Immunohistological localization of human endometrial secretory protein, 'pregnancy-associated endometrial alpha 2-globulin' (alpha 2-PEG), during the menstrual cycle

The distribution of alpha 2-PEG, a human analogue of beta-lactoglobulin, in endometrium at different phases of the cycle was determined using immunohistochemistry with monoclonal and polyclonal antibodies. In the epithelial cells of glands in the functional zone of the endometrium, alpha 2-PEG was first detectable from Days 19 to 21 during the mid-luteal phase and maximal immunostaining was observed during the end of the late luteal phase. Intense staining in the glandular secretions and weaker staining in surface luminal epithelial cells during this period were observed. A minor population of basal glands contained alpha 2-PEG during the follicular phase. These results suggest that alpha 2-PEG synthesis by the glandular epithelium of the regenerated endometrium is hormonally regulated. Maximal staining occurring during the late luteal phase suggests that regulation may be related to the hormonal requirement for pre-decidualization rather than that required for histologically defined glandular epithelial secretion.     

Immunochemical detection, physicochemical characterization and levels of pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG) in seminal plasma of men

Pregnancy-associated endometrial alpha 2-globulin (alpha 2-PEG), the major secretory protein of the human uterine endometrium during the luteal phase of the menstrual cycle and early first trimester of pregnancy, has been detected by immunochemical techniques in seminal plasma. Biochemical analysis and immunoblotting has verified that immunoreactive alpha 2-PEG in seminal plasma exhibits properties identical to those of endometrial alpha 2-PEG, i.e. Concanavalin A-binding dimeric glycoprotein of native Mr 56,000, subunit Mr 28,000, average pI 4.7 and of alpha 2-mobility. Concentration of alpha 2-PEG in seminal plasma was 22.13 +/- 2.82 micrograms/ml (mean +/- s.e.m., n = 110) which compared to 12.02 +/- 1.65 micrograms/ml (mean +/- s.e.m., n = 48) found in amniotic fluid at 11-20 weeks of pregnancy, to 4.29 +/- 1.66 micrograms/ml (mean +/- s.e.m., n = 15) in uterine luminal fluid in women during the luteal phase and to 0.245 +/- 0.025 micrograms/ml (mean +/- s.e.m., n = 10) in sera at 10 weeks of pregnancy. This distribution is very different from that observed for pregnancy-associated placentally-derived serum proteins detected in seminal plasma. The source of alpha 2-PEG in seminal plasma is unknown but is unlikely to be the testis because of the normal levels observed in vasectomized men. In the endometrium alpha 2-PEG synthesis and secretion appears to be related to progesterone-dependent differentiation of the glandular epithelium. Therefore these observations suggest that a different mechanism of regulation of the gene for alpha 2-PEG operates in the male reproductive tract.     

Characterization of an insulin-like growth factor binding protein, analogous to human pregnancy-associated secreted endometrial alpha 1-globulin, in decidua of the baboon (Papio anubis) placenta

The major secreted protein of the human decidua (pregnancy-associated endometrial alpha 1-globulin [alpha 1-PEG]), is an insulin-like growth factor-binding protein (IGF-BP) that is immunologically and biochemically similar to placental protein 12 (PP12) extracted from term human placenta. Since previous studies have demonstrated that the baboon and human endometrium synthesize and release a number of biochemically and immunologically related polypeptides in culture, this study was undertaken to further characterize a related IGF-BP in baboon placental tissues. Decidua, chorio-amniotic membranes with adhering decidua (CAM-D), and placental villi were obtained from pregnant baboons between Days 134 and 160 of gestation by Cesarean sections. Portions of tissue were either cultured in the presence of 35S-methionine, fixed for immunocytochemistry, or frozen in liquid nitrogen for cytosol extraction. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) of tissue culture media (TCM) revealed that the major secretory product of the decidua and CAM-D was an acidic polypeptide (Mr 33,000). Western blot analysis and immunoprecipitation of TCM with murine monoclonal antibody (B2H10) against human alpha 1-PEG demonstrated that this molecule, secreted by the baboon decidua and CAM-D, but not the placental villi, was immunologically identical to the human IGF-BP. Immunocytochemical localization of IGF-BP was intense in the cytoplasm of stromal cells in decidua and CAM-D and absent in the placenta. Gel filtration of TCM and cytosol followed by screening of eluates for 125I-IGF-I binding resolved two peaks (Mr greater than 100,000 and 35,000) of specific IGF-BP in decidua and CAM-D. The 35,000 peak had 100-200 times the binding capacity of the Mr greater than 100,000 peak and a Kd of 1.14-1.83 nM. The eluates contained in the Mr 35,000 peak were also immunoreactive to alpha 1-PEG, as accessed by a polyclonal radioimmunoassay. Affinity cross-linking with 125I-IGF-I followed by sodium dodecyl sulfate-PAGE revealed an immunoreactive complex of Mr 36,000, confirming that the baboon protein represents a high affinity IGF-BP. These studies indicate that the hypertrophied stromal cells of the baboon decidua and CAM-D synthesize and release an IGF-BP as their major secretory product, analogous to the situation in humans. The results of this study suggest that this protein may play a role in the regulation of IGF action during pregnancy.     

The release of PGF2 alpha and PGE2 from separated cells of human endometrium and decidua

The capacity of separated glandular and stromal cells from endometrium and first trimester decidua to release prostaglandins (PGs) was studied over 48 hours in culture. Glandular preparations released more PGs than stromal preparations in all tissues. Stromal release of PGs did not alter throughout the cycle or in early pregnancy but the capacity of glandular preparations to release PGs varied considerably. Proliferative glands released most PGF2 alpha and PGE2 followed by secretory glands and decidua. Histamine (10(-5)) stimulated PG release from endometrial and decidual glands but the response of proliferative glands was greatest. Actinomycin D stimulated release of PGF2 alpha and PGE2 from glandular cells of secretory endometrium and decidua. These results suggest that in vitro release of PGs is suppressed after ovulation and is in part due to inhibition of PG release by a protein or proteins synthesized in the glandular fraction of secretory endometrium or decidua.     

Lipopolysaccharide induces the expression of interleukin-1alpha distinctly in different compartments of term and preterm human placentae

The aim of the study was to investigate the stimulatory effect of lipopolysaccharide (LPS) on IL-lalpha production in different compartments of term and preterm placental tissues. Homogenates from amnion, chorion, and from fetal (subchorionic placental tissues, maternal decidua, and mid-placental tissue before and after perfusion of isolated placental cotyledons of 5 term placentas and 4 placentas obtained after preterm birth (28-34 W of gestation) were examined. Isolated placental cotyledons were dually perfused LPS (100 ng/kg perfused placental tissue) was perfused into the maternal side during 10 hours. Homogenates of the samples were examined by ELISA for IL-1alpha levels, and paraffin sections of the samples were stained by immunohistochemical staining, to characterize the cellular origin of placental IL-1alpha. Paired t test and ANOVA determined statistical significance. In the homogenates, there was a tendency towards higher IL-lalpha levels in all preterm placental compartments as compared to the term compartments before perfusion. A significant increase was observed only in the chorion compartment (p = 0.035). LPS had significantly increased IL-la levels only in the decidua compartment of term placentas as compared to other placental compartments (p = 0.0004), and had decreased IL-1alpha levels in the mid-placenta (p = 0.034). In preterm placentas, addition of LPS did not affect the expression levels of IL-1alpha in either fetal or maternal compartments as determined by ELISA and immunohistochemical staining. IL-la levels in the chorion compartment of preterm placenta were significantly higher as compared to term placenta. LPS affects placental tissues of term and preterm placentas differently. Also, in the term placentas, LPS affected the different compartments differently. Thus, IL-1alpha may have a key role (as a autocrine/paracrine factor) in the regulation of normal and pathological pregnancy and parturition.     

Study of oxytocin receptor: II. oxytocin and prostaglandin F2 alpha receptors in human myometria and amnion-decidua complex during pregnancy and labor

Oxytocin receptors (OXT-R) and prostaglandin F2 alpha receptors (PGF2 alpha-R) in human myometrium, amnion and decidua during pregnancy and at parturition were examined in an effort to clarify their role in the initiation and maintenance of uterine contractions. The number of binding sites for OXT in myometria showed an increase as gestation advance (Ist trimester v.s. at term; 205 +/- 90 v.s. 671 +/- 98 fmol/mg protein, N = 5, p less than 0.01), and a rapid decrease following the onset of labor (254 +/- 60 fmol/mg protein, N = 5, p less than 0.02). On the other hand the number of PGF2 alpha-R, remained unchanged throughout pregnancy and in labor. This myometrial PGF2 alpha binding capacity was approximately 1/20 to 1/30 that of the OXT binding, while binding affinity was almost equal. The OXT-R both in amnion and decidua, which was 1/6 to 1/7 that in myometrium, showed no significant changes throughout pregnancy or after the onset of labor. Binding affinity for each tissue was almost the same and appeared to increase towards term but no statistical significance was detected. Present data confirmed the presence of OXT as well as PGF2 alpha receptors in the three functionally distinct entities of pregnant human uterus; myometrium, amnion, and decidua. Among the components, the OXT binding increased only in the myometrium during pregnancy, suggesting this tissue specifically responds to OXT. In contrast, there was a constant binding in myometria for PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression and localization of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in murine and human placentas.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is one of the scavenger receptors that recognizes oxidized low-density lipoprotein as a major ligand. The placenta is a major source of prooxidant during pregnancy, and the level of placental oxidative stress increases rapidly at the end of the first trimester and tapers off later in gestation. In our study, we evaluated placental expression of LOX-1 during different gestational stages in mice and humans. We used immunohistochemistry and ISH to identify LOX-1-expressing cells in murine and human placentas. In both species, higher expression of LOX-1 mRNA during early to midgestational stages compared with late gestation-corresponding to the increased oxidative stress in early pregnancy-was shown by real-time RT-PCR. In murine placenta, we showed that LOX-1-expressing cells were fibroblast-like stromal cells in metrial glands and decidua basalis and that they were glycogen trophoblast cells in the junctional and labyrinth zones. In the human, LOX-1 expression was detected in villous cytotrophoblasts in both first trimester and term placentas. These localization patterns of LOX-1 in murine and human placentas suggest the possible involvement of LOX-1 in high oxidative stress conditions of pregnancy.     

IL-11 and IL-11Rα immunolocalisation at primate implantation sites supports a role for IL-11 in placentation and fetal development

Embryo implantation, endometrial stromal cell decidualization and formation of a functional placenta are critical processes in the establishment and maintenance of pregnancy. Interleukin (IL)-11 signalling is essential for adequate decidualization in the mouse uterus and IL-11 promotes decidualization in the human. IL-11 action is mediated via binding to the specific IL-11 receptor α (IL-11Rα). The present study examined immunoreactive IL-11 and IL-11Rα in cycling rhesus monkey endometrium, at implantation sites in cynomolgus and rhesus monkeys and in human first trimester decidua and defined distinct spatial and temporal patterns. In cycling rhesus monkey endometrium, IL-11 and IL-11Rα increased in both basalis and functionalis regions during the secretory compared with the proliferative phase, with changing cellular locations in luminal and glandular epithelium and stroma. The patterns were similar overall to those previously described in human endometrium. Differences were seen in immunostaining during implantation in cynomologus and rhesus monkey. In the cynomolgus, very little staining for IL-11 or IL-11Rα was seen in syncytio- and cyto-trophoblast cells in the villi between days 12 and 150 of pregnancy although there was moderate staining in cytotrophoblast in the shell between days 12 and 17 and in subpopulations of cytotrophoblast cells invading the arteries at day 17. By contrast in the rhesus monkey between days 24 and 35 of pregnancy and in human first trimester placenta, cyto- and syncytio-trophoblast in the villi but not cytotrophoblast in the shell were positively stained. The most intense staining for both IL-11 and IL-11Rα was present within the decidua in the maternal component of implantation sites in all three primates but moderate staining was also present in maternal vascular smooth muscle and glands perivascular cells and epithelial plaques. These results are consistent with a role for IL-11 both during decidualization and placentation in primates.     

Effect of luteinizing hormone (LH), pregnancy specific protein B (PSPB), or arachidonic acid (AA) on ovine endometrium of the estrous cycle or placental secretion of prostaglandins E2 (PGE2) and F2alpha (PGF2alpha) and progesterone in vitro

The objective of this experiment was to determine the effect of AA, LH, or PSPB on secretion of PGE2, PGF2alpha, or progesterone by ovine caruncular endometrium of the estrous cycle or placental tissue of pregnancy in vitro. Ovine caruncular endometrium of the estrous cycle (days 8, 11, 13, and 15) or caruncular/placental tissue on days 8, 11, 13, 15, 20, 30, 40, 50, 60, and 90 postbreeding were incubated in vitro with vehicle, AA, LH, or PSPB in M-199 for 4 and 8 h. Secretion of PGF2alpha by caruncular endometrium of non-bred ewes on days 13 and 15 and by caruncular/placental tissue of bred ewes on days 13, 15, 20, 30, and 40 was increased (P < or = 0.05) when incubated with vehicle and declined (P < or = 0.05) after day-40 in bred ewes. Secretion of PGF2alpha by day-15 caruncular endometrium of non-bred ewes and bred ewes was increased (P < or = 0.05) by AA on days 13 and 15 and by LH on day-15. Secretion of PGF2alpha by caruncular/placental tissue from bred ewes was (P < or = 0.05) by AA on days 13, 15, 20, 30, and 40 and by LH on days 15, 20, 30, and 40, after which the response decreased (P < or = 0.05). Secretion of PGF2alpha by caruncular endometrium of non-bred ewes during the estrous cycle or by caruncular/placental tissue of bred ewes during the first trimester was not affected by PSPB (P > or = 0.05). Secretion of PGE2 by caruncular endometrium of non-bred ewes did not change (P > or = 0.05) and was increased (P < or = 0.05) by caruncular/placental tissue on days 13-90 from bred ewes when incubated with vehicle. Secretion of PGE2 by endometrium from non-bred ewes was not affected (P > or = 0.05) by AA, LH, or PSPB, but was increased (P < or = 0.05) by AA or LH on days 13-50 and by PSPB on days 60 and 90 when incubated with caruncular/placental tissue from bred ewes. Secretion of progesterone by placental tissue of bred ewes increased (P < or = 0.05) on day-50 and continued to increase through day-90. In summary, uterine/placental tissue secretion of PGF2alpha is not reduced until the end of the first trimester of pregnancy in ewes. In addition, LH appears to play a role in luteolysis of non-bred ewes by stimulating caruncular endometrial secretion of PGF2alpha and on day-5 postbreeding to prevent luteolysis during early pregnancy by stimulating caruncular/placental secretion of PGE2 throughout the first trimester of pregnancy in sheep. Secretion of PGE2 by caruncular/placental tissue after day-50 of pregnancy appears to be regulated by PSPB, not LH.     

The effect of steroid sex hormones on the biosynthesis of alpha 2-macroglobulin and pregnancy-associated alpha 2-glycoprotein in cultures of peripheral blood mononuclear cells]

The peripheral blood mononuclears are capable of intense biosynthesis of alpha 2-macroglobulin and of weak biosynthesis of pregnancy-associated alpha 2-glycoprotein. Sex hormones of men and non-pregnant women exert no influence on the protein biosynthesis. During pregnancy alpha 2-macroglobulin biosynthesis is shortly activated, although it does not depend on the influence of sex hormones. All the steroid sex hormones provide a short-term biosynthesis of this protein during the II trimester of pregnancy, while testosteron inhibits it during the III trimester. Possible mechanisms of control of biosynthesis of these proteins are discussed.     

Protein synthesis and secretion by the human endometrium during the menstrual cycle and the effect of progesterone in vitro

To identify markers of endometrial differentiation specimens of endometrium from the menstrual cycle were incubated in vitro with [35S]methionine, in the absence or presence of progesterone, and protein synthesis and secretion were studied by fluorographic analysis of one dimensional SDS/gradient polyacrylamide gels. Changes were demonstrated in the rate of synthesis and secretion of a number of endometrial proteins (EP) during the cycle and in response to progesterone. Endometrial proteins were classified into three groups: Group I-synthesized and secreted throughout the menstrual cycle and unaffected by progesterone exposure; Group II-synthesis and secretion associated with histological type of endometrium and unaffected by progesterone exposure, e.g. EP 13 (Mr 33,000) with proliferative, EP 15 (Mr 28,000) with secretory and EP 14 (Mr 32,000) with late secretory endometrium; Group III-synthesis and secretion regulated by progesterone exposure irrespective of source of endometrium, e.g. EP 9 (Mr 54,000) and 11 (Mr 45,000). The Group II proteins EP 14 and 15 were also the major secretory protein products of endometrium from first and second trimester pregnancy respectively, the native forms referred to as pregnancy-associated endometrial alpha 1- and alpha 2-globulins (alpha 1- and alpha 2-PEG). We conclude that EP 15 (alpha 2-PEG) represents a human analogue of uteroglobin.     

Modulation of alpha2beta1 integrin changes during mammary gland development by beta-oestradiol

In order to study the role of cell-matrix interactions in mammary gland function, temporal changes in alpha2beta1 integrin, the major receptor for collagen and the influence of beta-oestradiol on its level and distribution in rat mammary gland at different stages of development were studied. The level of alpha2beta1 integrin determined by ELISA, was found to be high during different days of pregnancy, while in the lactating stage, it was significantly reduced. By immunocytochemical analysis, alpha2beta1 integrin was found to be localized towards the luminal side of acinar cells, both in the virgin and midpregnant stage, while it was not detected in the lactating stage. The possible role of hormones in modulating the level of integrin was examined in both in vitro and in vivo experiments using beta-oestradiol. Supplementing beta-oestradiol to isolated mammary epithelial cells from both virgin and lactating glands caused a concentration dependent increase in the incorporation of [35S]methionine into alpha2beta1 integrin associated with the cells. Administration of beta-oestradiol to virgin and lactating glands caused about 1.4-4-fold increase in the level of alpha2 integrin, indicating that upregulation of integrin during pregnancy may be due to oestrogen and as the oestrogen level falls during lactating phase, downregulation of alpha2beta1 integrin occurs. Treatment with beta-oestradiol also resulted in the appearance of alpha2beta1 integrin in the acinar region of the lactating tissue, while in the untreated controls no staining for integrin was seen. These results indicate that oestrogen, apart from directly affecting the cellular activity, can influence mammary tissue function by affecting cell-ECM interactions through the modulation of integrin receptors for matrix proteins.     

Changes in urinary 6-keto-prostaglandin F1 alpha excretion during pregnancy and labor

Urinary excretion of 6-keto-PGF1 alpha was measured by high pressure liquid chromatography and radioimmunoassay at various stages of pregnancy and labor. In the first trimester of pregnancy, urinary 6-keto-PGF1 alpha concentrations were not different from those measured before pregnancy, but they showed a significant increase in the second trimester of pregnancy (p less than 0.001). The levels rose further in the third trimester, although this increase was not statistically significant when compared to levels obtained in the second trimester. There was no evidence for a significant change in 6-keto-PGF1 alpha excretion with the onset of labor. During well-established, progressive labor mean values of 6-keto-PGF1 alpha excretion were about twice as high as before the onset of labor, but the range of values during labor was so wide that there was no statistical difference with values obtained in the second half of pregnancy. It is concluded that the increase in the urinary excretion of 6-keto-PGF1 alpha occurs later in pregnancy than the increase in TXB2 excretion and that labor at term is not associated with marked changes in 6-keto-PGF1 alpha excretion.     

Immunohistochemical co-localization of placental lactogen II and relaxin in the golden hamster (Mesocricetus auratus)

Two hormones with lactogenic activity are produced by the hamster placenta during the second half of pregnancy. One of these hormones, hamster placental lactogen II (haPL-II), has been well characterized; however, its cellular source is not known. In the present study, haPL-II was localized in placental tissues using a specific antibody and the avidin-biotin-peroxidase immunohistochemical technique. Because relaxin has been localized in the hamster placenta, it was of interest to determine if haPL-II and relaxin are localized in the same cells. haPL-II immunoactivity was observed in primary and secondary giant trophoblast cells of the placenta on Days 12, 14, and 15 of pregnancy. On Day 15 positive staining was also observed in large cells located within mesometrial arteries and in eosinophilic bodies associated with degenerating sheathed arteries of the decidua basalis. haPL-II-positive staining was not observed in placentae from Days 8 or 10 of pregnancy. On Day 14, haPL-II was colocalized with relaxin in 75% of the giant trophoblast cells observed. Therefore, it is probable that these hormones are synthesized and secreted by the same cell.     

Expression and cellular distribution of NADPH-diaphorase and nitric oxide synthases in the porcine uterus during early pregnancy

Nitric oxide plays a key role in the regulation of various female reproductive processes such as ovulation, implantation and myometrial relaxation. The aim of the present study was to determine the histochemical activity and cellular localization of NADPH-d in the porcine uterus during early pregnancy, including the implantation period. Tissue samples collected from the pig uteri on days 5, 10, 12, 15 and 17 of pregnancy were stained histochemically for NADPH-d activity and immunohistochemically for NOS isoforms localization. In the luminal epithelium a significant increase of NADPH-d activity was observed on days 5-12 of pregnancy. On day 17 of pregnancy, two different staining patterns were observed: 1) a significant (p0.001) decrease in NADPH-d activity at the site of implantation and 2) the high NADPH-d activity at inter-implantation regions. The endometrial glands showed a significant (p0.001) increase in NADPH-d staining with high activity in individual glands. The arterial endothelium expressed stronger NADPH-d staining compared with venous vessels. Immunoreactivity of eNOS was similar to NADPH-d staining but no optical differences in the intensity of staining were observed. Clear iNOS immunoreactivity was detected in the luminal epithelium, endometrial stroma and individual endometrial glands. The vascular endothelium displayed weak iNOS staining.     

Expression of the Thomsen-Friedenreich antigen and of its putative carrier protein mucin 1 in the human placenta and in trophoblast cells in vitro

The Thomsen-Friedenreich (TF) antigen (or, more precisely, epitope Galbeta1-3GalNAcalpha-O-) has been known for a long time as a carcinoma-associated antigen. In normal tissues the occurrence of TF antigen is restricted to a few immunologically privileged areas. Here we report on the identification of the TF epitope and its putative carrier protein mucin 1 (MUC1) in human placental tissue, on isolated trophoblast cells in vitro and on trophoblast tumour cell lines BeWo and Jeg3. Cryosections of placental and decidual tissues of the first, second and third trimester were double stained with monoclonal antibodies directed against the TF epitope (IgM) and against MUC1 (IgG). In the first trimester of pregnancy we found strong expression of TF antigen and MUC1 at the apical side of the syncytiotrophoblast directed towards the maternal blood. This expression was consistent in the second trimester of pregnancy, and to a lesser degree in the third trimester. In addition, we found positive staining for TF antigen and MUC1 on extravillous trophoblast cells in the decidua during the first and second trimester of pregnancy. Trophoblast tumour cells of the cell line BeWo, which form a syncytium in vitro, were also positive for TF antigen and MUC1, whereas Jeg3 cells, which are unable to form a syncytium, expressed only MUC1. Freshly isolated trophoblast cells from first trimester placentas showed strong staining for MUC1; however, only a few of these cells (less than 1%) were positive for TF antigen, and might consist of digested fragments of the syncytium. In summary, TF antigen and MUC1 are expressed by the syncytiotrophoblast at the feto-maternal interface and by extravillous trophoblast cells invading the decidua, whereas villous cytotrophoblast cells in situ as well as freshly isolated trophoblast cells from first trimester placentas only express MUC1 but not TF antigen.     

Temporospatial changes of kinin b2 receptors during the estrous cycle and pregnancy in the rat uterus

Tissue kallikreins are present in rat uterus during the estrous cycle in luminal and glandular epithelium, in early gestation in the implantation node, and in the last third of pregnancy surrounding the sinusoids in the decidua basalis. The pattern of kinin B2 receptor expression, through which the vasoactive effect of kallikreins is exerted, was studied by in vitro autoradiography and immunohistochemistry. The kinin B2 receptor was observed in the luminal and glandular epithelium, myometrium, endothelial cells of arteries, veins and venules, and smooth muscle cells of endometrial and myometrial arterioles. Immunoblotting of crude membranes revealed a band of 69 kDa that increased in late proestrus and estrus, concordantly with the pattern of immunostaining observed in the tissue. At Day 7 of gestation, the kinin B2 receptor was expressed (binding sites and receptor protein) in the epithelium of the implantation node and decidual cells; these latter cells showed a further increase during gestational Days 9 and 10. From Days 14 to 21, the subplacental decidua became strongly immunoreactive, and on Days 16 and 21 the placental labyrinthine endothelium was intensely stained. During this period, endothelium of arteries and veins, smooth muscular cells of small diameter arterioles, and myometrium also expressed B2 receptors. In unilaterally oil-stimulated pseudopregnancy, the decidual cells and the glandular epithelium show similar immunoreactivity to that during pregnancy. The temporospatial pattern of kinin B2 receptors, coinciding with that of kallikrein or with sites accessible to the generated kinins, further supports an autocrine-paracrine role for the kallikrein-kinin system in the vasoactive changes of implantation and placental blood flow regulation.     

Cloning and characterization of an apoptosis-associated gene in the human placenta

Placenta is a transient feto-maternal association that develops during mammalian pregnancies. Human placental tissue during the first trimester of pregnancy is an actively dividing and differentiating tissue, while near term, it represents a fully differentiated unit performing many life-sustaining functions for the fetus. Previous studies have demonstrated that the percentage of placental cells that undergo apoptosis is greater at full term as compared to the first trimester of pregnancy. In this study, we undertook a study aimed at gaining an insight into the kind of genes expressed in the two developmentally distinct stages of gestation ie, the first trimester and term using Differential Display RT-PCR. Cloning and sequencing of one of the differentially expressed cDNAs from term placental tissue revealed that it is a novel gene, referred to as T-18 in the text. In this study, we also examined the regulation of this gene during apoptosis in the human placenta. A model for analysis of placental apoptosis was established by incubating placental villi in serum-free culture medium. It was observed that apoptosis occurred rapidly following incubation of placental villi without tropic support, and the proposed free-radical scavenger, superoxide dismutase (SOD) suppressed apoptosis in the placenta. Interestingly, the levels of T-18 mRNA increased significantly during spontaneous induction of apoptosis and decreased when apoptosis was blocked by SOD. These data clearly suggest that there is a strong correlation between the expression of T-18 and placental apoptosis and that T-18, may play a significant role in this process. Furthermore, the establishment of a defined in vitro explant culture model should facilitate elucidation of factors, which regulate apoptosis in human placenta.