Molecular aspects of adipoepithelial transdifferentiation in mouse mammary gland.

The circular, reversible conversion of the mammary gland during pregnancy and involution is a paradigm of physiological tissue plasticity. The two most prominent cell types in mammary gland, adipocytes and epithelial cells, interact in an orchestrated way to coordinate this process. Previously, we showed that this conversion is at least partly achieved by reciprocal transdifferentiation between mammary adipocytes and lobulo-alveolar epithelial cells. Here, we aim to shed more light on the regulators of mammary transdifferentiation. Using immunohistochemistry with cell type-specific lipid droplet-coating markers (Perilipin1 and 2), we show that cells with an intermediate adipoepithelial phenotype exist during and after pregnancy. Nuclei of cells with similar transitional structural characteristics are highly positive for Elf5, a master regulator of alveologenesis. In cultured adipocytes, we could show that transient and stable ectopic expression of Elf5 induces expression of the milk component whey acidic protein, although the general adipocyte phenotype is not affected suggesting that additional pioneering factors are necessary. Furthermore, the lack of transdifferentiation of adipocytes during pregnancy after clearing of the epithelial compartment indicates that transdifferentiation signals must emanate from the epithelial part. To explore candidate genes potentially involved in the transdifferentiation process, we devised a high-throughput gene expression study to compare cleared mammary fat pads with developing, contralateral controls at several time points during pregnancy. Incorporation of bioinformatic predictions of secretory proteins provides new insights into possible paracrine signaling pathways and downstream transdifferentiation factors. We discuss a potential role for osteopontin (secreted phosphoprotein 1 [Spp1]) signaling through integrins to induce adipoepithelial transdifferentiation.

IL-1ß and TGF-ß weaken the placental barrier through destruction of tight junctions: an in vivo and in vitro study.

INTRODUCTION: Chorioamnionitis is a gestational pathological condition characterized by acute inflammation of the amniochorionic membranes and placentas leading to high concentrations of IL-1ß, Il-6, Il-8 and TGF-ß in the amniotic fluid. In normal conditions, the permeability of foeto-maternal barrier is due to the assembly and maintenance of different cellular junctional domains. METHODS: In the present study, first we aimed to evaluate the protein expression (by immunohistochemistry and western blotting) and mRNA (by real time PCR) levels of the molecular components of tight junctions (Zonula occludens-1 and occludin), and of adherent junctions (VE-cadherin and ß-catenin) in placentas from chorioamnionitis compared to that in normal pregnancies. RESULTS: Western blotting results showed a significant down-regulation of occludin in placentas affected with chorioamnionitis. No differences were detected for the other proteins analysed. We evaluated whether occludin expression was regulated by IL-1ß, IL-6, IL-8 and TGF-ß by means of in vitro studies using HUVEC cultures and demonstrated a key role of IL-1ß and TGF-ß in the disappearance of occludin at cellular border. CONCLUSIONS: We conclude by suggesting a pivotal role of these two cytokines in facilitating intra-placental infection via para-cellular way due to the disassembly of tight junctions at trophoblastic and endothelial cells in placental tissues.

Activin-related proteins in bovine mammary gland: localization and differential expression during gestational development and differentiation.

Bovine mammary gland morphogenesis and differentiation are regulated by actions of growth factors including members of the transforming growth factor ß superfamily. Activins A and B, which are members of the transforming growth factor ß superfamily, bind selectively to ActRIB and ActRIIA receptors and their biological effects are antagonized by inhibins and follistatins. In the present paper we evaluated gene and protein expression of the activin and inhibin subunits ßA, ßB, and α-inhibin and follistatin and ActRIB and ActRIIA receptors in the mammary gland of nonpregnant and pregnant heifers. Mammary glands were obtained from nonpregnant Nelore (Bos indicus) heifers (n=9) and from primigravid Nelore heifers during early (n=9), mid (n=6), and late (n=5) pregnancy. Specimens of mammary tissue were analyzed by real-time PCR and immunohistochemistry. The ßA and α-inhibin subunits and ActRIB and ActRIIA mRNA expression was higher in the early-pregnancy group compared with the nonpregnant group. In the mid-pregnancy group, the subunits ßA, ßB, and α-inhibin as much as follistatin mRNA expression was higher compared with the nonpregnant group, whereas ActRIB transcripts were absent in the late-pregnancy group. Immunostaining of these proteins, with the exception of ActRIB, was observed in the mammary tissue sections at all time points analyzed; these findings are in agreement with the observed pattern of mRNA expression. Staining and mRNA expression for ActRIB were undetected in the late-pregnancy group. In summary, the present study demonstrated that the activin-related proteins, ßA, ßB, and α-inhibin subunits, as much as follistatin and ActRIB and ActRIIA receptors display different patterns of expression regarding time of gestation in the bovine mammary gland. The modulation of the expression pattern during gestation suggests that activin-related proteins may play a key role in regulating bovine mammary branching morphogenesis and epithelial differentiation.

Activating protein-1 family of transcription factors in the human placenta complicated by preeclampsia with and without fetal growth restriction.

Preeclampsia (PE) is a serious disorder of human pregnancy, it is often associated with fetal growth restriction (FGR) which is a failure of the fetus to reach its own growth potential. Activator protein-1 (AP-1) is a family of transcription factors inducible in response to a variety of extracellular stimuli and functions. AP-1 plays a complex role in the regulation of different fundamental cellular processes, including cell proliferation, survival, death and transformation. We investigate the expression pattern of AP-1 transcription factors in normal placentas during gestation and in placentas from PE without and with FGR using semiquantitative RT-PCR and immunohistochemistry techniques. The most interesting data concern the alterations of protein expression patterns of c-fos, Jun D and c-jun in normal gestation as well as in PE and PE-FGR pathologies. In addition, alterations but not significant changes are detected in mRNA expressions for these transcription factors. We strongly suggest that c-fos is implicated in regulating invasiveness mechanism of extravillous trophoblast in normal gestation as well as in PE placentas. In addition, we suggest that the opposite modulation of Jun D and c-jun in PE and PE-FGR supports the recent hypothesis that PE and PE-FGR could be considered two pathologies with different origin (maternal and placental) each of which has a different molecular pattern of expression.

Human placenta and fetal membranes express nerve growth factor mRNA and protein.

The present study investigated whether trophoblast, decidua and fetal membranes express nerve growth factor (NGF) mRNA and peptide. Tissue specimens were collected in the first and third trimester of pregnancy from women undergoing voluntary pregnancy interruption (no.= 6; from 8 to 12 gestational weeks) and from women having an elective caesarean section at term (no.= 6; week 39-40 of pregnancy). Using reverse transcriptase-polymerase chain reaction (RT-PCR), trophoblast, amnion/chorion and maternal decidua showed the expression of NGF mRNA both in early gestation and at term. By immunohistochemistry, the immunoreactive NGF was found in the cyto and syncytial trophoblast cells, chorionic mesodermic cells and in decidua. Vessel endothelial cells were stained in maternal compartments, while fetal vessels were unstained. These results, showing the expression and localization of NGF, support the current concept that human placenta is a potent neuroendocrine organ throughout gestation.

Mutational analysis of the inhibin alpha gene in preeclamptic women.

BACKGROUND: Preeclampsia (PE) is a disorder that occurs in at least 5% of pregnancies and affects both the mother and the unborn baby. A dramatic increase of maternal serum inhibin A concentration in the second and third trimester of pregnancy is a common feature of PE and inhibin A measurement may add significant prognostic information for predicting PE in pregnant women. DESIGN: We evaluated the presence and prevalence of gene polymorphisms for inhibin alpha subunit (INHalpha) in patients affected by PE (no.=50; study group), and in the general population (control group composed of 103 women and 42 men). METHODS: DNA extraction, single strand conformation polymorphism analysis, DNA sequencing, restriction fragment length polymorphism analysis, and Fisher's exact test were used. RESULTS: A 769G-->A transition was found in INHalpha1, but not in INHalpha2 or INHalpha3 fragment. This variant was found in 10/145 normal controls (7,6%), and in 1/50 preeclamptic patients (2%), without significant difference between the two groups (p=0.29). CONCLUSIONS: The prevalence of INHalpha gene variants is not increased in PE. Due to its frequency, the 769G-->A transition may be considered a polymorphism present in the general Italian population.

Inhibins and activins in pregnancy.

Human placenta, decidua, and fetal membranes are the major sites of production and secretion of inhibin A and activin A in maternal serum, amniotic fluid, and umbilical cord blood. These tissues also express follistatin-related gene and betaglycan, the binding proteins of activin A and inhibin A, respectively, recently identified. They show a different expression throughout pregnancy, suggesting new functional roles into gestational tissues. The availability of suitable assays for measuring inhibin A and activin A lead us the possibility to investigate their secretion in healthy pregnancy. In addition, several evidences underline the potential role and the clinical usefulness of their measurement in the diagnosis, prevention, prognosis and follow-up of different gestational pathologies such as: threatened abortion, placental tumors, hypertensive disorders of pregnancy, intrauterine growth restriction, fetal hypoxia. The measurement of inhibin A and activin A into the biological fluids of pregnancy will offer in the future further possibilities in early diagnosis, prediction, and monitoring pregnancy diseases.

Human placenta and fetal membranes express follistatin-related gene mRNA and protein.

Activin A is a placental glycoprotein and possible biological actions during pregnancy, suggested by experimental data, are the modulation of cytotrophoblast differentiation, placental hormonogenesis and uterotonins secretion. Follistatin-related gene (FLRG) is a 70 amino acids protein which binds activin A with high affinity, and which modulates its biological effects on target tissues by preventing the activin A interaction with its receptors. The present study investigated whether trophoblast, decidua and fetal membranes express FLRG mRNA (by RT-PCR) and peptide (by immunohistochemistry). Tissue specimens were collected at first and third trimester of pregnancy, from patients undergoing voluntary pregnancy interruption (no.=6; from 8 to 12 gestational weeks) and elective caesarean section at term (no.=6; 39-40 weeks of pregnancy). FLRG mRNA was expressed by the various gestational tissues both at early gestation and at term pregnancy. Immunoreactive protein was found in the trophoblast cells, epithelial amniotic and chorionic cells and maternal decidua; nevertheless, the most intense FLRG stain was detected in the walls of decidual and placental blood vessels. In conclusion, FLRG mRNA and peptide are expressed by placenta and fetal membranes. Its different immunolocalization with respect to follistatin and activin A supports a different role for FLRG in modulating activin A actions into gestational tissues.

Identification of urocortin mRNA and peptide in the human endometrium.

Urocortin is a 40-amino acid peptide belonging to the corticotropin-releasing factor (CRF) family. In human reproductive tissues, urocortin expression has been previously demonstrated in the ovary, in the placenta and fetal membranes and in pregnant uterine tissues, while no data are available on the expression of the peptide in the nonpregnant uterus. In this study, urocortin expression was evaluated by both immunohistochemistry and reverse transcription-polymerase chain reaction, in human uterine tissues and cells at different phases of the menstrual cycle. Urocortin was immunolocalized in endometrial epithelial and stromal cells, as well as in the myometrium, and in vascular smooth muscle cells. No differences between proliferative and secretory phase were observed. These results were confirmed by reverse transcription-polymerase chain reaction analysis of isolated endometrial epithelial and stromal cells, and myometrial specimens. These findings open new questions on the roles played by urocortin in the human uterus.

Pre-eclampsia with fetal growth restriction: placental and serum activin A and inhibin A levels.

Activin A (beta A beta A) and inhibin A (alpha beta A) are dimeric glycoproteins secreted from early to term pregnancy in the maternal circulation. They circulate in higher amounts in women with gestational hypertension and/or pre-eclampsia, the most important gestational diseases also causing fetal growth restriction (FGR). Since no data are available in patients with pre-eclampsia and superimposed FGR, by using two-site immunoassays we evaluated serum activin A and inhibin A levels in serum samples collected from: healthy normotensive pregnant controls (n = 42); and women with pre-eclampsia with (n = 19) or without superimposed FGR (n = 21). In addition, by quantitative reverse transcriptase-polymerase chain reaction the changes of alpha- and beta A-subunit mRNA expression in placentas collected from healthy controls (n = 7) and pre-eclamptic pregnancies with (n = 6) or without (n = 6) superimposed FGR was also investigated. Activin A and inhibin A serum levels were significantly higher in pre-eclampsia, and the presence of FGR did not significantly modify these concentrations. Similarly, inhibin-subunit mRNA levels in placentas from pre-eclampsia were significantly higher than in controls, and FGR did not significantly affect this expression. The present data suggest that the increased placental expression of inhibin subunit mRNAs is part of the mechanism leading to increased serum activin A and inhibin A levels.

Changes in inhibins and activin secretion in healthy and pathological pregnancies.

Inhibin-related proteins are involved in the control of the feto-maternal communication required to maintain pregnancy. Human placenta, decidua, and fetal membranes are the major sites of production and secretion of activin A, inhibin A and inhibin B in maternal serum, amniotic fluid, and cord blood. The availability of suitable assays developed in the last years has enabled the measurement of inhibins and activin A in their dimeric forms, in order to investigate their role in physiological conditions of pregnancy. The studies conducted on inhibin-related proteins and human pregnancy suggested the possibility of an involvement of inhibin A and activin A in the pathogenesis of gestational diseases. In fact, several lines of evidence underline the potential role and the clinical usefulness of inhibin-related proteins measurement in the diagnosis, prevention, prognosis and follow-up of different gestational pathologies such as early pregnancy viability, Down's syndrome, fetal demise, pre-eclampsia, pregnancy-induced hypertension, preterm delivery and intrauterine growth restriction. The measurement of inhibin A and activin A into the biological fluids of pregnancy will offer in the future, further possibilities in the early diagnosis, prediction, and monitoring diseases of pregnancy.