Functional analyses of placental protein 13/galectin-13

Governing the invasive trophoblast: current aspects on intra- and extracellular regulation

This review summarizes several aspects especially of regulating factors governing trophoblast invasion. Those include the composition of the extracellular matrix containing a variety of matrix metalloproeinases and their inhibitors, but also intracellular signals. Furthermore, a newly described trophoblast subtype, the endoglandular trophoblast, is presented. Its presence may provide a possible mechanism for opening and connecting uterine glands into the intervillous space. Amongst others, two intracellular signalling pathways are crucial for regulation of trophoblast functions and development: Wnt- and signal transducer and activator of transcription (STAT)3 signalling. Wnt signalling promotes implantation, placentation and trophoblast differentiation. Several Wnt-dependent cascades and regulatory mechanisms display different functions in trophoblast cells. The STAT3 signalling system is fundamental for induction and regulation of invasiveness in physiological trophoblastic cells, but also in tumours. The role of galectins (Gal) in trophoblast regulation and placenta development comes increasingly into focus. The Gal- 1-4, 7-10 and 12-14 have been detected in humans. Detailed information is only available for Gal-1, -2, -3, -4, -9 and -12 in endometrium and decidua. Gal-1, -3 and -13 (-14) have been detected and studied in trophoblast cells.

Placental protein 13 as a first trimester screening marker for aneuploidy

OBJECTIVE

To determine whether Placental Protein 13 (PP13) could be an additional marker in first trimester screening for aneuploidies.

METHODS

To evaluate differences in multiples of the gestation-specific normal median (MoMs), PP13 concentrations were measured in serum samples from Down syndrome, trisomy 18 and 13 affected pregnancies and euploid singleton pregnancies (four for each case matched for duration of storage, maternal weight and age).

RESULTS

The PP13 MoM in Down syndrome cases (n = 153) was 0.91 [not statistically significant from controls (n = 853); P = 0.06; Wilcoxon rank sum test, two-tail]. PP13 MoMs were decreased in trisomy 18 (n = 38-median MoM 0.64; P < 0.0001) and trisomy 13 cases (n = 23-median MoM 0.46; P < 0.0001). There was a slight upward trend in MoM values of the Down syndrome cases with gestational weeks. The PP13 MoM was significantly correlated with the pregnancy associated plasma protein-A MoM and the free beta-subunit of human chorion gonadotrophin (fbeta-hCG) MoM.

CONCLUSION

PP13 does not seem to be a good marker for Down syndrome. PP13 MoMs are, however, significantly lower in trisomy 18 and 13 pregnancies. The addition of PP13 to the current screening test could be valuable for improving the discrimination of aneuploid from euploid pregnancies.

PP13 mRNA expression in the cellular component of maternal blood as a marker for preeclampsia

OBJECTIVE

To assess the PP13 expression in the cellular component of blood in both preeclamptic patients and asymptomatic pregnant women during the early second trimester.

METHODS

In the case-control study, peripheral blood samples were obtained from pregnant women with preeclampsia (n = 24) and controls (n = 22). PP13 RNA expression was quantified in the cellular component of the blood by reverse transcription PCR assay. Next, as a cohort study of asymptomatic pregnant women at early gestation, cellular RNA from 41 cases who developed preeclampsia at later gestation and 123 cases of control were analysed, and the possibility of prediction of preeclampsia was assessed.

RESULTS

In symptomatic patients, PP13 level in preeclampsia was significantly lower than that in controls (p < 0.001). In the asymptomatic pregnant women, the PP13 level in preeclampsia was significantly lower than that in the controls (p = 0.008). A receiver-operating characteristics (ROC) curve yielded a detection rate of 24 and 31% at a false positive rate of 5 and 10% respectively.

CONCLUSION

An alteration in the cellular PP13 RNA expression would affect the placental pathophysiological change. The cellular PP13 expression level could therefore potentially be one of the key markers to predict the clinical onset of preeclampsia.

Maternal serum placental protein 13 at 11-13 weeks of gestation in preeclampsia

OBJECTIVE

To examine the potential value of maternal serum concentration of placental protein 13 (PP13) at 11-13 weeks' gestation in screening for preeclampsia (PE).

METHODS

Serum PP13, PAPP-A and uterine artery pulsatility index (PI) were determined in a case-control study of 208 cases that developed PE including 48 that required delivery before 34 weeks (early-PE) and 416 unaffected controls.

RESULTS

Serum PP13 levels, expressed as multiples of the median (MoM) in the unaffected group, were significantly reduced in early-PE (0.83 MoM) but not in late-PE (0.96 MoM). In both early- and late-PE serum PAPP-A (0.55 and 0.84 MoM) was reduced and uterine artery PI (1.61 and 1.25 MoM) was increased. In PE pregnancies there was a significant association between serum PP13 and both uterine artery PI and serum PAPP-A (p < 0.0001 for both). Logistic regression analysis demonstrated that serum PP13 did not improve significantly the prediction of early-PE provided by a combination of maternal factors, uterine artery PI and PAPP-A.

CONCLUSION

PP13 is implicated in the pathogenesis of impaired placentation and subsequent development of early-PE but measurement of this placental product is unlikely to be useful in screening for the disease at 11-13 weeks.

First trimester maternal serum placental protein 13 for the prediction of pre-eclampsia in women with a priori high risk

OBJECTIVE

To evaluate whether first trimester maternal serum PP13 can predict pre-eclampsia among women with a priori high risk.

METHOD

This was a nested case-control study. Women less than 14 weeks' gestation at increased risk of developing pre-eclampsia were recruited. Venous blood samples were assayed for PP13 using enzyme-linked immunosorbent assay. PP13 multiples of median (MoM) were calculated and adjusted for body mass index, ethnicity, smoking, maternal age and parity. For each case of pre-eclampsia (n = 42), five controls were randomly selected. PP13 levels were compared between women who developed pre-eclampsia and controls using the Wilcoxon rank sum test. Sensitivity and false-positive rates were derived from receiver operating characteristic curves.

RESULTS

Women who developed pre-eclampsia had significantly lower (P < 0.001) PP13 MoMs compared with controls. PP13 MoMs for controls and pre-eclampsia cases were 1.0 (range 0.0-10.0) and 0.4 (range 0.0-7.0), respectively (P < 0.001). At a MoM cutoff of 0.53, for a false-positive rate of 10%, sensitivity was 50% for pre-eclampsia at term (>37 weeks), 62% for preterm pre-eclampsia (<37 weeks) and 71% for early-onset pre-eclampsia (<34 weeks).

CONCLUSION

First trimester PP13 can predict pre-eclampsia in women at increased a priori risk and predicts early-onset better than late-onset disease.

A novel exonic variant (221delT) in the LGALS13 gene encoding placental protein 13 (PP13) is associated with preterm labour in a low risk population

Predicting adverse pregnancy outcome in low risk patients in a community with poor socio-economic circumstances is difficult, yet about 5% of these pregnancies will result in preterm labour or severe pre-eclampsia. In this study we aimed to identify markers in pro- and anti-inflammatory genes that may contribute to disease and possibly disease prediction in a low risk community setting. A prospective study was undertaken on 450 consecutive low risk primigravid patients. Blood obtained at first booking was screened for known immunological gene variants (IL4 -590, IL1B +3953, IL1RN, IL10 -1082; -819; -592 and TNFA -308; -238; +488) as well as for novel variants in the LGALS13 gene coding for placental protein 13 (PP13). The incidence of preterm labour and pre-eclampsia was 7.1% and 6.8% respectively. A novel exonic variant (221delT) in the LGALS13 gene increased the risk for preterm labour in the total study group (relative risk RR 2.27). Maternal carriage of the interleukin-1 RN*2 allele was associated with an increased risk of hypertension in pregnancy in the Coloured subgroup of the study cohort (RR 2.53). There was an increased risk for preterm labour in the same subgroup with carriage of the TNFA -308 A-allele (TNF2) (RR 2.53). No significance was found for the other variants examined. We conclude that single nucleotide polymorphisms (SNPs) in certain genes regulating implantation and inflammation may contribute to the complex etiology of pre-eclampsia and preterm labour. The association between the 221delT deletion and adverse pregnancy outcome needs to be confirmed in different populations.

Potential markers of preeclampsia--a review

Preeclampsia is a leading cause of maternal and fetal/neonatal mortality and morbidity worldwide. The early identification of patients with an increased risk for preeclampsia is therefore one of the most important goals in obstetrics. The availability of highly sensitive and specific physiologic and biochemical markers would allow not only the detection of patients at risk but also permit a close surveillance, an exact diagnosis, timely intervention (e.g. lung maturation), as well as simplified recruitment for future studies looking at therapeutic medications and additional prospective markers. Today, several markers may offer the potential to be used, most likely in a combinatory analysis, as predictors or diagnostic tools. We present here the current knowledge on the biology of preeclampsia and review several biochemical markers which may be used to monitor preeclampsia in a future, that, we hope, is not to distant from today.

A primate subfamily of galectins expressed at the maternal-fetal interface that promote immune cell death

Galectins are proteins that regulate immune responses through the recognition of cell-surface glycans. We present evidence that 16 human galectin genes are expressed at the maternal-fetal interface and demonstrate that a cluster of 5 galectin genes on human chromosome 19 emerged during primate evolution as a result of duplication and rearrangement of genes and pseudogenes via a birth and death process primarily mediated by transposable long interspersed nuclear elements (LINEs). Genes in the cluster are found only in anthropoids, a group of primate species that differ from their strepsirrhine counterparts by having relatively large brains and long gestations. Three of the human cluster genes (LGALS13, -14, and -16) were found to be placenta-specific. Homology modeling revealed conserved three-dimensional structures of galectins in the human cluster; however, analyses of 24 newly derived and 69 publicly available sequences in 10 anthropoid species indicate functional diversification by evidence of positive selection and amino acid replacements in carbohydrate-recognition domains. Moreover, we demonstrate altered sugar-binding capacities of 6 recombinant galectins in the cluster. We show that human placenta-specific galectins are predominantly expressed by the syncytiotrophoblast, a primary site of metabolic exchange where, early during pregnancy, the fetus comes in contact with immune cells circulating in maternal blood. Because ex vivo functional assays demonstrate that placenta-specific galectins induce the apoptosis of T lymphocytes, we propose that these galectins reduce the danger of maternal immune attacks on the fetal semiallograft, presumably conferring additional immune tolerance mechanisms and in turn sustaining hemochorial placentation during the long gestation of anthropoid primates.

PP13 mRNA expression in trophoblasts from preeclamptic placentas

To assess the role of placental protein 13 (PP13) in the pathogenesis of preeclampsia, the messenger RNA expression of PP13 was investigated in the trophoblasts from first and third trimester placenta. First, syncytiotrophoblasts and extravillous trophoblasts were separated from frozen section of third trimester placenta obtained from pregnant women with and without preeclampsia by laser microdissection. The PP13 levels of syncytiotrophoblasts were significantly higher than those of extravillous trophoblasts. The expression levels in syncytiotrophoblasts from the preeclampsia were significantly lower than those from normal. Next, the PP13 expression was assessed in trophoblasts from residual samples of chorionic villus sampling at 11 weeks of gestation, who subsequently developed preeclampsia. The levels in the preeclampsia group were significantly lower than those of normal cases. These findings indicate that an alteration in the PP13-messenger RNA expression in the trophoblasts may be associated with the pathogenesis of preeclampsia.

Factors involved in regulating trophoblast fusion: potential role in the development of preeclampsia

In the human placenta, turnover of villous trophoblast involves proliferation, differentiation and fusion of mononucleated cytotrophoblasts with the overlying syncytiotrophoblast. In this way the syncytiotrophoblast is continuously supplied with compounds derived from the fusing cytotrophoblasts. Acquisition of fresh cellular components is balanced by a concomitant release of apoptotic material as syncytial knots from the syncytiotrophoblast to the maternal circulation. In the turnover of villous trophoblast, fusion is an essential step and has been shown to be regulated by multiple factors, such as cytokines, hormones, protein kinases, transcription factors, proteases and membrane proteins. Dysregulation of one or more of these fusion factors entails aberrant fusion of the cytotrophoblast with the syncytiotrophoblast, which adversely affects the maintenance and integrity of the placental barrier. Unbalanced trophoblast fusion and release of apoptotic material into the intervillous space may provoke a massive systemic inflammatory response by the mother and thus lead to preeclampsia.

T cell apoptosis at the maternal-fetal interface in early human pregnancy, involvement of galectin-1

The human fetus is not rejected by the maternal immune system despite expressing paternal antigens. Natural killer cells, the major lymphocyte population of the human decidua (dNKs), express genes with immunomodulatory potential. These include galectin-1 (gal1), a lectin with apoptotic activity on activated CD8(+) T cells, Th1 and Th17 CD4(+) cells. Although many cell types at the maternal-fetal interface also produce gal1, its production by dNKs has been used here to study its function in pregnancy. Media conditioned by dNKs containing gal1 induced apoptosis of activated T cells. This effect was blocked by anti-gal1 antibodies. Decidual T (dT) cells but not peripheral T (pT) cells bound gal1 and presented a distinct glycophenotype compatible with sensitivity to gal1. Annexin V staining, TUNEL, and hypodiploidy showed a substantial proportion of apoptotic dT cells. Immunohistochemistry revealed widespread expression of gal1 as well as periglandular apoptotic dT foci that colocalized with dNKs. Thus, secretion of gal1 by dNKs and other decidual cells contributes to the generation of an immune-privileged environment at the maternal-fetal interface.

Placental protein 13 (galectin-13) has decreased placental expression but increased shedding and maternal serum concentrations in patients presenting with preterm pre-eclampsia and HELLP syndrome

Placental protein 13 (PP13) is a galectin expressed by the syncytiotrophoblast. Women who subsequently develop preterm pre-eclampsia have low first trimester maternal serum PP13 concentrations. This study revealed that third trimester maternal serum PP13 concentration increased with gestational age in normal pregnancies (p < 0.0001), and it was significantly higher in women presenting with preterm pre-eclampsia (p = 0.02) and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome (p = 0.01) than in preterm controls. Conversely, placental PP13 mRNA (p = 0.03) and protein, as well as cytoplasmic PP13 staining of the syncytiotrophoblast (p < 0.05) was decreased in these pathological pregnancies compared to controls. No differences in placental expression and serum concentrations of PP13 were found at term between patients with pre-eclampsia and control women. In contrast, the immunoreactivity of the syncytiotrophoblast microvillous membrane was stronger in both term and preterm pre-eclampsia and HELLP syndrome than in controls. Moreover, large syncytial cytoplasm protrusions, membrane blebs and shed microparticles strongly stained for PP13 in pre-eclampsia and HELLP syndrome. In conclusion, parallel to its decreased placental expression, an augmented membrane shedding of PP13 contributes to the increased third trimester maternal serum PP13 concentrations in women with preterm pre-eclampsia and HELLP syndrome.

First-trimester maternal serum PP13 in the risk assessment for preeclampsia

OBJECTIVE

The objective of the study was to determine whether first-trimester maternal serum placental protein 13 (PP13) concentrations can be used in the risk assessment for preeclampsia.

STUDY DESIGN

This case-control study included 50 patients with preeclampsia and 250 patients with normal pregnancies. Samples were collected between 8 and 13 weeks of gestation. Serum PP13 concentrations were measured by immunoassay and expressed as medians and multiples of the median (MoM) for gestational age. Sensitivity and specificity were derived from receiver-operating characteristic curve analysis.

RESULTS

(1) Serum PP13 concentration in the first trimester was significantly lower in patients who developed preterm and early-onset preeclampsia than in those with normal pregnancies; and (2) at 80% specificity, a cutoff of 0.39 MoM had a sensitivity of 100% for early-onset preeclampsia and 85% for preterm preeclampsia.

CONCLUSION

Maternal serum first-trimester PP13 appears to be a reasonable marker for risk assessment for preterm preeclampsia but a weak marker for severe preeclampsia at term, and ineffective for identifying mild preeclampsia at term.

First-trimester placental protein 13 screening for preeclampsia and intrauterine growth restriction

OBJECTIVE

The purpose of this study was to evaluate first-trimester serum placental protein 13 (PP13) as a screening test for preeclampsia and intrauterine growth restriction (IUGR).

STUDY DESIGN

We performed a prospective, nested case-control study in the Massachusetts General Hospital Obstetric Maternal Study. PP13 was measured by solid-phase sandwich enzyme-linked immunosorbent assay in serum samples that were collected at the first prenatal visit (9-12 weeks of gestation) from women who subsequently experienced preeclampsia (n = 47), IUGR (n = 42), or preterm delivery (n = 46). Women with uncomplicated term deliveries served as control subjects (n = 290) and were matched to cases by gestational age when serum was collected and for the duration of specimen storage.

RESULTS

The median first-trimester PP13 level was 132.5 pg/mL in the control subjects. Median PP13 levels were significantly lower among women who had preeclampsia (27.2 pg/mL; P < .001), IUGR (86.6 pg/mL; P < .001), and preterm delivery (84.9 pg/mL; P = .007). When PP13 was expressed as multiples of the gestational age-specific medians among the control subjects, the multiples of the medians were 0.2 for preeclampsia, 0.6 for IUGR, and 0.6 for preterm delivery (P < .001 for each disorder compared with control subjects). Receiver operating characteristic analysis yielded areas under the curve of 0.91, 0.65, and 0.60 for preeclampsia, IUGR, and preterm delivery, respectively. At a 90% specificity rate, the corresponding sensitivities were 79%, 33%, and 28%, respectively.

CONCLUSION

The screening of maternal PP13 levels in the first trimester is a promising diagnostic tool for the prediction of preeclampsia with high sensitivity and specificity.

Second-trimester uterine artery Doppler pulsatility index and maternal serum PP13 as markers of pre-eclampsia

OBJECTIVE

To evaluate whether measurement of maternal serum PP13 at 22 to 24 weeks of gestation, alone or in combination with second-trimester biochemical markers or uterine artery pulsatility measured by Doppler velocimetry, is useful in predicting those women at risk of developing pre-eclampsia.

STUDY DESIGN

A nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. PP13 was tested by an ELISA, with the samples blinded to pregnancy outcome. All patients also underwent uterine artery Doppler flow velocimetry at 22-24 weeks to measure the mean pulsatility index (PI). Results for Inhibin, Activin, PAPP-A and Free beta-hCG were available from previous studies.

RESULTS

There were 73 controls and five cases with early pre-eclampsia in which delivery was induced prior to 35 weeks. In addition, there were a further seven cases with pre-eclampsia in which delivery was not induced before term. Median PP13 levels for controls and all cases were 295.9 and 212.6 pg/ml, and 171.2 pg/ml amongst the early pre-eclampsia cases, with the MoMs 1.00, 0.94 and 0.63, respectively (p < 0.001). Receiver operator characteristic (ROC) curve analysis for either all cases or early cases versus controls yielded areas under the curve of 0.588 (95% CI: 0.42-0.76; p = 0.1526) and 0.693 (0.47-0.92; p = 0.0441) for PP13. At a specificity set to 0.80, the sensitivity for PP13 in the early cases was 0.40 and that in all cases was 0.25. Combining PP13 bivariately with any of the markers (PI, PAPP-A, Activin, Inhibin or Free beta-hCG) tested in the 22-24 week period did not improve the detection of early, late or all cases of pre-eclampsia compared with either marker alone.

CONCLUSION

Late second-trimester PP13 alone is unlikely to be useful in predicting pre-eclampsia and early pre-eclampsia, and its prediction does not increase when coupled with second-trimester Doppler PI or other potential biochemical markers. Measuring between-trimester temporal changes may be worthy of further investigation.

First-trimester maternal serum PP-13, PAPP-A and second-trimester uterine artery Doppler pulsatility index as markers of pre-eclampsia

OBJECTIVE

To evaluate whether measurement of maternal serum placental protein-13 (PP-13) and pregnancy-associated plasma protein-A (PAPP-A) at 11 + 0 to 13 + 6 weeks of gestation alone or in combination with second-trimester uterine artery pulsitility measured by Doppler velocimetry is useful in predicting those women who will develop pre-eclampsia

METHODS

This was a nested case-control study of pre-eclampsia cases with controls matched for gestational age and storage time for the maternal serum. Samples were collected as part of a first-trimester prenatal chromosomal anomaly screening program and were routinely tested for PAPP-A. PP-13 was tested using an enzyme linked immunosorbent assay (ELISA) by an examiner who was blinded to pregnancy outcome. All patients also underwent uterine artery Doppler flow velocimetry to measure the mean pulsatility index (PI) at 22-24 weeks' gestation.

RESULTS

There were 446 controls and 44 cases with early pre-eclampsia where delivery was induced prior to 35 weeks. In addition there were a further 44 cases with pre-eclampsia in which delivery was not induced before term. Median PP-13 levels for controls, all cases and early pre-eclampsia cases were 176.9, 121.9 and 111.7 pg/mL, with multiples of the median (MoMs) of 1.00, 0.69 and 0.63, respectively (P < 0.001). PAPP-A MoMs were 1.00, 0.89 (P = 0.076) and 0.89 (P = 0.042) and mean PIs were 1.0, 1.6 (P < 0.001) and 1.7 (P < 0.001) for controls, all cases and early cases, respectively. Receiver-operating characteristics (ROC) curve analysis for either all cases or early cases vs. controls yielded areas under the curve for PP-13, PAPP-A and PI respectively of 0.68 (95% CI, 0.61-0.74; P < 0.001), 0.56 (95% CI, 0.49-0.63; P = 0.076) and 0.79 (95% CI, 0.72-0.87; P < 0.001) for all cases and 0.71 (95% CI, 0.63-0.79; P < 0.001), 0.59 (95% CI, 0.51-0.68; P = 0.076) and 0.86 (95% CI, 0.77-0.94; P < 0.001) for early cases. At a specificity set to 0.80 the sensitivities were 0.50, 0.23 and 0.76 for PP-13, PAPP-A and PI in the early cases and 0.44, 0.24 and 0.73 in all cases. Combining PP-13 and PI using logistic regression analysis yielded an area under the curve of 0.84 (95% CI, 0.78-0.90; P < 0.001) and a sensitivity of 0.74 in all cases, and 0.90 (95% CI, 0.84-0.96; P < 0.001) and a sensitivity of 0.79 for early cases. PAPP-A with PI gave an area under the curve of 0.82 (95% CI, 0.76-0.90; P < 0.001) and a sensitivity of 0.76 in all cases. Combining PAPP-A with PP-13 and PI did not add significantly to the sensitivity.

CONCLUSION

First-trimester PP-13 levels may be useful in predicting pre-eclampsia and early pre-eclampsia, and the accuracy of the method increases when coupled with second-trimester Doppler PI measurement. First-trimester PAPP-A provides some prediction for pre-eclamspia when combined with PI but does not add to the prediction of early pre-eclampsia when PP-13 and PI are used together. Further studies are required to establish the real value of PP-13 in first-trimester screening for pre-eclampsia.

A novel approach to first-trimester screening for early pre-eclampsia combining serum PP-13 and Doppler ultrasound

OBJECTIVE

To investigate the value of maternal serum placental protein 13 (PP-13) measurement and uterine artery Doppler during first-trimester screening in the prediction of early pre-eclampsia.

METHODS

This was a nested case-control prospective study of pregnancies at 11 + 0 to 13 + 6 weeks of gestation. The pulsatility index (PI) of blood flow in the uterine arteries and the maternal serum concentration of PP-13 were measured in 10 women who went on to develop pre-eclampsia that necessitated delivery before 34 weeks, and in 423 unaffected women. Results were expressed as multiples of the gestation-specific median in controls (MoM). A logistic regression model was used to predict detection and false-positive rates.

RESULTS

In the cases that developed pre-eclampsia requiring delivery before 34 weeks, compared with the unaffected pregnancies, the median uterine artery PI was higher (1.43 MoM) and the median serum PP-13 level was lower (0.07 MoM; P < 0.001, Wilcoxon rank sum test for both). Modeling predicted that for a 90% detection rate of pre-eclampsia requiring delivery before 34 weeks, the false-positive rate of screening by PP-13 was 12%, by uterine artery PI was 31% and by a combination of the two methods was 9%. A policy of contingency screening, whereby all women are screened by maternal serum PP-13 and only the 14% at highest risk are then screened by Doppler, achieved a detection rate of 90% with an overall false-positive rate of 6%.

CONCLUSION

Effective screening for pre-eclampsia requiring delivery before 34 weeks can potentially be provided by assessment of a combination of maternal serum PP-13 and uterine artery Doppler in the first trimester of pregnancy.

Placental protein 13 (PP-13): effects on cultured trophoblasts, and its detection in human body fluids in normal and pathological pregnancies

Placental tissue protein 13 (PP-13), one of the 56 known placental proteins identified till today, was purified from placentas obtained from women at delivery, and used to evoke antibodies against it. The purified PP-13 was lysed to peptides, which were sequenced, leading to the full-length cDNA sequencing and its expression in Escherichia coli. Sequence analysis in databases showed homology to the galectin family. Of the various antibody preparations developed, a pair of monoclonal antibodies (MAbs) coupled to the recombinant PP-13 (PP-13-R) was used for the immunodetection of PP-13 in pregnant women's serum with the solid-phase ELISA format. With a dynamic range of 25-500 pg/mL with no background in non-pregnant women's serum and men's serum, the ELISA test was suitable for the detection of PP-13 in the 1st, 2nd, and 3rd trimesters. PP-13 levels slowly increase during pregnancy. In the 1st trimester, lower than normal PP-13 levels were found in fetal growth restriction (IUGR), preeclampsia (PE), and particularly in early PE (<34 weeks of gestation). In the 2nd and 3rd trimesters, higher than normal concentrations were found in PE, IUGR and in preterm delivery (PTD). Application of PP-13 to cultured trophoblasts elicited depolarization carried by calcium ions, followed by liberation of linoleic and arachidonic acids from the trophoblast membrane, and a subsequent elevation of prostacyclin and thromboxane. These effects were negligible when PP-13 derived from the placentas of patients with IUGR, PE or PTD was used. The results are discussed in view of the potential utilization of PP-13 for early serum screening to assess the risk to develop placental insufficiency, coupled to a differential analysis of the various pathologies by analyzing cultured trophoblasts.