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.

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.

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.

Chemotherapy-Induced Neutropenia in HIV Positive Patients with Lymphoma: Comparison of Pegfilgrastim with Daily Filgrastim Administration.

We retrospectively compared the incidence of neutropenia in two groups of HIV patients with lymphoma, who underwent chemotherapy supported by once-per-cycle administration of pegfilgrastim or by daily subcutaneous injection of filgrastim, respectively. Our findings indicate that pegfilgrastim and filgastrim produce similar results in preventing both neutropenia and febrile neutropenia.

A three-step pathway comprising PLZF/miR-146a/CXCR4 controls megakaryopoiesis.

MicroRNAs (miRNAs or miRs) regulate diverse normal and abnormal cell functions. We have identified a regulatory pathway in normal megakaryopoiesis, involving the PLZF transcription factor, miR-146a and the SDF-1 receptor CXCR4. In leukaemic cell lines PLZF overexpression downmodulated miR-146a and upregulated CXCR4 protein, whereas PLZF knockdown induced the opposite effects. In vitro assays showed that PLZF interacts with and inhibits the miR-146a promoter, and that miR-146a targets CXCR4 mRNA, impeding its translation. In megakaryopoietic cultures of CD34(+) progenitors, PLZF was upregulated, whereas miR-146a expression decreased and CXCR4 protein increased. MiR-146a overexpression and PLZF or CXCR4 silencing impaired megakaryocytic (Mk) proliferation, differentiation and maturation, as well as Mk colony formation. Mir-146a knockdown induced the opposite effects. Rescue experiments indicated that the effects of PLZF and miR-146a are mediated by miR-146a and CXCR4, respectively. Our data indicate that megakaryopoiesis is controlled by a cascade pathway, in which PLZF suppresses miR-146a transcription and thereby activates CXCR4 translation.