Haemopoietic stem cells

Impact of the putative cancer stem cell markers and growth factor receptor expression on the sensitivity of ovarian cancer cells to treatment with various forms of small molecule tyrosine kinase inhibitors and cytotoxic drugs

Increased expression and activation of human epidermal growth factor receptor (EGFR) and HER-2 have been reported in numerous cancers. The aim of this study was to determine the sensitivity of a large panel of human ovarian cancer cell lines (OCCLs) to treatment with various forms of small molecule tyrosine kinase inhibitors (TKIs) and cytotoxic drugs. The aim was to see if there was any association between the protein expression of various biomarkers including three putative ovarian cancer stem cell (CSC) markers (CD24, CD44, CD117/c-Kit), P-glycoprotein (P-gp), and HER family members and response to treatment with these agents. The sensitivity of 10 ovarian tumour cell lines to the treatment with various forms of HER TKIs (gefitinib, erlotinib, lapatinib, sapitinib, afatinib, canertinib, neratinib), as well as other TKIs (dasatinib, imatinib, NVP-AEW541, crizotinib) and cytotoxic agents (paclitaxel, cisplatin and doxorubicin), as single agents or in combination, was determined by SRB assay. The effect on these agents on the cell cycle distribution, and downstream signaling molecules and tumour migration were determined using flow cytometry, western blotting, and the IncuCyte Clear View cell migration assay respectively. Of the HER inhibitors, the irreversible pan-TKIs (canertinib, neratinib and afatinib) were the most effective TKIs for inhibiting the growth of all ovarian cancer cells, and for blocking the phosphorylation of EGFR, HER-2, AKT and MAPK in SKOV3 cells. Interestingly, while the majority of cancer cells were highly sensitive to treatment with dasatinib, they were relatively resistant to treatment with imatinib (i.e., IC50 >10 µM). Of the cytotoxic agents, paclitaxel was the most effective for inhibiting the growth of OCCLs, and of various combinations of these drugs, only treatment with a combination of NVP-AEW541 and paclitaxel produced a synergistic or additive anti-proliferative effect in all three cell lines examined (i.e., SKOV3, Caov3, ES2). Finally, of the TKIs, only treatment with afatinib, neratinib and dasatinib were able to reduce the migration of HER-2 overexpressing SKOV3 cells. We did not find any significant association between the expression of putative ovarian CSC marker, HER family members, c-MET, ALK, and IGF-IR and the response to the irreversible HER TKIs. Our results support the need for further investigations of the therapeutic potential of these irreversible HER family blockers in ovarian cancer, and the therapeutic potential of dasatinib when used in combination with the inhibitors of the HER family members in ovarian cancer.

Study on the Dynamic Biological Characteristics of Sca-1(+) Hematopoietic Stem and Progenitor Cell Senescence

The researches in the dynamic changes of the progress of HSCs aging are very limited and necessary. In this study, male C57BL/6 mice were divided into 5 groups by age. We found that the superoxide damage of HSPCs started to increase from the middle age (6 months old), with notably reduced antioxidation ability. In accordance with that, the senescence of HSPCs also started from the middle age, since the self-renewal and differentiation ability remarkably decreased, and senescence-associated markers SA-β-GAL increased in the 6-month-old and the older groups. Interestingly, the telomere length and telomerase activity increased to a certain degree in the 6-month-old group. It suggested an intrinsic spontaneous ability of HSPCs against aging. It may provide a theoretical and experimental foundation for better understanding the senescence progress of HSPCs. And the dynamic biological characteristics of HSPCs senescence may also contribute to the clinical optimal time for antiaging drug intervention.

Hematopoietic stem cells: an overview

Considerable efforts have been made in recent years in understanding the mechanisms that govern hematopoietic stem cell (HSC) origin, development, differentiation, self-renewal, aging, trafficking, plasticity and transdifferentiation. Hematopoiesis occurs in sequential waves in distinct anatomical locations during development and these shifts in location are accompanied by changes in the functional status of the stem cells and reflect the changing needs of the developing organism. HSCs make a choice of either self-renewal or committing to differentiation. The balance between self-renewal and differentiation is considered to be critical to the maintenance of stem cell numbers. It is still under debate if HSC can rejuvenate infinitely or if they do not possess ''true" self-renewal and undergo replicative senescence such as any other somatic cell. Gene therapy applications that target HSCs offer a great potential for the treatment of hematologic and immunologic diseases. However, the clinical success has been limited by many factors. This review is intended to summarize the recent advances made in the human HSC field, and will review the hematopoietic stem cell from definition through development to clinical applications.

hERG potassium channel blockage by scorpion toxin BmKKx2 enhances erythroid differentiation of human leukemia cells K562

BACKGROUND

The hERG potassium channel can modulate the proliferation of the chronic myelogenous leukemic K562 cells, and its role in the erythroid differentiation of K562 cells still remains unclear.

PRINCIPAL FINDINGS

The hERG potassium channel blockage by a new 36-residue scorpion toxin BmKKx2, a potent hERG channel blocker with IC50 of 6.7 ± 1.7 nM, enhanced the erythroid differentiation of K562 cells. The mean values of GPA (CD235a) fluorescence intensity in the group of K562 cells pretreated by the toxin for 24 h and followed by cytosine arabinoside (Ara-C) treatment for 72 h were about 2-fold stronger than those of K562 cells induced by Ara-C alone. Such unique role of hERG potassium channel was also supported by the evidence that the effect of the toxin BmKKx2 on cell differentiation was nullified in hERG-deficient cell lines. During the K562 cell differentiation, BmKKx2 could also suppress the expression of hERG channels at both mRNA and protein levels. Besides the function of differentiation enhancement, BmKKx2 was also found to promote the differentiation-dependent apoptosis during the differentiation process of K562 cells. In addition, the blockage of hERG potassium channel by toxin BmKKx2 was able to decrease the intracellular Ca(2+) concentration during the K562 cell differentiation, providing an insight into the mechanism of hERG potassium channel regulating this cellular process.

CONCLUSIONS/SIGNIFICANCE

Our results revealed scorpion toxin BmKKx2 could enhance the erythroid differentiation of leukemic K562 cells via inhibiting hERG potassium channel currents. These findings would not only accelerate the functional research of hERG channel in different leukemic cells, but also present the prospects of natural scorpion toxins as anti-leukemic drugs.

Simultaneous expansion and harvest of hematopoietic stem cells and mesenchymal stem cells derived from umbilical cord blood

The simultaneous expansion and harvest of hematopoietic stem cells and mesenchymal stem cells derived from umbilical cord blood were carried out using bioreactors. The co-culture of umbilical cord blood (UCB)-derived hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) was performed within spinner flasks and a rotating wall vessel (RWV) bioreactor using glass-coated styrene copolymer (GCSC) microcarriers. The medium used was composed of serum-free IMDM containing a cocktail of SCF 15 ng·mL(-1), FL 5 ng·mL(-1), TPO 6 ng·mL(-1), IL-3 15 ng·mL(-1), G-CSF 1 ng·mL(-1) and GM-CSF 5 ng·mL(-1). Accessory stromal cells derived from normal allogeneic adipose tissue were encapsulated in alginate-chitosan (AC) beads and used as feeding cells. The quality of the harvested UCB-HSCs and MSCs was assessed by immunophenotype analysis, methylcellulose colony and multi-lineage differentiation assays. After 12 days of culture, the fold-expansion of total cell numbers, colony-forming units (CFU-C), CD34(+)/CD45(+)/CD105(-) (HSCs) cells and CD34(-)/CD45(-)/CD105(+) (MSCs) cells using the RWV bioreactor were (3.7 ± 0.3)- , (5.1 ± 1.2)- , (5.2 ± 0.4)- , and (13.9 ± 1.2)-fold respectively, significantly better than those obtained using spinner flasks. Moreover, UCB-HSCs and UCB-MSCs could be easily separated by gravity sedimentation after the co-culture period as only UCB-MSCs adhered on to the microcarriers. Simultaneously, we found that the fibroblast-like cells growing on the surface of the GCSC microcarriers could be induced and differentiated towards the osteoblastic, chondrocytic and adipocytic lineages. Phenotypically, these cells were very similarly to the MSCs derived from bone marrow positively expressing the MSCs-related markers CD13, CD44, CD73 and CD105, while negatively expressing the HSCs-related markers CD34, CD45 and HLA-DR. It was thus demonstrated that the simultaneous expansion and harvest of UCB-HSCs and UCB-MSCs is possible to be accomplished using a feasible bioreactor culture system such as the RWV bioreactor with the support of GCSC microcarriers.

MicroRNA-223 reversibly regulates erythroid and megakaryocytic differentiation of K562 cells

MicroRNAs (miRNAs) are thought to modulate a variety of cellular events. Several studies have revealed the functions of miR-223 in granulopoiesis. Here we analysed miR-223 expression in various human tissues, blood and leukaemia cells, and focused on its role in K562 erythroid and megakaryocytic differentiation. MiR-223 was detected not only in granulocytes but also in erythroid cells. In K562 cells, expression of miR-223 was down-regulated during haemin-induced erythroid differentiation but up-regulated during phorbol myristate acetate (PMA)-induced megakaryocytic differentiation. The overexpression of miR-223 resulted in significant decrease of γ-globin mRNA and the fraction of benzidine-positive cells in K562 cells, suggesting a suppressive effect of miR-223 on erythroid differentiation. Peaks corresponding to 4N cells in stable transfectants overexpressing miR-223 were higher than that in control K562 cells during megakaryocytic differentiation, indicating that miR-223 increases megakaryocytic differentiation. The expression of LIM domain only 2 (LMO2) reporter was suppressed in NIH-3T3 when the expression of miR-223 was enforced by both the luciferase and fluorescence system. Furthermore, LMO2 mRNA and protein levels were significantly decreased in stable K562 transfectants overexpressing miR-223. These results indicate that LMO2 is a direct target of miR-223. Thus, our results suggest that miR-223 reversibly regulates erythroid and megakaryocytic differentiation of K562 cells via down-modulation of LMO2.

Stem cells for epidermal melanocytes--a challenge for students of dermatopathology

Many obstacles to belief in stem cells for melanocytes arise in the routine practice of cutaneous histopathology. However, the fundamental principle of stem cell theory says that normal stem cells arise during development, are present in adult organs as tissue-determined stem cells, and are little changed, if at all, from their embryonic counterparts. This paradox can be resolved by focusing on the process of epidermal melanocyte development in utero. Stem cells for melanocytes originate in the neural crest. Although much remains to be learned, this author proposes that these stem cells then take a small step to the paraspinal ganglia and then follow the axonal signposts to the skin provided in the course of normal cutaneous innervation. The epidermis may then induce these stem cells in the nerve sheath to give rise to immature dermal melanocytes, which migrate up into the epidermis. It is proposed that these melanocyte stem cells also persist after birth in the superficial nerve sheath and give rise to transient, immature, inconspicuous dermal migratory melanocytes when replacements for epidermal melanocytes are needed in postnatal skin.

Gene therapy in large animal models of muscular dystrophy

The muscular dystrophies are a group of genetically and phenotypically heterogeneously inherited diseases characterized by progressive muscle wasting, which can lead to premature death in severe forms such as Duchenne muscular dystrophy (DMD). In many cases they are caused by the absence of proteins that are critical components of the dystrophin-glycoprotein complex, which links the cytoskeleton and the basal lamina. There is no effective treatment for these disorders at present, but several novel strategies for replacing or repairing the defective gene are in development, with early encouraging results from animal models. We review these strategies, which include the use of stem cells of different tissue origins, gene replacement therapies mediated by various viral vectors, and transcript repair treatments using exon skipping strategies. We comment on their advantages and on limitations that must be overcome before successful application to human patients. Our focus is on studies in a clinically relevant large canine model of DMD. Recent advances in the field suggest that effective therapies for muscular dystrophies are on the horizon. Because of the complex nature of these diseases, it may be necessary to combine multiple approaches to achieve a successful treatment.

Effects of encapsulated rabbit mesenchymal stem cells on ex vivo expansion of human umbilical cord blood hematopoietic stem/progenitor cells

The expansion of umbilical cord blood mononuclear cells (UCB MNCs) was investigated in a novel co-culture system by means of encapsulation of rabbit bone marrow (BM) mesenchymal stem cells (MSCs) in alginate beads (Alg beads). Three kinds of media were applied and the experiments lasted for 7 days. The total nucleated cell density was measured every 24 h. Flow cytometric assay for CD34(+) cells and methylcellulose colony assays were carried out at 0, 72 and 168 h. It was found that the encapsulated MSCs illustrated remarkable effects on UCB MNCs expansion regardless of whether serum is present in culture media or not. At the end of 168 h co-culture, the total nucleated cell number was multiplied by 15 +/- 2.9 times, and CD34(+) cells 5.3 +/- 0.3 times and colony-forming units in culture (CFU-Cs) 5.6 +/- 1.2 times in the serum-free media supplemented with conventional dose of cytokines, which was very similar to the results in the containing 20% serum media. While in the control, i.e. MNC expansion without encapsulated MSCs, however, total nucleated cells density changed mildly, CD34(+) cells and CFU-Cs showed little effective expansion. It is demonstrated that the encapsulated stromal cells can support the expansion of UCB MNCs effectively under the experimental condition.

The vitamin D3/Hox-A10 pathway supports MafB function during the monocyte differentiation of human CD34+ hemopoietic progenitors

Although a considerable number of reports indicate an involvement of the Hox-A10 gene in the molecular control of hemopoiesis, the conclusions of such studies are quite controversial given that they support, in some cases, a role in the stimulation of stem cell self-renewal and myeloid progenitor expansion, whereas in others they implicate this transcription factor in the induction of monocyte-macrophage differentiation. To clarify this issue, we analyzed the biological effects and the transcriptome changes determined in human primary CD34(+) hemopoietic progenitors by retroviral transduction of a full-length Hox-A10 cDNA. The results obtained clearly indicated that this homeogene is an inducer of monocyte differentiation, at least partly acting through the up-regulation of the MafB gene, recently identified as the master regulator of such a maturation pathway. By using a combined approach based on computational analysis, EMSA experiments, and luciferase assays, we were able to demonstrate the presence of a Hox-A10-binding site in the promoter region of the MafB gene, which suggested the likely molecular mechanism underlying the observed effect. Stimulation of the same cells with the vitamin D(3) monocyte differentiation inducer resulted in a clear increase of Hox-A10 and MafB transcripts, indicating the existence of a precise transactivation cascade involving vitamin D(3) receptor, Hox-A10, and MafB transcription factors. Altogether, these data allow one to conclude that the vitamin D(3)/Hox-A10 pathway supports MafB function during the induction of monocyte differentiation.

A two-stage perfusion fibrous bed bioreactor system for mass production of embryonic stem cells

BACKGROUND

Embryonic stem cells (ESCs) have unlimited proliferation potential and can differentiate into all cell and tissue types, and thus are ideal sources for cell therapy and drug screening. Current supplies of ESCs are limited by the available cell sources and inefficient culture methods that grow ESCs on surfaces coated with expensive extracellular matrix (ECM) proteins and in media containing expensive growth factors.

OBJECTIVE

To meet the demand for ESCs, it is necessary to develop an economical process for their mass production.

METHODS

We review the latest development in in vitro ESC culture and introduce a two-stage perfusion bioreactor system that uses 3-D fibrous matrices and conditioned media for production of ESCs.

RESULTS/CONCLUSION

The two-stage process can produce billions of ESCs in a small bioreactor without using ECM proteins and growth factors, and is promising for further scale-up for clinical applications.

Stem cells for cardiovascular repair - the challenges of the aging heart

The discovery of extracardiac progenitor cells and resident cardiac stem cells in recent years has led to a great deal of interest in the development of therapeutic strategies that target these endogenous cell sources for promotion of cardiovascular repair mechanisms in the diseased heart. Cardiovascular risk increases with age and among many factors, the age-associated decline in cardiac and vascular regenerative capacity may contribute to the progressive deterioration of cardiovascular health. Thus, understanding the mechanisms which underlie the dysregulation of cardiac stem and progenitor cells may lead to the identification of novel targets and approaches to reverse this decline. In this review, we outline the current knowledge about cardiac stem and progenitor cells, their contribution to cardiovascular regenerative processes and factors that may affect their decreased function in aging individuals. Moreover, we describe the therapeutic strategies that are currently being tested in clinical trials as well as potential new avenues of investigation for the future.

The role of DNA damage repair in aging of adult stem cells

DNA repair maintains genomic stability and the loss of DNA repair capacity results in genetic instability that may lead to a decline of cellular function. Adult stem cells are extremely important in the long-term maintenance of tissues throughout life. They regenerate and renew tissues in response to damage and replace senescent terminally differentiated cells that no longer function. Oxidative stress, toxic byproducts, reduced mitochondrial function and external exposures all damage DNA through base modification or mis-incorporation and result in DNA damage. As in most cells, this damage may limit the survival of the stem cell population affecting tissue regeneration and even longevity. This review examines the hypothesis that an age-related loss of DNA damage repair pathways poses a significant threat to stem cell survival and longevity. Normal stem cells appear to have strict control of gene expression and DNA replication whereas stem cells with loss of DNA repair may have altered patterns of proliferation, quiescence and differentiation. Furthermore, stem cells with loss of DNA repair may be susceptible to malignant transformation either directly or through the emergence of cancer-prone stem cells. Human diseases and animal models of loss of DNA repair provide longitudinal analysis of DNA repair processes in stem cell populations and may provide links to the physiology of aging.

Neural Network Analysis of Ex-vivo Expansion of Hematopoietic Stem Cells

The shortage of hematopoietic stem cells (HSCs) greatly limits their widespread clinical applications. Few studies however, investigated the relationship between the cellular expansion and the influencing factors although wide variety results of the ex-vivo expansion of HSCs existed in literature. Here, a back-propagation (BP) neural network model was employed to evaluate the ex-vivo expansions of nuclear cells (NCs), CD34(+) cells, and colony-forming units (CFU-Cs), where the output was the cellular expansion folds and the inputs include inoculated density, cytokines, resources, serum, stroma, culture time, and bioreactor types. Around 124, 86, and 90 samples were used to train the neural network for the expansion evaluations of NCs, CD34(+ )cells, and CFU-Cs, respectively, while 17, 14, and 10 samples were applied to predict respectively. The results show that for the training of network, the interval accuracy of the expansion folds for the different cells is 85.5, 86.1, and 86.7%, respectively, while the truth-value accuracy is still up to 59.7, 50.0, and 62.2%, respectively within a relative error (RE) of +/-20%. For the prediction of network, the interval accuracy can be up to 82.4, 71.4, and 70%, respectively, while the truth-value accuracy is only 29.4, 14.3, and 50.0%, respectively (RE = +/-20%). Moreover, six verification experiments were carried out based on our interval predicted values and the results proved that the five group predicted conditions lead to the correct expansion of the HSCs with the accuracy more than 80%. Considering the complexity of HSC expansion and complicated wide range of the experimental data, such relatively high interval accuracy for training and prediction as well as verification are satisfied. Therefore this nonlinear modeling makes it possible to describe quantitatively the effects of the culture conditions on the HSC expansion and to predict the optimal culture conditions for higher ex-vivo expansion of HSCs.

Growth factor independence-1 (Gfi-1) plays a role in mediating specific granule deficiency (SGD) in a patient lacking a gene-inactivating mutation in the C/EBPepsilon gene

Neutrophil-specific granule deficiency (SGD) is a rare congenital disorder marked by recurrent bacterial infections. Neutrophils from SGD patients lack secondary and tertiary granules and their content proteins and lack normal neutrophil functions. Gene-inactivating mutations in the C/EBPepsilon gene have been identified in 2 SGD patients. Our studies on a third SGD patient revealed a heterozygous mutation in the C/EBPepsilon gene. However, we demonstrate elevated levels of C/EBPepsilon and PU.1 proteins in the patient's peripheral blood neutrophils. The expression of the transcription factor growth factor independence-1 (Gfi-1), however, was found to be markedly reduced in our SGD patient despite the absence of an obvious mutation in this gene. This may explain the elevated levels of both C/EBPepsilon and PU.1, which are targets of Gfi-1 transcriptional repression. We have generated a growth factor-dependent EML cell line from the bone marrow of Gfi-1(+/-) and Gfi-1(+/+) mice as a model for Gfi-1-deficient SGD, and demonstrate that lower levels of Gfi-1 expression in the Gfi-1(+/-) EML cells is associated with reduced levels of secondary granule protein (SGP) gene expression. Furthermore, we demonstrate a positive role for Gfi-1 in SGP expression, in that Gfi-1 binds to and up-regulates the promoter of neutrophil collagenase (an SGP gene), in cooperation with wild-type but not with mutant C/EBPepsilon. We hypothesize that decreased Gfi-1 levels in our SGD patient, together with the mutant C/EBPepsilon, block SGP expression, thereby contributing to the underlying etiology of the disease in our patient.

The molecular basis of ageing in stem cells

Ageing is often defined in the context of telomerase activity and telomere length regulation. Most somatic cells have limited replication ability and undergo senescence eventually. Stem cells are unique as they possess more abundant telomerase activity and are able to maintain telomere lengths for a longer period. Embryonic stem cells are particularly resistant to ageing and can be propagated indefinitely. Remarkably, adult somatic cells can be reprogrammed to an ESC-like state by various means including cell fusion, exposure to ESC cell-free extracts, enforced expression of specific molecules, and somatic cell nuclear transfer. Thus, the rejuvenation of an 'aged' state can be effected by the activation of specific key molecules in the cell. Here, we argue that cellular ageing is a reversible process, and this is determined by the balance of biological molecules which directly or indirectly control telomere length and telomerase activity, either through altering gene expression and/or modulating the epigenetic state of the chromatin.

Tfe3 expression is closely associated to macrophage terminal differentiation of human hematopoietic myeloid precursors

The MItf-Tfe family of basic helix-loop-helix leucine zipper (bHLH-Zip) transcription factors encodes four family members: MItf, Tfe3, TfeB and TfeC. In vitro, each protein of the family binds DNA in a homo- or heterodimeric form with other family members. Tfe3 is involved in chromosomal translocations recurrent in different tumors and it has been demonstrated, by in vivo studies, that it plays, redundantly with MItf, an important role in the process of osteoclast formation, in particular during the transition from mono-nucleated to multi-nucleated osteoclasts. Since mono-nucleated osteoclasts derive from macrophages we investigated whether Tfe3 might play a role upstream during hematopoietic differentiation. Here we show that Tfe3 is able to induce mono-macrophagic differentiation of U937 cells, in association with a decrease of cell proliferation and an increase of apoptosis. We also show that Tfe3 does not act physiologically during commitment of CD34+ hematopoietic stem cells (HSCs), since it is not able to direct HSCs toward a specific lineage as observed by clonogenic assay, but is a strong actor of terminal differentiation since it allows human primary myeloblasts' maturation toward the macrophage lineage.

Ex vivo expansion of hematopoietic stem cells derived from umbilical cord blood in rotating wall vessel

Expansion of umbilical cord blood mononuclear cells (UCB MNCs) was carried out in a rotating wall vessel (RWV) bioreactor and tissue culture flasks (T-flasks) in serum-containing medium supplemented with relatively low doses of purified recombinant human cytokines (5.33 ng/ml IL-3, 16 ng/ml SCF, 3.33 ng/ml G-CSF, 2.13 ng/ml GM-CSF, 7.47 ng/ml FL and 7.47 ng/ml TPO) for 8 days. The cell density, pH and osmolality of the culture medium in the two culture systems were measured every 24h. Flow cytometric assay for CD34+ cells was carried out at 0, 144 and 197 h and methylcellulose colony assays were performed at 0, 72, 144 and 197 h. The pH and osmolality of the medium in the two culture systems were maintained in the proper ranges for hematopoietic stem cells (HSCs) and progenitors culture. The RWV bioreactor, combined with a cell-dilution feeding protocol, was efficient to expand UCB MNCs. At the end of 200 h culture, the total cell number was multiplied by 435.5+/-87.6 times, and CD34+ cells 32.7+/-15.6 times, and colony-forming units of granulocyte-macrophage (CFU-GM) 21.7+/-4.9 times. While in T-flasks, however, total cells density changed mildly, CD34+ cells and CFU-GM decreased in number. It is demonstrated that the RWV bioreactor can provide a better environment for UCB MNCs expansion, enhance the contact between HSCs and accessory cells and make the utilization of cytokines more effective than T-flask.

Stem cells: classifications, controversies, and clinical applications

The application of stem cells in regenerative and reparative therapies is emerging in surgery. Published information can lead to an over simplified view of stem cells with respect to their definitions, tissues of origin, abilities to differentiate into tissue lineages, and their capacity for functional tissue regeneration. The goals of this review article are to define embryonic and adult stem cells, compare differences between them, and summarize their potential clinical applications.

The anti-proliferative effect of neurokinin-A on hematopoietic progenitor cells is partly mediated by p53 activating the 5' flanking region of neurokinin-2 receptor

The bone marrow (BM) is home to at least two stem cells, hematopoietic (HSC) and mesenchymal. Hematopoiesis is partly regulated through neurokinin-1 (NK-1) and NK-2 belonging to the family of G-protein/7-transmembrane receptors. NK-1 and NK-2 show preference for the neurotransmitters, substance P (SP) and neurokinin-A (NK-A), respectively. Hematopoietic suppression mediated by NK-A could be partly explained through the production of TGF-beta1 and MIP-1alpha. This study further characterizes mechanisms by which NK-A inhibits progenitor cell proliferation. The study addresses the hypothesis that p53 is a mediator of NK-A activation and this occurs partly through p53-mediated expression of NK-2. The studies first analyzed two consensus sequences for p53 in supershift assays. Reporter gene assays with NK-2 gene constructs and p53 expressing wild-type and mutant vectors, combined with cell proliferation assays, show NK-A activating p53 to inhibit the proliferation of K562 progenitors. These effects were reversed by hematopoietic stimulators, GM-CSF and SP. Verification studies with human CD34+/CD38- and CD34+/CD38+ BM progenitors show similar mechanisms with the expression of p21. This study reports on p53 as central to NK-A-NK-2 interaction in cell cycle quiescence of hematopoietic progenitors. These effects are reversed by at least two hematopoietic stimulators, SP and GM-CSF, with concomitant downregulation of p53.

Adult neural stem cells from the mouse subventricular zone are limited in migratory ability compared to progenitor cells of similar origin

The subventricular zone (SVZ) in the forebrain is the largest source of neural stem cells and progenitor cells in the adult CNS. To assess the ability of adult neural stem cells to survive, differentiate and migrate, we have compared the behavior of dissociated, neurosphere-derived stem cells with that of progenitor cells in transplantation experiments. This ability was first tested in vivo, offering the stem cells the possibility to migrate along the rostral migratory stream (RMS), their specific pathway. In addition, the differential behaviors of the two classes of cells were also compared in vitro by grafting them into organotypic slice cultures containing either tangential (embryonic cerebral cortex) or radial (early postnatal cerebellar cortex) migratory routes. Most of the grafted adult neurosphere-derived stem cells survived and integrated in vivo, and a proportion of them differentiate into neurons, oligodendrocytes or astrocytes. However, they were unable to migrate along the RMS and remained in the vicinity of the injection site. In contrast, SVZ progenitor cells were able to migrate toward the olfactory bulb and, once there, to acquire the phenotype of granule cells, as previously reported. In vitro, neural stem cells exhibited a better migratory ability, although they only migrated for short distances, particularly, in forebrain slices. Nevertheless, the average distance covered by progenitor cells was a two-fold longer than that covered by neural stem cells, corroborating that this class of more specified cells has higher migratory ability. These results suggest that the in vitro conditions of expanding SVZ-derived stem cells, required to maintain them in an immature stage might modify their intrinsic properties, preventing their differentiation into neuroblasts and their subsequent migration.