treatments in clinical practice. However, the homing rate of hematopoietic stem cells/hematopoietic progenitor cells (HSCs/HPCs) by routine cell transfusion is quite low, influencing hematopoietic reconstitution after HSCT/HPCT.

METHODS

The authors developed a micro-living motor (MLM) strategy to increase the number of magnetically empowered bone marrow cells (ME-BMCs) homing to the bone marrow of recipient mice.

RESULTS

In the in vitro study, migration and retention of ME-BMCs were greatly improved in comparison with non-magnetized bone marrow cells, and the biological characteristics of ME-BMCs were well maintained. Differentially expressed gene analysis indicated that ME-BMCs might function through gene regulation. In the in vivo study, faster hematopoietic reconstitution was observed in ME-BMC mice, which demonstrated a better survival rate and milder symptoms of acute graft-versus-host disease after transplantation of allogeneic ME-BMCs.

CONCLUSIONS

This study demonstrated that ME-BMCs serving as MLMs facilitated the homing of HSCs/HPCs and eventually contributed to earlier hematopoietic reconstitution in recipients. These data might provide useful information for other kinds of cell therapies.

Therapeutic Perspectives of HIV-Associated Chemokine Receptor (CCR5 and CXCR4) Antagonists in Carcinomas

The interaction between malignant cells and the tumor microenvironment is critical for tumor progression, and the chemokine ligand/receptor axes play a crucial role in this process. The CXCR4/CXCL12 and CCR5/CCL5 axes, both related to HIV, have been associated with the early (epithelial-mesenchymal transition and invasion) and late events (migration and metastasis) of cancer progression. In addition, these axes can also modulate the immune response against tumors. Thus, antagonists against the receptors of these axes have been proposed in cancer therapy. Although preclinical studies have shown promising results, clinical trials are needed to include these drugs in the oncological treatment protocols. New alternatives for these antagonists, such as dual CXCR4/CCR5 antagonists or combined therapy in association with immunotherapy, need to be studied in cancer therapy.

The road of NSCLC stem cells toward bone metastases

Despite advancement in therapeutic options, Non-Small Cell lung cancer (NSCLC) remains a lethal disease mostly due to late diagnosis at metastatic phase and drug resistance. Bone is one of the more frequent sites for NSCLC metastatization. A defined subset of cancer stem cells (CSCs) that possess motile properties, mesenchymal features and tumor initiation potential are defined as metastasis initiating cells (MICs). A better understanding of the mechanisms supporting MIC dissemination and interaction with bone microenvironment is fundamental to design novel rational therapeutic option for long lasting efficient treatment of NSCLC. In this review we will summarize findings about bone metastatic process initiated by NSCLC MICs. We will review how MICs can reach bone and interact with its microenvironment that supports their extravasation, seeding, dormancy/proliferation. The role of different cell types inside the bone metastatic niche, such as endothelial cells, bone cells, hematopoietic stem cells and immune cells will be discussed in regards of their impact in dictating the success of metastasis establishment by MICs. Finally, novel therapeutic options to target NSCLC MIC-induced bone metastases, increasing the survival of patients, will be presented.

Chemokine level predicts the therapeutic effect of anti-PD-1 antibody (nivolumab) therapy for malignant melanoma

Anti-programmed cell death protein 1 (PD-1) antibody drugs, nivolumab and pembrolizumab, are regarded as first-line therapies for advanced malignant melanoma. Anti-PD-1 therapy suppresses tumor immunity, and the therapeutic effect is frequently correlated with the number of tumor-infiltrating lymphocytes (TIL) and tumor mutation burden (TMB). However, sampling tumor tissues from the metastatic sites to examine the number of TILs and TMB level is often challenging. Herein, we focused on chemokines in blood to determine whether they can predict the therapeutic effect of anti-PD-1 (nivolumab) therapy. First, we measured 44 types of chemokines and cytokines in the blood of 8 advanced malignant melanomas before anti-PD-1 (nivolumab) treatment and examined the relationship between the levels of these proteins and therapeutic effect of the drug treatment, which suggested that C-C motif chemokine 5 (CCL5) and C-X-C motif chemokine ligand 12 (CXCL12) were candidates for biomarkers to predict the therapeutic effect of anti-PD-1 therapy. Next, we measured the blood levels of CCL5 and CXCL12 in 22 patients with advanced malignant melanomas before the administration of anti-PD-1 antibody. We evaluated tumor infiltration of CD8-positive T cells by immunostaining in nine patients in whom the metastatic site could be sampled at the beginning of the treatment. The patients with lower than average levels of CCL5 and CXCL12 had a large number of TILs (P = 0.04) and good disease-specific survival rate (P = 0.04). Therefore, CCL5 and CXCL12 could likely be used as biomarkers to predict the therapeutic effect of anti-PD-1 (nivolumab) therapy.

Asymmetric T cell division of GAD65 specific naive T cells contribute to an early divergence in the differentiation fate into memory T cell subsets

Autoreactive T cells with the phenotype and function of different memory subsets are present in patients who developed type 1 diabetes. According to the progressive differentiation model, memory subsets generate from naïve precursors in a linear and unidirectional path depending on the strength and quality of stimulatory signals. By observing human naïve T cells in contact with GAD65 loaded autologous dendritic cells, we observed that approximately 10% of cells divided with the plane of cell division parallel to the one of the immune synapse, causing phenotypic asymmetries in the proximal and distal daughter T cells. After the first T cell division, proximal and distal daughter T cells showed different phenotype, metabolic signature and commitment to differentiate toward long-lived memory T cells or T cells with effector function. Subjects with or without T1D showed a similar frequency of asymmetric T cell division (ATCD) for autoantigens and recall antigens specific T cells, however the frequency of ATCD is significantly increased in autoreactive T cells in patients with T1D when IL-7 was added to the culture. An increased up-regulation of GLUT1 in response to IL-7 in patients with T1D was related to the rate of ATCD Our results showed that ATCD is associated with an early divergence in the differentiation fate of naïve T cells specific for GAD65 during first antigen encounter. This article is protected by copyright. All rights reserved.

Chemokine C-X-C receptor 4 mediates recruitment of bone marrow-derived nonhematopoietic and immune cells to the pregnant uterus†

Bone marrow-derived progenitor cells (BMDPCs) are mobilized to the circulation in pregnancy and get recruited to the pregnant decidua where they contribute functionally to decidualization and successful implantation. However, the molecular mechanisms underlying BMDPCs recruitment to the decidua are unknown. CXCL12 ligand and its CXCR4 receptor play crucial roles in the mobilization and homing of stem/progenitor cells to various tissues. To investigate the role of CXCL12-CXCR4 axis in BMDPCs recruitment to decidua, we created transgenic GFP mice harboring CXCR4 gene susceptible to tamoxifen-inducible Cre-mediated ablation. These mice served as BM donors into wild-type C57BL/6 J female recipients using a 5-fluorouracil-based nongonadotoxic submyeloablation to achieve BM-specific CXCR4 knockout (CXCR4KO). Successful CXCR4 ablation was confirmed by RT-PCR and in vitro cell migration assays. Flow cytometry and immunohistochemistry showed a significant increase in GFP+ BM-derived cells (BMDCs) in the implantation site as compared to the nonpregnant uterus of control (2.7-fold) and CXCR4KO (1.8-fold) mice. This increase was uterus-specific and was not observed in other organs. This pregnancy-induced increase occurred in both hematopoietic (CD45+) and nonhematopoietic (CD45-) uterine BMDCs in control mice. In contrast, in CXCR4KO mice there was no increase in nonhematopoietic BMDCs in the pregnant uterus. Moreover, decidual recruitment of myeloid cells but not NK cells was diminished by BM CXCR4 deletion. Immunofluorescence showed the presence of nonhematopoietic GFP+ cells that were negative for CD45 (panleukocyte) and DBA (NK) markers in control but not CXCR4KO decidua. In conclusion, we report that CXCR4 expression in nonhematopoietic BMDPCs is essential for their recruitment to the pregnant decidua.

CRISPR-Cas9-mediated gene disruption of HIV-1 co-receptors confers broad resistance to infection in human T cells and humanized mice

In this preclinical study, we evaluated the efficacy and feasibility of creating broad human immunodeficiency virus (HIV) resistance by simultaneously disrupting the human CCR5 and CXCR4 genes, which encode cellular co-receptors required for HIV-1 infection. Using a clinically scalable system for transient ex vivo delivery of Cas9/guide RNA (gRNA) ribonucleoprotein (RNP) complexes, we demonstrated that CRISPR-mediated disruption of CCR5 and CXCR4 in T lymphocyte cells significantly reduced surface expression of the co-receptors, thereby establishing resistance to HIV-1 infection by CCR5 (R5)-tropic, CXCR4 (X4)-tropic, and dual (R5/X4)-tropic strains. Similarly, disruption of CCR5 alleles in human CD34⁺ hematopoietic stem and progenitor cells (HSPCs) successfully led to the differentiation of HIV-resistant macrophages. In a humanized mouse model under HIV-1 challenge, CXCR4-disrupted CD4⁺ T cells were enriched in the peripheral blood and spleen, indicating survival advantage because of resistance to viral infection. However, in human CD4⁺ T cells with both CCR5 and CXCR4 disruption, we observed poor engraftment in bone marrow, although significant changes were not observed in the lung, spleen, or peripheral blood. This study establishes a clinically scalable strategy for the dual knockout of HIV-1 co-receptors as a therapeutic strategy, while also raising caution of disrupting CXCR4, which may abate engraftment of CD4⁺ T cells in bone marrow.

Ginsenoside Rg1 as a Potential Regulator of Hematopoietic Stem/Progenitor Cells

Ginsenoside Rg1 (Rg1), a purified, active component of the root or stem of ginseng, exerts positive effects on mesenchymal stem cells (MSCs). Many recent studies have found that hematopoietic stem cells (HSCs), which can develop into hematopoietic progenitor cells (HPCs) and mature blood cells, are another class of heterogeneous adult stem cells that can be regulated by Rg1. Rg1 can affect HSC proliferation and migration, regulate HSC/HPC differentiation, and alleviate HSC aging, and these findings potentially provide new strategies to improve the HSC homing rate in HSC transplantation and for the treatment of graft-versus-host disease (GVHD) or other HSC/HPC dysplasia-induced diseases. In this review, we used bioinformatics methods, molecular docking verification, and a literature review to systematically explore the possible molecular pharmacological activities of Rg1 through which it regulates HSCs/HPCs.

Regenerative Medicine for the Treatment of Ischemic Heart Disease; Status and Future Perspectives

Cardiovascular disease is now the leading cause of adult death in the world. According to new estimates from the World Health Organization, myocardial infarction (MI) is responsible for four out of every five deaths due to cardiovascular disease. Conventional treatments of MI are taking aspirin and nitroglycerin as intermediate treatments and injecting antithrombotic agents within the first 3 h after MI. Coronary artery bypass grafting and percutaneous coronary intervention are the most common long term treatments. Since none of these interventions will fully regenerate the infarcted myocardium, there is value in pursuing more innovative therapeutic approaches. Regenerative medicine is an innovative interdisciplinary method for rebuilding, replacing, or repairing the missed part of different organs in the body, as similar as possible to the primary structure. In recent years, regenerative medicine has been widely utilized as a treatment for ischemic heart disease (one of the most fatal factors around the world) to repair the lost part of the heart by using stem cells. Here, the development of mesenchymal stem cells causes a breakthrough in the treatment of different cardiovascular diseases. They are easily obtainable from different sources, and expanded and enriched easily, with no need for immunosuppressing agents before transplantation, and fewer possibilities of genetic abnormality accompany them through multiple passages. The production of new cardiomyocytes can result from the transplantation of different types of stem cells. Accordingly, due to its remarkable benefits, stem cell therapy has received attention in recent years as it provides a drug-free and surgical treatment for patients and encourages a more safe and feasible cardiac repair. Although different clinical trials have reported on the promising benefits of stem cell therapy, there is still uncertainty about its mechanism of action. It is important to conduct different preclinical and clinical studies to explore the exact mechanism of action of the cells. After reviewing the pathophysiology of MI, this study addresses the role of tissue regeneration using various materials, including different types of stem cells. It proves some appropriate data about the importance of ethical problems, which leads to future perspectives on this scientific method.

Pharmacological Inhibition of p38 MAPK Rejuvenates Bone Marrow Derived-Mesenchymal Stromal Cells and Boosts their Hematopoietic Stem Cell-Supportive Ability

The therapeutic value of mesenchymal stromal cells (MSCs) for various regenerative medicine applications, including hematopoietic stem cell transplantations (HSCT), has been well-established. Owing to their small numbers in vivo, it becomes necessary to expand them in vitro, which leads to a gradual loss of their regenerative capacity. Stress-induced mitogen-activated protein kinase p38 (p38 MAPK) signaling has been shown to compromise the MSC functions. Therefore, we investigated whether pharmacological inhibition of p38 MAPK signaling rejuvenates the cultured MSCs and boosts their functionality. Indeed, we found that the ex vivo expanded MSCs show activated p38 MAPK signaling and exhibit increased oxidative stress. These MSCs show a decreased ability to secrete salutary niche factors, thereby compromising their ability to support hematopoietic stem cell (HSC) self-renewal, proliferation, and differentiation. We, therefore, attempted to rejuvenate the cultured MSCs by pharmacological inhibition of p38 MAPK - a strategy broadly known as "priming of MSCs". We demonstrate that priming of MSCs with a p-38 MAPK inhibitor, PD169316, boosts their niche-supportive functions via upregulation of various HSC-supportive transcription factors. These primed MSCs expand multipotent HSCs having superior homing and long-term reconstitution ability. These findings shed light on the significance of non-cell-autonomous mechanisms operative in the hematopoietic niche and point towards the possible use of pharmacological compounds for rejuvenation of ex vivo cultured MSCs. Such approaches could improve the outcome of regenerative therapies involving in vitro cultured MSCs.

Curcumin restores the engraftment capacity of aged hematopoietic stem cells and also reduces PD-1 expression on cytotoxic T cells

Aging affects the functionality of hematopoietic stem cells (HSCs), and therefore, aged individuals are not preferred as donors in HSC transplantation. Such elimination leads to the restriction of donor cohort. Several efforts are being done to rejuvenate aged HSCs. Here, we show that treatment of aged mice with curcumin rejuvenates their HSCs by restoring the expression of autophagy-inducing messenger RNAs in them, and improves their engraftment capacity. Importantly, we show that curcumin is effective in rejuvenation of HSCs when administered via both, intraperitoneal as well as oral routes. Aging also affects the immune system. While elderly individuals are not immuno-deficient, they do not respond optimally to immunizations, and hence, a strategy needs to be developed to make them immunologically responsive. Programmed cell death 1 (PD-1), one of the inhibitory coreceptors, plays an important role in the regulation of autoimmunity, infectious immunity, and cancer immunity. Its expression on T cells is indicative of their exhaustion. Here, we show that curcumin reduces the frequency of PD1+ cytotoxic T cells in the spleens of aged mice. Curcumin has a proven safety profile, and hence, can be used to treat aged donors to boost the functionality of their HSCs and also to improve the immunological profile of aged individuals. These data could have implications in various other regenerative medicine protocols as well.

Enhanced anti-inflammatory effects of mesenchymal stromal cells mediated by the transient ectopic expression of CXCR4 and IL10

Background

Mesenchymal stromal cells (MSCs) constitute one of the cell types most frequently used in cell therapy. Although several studies have shown the efficacy of these cells to modulate inflammation in different animal models, the results obtained in human clinical trials have been more modest. Here, we aimed at improving the therapeutic properties of MSCs by inducing a transient expression of two molecules that could enhance two different properties of these cells. With the purpose of improving MSC migration towards inflamed sites, we induced a transient expression of the C-X-C chemokine receptor type 4 (CXCR4). Additionally, to augment the anti-inflammatory properties of MSCs, a transient expression of the anti-inflammatory cytokine, interleukin 10 (IL10), was also induced.

Methods

Human adipose tissue-derived MSCs were transfected with messenger RNAs carrying the codon-optimized versions of CXCR4 and/or IL10. mRNA-transfected MSCs were then studied, first to evaluate whether the characteristic phenotype of MSCs was modified. Additionally, in vitro and also in vivo studies in an LPS-induced inflamed pad model were conducted to evaluate the impact associated to the transient expression of CXCR4 and/or IL10 in MSCs.

Results

Transfection of MSCs with CXCR4 and/or IL10 mRNAs induced a transient expression of these molecules without modifying the characteristic phenotype of MSCs. In vitro studies then revealed that the ectopic expression of CXCR4 significantly enhanced the migration of MSCs towards SDF-1, while an increased immunosuppression was associated with the ectopic expression of IL10. Finally, in vivo experiments showed that the co-expression of CXCR4 and IL10 increased the homing of MSCs into inflamed pads and induced an enhanced anti-inflammatory effect, compared to wild-type MSCs.

Conclusions

Our results demonstrate that the transient co-expression of CXCR4 and IL10 enhances the therapeutic potential of MSCs in a local inflammation mouse model, suggesting that these mRNA-modified cells may constitute a new step in the development of more efficient cell therapies for the treatment of inflammatory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02193-0.

Competitive sgRNA Screen Identifies p38 MAPK as a Druggable Target to Improve HSPC Engraftment

Previous gene therapy trials for X-linked chronic granulomatous disease (X-CGD) lacked long-term engraftment of corrected hematopoietic stem and progenitor cells (HSPCs). Chronic inflammation and high levels of interleukin-1 beta (IL1B) might have caused aberrant cell cycling in X-CGD HSPCs with a concurrent loss of their long-term repopulating potential. Thus, we performed a targeted CRISPR-Cas9-based sgRNA screen to identify candidate genes that counteract the decreased repopulating capacity of HSPCs during gene therapy. The candidates were validated in a competitive transplantation assay and tested in a disease context using IL1B-challenged or X-CGD HSPCs. The sgRNA screen identified Mapk14 (p38) as a potential target to increase HSPC engraftment. Knockout of p38 prior to transplantation was sufficient to induce a selective advantage. Inhibition of p38 increased expression of the HSC homing factor CXCR4 and reduced apoptosis and proliferation in HSPCs. For potential clinical translation, treatment of IL1B-challenged or X-CGD HSPCs with a p38 inhibitor led to a 1.5-fold increase of donor cell engraftment. In summary, our findings demonstrate that p38 may serve as a potential druggable target to restore engraftment of HSPCs in the context of X-CGD gene therapy.

Switching Homes: How Cancer Moves to Bone

Bone metastases (BM) are a very common complication of the most prevalent human cancers. BM are extremely painful and may be life-threatening when associated with hypercalcaemia. BM can lead to kidney failure and cardiac arrhythmias and arrest, but why and how do cancer cells decide to "switch homes" and move to bone? In this review, we will present what answers science has provided so far, with focus on the molecular mechanisms and cellular aspects of well-established findings, such as the concept of "vicious cycle" and "osteolytic" vs. "osteosclerotic" bone metastases; as well as on novel concepts, such as cellular dormancy and extracellular vesicles. At the molecular level, we will focus on hypoxia-associated factors and angiogenesis, the Wnt pathway, parathyroid hormone-related peptide (PTHrP) and chemokines. At the supramolecular/cellular level, we will discuss tumour dormancy, id est the mechanisms through which a small contingent of tumour cells coming from the primary site may be kept dormant in the endosteal niche for many years. Finally, we will present a potential role for the multimolecular mediators known as extracellular vesicles in determining bone-tropism and establishing a premetastatic niche by influencing the bone microenvironment.

Isolation and characterisation of nasoseptal cartilage stem/progenitor cells and their role in the chondrogenic niche

BACKGROUND

Since cartilage-derived stem/progenitor cells (CSPCs) were first identified in articular cartilage using differential adhesion to fibronectin, their self-renewal capacity and niche-specific lineage preference for chondrogenesis have propelled their application for cartilage tissue engineering. In many adult tissues, stem/progenitor cells are recognised to be involved in tissue homeostasis. However, the role of nasoseptal CSPCs has not yet been elucidated. Our aim was to isolate and characterise nasoseptal CSPCs alongside nasoseptal chondrocyte populations and determine chondrogenic capacity.

METHODS

Here, we isolated nasoseptal CSPCs using differential adhesion to fibronectin and assessed their colony forming efficiency, proliferation kinetics, karyotype and trilineage potential. CSPCs were characterised alongside non-fibronectin-adherent nasoseptal chondrocytes (DNCs) and cartilage-derived cells (CDCs, a heterogenous combination of DNCs and CSPCs) by assessing differences in gene expression profiles using PCR Stem Cell Array, immunophenotype using flow cytometry and chondrogencity using RT-PCR and histology.

RESULTS

CSPCs were clonogenic with increased gene expression of the neuroectodermal markers NCAM1 and N-Cadherin, as well as Cyclins D1 and D2, compared to DNCs. All three cell populations expressed recognised mesenchymal stem cell surface markers (CD29, CD44, CD73, CD90), yet only CSPCs and CDCs showed multilineage differentiation potential. CDC populations expressed significantly higher levels of type 2 collagen and bone morphogenetic protein 2 genes, with greater cartilage extracellular matrix secretion. When DNCs were cultured in isolation, there was reduced chondrogenicity and higher expression of type 1 collagen, stromal cell-derived factor 1 (SDF-1), CD73 and CD90, recognised markers of a fibroblast-like phenotype.

CONCLUSIONS

Fibronectin-adherent CSPCs demonstrate a unique gene expression profile compared to non-fibronectin-adherent DNCs. DNCs cultured in isolation, without CSPCs, express fibroblastic phenotype with reduced chondrogenicity. Mixed populations of stem/progenitor cells and chondrocytes were required for optimal chondrogenesis, suggesting that CSPCs may be required to retain phenotypic stability and chondrogenic potential of DNCs. Crosstalk between DNCs and CSPCs is proposed based on SDF-1 signalling.

Emerging strategies for enhancing the homing of hematopoietic stem cells to the bone marrow after transplantation

Bone marrow failure is the primary cause of death after nuclear accidents or intentional exposure to high or low doses of ionizing radiation. Hematopoietic stem cell transplantation is the most potent treatment procedure for patients suffering from several hematopoietic malignancies arising after radiation injuries. Successful hematopoietic recovery after transplantation depends on efficient homing and subsequent engraftment of hematopoietic stem cells in specific niches within the bone marrow. It is a rapid and coordinated process in which circulating cells actively enter the bone marrow through the process known as transvascular migration, which involves the tightly regulated relay of events that finally leads to homing of cells in the bone marrow. Various adhesion molecules, chemokines, glycoproteins, integrins, present both on the surface of stem cells and sinusoidal endothelium plays a critical role in transvascular migration. But despite having an in-depth knowledge of homing and engraftment and the key events that regulate it, we are still not completely able to avoid graft failures and post-transplant mortalities. This deems it necessary to design a flawless plan for successful transplantation. Here, in this review, we will discuss the current clinical methods used to overcome graft failures and their flaws. We will also discuss, what are the new approaches developed in the past 10-12 years to selectively deliver the hematopoietic stem cells in the bone marrow by adopting proper targeting strategies that can help revolutionize the field of regenerative and translational medicine.

Evaluation of bone-regeneration effects and ectopic osteogenesis of collagen membrane chemically conjugated with stromal cell-derived factor-1 in vivo

Because the collagen membrane lacks osteoinductivity, it must be modified with bioactive components to trigger rapid bone regeneration. In this study, we aimed to evaluate the bone regeneration effects of a collagen membrane chemically conjugated with stromal cell-derived factor-1 alpha (SDF-1α) in rat models. To this end, different collagen membranes from four groups including a control group with a Bio-Oss bone substitute + collagen membrane; physical adsorption group with Bio-Oss + SDF-1α physically adsorbed on the collagen membrane; chemical cross-linking group with Bio-Oss + SDF-1α chemically cross-linked to the collagen membrane; and cell-seeding group with Bio-Oss + bone marrow mesenchymal stem cells (BMSCs) seeded onto the collagen membrane were placed in critical-sized defect models using a guided bone regeneration technique. At 4 and 8 weeks, the specimens were analyzed by scanning electron microscopy, energy-dispersive x-ray spectroscopy, micro-computed tomography, and histomorphology analyzes. Furthermore, ectopic osteogenesis was examined by histological analysis with Von Kossa staining, with the samples counterstained by hematoxylin and eosin and immunohistochemical staining. The results showed that in the chemical cross-linking group and cell-seeding group, the bone volume fraction, bone surface area fraction, and trabecular number were significantly increased and showed more new bone formation compared to the control and physical adsorption groups. Von Kossa-stained samples counterstained with hematoxylin and eosin and subjected to immunohistochemical staining of 4-week implanted membranes revealed that the chemical cross-linking group had the largest number of microvessels. The collagen membrane chemically conjugated with SDF-1α to significantly promote new bone and microvessel formation compared to SDF-1α physical adsorption and showed similar effects on new bone formation as a BMSC seeding method. This study provided a cell-free approach for shortening the bone healing time and improving the success rate of guided bone regeneration.

Intranasal delivery of SDF-1α-preconditioned bone marrow mesenchymal cells improves remyelination in the cuprizone-induced mouse model of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS) that leads to disability in middle-aged individuals. High rates of apoptosis and inappropriate homing are limitations for the application of stem cells in cell therapy. Preconditioning of bone marrow mesenchymal stem cells (BMSCs) with stromal cell-derived factor 1α (SDF-1α), also called C-X-C motif chemokine 12 (CXCL12), is an approach for improving the functional features of the cells. The aim of this study was to investigate the therapeutic efficacy of intranasal delivery of SDF-1α preconditioned BMSCs in the cuprizone-induced chronically demyelinated mice model. BMSCs were isolated, cultured, and preconditioned with SDF-1α. Then, intranasal delivery of the preconditioned cells was performed in the C57BL/6 mice receiving cuprizone for 12 weeks. Animals were killed at 30 days after cell delivery. SDF-1α preconditioning increased C-X-C chemokine receptor type 4 (CXCR4) expression on the surface of BMSCs, improved survival of the cells, and decreased their apoptosis in vitro. SDF-1α preconditioning also improved CXCL12 level within the brain, and enhanced spatial learning and memory (assessed by Morris water maze [MWM]), and myelination (assessed by Luxol fast blue [LFB] and transmission electron microscopy [TEM]). In addition, preconditioning of BMSCs with SDF-1α reduced the protein expressions of glial fibrillary acidic protein and ionized calcium-binding adapter molecule (Iba-1) and increased the expressions of oligodendrocyte lineage transcription factor-2 (Olig-2) and adenomatous polyposis coli (APC), evaluated by immunofluorescence. The results showed the efficacy of intranasal delivery of SDF-1α-preconditioned BMSCs for improving remyelination in the cuprizone model of MS.

Stromal cell-derived factor-1/CXC chemokine receptor 4 axis in injury repair and renal transplantation

Stem cell therapy has shown promise in treating a variety of pathologies, such as myocardial infarction, ischaemic stroke and organ transplantation. The stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) axis plays a key role in stem cell mobilization. This review describes the important role of SDF-1 in tissue injury and how it works in tissue revascularization and regeneration via CXCR4. Furthermore, factors influencing the SDF-1/CXCR4 axis and its clinical potential in ischaemia reperfusion injury, such as renal transplantation, are discussed. Exploring signalling pathways of the SDF-1/CXCR4 axis will contribute to the development of stem cell therapy so that more clinical problems can be solved. Controlling directional homing of stem cells through the SDF-1/CXCR4 axis is key to improving the efficacy of stem cell therapy for tissue injury. CXCR4 antagonists may also be effective in increasing circulating levels of adult stem cells, thereby exerting beneficial effects on damaged or inflamed tissues in diseases that are currently not treated by standard approaches.

Redistribution, homing and organ-invasion of neoplastic stem cells in myeloid neoplasms

The development of a myeloid neoplasm is a step-wise process that originates from leukemic stem cells (LSC) and includes pre-leukemic stages, overt leukemia and a drug-resistant terminal phase. Organ-invasion may occur in any stage, but is usually associated with advanced disease and a poor prognosis. Sometimes, extra-medullary organ invasion shows a metastasis-like or even sarcoma-like destructive growth of neoplastic cells in local tissue sites. Examples are myeloid sarcoma, mast cell sarcoma and localized blast phase of chronic myeloid leukemia. So far, little is known about mechanisms underlying re-distribution and extramedullary dissemination of LSC in myeloid neoplasms. In this article, we discuss mechanisms through which LSC can mobilize out of the bone marrow niche, can transmigrate from the blood stream into extramedullary organs, can invade local tissue sites and can potentially create or support the formation of local stem cell niches. In addition, we discuss strategies to interfere with LSC expansion and organ invasion by targeted drug therapies.

Stress and catecholamines modulate the bone marrow microenvironment to promote tumorigenesis

High vascularization and locally secreted factors make the bone marrow (BM) microenvironment particularly hospitable for tumor cells and bones to a preferred metastatic site for disseminated cancer cells of different origins. Cancer cell homing and proliferation in the BM are amongst other regulated by complex interactions with BM niche cells (e.g. osteoblasts, endothelial cells and mesenchymal stromal cells (MSCs)), resident hematopoietic stem and progenitor cells (HSPCs) and pro-angiogenic cytokines leading to enhanced BM microvessel densities during malignant progression. Stress and catecholamine neurotransmitters released in response to activation of the sympathetic nervous system (SNS) reportedly modulate various BM cells and may thereby influence cancer progression. Here we review the role of catecholamines during tumorigenesis with particular focus on pro-tumorigenic effects mediated by the BM niche.

Regulation of plasticity and biological features of endothelial progenitor cells by MSC-derived SDF-1

Bone marrow (BM) is a source of mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs). MSCs provide a specific niche in the BM and biological features of EPCs may be changed with this niche. Stromal cell-derived factor 1 (SDF-1) secreted from primary BM-MSCs and biological features of this niche on EPC development are still yet to be understood. The aim of this study was to evaluate the role of SDF-1 produced by MSCs on EPC development. We applied the CRISPR/Cas9 system for the knock-out of the SDF-1 gene in BM-derived MSCs. BM-derived EPCs were then cocultured with MSCs^SDF-1-/- or MSCs^SDF-1+/+ to identify the role of MSC-derived SDF-1α on proliferation, migration and angiogenic activity of EPCs. Next, pre-expanded EPCs were harvested and co-transplanted with MSCs^SDF-1-/- or MSCs^SDF-1+/+ into sublethally irradiated mice to analyze the potency of these cells for marrow reconstitution. Our results revealed that proliferation, colony formation, migration and angiogenic activity of EPCs was significantly increased after coculture with MSCs^SDF-1+/+. We also found that co-transplantation of EPCs with MSCs^SDF-1+/+, in contrast to MSCs^SDF-1-/-, into irradiated mice resulted in marrow repopulation and hematologic recovery, leading to improved survival of transplanted mice. In conclusions, MSC-derived SDF-1 niche plays an important role in the development of EPCs and this niche is essential for bone marrow repopulation by these cells and can enhance the efficiency of EPC therapy for ischemic diseases.

Stem Cell Homing: a Potential Therapeutic Strategy Unproven for Treatment of Myocardial Injury

Despite advances in the prevention and therapeutic modalities of ischemic heart disease, morbidity and mortality post-infarction heart failure remain big challenges in modern society. Stem cell therapy is emerging as a promising therapeutic strategy. Stem cell homing, the ability of stem cells to find their destination, is receiving more attention. Identification of specific cues and understanding the signaling pathways that direct stem cells to targeted destination will improve stem cell homing efficiency. This review discusses the cellular and molecular mechanism of stem cell homing at length in the light of literature and analyzes the problem and considerations of this approach as a treatment strategy for the treatment of ischemic heart disease clinically.

Ovarian Tumor Microenvironment Signaling: Convergence on the Rac1 GTPase

The tumor microenvironment for epithelial ovarian cancer is complex and rich in bioactive molecules that modulate cell-cell interactions and stimulate numerous signal transduction cascades. These signals ultimately modulate all aspects of tumor behavior including progression, metastasis and therapeutic response. Many of the signaling pathways converge on the small GTPase Ras-related C3 botulinum toxin substrate (Rac)1. In addition to regulating actin cytoskeleton remodeling necessary for tumor cell adhesion, migration and invasion, Rac1 through its downstream effectors, regulates cancer cell survival, tumor angiogenesis, phenotypic plasticity, quiescence, and resistance to therapeutics. In this review we discuss evidence for Rac1 activation within the ovarian tumor microenvironment, mechanisms of Rac1 dysregulation as they apply to ovarian cancer, and the potential benefits of targeting aberrant Rac1 activity in this disease. The potential for Rac1 contribution to extraperitoneal dissemination of ovarian cancer is addressed.

Dux4 controls migration of mesenchymal stem cells through the Cxcr4-Sdf1 axis

We performed transcriptome profiling of human immortalized myoblasts (MB) transiently expressing double homeobox transcription factor 4 (DUX4) and double homeobox transcription factor 4 centromeric (DUX4c) and identified 114 and 70 genes differentially expressed in DUX4- and DUX4c-transfected myoblasts, respectively. A significant number of differentially expressed genes were involved in inflammation, cellular migration and chemotaxis suggesting a role for DUX4 and DUX4c in these processes. DUX4 but not DUX4c overexpression resulted in upregulation of the CXCR4 (C-X-C motif Receptor 4) and CXCL12 (C-X-C motif ligand 12 also known as SDF1) expression in human immortalized myoblasts. In a Transwell cell migration assay, human bone marrow-derived mesenchymal stem cells (BMSCs) were migrating more efficiently towards human immortalized myoblasts overexpressing DUX4 as compared to controls; the migration efficiency of DUX4-transfected BMSCs was also increased. DUX4c overexpression in myoblasts or in BMSCs had no impact on the rate of BMSC migration. Antibodies against SDF1 and CXCR4 blocked the positive effect of DUX4 overexpression on BMSC migration. We propose that DUX4 controls the cellular migration of mesenchymal stem cells through the CXCR4 receptor.

Identification of Novel Hemangioblast Genes in the Early Chick Embryo

During early vertebrate embryogenesis, both hematopoietic and endothelial lineages derive from a common progenitor known as the hemangioblast. Hemangioblasts derive from mesodermal cells that migrate from the posterior primitive streak into the extraembryonic yolk sac. In addition to primitive hematopoietic cells, recent evidence revealed that yolk sac hemangioblasts also give rise to tissue-resident macrophages and to definitive hematopoietic stem/progenitor cells. In our previous work, we used a novel hemangioblast-specific reporter to isolate the population of chick yolk sac hemangioblasts and characterize its gene expression profile using microarrays. Here we report the microarray profile analysis and the identification of upregulated genes not yet described in hemangioblasts. These include the solute carrier transporters SLC15A1 and SCL32A1, the cytoskeletal protein RhoGap6, the serine protease CTSG, the transmembrane receptor MRC1, the transcription factors LHX8, CITED4 and PITX1, and the previously uncharacterized gene DIA1R. Expression analysis by in situ hybridization showed that chick DIA1R is expressed not only in yolk sac hemangioblasts but also in particular intraembryonic populations of hemogenic endothelial cells, suggesting a potential role in the hemangioblast-derived hemogenic lineage. Future research into the function of these newly identified genes may reveal novel important regulators of hemangioblast development.

Hedgehog inhibitors selectively target cell migration and adhesion of mantle cell lymphoma in bone marrow microenvironment

The clinical benefits of a Hedgehog (Hh) inhibitor, LDE225 (NPV-LDE-225, Erismodegib), have been unclear in hematological cancers. Here, we report that LDE225 selectively inhibited migration and adhesion of mantle cell lymphoma (MCL) to bone marrows via very late antigen-4 (VLA-4) mediated inactivation of focal adhesion kinase (FAK) signaling. LDE225 treatment not only affected MCL cells, but also modulated stromal cells within the bone marrow microenvironment by decreasing their production of SDF-1, IL-6 and VCAM-1, the ligand for VLA-4. Surprisingly, LDE225 treatment alone did not suppress cell proliferation due to increased CXCR4 expression mediated by reactive oxygen species (ROS). The increased ROS/CXCR4 further stimulated autophagy formation. The combination of LDE225 with the autophagy inhibitors further enhanced MCL cell death. Our data, for the first time, revealed LDE225 selectively targets MCL cells migration and adhesion to bone marrows. The ineffectiveness of LDE225 in MCL is due to autophagy formation, which in turn increases cell viability. Inhibiting autophagy will be an effective adjuvant therapy for LDE225 in MCL, especially for advanced MCL patients with bone marrow involvement.

Growth Factor Delivery Systems for Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are often a key component in tissue engineering and regenerative medicine approaches. In order to fully exploit the therapeutic potential of GFs, GF delivery vehicles have to meet a number of key design criteria such as providing localized delivery and mimicking the dynamic native GF expression levels and patterns. The use of biomaterials as delivery systems is the most successful strategy for controlled delivery and has been translated into different commercially available systems. However, the risk of side effects remains an issue, which is mainly attributed to insufficient control over the release profile. This book chapter reviews the current strategies, chemistries, materials and delivery vehicles employed to overcome the current limitations associated with GF therapies.

Administration of signalling molecules dictates stem cell homing for in situ regeneration

Ex vivo-expanded stem cells have long been a cornerstone of biotherapeutics and have attracted increasing attention for treating intractable diseases and improving tissue regeneration. However, using exogenous cellular materials to develop restorative treatments for large numbers of patients has become a major concern for both economic and safety reasons. Advances in cell biological research over the past two decades have expanded the potential for using endogenous stem cells during wound healing processes, and in particular, recent insight into stem cell movement and homing has prompted regenerative research and therapy based on recruiting endogenous cells. Inspired by the natural healing process, artificial administration of specific chemokines as signals systemically or at the injury site, typically using biomaterials as vehicles, is a state-of-the-art strategy that potentiates stem cell homing and recreates an anti-inflammatory and immunomodulatory microenvironment to enhance in situ tissue regeneration. However, pharmacologically coaxing endogenous stem cells to act as therapeutics in the field of biomedicine remains in the early stages; its efficacy is limited by the lack of innovative methodologies for chemokine presentation and release. This review describes how to direct the homing of endogenous stem cells via the administration of specific signals, with a particular emphasis on targeted signalling molecules that regulate this homing process, to enhance in situ tissue regeneration. We also provide an outlook on and critical considerations for future investigations to enhance stem cell recruitment and harness the reparative potential of these recruited cells as a clinically relevant cell therapy.

Inhibition of MEK/ERK signalling pathway promotes erythroid differentiation and reduces HSCs engraftment in ex vivo expanded haematopoietic stem cells

The MEK/ERK pathway is found to be important in regulating different biological processes such as proliferation, differentiation and survival in a wide variety of cells. However, its role in self‐renewal of haematopoietic stem cells is controversial and remains to be clarified. The aim of this study was to understand the role of MEK/ERK pathway in ex vivo expansion of mononuclear cells (MNCs) and purified CD34⁺ cells, both derived from human umbilical cord blood (hUCB). Based on our results, culturing the cells in the presence of an inhibitor of MEK/ERK pathway—PD0325901 (PD)—significantly reduces the expansion of CD34⁺ and CD34⁺ CD38⁻ cells, while there is no change in the expression of stemness‐related genes (HOXB4, BMI1). Moreover, in vivo analysis demonstrates that PD reduces engraftment capacity of ex vivo expanded CD34⁺ cells. Notably, when ERK pathway is blocked in UCB‐MNCs, spontaneous erythroid differentiation is promoted, found in concomitant with increasing number of burst‐forming unit‐erythroid colony (BFU‐E) as well as enhancement of erythroid glycophorin‐A marker. These results are in total conformity with up‐regulation of some erythroid enhancer genes (TAL1, GATA2, LMO2) and down‐regulation of some erythroid repressor genes (JUN, PU1) as well. Taken together, our results support the idea that MEK/ERK pathway has a critical role in achieving the correct balance between self‐renewal and differentiation of UCB cells. Also, we suggest that inhibition of ERK signalling could likely be a new key for erythroid induction of UCB‐haematopoietic progenitor cells.

Relationship between rs1801157 polymorphism in stromal cell-derived factor gene and systemic lupus erythematosus risk

Objective

Present meta-analysis was performed to investigate the role of stromal cell-derived factor (SDF-1) gene rs1801157 polymorphism in systemic lupus erythematosus (SLE).

Results

Five publications with 1,087 cases and 1,181 controls were incorporated in this meta-analysis. Overall, a marginal association between SDF-1 rs1801157 polymorphism and reduced SLE risk was found under GA vs. GG model (OR = 0.84, 95% CI = 0.70–1.00). A similar result was also observed in Asian subgroup under the same comparison after stratification analysis by ethnicity (OR = 0.79, 95% CI = 0.63–1.00).

Materials and Methods

All included studies were retrieved from PubMed, EMBASE, Google Scholar Web and Chinese National Knowledge Infrastructure (CNKI). Odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated to appraise the strength of association between SDF-1 rs1801157 polymorphism and SLE risk. The stratification analysis was also performed according to ethnicity. In addition, heterogeneity was examined with Q test, and sensitivity analysis was used to test the stability of final results. Begg’s funnel plot and Egger’s test were adopted to evaluate publication bias.

Conclusions

SDF-1 rs1801157 polymorphism may not influence the risk of SLE. However, more studies with larger sample sizes involving different populations are needed to further explore this issue.

Omega-3 Fatty Acids Supplementation Differentially Modulates the SDF-1/CXCR-4 Cell Homing Axis in Hypertensive and Normotensive Rats

BACKGROUND

We assessed the effect of acute and chronic dietary supplementation of ω-3 on lipid metabolism and cardiac regeneration, through its influence on the Stromal Derived Factor-1 (SDF-1) and its receptor (CXCR4) axis in normotensive and hypertensive rats.

METHODS

Male Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were allocated in eight groups (of eight animals each), which received daily orogastric administration of ω-3 (1 g) for 24 h, 72 h or 2 weeks. Blood samples were collected for the analysis of the lipid profile and SDF-1 systemic levels (ELISA). At the end of the treatment period, cardiac tissue was collected for CXCR4 expression analysis (Western blot).

RESULTS

The use of ω-3 caused a reduction in total cholesterol levels (p = 0.044), and acutely activated the SDF-1/CXCR4 axis in normotensive animals (p = 0.037). In the presence of the ω-3, after 72 h, SDF-1 levels decreased in WKY and increased in SHR (p = 0.017), and tissue expression of the receptor CXCR4 was higher in WKY than in SHR (p = 0.001).

CONCLUSION

The ω-3 fatty acid supplementation differentially modulates cell homing mediators in normotensive and hypertensive animals. While WKY rats respond acutely to omega-3 supplementation, showing increased release of SDF-1 and CXCR4, SHR exhibit a weaker, delayed response.

Bifurcated BACH2 control coordinates mantle cell lymphoma survival and dispersal during hypoxia

BACH2, a B-cell-specific transcription factor, plays a critical role in oxidative stress-mediated drug resistance in mantle cell lymphoma (MCL); however, the biological functions of BACH2 and its regulation of B-cell malignancies in chronic hypoxic microenvironment have not been studied. Here, we found that silencing BACH2 led to not only increased tumor formation and colony formation but also increased tumor dispersal to spleen and bone marrow. Decreased BACH2 levels in patients were also correlated with bone marrow and gastrointestinal dispersal of MCL and blastoid subtypes of MCL. Unexpectedly, decreased BACH2 levels in dispersed MCL cells were due to direct transcriptional repression by hypoxia-induced factor 1α (HIF-1α) and increased heme-mediated protein degradation. In normoxic conditions, BACH2 was able to modulate HIF-1α degradation by suppressing prolyl hydroxylase 3 expression. Bifurcated BACH2 controls during hypoxia and normoxia coordinate not only MCL tumor dispersal but also drug resistance, including bortezomib resistance, via plasmacytic differentiation. Our data highlight an interactive relationship between tumor cells and local microenvironment and the mechanisms of B-cell transcription factor in the regulation of MCL dispersal.

CXCL12 Promotes Stem Cell Recruitment and Uterine Repair after Injury in Asherman's Syndrome

Asherman’s syndrome is an acquired condition of uterine fibrosis and adhesions in response to injury that adversely affects fertility and pregnancy. We have previously demonstrated that bone marrow-derived mesenchymal stem cells (BMDSCs) contribute to uterine repair after injury and that stem cells supplementation improves fertility. Here, we demonstrate that CXCL12 is the chemokine that mediates stem cell engraftment and functional improvement using a murine model of Asherman’s syndrome. After uterine injury, we demonstrate that CXCL12 augmentation increased BMDSC engraftment and that the CXCL12 receptor (CXCR4) antagonist, ADM3100, blocked stem cell recruitment. CXCL12 reduced, whereas ADM3100 increased fibrosis. CXCL12 treatment led to improved fertility and litter size, whereas ADM3100 treatment reduced fertility and litter size. ADM3100 prevented optimal spontaneous uterine repair mediated by endogenous CXCL12 production, reducing pregnancies after injury in the absence of supplemental CXCL12 administration; however, ADM3100 treatment could be partially rescued by CXCL12 augmentation. CXCL12 or other CXCR4 receptor agonists may be useful in the treatment of infertility or adverse pregnancy outcomes in Asherman’s syndrome and other related uterine disorders.

Incorporation of heparin-binding proteins into preformed dextran sulfate-chitosan nanoparticles

Incorporation of proteins into dextran sulfate (DS)-chitosan (CS) nanoparticles (DSCS NPs) is commonly performed using entrapment procedures, in which protein molecules are mixed with DS and CS until particle formation occurs. As DS is an analog of heparin, the authors examined whether proteins could be directly incorporated into preformed DSCS NPs through a heparin binding domain-mediated interaction. The authors formulated negatively-charged DSCS NPs, and quantified the amount of charged DS in the outer shell of the particles. The authors then mixed the DSCS NPs with heparin-binding proteins (SDF-1α, VEGF, FGF-2, BMP-2, or lysozyme) to achieve incorporation. Data show that for DSCS NPs containing 100 nmol charged glucose sulfate units in DS, up to ~1.5 nmol of monomeric or ~0.75 nmol of dimeric heparin-binding proteins were incorporated without significantly altering the size or zeta potential of the particles. Incorporation efficiencies of these proteins were 95%–100%. In contrast, serum albumin or serum globulin showed minimal incorporation (8% and 4%, respectively) in 50% physiological saline, despite their large adsorption in water (80% and 92%, respectively). The NP-incorporated SDF-1α and VEGF exhibited full activity and sustained thermal stability. An in vivo aerosolization study showed that NP-incorporated SDF-1α persisted in rat lungs for 72 h (~34% remaining), while free SDF-1α was no longer detectable after 16 h. As many growth factors and cytokines contain heparin-binding sites/domains, incorporation into preformed DSCS NPs could facilitate in vivo applications of these proteins.

Mesenchymal Stem and Progenitor Cells in Normal and Dysplastic Hematopoiesis-Masters of Survival and Clonality?

Myelodysplastic syndromes (MDS) are malignant hematopoietic stem cell disorders that have the capacity to progress to acute myeloid leukemia (AML). Accumulating evidence suggests that the altered bone marrow (BM) microenvironment in general, and in particular the components of the stem cell niche, including mesenchymal stem cells (MSCs) and their progeny, play a pivotal role in the evolution and propagation of MDS. We here present an overview of the role of MSCs in the pathogenesis of MDS, with emphasis on cellular interactions in the BM microenvironment and related stem cell niche concepts. MSCs have potent immunomodulatory capacities and communicate with diverse immune cells, but also interact with various other cellular components of the microenvironment as well as with normal and leukemic stem and progenitor cells. Moreover, compared to normal MSCs, MSCs in MDS and AML often exhibit altered gene expression profiles, an aberrant phenotype, and abnormal functional properties. These alterations supposedly contribute to the “reprogramming” of the stem cell niche into a disease-permissive microenvironment where an altered immune system, abnormal stem cell niche interactions, and an impaired growth control lead to disease progression. The current article also reviews molecular targets that play a role in such cellular interactions and possibilities to interfere with abnormal stem cell niche interactions by using specific targeted drugs.

Beyond the Niche: Myelodysplastic Syndrome Topobiology in the Laboratory and in the Clinic

We review the murine and human microenvironment and hematopoietic stem cell niche in the context of intact bone marrow architecture in man and mouse, both in normal and in myelodysplastic syndrome marrow. We propose that the complexity of the hematopoietic stem cell niche can usefully be approached in the context of its topobiology, and we provide a model that incorporates in vitro and in vivo models as well as in situ findings from intact human marrow to explain the changes seen in myelodysplastic syndrome patients. We highlight the clinical application of the study of the bone marrow microenvironment and its topobiology in myelodysplastic syndromes.

Increased Proportion of Hematopoietic Stem and Progenitor Cell Population in Cord Blood of Neonates Born to Mothers with Gestational Diabetes Mellitus

We assessed the hematopoietic stem and progenitor cell (HSPC) population in the cord blood of neonates born to mothers with gestational diabetes mellitus (GDM) in a hypothesis generating pilot study, due to that, neonatal polycythemia may be the consequence of GDM pregnancy. Forty-five pregnant women with GDM (last trimester mean HbA1C = 33.9 mmol/mol) and 42 (nondiabetic) control pregnant women were enrolled after their routine 75 g oral glucose tolerance test (OGTT) between the 24th and 28th gestational week (with expected differences in their mean routine clinical characteristics: plasma glucose at OGTT: 0′ = 5.07 vs. 4.62 mM, 120′ = 8.9 vs. 5.76 mM, age = 35.07 vs. 31.66 years, prepregnancy body mass index = 27.9 vs. 23.9 kg/m², GDM vs. control, respectively) on a voluntary basis after signing the informed consent. EDTA-treated cord blood samples were analyzed by flow cytometry and the software Kaluza1.2 using CD45 and CD34-specific fluorescent antibodies to identify the HSPC population (CD34⁺ cells within the CD45^dim blast gate). The proportion of CD34⁺CD45^dim HSPCs among the nucleated cells was significantly (P < 0.05, statistical power = 60.8%) higher in the cord blood samples of neonates born to mothers with GDM (median 0.38%) compared to neonates born to nondiabetic mothers (median 0.32%) and according to treatment types (P < 0.05) median: control 0.32%, GDM-diet only 0.37%, GDM-on insulin 0.45%; control versus GDM on insulin (P < 0.05). The increased proportion of circulating CD34⁺CD45^dim cells in the cord blood may possibly be related to altered fetal stem cell mobilization in GDM pregnancy, yet these results should be interpreted only as preliminary due to the small sample sizes.

Evidence that β7 Integrin Regulates Hematopoietic Stem Cell Homing and Engraftment Through Interaction with MAdCAM-1

α4β7 integrin is a cell adhesion receptor that is crucial for the migration of hematopoietic progenitors and mature effector cells in the periphery, but its role in adult hematopoiesis is controversial. We identified a subset of hematopoietic stem cells (HSCs) in the bone marrow (BM) that expressed β7 integrin. These β7(+) HSCs were capable of multilineage, long-term reconstitution and had an inherent competitive advantage over β7(-) HSCs. On the other hand, HSCs that lacked β7 integrin (β7KO) had reduced engraftment potential. Interestingly, quantitative RT-PCR and flow cytometry revealed that β7KO HSCs expressed lower levels of the chemokine receptor CXCR4. Accordingly, β7KO HSCs exhibited impaired migration abilities in vitro and BM homing capabilities in vivo. Lethal irradiation induced expression of the α4β7 integrin ligand-mucosal addressin cell adhesion molecule-1 (MAdCAM-1) on BM endothelial cells. Moreover, blocking MAdCAM-1 reduced the homing of HSCs and impaired the survival of recipient mice. Altogether, these data indicate that β7 integrin, when expressed by HSCs, interacted with its endothelial ligand MAdCAM-1 in the BM microenvironment, thereby promoting HSC homing and engraftment.

Positron emission tomographic imaging of CXCR4 in cancer: challenges and promises

Molecular imaging is an attractive platform for noninvasive detection and assessment of cancer. In recent years, the targeted imaging of the C-X-C chemokine receptor 4 (CXCR4), a chemokine receptor that has been associated with tumor metastasis, has become an area of intensive research. This review article focuses on positron emission tomography (PET) and aims to provide useful and critical insights into the application of PET to characterize CXCR4 expression, including the chemical, radiosynthetic, and biological requirements for PET radiotracers. This discussion is informed by a summary of the different approaches taken so far and a comparison of their clinical translation. Finally, our expert opinions as to potential future advances in the field are expressed.

ROS-Induced CXCR4 Signaling Regulates Mantle Cell Lymphoma (MCL) Cell Survival and Drug Resistance in the Bone Marrow Microenvironment via Autophagy

PURPOSE

Patients with advanced stages of mantle cell lymphoma (MCL) have a poor prognosis after standard therapies. MCL cells in those patients often spread into tissues other than lymph nodes, such as the bone marrow. Apart from directed migration and homing, there is little understanding of the function of the CXCR4/SDF-1 signaling axis in MCL. In this report, we aim to understand mechanisms of MCL cell survival in the bone marrow.

EXPERIMENTAL DESIGN

For comprehensive analyses of MCL interactions with bone marrow stromal cells, we have generated gene knockout cells using CRISPR-CAS9 system and gene knockdown cells to reveal novel roles of the CXCR4/SDF-1 signaling.

RESULTS

CXCR4 silencing in MCL cells led to a significant reduction in proliferation, cell adhesion to bone marrow stromal cells, and colony formation in PHA-LCM methylcellulose medium, which were reversed upon the addition of SDF-1-neutralizing antibodies. In addition, tracking MCL cell engraftment in vivo revealed that quiescent MCL cells are significantly reduced in the bone marrow upon CXCR4 silencing, indicating that CXCR4/SDF-1 signaling is required for the survival and maintenance of the quiescent MCL cells. Further analysis revealed novel mechanisms of ROS-induced CXCR4/SDF-1 signaling that stimulate autophagy formation in MCL cells for their survival.

CONCLUSIONS

Our data, for the first time, revealed new roles of the CXCR/SDF-1 signaling axis on autophagy formation in MCL, which further promoted their survival within the bone marrow microenvironment. Targeting the CXCR4/SDF-1/autophagy signaling axis may contribute to an enhanced efficacy of current therapies.

CXCL12 Gene Therapy Ameliorates Ischemia-Induced White Matter Injury in Mouse Brain

Remyelination is an important repair process after ischemic stroke-induced white matter injury. It often fails because of the insufficient recruitment of oligodendrocyte progenitor cells (OPCs) to the demyelinated site or the inefficient differentiation of OPCs to oligodendrocytes. We investigated whether CXCL12 gene therapy promoted remyelination after middle cerebral artery occlusion in adult mice. The results showed that CXCL12 gene therapy at 1 week after ischemia could protect myelin sheath integrity in the perifocal region, increase the number of platelet-derived growth factor receptor-α (PDGFRα)-positive and PDGFRα/bromodeoxyuridine-double positive OPCs in the subventricular zone, and further enhance their migration to the ischemic lesion area. Coadministration of AMD3100, the antagonist for CXCL12 receptor CXCR4, eliminated the beneficial effect of CXCL12 on myelin sheath integrity and negatively influenced OPC proliferation and migration. At 5 weeks after ischemia, CXCR4 was found on the PDGFRα- and/or neuron/glia type 2 (NG2)-positive OPCs but not on the myelin basic protein-positive mature myelin sheaths, and CXCR7 was only expressed on the mature myelin sheath in the ischemic mouse brain. Our data indicated that CXCL12 gene therapy effectively protected white matter and promoted its repair after ischemic injury. The treatment at 1 week after ischemia is effective, suggesting that this strategy has a longer therapeutic time window than the treatments currently available.

SIGNIFICANCE

This study has demonstrated for the first time that CXCL12 gene therapy significantly ameliorates brain ischemia-induced white matter injury and promotes oligodendrocyte progenitor cell proliferation in the subventricular zone and migration to the perifocal area in the ischemic mouse brain. Additional data showed that CXCR4 receptor plays an important role during the proliferation and migration of oligodendrocyte progenitor cells, and CXCR7 might play a role during maturation. In contrast to many experimental studies that provide treatment before ischemic insult, CXCL12 gene therapy was performed 1 week after brain ischemia, which significantly prolonged the therapeutic time window of brain ischemia.