Small peptide analogue of SDF-1alpha supports survival of cord blood CD34+ cells in synergy with other cytokines and enhances their ex vivo expansion and engraftment into nonobese diabetic/severe combined immunodeficient mice

Study of stem cell homing & self-renewal marker gene profile of ex vivo expanded human CD34+ cells manipulated with a mixture of cytokines & stromal cell-derived factor 1

BACKGROUND & OBJECTIVES

Next generation transplantation medicine aims to develop stimulating cocktail for increased ex vivo expansion of primitive hematopoietic stem and progenitor cells (HSPC). The present study was done to evaluate the cocktail GF (Thrombopoietin + Stem Cell factor + Flt3-ligand) and homing-defining molecule Stromal cell-derived factor 1 (SDF1) for HSPC ex vivo expansion.

METHODS

Peripheral blood stem cell (n=74) harvests were analysed for CD34hiCD45lo HSPC. Immunomagnetically enriched HSPC were cultured for eight days and assessed for increase in HSPC, colony forming potential in vitro and in vivo engrafting potential by analyzing human CD45+ cells. Expression profile of genes for homing and stemness were studied using microarray analysis. Expression of adhesion/homing markers were validated by flow cytometry/ confocal microscopy.

RESULTS

CD34hiCD45lo HSPC expansion cultures with GF+SDF1 demonstrated increased nucleated cells (n=28, P+ cells (n=8, P=0.021) and increased colony forming units (cfu) compared to unstimulated and GF-stimulated HSPC. NOD-SCID mice transplanted with GF+SDF1-HSPC exhibited successful homing/engraftment (n=24, PInterpretation & conclusions: Cocktail of cytokines and SDF1 showed good potential to successfully expand HSPC which exhibited enhanced ability to generate multilineage cells in short-term and long-term repopulation assay. This cocktail-mediated stem cell expansion has potential to obviate the need for longer and large volume apheresis procedure making it convenient for donors.

Combined treatment with a CXCL12 analogue and antibiotics improves survival and neutrophil recruitment and function in murine sepsis

Previous studies demonstrated that the CXCL12 peptide analogue CTCE-0214 (CTCE) has beneficial effects in experimental sepsis induced by cecal ligation and puncture (CLP). We examined the hypothesis that CTCE recruits neutrophils (PMN) to the site of infection, enhances PMN function and improves survival of mice in CLP-induced sepsis with antibiotic treatment. Septic mice (n=15) were administered imipenem (25mg/kg) and CTCE (10 mg/kg) subcutaneously vs. vehicle control at designated intervals post-CLP. CTCE treatment increased PMN recruitment in CLP-induced sepsis as evidenced by increased PMN in blood by 2.4±0.6 fold at 18h, 2.9±0.6 fold at 24h, respectively and in peritoneal fluid by 2.0±0.2 fold at 24h vs. vehicle control. CTCE treatment reduced bacterial invasion in blood (CFU decreased 77±11%), peritoneal fluid (CFU decreased 78±9%) and lung (CFU decreased 79±8% vs. CLP vehicle). The improved PMN recruitment and bacterial clearance correlated with reduced mortality with CTCE treatment (20% vs. 67% vehicle controls). In vitro studies support the notion that CTCE augments PMN function by enhancing phagocytic activity (1.25±0.02 fold), increasing intracellular production of ROS (32±4%) and improving bacterial killing (CFU decreased 27±3%). These composite findings support the hypothesis that specific CXCL12 analogues with ancillary antibiotic treatment are beneficial in experimental sepsis, in part, by augmenting PMN recruitment and function. This article is protected by copyright. All rights reserved.

Endothelial progenitor cells and a stromal cell-derived factor-1α analogue synergistically improve survival in sepsis

RATIONALE

Endothelial progenitor cells (EPCs) have been associated with human sepsis but their role is incompletely understood. Stromal cell-derived factor (SDF)-1α facilitates EPC recruitment and is elevated in murine sepsis models. Previous studies have demonstrated that the SDF-1α analog CTCE-0214 (CTCE) is beneficial in polymicrobial sepsis induced by cecal ligation and puncture (CLP) in mice.

OBJECTIVES

We hypothesized that exogenously administered EPCs are also beneficial in CLP sepsis and that CTCE provides synergistic benefit.

METHODS

Mice were subjected to CLP and administered EPCs at varying doses, CTCE, or a combination of the two. Mouse survival, plasma miRNA expression, IL-10 production, and lung vascular leakage were determined. The in vitro effect of CTCE on miRNA expression and EPC function were determined.

MEASUREMENTS AND MAIN RESULTS

Survival was improved with EPC therapy at a threshold of 10(6) cells. In coculture studies, EPCs augmented LPS-induced macrophage IL-10 production. In vivo EPC administration in sepsis increased plasma IL-10, suppressed lung vascular leakage, attenuated liver and kidney injury, and augmented miR-126 and -125b expression, which regulate endothelial cell function and/or inflammation. When subthreshold numbers of EPCs were coadministered with CTCE in CLP mice they synergistically improved survival. We demonstrated that CTCE recruits endogenous EPCs in septic mice. In in vitro analysis, CTCE enhanced EPC proliferation, angiogenesis, and prosurvival signaling while inhibiting EPC senescence. These cellular effects were, in part, explained by the effect of CTCE on miR-126, -125b, -34a, and -155 expression in EPCs.

CONCLUSIONS

EPCs and CTCE represent important potential therapeutic strategies in sepsis.

Beneficial effect of a CXCR4 agonist in murine models of systemic inflammation

The chemokine CXC receptor 4 (CXCR4) is activated by stromal cell-derived factor (SDF-1α). CXCR4 may be part of a lipopolysaccharide (LPS) sensing co-clustering complex that modulates TLR4 activation and evidence suggest that SDF-1α can activate anti-inflammatory signaling pathways and suppress inflammation. In the present study we examined the hypothesis that the SDF-1α peptide analog and CXCR4 agonist CTCE-0214 is anti-inflammatory in three distinct models of murine systemic inflammation. Our findings demonstrate that CTCE-0214 in vivo significantly suppressed plasma tumor necrosis factor alpha (TNF-α) increases in acute endotoxemia and following zymosan-induced multiple organ dysfunction syndrome (MODS). In both models, CTCE-0214 did not suppress plasma increases in the anti-inflammatory cytokine interleukin (IL)-10. CTCE-0214 improved survival without antibiotics in a model of severe sepsis induced by cecal ligation and puncture (CLP). CTCE-0214 also decreased plasma increases in IL-6 but not TNF-α and IL-10 in response to CLP-induced inflammation. We demonstrated in a moderately severe model of CLP (one puncture) that IL-6 levels at 24 h were similar to sham controls. However in severe CLP (two punctures) plasma IL-6 levels were markedly elevated. Plasma SDF-1α levels varied inversely with the plasma IL-6. In addition to the beneficial effect of CTCE-0214 in these models of systemic inflammation in vivo, we also demonstrated that the analog dose dependently suppressed LPS-induced IL-6 production in bone marrow-derived macrophages. CTCE-0214 therefore may be beneficial in controlling inflammation sepsis and systemic inflammatory syndromes.

Mobilization and homing of hematopoietic stem cells

Hematopoietic stem cells (HSC) are a population of precursor cells that posses the capacity for self-renewal and multilineage differentiation. In the bone marrow (BM), HSCs warrant blood cell homeostasis, but at the same time a stable pool of functional cells must be constantly maintained. For this, HSCs constitute a model in which subpopulations of quiescent and active adult stem cells co-exist in the same tissue, in specific microenvironment called stem-cell "niches." These microenvironments keep the stem cells at quiescent (osteoblastic niche) for its self-renewal and activate the stem cells (vascular niche) for proliferation and/or injury repair, maintaining a dynamic balance between self-renewal and differentiation. HSC reside in the bone marrow but can be forces into the blood, a process termed mobilization used clinically to harvest large number of cells for transplantation. At the same time, homing to the BM is necessary to optimize cell engraftment. Here, we summarize current understanding of HSC niche characteristics, and the physiological and pathological mechanisms that guide HSC mobilization both within the BM and to distant niches in the periphery. Mobilization and Homing are mirror process depending on an interplay between chemokines, chemokine receptors, intracellular signaling, adhesion moleculas and proteases. The interaction between SDF-1/CXCL12 and its receptor CXCR4 is critical to retain HSCs within the bone marrow. Current mobilization strategies used in clinic, mainly G-CSF cytokine, are well tolerated but often produce suboptimal number of collected HSCs. Novel agents (AMD3100, stem cell factor, GROßT.) are being developed to enhance the mobilization to modify the signaling into the niche and boost the stem cell harvest, increasing the number of HSCs available for the transplant.

Agonists for the Chemokine Receptor CXCR4

The development of agonists for the chemokine receptor CXCR4 could provide promising therapeutic candidates. On the basis of previously forwarded two site model of chemokine–receptor interactions, we hypothesized that linking the agonistic N-terminus of SDF-1 to the T140 backbone would yield new high-affinity agonists of CXCR4. We developed chimeras with the agonistic SDF-1 N-terminus grafted to a T140 side chain and tested their binding affinity and chemotactic agonist activity. While chimeras with the peptide grafted onto position 12 of T140 remained high-affinity antagonists, those bearing the peptide on position 14 were in part agonists. One chimera was a full CXCR4 agonist with 25 nM affinity, and several chimeras showed low nanomolar affinities with partial agonist activity. Our results confirmed that we have developed high-affinity agonists of CXCR4.

Formation of an adherent hematopoietic expansion culture using fucoidan

Expansion of transplantable cord blood (CB) progenitors using a stroma requires provision of an exogenous cell source because of the low frequency of stromal precursor cells in CB. A simpler approach from a clinical regulatory perspective would be to provide synthetic extracellular matrix. The aim of this study was to characterize the effect on hematopoietic cell culture of fucoidan. The modulation of cytokine-driven hematopoietic cell expansion by fucoidan was investigated using two-level fractional and full factorial experimental designs. Mobilized peripheral blood (PB) CD34(+) cells were grown over 10 days in various combinations of FL, SCF, TPO, G-CSF, and SDF-1. Cultures were analyzed by immunophenotype. The effect of fucoidan on the divisional recruitment of CD34(+) cells was studied by CFDA-SE division tracking. Fucoidan was adsorbed by polystyrene to tissue culture plates and promoted formation of an adherent hematopoietic culture. Factorial design experiments with mobilized PB-CD34(+) cells showed that fucoidan reduced the production of CD34(+) cells and CD34(+)CXCR4(+) ratio but did not affect the production of monocytic, granulocytic, or megakaryocytic cells. The inhibitory effect of fucoidan on expansion of CB-CD34(+) cells was greater than mobilized PB. Division tracking analysis showed that CD34(+) cell generation times were lengthened by fucoidan. Fucoidan binds growth factors via their heparin-binding domain. The formation of an adherent hematopoietic culture system by fucoidan is most likely mediated by the binding of L-selectin and integrin-αMβ2 on myeloids. Fucoidan deserves further investigation as glycan scaffold that is suitable for immobilization of other matrix molecules thought to comprise blood stem cell niche.

Collagen IV significantly enhances migration and transplantation of embryonic stem cells: involvement of α2β1 integrin-mediated actin remodeling

Embryonic stem (ES) cell transplantation represents a potential means for the treatment of degenerative diseases and injuries. As appropriate distribution of transplanted ES cells in the host tissue is critical for successful transplantation, the exploration of efficient strategies to enhance ES cell migration is warranted. In this study we investigated ES cell migration under the influence of various extracellular matrix (ECM) proteins, which have been shown to stimulate cell migration in various cell models with unclear effects on ES cells. Using two mouse ES (mES) cell lines, ESC 26GJ9012-8-2 and ES-D3 GL, to generate embryoid bodies (EBs), we examined the migration of differentiating cells from EBs that were delivered onto culture surfaces coated with or without collagen I, collagen IV, Matrigel, fibronectin, and laminin. Among these ECM proteins, collagen IV exhibited maximal migration enhancing effect. mES cells expressed α2 and β1 integrin subunits and the migration enhancing effect of collagen IV was prevented by RGD peptides as well as antibodies against α2 and β1 integrins, indicating that the enhancing effect of collagen IV on cell migration was mediated by α2β1 integrin. Furthermore, staining of actin cytoskeleton that links to integrins revealed well-developed stress fibers and long filopodia in mES cells cultured on collagen IV, and the actin-disrupting cytochalasin D abolished the collagen IV-enhanced cell migration. In addition, pretreatment of undifferentiated or differentiated mES cells with collagen IV resulted in improved engraftment and growth after transplantation into the subcutaneous tissue of nude mice. Finally, collagen IV pretreatment of osteogenically differentiated mES cells increased osteogenic differentiation-like tissue and decreased undifferentiation-like tissue in the grafts grown after transplantation. Our results demonstrated that collagen IV significantly enhanced the migration of differentiating ES cells through α2β1 integrin-mediated actin remodeling and could promote ES cell transplantation efficiency, which may be imperative to stem cell therapy.

The tetraspanin CD9 regulates migration, adhesion, and homing of human cord blood CD34+ hematopoietic stem and progenitor cells

The stromal cell-derived factor-1 (SDF-1)/chemokine C-X-C receptor 4 (CXCR4) axis plays a critical role in homing and engraftment of hematopoietic stem/progenitor cells (HSCs) during bone marrow transplantation. To investigate the transcriptional regulation provided by this axis, we performed the first differential transcriptome profiling of human cord blood CD34(+) cells in response to short-term exposure to SDF-1 and identified a panel of genes with putative homing functions. We demonstrated that CD9, a member of the tetraspanin family of proteins, was expressed in CD34(+)CD38(-/lo) and CD34(+)CD38(+) cells. CD9 levels were enhanced by SDF-1, which simultaneously down-regulated CXCR4 membrane expression. Using specific inhibitors and activators, we demonstrated that CD9 expression was modulated via CXCR4, G-protein, protein kinase C, phospholipase C, extracellular signal-regulated kinase, and Janus kinase 2 signals. Pretreatment of CD34(+) cells with the anti-CD9 monoclonal antibody ALB6 significantly inhibited SDF-1-mediated transendothelial migration and calcium mobilization, whereas adhesion to fibronectin and endothelial cells was enhanced. Pretreatment of CD34(+) cells with ALB6 significantly impaired their homing to bone marrow and spleen of sublethally irradiated NOD/SCID (nonobese diabetic/severe combined immune-deficient) mice. Sorted CD34(+)CD9(-) cells displayed lower bone marrow homing capacity compared with that of total CD34(+) cells. CD9 expression on homed CD34(+) cells was significantly up-regulated in vivo. Our results indicate that CD9 might possess specific functions in HSC homing.

Maitake beta-glucan enhances umbilical cord blood stem cell transplantation in the NOD/SCID mouse

Beta glucans are cell wall constituents of yeast, fungi and bacteria, as well as mushrooms and barley. Glucans are not expressed on mammalian cells and are recognized as pathogen-associated molecular patterns (PAMPS) by pattern recognition receptors (PRR). Beta glucans have potential activity as biological response modifiers for hematopoiesis and enhancement of bone marrow recovery after injury. We have reported that Maitake beta glucan (MBG) enhanced mouse bone marrow (BMC) and human umbilical cord blood (CB) cell granulocyte-monocyte colony forming unit (GM-CFU) activity in vitro and protected GM-CFU forming stem cells from doxorubicin (DOX) toxicity. The objective of this study was to determine the effects of MBG on expansion of phenotypically distinct subpopulations of progenitor and stem cells in CB from full-term infants cultured ex vivo and on homing and engraftment in vivo in the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse. MBG promoted a greater expansion of CD34+CD33+CD38- human committed hematopoietic progenitor (HPC) cells compared to the conventional stem cell culture medium (P = 0.002 by ANOVA). CD34+CXCR4+CD38- early, uncommitted human hematopoietic stem cell (HSC) numbers showed a trend towards increase in response to MBG. The fate of CD34+ enriched CB cells after injection into the sublethally irradiated NOS/SCID mouse was evaluated after retrieval of xenografted human CB from marrow and spleen by flow cytometric analysis. Oral administration of MBG to recipient NOS/SCID mice led to enhanced homing at 3 days and engraftment at 6 days in mouse bone marrow (P = 0.002 and P = 0.0005, respectively) compared to control mice. More CD34+ human CB cells were also retrieved from mouse spleen in MBG treated mice at 6 days after transplantation. The studies suggest that MBG promotes hematopoiesis through effects on CD34+ progenitor cell expansion ex vivo and when given to the transplant recipient could enhance CD34+ precursor cell homing and support engraftment.

Chemokine receptor CXCR4 as a therapeutic target for neuroectodermal tumors

Chemokines (chemotactic cytokines) are a family of proteins associated with the trafficking and activation of leukocytes and other cell types in immune surveillance and inflammatory response. Besides their roles in the immune system, they play pleiotropic roles in tumor initiation, promotion, and progression. Chemokines can be classified into four subfamilies of chemokines, CXC, CC, C, or CX3C, based on their number and spacing of conserved cysteine residues near the N-terminus. This CXC subfamily can be further subclassified into two groups, depending on the presence or absence of a tripeptide motif glutamic acid-leucine-arginine (ELR) in the N-terminal domain. ELR(-)CXCL12, which binds to CXCR4 has been frequently implicated in various cancers. Over the past several years, studies have increasingly shown that the CXCR4/CXCL12 axis plays critical roles in tumor progression, such as invasion, angiogenesis, survival, homing to metastatic sites. This review focuses on involvement of CXCR4/CXCL12 interaction in neuroectodermal cancers and their therapeutic potentials. As an attractive therapeutic target of CXCR4/CXCL12 axis for cancer chemotherapy, development history and application of CXCR4 antagonists are described.

Humanized SCID mouse models for biomedical research

There is a growing need for effective animal models to carry out experimental studies on human hematopoietic and immune systems without putting individuals at risk. Progress in development of small animal models for the in vivo investigation of human hematopoiesis and immunity has seen three major breakthroughs over the last three decades. First, CB 17-Prkdc(scid) (abbreviated CB 17-scid) mice were discovered in 1983, and engraftment of these mice with human fetal tissues (SCID-Hu model) and peripheral blood mononuclear cells (Hu-PBL-SCID model) was reported in 1988. Second, NOD-scid mice were developed and their enhanced ability to engraft with human hematolymphoid tissues as compared with CB17-scid mice was reported in 1995. NOD-scid mice have been the "gold standard" for studies of human hematolymphoid engraftment in small animal models over the last 10 years. Third, immunodeficient mice bearing a targeted mutation in the IL-2 receptor common gamma chain (IL2rgamma(null)) were developed independently by four groups between 2002 and 2005, and a major increase in the engraftment and function of human hematolymphoid cells as compared with NOD-scid mice has been reported. These new strains of immunodeficient IL2rgamma(null) mice are now being used for studies in human hematopoiesis, innate and adaptive immunity, autoimmunity, infectious diseases, cancer biology, and regenerative medicine. In this chapter, we discuss the current state of development of these strains of mice, the remaining deficiencies, and how approaches used to increase the engraftment and function of human hematolymphoid cells in CB 17-scid mice and in previous models based on NOD-scid mice may enhance human hematolymphoid engraftment and function in NOD-scid IL2rgamma(null) mice.

The plant mannose-binding lectin NTL preserves cord blood haematopoietic stem/progenitor cells in long-term culture and enhances theirex vivoexpansion

Ex vivo expansion of haematopoietic stem and progenitor cells in cytokine combinations is effective in promoting differentiation and proliferation of multilineage progenitor cells, but often results in reduction of self-renewable stem cells. This study investigated the effect of a mannose-binding lectin, NTL, purified from Narcissus tazetta var. chinensis, on prolonged maintenance and expansion of cord blood CD34+ cells. Our results showed that the presence of NTL or Flt-3 ligand (FL) significantly preserved a population of early stem/progenitor cells in a serum- and cytokine-free culture for 35 d. The effect of NTL on the ex vivo expansion of CD34+ cells in the presence of stem cell factor, thrombopoietin (TPO) and FL was also investigated. NTL-enhanced expansion of early progenitors (CD34+, CD34+CD38-, mixed colony-forming units and CFU-GEMM) and committed progenitor cells (granulocyte CFU, erythroid burst-forming units/CFU and megakayocyte CFU) after 8 and 12 d of culture. Six weeks after transplanting 12 d-expanded cells to non-obese diabetic severe combined immunodeficient mice, increased engraftment of human CD45+ cells was observed in the bone marrow of animals that received NTL-treated cells. The dual functions of NTL on long-term preservation and expansion of early stem/multilineage progenitor cells could be developed for applications in various cell therapy strategies, such as the clinical expansion of CD34+ cells for transplantation.

Promoting effects of serotonin on hematopoiesis: ex vivo expansion of cord blood CD34+ stem/progenitor cells, proliferation of bone marrow stromal cells, and antiapoptosis

Serotonin is a monoamine neurotransmitter that has multiple extraneuronal functions. We previously reported that serotonin exerted mitogenic stimulation on megakaryocytopoiesis mediated by 5-hydroxytryptamine (5-HT)2 receptors. In this study, we investigated effects of serotonin on ex vivo expansion of human cord blood CD34+ cells, bone marrow (BM) stromal cell colony-forming unit-fibroblast (CFU-F) formation, and antiapoptosis of megakaryoblastic M-07e cells. Our results showed that serotonin at 200 nM significantly enhanced the expansion of CD34+ cells to early stem/progenitors (CD34+ cells, colony-forming unit-mixed [CFU-GEMM]) and multilineage committed progenitors (burst-forming unit/colony-forming unit-erythroid [BFU/CFU-E], colony-forming unit-granulocyte macrophage, colony-forming unit-megakaryocyte, CD61+ CD41+ cells). Serotonin also increased nonobese diabetic/severe combined immunodeficient repopulating cells in the expansion culture in terms of human CD45+, CD33+, CD14+ cells, BFU/CFU-E, and CFU-GEMM engraftment in BM of animals 6 weeks post-transplantation. Serotonin alone or in addition to fibroblast growth factor, platelet-derived growth factor, or vascular endothelial growth factor stimulated BM CFU-F formation. In M-07e cells, serotonin exerted antiapoptotic effects (annexin V, caspase-3, and propidium iodide staining) and reduced mitochondria membrane potential damage. The addition of ketanserin, a competitive antagonist of 5-HT2 receptor, nullified the antiapoptotic effects of serotonin. Our data suggest the involvement of serotonin in promoting hematopoietic stem cells and the BM microenvironment. Serotonin could be developed for clinical ex vivo expansion of hematopoietic stem cells for transplantation. Disclosure of potential conflicts of interest is found at the end of this article.

Maternal plasma or human serum albumin in wash buffer enhances enrichment and ex vivo expansion of human umbilical cord blood CD34+ cells

Umbilical cord blood is a valuable source of haemopoietic stem/progenitor cells (HSC) for transplantation. This study explored the effect of maternal plasma/human serum albumin (HSA) in the purification and culture conditions of CD34+ cells derived from human umbilical cord blood. During CD34+ cell enrichment, including maternal plasma or HSA instead of fetal bovine serum (FBS) in the wash buffer, significantly increased the purity and the fold expansion of CD34+ cells. The increase in fold expansion of CD34+ cells was independent of CD34+ cell purity before expansion. With FBS, the mean fold expansion of CD34+ cells and total nucleated cells on day 7 was 9.7 +/- 5.5 and 39.7 +/- 13.7 respectively. The use of maternal plasma increased the mean fold expansion of CD34+ cells and total nucleated cells on day 7 to 28.2 +/- 6.7 and 71.5 +/- 15.4 respectively. When HSA was added to wash buffer, the mean fold expansion of CD34+ cells and total nucleated cells were 30.4 +/- 10.5 and 83.5 +/- 24.8 respectively. No statistical significance was found between using HSA and maternal plasma on total cell and CD34+ cell expansion. We propose that HSA in maternal plasma was responsible for the positive effect on CD34+ cell enrichment and expansion.

The many facets of SDF-1alpha, CXCR4 agonists and antagonists on hematopoietic progenitor cells

Stromal cell-derived factor-1alpha (SDF-1α) has pleiotropic effects on hematopoietic progenitor cells (HPCs). We have monitored podia formation, migration, proliferation, and cell-cell adhesion of human HPC under the influence of SDF-1α, a peptide agonist of CXCR4 (CTCE-0214), a peptide antagonist (CTCE-9908), and a nonpeptide antagonist (AMD3100). Whereas SDF-1α induced migration of CD34⁺ cells in a dose-dependent manner, CTCE-0214, CTCE-9908, and AMD3100 did not induce chemotaxis in this concentration range albeit the peptides CTCE-0214 and CTCE-9908 increased podia formation. Cell-cell adhesion of HPC to human mesenchymal stromal cells was impaired by the addition of SDF-1α, CTCE-0214, and AMD3100. Proliferation was not affected by SDF-1α or its analogs. Surface antigen detection of CXCR4 was reduced upon treatment with SDF-1α or AMD3100 and it was enhanced by CTCE-9908. Despite the fact that all these molecules target the same CXCR4 receptor, CXCR4 agonists and antagonists have selective effects on different functions of the natural molecule.

Enhanced In Vivo Homing of Uncultured and Selectively Amplified Cord Blood CD34+Cells by Cotransplantation with Cord Blood-Derived Unrestricted Somatic Stem Cells

Mesenchymal stem cells have been implicated as playing an important role in stem cell engraftment. Recently, a new pluripotent population of umbilical cord blood (UCB) cells, unrestricted somatic stem cells (USSCs), with intrinsic and directable potential to develop into mesodermal, endodermal, and ectodermal fates, has been identified. In this study, we evaluated the capacity of ex vivo expanded USSCs to influence the homing of UCB-derived CD34(+) cells into the marrow and spleen of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. USSCs induced a significant enhancement of CD34(+) cell homing to both bone marrow and spleen (2.2 +/- 0.3- and 2.4 +/- 0.6-fold, respectively; p < .05), with a magnitude similar to that induced by USSCs that had been thawed prior to transplantation. The effect of USSCs was dose-dependent and detectable at USSC:CD34(+) ratios of 1:1 and above. Enhanced marrow homing by USSCs was unaltered by extensive culture passaging of the cells, as similar enhancement was observed for both early-passage (passage 5 [p5]) and late-passage (p10) USSCs. The homing effect of USSCs was also reflected in an increased proportion of NOD/SCID mice exhibiting significant human cell engraftment 6 weeks after transplantation, with a similar distribution of myeloid and lymphoid components. USSCs enhanced the homing of cellular products of ex vivo expanded UCB lineage-negative (lin(-)) cells, generated in 14-day cultures by Selective Amplification. The relative proportion of homing CD34(+) cells within the culture-expanded cell population was unaltered by USSC cotransplantation. Production of stromal-derived factor-1 (SDF-1) by USSCs was detected by both gene expression and protein released into culture media of these cells. Knockdown of SDF-1 production by USSCs using lentiviral-SiRNA led to a significant (p < .05) reduction in USSC-mediated enhancement of CD34(+) homing. Our findings thus suggest a clinical potential for using USSCs in facilitating homing and engraftment for cord blood transplant recipients.

In vivo gene transfer into adult stem cells in unconditioned mice by in situ delivery of a lentiviral vector

The potential of in vivo lentivirus-mediated bone marrow stem cell gene transfer by bone cavity injection, which could take full advantage of any source of stem cells present there, has not been previously explored. Such an approach may avoid several difficulties encountered by ex vivo hematopoietic stem cell (HSC) gene transfer. We sought to determine if efficient gene transfer could be achieved in HSC and mesenchymal stem/progenitor cells (MSC) by intrafemoral injection of a lentivirus vector in mice. Four months after injection, up to 12% GFP-expressing cells were observed in myeloid and lymphoid subpopulations. Significant transduction efficiencies were seen in Lin(-)c-kit(+)Sca1(+) HSC/progenitors and CFU with multilineage potential, which were also confirmed by duplex PCR analysis of progenitor-derived colonies. Four months after secondary BMT, we observed 8.1 to 15% vector(+) CFU in all recipients. Integration analysis by LAM-PCR demonstrated that multiple transduced clones contributed to hematopoiesis in these animals. We also showed that GFP-expressing MSC retained multilineage differentiation potential, with 2.9 to 8.8% GFP-containing CFU-fibroblasts detected in both injected and BMT recipients. Our data provide evidence that adult stem cells in bone marrow can be efficiently transduced "in situ" by in vivo vector administration without preconditioning. This approach could lead to a novel application for treatment of human diseases.