Serum Thrombopoietin Concentrations Research Articles

Mpl Expression on AML Blasts Predicts Cytopenia

Acute myeloid leukemia (AML) induces profound impairment of healthy hematopoiesis. The production deficit in the bone marrow (BM) leads to development of peripheral anemia, thrombocytopenia and neutropenia, which is a major cause of AML-associated morbidity and mortality. Despite much progress in understanding of AML biology, the mechanisms by which AML blasts interact with elements of normal hematopoiesis to cause cytopenia are unclear.Conventional wisdom has it that blasts infiltrate the marrow and displace normal hematopoiesis. If this concept were to be true, there should be a strong correlation between BM blast count and peripheral cytopenia. Surprisingly, analysis of 223 patients with newly diagnosed AML at a tertiary referral center revealed lack of correlation between initial BM blast count [% of cellularity] and hemoglobin level (ρ=-0.11, P=0.12), platelet count (ρ=-0.00, P=0.53) and absolute neutrophil count (ρ=0.13, P=0.06). This indicates that mechanisms other than displacement of normal hematopoiesis dictate the severity of cytopenia in AML patients.Hematopoiesis is tightly regulated by cytokines. Among them, thrombopoietin (TPO) acts through its receptor c-Mpl as the master regulator of megakaryopoiesis, but also exerts upstream effects on hematopoietic stem and progenitor cells (HSPC). TPO levels are controlled by receptor-mediated scavenging by cells carrying c-Mpl on the surface, with platelets representing the lion's share in a healthy organism. This negative feedback loop results in strong negative correlation between serum TPO concentration and platelet count in the steady state. When we examined this relationship in our AML cohort, TPO levels did not follow the expected negative correlation with platelet counts (ρ=-0.10, P=0.59). Comparison with historic controls with thrombocytopenia induced by chemotherapy for non-hematopoietic malignancy revealed that the lack of correlation was driven by AML cases with severe thrombocytopenia that had lower than expected levels of TPO in the serum.As HSPC are known to express c-Mpl, we hypothesized that HSPC-derived AML blasts may also express the receptor and cause insufficiency of hematopoiesis by means of receptor-mediated TPO scavenging. To test this hypothesis, we compared c-Mpl expression on blasts in AML cases with severe thrombocytopenia and low TPO concentration (potential scavenger cases) to cases with TPO levels adequate for the degree of cytopenia. Both surface flow cytometry and qPCR demonstrated higher c-Mpl expression in potential scavenger cases (3.1-fold, P=0.02).To determine whether this difference in expression translates into increased serum TPO clearance, we incubated AML blasts with high (c-Mpl+) and low (c-Mpl-) receptor expression in serum containing recombinant human TPO at a concentration of 100 pg/mL. After 2h, TPO clearance reached 45 pg per 106 cells in wells with c-Mpl+ blasts, compared to only 4 pg per 106 cells in wells with c-Mpl- blasts (P=0.02). This confirms the hypothesis that AML blasts can lower TPO levels by virtue of their c-Mpl expression.Validation studies in an independent, multi-center Dutch-Belgian-Swiss cohort of 437 AML cases confirmed lack of correlation between initial BM blast count and cytopenia. Ranked gene list correlation analysis of whole genome microarray data proved significant enrichment of the MPL transcript in patients with severe thrombocytopenia when compared to patients with average platelet counts (rank 27/20'589, FDR<10-6). MPL enrichment could also be observed in patients with severe neutropenia (P<0.01), but there was no correlation between MPL transcript level and degree of anemia.Lastly, we asked if MPL expression was related to cytogenetic or molecular AML subtype: indeed, microarray analysis showed higher MPL expression in cases of AML with t(8;21) than in any other subtype (P<10-4). Concurrently, these patients displayed significantly lower platelet count (40 vs 83 x 109/L, P=0.02) when compared to all other AML cases.In summary, our study demonstrates that cytopenia in AML is independent of BM blast count, but strongly correlated with c-Mpl expression on blasts. We show that c-Mpl+ blasts clear TPO, causing insufficient TPO levels and contributing to development of thrombocytopenia and neutropenia. The work may have important ramifications for treatment of AML-induced cytopenia, especially in the relapsed or refractory setting. DisclosuresNo relevant conflicts of interest to declare.

Identification of a Novel Splice Donor Mutation In the Thrombopoietin Gene In a Philippine Family with Hereditary Thrombocythemia

AbstractAbstract 3086 Background:Hereditary thrombocythemia (HT) is a rare autosomal dominant disorder related to mutations in either the gene encoding thrombopoietin (THPO), or its receptor MPL. In some cases of HT, mutational involvement of the THPO or MPL genes has been excluded. To date, five HT families with three distinct THPO mutations have been published, including Dutch, Japanese, and Polish pedigrees. In all cases, the mechanism of overproduction of platelets is related to alteration of the 5′ untranslated region (5′ UTR) of the THPO gene which results in enhanced translation of thrombopoietin (TPO) mRNA. We present our analysis of a Philippine family with a novel THPO gene mutation which segregates with the thrombocytosis phenotype. Methods:Informed consent was obtained from research participants. Peripheral blood was obtained from 6 family members, and serum was collected from 10 healthy adults. DNA was extracted with the Puregene DNA Isolation Kit (Qiagen). For the human TPO ELISA assay, the serum TPO concentrations of the family members as well as the healthy controls were measured with the human TPO Quantikine kit (R&D Systems). The exon 2 to intron 3 region of THPO gene covering the 3 previously reported mutations was amplified and purified PCR products were sequenced. To examine the functional effects of increased TPO levels on downstream JAK-STAT signaling, freshly obtained PB samples were incubated for 15 minutes at 37C, followed by fixation with paraformaldehyde and lysis of red blood cells. Fixed cells were permeabilized with methanol and stained with a combination of surface marker and intracellular phospho-specific antibodies, followed by analysis on a LSRII flow cytometer. Data analysis was performed with FlowJo (Tree Star). Results:The proband (see Figure 1a, pedigree subject II-1, arrow) is a 39 year-old Philippine woman who was informed at age 19 that she had an elevated platelet count. Although placed on hydroxyurea, anagrelide, and interferon-α in the distant past, she was currently maintained on only low-dose aspirin. At the time of her presentation at Stanford Cancer Center in March 2010, her complete blood count revealed a platelet count of 1,015,000/mm3 without other abnormalities. The peripheral blood smear revealed occasional large, hypogranular platelets. Reactive causes of thrombocytosis were excluded and her examination was normal. JAK2 V617F mutation analysis was negative. Routine CBC evaluation of her two children revealed thrombocytosis in her 11 year-old daughter (subject III-1; platelet count 550,000/mm3) and 9-year old son (subject III-2; platelet count 759,000/mm3). None of the three family members with thrombocytosis experienced a history arterial or venous thrombosis nor vasomotor symptoms. As shown in Figure 1b, DNA sequencing revealed a novel heterozygous mutation of T>C at the splice donor site of intron 2 in the proband (II-1) and her two children (III-1, III-2), while the proband's parents (I-1, I-2) and husband (II-2)were wild type at this site. In Figure 1a, the pedigree of the six family members with serum TPO concentrations (pg/mL) (1st row) and platelet counts (/mm3)(2nd row) is shown. Figure 1c demonstrates that the serum TPO concentration of family members with the THPO mutation was significantly higher than those family members without the mutation (un-paired t-test, p=0.0378), or healthy controls (p=0.0003). The TPO level in non-affected family members showed no statistical difference with healthy controls (p=0.98). In Figure 1d, basal phosphorylated STAT5 (pSTAT5) levels in CD3−/CD66−/CD14− progenitors were evaluated, and the 95th percentile is presented in the mean with SEM format. An un-paired t-test revealed that pSTAT5 levels were significantly higher in the affected group (p = 0.024, denoted by *). Conclusion:In our Philippine family, we have identified a novel heterozygous mutation at the conserved T in the invariant donor splice site of intron 2 of the THPO gene. Mutations at this position result in splicing errors, leading to exon skipping, intron retention or exposure of cryptic splice sites. Loss of the inhibitory wild-type 5′UTR has been shown to result in enhanced THPO transcription. This autosomal dominant gain of function germline mutation is associated with thrombocytosis, increased TPO levels, and constitutive activation of JAK-STAT signaling. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Identification of reduced serum thrombopoietin concentrations in patients with chronic hepatitis C undergoing an interferon therapy

Identification of reduced serum thrombopoietin concentrations in patients with chronic hepatitis C undergoing an interferon therapy

Alteration of serum thrombopoietin levels in patients with chronic hepatitis C under interferon therapy

Thrombocytopenia is commonly observed during interferon-alpha (IFN-alpha) therapy in patients with chronic hepatitis C. Since thrombopoietin (TPO) is the main regulator of thrombopoiesis, thrombocytopenia may partially be due to a reduced TPO generation. Because of the developments of the second generation of TPO mimetic drugs patients with reduced TPO levels should be identified possibly having a benefit by medicinal stimulation of thrombopoiesis. Therefore, platelet count and serum TPO concentration of patients receiving an interferon-alpha therapy were determined.Twelve patients treated with IFN-alpha (daily 10 x 106 IU s.c. for four weeks) in cause of chronic hepatitis C were examined during the first month of therapy. Serum TPO concentration significantly decreased from 80.8+/-48.0 to 34.6+/-24.5 pg/ml (p<0.05, Mann-Whitney test), and platelet count declined from 214,417+/-48,292 to 151,333+/-44,726 platelets/microl. During the following three weeks platelet count remained at a low level, while serum TPO increased to normal range.In conclusion, an interferon treatment causes reduced serum TPO level during the first week of therapy accompanied by decreased platelet count. The reduction in TPO synthesis contributes to the development of thrombocytopenia in patients during interferon therapy.

Fluctuations in thrombopoietin, immature platelet fraction, and glycocalicin levels in a patient with cyclic thrombocytopenia

Cyclic thrombocytopenia (CT) is an uncommon disorder characterized by periodic fluctuations in platelet count, resulting in alternating episodes of thrombocytopenia and normal platelet counts. Its pathogenesis remains unclear. Here, we report the case of a 65-year-old man with CT who was initially diagnosed with idiopathic thrombocytopenic purpura (ITP) concomitant with chronic thyroiditis. ITP was diagnosed 12 years ago in the absence of periodic fluctuations in platelet counts. He had been treated with corticosteroids; underwent splenectomy; and subsequently been treated with azathioprine, vincristine, high doses of dexamethasone, and herbal medicine. He had not received antibiotic eradication therapy for Helicobacter pylori because there was no evidence of infection with this organism. Since his symptoms did not improve, the treatments were discontinued, and he was placed under observation. He complained of mild bleeding symptoms, such as petechiae and purpura, which occurred intermittently for several months before he presented to us to undergo detailed investigations. His platelet count varied between 3 9 10/ll and 30 9 10/ll approximately every 3–4 weeks. His white blood cell count and hemoglobin concentration remained unchanged. To elucidate the mechanism underlying this disease, we evaluated the serum thrombopoietin (TPO) level, immature platelet fraction (IPF), plasma glycocalicin index normalized for the individual platelet count (GCI), and T helper (Th)1/Th2 ratio. The serum TPO level was measured with a human TPO ELISA kit (R&D Systems Inc., Minneapolis, MN, USA). The serum levels of TPO, a principal regulator of megakaryogenesis and thrombopoiesis, are thought to be regulated via receptor-mediated clearance by platelets and megakaryocytes. The median serum TPO concentration in healthy individuals is 51 pg/ml. The plasma glycocalicin level was measured with a Glycocalicin EIA kit (Takara Bio Inc., Ohtsu, Japan). The GCI was calculated as proposed by Steinberg et al. [1]: GCI = glycocalicin level 9 250 9 10/individual platelet count (/ll). Glycocalicin is a proteolytic fragment of the a-chain of glycoprotein Ib, a platelet membrane. The GCI reflects the rate of platelet destruction [2]. The mean GCI in healthy individuals is 1.27 (range 0.87–1.77). The IPF was determined to reliably quantify reticulated platelet counts by using a fully automated hematology analyzer XE-2100 equipped with special software IPF Master (Sysmex, Kobe, Japan). Reticulated platelets are RNA-rich immature platelets and are thought to reflect the ability of the bone marrow to produce platelets. Therefore, the IPF, as a surrogate marker of the reticulated platelet count, reflects the rate of thrombopoiesis [3]. The mean IPF in healthy individuals is 2.0% (range 0.5–5.7%). The Th1/Th2 ratio was determined by using flow cytometry analysis to measure the ratio of CD4? cells containing intracellular interferon-c to those containing interleukin-4. The fluctuations in the TPO levels, percentage of IPF, and GCI were synchronous and inversely proportional to those in the platelet counts (Fig. 1). In the thrombocytopenic phase, elevated GCI indicated platelet destruction in this patient. Thrombopoiesis was simultaneously accelerated in response to TPO. Consequently, the IPF, which is as an indicator of thrombopoiesis, increased. In the present case, CT seemed to be closely associated with cyclic increases in platelet destruction. However, the mechanism of cyclic platelet destruction remains to be elucidated. Th1/Th2 balance is T. Yujiri (&) Y. Tanaka M. Tanaka Y. Tanizawa Third Department of Internal Medicine, Yamaguchi University School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi 755-8505, Japan e-mail: yujirit@yamaguchi-u.ac.jp

Hematopoietic Stem/Progenitor Cell Mobilization in Donors and Recipients after Living Donor Liver Transplantation

Combination therapy with interferon-α and anti-viral drug is the current treatment of choice for chronic hepatitis viral infection. However, an important number of patients fail to respond to this therapeutic strategy and develop cirrhosis or liver cancer. Liver transplantation (mainly living donor liver transplantation (LDLT) in Japan) is known to be the ultimate therapy for them. To clarify the association of liver regeneration and hematopoietic stem/progenitor cells (HSCs), we quantified the number of circulating CD34+ cells (CD34+ cell number) and serum concentration of thrombopoietin (TPO) before and after surgery in 10 donors and 9 recipients undergoing LDLT. The evaluation of CD34+ cells has been carried out by flow cytometry, by applying conventional protocols. In donors, CD34+ cell number increased from 3.69 ± 2.87 cells/μL at pre-LDLT to 8.25 ± 4.94 cells/μL at post-operative day (POD) 7. Platelet count increased from 209 ± 50 × 109/L at pre-LDLT to 273 ± 23 × 109/L at POD 7–11. In recipients, although CD34+ cell number was 0.78 ± 0.73 cells/μL at pre-LDLT and significantly lower than that in healthy volunteers (3.78 ± 3.93 cells/μL), the number at POD 9–42 increased to 4.25 ± 3.55 cells/μL. Platelet count increased from 64 ± 35 × 109/L at pre-LDLT to 197 ± 91 × 109/L at POD 9–42. Serum TPO concentration at pre-LDLT was 0.98 ± 0.61 fmol/L in donors and 1.00 ± 0.35 fmol/L in recipients. TPO level peaked at POD 3–7 (3.14 ± 1.67 fmol/L) in donors and at POD 7–22 (6.74 ± 3.13 fmol/L) in recipients. It has been reported that mobilization of HSCs after partial hepatectomy in donors or LDLT in recipients was likely enhanced by increased serum levels of granulocyte colony-stimulating factor (peaked at POD 1), interleukin-6 and stem cell factor (POD 7). However, in our study, TPO (peaked at POD 7–22) was strongly associated with not only the increase of platelet count (peaked at POD 9–42) but also the mobilization of HSCs (POD 9–42) in recipients. Both mobilized HSCs and platelets may contribute to the liver regeneration after LDLT.

Preoperative serum thrombopoietin levels are higher in patients with ovarian cancer than with benign cysts

Objective To assess the diagnostic relevance of serum thrombopoietin (TPO) levels, we compared serum TPO levels between the patients with ovarian cancer and benign ovarian cysts. We also correlated serum TPO concentrations in ovarian cancer patients to know prognostic factors such as disease stage, tumor grade, histological subtype, and residual tumor mass. Study design Preoperative serum TPO levels were measured in women with epithelial ovarian cancer ( n = 51) and women with benign ovarian cysts ( n = 25) using an enzyme-linked immunosorbent assay. Results The serum TPO concentration was significantly elevated in the ovarian cancer patients as compared to the benign patient controls. Platelet counts and TPO in the serum did not correlate in the ovarian cancer patients. However, using a TPO cutoff of 90 pg/ml and a CA125 cutoff of 30 units/ml, when both markers were elevated, the specificity was as high as 92%. Conclusion Serum TPO concentrations may have a role in the diagnostic clinical setting for discerning benign from malignant ovarian tumors.

Thrombopoietin in the Cerebrospinal Fluid of Patients with Aseptic and Bacterial Meningitis

Despite the recent evidence of the localization of thrombopoietin (TPO) and its receptor in the central nervous system (CNS), TPO protein concentrations in the cerebrospinal fluid (CSF) remained to be clarified. We previously reported that serum TPO is increased in children with meningitis. To determine changes in TPO concentrations in the CSF by meningitis and to explore the relationship between serum and CSF TPO concentrations, we measured TPO concentrations in 110 CSF samples and 33 serum/CSF pairs from 11 bacterial meningitis, 49 aseptic meningitis, and 50 nonmeningitis children. In only 12% (13 of 110) of CSF samples (0 bacterial meningitis, 8 aseptic meningitis, and 5 controls), TPO concentrations could be determined (24.1 +/- 29.0 pg/ml). CSF TPO concentrations did not significantly differ among the three groups and did not correlate with age. TPO concentrations in all serum samples were detectable, and mean concentrations in bacterial meningitis (510.6 +/- 237.0 pg/ml) were significantly higher than those in aseptic meningitis (136.6 +/- 71.6, p < 0.01) and controls (181.3 +/- 88.3, p < 0.01). These findings suggest that TPO is not produced in the CNS of patients with meningitis and that TPO did not cross the blood-brain barrier even during meningeal infection.

Thrombopoietin and Interleukin-6 in Children with Pneumonia-Associated Thrombocytosis

The aim of this study was to investigate why some, but not all, children develop thrombocytosis during the course of pneumonia. The retrospective study included 40 healthy children and 75 children with pneumonia: 17 patients with platelet count within the reference values, i.e., platelet count </=450 x 10(9)/L, and 58 with thrombocytosis >450 x 10(9)/L. Erythrocyte sedimentation rate, leukocyte and platelet counts, and concentrations of hemoglobin, C-reactive protein, interleukin-6 and thrombopoietin were determined in the blood of patients and control groups of children. Patients with thrombocytosis were slightly younger (3.0 +/- 1.8 years and median 2.5 years, respectively) than patients with normal platelet count (3.8 +/- 2.4 years and median 4 years, respectively). Additionally, according to clinical and radiological findings, pneumonia in children with thrombocytosis had a more severe and protracted course. Serum thrombopoietin concentrations were found to be 91.2 +/- 41.7 ng/L (range: 14.3-166.7 ng/L) in patients with normal platelet count (313 +/- 70 x 10(9)/L, range: 206-428 x 10(9)/L). In patients with thrombocytosis (581 +/- 131 x 10(9)/L, range: 450-830 x 10(9)/L) serum thrombopoietin ranged from 63.6 to 1115.9 ng/L (526.6 +/- 268.4 ng/L). In these patients both concentration of hemoglobin (114 +/- 12 g/L) and iron (4.3 +/- 1.3 micromol/L) significantly decreased as compared with the control group. Study results suggested the possible development of reactive thrombocytosis in children with pneumonia. As platelets are involved in inflammatory reaction, reactive thrombocytosis might be part of the mechanism of defense. Reactive thrombocytosis may develop as a sequel of either anemia or inflammatory reaction (or both).

Investigating the relationship between serum thrombopoietin kinetics and the platelet-sparing effect: A clinical pharmacological evaluation of combined paclitaxel and carboplatin in patients with non-small cell lung cancer

We conducted a clinical pharmacological evaluation of paclitaxel/carboplatin combination in Japanese patients with non-small cell lung cancer. The purpose of this study was to identify the optimal dose of this combination and to investigate the relationships between the pharmacokinetic profiles of these 2 drugs, serum thrombopoietin (TPO) kinetics and the platelet-sparing effect. Patients received paclitaxel at 180-225 mg/m(2) by intravenous infusion over 3 h, followed by carboplatin at a target area under the concentration-time curve (AUC) of 6 mg/ml x min as a 1-h infusion. Serum paclitaxel, free platinum and TPO concentrations were measured using high-performance liquid chromatography, atomic absorption spectrometry and a double-sandwich enzyme-linked immunosorbent assay, respectively. Thirteen patients were enrolled. Neutropenia was the most frequent hematological toxicity and was significantly related to the time for which paclitaxel concentrations remained above 0.05 micro mol/ml. The prominent non-hematological toxicities were myalgia and sensory-dominant neuropathy. In this study, platelet and serum TPO kinetics were clearly different from those in our previous study of single-agent carboplatin (21). The platelet counts at the nadir were significantly higher (p<0.0001) in patients treated with paclitaxel/carboplatin combination (161,000+/-38,000/ micro l) compared with single-agent carboplatin (92,000+/-28,000/ micro l). The early increase in TPO (the percentage increase in TPO at day 4) was significantly greater (p=0.0345) in patients treated with paclitaxel/carboplatin combination (57.8+/-44.5%) compared with single-agent carboplatin (21.3+/-34.1%). The recommended doses are paclitaxel 210 mg/m(2) and carboplatin at an AUC of 6 mg/ml x min every 3 weeks. The observed platelet-sparing effect of the paclitaxel/carboplatin might be related to the early increase in circulating TPO levels, although the precise mechanism remains to be elucidated.

Quantification of hepatic thrombopoietin mRNA transcripts in patients with chronic liver diseases shows maintained gene expression in different etiologies of liver cirrhosis.

Platelet production is regulated by thrombopoietin (TPO), which is primarily synthesized in the liver. The TPO in patients with liver diseases could possibly be owing to impaired hepatic TPO production. As we reported previously, TPO serum levels are not decreased in patients with liver diseases compared with healthy controls and do not depend on the stage of cirrhosis or platelet count, but are highly elevated in patients with chronic virus hepatitis. To study possible mechanisms, we measured hepatic TPO mRNA levels in liver tissue samples from 31 liver cirrhosis patients by quantitative TaqMan real-time RT-PCR and corresponding serum TPO concentrations by ELISA. Median TPO serum levels were elevated in patients with viral hepatitis (n = 12) compared with patients with a biliary (n = 10), alcoholic (n = 6) or other (n = 3) disease etiology, while hepatic TPO mRNA levels did not differ. The TPO mRNA levels in patients with chronic liver diseases were not different from normal liver tissue sample. The TPO mRNA and TPO serum level did not correlate. We conclude that hepatic TPO gene expression appears to be maintained on a constitutive transcriptional level in patients with liver diseases and does not change dependent on disease etiology.

Colony-forming unit-megakaryocyte (CFR-meg) numbers and serum thrombopoietin concentrations in thrombocytopenic disorders: an inverse correlation in myelodysplastic syndromes.

We studied both serum-free colony-forming unit-megakaryocyte (CFU-meg) numbers and serum thrombopoietin (TPO) levels in 14 patients with aplastic anemia (AA), 37 patients with myelodysplastic syndromes (MDS) and 23 patients with idiopathic thrombocytopenic purpura (ITP) to assess thrombopoiesis in these thrombocytopenic disorders. The mean CFU-meg numbers were lower in AA and MDS patients (10.7 +/- 11.4 and 42.3 +/- 58.5/10(5) BMLD cells) than in healthy controls (103.1 +/- 57.3/10(5) BMLD cells) (P < 0.0001 and P= 0.0053, respectively), although they were distributed variably in MDS. ITP patients showed higher CFU-meg numbers (223.2 +/- 143.5/10(5) BMLD cells) (P= 0.017). The mean TPO concentrations were higher in both AA (986.8 +/- 500.8 pg/ml) and MDS patients (838.2 +/- 639.1 pg/ml) than in healthy controls (80.7 +/- 38.8 pg/ml) (P < 0.0001), although they were distributed from high to low in MDS. ITP patients showed a slight elevation of TPO (123.1 +/- 55.3 pg/ml) P = 0.0106). The TPO levels was inversely correlated to both platelet counts and CFU-meg numbers (correlative coefficient (CC): -0.719 and -0.682, P < 0.0001) in AA, but not in ITP. In MDS, the inverse correlation to TPO was stronger in CFU-meg (CC: -0.678, P < 0.0001) than in platelet counts (CC: -0.538, P = 0.0014), suggesting that CFU-meg plays an important role in regulating TPO production in this heterogenous disorder. CFU-meg and TPO may provide useful information for understanding thrombopoiesis of MDS, especially for application of TPO.

Pathophysiological significance of simultaneous measurement of reticulated platelets, large platelets and serum thrombopoietin in non-neoplastic thrombocytopenic disorders.

An automated reticulocyte counter using flowcytometric analysis, the R-3000 (Sysmex Inc. Kobe, Japan), has recently been modified to determine reticulated platelets (RPs) and large platelets (LPs). We measured frequencies of RPs, LPs in total platelet count and serum thrombopoietin concentration comprehensively in non-neoplastic thrombocytopenic patients with immune thrombocytopenic purpura (ITP, n = 23), aplastic anemia (AA, n = 21), liver cirrhosis (LC, n= 17), and hematologically normal subjects (control, n = 151). ITP was characterized as high frequencies of both RP and LP, AA as high RP frequency and elevated thrombopoietin concentration, and LC as no difference compared with control. Interestingly, the frequency of RP appeared to depend on total platelet count rather than the cause of thrombocytopenia, while the frequency of LP appeared to depend much less on total platelet count. Furthermore, significant positive correlations were observed between frequencies of RP and LP in control, ITP and LC subjects, in whom bone marrow stem cells are intrinsically normal. However, there was no such correlation in AA patients with stem cell deficiency, suggesting that this correlation might be a useful new parameter for detecting qualitatively abnormal platelets. Measurement of RP and LP is thus useful for elucidating the pathophysiology of thrombocytopenic disorders.

Expression of the Thrombopoietin Gene in Human Fetal and Neonatal Tissues

Thrombopoietin (TPO) regulates megakaryopoiesis and platelet production. In the adult, TPO is mainly produced by the liver and the kidneys. This study focuses on fetal and neonatal TPO mRNA expression. In 26 human fetuses and preterm neonates, samples from liver, kidney, spleen, lung, and bone marrow were extracted for total RNA. We measured platelet counts, TPO serum concentrations by enzyme-linked immunosorbent assay, and TPO mRNA contents by reverse transcription/competitive polymerase chain reaction. TPO mRNA concentrations per microgram total RNA were similar in liver, spleen, and bone marrow, slightly lower in kidney, and significantly lower in lung. When related to gram tissue, TPO mRNA levels were highest in the liver. Considering the total amount of TPO mRNA produced in liver, kidney, and spleen, the liver accounted for 95.3%. No correlations between TPO mRNA expression and serum TPO concentration, blood platelet count, or gestational age were observed. In conclusion, the liver is the primary site of TPO gene expression in human fetuses and neonates. The spleen may contribute to TPO production during fetal life. Like in the adult, TPO mRNA is expressed in fetal bone marrow.

Serum thrombopoietin levels in patients with chronic hepatitis and liver cirrhosis.

Thrombocytopenia is a common manifestation of cirrhosis. The aim of this study was to examine the relationship between serum thrombopoietin concentrations, circulating platelet levels, and the stage of hepatic fibrosis in patients with chronic viral hepatitis. The study included 48 patients with chronic viral hepatitis (14 with stage 1 fibrosis; five with stage 2 fibrosis; three with stage 3 fibrosis; 26 with cirrhosis) and 30 healthy volunteers. Serum thrombopoietin levels were measured using an enzyme-linked immunosorbent assay. Spleen size, platelet counts, and prothrombin time were measured. Thrombopoietin levels of patients with fibrosis stage 1 (2.50 +/- 1.60 fmol/ml) or stage 2 (1.89 +/- 0.65) were significantly higher than those in patients with cirrhosis (1.21 +/- 0.55) or healthy volunteers (1.26 +/- 0.74). Mean platelet counts of patients with cirrhosis (8.0 +/- 4.6 x 10(4)/microl) were significantly lower than those with fibrosis stage 1 (18.6 +/- 3.9) or stage 2 (16.0 +/- 5.8), or healthy volunteers (24.5 +/- 7.3). Patients with cirrhosis had larger spleens (30.9 +/- 18.4 cm2) than those with fibrosis stage 1 (18.2 +/- 6.4). Platelet counts showed a significant inverse relationship to spleen size (p = -0.51, p < 0.0005) and a significant positive relationship with thrombopoietin levels (p = 0.34, p < 0.02). Thrombopoietin levels were significantly correlated to prothrombin time (p = 0.45, p < 0.005). Serum thrombopoietin levels are elevated in patients with an early stage of chronic viral hepatitis. As the disease progresses from mild fibrosis to cirrhosis, decreased production of thrombopoietin may contribute to the further development of thrombocytopenia in cirrhosis.

Serum thrombopoietin levels in patients with chronic hepatitis and liver cirrhosis

OBJECTIVE: Thrombocytopenia is a common manifestation of cirrhosis. The aim of this study was to examine the relationship between serum thrombopoietin concentrations, circulating platelet levels, and the stage of hepatic fibrosis in patients with chronic viral hepatitis. METHODS: The study included 48 patients with chronic viral hepatitis (14 with stage 1 fibrosis; five with stage 2 fibrosis; three with stage 3 fibrosis; 26 with cirrhosis) and 30 healthy volunteers. Serum thrombopoietin levels were measured using an enzyme-linked immunosorbent assay. Spleen size, platelet counts, and prothrombin time were measured. RESULTS: Thrombopoietin levels of patients with fibrosis stage 1 (2.50 ± 1.60 fmol/ml) or stage 2 (1.89 ± 0.65) were significantly higher than those in patients with cirrhosis (1.21 ± 0.55) or healthy volunteers (1.26 ± 0.74). Mean platelet counts of patients with cirrhosis (8.0 ± 4.6 × 10 4/μl) were significantly lower than those with fibrosis stage 1 (18.6 ± 3.9) or stage 2 (16.0 ± 5.8), or healthy volunteers (24.5 ± 7.3). Patients with cirrhosis had larger spleens (30.9 ± 18.4 cm 2) than those with fibrosis stage 1 (18.2 ± 6.4). Platelet counts showed a significant inverse relationship to spleen size (ρ = −0.51, p < 0.0005) and a significant positive relationship with thrombopoietin levels (ρ = 0.34, p < 0.02). Thrombopoietin levels were significantly correlated to prothrombin time (ρ = 0.45, p < 0.005). CONCLUSIONS: Serum thrombopoietin levels are elevated in patients with an early stage of chronic viral hepatitis. As the disease progresses from mild fibrosis to cirrhosis, decreased production of thrombopoietin may contribute to the further development of thrombocytopenia in cirrhosis.

Hepatic thrombopoietin mRNA levels in acute and chronic liver failure of childhood.

The liver is the main production site of the hormone thrombopoietin (TPO), the major regulator of megakaryopoiesis. To investigate the role of an impaired TPO gene expression in the pathogenesis of thrombocytopenia in pediatric patients suffering from liver failure, we measured hepatic TPO mRNA in children with acute or chronic end-stage liver disease undergoing orthotopic liver transplantation. Tissue samples for RNA extraction were obtained from 12 children with compensated cirrhosis (CC), 22 children with decompensated cirrhosis (DC), and 9 children with acute liver failure (ALF). TPO mRNA was quantitated by competitive polymerase chain reaction (PCR), following reverse transcription (RT). Furthermore, in 9 children with ALF, serum TPO levels were measured by enzyme-linked immunosorbent assay before and 10 to 14 days after liver transplantation. The hepatic TPO mRNA concentration was highest in children with CC (median, 50.9 amol/micrograms RNA). This value was significantly reduced in children with DC (30.2 amol/micrograms RNA) or ALF (13.8 amol/micrograms RNA). Children with ALF (139 cells/nL) or DC (200 cells/nL) had lower platelet counts than children with CC (368 cells/nL). The serum TPO concentration increased from a median of 156 pg/mL in patients with ALF to 547 pg/mL after liver transplantation. These results show that the thrombocytopenia in children with liver failure is associated with reduced hepatic TPO mRNA levels. It remains to be investigated whether the serum TPO level and platelet counts are markers for the severity of liver damage that may serve as a prognostic indicator.

Evaluation of Thrombopoiesis in Thrombocytopenic Disorders by Simultaneous Measurement of Reticulated Platelets of Whole Blood and Serum Thrombopoietin Concentrations

To evaluate thrombopoiesis in thrombocytopenic disorders, we simultaneously determined reticulated platelet counts in whole blood by FACScan flow cytometry and serum thrombopoietin (TPO) concentrations by a sensitive sandwich ELISA. The subjects were 40 healthy volunteers and 45 thrombocytopenic patients. In idiopathic thrombocytopenic purpura (ITP), the percentage of reticulated platelets was significantly elevated (5.61 +/- 2.02%: mean +/- SD) relative to normal controls (2.17 +/- 0.90%), but serum TPO concentrations (1.91 +/- 1.27 fmol/l) did not differ significantly from the normal range (1.43 +/- 0.62 fmol/l). The patients with aplastic anemia (AA) had decreased reticulated platelet counts and markedly increased serum TPO concentrations (13.65 +/- 10.64 fmol/l). In thrombocytopenic patients with liver cirrhosis (LC), the absolute number of reticulated platelets (1.65 +/- 1.11 x 10(9)/l) decreased similarly that in AA. However, serum TPO concentrations (1.38 +/- 0.50 fmol/l) did not increase in contrast to AA. Our findings suggested a possible dual mechanism of thrombocytopenia in LC; that is, thrombocytopenia in LC results from the decreased TPO production primarily in the liver adding to an increase in platelet sequestration in the spleen.

Endogenous serum thrombopoietin concentrations in patients with myelodysplastic syndromes.

Prognosis in patients with myelodysplastic syndromes (MDS) is closely correlated with cytopenia. To date, no factor is available which is able to reliably stimulate megakaryopoiesis in vivo. Recently, the ligand of the mpl receptor was cloned and found to be thrombopoietin (TPO). We measured endogenous TPO serum levels in 69 patients suffering from MDS using an TPO receptor-based ELISA. Twenty-six of the patients suffered from refractory anemia (RA), 12 from RA with excess of blasts (RAEB), 25 from RAEB in transition (RAEBt), and six from chronic myelomonocytic leukemia (CMML). This assay uses a chimeric molecule consisting of the human TPO receptor fused to the Fc portion of human IgG as the capture reagent. Biotinylated antibody to TPO IgG was used for detection and the lower detection limit in serum was found to be 160 pg/ml. Samples obtained from healthy individuals with a normal platelet number were shown to be below detectable levels. In patients with RA, high endogenous serum TPO concentrations correlated with low platelet count and significantly elevated TPO concentrations were only found when megakaryopoiesis was absent or decreased in the bone marrow. This correlation was not detected in RAEB and RAEBt patients and no detectable TPO serum concentrations were found in six CMML patients whether they showed decreased or normal platelet count. Our data show that endogenous TPO production is upregulated by decreased circulating platelet count only in patients with refractory anemia. In the more advanced stages of MDS where the leukemic clone has further progressed, an inadequate TPO response occurs, possibly due to overexpression of the mpl receptor by the malignant clone.

A sensitive sandwich ELISA for measuring thrombopoietin in human serum: serum thrombopoietin levels in healthy volunteers and in patients with haemopoietic disorders.

A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) has been established to estimate serum thrombopoietin (TPO) concentrations in healthy volunteers and patients with haemopoietic disorders. The ELISA uses a mouse monoclonal antibody (Ab) as the capture Ab and a biotinylated rabbit polyclonal Ab as the detector. The ELISA was reproducible, highly sensitive and specific for human TPO. The coefficients of intra-and inter assay variation were from 3.0% to 4.9% and from 5.9% to 6.1%, respectively. The quantitative limit of the ELISA was 0.09 fmol/ml in serum. The quantitative limit was lower than the normal level. The dose-response curves of serum samples from healthy volunteers and patients with haemopoietic disorders were parallel to the standard curves. The ELISA did not cross-react with a variety of blood components and cytokines to produce false-positive results. The serum TPO concentrations from 29 normal males and 21 females were 0.79 +/- 0.35 and 0.70 +/- 0.26 fmol/ml, respectively. Serum TPO levels in patients with aplastic anaemia (AA), acute lymphocytic leukemia (ALL) and essential thrombocythaemia (ET) were measured using the ELISA. The serum TPO levels in the patients with ET (n = 6, 2.80 +/- 1.55 fmol/ml) were higher than the normal level. The patients with AA (n = 7, 18.53 +/- 12.37 fmol/ml) and ALL (n = 5, 10.36 +/- 5.57 fmol/ml) had significantly higher serum TPO levels than normal individuals. These results indicate that the ELISA specific to TPO should prove useful in measuring the TPO concentration in serum samples.