Maria Grazia Iachininoto

Myoendothelial Differentiation of Human Umbilical Cord Blood–Derived Stem Cells in Ischemic Limb Tissues

Abstract— 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.

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.

Endothelial progenitor cell trafficking in human immunodeficiency virus-infected persons.

Objective:Human immunodeficiency virus (HIV)-infected people exhibit a high incidence of vascular diseases. Since in the general population the high cardiovascular risk has been associated with an impaired endothelial cell function, we investigated circulating endothelial progenitor cells in HIV-positive patients. Design:We evaluated circulating colony-forming unit–endothelial cell (CFU-EC) and endothelial colony-forming cell (ECFC) progenitors in 14 antiviral therapy-naive HIV-positive patients, in comparison with 15 normal controls. Methods:CFU-EC and ECFC derived from peripheral blood mononuclear cells from HIV-infected and HIV-uninfected individuals were recovered and evaluated for HIV genome presence by PCR. Vascular endothelial growth factor (VEGF) and apolipoprotein B mRNA-editing enzyme catalytic polypeptide like (APOBEC) subunits expression were evaluated in infected colonies by real-time PCR. Results:We found that circulating CFU-EC but not ECFC were significantly reduced in HIV-positive patients and that proviral HIV DNA was detectable only in CFU-EC but not in ECFC. Furthermore, the expression of APOBEC subunits was significantly lower in CFU-EC than in circulating monocytes. Accordingly, the CFU-EC displayed a high content of proviral DNA copies, suggesting that these cells have a high sensitivity to the HIV infection. Conclusions:Although HIV does not affect the ‘true endothelial progenitor’ compartment, it infects and strongly depletes circulating endothelial progenitors with hematopoietic signature. We unravel a novel pathogenetic mechanism by which HIV infection might cause vascular diseases.

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-γ-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-γ-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.

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.

Adult and cord blood endothelial progenitor cells have different gene expression profiles and immunogenic potential

BACKGROUND Endothelial colony-forming cells (ECFC) are endowed with vascular regenerative ability in vivo and in vitro. In this study we compared the genotypic profile and the immunogenic potential of adult and cord blood ECFC, in order to explore the feasibility of using them as a cell therapy product. MATERIALS AND METHODS ECFC were obtained from cord blood samples not suitable for haematopoietic stem cell transplantation and from adult healthy blood donors after informed consent. Genotypes were analysed by commercially available microarray assays and results were confirmed by real-time polymerase chain reaction analysis. HLA antigen expression was evaluated by flow-cytometry. Immunogenic capacity was investigated by evaluating the activation of allogeneic lymphocytes and monocytes in co-cultures with ECFC. RESULTS Microarray assays revealed that the genetic profile of cord blood and adult ECFC differed in about 20% of examined genes. We found that cord blood ECFC were characterised by lower pro-inflammatory and pro-thrombotic gene expression as compared to adult ECFC. Furthermore, whereas cord blood and adult ECFCs expressed similar amount of HLA molecules both at baseline and after incubation with γ-interferon, cord blood ECFC elicited a weaker expression of pro-inflammatory cytokine genes. Finally, we observed no differences in the amount of HLA antigens expressed among cord blood ECFC, adult ECFC and mesenchymal cells. CONCLUSIONS Our observations suggest that cord blood ECFC have a lower pro-inflammatory and pro-thrombotic profile than adult ECFC. These preliminary data offer level-headed evidence to use cord blood ECFC as a cell therapy product in vascular diseases.

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.

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-β (TGF-β) or (iii) MEM with dexamethasone. The expression of cardiac markers (GATA4, GATA6, β-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-β) 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.

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.