Effects of exposure to gradient magnetic fields emitted by nuclear magnetic resonance devices on clonogenic potential and proliferation of human hematopoietic stem cells.

This study investigates effects of gradient magnetic fields (GMFs) emitted by magnetic resonance imaging (MRI) devices on hematopoietic stem cells. Field measurements were performed to assess exposure to GMFs of staff working at 1.5 T and 3 T MRI units. Then an exposure system reproducing measured signals was realized to expose in vitro CD34+ cells to GMFs (1.5 T-protocol and 3 T-protocol). CD34+ cells were obtained by Fluorescence Activated Cell Sorting from six blood donors and three MRI-exposed workers. Blood donor CD34+ cells were exposed in vitro for 72 h to 1.5 T or 3 T-protocol and to sham procedure. Cells were then cultured and evaluated in colony forming unit (CFU)-assay up to 4 weeks after exposure. Results showed that in vitro GMF exposure did not affect cell proliferation but instead induced expansion of erythroid and monocytes progenitors soon after exposure and for the subsequent 3 weeks. No decrease of other clonogenic cell output (i.e., CFU-granulocyte/erythroid/macrophage/megakaryocyte and CFU-granulocyte/macrophage) was noticed, nor exposed CD34+ cells underwent the premature exhaustion of their clonogenic potential compared to sham-exposed controls. On the other hand, pilot experiments showed that CD34+ cells exposed in vivo to GMFs (i.e., samples from MRI workers) behaved in culture similarly to sham-exposed CD34+ cells, suggesting that other cells and/or microenvironment factors might prevent GMF effects on hematopoietic stem cells in vivo. Accordingly, GMFs did not affect the clonogenic potential of umbilical cord blood CD34+ cells exposed in vitro together with the whole mononuclear cell fraction.

In vitro cardiomyocyte differentiation of umbilical cord blood cells: crucial role for c-kit(+) cells.

BACKGROUND AIMS: Although bone marrow c-kit(+) progenitor cells support myocardial regeneration, the cardiomyocyte differentiation potential of umbilical cord blood (UCB) c-kit(+) cells is unknown. METHODS: UCB mononuclear cells (MNCs) and c-kit(+) cells purified by use of immunomagnetic beads were used. Cardiomyocyte differentiation was induced with (i) α-minimum essential medium (MEM) with cyclosporine A, (ii) α-MEM with bone morphogenic protein 4 (BMP-4) and transforming growth factor-ß (TGF-ß) or (iii) MEM with dexamethasone. The expression of cardiac markers (GATA4, GATA6, ß-myosin heavy chain, α-sarcomeric actin and cardiac Troponin T) was investigated, and whole-cell current and voltage-clamp recordings were performed. RESULTS: Although c-kit(+) cells revealed an immature gene profile, with high expression of CD34, CD133, aldehyde dehydrogenase-A1 and c-myc RNAs, purified c-kit(+) cells did not succeed in differentiating into cardiomyocyte-like cells in culture. In contrast, MNCs (either in α-MEM plus cyclosporine A or in α-MEM plus BMP-4 and TGF-ß) produced large, adherent cells expressing several cardiac genes and exhibiting an excitable phenotype. Cardiomyocyte-like cell formation was prevented by removing the c-kit(+) cell fraction from MNCs. Furthermore, after co-culturing carboxyfluorescein diacetate succynimidyl ester (CFSE)-tracked c-kit(+) cells together with c-kit(-) cells, we found that cardiac Troponin T--expressing cells were also CFSE(+). CONCLUSIONS: We show that UCB contains progenitors endowed with differentiation potential into cardiomyocytes: these cells reside in the c-kit(+) fraction and require the presence of abundant accessory cells to accomplish the differentiation. These preliminary observations provide the basis for consider the storage of autologous UCB in patients with prenatal diagnosis of congenital heart diseases potentially amenable by myocardial regenerative approaches.

Endothelial progenitor cells are clonal and exhibit the JAK2(V617F) mutation in a subset of thrombotic patients with Ph-negative myeloproliferative neoplasms.

In this study we investigated whether neoplastic transformation occurring in Philadelphia (Ph)-negative myeloproliferative neoplasms (MPNs) could involve also the endothelial cell compartment. We evaluated the level of endothelial colony-forming cells (E-CFCs) in 42 patients (15 with polycythemia vera, 12 with essential thrombocythemia, and 15 with primary myelofibrosis). All patients had 1 molecular abnormality (JAK2(V617F) or MPL(W515K) mutations, SOCS gene hypermethylation, clonal pattern of growth) detectable in their granulocytes. The growth of colonies was obtained in 22 patients and, among them, patients with primary myelofibrosis exhibited the highest level of E-CFCs. We found that E-CFCs exhibited no molecular abnormalities in12 patients, had SOCS gene hypermethylation, were polyclonal at human androgen receptor analysis in 5 patients, and resulted in JAK2(V617F) mutated and clonal in 5 additional patients, all experiencing thrombotic complications. On the whole, patients with altered E-CFCs required antiproliferative therapy more frequently than patients with normal E-CFCs. Moreover JAK2(V617F)-positive E-CFCs showed signal transducer and activator of transcription 5 and 3 phosphorylation rates higher than E-CFCs isolated from healthy persons and patients with MPN without molecular abnormalities. Finally, JAK2(V617F)-positive E-CFCs exhibited a high proficiency to adhere to normal mononuclear cells. This study highlights a novel mechanism underlying the thrombophilia observed in MPN.

Cyclooxygenase-2 (COX-2) inhibition constrains indoleamine 2,3-dioxygenase 1 (IDO1) activity in acute myeloid leukaemia cells.

Indoleamine 2,3-dioxygenase 1 (IDO1) metabolizes L-tryptophan to kynurenines (KYN), inducing T-cell suppression either directly or by altering antigen-presenting-cell function. Cyclooxygenase (COX)-2, the rate-limiting enzyme in the synthesis of prostaglandins, is over-expressed by several tumours. We aimed at determining whether COX-2 inhibitors down-regulate the IFN-g-induced expression of IDO1 in acute myeloid leukaemia (AML) cells. IFN-γ at 100 ng/mL up-regulated COX-2 and IDO1 in HL-60 AML cells, both at mRNA and protein level. The increased COX-2 and IDO1 expression correlated with heightened production of prostaglandin (PG)E2 and kynurenines, respectively. Nimesulide, a preferential COX-2 inhibitor, down-regulated IDO1 mRNA/protein and attenuated kynurenine synthesis, suggesting that overall IDO inhibition resulted both from reduced IDO1 gene transcription and from inhibited IDO1 catalytic activity. From a functional standpoint, IFN-g-challenged HL-60 cells promoted the in vitro conversion of allogeneic CD4⁺CD25⁻ T cells into bona fide CD4⁺CD25⁺FoxP3⁺ regulatory T cells, an effect that was significantly reduced by treatment of IFN-γ-activated HL-60 cells with nimesulide. Overall, these data point to COX-2 inhibition as a potential strategy to be pursued with the aim at circumventing leukaemia-induced, IDO-mediated immune dysfunction.

Cord Blood Platelet Lysate: In Vitro Evaluation to Support the Use in Regenerative Medicine.

Platelet-rich plasma (PRP) is an inexpensive and safe substitute of recombinant growth factors in vitro and in vivo. Due to its putative effect on tissue repair, the use of autologous PRP has become largely popular. Recently, a jellified PRP derivative obtained from umbilical cord blood (CB) has been utilized in vivo to treat mucosal and cutaneous lesions. Nevertheless, whether PRP derived from CB and adult blood display different potency in promoting cell growth in vitro has been rarely investigated. In this study, we compared cytokine profile and mesenchymal cell growth supporting the ability of platelet lysate obtained from adult and cord blood. Our in vitro results strongly back the utilization of CB platelet lysate in vivo, as an efficacious, safe and inexpensive alternative to promote damaged tissue healing when the autologous PRP is contraindicated. Moreover, the policy of manufacturing CB platelet lysate can limit the current disposal of many collected CB units not suitable for transplant due to their low nucleated cell count.

Myoendothelial differentiation of human umbilical cord blood-derived stem cells in ischemic limb tissues.

Human umbilical cord blood (UCB) contains high numbers of endothelial progenitors cells (EPCs) characterized by coexpression of CD34 and CD133 markers. Prior studies have shown that CD34+/CD133+ EPCs from the cord or peripheral blood (PB) can give rise to endothelial cells and induce angiogenesis in ischemic tissues. In the present study, it is shown that freshly isolated human cord blood CD34+ cells injected into ischemic adductor muscles gave rise to endothelial and, unexpectedly, to skeletal muscle cells in mice. In fact, the treated limbs exhibited enhanced arteriole length density and regenerating muscle fiber density. Under similar experimental conditions, CD34- cells did not enhance the formation of new arterioles and regenerating muscle fibers. In nonischemic limbs CD34+ cells increased arteriole length density but did not promote formation of new muscle fibers. Endothelial and myogenic differentiation ability was maintained in CD34+ cells after ex vivo expansion. Myogenic conversion of human cord blood CD34+ cells was also observed in vitro by coculture onto mouse myoblasts. These results show that human cord blood CD34+ cells differentiate into endothelial and skeletal muscle cells, thus providing an indication of human EPCs plasticity. The full text of this article is available online at http://www.circresaha.org.

Electrophysiological properties of mouse bone marrow c-kit+ cells co-cultured onto neonatal cardiac myocytes.

OBJECTIVE: Controversy about hematopoietic stem cells reprogramming into cardiac myocytes is currently supported by positive and negative findings. In fact, some reports have shown the ability of stem cells from the bone marrow (BM) to differentiate into cardiac myocytes and to contribute to myocardium repair, while others have reported the opposite. METHODS: C-kit(+) cells from mouse bone marrow were co-cultured onto neonatal cardiac myocytes. Hematopoietic stem cell-derived cells were analyzed by investigating the expression of cardiac markers and ion channels and by single-cell electrophysiological recordings. RESULTS: Groups of undifferentiated c-kit(+) cells displayed only outward currents. Co-cultured c-kit(+) stem cells on neonatal cardiac myocytes expressed cardiac markers and Na(+) and Ca(2+) voltage-gated ion channels. However, Na(+) and Ca(2+) currents were not detected by electrophysiological patch-clamp recordings even if caffeine and cyclopiazonic acid treatment showed the presence of intracellular calcium stores. This suggests that these channels, although expressed, were not functional and thus do not allow the coupling between excitation and contraction that is typical of cardiac myocytes. Nevertheless, co-cultured cells had a more hyperpolarized resting membrane potential and, at least in a subset of cells, displayed voltage-gated inward rectifier currents and outward currents. Co-cultured c-kit(+)-derived cells were not connected to surrounding cardiac myocytes through gap junctions. To induce a more pronounced differentiation, co-cultured cells were treated with BMP-4 and TGF-beta, two factors that were shown to trigger a cardiac myocyte differentiation pathway in embryonic stem (ES) cells. Even under these conditions, c-kit(+) cells did not differentiate into functionally active cardiac myocytes. However, TGF-beta/BMP-4-treated cells were hyperpolarized and showed and increased inward rectifier current density. CONCLUSIONS: Our study shows that mouse BM hematopoietic stem cells exhibit a limited plasticity to transdifferentiate into cardiac myocytes in culture.

Human cord blood endothelial progenitors promote post-ischemic angiogenesis in immunocompetent mouse model.

BACKGROUND: Human cord blood (CB) endothelial colony forming cells (ECFCs) are endowed with high vascular regenerative ability in immunodeficient mice, but their immunogenicity and susceptibility to rejection in immunocompetent models has yet to be explored. METHODS: We injected CB ECFCs in non-immuno-suppressed C57BL/6J mice after having induced the hindlimb ischemia and we investigated their contribution to the recovery from the ischemic injury. Human ECFCs (hECFCs) were administered by intramuscular injection and hindlimb blood perfusion was measured by laser Doppler analysis at 7-day intervals for 28days after treatment. Mice were sacrificed after 7 and 28days and immunohistochemistry for specific human (CD31) and mouse (von Willebrand factor) endothelial antigens was carried out. Before euthanasia, blood samples to assess cytokines and angiogenic growth factor levels were collected. RESULTS: Mice injected with hECFCs showed a prompter and greater recovery of blood flow than controls. Several endothelial cells of human origin were detected at day7 after injection and their number declined progressively. Likewise, a progressive increase of mouse-derived vascular structures were observed, paralleled by the amplified endogenous production of various soluble mediators of angiogenesis, including Vascular Endothelial Growth Factor and Fibroblast Growth Factor. CONCLUSIONS: Overall, our findings are consistent with the hypothesis that human ECFCs might expand the endogenous vascular repair potential of recipients and support their possible HLA-independent unconventional use.

Endothelial progenitor cell dysfunction in myelodysplastic syndromes: possible contribution of a defective vascular niche to myelodysplasia.

We set a model to replicate the vascular bone marrow niche by using endothelial colony forming cells (ECFCs), and we used it to explore the vascular niche function in patients with low-risk myelodysplastic syndromes (MDS). Overall, we investigated 56 patients and we observed higher levels of ECFCs in MDS than in healthy controls; moreover, MDS ECFCs were found variably hypermethylated for p15INK4b DAPK1, CDH1, or SOCS1. MDS ECFCs exhibited a marked adhesive capacity to normal mononuclear cells. When normal CD34+ cells were co-cultured with MDS ECFCs, they generated significant lower amounts of CD11b+ and CD41+ cells than in co-culture with normal ECFCs. At gene expression profile, several genes involved in cell adhesion were upregulated in MDS ECFCs, while several members of the Wingless and int (Wnt) pathways were underexpressed. Furthermore, at miRNA expression profile, MDS ECFCs hypo-expressed various miRNAs involved in Wnt pathway regulation. The addition of Wnt3A reduced the expression of intercellular cell adhesion molecule-1 on MDS ECFCs and restored the defective expression of markers of differentiation. Overall, our data demonstrate that in low-risk MDS, ECFCs exhibit various primary abnormalities, including putative MDS signatures, and suggest the possible contribution of the vascular niche dysfunction to myelodysplasia.

Effect of antiviral therapy on pro-angiogenic hematopoietic and endothelial progenitor cells in HIV-infected people.

BACKGROUND: HIV infection is an independent risk factor for cardiovascular disease. HIV-sustained impairment of endothelial progenitor cells (EPCs) could contribute to this process, so that it is important to assess whether antiviral therapy (ART) is able to revert these abnormalities. METHODS: We quantified in 21 naïves and 34 treated patients two functionally distinct clonogenic progenitors which have been acknowledged important for vascular repair: the hematopoietic progenitor colony forming unit - endothelial cells (CFU-EC) and the true endothelial progenitor, the endothelial colony forming cells (ECFC). We correlated results obtained with conventional vascular risk factors and with HIV-related parameters. RESULTS: We found that these progenitors behaved differently in naive and treated patients. In particular, CFU-EC level was significantly low in all naive patients and slowly recovered during ART. In contrast, the ECFC level was abnormally high in naive patients while it decreased upon ART. The CFU-EC level was related to conventional cardiovascular risk factors, as reported in general population, but also to inflammatory indexes and CD4 cell count. In contrast, the ECFC number was exclusively related to viral replication activity and to CD4 cell count. CONCLUSIONS: In HIV-infected people, the levels of CFU-EC and ECFC are related to classical cardiovascular risk factors but, in addition, they are also significantly influenced by the infection itself and by antiviral therapy.

Hypoxia-inducible factor-1α(Pro-582-Ser) polymorphism prevents iron deprivation in healthy blood donors.

BACKGROUND: Frequent blood loss induces progressive depletion of iron stores, leading to iron deficiency and, ultimately, to overt iron-deficient anaemia. The erythropoietin-mediated bone marrow response to anaemia is under the control of hypoxia-inducible factors (HIF), the master regulators of oxygen and iron homeostasis. Since the HIF-1α(Pro-582-Ser) variant is associated with elevated trans-activation capacity of hypoxia responsive elements of target genes, we investigated whether the HIF-1α(Pro-582-Ser) polymorphism might influence the response to repeated blood withdrawals. MATERIALS AND METHODS: Using polymerase chain reaction analysis and DNA sequencing, we retrospectively investigated the presence of HIF-1α(Pro-582-Ser) in a series of 163 blood donors. Haematological findings, serum ferritin levels and frequency of donations were compared according to the mutational status of the HIF-1α gene. RESULTS: We found that male carriers of the HIF-1α(Pro-582-Ser) polymorphism had higher haemoglobin and ferritin levels than individuals homozygous for the wild-type allele. Moreover, the HIF-1α(Pro-582-Ser) polymorphism protected regular blood donors from developing iron deficiency and anaemia and predicted uninterrupted donation activity. DISCUSSION: These findings show for the first time that the HIF-1α(Pro-582-Ser) polymorphism significantly affects red blood cell and iron homeostasis after blood loss, conferring to male carriers a resistance to anaemia. Regarding the female gender, large series of individuals should be investigated to establish whether there is an effect of the HIF-1α(Pro-582-Ser) polymorphism in this population. Although these data need to be confirmed in prospective studies, they could have important implications in blood donor selection and donation procedures.

Endothelial progenitor cells and thrombosis.

The remodelling of existing vessels (i.e. angiogenesis) and the "de novo" vessel formation (i.e. vasculogenesis) occur not only during the embryonic development but also over the entire postnatal life. In 1997, the Asahara group first reported that endothelial progenitor cells circulate in peripheral blood and that they are recruited at sites of ischemia, thus proving that these cells are able to promote vasculogenesis. Since then, several different approaches have been set up to investigate endothelial progenitor cells. This review summarizes the different modalities utilized to enumerate these cells, delineates their involvement in the haemostatic pathways, and depicts their altered trafficking during cardiovascular diseases. Finally, recent observations suggesting a primary role for endothelial progenitors in particular situations such as pulmonary arterial hypertension or Philadelphia negative-myeloproliferative neoplasms are discussed.

Spontaneous myogenic differentiation of Flk-1-positive cells from adult pancreas and other nonmuscle tissues.

At the embryonic or fetal stages, autonomously myogenic cells (AMCs), i.e., cells able to spontaneously differentiate into skeletal myotubes, have been identified from several different sites other than skeletal muscle, including the vascular compartment. However, in the adult animal, AMCs from skeletal muscle-devoid tissues have been described in only two cases. One is represented by thymic myoid cells, a restricted population of committed myogenic progenitors of unknown derivation present in the thymic medulla; the other is represented by a small subset of adipose tissue-associated cells, which we recently identified. In the present study we report, for the first time, the presence of spontaneously differentiating myogenic precursors in the pancreas and in other skeletal muscle-devoid organs such as spleen and stomach, as well as in the periaortic tissue of adult mice. Immunomagnetic selection procedures indicate that AMCs derive from Flk-1(+) progenitors. Individual clones of myogenic cells from nonmuscle organs are morphologically and functionally indistinguishable from skeletal muscle-derived primary myoblasts. Moreover, they can be induced to proliferate in vitro and are able to participate in muscle regeneration in vivo. Thus, we provide evidence that fully competent myogenic progenitors can be derived from the Flk-1(+) compartment of several adult tissues that are embryologically unrelated to skeletal muscle.

Myogenic potential of adipose-tissue-derived cells.

Adipose-tissue-derived mesenchymal stem cells can be directed towards a myogenic phenotype in vitro by the addition of specific inductive media. However, the ability of these or other adipose-tissue-associated cells to respond to ;natural' myogenic cues such as a myogenic environment has never been investigated in detail. Here, we provide evidence that a restricted subpopulation of freshly harvested adipose-tissue-derived cells possesses an intrinsic myogenic potential and can spontaneously differentiate into skeletal muscle. Conversion of adipose-tissue-derived cells to a myogenic phenotype is enhanced by co-culture with primary myoblasts in the absence of cell contact and is maximal when the two cell types are co-cultured in the same plate. Conversely, in vitro expanded adipose-tissue-derived mesenchymal stem cells require direct contact with muscle cells to generate skeletal myotubes. Finally, we show that uncultured adipose-tissue-associated cells have a high regenerative capacity in vivo since they can be incorporated into muscle fibers following ischemia and can restore significantly dystrophin expression in mdx mice.

SDF-1 involvement in endothelial phenotype and ischemia-induced recruitment of bone marrow progenitor cells.

Chemokine stromal derived factor 1 (SDF-1) is involved in trafficking of hematopoietic stem cells (HSCs) from the bone marrow (BM) to peripheral blood (PB) and has been found to enhance postischemia angiogenesis. This study was aimed at investigating whether SDF-1 plays a role in differentiation of BM-derived c-kit(+) stem cells into endothelial progenitor cells (EPCs) and in ischemia-induced trafficking of stem cells from PB to ischemic tissues. We found that SDF-1 enhanced EPC number by promoting alpha(2), alpha(4), and alpha(5) integrin-mediated adhesion to fibronectin and collagen I. EPC differentiation was reduced in mitogen-stimulated c-kit(+) cells, while cytokine withdrawal or the overexpression of the cyclin-dependent kinase (CDK) inhibitor p16(INK4) restored such differentiation, suggesting a link between control of cell cycle and EPC differentiation. We also analyzed the time course of SDF-1 expression in a mouse model of hind-limb ischemia. Shortly after femoral artery dissection, plasma SDF-1 levels were up-regulated, while SDF-1 expression in the bone marrow was down-regulated in a timely fashion with the increase in the percentage of PB progenitor cells. An increase in ischemic tissue expression of SDF-1 at RNA and protein level was also observed. Finally, using an in vivo assay such as injection of matrigel plugs, we found that SDF-1 improves formation of tubulelike structures by coinjected c-kit(+) cells. Our findings unravel a function for SDF-1 in increase of EPC number and formation of vascular structures by bone marrow progenitor cells.