Thrombopoietin in normal pregnancy and preeclampsia

Growth hormone receptor contributes to the activation of STAT5 in the hypothalamus of pregnant mice

Growth hormone (GH) receptor (GHR) signaling induces the phosphorylation of the signal transducer and activator of transcription 5 (pSTAT5) in the cells of several tissues including in the hypothalamus. During pregnancy, several STAT5-recruiting hormones (e.g., prolactin, GH and placental lactogens) are highly secreted. However, the precise contribution of GHR signaling to the surge of pSTAT5 immunoreactive neurons that occurs in the hypothalamus of pregnant mice is currently unknown. Thus, the objective of the present study was to determine whether GHR expression in neurons is required for inducing pSTAT5 expression in several hypothalamic nuclei during pregnancy. Initially, we demonstrated that late pregnant C57BL/6 mice (gestational day 14 to 18) exhibited increased pulsatile GH secretion compared to virgin females. Next, we confirmed that neuron-specific GHR ablation robustly reduces hypothalamic Ghr mRNA levels and prevents GH-induced pSTAT5 in the arcuate, paraventricular and ventromedial hypothalamic nuclei. Subsequently, the number of pSTAT5 immunoreactive cells was determined in the hypothalamus of late pregnant mice. Although neuron-specific GHR ablation did not affect the number of pSTAT5 immunoreactive cells in the paraventricular nucleus of the hypothalamus, reduced pSTAT5 expression was observed in the arcuate and ventromedial nuclei of pregnant neuron-specific GHR knockouts, compared to control pregnant mice. In summary, a subset of hypothalamic neurons requires GHR signaling to express pSTAT5 during pregnancy. These findings contribute to the understanding of the endocrine factors that affect the activation of transcription factors in the brain during pregnancy.

Refractory severe immune thrombocytopenia in a twin pregnancy

A 34-year-old woman presented at 29 weeks gestation of a twin pregnancy, with a platelet count of 1 × 10⁹/l. She was extensively investigated and was subsequently diagnosed with severe immune thrombocytopenia. She did not respond to initial treatment with corticosteroids and intravenous immunoglobulin. She also failed to respond to second-line therapies of Anti-D immunoglobulin, Azathioprine and the thrombopoietin agonist Romiplostim. Her case was further complicated by an episode of obstetric cholestasis possibly related to Azathioprine treatment. She went on to require plasma exchange around the time of an elective Caesarean section which provided temporary improvement in the platelet count and enabled safe delivery. This case highlights some of the challenges faced in the management of patients with severe and refractory immune thrombocytopenia during pregnancy.

Thrombopoietin: a potential diagnostic indicator of immune thrombocytopenia in pregnancy

To evaluate whether the serum thrombopoietin levels in pregnancy-associated immune thrombocytopenia (ITP) differ from those in gestational thrombocytopenia, and reveal the possibility of thrombopoietin serving as a marker for differential diagnosis. Serum thrombopoietin concentration was determined in ITP in pregnancy (n = 35), gestational thrombocytopenia (n = 31), healthy pregnancy (n = 32), age-matched nonpregnant ITP (n = 32) and nonpregnant healthy controls (n = 35) by ELISA. The serum thrombopoietin level of ITP in pregnancy (1283 ± 646 pg/mL) was significantly higher than gestational thrombocytopenia (187 ± 64 pg/mL) (P < 0.01), although the platelet counts of these two disorders may overlap. Twenty-nine of 35 patients with ITP in pregnancy had thrombopoietin values >500 pg/mL, whereas none of the gestational thrombocytopenia patients' thrombopoietin levels exceeded 500 pg/mL. In addition, ITP in pregnancy presented a markedly higher thrombopoietin level than nonpregnant ITP (88 ± 41 pg/mL) (P < 0.01), indicating that the pathogenesis of pregnant and nonpregnant ITP was different. Our findings suggest that measurement of serum thrombopoietin concentration provides valuable diagnostic information for differentiating ITP in pregnancy from gestational thrombocytopenia. Thrombopoietin represents a reliable marker for ITP in pregnancy.

Significance of the platelet distribution width as a severity marker for the development of preeclampsia

OBJECTIVE

To evaluate the platelet distribution width (PDW) and other platelet indices as potential severity markers of preeclampsia (PE).

STUDY DESIGN

A total of 935 pregnant women who had received continuous prenatal care and had undergone delivery were included. The participants were classified into 3 groups: healthy pregnant women (n=816), pregnant women with mild PE (n=59), and pregnant women with severe PE (n=60). Blood samples were collected during antenatal care or at the time of admission, and the platelet indices were compared among the three groups.

RESULTS

Among the three groups, the platelet count and plateletcrit decreased as the disease progressed. The mean platelet volume and the PDW, however, increased as the disease progressed. When compared to the levels of other platelet indices, the PDW showed significant elevation in the severe PE group. In the mild and severe PE groups, the PDW was statistically correlated with the mean arterial pressure (MAP) (r=0.231, p<0.05), whereas other platelet indices were not. In the receiver operating characteristics curve analysis, the area under the curve of the PDW to predict severe PE was 0.74.

CONCLUSIONS

Among platelet indices, the PDW is significantly higher in women with severe PE than in women with mild PE, and is positively correlated with the MAP. Therefore, the PDW can serve as a candidate marker for predicting the severity of PE.

Use of a thrombopoietin mimetic for chronic immune thrombocytopenic purpura in pregnancy

BACKGROUND

Romiplostim, a thrombopoietin mimetic, is a novel therapeutic option for patients with chronic immune thrombocytopenic purpura. We report on the effects of romiplostim use throughout pregnancy.

CASE

A 28-year-old primigravid woman with chronic immune thrombocytopenic purpura initiated a planned pregnancy on romiplostim. The second and third trimesters were marked by a cyclic pattern of thrombocytopenia requiring supplemental corticosteroids or intravenous immunoglobulin and resultant thrombocytosis. Increased romiplostim doses and daily corticosteroids stabilized the platelet count before induction of labor at 33 weeks of gestation. The newborn manifested intraventricular hemorrhage at birth, although no developmental delay was present on follow-up at 10 months of age.

CONCLUSION

The decreased efficacy of romiplostim monotherapy is attributed to increased target-mediated drug disposition and the physiologic changes of pregnancy. Safety concerns still exist for the developmental effects of romiplostim on the fetus.

Circulating levels of cytokines during pregnancy: thrombopoietin is elevated in miscarriage

OBJECTIVE

To evaluate the hypothesis that cytokine levels are associated with miscarriage risk using serum samples collected before report of miscarriage.

DESIGN

A nested case-control study.

SETTING

Biospecimens from the multisite Collaborative Perinatal Project, University of Florida, laboratory assessment of interleukin (IL)-1 receptor antagonist, IL-1beta, IL-4, IL-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, thrombopoietin (TPO), and granulocyte colony-stimulating factor (G-CSF).

PATIENT(S)

Cases of miscarriage (n = 439) were matched to controls (n = 373) by gestational age at sample collection.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Miscarriage.

RESULT(S)

Increased risk of miscarriage was associated with elevated TPO (adjusted odds ratio [OR] 1.16, 95% confidence interval [CI] 1.00-1.36) and decreased G-CSF (adjusted OR 0.78, 95% CI 0.64-0.95). When analysis was restricted to samples collected more than 35 days before miscarriage, the effect of G-CSF was not observed (adjusted OR 0.96, 95% CI 0.72-1.28), whereas increased risk related to higher TPO remained.

CONCLUSION(S)

Circulating levels of TPO may be associated with increased risk of miscarriage.

Prospective evaluation of platelet B2 bradykinin and thrombopoietin receptor levels from preeclamptic compared to non-preeclamptic pregnancy patients

Our recent study determined a difference between preeclamptic and non-preeclamptic patients in platelet potentiation by thrombopoietin (TPO) of reactivity to collagen. The main conclusion was that non-preeclamptic, but not preeclamptic, pregnancy patients' platelets showed significant TPO potentiation at first and third trimesters. Since TPO or B2 Bradykinin platelet receptor levels might influence TPO potentiation, we obtained platelet samples from 187 first trimester pregnant patients prospectively followed through pregnancy. Patients were additionally sampled at third trimester, delivery, and 4 to 6 weeks postpartum. A total of 43 patients, including 11 diagnosed as preeclamptic at third trimester, were sampled at least three different times. We used Western blotting normalized with glyceraldehyde 3 phosphate dehydrogenase as a loading and staining control. There were no significant differences in relative receptor levels between groups or sampling times using repeated measures ANOVA with the mixed model allowing for missing samples. While the mechanism for differences in thrombopoietin potentiation of platelet activation by collagen remains unknown, it may be a first trimester indicator of developing preeclampsia.

Lack of thrombopoietin potentiation of platelet collagen activation in the first trimester is associated with preeclampsia

To determine whether a difference exists in platelet reactivity to collagen and potentiation by thrombopoietin (TPO) between preeclamptic and non-preeclamptic patients, 187 first trimester pregnant patients were prospectively followed through pregnancy. Citrated blood, drawn at first (<14 weeks estimated gestational age) and third trimesters (>28 weeks), when patients were admitted for delivery, and 4-6 weeks postpartum, was assayed by a Whole Blood Impedance Aggregometer measuring platelet activation by 0.4 mug/ml collagen, +/-10 ng/ml TPO. There was no significant difference in 1st trimester platelet collagen activation by unpaired t-test between groups. Significant TPO potentiation of collagen activation (P<0.05, paired t-test) was observed in non-preeclamptic patients at the first and third trimesters. In contrast, preeclamptic patients' platelets show no significant (P>0.8, paired t-test) TPO potentiation at any time. While the mechanism for this difference in thrombopoietin potentiation of platelet activation by collagen as early as the first trimester is unknown, it may be one of the initiating events in this syndrome.

Soluble P-selectin levels during normal pregnancy: a longitudinal study

OBJECTIVE

To investigate soluble P-selectin (sP-selectin) levels and platelet parameters in normal pregnant women compared with non-pregnant control subjects.

DESIGN

A longitudinal case-control study.

SETTING

Obstetric outpatient clinic in the Jubilee Maternity Hospital, Belfast.

POPULATION

One hundred and twenty normal pregnant women and 41 non-pregnant age-matched control subjects.

METHODS

The plasma concentration of sP-selectin in pregnant women sampled at 12, 20 and 35 weeks of gestation, and, in a subgroup at three days postpartum, and non-pregnant controls sampled in parallel, was determined using a commercial quantitative sandwich immunoassay kit. Platelet parameters on each blood sample were also recorded using a SYSMEX SE 9500 analyser.

MAIN OUTCOME MEASURES

Plasma sP-selectin as a measure of platelet activation in normal pregnancy.

RESULTS

Soluble P-selectin was significantly higher in pregnant women than in non-pregnant control subjects at 20 and 35 weeks of gestation, (P < 0.01, and P < 0.001, respectively). Correlation analyses showed positive correlation between sP-selectin and platelet count in pregnant women at 20 and 35 weeks of gestation (r = 0.247, P < 0.05 and r = 0.360, P < 0.001, respectively). Soluble P-selectin concentration per platelet was also significantly higher in pregnant women than in non-pregnant control subjects at 20 and 35 weeks of gestation (P < 0.001).

CONCLUSIONS

Our results show that sP-selectin concentration is significantly higher in the second and third trimester of pregnancy when compared with non-pregnant control subjects sampled in parallel. This finding clarifies previous conflicting results on platelet activation in normal pregnancy, and is in agreement with those earlier studies which reported, using other methods, increased platelet activation in normal pregnancy.

Cesarean section combined with splenectomy in a parturient with immune thrombocytopenic purpura

The case of a 25-year-old parturient with immune thrombocytopenic purpura is discussed. The patient was first seen at 20 weeks' gestation because of a history of thrombocytopenia after delivery of a child six years previously. The patient was not compliant with prednisone therapy or return follow-up visits; a combined cesarean section with splenectomy was planned for this patient. The report discusses the multidisciplinary management of this patient during her pregnancy and delivery.