Pathways implicated in stem cell migration: the SDF-1/CXCR4 axis

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.

Evaluation in a porcine wound model and long-term clinical assessment of an autologous heterogeneous skin construct used to close full-thickness wounds

Acute and chronic wounds involving deeper layers of the skin are often not adequately healed by dressings alone and require therapies such as skin grafting, skin substitutes, or growth factors. Here we report the development of an autologous heterogeneous skin construct (AHSC) that aids wound closure. AHSC is manufactured from a piece of healthy full-thickness skin. The manufacturing process creates multicellular segments, which contain endogenous skin cell populations present within hair follicles. These segments are physically optimized for engraftment within the wound bed. The ability of AHSC to facilitate closure of full thickness wounds of the skin was evaluated in a swine model and clinically in 4 patients with wounds of different etiologies. Transcriptional analysis demonstrated high concordance of gene expression between AHSC and native tissues for extracellular matrix and stem cell gene expression panels. Swine wounds demonstrated complete wound epithelialization and mature stable skin by 4 months, with hair follicle development in AHSC-treated wounds evident by 15 weeks. Biomechanical, histomorphological, and compositional analysis of the resultant swine and human skin wound biopsies demonstrated the presence of epidermal and dermal architecture with follicular and glandular structures that are similar to native skin. These data suggest that treatment with AHSC can facilitate wound closure.

CXCR4 enhances the inhibitory effects of bone mesenchymal stem cells on lung cell apoptosis in a rat model of smoking-induced COPD

Chronic obstructive pulmonary disease is the 3rd leading cause of death worldwide, and the available treatments are unsatisfactory, resulting in a major economic burden. As cellular therapy is commonly used for lung disease, we investigated a treatment with CXCR4-overexpressing BMSCs in a COPD model. We extracted and purified Bone marrow mesenchymal stem cells (BMSCs) from SD rats. COPD apoptosis model was established by cigarette smoke exposure. BMSCs (1 × 106 cells per injection)were transplanted in vivo twice a month during model establishment, and alveolar rupture in the lung was assessed. Lung cell apoptosis was assessed by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) analysis, and the concentrations of apoptotic proteins in the lungs were detected by Western blotting. We successfully isolated BMSCs and established CXCR4-overexpressing BMSCs. qRT‒PCR and Western blotting detection both reveal that CXCR4 mRNA level and protein both significantly higher expression in CXCR4-BMSCs than the pBABE-BMSCs. Continuous cigarette smoke exposure caused alveolar septal rupture: In the model group, the alveolar mean linear intercept in the first month was significantly lower than that in the third month (p < 0.05). In the third month, the alveolar mean linear intercept values of the control and CXCR4-BMSC groups were lower than those of the model group (control group p < 0.01, CXCR4-BMSC group p < 0.05), and TUNEL staining revealed that the apoptosis rates of the control and CXCR4-BMSC groups were significantly lower than those of the model group (p < 0.01). Furthermore, the levels of the apoptotic proteins cleaved caspase-8, cleaved caspase-3 and cleaved PARP-1 were higher in the model group than in the control group (p < 0.05) and significantly lower in the CXCR4-BMSC group than in the model group (p < 0.05). The transplantation of CXCR4-overexpressing BMSCs during COPD model generation significantly inhibited apoptosis via the extrinsic apoptosis pathway. CXCR4 enhances the inhibitory effects of bone mesenchymal stem cells on lung cell apoptosis in a rat model of smoking-induced COPD.

The Intercellular Communication Between Mesenchymal Stromal Cells and Hematopoietic Stem Cells Critically Depends on NF-κB Signalling in the Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) regulate the fate of the hematopoietic stem cells (HSCs) through both cell-cell interactions and paracrine mechanisms involving multiple signalling pathways. We have previously shown that co-culturing of HSCs with CoCl₂-treated MSCs expands functional HSCs. While performing these experiments, we had observed that the growth of CoCl₂-treated MSCs was significantly stunted. Here, we show that CoCl₂-treated MSCs possess activated NF-κB signalling pathway, and its pharmacological inhibition significantly relieves their growth arrest. Most interestingly, we found that pharmacological inhibition of NF-κB pathway in both control and CoCl₂-treated MSCs completely blocks their intercellular communication with the co-cultured hematopoietic stem and progenitor cells (HSPCs), resulting in an extremely poor output of hematopoietic cells. Mechanistically, we show that this is due to the down-regulation of adhesion molecules and various HSC-supportive factors in the MSCs. This loss of physical interaction with HSPCs could be partially restored by treating the MSCs with calcium ionophore or calmodulin, suggesting that NF-κB regulates intracellular calcium flux in the MSCs. Importantly, the HSPCs co-cultured with NF-κB-inhibited-MSCs were in a quiescent state, which could be rescued by re-culturing them with untreated MSCs. Our data underscore a critical requirement of NF-κB signalling in the MSCs in intercellular communication between HSCs and MSCs for effective hematopoiesis to occur ex vivo. Our data raises a cautionary note against excessive use of anti-inflammatory drugs targeting NF-κB.

Mesenchymal Stem/Stromal Cells Overexpressing CXCR4R334X Revealed Enhanced Migration: A Lesson Learned from the Pathogenesis of WHIM Syndrome

C-X-C chemokine receptor type 4 (CXCR4), initially recognized as a co-receptor for HIV, contributes to several disorders, including the WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome. CXCR4 binds to its ligand SDF-1 to make an axis involved in the homing property of stem cells. This study aimed to employ WHIM syndrome pathogenesis as an inspirational approach to reinforce cell therapies. Wild type and WHIM-type variants of the CXCR4 gene were chemically synthesized and cloned in the pCDH-513B-1 lentiviral vector. Molecular cloning of the synthetic genes was confirmed by DNA sequencing, and expression of both types of CXCR4 at the protein level was confirmed by western blotting in HEK293T cells. Human adipose-derived mesenchymal stem cells (Ad-MSCs) were isolated, characterized, and subjected to lentiviral transduction with Wild type and WHIM-type variants of CXCR4. The presence of copGFP-positive MSCs confirmed the high efficiency of transduction. The migration ability of both groups of transduced cells was then assessed by transwell migration assay in the presence or absence of a CXCR4-blocking agent. Our qRT-PCR results showed overexpression of CXCR4 at mRNA level in both groups of transduced MSCs, and expression of WHIM-type CXCR4 was significantly higher than Wild type CXCR4 (P<0.05). Our results indicated that the migration of genetically modified MSCs expressing WHIM-type CXCR4 had significantly enhanced towards SDF1 in comparison with Wild type CXCR4 (P<0.05), while it was reduced after treatment with CXCR4 antagonist. These data suggest that overexpression of WHIM-type CXCR4 could lead to enhanced and sustained expression of CXCR4 on human MSCs, which would increase their homing capability; hence it might be an appropriate strategy to improve the efficiency of cell-based therapies.

FGF23 ameliorates ischemia-reperfusion induced acute kidney injury via modulation of endothelial progenitor cells: targeting SDF-1/CXCR4 signaling

The levels of fibroblast growth factor 23 (FGF23) rapidly increases after acute kidney injury (AKI). However, the role of FGF23 in AKI is still unclear. Here, we observe that pretreatment with FGF23 protein into ischemia-reperfusion induced AKI mice ameliorates kidney injury by promoting renal tubular regeneration, proliferation, vascular repair, and attenuating tubular damage. In vitro assays demonstrate that SDF-1 induces upregulation of its receptor CXCR4 in endothelial progenitor cells (EPCs) via a non-canonical NF-κB signaling pathway. FGF23 crosstalks with the SDF-1/CXCR4 signaling and abrogates SDF-1-induced EPC senescence and migration, but not angiogenesis, in a Klotho-independent manner. The downregulated pro-angiogenic IL-6, IL-8, and VEGF-A expressions after SDF-1 infusion are rescued after adding FGF23. Diminished therapeutic ability of SDF-1-treated EPCs is counteracted by FGF23 in a SCID mouse in vivo AKI model. Together, these data highlight a revolutionary and important role that FGF23 plays in the nephroprotection of IR-AKI.

Anti-HIV-1 Activity of pepRF1, a Proteolysis-Resistant CXCR4 Antagonist Derived from Dengue Virus Capsid Protein

There is an urgent need for the development of new anti-HIV drugs that can complement existing medicines to be used against resistant strains. Here, we report the anti-HIV-1 peptide pepRF1, a human serum-resistant peptide derived from the Dengue virus capsid protein. In vitro, pepRF1 shows a 50% inhibitory concentration of 1.5 nM with a potential therapeutic window higher than 53 000. This peptide is specific for CXCR4-tropic strains, preventing viral entry into target cells by binding to the viral coreceptor CXCR4, acting as an antagonist of this receptor. pepRF1 is more effective than T20, the only peptide-based HIV-1 entry inhibitor approved, and excels in inhibiting a HIV-1 strain resistant to T20. Potentially, pepRF1 can be used alone or in combination with other anti-HIV drugs. Furthermore, one can also envisage its use as a novel therapeutic strategy for other CXCR4-related diseases.

In vitro study of SDF-1α-loaded injectable and thermally responsive hydrogels for adipose stem cell therapy by SDF-1/CXCR4 axis

Stem cell-based approaches have become a promising therapeutic strategy for treating ischemic diseases. The aim of this study was to develop injectable hydrogel systems for the local release of stromal cell-derived factor-1α (SDF-1α) to recruit adipose stem cells (ASCs) that express CXCR4 to achieve stem cell therapy and therapeutic angiogenesis. Thermoresponsive and injectable chitosan (CS)/β-glycerophosphate disodium salt pentahydrate (βGP) hydrogels with different concentrations of hyaluronic acid (HA) were designed and fabricated to achieve local and sustained release of SDF-1α for ASC recruitment. Herein, the material structures, physical properties, gelation temperature, and gelation time of hydrogels with different compositions were determined. The incorporation of 0.9% HA in CS-based hydrogels not only enhanced the gelation time but also increased the strength of the hydrogels. In addition, the results revealed that the thermoresponsive and injectable CS/βGP/HA hydrogels showed good biocompatibility. In addition, the in vitro release profiles showed that the hydrogels achieved sustained release of SDF-1α over 7 days and enhanced ASC migration. The results revealed that the hydrogels with HA enhanced the sustained release effect compared with the hydrogel without HA, indicating that the HA content regulated the physical and release properties of the injectable hydrogels. Therefore, thermoresponsive and injectable CS/βGP/HA hydrogels may provide an alternative for treating ischemic diseases via SDF-1/CXCR4 axis for ASC recruitment and retention.

Granulocyte-colony stimulating factor improves intervertebral disc degeneration in experimental adult male rats: A microscopic and radiological study

Intervertebral disc degeneration (IVDD) is a major contributor to low back pain (LBP). Granulocyte-colony stimulating factor (GCSF) is known to mobilize hematopoietic stem cells (HSCs) that may be implicated in intervertebral disc (IVD) regeneration. Rats were divided into the following three groups: (i) control group; (ii) IVDD group-the rats underwent Co5/Co6 and Co7/Co8 IVDD operation; and (iii) GCSF-treated group-the rats received daily GCSF subcutaneous injections starting 6 weeks after the IVDD operation and continued for 5 days. All of the rats were euthanized after 8 weeks, and IVDs were assessed by tail X-ray and histopathological, immunohistochemical, and transmission electron microscopy (TEM) analyses. The X-rays showed disc narrowing in the IVDD group that was significantly widened in the GCSF-treated rats. Histologically, the IVDD group showed disarrangement of the annulus fibrosis lamellae, complete degeneration of the nucleus pulposus, and loss of proteoglycan content. These changes were improved after GCSF treatment. Vertebral endplate thickness and cellularity were significantly decreased with IVDD and significantly increased after GCSF treatment. Stromal cell-derived factor-1α (SDF-1α) immune expression was significantly increased in the IVDD group but decreased in the GCSF-treated group. However, the caspase-3 expression percentage showed no significant difference among the studied groups. TEM showed excessive collagen deposits around the notochordal cells in the IVDD group, which were attenuated in the GCSF-treated group. These results indicate that GCSF improves IVDD and promotes its recovery based on radiological, histological and TEM findings.

Diaphanous-related formin mDia2 regulates beta2 integrins to control hematopoietic stem and progenitor cell engraftment

Bone marrow engraftment of the hematopoietic stem and progenitor cells (HSPCs) involves homing to the vasculatures and lodgment to their niches. How HSPCs transmigrate from the vasculature to the niches is unclear. Here, we show that loss of diaphanous-related formin mDia2 leads to impaired engraftment of long-term hematopoietic stem cells and loss of competitive HSPC repopulation. These defects are likely due to the compromised trans-endothelial migration of HSPCs since their homing to the bone marrow vasculatures remained intact. Mechanistically, loss of mDia2 disrupts HSPC polarization and induced cytoplasmic accumulation of MAL, which deregulates the activity of serum response factor (SRF). We further reveal that beta2 integrins are transcriptional targets of SRF. Knockout of beta2 integrins in HSPCs phenocopies mDia2 deficient mice. Overexpression of SRF or beta2 integrins rescues HSPC engraftment defects associated with mDia2 deficiency. Our findings show that mDia2-SRF-beta2 integrin signaling is critical for HSPC lodgment to the niches.

Bone marrow engraftment of haematopoietic stem and progenitor cells (HSPCs) requires homing and lodgement to the niche. Here, the authors show that mDia2 is required for HSPC polarization, nuclear MAL, and SRF-induced beta2 integrin expression during transendothelial migration of HSPCs required for engraftment.

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.

The Chemokine Receptor CXCR4 Mediates Recruitment of CD11c+ Conventional Dendritic Cells Into the Inflamed Murine Cornea

Purpose

The cornea contains distinct populations of antigen-presenting cells (APCs), including conventional dendritic cells (cDCs). Little is known about the molecular mechanisms involved in cDCs homing and recruitment into the naïve and inflamed cornea. The purpose of this study was to investigate the presence of CXCR4 and its ligand CXCL12 in the murine cornea and its role in cDC migration during corneal inflammation.

Methods

The expression of CXCR4 and CXCL12 in naïve and suture-inflamed murine corneas was assessed by whole-mount staining, flow cytometry, and quantitative PCR. The role of CXCR4 in recruitment into inflamed corneas was investigated using adoptive transfer of cDCs blocked with neutralizing antibody against CXCR4.

Results

We show the chemokine receptor CXCR4 to be expressed on 51.7% and 64.8% of total corneal CD11c⁺ cDCs, equating to 98.6 ± 12.5 cells/mm² in the peripheral and 64.7 ± 10.6 cells/mm² in the central naïve cornea, respectively. Along with a 4.5-fold increase in CXCL12 expression during inflammation (P < 0.05), infiltrating cDCs also expressed CXCR4 in both the peripheral (222.6 ± 33.3 cells/mm²; P < 0.001) and central cornea (161.9 ± 23.8 cells/mm²; P = 0.001), representing a decrease to 31.0% and 37.3% in the cornea, respectively. Further, ex vivo blockade (390.1 ± 40.1 vs. 612.1 ± 78.3; P = 0.008) and local blockade (263.5 ± 27.1 vs. 807.5 ± 179.5, P < 0.001) with anti-CXCR4 neutralizing antibody resulted in a decrease in cDCs homing into the cornea compared with cells pretreated with isotype controls.

Conclusions

Our results demonstrate that corneal CXCL12 plays a direct role in CXCR4⁺ cDC recruitment into the cornea. The CXCR4/CXCL12 axis is therefore a potential target to modulate corneal inflammatory responses.

Sustained Release SDF-1α/TGF-β1-Loaded Silk Fibroin-Porous Gelatin Scaffold Promotes Cartilage Repair

Continuous delivery of growth factors to the injury site is crucial to creating a favorable microenvironment for cartilage injury repair. In the present study, we fabricated a novel sustained-release scaffold, stromal-derived factor-1α (SDF-1α)/transforming growth factor-β1 (TGF-β1)-loaded silk fibroin-porous gelatin scaffold (GSTS). GSTS persistently releases SDF-1α and TGF-β1, which enhance cartilage repair by facilitating cell homing and chondrogenic differentiation. Scanning electron microscopy showed that GSTS is a porous microstructure and the protein release assay demonstrated the sustainable release of SDF-1α and TGF-β1 from GSTS. Bone marrow-derived mesenchymal stem cells (MSCs) maintain high in vitro cell activity and excellent cell distribution and phenotype after seeding into GSTS. Furthermore, MSCs acquired enhanced chondrogenic differentiation capability in the TGF-β1-loaded scaffolds (GSTS or GST: loading TGF-β1 only) and the conditioned medium from SDF-1α-loaded scaffolds (GSTS or GSS: loading SDF-1α only) effectively promoted MSCs migration. GSTS was transplanted into the osteochondral defects in the knee joint of rats, and it could promote cartilage regeneration and repair the cartilage defects at 12 weeks after transplantation. Our study shows that GSTS can facilitate in vitro MSCs homing, migration, chondrogenic differentiation and SDF-1α and TGF-β1 have a synergistic effect on the promotion of in vivo cartilage forming. This SDF-1α and TGF-β1 releasing GSTS have promising therapeutic potential in cartilage repair.

Molecular Mechanisms Mediating Diabetic Retinal Neurodegeneration: Potential Research Avenues and Therapeutic Targets

Diabetic retinopathy (DR) is a devastating complication of diabetes with a prevalence rate of 35%, and no effective treatment options. Since the most visible clinical features of DR are microvascular irregularities, therapeutic interventions often attempt to reduce microvascular injury, but only after permanent retinal damage has ensued. However, recent data suggests that diabetes initially affects retinal neurons, leading to neurodegeneration as an early occurrence in DR, before onset of the more noticeable vascular abnormalities. In this review, we delineate the sequence of initiating events leading to retinal degeneration in DR, considering neuronal dysfunction as a primary event. Key molecular mechanisms and potential biomarkers associated with retinal neuronal degeneration in diabetes are discussed. In addition to glial reactivity and inflammation in the diabetic retina, the contribution of neurotrophic factors, cell adhesion molecules, apoptosis markers, and G protein signaling to neurodegenerative pathways warrants further investigation. These studies could complement recent developments in innovative treatment strategies for diabetic retinopathy, such as targeting retinal neuroprotection, promoting neuronal regeneration, and attempts to re-program other retinal cell types into functional neurons. Indeed, several ongoing clinical trials are currently attempting treatment of retinal neurodegeneration by means of such novel therapeutic avenues. The aim of this article is to highlight the crucial role of neurodegeneration in early retinopathy progression, and to review the molecular basis of neuronal dysfunction as a first step toward developing early therapeutic interventions that can prevent permanent retinal damage in diabetes. ClinicalTrials.gov: NCT02471651, NCT01492400.

CXCL12 rs18011157 polymorphısm in patients wıth non-Hodgkin's lymphoma: Is it associated with poor outcome?

Objective

We studied CXCL12-related rs18011157 polymorphism in non-Hodgkin lymphoma (NHL) patients. We also determined the effect of this polymorphism on clinical features and outcome of NHL.

Methods

We included 90 NHL patients (54 males, 36 females) and 88 healthy controls (54 males, 34 females). CXCL12-related rs18011157 polymorphism was determined by polymerase chain reaction.

Results

rs18011157 polymorphism was significantly more frequent in NHL patients with GA genotype than in healthy controls (37.8% vs. 20.5%, P = 0.011). The frequency of patients with initially high lactate dehydrogenase (LDH) level (65.8% vs. 38.5%) and extranodal involvement (61.1% vs. 43.8%) was significantly higher in the GA plus AA genotype groups when considered altogether (P = 0.01 and 0.09). Poor prognostic factors in univariate analysis were the presence of B symptoms, initially high International Prognostic Index (IPI), splenomegaly, nonresponse to first-line therapy, the presence of early relapse, and carrying A allele (GA plus AA genotypes). The independent prognostic factors in multivariate analysis were only early relapse and an initially high IPI score.

Discussion

CXCL12 rs1801157 polymorphism which was found to be associated with extranodal involvement and increased LDH in NHL might be a marker of poor prognosis in patients with GA and AA genotypes.

Conclusions

CXCL12-related rs18011517 polymorphism was more frequent in NHL patients: it might be associated with NHL pathogenesis and outcome.

Augmented migration of mesenchymal stem cells correlates with the subsidiary CXCR4 variant

Use of mesenchymal stem cells (MSCs) has been introduced as a promising tool, for structural and functional recovery of damaged tissues/organs. Studies have indicated that interactions between chemokine receptors and their ligands have a critical role in homing of MSCs to the site of injury. Although CXCR4 variants have been characterized, the exact role of each transcript in homing has remained unclear. In this study, cells were pretreated with various hypoxia-mimicking compounds (valproic acid, cobalt-chloride, and deferoxamine mesylate). Results indicated that both variants of CXCR4 were overexpressed after 24 hours of treatments and their expression could cooperatively induce and promote the cell migration. Moreover, deferoxamine mesylate was more effective in overexpression of variant A (lo), which resulted in higher level of CXCR4 protein and the highest rate of migration of the cells. In conclusion, our findings may have important potential implications in clinical applications, reinforcing the concept that manipulating the expression of specific CXCR4 variants may increase migration of MSCs.

Phenotypic correction of Fanconi anemia cells in the murine bone marrow after carrier cell mediated delivery of lentiviral vector

Fanconi anemia (FA) is an autosomal-recessive disorder associated with hematopoietic failure and it is a candidate for hematopoietic stem cell (HSC)-directed gene therapy. However, the characteristically reduced HSC numbers found in FA patients, their ineffective mobilization from the marrow, and re-oxygenation damage during ex vivo manipulation have precluded clinical success using conventional in vitro approaches. We previously demonstrated that lentiviral vector (LV) particles reversibly attach to the cell surface where they gain protection from serum complement neutralization. We reasoned that cellular delivery of LV to the bone marrow niche could avoid detrimental losses during FA HSC mobilization and in vitro modification. Here, we demonstrate that a VSV-G pseudotyped lentivector, carrying the FANCC transgene, can be transmitted from carrier to bystander cells. In cell culture and transplantation models of FA, we further demonstrate that LV carrier cells migrate along SDF-1α gradients and transfer vector particles that stably integrate and phenotypically correct the characteristic DNA alkylator sensitivity in murine and human FA-deficient target bystander cells. Altogether, we demonstrate that cellular homing mechanisms can be harnessed for the functional phenotype correction in murine FA hematopoietic cells.

Regulation of Hematopoiesis and Osteogenesis by Blood Vessel-Derived Signals

In addition to their conventional role as a versatile transport system, blood vessels provide signals controlling organ development, regeneration, and stem cell behavior. In the skeletal system, certain capillaries support perivascular osteoprogenitor cells and thereby control bone formation. Blood vessels are also a critical component of niche microenvironments for hematopoietic stem cells. Here we discuss key pathways and factors controlling endothelial cell behavior in bone, the role of vessels in osteogenesis, and the nature of vascular stem cell niches in bone marrow.

Hematopoietic stem cells and solid organ transplantation

Solid organ transplantation provides lifesaving therapy for patients with end stage organ disease. In order for the transplanted organ to survive, the recipient must take a lifelong cocktail of immunosuppressive medications that increase the risk for infections, malignancies and drug toxicities. Data from many animal studies have shown that recipients can be made tolerant of their transplanted organ by infusing stem cells, particularly hematopoietic stem cells, prior to the transplant. The animal data have been translated into humans and now several clinical trials have demonstrated that infusion of hematopoietic stem cells, along with specialized conditioning regimens, can permit solid organ allograft survival without immunosuppressive medications. This important therapeutic advance has been made possible by understanding the immunologic mechanisms by which stem cells modify the host immune system, although it must be cautioned that the conditioning regimens are often severe and associated with significant morbidity. This review discusses the role of hematopoietic stem cells in solid organ transplantation, provides an understanding of how these stem cells modify the host immune system and describes how newer information about adaptive and innate immunity might lead to improvements in the use of hematopoietic stem cells to induce tolerance to transplanted organs.

Chimeric Allografts Induced by Short-Term Treatment With Stem Cell-Mobilizing Agents Result in Long-Term Kidney Transplant Survival Without Immunosuppression: A Study in Rats

Transplant tolerance allowing the elimination of lifelong immunosuppression has been the goal of research for 60 years. The induction of mixed chimerism has shown promise and has been extended successfully to large animals and to the clinic; however, it remains cumbersome and requires heavy early immunosuppression. In this study, we reported that four injections of AMD3100, a CXCR4 antagonist, plus eight injections of low-dose FK506 (0.05 mg/kg per day) in the first week after kidney transplantation extended survival, but death from renal failure occurred at 30-90 days. Repeating the same course of AMD3100 and FK506 at 1, 2 and 3 mo after transplant resulted in 92% allograft acceptance (n = 12) at 7 mo, normal kidney function and histology with no further treatment. Transplant acceptance was associated with the influx of host stem cells, resulting in a hybrid kidney and a modulated host immune response. Confirmation of these results could initiate a paradigm shift in posttransplant therapy.

Chimeric Allografts Induced by Short-Term Treatment With Stem Cell Mobilizing Agents Result in Long-Term Kidney Transplant Survival Without Immunosuppression: II, Study in Miniature Swine

Transplantation is now lifesaving therapy for patients with end-stage organ failure but requires lifelong immunosuppression with resultant morbidity. Current immunosuppressive strategies inhibit T cell activation and prevent donor-recipient engagement. Therefore, it is not surprising that few host cells are demonstrated in donor grafts. However, our recent small animal studies found large numbers of recipient stem cells present after transplantation and pharmacological mobilization, resulting in a chimeric, repopulated organ. We now confirm these findings in a well-characterized large animal preclinical model. Here, we show that AMD3100 and FK506 mobilization of endogenous stem cells immediately post kidney transplantation combined with repeat therapy at 1, 2, and 3 months led to drug-free long-term survival in maximally immunologically mismatched swine. Three long-term recipients have stable chimeric transplants, preserved antidonor skin graft responses, and normal serum creatinine levels despite withdrawal of all medication for 3 years.

Stem cell mobilisation by granulocyte-colony stimulating factor in patients with acute myocardial infarction. Long-term results of the REVIVAL-2 trial

Treatment with granulocyte-colony stimulating factor (G-CSF) mobilises cells from the bone marrow to the peripheral blood. Previous preclinical and early clinical trials may suggest that treatment with G-CSF leads to improved myocardial perfusion and function in acute or chronic ischaemic heart disease. In the REVIVAL-2 study we found that stem cell mobilisation by G-CSF does not influence infarct size, left ventricular function and coronary restenosis in patients with acute myocardial infarction (MI) that underwent successful percutaneous coronary intervention. The objective of the present analysis was to assess the impact of G-CSF treatment on seven-year clinical outcomes from the REVIVAL-2 trial. In the randomized, double-blind, placebo-controlled REVIVAL-2 study, 114 patients with the diagnosis of acute myocardial infarction were enrolled five days after successful reperfusion by percutaneous coronary intervention. Patients were assigned to receive 10 µg/kg G-CSF (n=56) or placebo (n=58) for five days. The primary endpoint for this long-term outcome analysis was the composite of death, myocardial infarction or stroke seven years after randomisation. The endpoint occurred in 14.3 % of patients in the G-CSF group versus 17.2 % assigned to placebo (p=0.67). The combined incidence of death or myocardial infarction occurred in 14.3 % of the patients assigned to G-CSF and 15.5 % of the patients assigned to placebo (p=0.85). In conclusion, these long-term follow-up data show that G-CSF does not improve clinical outcomes of patients with acute myocardial infarction.

Imbalances in Mobilization and Activation of Pro-Inflammatory and Vascular Reparative Bone Marrow-Derived Cells in Diabetic Retinopathy

Diabetic retinopathy is a sight-threatening complication of diabetes, affecting 65% of patients after 10 years of the disease. Diabetic metabolic insult leads to chronic low-grade inflammation, retinal endothelial cell loss and inadequate vascular repair. This is partly due to bone marrow (BM) pathology leading to increased activity of BM-derived pro-inflammatory monocytes and impaired function of BM-derived reparative circulating angiogenic cells (CACs). We propose that diabetes has a significant long-term effect on the nature and proportion of BM-derived cells that circulate in the blood, localize to the retina and home back to their BM niche. Using a streptozotocin mouse model of diabetic retinopathy with GFP BM-transplantation, we have demonstrated that BM-derived circulating pro-inflammatory monocytes are increased in diabetes while reparative CACs are trapped in the BM and spleen, with impaired release into circulation. Diabetes also alters activation of splenocytes and BM-derived dendritic cells in response to LPS stimulation. A majority of the BM-derived GFP cells that migrate to the retina express microglial markers, while others express endothelial, pericyte and Müller cell markers. Diabetes significantly increases infiltration of BM-derived microglia in an activated state, while reducing infiltration of BM-derived endothelial progenitor cells in the retina. Further, control CACs injected into the vitreous are very efficient at migrating back to their BM niche, whereas diabetic CACs have lost this ability, indicating that the in vivo homing efficiency of diabetic CACs is dramatically decreased. Moreover, diabetes causes a significant reduction in expression of specific integrins regulating CAC migration. Collectively, these findings indicate that BM pathology in diabetes could play a role in both increased pro-inflammatory state and inadequate vascular repair contributing to diabetic retinopathy.

Are there any new insights for G-CSF and/or AMD3100 in chemotherapy of haematological malignants?

AML is a common life-threatening blood system malignancy. The treatment of AML continues to face greater challenges. An abnormal haematopoietic niche with high adhesion and proliferation might be the root cause of resistance and relapse. Most leukaemia cells are stored in the endosteal niche and recess in the G0 phase, and they are not sensitive to varieties of radiotherapies and chemotherapies. G-CSF and AMD3100 are increasingly used in priming chemotherapy. G-CSF can promote leukaemia cells to the cell cycle, which improves the complete remission rate of leukaemia patients. AMD3100, the novel CXCR4 antagonist, could also potentially promote leukaemia cells to cell cycle and improve the susceptibility of leukaemia cells to chemotherapeutic agents. The combination of them enhances anti-leukaemia effect. So in this review, we explore the function of G-CSF and/or AMD3100 in the priming chemotherapy of haematological malignants.

Rapid assay of stem cell functionality and potency using electric cell-substrate impedance sensing

Regenerative medicine studies using autologous bone marrow mononuclear cells (BM-MNCs) have shown improved clinical outcomes that correlate to in vitro BM-MNC invasive capacity. The current Boyden-chamber assay for testing invasive capacity is labor-intensive, provides only a single time point, and takes 36 hours to collect data and results, which is not practical from a clinical cell delivery perspective. To develop a rapid, sensitive and reproducible invasion assay, we employed Electric Cell-substrate Impedance Sensing (ECIS) technology. Chemokine-directed BM-MNC cell invasion across a Matrigel-coated Transwell filter was measurable within minutes using the ECIS system we developed. This ECIS-Transwell chamber system provides a rapid and sensitive test of stem and progenitor cell invasive capacity for evaluation of stem cell functionality to provide timely clinical data for selection of patients likely to realize clinical benefit in regenerative medicine treatments. This device could also supply robust unambiguous, reproducible and cost effective data as a potency assay for cell product release and regulatory strategies.

Preclinical Assessment of Mutant Human TRIM5α as an Anti-HIV-1 Transgene

Current HIV-1 gene therapy approaches aim at stopping the viral life cycle at its earliest steps, such as entry or immediate postentry events. Among the most widely adopted strategies are CCR5 downregulation/knockout and the use of broadly neutralizing antibodies. However, the long-term efficacy and side effects are still unclear. TRIM5α is an interferon-stimulated restriction factor that can intercept incoming retroviruses within one hour of cytosolic entry and potently inhibit the infectivity of restriction-sensitive viruses. The human TRIM5α (TRIM5αhu) generally does not efficiently target HIV-1, but point mutations in its capsid-binding domain can confer anti-HIV-1 activity. Although the mechanisms by which TRIM5αhu mutants inhibit HIV-1 are relatively well understood, their characterization as potential transgenes for gene therapy is lacking. Additionally, previous reports of general immune activation by overexpression of TRIM5α have hindered its broad adoption as a potential transgene. Here we demonstrate the ability of the R332G-R335G TRIM5αhu mutant to efficiently restrict highly divergent HIV-1 strains, including Group O, as well as clinical isolates bearing cytotoxic T lymphocyte escape mutations. R332G-R335G TRIM5αhu efficiently protected human lymphocytes against HIV-1 infection, even when expressed at relatively low levels following lentiviral transduction. Most importantly, under these conditions Rhesus macaque TRIM5α (TRIM5αRh) and TRIM5αhu (wild-type or mutated) had no major effects on the NF-κB pathway. Transgenic TRIM5α did not modulate the kinetics of IκBα, JunB, and TNFAIP3 expression following TNF-α treatment. Finally, we show that human lymphocytes expressing R332G-R335G TRIM5αhu have clear survival advantages over unmodified parental cells in the presence of pathogenic, replication-competent HIV-1. These results support the relevance of R332G-R335G and other mutants of TRIM5αhu as candidate effectors for HIV-1 gene therapy.

The intricate role of CXCR4 in cancer

Chemokines mediate numerous physiological and pathological processes related primarily to cell homing and migration. The chemokine CXCL12, also known as stromal cell-derived factor-1, binds the G-protein-coupled receptor CXCR4, which, through multiple divergent pathways, leads to chemotaxis, enhanced intracellular calcium, cell adhesion, survival, proliferation, and gene transcription. CXCR4, initially discovered for its involvement in HIV entry and leukocytes trafficking, is overexpressed in more than 23 human cancers. Cancer cell CXCR4 overexpression contributes to tumor growth, invasion, angiogenesis, metastasis, relapse, and therapeutic resistance. CXCR4 antagonism has been shown to disrupt tumor-stromal interactions, sensitize cancer cells to cytotoxic drugs, and reduce tumor growth and metastatic burden. As such, CXCR4 is a target not only for therapeutic intervention but also for noninvasive monitoring of disease progression and therapeutic guidance. This review provides a comprehensive overview of the biological involvement of CXCR4 in human cancers, the current status of CXCR4-based therapeutic approaches, as well as recent advances in noninvasive imaging of CXCR4 expression.

Circumventing Y. pestis Virulence by Early Recruitment of Neutrophils to the Lungs during Pneumonic Plague

Pneumonic plague is a fatal disease caused by Yersinia pestis that is associated with a delayed immune response in the lungs. Because neutrophils are the first immune cells recruited to sites of infection, we investigated the mechanisms responsible for their delayed homing to the lung. During the first 24 hr after pulmonary infection with a fully virulent Y. pestis strain, no significant changes were observed in the lungs in the levels of neutrophils infiltrate, expression of adhesion molecules, or the expression of the major neutrophil chemoattractants keratinocyte cell-derived chemokine (KC), macrophage inflammatory protein 2 (MIP-2) and granulocyte colony stimulating factor (G-CSF). In contrast, early induction of chemokines, rapid neutrophil infiltration and a reduced bacterial burden were observed in the lungs of mice infected with an avirulent Y. pestis strain. In vitro infection of lung-derived cell-lines with a YopJ mutant revealed the involvement of YopJ in the inhibition of chemoattractants expression. However, the recruitment of neutrophils to the lungs of mice infected with the mutant was still delayed and associated with rapid bacterial propagation and mortality. Interestingly, whereas KC, MIP-2 and G-CSF mRNA levels in the lungs were up-regulated early after infection with the mutant, their protein levels remained constant, suggesting that Y. pestis may employ additional mechanisms to suppress early chemoattractants induction in the lung. It therefore seems that prevention of the early influx of neutrophils to the lungs is of major importance for Y. pestis virulence. Indeed, pulmonary instillation of KC and MIP-2 to G-CSF-treated mice infected with Y. pestis led to rapid homing of neutrophils to the lung followed by a reduction in bacterial counts at 24 hr post-infection and improved survival rates. These observations shed new light on the virulence mechanisms of Y. pestis during pneumonic plague, and have implications for the development of novel therapies against this pathogen.

Cancer stem cells and tumor metastasis

Cancer stem cells (CSCs) are endowed with an inherent resistance to cytotoxic drugs, and are closely related to the migration, invasiveness, and anti-apoptotic ability of the cancer cells. Epithelial-mesenchymal transition (EMT) is a process where epithelial cells acquire the highly invasive and metastatic characteristics of mesenchymal cells, and has a close connection with CSCs. In this paper, the authors address the recent progress made in the relationship between the EMT status of CSCs and tumor metastasis and between the localization and chemotaxis of CSCs and the formation of the metastatic colonies, as well as the relation of CSCs with the therapeutic strategy for cancer treatment.

Application of human bone marrow-derived mesenchymal stem cells in the treatment of radiation-induced Gastrointestinal syndrome

Nuclear accidents and terrorism present a serious threat for mass casualty. Accidental or intended radiation exposure leads to radiation-induced gastrointestinal (GI) syndrome. However, currently there are no approved medical countermeasures for GI syndrome. Thus, developing novel treatments for GI syndrome is urgent. Mesenchymal stem cells (MSCs) derived from bone marrow are a subset of multipotent adult somatic stem cells that have the ability to undergo self-renewal, proliferation and pluripotent differentiation. MSCs have advantages over other stem cells; they can be easily isolated from patients or donors, readily expanded ex vivo, and they possess reparative and immunomodulatory properties. Moreover, MSCs have been shown to be powerful tools in gene therapy and can be effectively transduced with vectors containing therapeutic genes. Therefore, the therapeutic potential of MSCs has been brought into the spotlight for the clinical treatment of GI syndrome. In this review, we discuss the possible role of MSCs in radiation-induced GI syndrome.

The effect of CXCL12 on endothelial progenitor cells: potential target for angiogenesis in intracerebral hemorrhage

Endothelial progenitor cells (EPCs) may contribute to vascular repair and angiogenesis. Chemokine (C-X-C motif) ligand 12 (CXCL12/SDF-1) is known to play an important role in the mobilization and recruitment of progenitor cells. Therefore, we assessed the function of CXCL12 as a stimulating molecule of angiogenesis in EPCs and the underlying mechanism after intracerebral hemorrhage (ICH). Isolated EPCs from male Sprague-Dawley rats, stimulate with various doses of CXCL12. Then, 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess the proliferation of EPCs, and cell migration and adhesion were analyzed by transwell chamber assay. Furthermore, mRNA levels of endothelial markers von Willebrand Factor (vWF), Tie-2, and vascular endothelial cadherin (VE-cadherin) were explored by real-time polymerase chain reaction. Capillary tube and vessel formation in vitro and in vivo were detected after pretreatment with the C-X-C chemokine receptor type 4 (CXCR4) inhibitor AMD3100. Following stimulation with various doses of CXCL12, an obvious dose-dependent increase in the proliferation, migration, and adhesion of EPCs was confirmed. Furthermore, the mRNA levels of endothelial markers vWF, Tie-2, and VE-cadherin were also demonstrated in CXCL12-treated EPCs, indicating that CXCL12 could regulate EPC differentiation to endothelial cells. Importantly, these increases depended on the activation of CXCR4 signaling, as pretreatment with CXCR4 inhibitor AMD3100 dramatically dampened the CXCL12-induced effects. Additionally, blocking CXCR4 signaling dampened CXCL12-induced angiogenic activity both in vitro and in vivo. Following construction of a rodent ICH model, scaffolds delivering CXCL12 together with EPCs resulted in an evident increase in blood vessel formation; however, this increase in blood vessels was attenuated with delivery of AMD3100. CXCL12 stimulates EPCs to induce angiogenesis though the CXCR4 pathway after ICH. Consequently, our findings provide a potential target for angiogenesis in ICH.

Combination of imatinib with CXCR4 antagonist BKT140 overcomes the protective effect of stroma and targets CML in vitro and in vivo

Functional role of CXCR4 in chronic myelogenous leukemia (CML) progression was evaluated. Elevated CXCR4 significantly increased the in vitro survival and proliferation in response to CXCL12. CXCR4 stimulation resulted in activation of extracellular signal-regulated kinase (Erk)-1/2, Akt, S6K, STAT3, and STAT5 prosurvival signaling pathways. In accordance, we found that in vitro treatment with CXCR4 antagonist BKT140 directly inhibited the cell growth and induced cell death of CML cells. Combination of BKT140 with suboptimal concentrations of imatinib significantly increased the anti-CML effect. BKT140 induced apoptotic cell death, decreasing the levels of HSP70 and HSP90 chaperones and antiapoptotic proteins BCL-2 and BCL-XL, subsequently promoting the release of mitochondrial factors cytochrome c and SMAC/Diablo. Bone marrow (BM) stromal cells (BMSC) markedly increased the proliferation of CML cells and protected them from imatinib-induced apoptosis. Furthermore, BMSCs elevated proto-oncogene BCL6 expression in the CML cells in response to imatinib treatment, suggesting the possible role of BCL6 in stroma-mediated TKI resistance. BKT140 reversed the protective effect of the stroma, effectively promoted apoptosis, and decreased BCL6 levels in CML cells cocultured with BMSCs. BKT140 administration in vivo effectively reduced the growth of subcutaneous K562-produced xenografts. Moreover, the combination of BKT140 with low-dose imatinib markedly inhibited tumor growth, achieving 95% suppression. Taken together, our data indicate the importance of CXCR4/CXCL12 axis in CML growth and CML-BM stroma interaction. CXCR4 inhibition with BKT140 antagonist efficiently cooperated with imatinib in vitro and in vivo. These results provide the rational basis for CXCR4-targeted therapy in combination with TKI to override drug resistance and suppress residual disease.

BIGH3 modulates adhesion and migration of hematopoietic stem and progenitor cells

Cell adhesion and migration are important determinants of homing and development of hematopoietic stem and progenitor cells (HSPCs) in bone marrow (BM) niches. The extracellular matrix protein transforming growth factor-β (TGF-β) inducible gene H3 (BIGH3) is involved in adhesion and migration, although the effect of BIGH3 is highly cell type-dependent. BIGH3 is abundantly expressed by mesenchymal stromal cells, while its expression in HSPCs is relatively low unless induced by certain BM stressors. Here, we set out to determine how BIGH3 modulates HSPC adhesion and migration. We show that primary HSPCs adhere to BIGH3-coated substrates, which is, in part, integrin-dependent. Overexpression of BIGH3 in HSPCs and HL60 cells reduced the adhesion to the substrate fibronectin in adhesion assays, which was even more profound in electrical cell-substrate impedance sensing (ECIS) assays. Accordingly, the CXCL12 induced migration over fibronectin-coated surface was reduced in BIGH3-expressing HSPCs. The integrin expression profile of HSPCs was not altered upon BIGH3 expression. Although expression of BIGH3 did not alter actin polymerization in response to CXCL12, it inhibited the PMA-induced activation of the small GTPase RAC1 as well as the phosphorylation and activation of extracellular-regulated kinases (ERKs). Reduced activation of ERK and RAC1 may be responsible for the inhibition of cell adhesion and migration by BIGH3 in HSPCs. Induced BIGH3 expression upon BM stress may contribute to the regulation of BM homeostasis.

Emerging targets in cancer management: role of the CXCL12/CXCR4 axis

The chemokine CXCL12 (SDF-1) and its cell surface receptor CXCR4 were first identified as regulators of lymphocyte trafficking to the bone marrow. Soon after, the CXCL12/CXCR4 axis was proposed to regulate the trafficking of breast cancer cells to sites of metastasis. More recently, it was established that CXCR4 plays a central role in cancer cell proliferation, invasion, and dissemination in the majority of malignant diseases. The stem cell concept of cancer has revolutionized the understanding of tumorigenesis and cancer treatment. A growing body of evidence indicates that a subset of cancer cells, referred to as cancer stem cells (CSCs), plays a critical role in tumor initiation, metastatic colonization, and resistance to therapy. Although the signals generated by the metastatic niche that regulate CSCs are not yet fully understood, accumulating evidence suggests a key role of the CXCL12/CXCR4 axis. In this review we focus on physiological functions of the CXCL12/CXCR4 signaling pathway and its role in cancer and CSCs, and we discuss the potential for targeting this pathway in cancer management.

Regulatory systems in bone marrow for hematopoietic stem/progenitor cells mobilization and homing

Regulation of hematopoietic stem cell release, migration, and homing from the bone marrow (BM) and of the mobilization pathway involves a complex interaction among adhesion molecules, cytokines, proteolytic enzymes, stromal cells, and hematopoietic cells. The identification of new mechanisms that regulate the trafficking of hematopoietic stem/progenitor cells (HSPCs) cells has important implications, not only for hematopoietic transplantation but also for cell therapies in regenerative medicine for patients with acute myocardial infarction, spinal cord injury, and stroke, among others. This paper reviews the regulation mechanisms underlying the homing and mobilization of BM hematopoietic stem/progenitor cells, investigating the following issues: (a) the role of different factors, such as stromal cell derived factor-1 (SDF-1), granulocyte colony-stimulating factor (G-CSF), and vascular cell adhesion molecule-1 (VCAM-1), among other ligands; (b) the stem cell count in peripheral blood and BM and influential factors; (c) the therapeutic utilization of this phenomenon in lesions in different tissues, examining the agents involved in HSPCs mobilization, such as the different forms of G-CSF, plerixafor, and natalizumab; and (d) the effects of this mobilization on BM-derived stem/progenitor cells in clinical trials of patients with different diseases.

Innate immunity derived factors as external modulators of the CXCL12-CXCR4 axis and their role in stem cell homing and mobilization

The α-chemokine CXCL12 (stromal derived factor-1; SDF-1) and its corresponding G_αI protein-coupled CXCR4 receptor axis play an important role in retention of hematopoietic stem progenitor cells (HSPCs) in bone marrow (BM) stem cell niches. CXCL12 has also been identified as a strong chemoattractant for HSPCs and implicated both in homing of HSPCs to BM after transplantation and in egress of these cells from BM into peripheral blood (PB). However, since CXCL12, as a peptide, is highly susceptible to degradation by proteolytic enzymes, its real biological availability in biological fluids may be somewhat limited. In this review, we will present data demonstrating that the CXCL12-CXCR4 axis is positively modulated by innate immunity-derived several external factors, ensuring that even low (near threshold) doses of CXCL12 still exert a robust chemotactic influence on HSPCs.

Galectin-3 enhances angiogenic and migratory potential of microglial cells via modulation of integrin linked kinase signaling

Focal cerebral ischemia initiates self-repair mechanisms that include the production of neurotrophic factors and cytokines. Galectin-3 is an important angiogenic cytokine. We have previously demonstrated that expression of galectin 3 (Gal-3), a carbohydrate binding protein is significantly upregulated in activated microglia in the brains of rats subjected to focal ischemia. Further blocking of Gal-3 function with Gal-3 neutralizing antibody decreased the microvessel density in ischemic brain. We currently show that Gal-3 significantly increases the viability of microglia BV2 cells subjected to oxygen glucose deprivation (OGD) and re-oxygenation. Exogenous Gal-3 promoted the formation of pro-angiogenic structures in an in vitro human umbilical vein endothelial (HUVEC) and BV2 cell co-culture model. Gal-3 induced angiogenesis was associated with increased expression of vascular endothelial growth factor. The conditioned medium of BV2 cells exposed to OGD contained increased Gal-3 levels, and promoted the formation of pro-angiogenic structures in an in vitro HUVEC culture model. Gal-3 also augmented the in vitro migratory potential of BV2 microglia. Gal-3 mediated functions were associated with increased levels of integrin-linked kinase (ILK) signaling as demonstrated by the impaired angiogenesis and migration of BV2 cells following targeted silencing of ILK expression by siRNA. Furthermore, we show that ILK levels correlate with the levels of phos-AKT and ERK1/2 that are downstream effectors of ILK pathway. Taken together, our studies indicate that Gal-3 contributes to angiogenesis and microglia migration that may have implications in post stroke repair.

A novel autologous cell-based therapy to promote diabetic wound healing

OBJECTIVES

We have previously shown that stromal cell-derived factor-1α (SDF-1α) is downregulated within diabetic cutaneous wounds, and that direct application of recombinant SDF-1α increases wound closure rates, neovascularization, and endothelial progenitor cell (EPC) recruitment. However, increased wound levels of exogenous SDF-1α results in elevated systemic levels of this proangiogenic chemokine that raises concerns for tumorigenesis and inflammation. We now seek to test the efficacy of a novel, safer cell-based therapy (CBT) employing ex vivo primed bone marrow-derived stem cells (BMDSC) with SDF-1α. We also elucidate the mechanism of action of this new approach for accelerating diabetic wound healing.

METHODS

Unfractionated BMDSC from diabetic Lepr mice were incubated for 20 hours with SDF-1α (100 ng/mL) or bovine serum albumin (control). Pretreated BMDSC (1 × 10) were injected subcutaneously into full-thickness skin wounds in Lepr mice (n = 8 per group). Wound closure rates, capillary density, and the recruitment of EPC were assessed with serial photography, DiI perfusion, confocal microscopy, and immunohistochemistry. The expression of molecular targets, which may mediate prohealing/proangiogenic effects of SDF-1α-primed BMDSC was evaluated by polymerase chain reaction array and immunoblotting assay. The biological function of a potential mediator was tested in a mouse wound-healing model. Serum SDF-1α levels were measured with enzyme-linked immunosorbent assay (ELISA).

RESULTS

SDF-1α-primed BMDSC significantly promote wound healing (P < 0.0001), neovascularization (P = 0.0028), and EPC recruitment (P = 0.0059). Gene/protein expression studies demonstrate upregulation of Ephrin Receptor B4 and plasminogen as downstream targets potentially mediating the prohealing and proangiogenic responses. Ex vivo BMDSC activation and the subsequent inoculation of cells into wounds does not increase systemic SDF-1α levels.

CONCLUSIONS

We report a novel CBT that is highly effective in promoting healing and neovascularization in a murine model of type 2 diabetes. Furthermore, we identify new molecular targets that may be important for advancing the field of wound healing.

The impact of the stromal cell-derived factor-1-3'A and E-selectin S128R polymorphisms on breast cancer

Breast cancer is prone to metastasis even in early stage disease. Stromal cell-derived factor-1 (SDF-1) is a chemokine that has been associated with the egress of cancer cells from the primary focus and homing to distant sites, while E-selectin has been implicated in their trans-endothelial migration. This study was performed to evaluate the association between SDF-1-3'A and E-selectin S128R-two polymorphisms associated with enhanced function-and the risk of breast cancer, as well as their influence on breast cancer outcome. A retrospective analysis was conducted on 261 patients and 480 healthy controls using PCR-RFLP. The frequencies for the wild-type (GG), GA and AA genotypes of SDF-1 were 43.7, 45.2, and 11.1 % in patients, and 51.5, 41.3, and 7.3 % in healthy controls, respectively, while the SDF-1-3'A allelic frequency was 33.7 % at patients and 27.9 % at controls. The SDF-1-3'A carrier group of patients and the A allele of SDF-1 were overrepresented among the breast cancer cases (p = 0.04 and 0.02, respectively). For the E-selectin S128R polymorphism, the frequencies for the wild-type (AA), AC and CC genotypes were 58.6, 38.3, and 3.1 % in patients and 63.8, 31.4, and 3.8 % in controls, respectively, while the C allelic frequency was 22.2 % for patients and 19.5 % for controls. The CC genotype was associated with poorer survival. Otherwise, no significant association was detected between examined genotypes and tumor characteristics. Overall, our findings support that the SDF-1-3'A confers increased susceptibility to breast cancer and that the E-selectin S128R CC genotype may be related to poorer prognosis. Investigation in bigger cohorts of patients is warranted.

The expanding family of bone marrow homing factors for hematopoietic stem cells: stromal derived factor 1 is not the only player in the game

The α-chemokine stromal derived factor 1 (SDF-1), which binds to the CXCR4 and CXCR7 receptors, directs migration and homing of CXCR4⁺ hematopoietic stem/progenitor cells (HSPCs) to bone marrow (BM) and plays a crucial role in retention of these cells in stem cell niches. However, this unique role of SDF-1 has been recently challenged by several observations supporting SDF-1-CXCR4-independent BM homing. Specifically, it has been demonstrated that HSPCs respond robustly to some bioactive lipids, such as sphingosine-1-phosphate (S1P) and ceramide-1-phosphate (C1P), and migrate in response to gradients of certain extracellular nucleotides, including uridine triphosphate (UTP) and adenosine triphosphate (ATP). Moreover, the responsiveness of HSPCs to an SDF-1 gradient is enhanced by some elements of innate immunity (e.g., C3 complement cascade cleavage fragments and antimicrobial cationic peptides, such as cathelicidin/LL-37 or β2-defensin) as well as prostaglandin E2 (PGE2). Since all these factors are upregulated in BM after myeloblative conditioning for transplantation, a more complex picture of homing emerges that involves several factors supporting, and in some situations even replacing, the SDF-1-CXCR4 axis.

GMP-adapted overexpression of CXCR4 in human mesenchymal stem cells for cardiac repair

BACKGROUND

Human mesenchymal stem cells (MSC) have been utilized for cardiac regeneration after myocardial damage. Their clinical effects are marginal and only a minority of administered cells could make their way into the myocardium. The chemokine receptor CXCR4 has been identified as crucial for migration and homing of stem cells. In this study we overexpressed CXCR4 on human MSC to improve cell trafficking and tissue repair.

METHODS

Human MSC were isolated from the spongiosa of tibia and femur as well as from pelvic bone marrow. MSC were characterized by differentiation assays and FACS analysis. CXCR4 was overexpressed by mRNA-nucleofection. Intracellular signaling was analyzed to demonstrate functionality of CXCR4. The modified Boyden chamber, wounding assays and time lapse microscopy were utilized to investigate MSC migration.

RESULTS

MSC did not express relevant amounts of CXCR4 spontaneously. CXCR4 could be overexpressed in 93% of MSC with a cell viability of 62%. Functionality of the overexpressed CXCR4 was demonstrated by a significant cytosolic Ca(2+) increase and activation of different MAP kinases followed by SDF-1α stimulation. In contrast no improvement of cell migration could be observed. There was a strong basal MSC chemokinesis independent from CXCR4 expression.

CONCLUSIONS

CXCR4 could be effectively overexpressed in human MSC by mRNA-nucleofection. Despite functionality of CXCR4 MSC were characterized by a strong basal chemokinesis that could not be further enhanced by CXCR4 overexpression. As isolation, culture and nucleofection of pelvic bone marrow-derived MSC basically fulfill the GMP-requirements our approach seems suited for an in vivo application in patients.

Advanced glycation end products impair the migration, adhesion and secretion potentials of late endothelial progenitor cells

Background

Endothelial progenitor cells (EPCs), especially late EPCs, play a critical role in endothelial maintenance and repair, and postnatal vasculogenesis. Advanced glycation end products (AGEs) have been shown to impair EPC functions, such as proliferation, migration and adhesion. However, their role in the regulation of the production of vasoactive substances in late EPCs is less well defined.

Methods

Passages of 3~5 EPCs, namely late EPCs, were cultured with different concentrations (0~500 μg/ml) of AGEs, and the apoptosis, adhesion and migration were subsequently determined. The release of vasoactive substances, such as stromal cell-derived factor-1 (SDF-1), nitric oxide (NO), prostaglandin I₂ (PGI₂), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA), and in addition the activity of superoxide dismutase (SOD), were evaluated by ELISA. At the same time, the gene and protein expressions of CXCR4 were assayed by real-time RT-PCR and western-blot.

Results

AGEs promoted late EPC apoptosis. Moreover, AGEs impaired late EPC migration and adhesion in a concentration-dependent manner. Accordingly, the production of SDF-1 was decreased by AGEs. Although the CXCR4 expressions of late EPCs were up-regulated for AGE concentrations of 50, 100 or 200 μg/ml, a marked decrease was observed for the higher concentration of 500 μg/ml. Furthermore, co-culturing with AGEs decreased the levels of NO, t-PA, PGI_2, and the activity of SOD but up-regulated the production of PAI-1.

Conclusion

Our data provide evidence that AGEs play an important role in impairing late EPC functions, which could contribute to the development of vascular diseases in diabetes.

Cardiovascular biology of the incretin system

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that enhances glucose-stimulated insulin secretion and exerts direct and indirect actions on the cardiovascular system. GLP-1 and its related incretin hormone, glucose-dependent insulinotropic polypeptide, are rapidly inactivated by the enzyme dipeptidyl peptidase 4 (DPP-4), a key determinant of incretin bioactivity. Two classes of medications that enhance incretin action, GLP-1 receptor (GLP-1R) agonists and DPP-4 inhibitors, are used for the treatment of type 2 diabetes mellitus. We review herein the cardiovascular biology of GLP-1R agonists and DPP-4 inhibitors, including direct and indirect effects on cardiomyocytes, blood vessels, adipocytes, the control of blood pressure, and postprandial lipoprotein secretion. Both GLP-1R activation and DPP-4 inhibition exert multiple cardioprotective actions in preclinical models of cardiovascular dysfunction, and short-term studies in human subjects appear to demonstrate modest yet beneficial actions on cardiac function in subjects with ischemic heart disease. Incretin-based agents control body weight, improve glycemic control with a low risk of hypoglycemia, decrease blood pressure, inhibit the secretion of intestinal chylomicrons, and reduce inflammation in preclinical studies. Nevertheless, there is limited information on the cardiovascular actions of these agents in patients with diabetes and established cardiovascular disease. Hence, a more complete understanding of the cardiovascular risk to benefit ratio of incretin-based therapies will require completion of long-term cardiovascular outcome studies currently underway in patients with type 2 diabetes mellitus.

A novel perspective on stem cell homing and mobilization: review on bioactive lipids as potent chemoattractants and cationic peptides as underappreciated modulators of responsiveness to SDF-1 gradients

Hematopoietic stem progenitor cells (HSPCs) respond robustly to α-chemokine stromal-derived factor-1 (SDF-1) gradients, and blockage of CXCR4, a seven-transmembrane-spanning G(αI)-protein-coupled SDF-1 receptor, mobilizes HSPCs into peripheral blood. Although the SDF-1-CXCR4 axis has an unquestionably important role in the retention of HSPCs in bone marrow (BM), new evidence shows that, in addition to SDF-1, the migration of HSPCs is directed by gradients of the bioactive lipids sphingosine-1 phosphate and ceramide-1 phosphate. Furthermore, the SDF-1 gradient may be positively primed/modulated by cationic peptides (C3a anaphylatoxin and cathelicidin) and, as previously demonstrated, HSPCs respond robustly even to very low SDF-1 gradients in the presence of priming factors. In this review, we discuss the role of bioactive lipids in stem cell trafficking and the consequences of HSPC priming by cationic peptides. Together, these phenomena support a picture in which the SDF-1-CXCR4 axis modulates homing, BM retention and mobilization of HSPCs in a more complex way than previously envisioned.