Ontogeny of hepatocyte growth factor (HGF) and its receptor (c-met) in human placenta: reduced HGF expression in intrauterine growth restriction.

Severe intrauterine growth restriction (IUGR) is characterized by abnormal placentation. Mouse gene knockout studies show that an absence of either hepatocyte growth factor (HGF) or its receptor, c-met, leads to intrauterine death secondary to severe IUGR with deficient placentation. In this study, immunocytochemistry localized HGF protein throughout placental villi across gestation, whereas c-met protein was localized only to the perivillous trophoblast and vascular endothelium. Within the IUGR placentae, a reduction in HGF immunostaining within the villous stroma was observed. HGF mRNA was strongly expressed in the perivascular tissue around the stem villous arteries throughout gestation, with weaker expression within the villous stroma and the terminal villi. c-met mRNA expression was limited to the perivillous trophoblast, particularly in the first trimester, with only a faint hybridization signal from the villous stroma. Placental mRNA expression was examined quantitatively using a ribonuclease protection assay: HGF and c-met mRNA expression increased from the first to the second trimester, reaching a zenith before decreasing again through the third trimester to term. HGF mRNA levels were significantly reduced in the IUGR placentae (P = 0.036), whereas c-met mRNA expression was within the normal range for gestation. These findings suggest that HGF derived from the perivascular tissue of stem villous arteries may play an important role in controlling normal villous development. Whereas reduced expression of HGF within IUGR placentae does not prove a causative link with abnormal villous development, the association lends support to this possibility.

Localization, quantification, and activation of platelet-activating factor receptor in human endometrium during the menstrual cycle: PAF stimulates NO, VEGF, and FAKpp125.

Implantation is characterized by an inflammatory-like response with expansion of extracellular fluid volume, increased vascular permeability, and vasodilatation. These effects are believed to be mediated at the paracrine level by prostaglandin E2 and platelet-activating factor (PAF), but the cellular mechanism (or mechanisms) remains largely unknown. We demonstrate that PAF receptor (PAF-R) immunoreactivity and mRNA are detected in proliferative and secretory endometrial glands, however, the responsiveness of endometrium to physiological concentrations of PAF is confined predominantly to the secretory endometrium. Semiquantitative reverse transcription-polymerase chain reaction revealed that PAF-R transcript levels were highest in the mid-late proliferative and late secretory phases of the cycle. Interaction of PAF with its receptor resulted in the rapid release of nitric oxide (NO), increased expression of vascular endothelial growth factor (VEGF), and activation of FAKpp125, a focal adhesion kinase, demonstrating that the PAF-R is functionally active. Inhibition of NO synthesis by NG-monomethyl-L-arginine produced dose-dependent attenuation of PAF-evoked NO release, indicating NOS activation; the dependency of PAF-evoked NO release on PKC and extracellular Ca2+ was confirmed by PKC inhibitor Ro 31-8220 and by the removal of extracellular Ca2+. PAF up-regulated VEGF gene expression in a concentration- and time-dependent fashion in human endometrial epithelial cell lysates. Transcription of VEGF was rapidly followed by secretion of the protein. These data support our premise that this autocoid acts as an angiogenic mediator in the regeneration of the endometrium after menses and as a vasodilator to promote blastocyst attachment during the implantation process.

Fibroblast growth factor receptor-1 is a critical component for endometrial remodeling: localization and expression of basic fibroblast growth factor and FGF-R1 in human endometrium during the menstrual cycle and decreased FGF-R1 expression in menorrhagia.

Angiogenic growth factors play a critical role in the cyclic growth and vascularization of normal endometrium. Herein, we report the expression and localization of both basic fibroblast growth factor (FGF-2) and its receptor (FGF-R1; flg) in human endometrium and demonstrate the markedly decreased FGF-R1 levels in menorrhagia. In situ hybridization using [35S]-labeled riboprobe demonstrated distinct autoradiographic signals for FGF-2 mRNA in glandular epithelial and stromal cells in endometrium throughout the menstrual cycle, with the strongest hybridization signal in stromal cells of the proliferative endometrium relative to that of the secretory endometrium. Moreover, RNAse protection assay revealed that the mRNA encoding FGF-2 and FGF-R1 was significantly higher in proliferative than in secretory endometrium (p < 0.05, p < 0.01). Immunohistochemistry using anti-flg antibody showed that the intensity of FGF-R1 staining was markedly diminished in the stromal cells of secretory endometrium, which corresponded with the reduced FGF-2 mRNA expression. In contrast, the endometrial glandular epithelial cells showed intense localization of FGF-R1 protein throughout the menstrual cycle, which paralleled FGF-2 mRNA expression. Colocalization of FGF-2 and FGF-R1 in stroma and stimulation of DNA synthesis and phospholipase C activation by FGF-2 in these cells demonstrates that FGF-2 acts in an autocrine manner in endometrial stroma. Western immunoblotting showed that FGF-R1 immunoprotein was markedly reduced or absent in women with menorrhagia throughout the cycle relative to that of normal cycling women, suggesting that FGF-R1 is critical for endometrial "maturation" and regeneration of the normal endometrium following menstruation.

Immunoreactive 15-hydroxyprostaglandin dehydrogenase (PGDH) is reduced in fetal membranes from patients at preterm delivery in the presence of infection.

Previously we reported that the proportion of trophoblast cells that were immunopositive for 15-OH prostaglandin dehydrogenase (PGDH) in the chorionic membranes was reduced in women in preterm labour without infection, compared with women at term, but was not altered in preterm labour patients with an underlying infective process. Subsequently, we found that PGDH activity and PGDH mRNA were significantly lower in membranes of this latter group of patients than in women at preterm labour without infection or at term. To resolve this issue we used immunohistochemistry to examine the distribution and frequency of immunoreactive (ir)-PGDH positive cells in full-thickness fetal membranes in patients at preterm labour in the presence or absence of infection. Trophoblast and decidual stromal cells were identified using antibodies against cytokeratin and vimentin, respectively. There was considerable variation in the number of chorionic trophoblast cells that were positive for ir-PGDH, but in some patients there was little or no ir-PGDH staining, and this was associated with loss of trophoblast cells from the tissue. The mean intensity and number of ir-PGDH positive cells was significantly lower in membranes from patients in preterm labour with infection than in idiopathic preterm labour at which the diagnosis of infection was not made. We conclude that in the setting of preterm labour with infection there may be loss of trophoblast cells from membranes, with corresponding reduction in the number of ir-PGDH positive cells. Loss of PGDH activity removes the initial step in activating primary prostaglandins, which are then able to pass unmetabolized to the decidua and myometrium, and contribute to the stimulus to preterm birth.

Immunohistochemical localization, messenger ribonucleic acid abundance, and activity of 15-hydroxyprostaglandin dehydrogenase in placenta and fetal membranes during term and preterm labor.

Type 1 15-hydroxyprostaglandin dehydrogenase (PGDH) is the main enzyme responsible for the metabolism of prostaglandin E2 (PGE2) and PGF2 alpha. To examine the possibility that a deficiency of PGDH might contribute to preterm labor, we measured localization of immunoreactive (IR-) PGDH, PGDH mRNA, and PGDH enzyme activity in chorio-decidua, placenta, and amnion in patients after term elective cesarean section (n = 9), after spontaneous vaginal term delivery (n = 10), and at idiopathic preterm labor (PTL) in the absence of infection (< 36 weeks gestation; n = 11). Localization of IR-PGDH was determined in additional specimens of membranes after PTL with infection (n = 13) and without (n = 37). IR-PGDH was localized in syncytiotrophoblast and intermediate trophoblasts in placenta and in the trophoblast layer of extraplacental chorion, but was absent from amnion in all patient groups. In chorion, the number of IR-positive trophoblasts was significantly reduced in the idiopathic PTL group compared to those in the other groups. The relative abundance of PGDH mRNA in the chorio-decidua, but not the placenta, from spontaneous labor and PTL was significantly less than that after cesarean section. PGDH mRNA in chorio-decidua from preterm patients correlated with PGDH enzyme activity. Undetectable or low IR-PGDH in chorionic trophoblasts was also associated with low enzyme activity. These results suggest that there exists a subset of patients that present in PTL because of reduced PGDH expression in chorionic trophoblasts. We suggest that this relative deficiency would allow PGs synthesized in the amnion or chorion to escape metabolism in the chorion and thereby contribute to the stimulus to idiopathic PTL.