TPO Concentration Research Articles

Thrombopoietin (Tpo) in the fetus and neonate: Tpo concentrations in preterm and term neonates, and organ distribution of Tpo and its receptor (c-mpl) during human fetal development.

Little is known about thrombopoietin (Tpo) production in human fetuses and neonates. As a step toward determining whether Tpo is relevant to platelet production in the fetus and neonate, we hypothesized that: (1) like other cytokines, Tpo is present in the cord blood in higher concentrations than in adult plasma; (2) Tpo and its receptor (c-mpl) are expressed in fetuses at, and following, 5-6 weeks post-conception (when platelet production begins); and (3) the sites of Tpo and c-mpl production in the fetus are similar to those of adults. We quantified Tpo, by ELISA, in the plasma of 50 adults, as well as in the umbilical cord plasma of 50 preterm and term infants. We also characterized, by RT-PCR, the organ distribution of Tpo and c-mpl during fetal development (at 8 and 16 weeks). Tpo concentrations were measurable (> or =41 pg/ml) in only two of the 50 adult samples (44 and 46 pg/ml), but in 24 of the 50 cord plasma samples (of the 24 samples, the median was 62 pg/ml; mean+/-SD, 80+/-39 pg/ml). Tpo levels did not correlate with either gestational age or platelet count at birth. Similarly to adults, in the fetal tissues, Tpo transcripts were found in all organs tested, but the most dense bands were from liver. C-mpl transcripts were also predominantly from liver. We conclude that: (1) Tpo is present in higher concentrations in cord plasma than in venous plasma of adults; (2) Tpo and c-mpl transcripts are detected in human fetuses as early as the onset of platelet appearance; and(3) Tpo and c-mpl have a similar organ distribution in fetuses and adults.

Comparative study of photoinitiator curing efficiency using regression data analysis

Regression data analysis was used to compare two alphahydroxy ketone, 1-hydroxycyclohexyl phenyl ketone (HCPK) and2-hydroxy-2-methyl-1phenyl-propan-1-one (HMPP) and two phosphine oxide, 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (TPO) and bis (2,6-dimethoxybenzoyl) 2,4,4-trimethyl pentyl phosphine oxide (DMBAPO) photoinitiators in a thin coating application. Phosphine oxide is inherently more efficient, especially in white pigmented systems than alpha hydroxy ketone because of its stronger and broader absorption at longer wavelength. Due to molecular weight dilution effect, it is usually required to have a higher TPO concentration in a formulation than HCPK or HMPP to overcome oxygen inhibition. On the molecular level, however, DMBAPO is the most reactive photoinitiator among all of them. Data analysis also suggests that the number of initiating free radicals generated by DMBAPO is twice of that generated by HCPK or HMPP or TPO. This study also confirms that in thin coating applications the use of either nitrogen blanket orphotoinitiator blend is a good method for increasing productivity and reducing formulation cost.

Plasma thrombopoietin levels in thrombocytopenic states: implication for a regulatory role of bone marrow megakaryocytes.

To evaluate the diagnostic value of thrombopoietin (TPO, c-mpl ligand) measurements, and clarify the regulatory mechanisms of TPO in normal and in thrombocytopenic conditions, the plasma TPO concentration was determined in normal individuals (n = 20), umbilical cord blood (n = 40), chronic idiopathic thrombocytopenic purpura (ITP; n = 16), in severe aplastic anaemia (SAA; n = 3), chemotherapy-induced bone marrow hypoplasia (n = 10), myelodysplastic syndrome (MDS; n = 11), and sequentially during peripheral blood progenitor cell transplantation (n = 7). A commercially available ELISA and EDTA-plasma samples were used for the analysis. The plasma TPO concentration in the normals and umbilical cord blood were 52 +/- 12 pg/ml and 66 +/- 12 pg/ml, respectively. The corresponding values in patients with SAA and chemotherapy-induced bone marrow hypoplasia were 1514 +/- 336 pg/ml and 1950 +/- 1684 pg/ml, respectively, and the TPO concentration, measured sequentially after myeloablative chemotherapy and peripheral blood progenitor cell transplantation, was inversely related to the platelet count. In contrast, the plasma TPO recorded in patients with ITP (64 +/- 20 pg/ml) and MDS (68 +/- 23 pg/ml) were only slightly higher than normal levels. In conclusion, TPO levels were significantly elevated in patients in which bone marrow megakaryocytes and platelets in circulation were markedly reduced, whereas TPO levels were normal in ITP patients, and only slightly increased in the MDS patients. These latter patients displayed a preserved number of megakaryocytes in bone marrow biopsies. Our data support the suggestion that megakaryocyte mass affects the plasma TPO concentration. In thrombocytopenic patients a substantially increased plasma TPO implies deficient megakaryocyte numbers. However, TPO measurements do not distinguish between ITP and thrombocytopenia due to dysmegakaryopoiesis, as seen in MDS patients.

Serial Plasma Thrombopoietin (Tpo) Concentrations in Thrombocytopenic and Non-thrombocytopenic Neonates: Insights into the Mechanisms Causing Neonatal Thrombocytopenia † 1411

Serial Plasma Thrombopoietin (Tpo) Concentrations in Thrombocytopenic and Non-thrombocytopenic Neonates: Insights into the Mechanisms Causing Neonatal Thrombocytopenia † 1411

Adenovector-Mediated Expression of Human Thrombopoietin cDNA in Immune-Compromised Mice: Insights into the Pathophysiology of Osteomyelofibrosis

Thrombopoietin (TPO) cDNA can be effectively delivered in vivo by adenovectors. Immune normal mice (BALB/c) and syngeneic mice with variable degrees of immune dysfunction nu, SCID, and NOD-SCID) were treated with an adenovirus vector expressing the human TPO cDNA (AdTPO). Platelet peaks were significantly higher in SCID and NOD-SCID mice compared with BALB/c and nu mice. Human plasma TPO concentration correlated with the platelet counts. SCID and NOD-SCID mice exhibited also granulocytosis and increased numbers of hemopoietic progenitors in bone marrow. Following platelet peak, BALB/c mice developed autoantibodies against murine TPO leading to thrombocytopenia and depletion of megakaryocytes and hemopoietic progenitors in bone marrow. AdTPO-treated SCID mice developed osteomyelofibrosis and extramedullary/extrasplenal hemopoiesis. In contrast, NOD-SCID mice with a similar magnitude of TPO overexpression did not show fibrotic changes in bone marrow. We conclude, first, that a chronic high level of TPO overexpression stimulates megakaryocytopoiesis and myelopoiesis leading to thrombocytosis and granulocytosis. Second, increased megakaryocytopoiesis is not sufficient for development of secondary osteomyelofibrosis. The functionally deficient monocytes and macrophages of NOD-SCID mice probably prevented fibrotic marrow changes. Third, immune deficiency enhances expression of adenovirally mediated transgenes, and fourth, xenogeneic transgene delivered by adenovector to a host with normal immune functions may induce loss of immune tolerance and autoimmune phenomenon.

Regulation of the Serum Concentration of Thrombopoietin in Thrombocytopenic NF-E2 Knockout Mice

AbstractThe mechanisms that regulate circulating levels of thrombopoietin (Tpo) are incompletely understood. According to one favored model, the rate of Tpo synthesis is constant, whereas the serum concentration of free Tpo is modulated through binding to c-Mpl receptor expressed on blood platelets. Additionally, a role for c-Mpl expressed on megakaryocytes is suggested, particularly by the observation that serum Tpo levels are not elevated in human immune thrombocytopenic purpura. Whereas direct binding of Tpo to platelets has been demonstrated in vitro and in vivo, the role of megakaryocytes in modulating serum Tpo levels has not been addressed experimentally. The profoundly thrombocytopenic mice lacking transcription factor p45 NF-E2 do not show the predicted increase in serum Tpo concentration. To evaluate the fate of the ligand in these animals, we injected 125I-Tpo intravenously into mutant and control mice. In contrast to normal littermates, NF-E2 knockout mice show negligible association of radioactivity with blood cellular components, consistent with an absence of platelets. There is no corresponding increase in plasma-associated radioactivity to suggest persistence in the circulation. However, a greater fraction of the radioligand is bound to hematopoietic tissues. In the bone marrow this is detected virtually exclusively in association with megakaryocytes, whereas in the spleen it is associated with megakaryocytes and small, abnormal, platelet-like particles or megakaryocyte fragments that are found within or in close contact with macrophages. These findings implicate the combination of megakaryocytes and the latter particles as a sink for circulating Tpo in NF-E2 knockout mice, and provide an explanation for the lack of elevated serum Tpo levels in this unique animal model of thrombocytopenia.

Sensitive Measurement of Thrombopoietin by a Monoclonal Antibody Based Sandwich Enzyme-linked Immunosorbent Assay

In this report a sensitive enzyme-linked immunosorbent assay (ELISA) for the measurement of plasma thrombopoietin (Tpo) is described that is solely based on monoclonal antibodies (MoAbs). The assay has an intra and inter-assay variance of 5-7% and 7-13%, respectively. Native and recombinant human Tpo (rhTpo) were recognized equally well, no cross reactivity with other cytokines was found and rhTpo added to plasma and serum was completely recovered. With the ELISA, Tpo concentrations in EDTA-anticoagulated plasma of all controls (n = 193) could be determined, since the limit of detection (2 +/- 0.8 A.U./ml, mean +/- sd) was lower than the concentration found in controls (11 +/- 8 A.U./ml, mean +/- sd; 2.5th-97.5th percentile: 4-32 A.U./ml). Tpo levels in serum were on average 3.4 times higher than in plasma. We showed in vivo that Tpo is bound by platelets, as in thrombocytopenic patients (n = 5) a platelet transfusion immediately led to a drop in plasma Tpo level, whereas in patients receiving chemotherapy the induced thrombocytopenia was followed by a rise in plasma Tpo levels. In summary, these results indicate that this ELISA is a reliable tool for Tpo measurements and is applicable for large scale studies.

Myelopoiesis and Myeloproliferative Disorders

Myeloid cells arise from a common stem cell whose development is regulated by stimulatory and inhibitory growth factors. Pluripotential hematopoietic stem cells are most influenced by IL-3, GM-CSF, and stem cell factor while committed progenitor cells are regulated by variable concentrations of GM-CSF, G-CSF, M-CSF, IL-5, Epo, and Tpo. As a result of their common origin, a key point to remember about myeloproliferative disorders is the involvement of multiple cell lines in dysplastic and neoplastic conditions. Dysplastic changes may signal early neoplastic changes with cases progressing to acute leukemia. Myelodysplastic syndrome (MDS) is associated with anemia or multiple cytopenias, normal to hypercellular bone marrow, ineffective hematopoiesis, and less than 30% blast cells of all nucleated cells in the bone marrow. Chronic myeloid leukemias also have less than 30% blast cells of all nucleated cells in the bone marrow and are distinguished from MDS by elevated cell counts of one or more cell lines with mature forms predominating. Acute myeloid leukemias, often the end result of all myeloproliferative disorders, are recognized by equal or greater 30% blast cells of all nucleated cells in the bone marrow. Additional diagnostic information from cytochemical stains, immunohistochemical staining, and cytogenetic analysis can influence the final diagnosis when morphology alone is equivocal. In conclusion, prognosis and response to treatment are best determined by application of a uniform set of standards in evaluating hematolymphatic neoplasia. Critical to diagnosis are complete blood and bone marrow evaluations including observation for dysplastic changes and blast cell quantitation. In addition, evidence for tissue infiltration identified through cytologic or histologic evaluations of lymph node, spleen, or liver is recommended.

Combined effects of a thymic peptide, thymopoietin and myasthenic patient sera in rat myotube culture

We investigated in a rat myotube assay the combined effect of 26 myasthenic (MG) patient sera and a thymic peptide, thymopoietin (Tpo) which had previously been shown to bind Torpedo and human AChR and to complete with α-bungarotoxin (α-Bgt) binding. Cultures were first exposed to Tpo alone for 3 h (0.3, 7.5, 15 nM), then MG sera (5% final dilution) were added for an additional 18 h. Reduction in the amount of 125I-α-Bgt binding sites in the presence of various concentrations of Tpo were similar with control sera and in all the patients with low or undetectable anti-AChR Ab (11 cases). In cultures exposed to Tpo and sera with high anti-AChR Ab titre (15 cases), Tpo and anti-AChR Ab have an additive capacity to reduce the number of α-Bgt binding sites. The results are compatible with the hypothesis that anti-AChR Ab and Tpo could impair neuromuscular transmission by complementary mechanisms.