Current understanding of stem cell mobilization: the roles of chemokines, proteolytic enzymes, adhesion molecules, cytokines, and stromal cells

PTH/SDF-1α cotherapy promotes proliferation, migration and osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVES

Stromal cell-derived factor-1α (SDF-1α) plays an important role in tissue regeneration in various tissues including the periodontium. A potential limitation for its use derives from its sensitivity to cleavage by dipeptidyl peptidase-IV (DPP-IV). Parathyroid hormone (PTH) reduces enzymatic activity of DPP-IV and is suggested to be a promising agent for periodontal tissue repair. The purpose of this study was to provide insight into how SDF-1α and intermittent PTH treatment might affect proliferation, migration and osteogenic differentiation of human periodontal ligament stem cells (PDLSCs) in vitro.

MATERIALS AND METHODS

PDLSCs were isolated by the limiting dilution method. Surface markers were quantified by flow cytometry. Cell-counting kit-8 (CCK8), cell migration assay, alkaline phosphatase (ALP) activity assay, alizarin red staining and RT-PCR were used to determine viability, migration and osteogenic differentiation of PDLSCs.

RESULTS

PDLSCs were positive for CD44, CD73, CD90, CD105, CD166 and STRO-1 and negative for CD14, CD34 and CD45. PTH/SDF-1α cotherapy significantly promoted cell proliferation, chemotactic capability, ALP activity and mineral deposition (P<.05). Gene expression level of bone sialoprotein (BSP), runt-related transcription factor 2 (Runx2) and osteocalcin (OCN) were all up-regulated (P<.05).

CONCLUSIONS

PTH/SDF-1α cotherapy promoted proliferation, migration and osteogenic differentiation of PDLSCs in vitro. Cotherapy seemed to have potential to promote periodontal tissue regeneration by facilitating chemotaxis of PDLSCs to the injured site, followed by promoting proliferation and osteogenic differentiation of these cells.

Phenotypic profile of dendritic and T cells in the lymph node of Balb/C mice with breast cancer submitted to dendritic cells immunotherapy

Breast cancer (BC) is the most common malignant neoplasm and the cause of death by cancer among women worldwide. Its development influenced by various mutations that occur in the tumor cell and by the immune system's status, which has a direct influence on the tumor microenvironment and, consequently, on interactions with non-tumor cells involved in the immunological response. Strategies using dendritic cells (DCs) or antigen-presenting cells (APCs), therapeutic mode, in cancer have been developed for some time. The proper interaction between DCs and T cells upon antigen presentation is of greatest importance for an antitumor immune response activation. Thus, various receptors on the surface of T cells must be able to recognize ligands that are located on the surface of APCs. However, little is known about the real behavior and interaction forms of CDs and T cells after vaccination. Due to the crucial importance of DCs in an effective anti-tumor immune response activation and the search for compliant results in inducing this response by immunotherapies with DCs, the phenotypic profile of DCs and T cells in lymph nodes obtained from female Balb/C mice with breast cancer induced by 4T1 cells and DCs treated with vaccines was investigated. We evaluated through flow cytometry based on the surface and intracellular molecules marking; as well as the presence of cytokines and chemokines, IL-2, IL-4, IL-10, IL-12, IFN-γ, TNF-α and TGF-β in the supernatant of the culture of Balb/C lymph nodes by ELISA. The results show that the vaccination with DCs, in the maturation parameters used in this study, was able to stimulate the secretion of cytokines such as IFN-γ and IL-12 and inhibit the secretion of TGF-β and IL-10 in nodal lymph infiltrates, as well as co-stimulatory activating (CD86) and adhesion molecules in DCs and T cells LFA-1/ICAM-1 and inhibit the secretion of CTLA-4 present in lymph nodes. Facts that led to aTh1 profile polarization, immuno competent in relation to breast cancer. We indirectly evaluated the interaction between DCs and T cells dependent on the vaccination with DCs in tumor draining lymph nodes, in breast cancer in Balb/C mice and we believe that, this way, we will be able to achieve a model vaccine protocol in the future, based on the correct interaction between cells that enable the induction of anti-tumor effective response. Breast cancer (BC) is the most common malignant neoplasm and the cause of death by cancer among women worldwide. Its development influenced by various mutations that occur in the tumor cell and by the immune system's status, which has a direct influence on the tumor microenvironment and, consequently, on interactions with non-tumor cells involved in the immunological response. Strategies using dendritic cells (DCs) or antigen-presenting cells (APCs), therapeutic mode, in cancer have been developed for some time. The proper interaction between DCs and T cells upon antigen presentation is of greatest importance for an antitumor immune response activation. Thus, various receptors on the surface of T cells must be able to recognize ligands that are located on the surface of APCs. However, little is known about the real behavior and interaction forms of DCs and T cells after vaccination. Due to the crucial importance of DCs in an effective anti-tumor immune response activation and the search for compliant results in inducing this response by immunotherapies with DCs, the phenotypic profile of DCs and T cells in lymph nodes obtained from female Balb/C mice with breast cancer induced by 4T1 cells and DCs treated with vaccines was investigated. We evaluated through flow cytometry based on the surface and intracellular molecules marking; as well as the presence of cytokines and chemokines, IL-2, IL-4, IL-10, IL-12, IFN-γ, TNF-α and TGF-β in the supernatant of the culture of Balb/C lymph nodes by ELISA. The results show that the vaccination with DCs, in the maturation parameters used in this study, was able to stimulate the secretion of cytokines such as IFN-γ and IL-12 and inhibit the secretion of TGF-β and IL-10 in nodal lymph infiltrates, as well as co-stimulatory activating (CD86) and adhesion molecules in DCs and T cells LFA-1/ICAM-1 and inhibit the secretion of CTLA-4 present in lymph nodes. Facts that led to aTh1 profile polarization, immuno competent in relation to breast cancer. We indirectly evaluated the interaction between DCs and T cells dependent on the vaccination with DCs in tumor draining lymph nodes, in breast cancer in Balb/C mice and we believe that, this way, we will be able to achieve a model vaccine protocol in the future, based on the correct interaction between cells that enable the induction of anti-tumor effective response.

Enhancement of Matrix Metalloproteinase-2 (MMP-2) as a Potential Chondrogenic Marker during Chondrogenic Differentiation of Human Adipose-Derived Stem Cells

Human adipose-derived stem cells (hASCs) have a capacity to undergo adipogenic, chondrogenic, and osteogenic differentiation. Recently, hASCs were applied to various fields including cell therapy for tissue regeneration. However, it is hard to predict the direction of differentiation of hASCs in real-time. Matrix metalloproteinases (MMPs) are one family of proteolytic enzymes that plays a pivotal role in regulating the biology of stem cells. MMPs secreted by hASCs are expected to show different expression patterns depending on the differentiation state of hASCs because biological functions exhibit different patterns during the differentiation of stem cells. Here, we investigated proteolytic enzyme activity, especially MMP-2 activity, in hASCs during their differentiation. The activities of proteolytic enzymes and MMP-2 were higher during chondrogenic differentiation than during adipogenic and osteogenic differentiation. During chondrogenic differentiation, mRNA expression of MMP-2 and the level of the active form of MMP-2 were increased, which also correlated with Col II. It is concluded that proteolytic enzyme activity and the level of the active form of MMP-2 were increased during chondrogenic differentiation, which was accelerated in the presence of Col II protein. According to our findings, MMP-2 could be a candidate maker for real-time detection of chondrogenic differentiation of hASCs.

Endothelial progenitor cells promote tumor growth and progression by enhancing new vessel formation

Tumor growth and progression require new blood vessel formation to deliver nutrients and oxygen for further cell proliferation and to create a neovascular network exit for tumor cell metastasis. Endothelial progenitor cells (EPCs) are a bone marrow (BM)-derived stem cell population that circulates in the peripheral circulation and homes to the tumor bed to participate in new blood vessel formation. In addition to structural support to nascent vessels, these cells can also regulate the angiogenic process by paracrine secretion of a number of proangiogenic growth factors and cytokines, thus playing a crucial role in tumor neovascularization and development. Inhibition of EPC-mediated new vessel formation may be a promising therapeutic strategy in tumor treatment. EPC-mediated neovascularization is a complex process that includes multiple steps and requires a series of cytokines and modulators, thus understanding the underlying mechanisms may provide anti-neovasculogenesis targets that may be blocked for the prevention of tumor development. The present review stresses the process and contribution of EPCs to the formation of new blood vessels in solid tumors, in an attempt to gain an improved understanding of the underlying cellular and molecular mechanisms involved, and to provide a potential effective therapeutic target for cancer treatment.

A novel hematopoietic progenitor cell mobilization regimen, utilizing bortezomib and filgrastim, for patients undergoing autologous transplant

Adequate hematopoietic progenitor cell (HPC) collection is critical for patients undergoing autologous HPC transplant (AHPCT). Historically, 15 - 30% of patients failed HPC mobilization with granulocyte-colony stimulating factor (G-CSF) alone. Bortezomib, a proteasome inhibitor, has been shown to down regulate very late antigen-4 (VLA-4), an adhesion molecule expressed on HPCs. In this pilot study, bortezomib was administered on days -11 and -8 at a dose of 1.3 mg/m² intravenously (IV) or subcutaneously (SQ), followed by G-CSF 10 mcg/kg SQ, on days -4 to -1 prior to HPC collection (Day 1). Nineteen patients, with multiple myeloma (n = 12) or non-Hodgkin lymphoma (n = 7) undergoing AHPCT for the first time, were enrolled. Patients were excluded if they had worse than grade II neuropathy or platelet count less than 100 x 10⁹ /L. Bortezomib was well tolerated and all patients had adequate HPC collections with no mobilization failures. One patient (6%) had a CD34⁺ cell count of 3.9 cells/µL on Day 1 and received plerixafor per institutional algorithm. Eleven patients completed HPC collection in 1 day and eight in 2 days. All patients underwent AHPCT and had timely neutrophil and platelet engraftment. Comparison with a historical control group of 70 MM and lymphoma patients, who were mobilized with G-CSF, showed significantly higher CD 34+ cells/kg collected in the bortezomib mobilization study group. Bortezomib plus G-CSF is an effective HPC mobilizing regimen worth investigating further in subsequent studies. J. Clin. Apheresis 31:559-563, 2016. © 2015 Wiley Periodicals, Inc.

Hematopoietic stem cells: multiparameter regulation

Hematopoietic stem cells (HSCs) are capable to self-renew with multi-potency which generated much excitement in clinical therapy. However, the main obstacle of HSCs in clinical application was insufficient number of HSCs which were derived from either bone marrow, peripheral blood or umbilical cord blood. This review briefly discusses the indispensable utility of growth factors and cytokines, stromal cells, extracellular matrix, bionic scaffold and microenvironment aiming to control the hematopoiesis in all directions and provide a better and comprehensive understanding for in vitro expansion of hematopoietic stem cells.

Measurements of CD34+/CD45-dim Stem Cells Predict Healing of Diabetic Neuropathic Wounds

Management of neuropathic foot ulcers in patients with diabetes (DFUs) has changed little over the past decade, and there is currently no objective method to gauge probability of successful healing. We hypothesized that studies of stem/progenitor cells (SPCs) in the early weeks of standard wound management could predict who will heal within 16 weeks. Blood and debrided wound margins were collected for 8 weeks from 100 patients undergoing weekly evaluations and treatment. SPC number and intracellular content of hypoxia-inducible factors (HIFs) were evaluated by flow cytometry and immunohistochemistry. More SPCs entered the bloodstream in the first 2 weeks of care in patients who healed (n = 37) than in those who did not (n = 63). Logistic regression demonstrated that the number of blood-borne SPCs and the cellular content of HIFs at study entry and the first-week follow-up visit predicted healing. Strong correlations were found among week-to-week assessments of blood-borne SPC HIF factors. We conclude that assays of SPCs during the first weeks of care in patients with DFUs can provide insight into how well wounds will respond and may aid with decisions on the use of adjunctive measures.

Induction of Neurorestoration From Endogenous Stem Cells

Neural stem cells (NSCs) persist in the subventricular zone lining the ventricles of the adult brain. The resident stem/progenitor cells can be stimulated in vivo by neurotrophic factors, hematopoietic growth factors, magnetic stimulation, and/or physical exercise. In both animals and humans, the differentiation and survival of neurons arising from the subventricular zone may also be regulated by the trophic factors. Since stem/progenitor cells present in the adult brain and the production of new neurons occurs at specific sites, there is a possibility for the treatment of incurable neurological diseases. It might be feasible to induce neurogenesis, which would be particularly efficacious in the treatment of striatal neurodegenerative conditions such as Huntington's disease, as well as cerebrovascular diseases such as ischemic stroke and cerebral palsy, conditions that are widely seen in the clinics. Understanding of the molecular control of endogenous NSC activation and progenitor cell mobilization will likely provide many new opportunities as therapeutic strategies. In this review, we focus on endogenous stem/progenitor cell activation that occurs in response to exogenous factors including neurotrophic factors, hematopoietic growth factors, magnetic stimulation, and an enriched environment. Taken together, these findings suggest the possibility that functional brain repair through induced neurorestoration from endogenous stem cells may soon be a clinical reality.

Activation of Hematopoietic Stem/Progenitor Cells Promotes Immunosuppression Within the Pre-metastatic Niche

Metastatic tumors have been shown to establish microenvironments in distant tissues that are permissive to disseminated tumor cells. Hematopoietic cells contribute to this microenvironment, yet the precise initiating events responsible for establishing the pre-metastatic niche remain unclear. Here, we tracked the developmental fate of hematopoietic stem and progenitor cells (HSPC) in tumor-bearing mice. We show that a distant primary tumor drives the expansion of HSPCs within the bone marrow and their mobilization to the bloodstream. Treatment of purified HSPCs cultured ex vivo with tumor-conditioned media induced their proliferation as well as their differentiation into immunosuppressive myeloid cells. We furthered tracked purified HSPCs in vivo and found they differentiated into myeloid-derived suppressor cells in early metastatic sites of tumor-bearing mice. The number of CD11b(+)Ly6g(+) cells in metastatic sites was significantly increased by HSPC mobilization and decreased if tumor-mediated mobilization was inhibited. Moreover, pharmacologic mobilization of HSPCs increased metastasis, whereas depletion of Gr1(+) cells abrogated the metastasis-promoting effects of HSPC mobilization. Finally, we detected elevated levels of HSPCs in the circulation of newly diagnosed cancer patients, which correlated with increased risk for metastatic progression. Taken together, our results highlight bone marrow activation as one of the earliest steps of the metastatic process and identify circulating HSPCs as potential clinical indicators of metastatic niche formation.

Dopamine mobilizes mesenchymal progenitor cells through D2-class receptors and their PI3K/AKT pathway

As the nervous system exerts direct and indirect effects on stem cells mobilization and catecholamines mobilize hematopoietic stem cells, we hypothesized that dopamine might induce mesenchymal progenitor cells (MPCs) mobilization. We show that dopamine induced in vitro MPCs migration through D2-class receptors, and their alternative phosphoinositide 3-kinase/Akt pathways. Also, administration of catecholamines induced in vivo mobilization of colony-forming unit-fibroblast in mice. In contrast, in vitro and in vivo MPCs migration was suppressed by D2-class receptors antagonists and blocking antibodies, consistent with dopamine signaling pathway implication. In humans, patients treated with L-dopa or catecholaminergic agonists showed a significant increase of a MPC-like population (CD45-CD31-CD34-CD105+) in their peripheral blood. These findings reveal a new link between catecholamines and MPCs mobilization and suggest the potential use of D2-class receptors agonists for mobilization of MPCs in clinical settings.

The Role of Stem Cells in the Etiology and Pathophysiology of Endometriosis

Human endometrium is a dynamic organ that normally undergoes repetitive cyclic regeneration. To enable this rapid regeneration, it is not surprising that the endometrium contains a reservoir of progenitor stem cells. However, this pool of cells that allows the growth of the endometrium also allows for unrestrained growth that can reach beyond the endometrium. In this review, we will address the role of stem cells in endometriosis. Recent characterization of stem cell populations within human endometrium has opened the possibility of understanding their physiologic as well as their pathologic roles. While stem cells are critical to the cyclic regeneration of a healthy endometrium, we have shown that both endometrium-derived and bone marrow-derived stem cells can migrate to ectopic sites and contribute to the development of endometriosis. Furthermore, endometriosis interferes with the normal stem cell trafficking to the uterus that is necessary for endometrial growth and repair. Altered stem cell mobility and engraftment characterize this disease.

Avemar and Echinacea extracts enhance mobilization and homing of CD34(+) stem cells in rats with acute myocardial infarction

Introduction

Activation of endogenous stem cell mobilization can contribute to myocardial regeneration after ischemic injury. This study aimed to evaluate the possible role of Avemar or Echinacea extracts in inducing mobilization and homing of CD34⁺ stem cells in relation to the inflammatory and hematopoietic cytokines in rats suffering from acute myocardial infarction (AMI).

Methods

AMI was developed by two consecutive subcutaneous injections of isoprenaline (85 mg/kg). AMI rats were either post-treated or pre- and post-treated daily with oral doses of Avemar (121 mg/kg) or Echinacea (130 mg/kg). In whole blood, the number of CD34⁺ cells was measured by flow cytometry and their homing to the myocardium was immunohistochemically assessed. Serum creatine kinase, vascular endothelial growth factor, interleukin-8 and granulocyte macrophage colony stimulating factor were determined on days 1, 7 and 14 after AMI. Sections of the myocardium were histopathologically assessed.

Results

Rats pre- and post-treated with Avemar or Echinacea exhibited substantial increases in the number of circulating CD34⁺ cells, peaking on the first day after AMI to approximately 13-fold and 15-fold, respectively, with a decline in their level on day 7 followed by a significant increase on day 14 compared to their corresponding AMI levels. Only post-treatment with Echinacea caused a time-dependent increase in circulating CD34⁺ cells on days 7 and 14. Such increases in circulating CD34⁺ cells were accompanied by increased homing to myocardial tissue 14 days after AMI. Interestingly, pre- and post-treatment with Avemar or Echinacea substantially increased serum creatine kinase on day 1, normalized its activity on day 7 and, on continued treatment, only Echinacea markedly increased its activity on day 14 compared to the corresponding AMI values. Moreover, both treatments modified differently the elevated serum vascular endothelial growth factor and the lowered granulocyte macrophage colony stimulating factor levels of the AMI group but did not affect the level of interleukin-8. These results were supported histopathologically by reduced inflammatory reactions and enhanced neovascularization.

Conclusion

Avemar and Echinacea extracts can effectively induce mobilization and homing of CD34⁺ stem cells to the myocardial tissue and thus may help in stem cell-based regeneration of the infarcted myocardium.

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

PURPOSE

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

EXPERIMENTAL DESIGN

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

RESULTS

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

CONCLUSIONS

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

miR-17 promotes expansion and adhesion of human cord blood CD34(+) cells in vitro

Introduction

We have recently found that miR-17 is necessary in the cell-extrinsic control of cord blood (CB) CD34⁺ cell function. Here, we demonstrated that the proper level of miR-17 is also necessary in the cell-intrinsic control of the hematopoietic properties of CB CD34⁺ cells.

Methods

The miR-17 overexpression and knockdown models were created using primary CB CD34⁺ cells transfected by the indicated vectors. Long-term culture, colony forming, adhesion and trans-well migration assays were carried out to investigate the function of miR-17 on CB CD34⁺ cells in vitro. NOD prkdc^scid Il2rg^null mice were used in a SCID repopulating cell assay to investigate the function of miR-17 on CB CD34⁺ cells in vivo. A two-tailed Student’s t-test was used for statistical comparisons.

Results

In vitro assays revealed that ectopic expression of miR-17 promoted long-term expansion, especially in the colony-forming of CB CD34⁺ cells and CD34⁺CD38⁻ cells. Conversely, downregulation of miR-17 inhibited the expansion of CB CD34⁺ cells. However, the overexpression of miR-17 in vivo reduced the hematopoietic reconstitution potential of CB CD34⁺ cells compared to that of control cells. The increased expression of major adhesion molecules in miR-17 overexpressed CB CD34⁺ cells suggests that the adhesion between miR-17 overexpressed CB CD34⁺ cells and their niche in vivo is regulated abnormally, which may further lead to the reduced hematopoietic reconstitution capability of 17/OE cells in engrafted mice.

Conclusion

We conclude that the proper expression of miR-17 is required, at least partly, for normal hematopoietic stem cell–niche interaction and for the regulation of adult hematopoiesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0159-1) contains supplementary material, which is available to authorized users.

Prolyl hydroxylase inhibitors act as agents to enhance the efficiency of cell therapy

INTRODUCTION

In stem cell-based therapy as a subtype of regenerative medicine, stem cells can be used to replace or repair injured tissue and cells in order to treat disease. Stem cells have the ability to integrate into injured areas and produce new cells via processes of proliferation and differentiation. Several studies have demonstrated that hypoxia increases self-renewal, proliferation and post-homing differentiation of stem cells through the regulation of hypoxia-inducible factor-1 (HIF-1)-mediated gene expression. Thus, pharmacological interventions including prolyl hydroxylase (PHD) inhibitors are considered as promising solutions for stem cell-based therapy. PHD inhibitors stabilize the HIF-1 and activate its pathway through preventing proteasomal degradation of HIF-1.

AREAS COVERED

This review focuses on the role of hypoxia, HIF-1 and especially PHD inhibitors on cell therapy. PHD structure and function are discussed as well as their inhibitors. In addition, we have investigated several preclinical studies in which PHD inhibitors improved the efficiency of cell-based therapies.

EXPERT OPINION

The data reviewed here suggest that PHD inhibitors are effective operators in improving stem cell therapy. However, because of some limitations, these compounds should be properly examined before clinical application.

Alpha-Particle-Induced Complex Chromosome Exchanges Transmitted through Extra-Thymic Lymphopoiesis In Vitro Show Evidence of Emerging Genomic Instability

Human exposure to high-linear energy transfer α-particles includes environmental (e.g. radon gas and its decay progeny), medical (e.g. radiopharmaceuticals) and occupational (nuclear industry) sources. The associated health risks of α-particle exposure for lung cancer are well documented however the risk estimates for leukaemia remain uncertain. To further our understanding of α-particle effects in target cells for leukaemogenesis and also to seek general markers of individual exposure to α-particles, this study assessed the transmission of chromosomal damage initially-induced in human haemopoietic stem and progenitor cells after exposure to high-LET α-particles. Cells surviving exposure were differentiated into mature T-cells by extra-thymic T-cell differentiation in vitro. Multiplex fluorescence in situ hybridisation (M-FISH) analysis of naïve T-cell populations showed the occurrence of stable (clonal) complex chromosome aberrations consistent with those that are characteristically induced in spherical cells by the traversal of a single α-particle track. Additionally, complex chromosome exchanges were observed in the progeny of irradiated mature T-cell populations. In addition to this, newly arising de novo chromosome aberrations were detected in cells which possessed clonal markers of α-particle exposure and also in cells which did not show any evidence of previous exposure, suggesting ongoing genomic instability in these populations. Our findings support the usefulness and reliability of employing complex chromosome exchanges as indicators of past or ongoing exposure to high-LET radiation and demonstrate the potential applicability to evaluate health risks associated with α-particle exposure.

An atypical addition to the chemokine receptor nomenclature: IUPHAR Review 15

Chemokines and their receptors are essential regulators of in vivo leukocyte migration and, some years ago, a systematic nomenclature system was developed for the chemokine receptor family. Chemokine receptor biology and biochemistry was recently extensively reviewed. In this review, we also highlighted a new component to the nomenclature system that incorporates receptors previously known as 'scavenging', or 'decoy', chemokine receptors on the basis of their lack of classical signalling responses to ligand binding and their general ability to scavenge, or sequester, their cognate chemokine ligands. These molecules are now collectively referred to as 'atypical chemokine receptors', or ACKRs, and play fundamental roles in regulating in vivo responses to chemokines. This commentary highlights this new addition to the chemokine receptor nomenclature system and provides brief information on the four receptors currently covered by this nomenclature.

The role of novel and known extracellular matrix and adhesion molecules in the homeostatic and regenerative bone marrow microenvironment

Maintenance of haematopoietic stem cells and differentiation of committed progenitors occurs in highly specialized niches. The interactions of haematopoietic stem and progenitor cells (HSPCs) with cells, growth factors and extracellular matrix (ECM) components of the bone marrow (BM) microenvironment control homeostasis of HSPCs. We only start to understand the complexity of the haematopoietic niche(s) that comprises endosteal, arterial, sinusoidal, mesenchymal and neuronal components. These distinct niches produce a broad range of soluble factors and adhesion molecules that modulate HSPC fate during normal hematopoiesis and BM regeneration. Adhesive interactions between HSPCs and the microenvironment will influence their localization and differentiation potential. In this review we highlight the current understanding of the functional role of ECM- and adhesion (regulating) molecules in the haematopoietic niche during homeostatic and regenerative hematopoiesis. This knowledge may lead to the improvement of current cellular therapies and more efficient development of future cellular products.

CXCR4 antagonist AMD3100 redistributes leukocytes from primary immune organs to secondary immune organs, lung, and blood in mice

AMD3100 (plerixafor), is a specific CXCR4 antagonist approved by the FDA for mobilizing hematopoietic stem cells from bone marrow to blood for transplantation in cancer. AMD3100 also mobilizes most mature leukocyte subsets to blood; however, their source and trafficking potential have not been fully delineated. Here, we show that a single injection of AMD3100 10 mg/kg into C57Bl/6 mice rapidly mobilizes (peak ∼ 2.5 h) the same leukocyte subsets to blood as in humans. Using this model, we found that AMD3100 mobilization of neutrophils, lymphocytes, and monocytes to blood is not reduced by splenectomy or by blockade of lymphocyte egress from lymph node with FTY720, but is coupled to (i) reduced content of each of these cell types in the bone marrow; (ii) reduced T-cell numbers in thymuses; (iii) increased lymphocytes in lymph nodes; and (iv) increased neutrophil and monocyte content in the lung. Direct intrathymic labeling showed that AMD3100 selectively mobilizes naïve thymic CD4(+) and CD8(+) T cells to blood. Finally, AMD3100-induced neutrophil mobilization to blood did not reduce neutrophil trafficking to thioglycollate-inflamed peritoneum. Thus, AMD3100 redistributes lymphocytes, monocytes, and neutrophils from primary immune organs to secondary immune organs, peripheral tissues, and blood, without compromising neutrophil trafficking to inflamed sites.

Cutting the brakes on hematopoietic regeneration by blocking TGFβ to limit chemotherapy-induced myelosuppression

Hematopoietic stressors such as infection, bleeding, or toxic injury trigger a hematopoietic adaptation that sacrifices hematopoietic stem and progenitor cell (HSPC) quiescence to meet an urgent need for new blood cell production. Once the hematopoietic demands are adequately met, homeostasis must be restored. Transforming growth factor β (TGFβ) signaling is a central mediator mandating the return of HSPCs to quiescence after stress. Blockade of TGFβ signaling after hematopoietic stress delays the return of cycling HSPCs to quiescence and in so doing promotes hematopoietic stem cell (HSC) self-renewal and accelerates hematopoietic reconstitution. These findings open the door to new therapeutics that modulate the hematopoietic adaptation to stress. In this review, we will discuss the complex context-dependent activities of TGFβ in hematopoiesis and the potential benefits and limitations of using TGFβ pathway inhibitors to promote multilineage hematopoietic reconstitution after myelosuppressive chemotherapy.

Discovery of novel N-aryl piperazine CXCR4 antagonists

A novel series of CXCR4 antagonists with substituted piperazines as benzimidazole replacements is described. These compounds showed micromolar to nanomolar potency in CXCR4-mediated functional and HIV assays, namely inhibition of X4 HIV-1(IIIB) virus in MAGI-CCR5/CXCR4 cells and inhibition of SDF-1 induced calcium release in Chem-1 cells. Preliminary SAR investigations led to the identification of a series of N-aryl piperazines as the most potent compounds. Results show SAR that indicates type and position of the aromatic ring, as well as type of linker and stereochemistry are significant for activity. Profiling of several lead compounds showed that one (49b) reduced susceptibility towards CYP450 and hERG, and the best overall profile when considering both SDF-1 and HIV potencies (6-20 nM).

Identify multiple myeloma stem cells: Utopia?

Multiple myeloma (MM) is a hematologic malignancy of monoclonal plasma cells which remains incurable despite recent advances in therapies. The presence of cancer stem cells (CSCs) has been demonstrated in many solid and hematologic tumors, so the idea of CSCs has been proposed for MM, even if MM CSCs have not been define yet. The existence of myeloma CSCs with clonotypic B and clonotypic non B cells was postulated by many groups. This review aims to focus on these distinct clonotypic subpopulations and on their ability to develop and sustain MM. The bone marrow microenvironment provides to MM CSCs self-renewal, survival and drug resistance thanks to the presence of normal and cancer stem cell niches. The niches and CSCs interact each other through adhesion molecules and the interplay between ligands and receptors activates stemness signaling (Hedgehog, Wnt and Notch pathways). MM CSCs are also supposed to be responsible for drug resistance that happens in three steps from the initial cancer cell homing microenvironment-mediated to development of microenvironment-independent drug resistance. In this review, we will underline all these aspects of MM CSCs.

Matrix metalloproteinases in stem cell mobilization

Hematopoietic stem cells (HSCs) have the capability to migrate back and forth between their preferred microenvironment in bone marrow niches and the peripheral blood, but under steady-state conditions only a marginal number of stem cells can be found in the circulation. Different mobilizing agents, however, which create a highly proteolytic milieu in the bone marrow, can drastically increase the number of circulating HSCs. Among other proteases secreted and membrane-bound matrix metalloproteinases (MMPs) are known to be involved in the induced mobilization process and can digest niche-specific extracellular matrix components and cytokines responsible for stem cell retention to the niches. Iatrogenic stem cell mobilization and stem cell homing to their niches are clinically employed on a routine basis, although the exact mechanisms of both processes are still not fully understood. In this review we provide an overview on the various roles of MMPs in the induced release of HSCs from the bone marrow.

Impaired glucose tolerance alters functional ability of peripheral blood-derived mononuclear cells in Asian Indian men

AIM

To compare the adhesion, migration and endothelial differentiation potential of peripheral blood-derived mononuclear cells (PBMCs) obtained from drug-naive normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) Asian Indian men.

METHODS

Based on the 75-g oral glucose tolerance test, 30 NGT and 31 IGT subjects were recruited into the study. PBMCs were isolated from fasting blood using histopaque density gradient centrifugation. Isolated PBMCs were analysed for their ability to adhere to extracellular matrices, incorporation into tubular structures formed by matured endothelial cells and differentiation into endothelial cells upon 7-day culture in endothelial-specific growth medium.

RESULTS

PBMCs obtained from IGT subjects exhibit poor adherence to fibronectin and reduced incorporation into tubular structures. Migration towards stromal cell-derived factor-1α (SDF-1α) in a trans-well filter assembly was also reduced for these cells. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis revealed decreased expression of CXCR4 and β2 integrin and increased expression of arginase II in IGT subjects. No differences were observed with regard to endothelial differentiation; however, cultured PBMCs of IGT subjects had decreased intracellular nitric oxide (NO) production.

CONCLUSION

In pre-diabetic, Asian Indian men, PBMCs exhibit defective migration and homing potential.

Impact of platelet phenotype on myocardial infarction

In acute myocardial infarction patients the injured vascular wall triggers thrombus formation in the damage site. Fibrin fibers and blood cellular elements are the major components of thrombus formed in acute occlusion of coronary arteries. It has been established that the initial thrombus is primarily composed of activated platelets rapidly stabilized by fibrin fibers. This review highlights the role of platelet membrane phenotype in pathophysiology of myocardial infarction. Here, we regard platelet phenotype as quantitative and qualitative parameters of the plasma membrane outer surface, which are crucial for platelet participation in blood coagulation, development of local inflammation and tissue repair.

C-X-C motif chemokine 12 influences the development of extramedullary hematopoiesis in the spleens of myelofibrosis patients

Myelofibrosis (MF) is characterized by the constitutive mobilization of hematopoietic stem cells (HSC) and hematopoietic progenitor cells (HPC) and the establishment of extramedullary hematopoiesis. The mechanisms underlying this abnormal HSC/HPC trafficking pattern remain poorly understood. We demonstrated that both splenic and peripheral blood (PB) MF CD34(+) cells equally share a defective ability to home to the marrow, but not to the spleens, of NOD/LtSz-Prkdc(scid) mice. This trafficking pattern could not be attributed to discordant expression of integrins or chemokine receptors other than the downregulation of C-X-C chemokine receptor type 4 by both PB and splenic MF CD34(+) cells. The number of both splenic MF CD34(+) cells and HPCs that migrated toward splenic MF plasma was, however, significantly greater than the number that migrated toward PB MF plasma. The concentration of the intact HSC/HPC chemoattractant C-X-C motif chemokine 12 (CXCL12) was greater in splenic MF plasma than PB MF plasma, as quantified using mass spectrometry. Functionally inactive truncated products of CXCL12, which are the product of proteolytic degradation by serine proteases, were detected at similar levels in both splenic and PB MF plasma. Treatment with an anti-CXCL12 neutralizing antibody resulted in a reduction in the degree of migration of splenic MF CD34(+) cells toward both PB and splenic MF plasma, validating the role of CXCL12 as a functional chemoattractant. Our data indicate that the MF splenic microenvironment is characterized by increased levels of intact, functional CXCL12, which contributes to the localization of MF CD34(+) cells to the spleen and the establishment of extramedullary hematopoiesis.

Carbon monoxide down-regulates α4β1 integrin-specific ligand binding and cell adhesion: a possible mechanism for cell mobilization

Background

Carbon monoxide (CO), a byproduct of heme degradation, is attracting growing attention from the scientific community. At physiological concentrations, CO plays a role as a signal messenger that regulates a number of physiological processes. CO releasing molecules are under evaluation in preclinical models for the management of inflammation, sepsis, ischemia/reperfusion injury, and organ transplantation. Because of our discovery that nitric oxide signaling actively down-regulates integrin affinity and cell adhesion, and the similarity between nitric oxide and CO-dependent signaling, we studied the effects of CO on integrin signaling and cell adhesion.

Results

We used a cell permeable CO releasing molecule (CORM-2) to elevate intracellular CO, and a fluorescent Very Late Antigen-4 (VLA-4, α₄β₁-integrin)-specific ligand to evaluate the integrin state in real-time on live cells. We show that the binding of the ligand can be rapidly down-modulated in resting cells and after inside-out activation through several Gα_i-coupled receptors. Moreover, cell treatment with hemin, a natural source of CO, resulted in comparable VLA-4 ligand dissociation. Inhibition of VLA-4 ligand binding by CO had a dramatic effect on cell-cell interaction in a VLA-4/VCAM-1-dependent cell adhesion system.

Conclusions

We conclude that the CO signaling pathway can rapidly down-modulate binding of the VLA-4 -specific ligand. We propose that CO-regulated integrin deactivation provides a basis for modulation of immune cell adhesion as well as rapid cell mobilization, for example as shown for splenic monocytes in response to surgically induced ischemia of the myocardium.

Reactive oxygen species regulate hematopoietic stem cell self-renewal, migration and development, as well as their bone marrow microenvironment

SIGNIFICANCE

Blood forming, hematopoietic stem cells (HSCs) mostly reside in the bone marrow in a quiescent, nonmotile state via adhesion interactions with stromal cells and macrophages. Quiescent, proliferating, and differentiating stem cells have different metabolism, and accordingly different amounts of intracellular reactive oxygen species (ROS). Importantly, ROS is not just a byproduct of metabolism, but also plays a role in stem cell state and function.

RECENT ADVANCES

ROS levels are dynamic and reversibly dictate enhanced cycling and myeloid bias in ROS(high) short-term repopulating stem cells, and ROS(low) quiescent long-term repopulating stem cells. Low levels of ROS, regulated by intrinsic factors such as cell respiration or nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) activity, or extrinsic factors such as stem cell factor or prostaglandin E2 are required for maintaining stem cell self-renewal. High ROS levels, due to stress and inflammation, induce stem cell differentiation and enhanced motility.

CRITICAL ISSUES

Stem cells need to be protected from high ROS levels to avoid stem cell exhaustion, insufficient host immunity, and leukemic transformation that may occur during chronic inflammation. However, continuous low ROS production will lead to lack of stem cell function and opportunistic infections. Ultimately, balanced ROS levels are crucial for maintaining the small stem cell pool and host immunity, both in homeostasis and during stress situations.

FUTURE DIRECTIONS

Deciphering the signaling pathway of ROS in HSC will provide a better understanding of ROS roles in switching HSC from quiescence to activation and vice versa, and will also shed light on the possible roles of ROS in leukemia initiation and development.

Stem cell therapy for cardiovascular disease: the demise of alchemy and rise of pharmacology

Regenerative medicine holds great promise as a way of addressing the limitations of current treatments of ischaemic disease. In preclinical models, transplantation of different types of stem cells or progenitor cells results in improved recovery from ischaemia. Furthermore, experimental studies indicate that cell therapy influences a spectrum of processes, including neovascularization and cardiomyogenesis as well as inflammation, apoptosis and interstitial fibrosis. Thus, distinct strategies might be required for specific regenerative needs. Nonetheless, clinical studies have so far investigated a relatively small number of options, focusing mainly on the use of bone marrow-derived cells. Rapid clinical translation resulted in a number of small clinical trials that do not have sufficient power to address the therapeutic potential of the new approach. Moreover, full exploitation has been hindered so far by the absence of a solid theoretical framework and inadequate development plans. This article reviews the current knowledge on cell therapy and proposes a model theory for interpretation of experimental and clinical outcomes from a pharmacological perspective. Eventually, with an increased association between cell therapy and traditional pharmacotherapy, we will soon need to adopt a unified theory for understanding how the two practices additively interact for a patient's benefit.

CD29 of human umbilical cord mesenchymal stem cells is required for expansion of CD34(+) cells

OBJECTIVES

Human umbilical cord mesenchymal stem cells (hUCMSCs) play a critical role in expanding haematopoietic stem cells (HSCs) by providing the essential microenvironment for haematopoiesis. In this study, we sought to investigate whether CD29 of hUCMSCs would play a key role in the ability of hUCMSCs to help expand HSCs in vivo and in vitro.

MATERIAL AND METHODS

To investigate whether CD29 of hUCMSCs would play a key role for the ability of hUCMSCs to expand HSCs, soluble anti-CD29 antibody was added to co-cultures of hUCMSCs and cord blood (CB) CD34(+) cells. It significantly blocked expansion of CB CD34(+) cells induced by hUCMSCs. Using CD29-deficient hUCMSCs models, long-term culture-initiating cell and non-obese diabetic/severe combined immunodeficient disease mouse repopulating cell assay, revealed that CB CD34(+) cells co-cultured with CD29-deficient hUCMSCs only retained the capacity of multipotent differentiation for 5 weeks at the most.

RESULTS

Soluble anti-CD29 antibody significantly blocked expansion of CB CD34(+) cells induced by hUCMSCs. CB CD34(+) cells co-cultured with CD29-deficient hUCMSCs only retained the capacity of multipotent differentiation for 5 weeks at the most.

CONCLUSIONS

CB CD34(+) cells co-cultured with CD29-deficient hUCMSCs gave rise to all major haematopoietic lineages, but failed to engraft long term.

Inhibitory effects of mesenchymal stem cells in intimal hyperplasia after balloon angioplasty

OBJECTIVE

Intimal hyperplasia is a major cause of restenosis after arterial bypass and balloon angioplasty. Induction of rapid re-endothelialization has been proposed to reduce intimal hyperplasia. The aim of this study was to evaluate the inhibitory effect of mesenchymal stem cells on intimal hyperplasia.

METHODS

Male New Zealand white rabbits were fed 1% cholesterol diets from 1 week before balloon angioplasty to the day of harvest. After dissection of rabbit carotid arteries, balloon angioplasty was performed with a 2F Fogarty embolectomy catheter. The injured carotid artery was coated with a mixture of 7 × 10(6) human umbilical cord mesenchymal stem cells (HUC-MSCs) and fibrin matrix. The carotid arteries were harvested 2, 4, and 8 weeks thereafter, and immunofluorescent staining and quantitative real-time polymerase chain reaction analysis were performed.

RESULTS

The intima/media ratio was significantly reduced in the group treated with HUC-MSCs compared with the nontreated group (Student t-tests, *P < .05). The area of re-endothelialization was significantly higher (Student t-tests, *P < .05) in the group treated with HUC-MSCs than in the nontreated group. Expression of angiogenic genes such as vascular endothelial growth factor, platelet-derived growth factor, kinase insert domain receptor 1, angiopoietin 1, and angio-associated migratory cell protein was increased (analysis of variance, P < .05) in the group treated with HUC-MSCs relative to the nontreated group.

CONCLUSIONS

Our study showed that HUC-MSCs reduce the formation of intimal hyperplasia through rapid re-endothelialization. This result might be applied to development of stem cell-coated stents as well as to development of a stem cell-containing sheet coat for inhibition of intimal hyperplasia after angioplasty or surgery.

Technical advance: ascorbic acid induces development of double-positive T cells from human hematopoietic stem cells in the absence of stromal cells

The efficacy of donor HSCT is partly reduced as a result of slow post-transplantation immune recovery. In particular, T cell regeneration is generally delayed, resulting in high infection-related mortality in the first years post-transplantation. Adoptive transfer of in vitro-generated human T cell progenitors seems a promising approach to accelerate T cell recovery in immunocompromised patients. AA may enhance T cell proliferation and differentiation in a controlled, feeder-free environment containing Notch ligands and defined growth factors. Our experiments show a pivotal role for AA during human in vitro T cell development. The blocking of NOS diminished this effect, indicating a role for the citrulline/NO cycle. AA promotes the transition of proT1 to proT2 cells and of preT to DP T cells. Furthermore, the addition of AA to feeder cocultures resulted in development of DP and SP T cells, whereas without AA, a preT cell-stage arrest occurred. We conclude that neither DLL4-expressing feeder cells nor feeder cell conditioned media are required for generating DP T cells from CB and G-CSF-mobilized HSCs and that generation and proliferation of proT and DP T cells are greatly improved by AA. This technology could potentially be used to generate T cell progenitors for adoptive therapy.

Annexin 2-CXCL12 interactions regulate metastatic cell targeting and growth in the bone marrow

Annexin 2 (ANXA2) plays a critical role in hematopoietic stem cell (HSC) localization to the marrow niche. In part, ANXA2 supports HSCs by serving as an anchor for stromal-derived factor-1 (CXCL12/SDF-1). Recently, it was demonstrated that prostate cancer cells, like HSCs, use ANXA2 to establish metastases in marrow. The present study determined the capacity of ANXA2 expression by bone marrow stromal cells (BMSC) to facilitate tumor recruitment and growth through ANXA2-CXCL12 interactions. Significantly more CXCL12 was expressed by BMSC(Anxa2) (+/+) than by BMSC(Anxa2) (-/-) resulting in more prostate cancer cells migrating and binding to BMSC(Anxa2) (+/+) than BMSC(Anxa2) (-/-), and these activities were reduced when CXCL12 interactions were blocked. To further confirm that BMSC signaling through ANXA2-CXCL12 plays a critical role in tumor growth, immunocompromised SCID mice were subcutaneously implanted with human prostate cancer cells mixed with BMSC(Anxa2) (+/+) or BMSC(Anxa2) (-/-). Significantly larger tumors grew in the mice when the tumors were established with BMSC(Anxa2) (+/+) compared with the tumors established with BMSC(Anxa2) (-/-). In addition, fewer prostate cancer cells underwent apoptosis when cocultured with BMSC(Anxa2) (+/+) compared with BMSC(Anxa2) (-/-), and similar results were obtained in tumors grown in vivo. Finally, significantly more vascular structures were observed in the tumors established with the BMSC(Anxa2) (+/+) compared with the tumors established with BMSC(Anxa2) (-/-). Thus, ANXA2-CXCL12 interactions play a crucial role in the recruitment, growth, and survival of prostate cancer cells in the marrow.

IMPLICATIONS

The tumor microenvironment interaction between ANXA2-CXCL12 is critical for metastatic phenotypes and may impact chemotherapeutic potential.

Biophysical regulation of hematopoietic stem cells

Blood is renewed throughout the entire life. The stem cells of the blood, called hematopoietic stem cells (HSCs), are responsible for maintaining a supply of all types of fresh blood cells. In contrast to other stem cells, the clinical application of these cells is well established and HSC transplantation is an established life-saving therapy for patients suffering from haematological disorders. Despite their efficient functionality throughout life in vivo, controlling HSC behaviour in vitro (including their proliferation and differentiation) is still a major task that has not been resolved with standard cell culture systems. Targeted HSC multiplication in vitro could be beneficial for many patients, because HSC supply is limited. The biology of these cells and their natural microenvironment - their niche - remain a matter of ongoing research. In recent years, evidence has come to light that HSCs are susceptible to physical stimuli. This makes the regulation of HSCs by engineering physical parameters a promising approach for the targeted manipulation of these cells for clinical applications. Nevertheless, the biophysical regulation of these cells is still poorly understood. This review sheds light on the role of biophysical parameters in HSC biology and outlines which knowledge on biophysical regulation identified in other cell types could be applied to HSCs.

Roles of osteoclasts in the control of medullary hematopoietic niches

Bone marrow is the major site of hematopoiesis in mammals. The bone marrow environment plays an essential role in the regulation of hematopoietic stem and progenitor cells by providing specialized niches in which these cells are maintained. Many cell types participate to the composition and regulation of hematopoietic stem cell (HSC) niches, integrating complex signals from the bone, immune and nervous systems. Among these cells, the bone-resorbing osteoclasts (OCLs) have been described as main regulators of HSC niches. They are not limited to carving space for HSCs, but they also provide signals that affect the molecular and cellular niche components. However, their exact role in HSC niches remains unclear because of the variety of models, signals and conditions used to address the question. The present review will discuss the importance of the implication of OCLs focusing on the formation of HSC niches, the maintenance of HSCs in these niches and the mobilization of HSCs from the bone marrow. It will underline the importance of OCLs in HSC niches.

The role of the nervous system in hematopoietic stem cell mobilization

Hematopoietic stem cells (HSCs) and blood cell progenitors, such as maturing leucocytes, steadily enter from bone marrow (BM) into the circulation under steady-state conditions, and their mobilization is dramatically amplified during stress conditions and by mediators such as granulocyte colony-stimulating factor (G-CSF). This mobilization is dependent upon bone remodeling, the proteolytic enzymes of bone marrow-derived stromal cells, and adhesion molecules such as integrin, but the main mechanisms controlling this traffic are still unclear. The nervous system, as the most important regulator of the body, can affect the mobilization network by secreting catecholamines, so that denervation of catecholaminergic fibers in the BM of mice could lead to declining mobilization in steady state and stress situations, even in the presence of other intact environmental factors in the BM. Thus, due to the importance of the nervous system, we have attempted to give a general overview of how the nervous system is involved in the mobilization of HSCs in this review. Then, we will try to describe the mobilization process induced by the nervous system, which consists of 3 mechanisms: stromal cell-derived factor 1 (SDF-1)/CXC chemokine receptor type 4 (CXCR4), proteolytic enzymes, and bone remodeling.

Chemokines as novel and versatile reagents for flow cytometry and cell sorting

Cell therapy regimens are frequently compromised by low-efficiency cell homing to therapeutic niches. Improvements in this regard would enhance effectiveness of clinically applicable cell therapy. The major regulators of tissue-specific cellular migration are chemokines, and therefore selection of therapeutic cellular populations for appropriate chemokine receptor expression would enhance tissue-homing competence. A number of practical considerations preclude the use of Abs in this context, and alternative approaches are required. In this study, we demonstrate that appropriately labeled chemokines are at least as effective in detecting their cognate receptors as commercially available Abs. We also demonstrate the utility of biotinylated chemokines as cell-sorting reagents. Specifically, we demonstrate, in the context of CCR7 (essential for lymph node homing of leukocytes), the ability of biotinylated CCL19 with magnetic bead sorting to enrich for CCR7-expressing cells. The sorted cells demonstrate improved CCR7 responsiveness and lymph node-homing capability, and the sorting is effective for both T cells and dendritic cells. Importantly, the ability of chemokines to detect CCR7, and sort for CCR7 positivity, crosses species being effective on murine and human cells. This novel approach to cell sorting is therefore inexpensive, versatile, and applicable to numerous cell therapy contexts. We propose that this represents a significant technological advance with important therapeutic implications.

Bone marrow vascular niche: home for hematopoietic stem cells

Though discovered later than osteoblastic niche, vascular niche has been regarded as an alternative indispensable niche operating regulation on hematopoietic stem cells (HSCs). As significant progresses gained on this type niche, it is gradually clear that the main work of vascular niche is undertaking to support hematopoiesis. However, compared to what have been defined in the mechanisms through which the osteoblastic niche regulates hematopoiesis, we know less in vascular niche. In this review, based on research data hitherto we will focus on component foundation and various functions of vascular niche that guarantee the normal hematopoiesis process within bone marrow microenvironments. And the possible pathways raised by various research results through which this environment undergoes its function will be discussed as well.

Cell surface engineering to enhance mesenchymal stem cell migration toward an SDF-1 gradient

Mesenchymal stem cell (MSC) therapy for the treatment of myocardial infarction (MI) has shown considerable promise in clinical trials. A billion MSCs need to be administered for therapeutic efficacy, however, because only ∼1% of the cells reach the ischemic myocardium after systemic infusion. This is due to the loss of the homing signal on the surface of the MSCs during their expansion in culture. Stromal-derived factor-1 (SDF-1) is up-regulated immediately after infarction and is released into the peripheral blood. This SDF-1 reaches the bone marrow and recruits CXC chemokine receptor 4 (CXCR4)-positive stem cells. The CXCR4/SDF-1 axis plays an important role in MSC homing to the ischemic myocardium. Since SDF-1 is highly expressed for only 48 h after infarction, the current approaches requiring long-term culture of MSCs to induce CXCR4 expression are not clinically useful. To provide a clinically viable means to improve the homing of MSCs, we have developed a surface modification method to incorporate recombinant CXCR4 protein on the membrane of MSCs within 10 min. Using this method, we have confirmed the improved migration of MSCs toward an SDF-1 gradient.

Looking for the elusive lung stem cell niche

This discourse contains three perspectives on various aspects of Stem Cell Biology and tools available to study and translate into Regenerative Medicine. The lung incessantly faces onslaught of the environment, constantly undergoes oxidative stress, and is an important organ of detoxification. In degenerative diseases and inflammation, the lung undergoes irreversible remodeling that is difficult to therapeutically address and/or transplant a dying tissue. The other difficulty is to study its development and regenerative aspects to best address the aforementioned problems. This perspective therefore addresses- firstly, review of types of stem cells, their pathway of action and models in invertebrate organisms vis-a-vis microenvironment and its dynamics; secondly, stem cells in higher organisms and niche; and lastly data and inference on a novel approach to study stem cell destruction patterns in an injury model and information on putative lung stem cell niche. Stem cells are cryptic cells known to retain certain primitive characteristics making them akin to ancient cells of invertebrates, developmental stages in invertebrates and vertebrates and pliant cells of complex creatures like mammals that demonstrate stimulus-specific behavious, whether to clonally propagate or to remain well protected and hidden within specialized niches, or mobilize and differentiate into mature functionally operative cells to house-keep, repair injury or make new tissues. In lung fibrosis, alveolar epithelium degenerates progressively. In keeping with the goal of regenerative medicine, various models and assays to evaluate long and short term identity of stem cells and their niches is the subject of this perspective. We also report identification and characterization of functional lung stem cells to clarify how stem cell niches counteract this degenerative process. Inferences drawn from this injury model of lung degeneration using a short term assay by tracking side population cells and a long term assay tracking label retaining cells have been presented.