Human amnion : the establishment of an amnion bank and its practical applications in surgery.
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Amnion↗
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[Amnionic infusion therapy in conditions with low amnionic fluid levels].
INTRODUCTION: Amniotic fluid volume reduction can have serious consequences: prior to 24 gestational weeks hypoplasia of fetal lungs and later in pregnancy cord compression and fetal hypoxia as well as contractions of extremities. Diagnosis of oligohydramnios is made either after a subjective estimation of amniotic fluid reduction or if the biggest amniotic fluid pocket is less than 1 cm. Amnioinfusion is a procedure during which a crystalloid solution, most often saline, is instilled into the amniotic cavity substituting amniotic fluid. To estimate the efficacy and safety of amnioinsfusion using our results and literature review. MATERIAL AND METHODS: Up to 800 ml of sterile saline solution was instilled intraamniotically (10-15 ml/min) in cases where the amniotic fluid index was less than 10 and intraamniotic infection was excluded. After that, 1 g of Longaceph was given intraamniotically. Infusion was stopped immediately when 800 ml was instilled, if a subjective estimation showed that there was enough fluid or if contractions occurred. RESULTS: During a six-month period there were five amnioinfusions--four therapeutical and one diagnostic; in four cases the procedure was successful and in one preterm rupture of membranes occurred 20 hours after the procedure. The procedure was most often done in the first half of the third trimester and continuation of pregnancy in successful cases was between 4 and 5 weeks, with average fetal weight gain of about 1200 gr. No complications occurred in cases where pregnancy continued. CONCLUSION: In our preliminary study amnioinfusion led to prolongation of pregnancy in majority of cases providing better maturation of fetal lungs and higher birth weight, without any complications. Further studies are necessary to reach definite conclusions about the efficacy and safety of amnioinfusion.
Crystalloid Solutions↗
[Premature rupture of amnion and ascending infection of amnion fluid. Experimental study].
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Amniotic Fluid↗
Pemphigus and pemphigoid antigens are expressed in human amnion epithelium.
The sera of patients with pemphigus vulgaris (PV) and bullous pemphigoid (BP) contain autoantibodies which react with antigens present in a variety of mammalian squamous epithelia. The biologic role of these epithelial antigens is unknown; however, they do appear to be markers of epithelial differentiation. We have examined many human tissues that may be used as sources of large amounts of BP and PV antigens, including the human amnion, which is composed of the amnion reflectum and placentum (epithelial monolayers) and amnion cord (stratified epithelium). Human amnion was obtained from normal term deliveries and specimens of each area of the amnion were processed for light and electron microscopy. Samples of amnion were snap-frozen in liquid nitrogen and 4-micron sections were used as a substrate for BP and PV antibodies by indirect immunofluorescence (IF) techniques. Well-characterized BP serum (indirect IF titer 1:2560), PV serum (indirect IF titer 1:160), and normal human serum (negative indirect IF) were utilized as sources of BP and PV autoantibodies and a negative control, respectively. Linear staining of the BMZ was produced by BP antibodies in 8/8 specimens of amnion reflectum, 8/8 specimens of amnion placentum, and 3/3 specimens of amnion cord. Staining of the epithelial intercellular spaces was produced by PV antibodies of 2/3 specimens of amnion cord and none of the amnion reflectum (0/8) or amnion placentum (0/8) tested. Normal human serum produced no specific staining of the amnion. The light and the ultrastructural features of human amnion basement membrane zone and intercellular spaces resembles closely their epidermal counterparts. The restricted distribution of BP antigen in amnion epithelial basal cells (amnion reflectum, placentum, and cord) and PV antigen in stratified amnion epithelium (amnion cord) reinforces their relationship with epithelial differentiation. The abundance and availability of these tissues facilitate extraction and characterization of BP and PV antigens.
Amnion↗
Effectiveness of human amnion preserved long-term in glycerol as a temporary biological dressing.
Human amnion as a temporary biological wound dressing has remained a beneficial and cost-effective means of treating burns in developing countries. The aim of this study was to determine whether human amnion that has undergone long-term preservation in glycerol is an effective biological dressing compared to fresh amnion and glycerol-preserved human skin. Samples of human amnion and skin were preserved in sterile containers of 85% glycerol at 4 degrees C for over a year. Dorsal full-thickness or split-thickness skin wounds were produced in rats. The defects were divided into four areas, each of which was covered with preserved amnion, fresh amnion, preserved skin, or left uncovered as a control. The materials on the wounds were evaluated macroscopically and microscopically after 2, 4, 7, 10 and 14 days. The primary take or adherence of the grafts on full-thickness wounds was evaluated at 4 and 7 days, and material performance was scored based on several macroscopic and microscopic criteria. The bacteria levels reducing effect of the materials were examined by quantitative bacteriology in heavily infected full-thickness scald burn wounds of rats. Qualitative cultures confirmed that the storage conditions the materials were subjected to for over a year were aseptic and that the amnion and skin had maintained their characteristic properties. All materials were found effective on partial-thickness rat wounds as a cover under which re-epithelialization was completed by 7 days. The preserved skin performed better than either preserved or fresh amnion on full-thickness wounds but the performance of preserved amnion was comparable to that of fresh amnion. Glycerol-preserved amnion was found to be as effective as fresh amnion or skin in terms of decreasing bacterial levels in infected rat burn wounds. Amnion stored in glycerol is reliable and effective for a long period of time. Amnion banking could provide an unlimited quantity of biologic dressing for burn treatment at low cost, a factor that is particularly important in developing countries.
Amnion↗
Endothelin-1 gene expression and regulation of endothelin mRNA and protein biosynthesis in avascular human amnion. Potential source of amniotic fluid endothelin.
We demonstrated previously that preproendothelin mRNA is present in avascular human amnion tissue and in human amnion cells maintained in primary monolayer culture. In this investigation we sought to identify the specific endothelin (ET) gene that is expressed in amnion and to determine whether endothelin is produced by amnion. Using oligonucleotides specific for ET-1, ET-2, and ET-3 mRNA, we identified preproET-1 mRNA in human amnion tissue. By radioimmunoassay of ET we found that human amnion tissue explants and amnion cells in culture secrete immunoreactive ET into the medium. PreproET mRNA levels and immunoreactive ET production by human amnion cells in monolayer culture are increased in response to treatment with agents that are known to be present in human amniotic fluid, i.e. epidermal growth factor, interleukin-1, and tumor necrosis factor-alpha. We found that the level of preproET mRNA in amnion cells was low compared with that in human umbilical endothelial cells; treatment with cycloheximide together with a stimulus of ET-1 gene transcription led to a striking increase in the level of preproET mRNA in amnion cells compared with a much weaker response in endothelial cells. These findings suggest that protein synthesis-dependent mechanisms may be of great importance in maintaining low levels of preproET mRNA in amnion tissue and in regulating the amount of preproET mRNA in amnion exposed to stimuli of ET-1 transcription. In addition, we demonstrated that immunoreactive ET is present in human amniotic fluid at the midtrimester of pregnancy and at term. Thus, it is likely that the avascular fetal amnion is one tissue site of origin of ET in amniotic fluid during human pregnancy.
Amnion↗
[A study on the regulation of intrauterine milieu by bioactive substances of fetal origin in the human amniotic fluid--the analyses of interactions among amnion, chorion laeve, and decidua vera tissues].
To elucidate the regulatory mechanism of human intrauterine milieu, the effects of various substances on the production of endothelin (ET) and brain natriuretic peptide (BNP) by amnion cells were investigated. In addition, we examined the regulation of phospholipase D (PLD) activity, which has been shown to be involved in the signal transduction in various tissues such as ovary, adrenal gland, etc. The ET production by cultured amnion cells was stimulated by epidermal growth factor (EGF), transforming growth factor-beta (TGF-beta), or interleukin-1 (IL-1). Ligand binding analyses indicated that both ET-A receptor and ET-B receptor are present in chorion laeve, decidua vera, and myometrium, but not in the amnion tissue at term. However, amnion tissue in the second trimester showed a significant amount of binding capacity for ET-1 but not for ET-3, indicating the presence of ET-A receptor in this tissue in the second trimester. These observations were confirmed by Northern blot analyses. In cultured amnion cells, ET-B receptor was detected by Northern blot analysis. The expression of this ET-B receptor in cultured amnion cells was down-regulated by the addition of EGF, but not by ET-1, IL-1 or A23187. Moreover, ET-1 inhibited the secretion of prostaglandin E2 (PGE2) by cultured amnion cells. These results suggest that ET-1 secreted from amnion cells may block prostaglandin synthesis in amnion cells during the second trimester, but this block may be released at term by the action of EGF. The BNP production by cultured amnion cells was dose-dependently stimulated by TGF-beta, but was inhibited by cortisol or EGF. TGF-beta (approximately 400 pM) was detected in the human amniotic fluid by a bioassay. The TGF-beta augmented BNP production was blocked by the simultaneous treatment with cortisol or EGF. The receptor for BNP (particulate guanylate cyclase A-type: GC-A) was identified in chorion, decidua, and myometrium by both cGMP generation assay and Northern blot analysis. However, GC-A was not detected in amnion tissues in the second trimester and at term. In an in vitro experiment with rat pregnant uterus, both BNP and cGMP dose-dependently inhibited the prostaglandin F2 alpha induced uterine contraction. Thus, BNP secreted from amnion cells may not act on amnion tissue, but on the decidua and myometrium, and generate cGMP, the second messenger of BNP, and finally block uterine contraction during the second trimester.(ABSTRACT TRUNCATED AT 400 WORDS)
Amniotic Fluid↗
Parathyroid hormone-related protein mRNA in avascular human amnion.
Previously, we found that preproendothelin-1 mRNA is present in human avascular amnion tissue. In this investigation, we evaluated the possibility that another vasoactive protein, namely, parathyroid hormone-related protein (PTH-rP), also is produced in amnion. Using a specific cDNA probe, we identified PTH-rP mRNA in amnion tissue and found that the level of PTH-rP mRNA in placental amnion was greater than that in reflected amnion tissue obtained from the same pregnancy. PTH-rP mRNA also was demonstrable in chorion laeve and in decidua, but the levels of this mRNA in these tissues were much lower than that in amnion. By radioimmunoassay, we found that human amnion cells in primary monolayer culture secrete immunoreactive PTH-rP into the medium. Importantly, the placental amnion covers the chorionic vessels that traverse over the chorionic plate prior to branching into the cotelydons; specifically, there is no intervening tissue between placental amnion and the adventitial tissue of the chorionic vessel wall. Thus, the potential exists for the production of endothelin-1, a potent vasocontractant, and PTH-rP, a vasorelaxant, in placental amnion for export to the adventitial surface of the chorionic vessels. Moreover, amnion cells respond to a number of agents (e.g., transforming growth factor-beta) that effect changes in the expression of these two peptides. Therefore, the possibility should be considered that amnion-derived vasoactive proteins may modulate fetal chorionic, umbilical, and villous vessel tone and thereby fetal-placental blood flow.
Amnion↗
Tissue inhibitor of metalloproteinase-1 and tissue inhibitor of metalloproteinase-2 expression in human amnion mesenchymal and epithelial cells.
OBJECTIVE: This study was conducted to define the cellular site of expression of tissue inhibitor of metalloproteinase-1 and tissue inhibitor of metalloproteinase-2 in human amnion by an evaluation of the levels of messenger ribonucleic acids in separated amnion epithelial and mesenchymal cells and to ascertain whether amnion epithelial and mesenchymal cells maintained in culture continue to express tissue inhibitor of metalloproteinase messenger ribonucleic acids. STUDY DESIGN: Human placentas and fetal membranes were obtained immediately after delivery. Amnion tissue was separated from chorion laeve and either frozen immediately (-80 degrees C) or processed by differential enzymatic treatment to separate the epithelial and mesenchymal cells, which were frozen (-80 degrees C) or else plated and maintained in monolayer culture. The levels of tissue inhibitor of metalloproteinase types 1 and 2 messenger ribonucleic acid were evaluated by Northern analyses of total ribonucleic acid extracted from amnion tissue, freshly separated epithelial and mesenchymal cells, and epithelial and mesenchymal cells in monolayer culture. RESULTS: Tissue inhibitor of metalloproteinase types 1 and 2 messenger ribonucleic acids were detected by Northern analysis in freshly isolated amnion tissues from midtrimester and term pregnancies. The major species of tissue inhibitor of metalloproteinase-1 messenger ribonucleic acid was 0.9 kb in length; a minor species of approximately 3.5 kb also was present. Tissue inhibitor of metalloproteinase-2 messenger ribonucleic acids of 3.5 and 1.0 kb and of similar intensity were also detected. The levels of type 1 messenger ribonucleic acid were not different in amnion tissues obtained at term or during the midtrimester of pregnancy. The levels of tissue inhibitor of metalloproteinase type 2 messenger ribonucleic acids in amnion tissue most commonly were greater at term than in tissues obtained during the midtrimester. The level of type 1 messenger ribonucleic acid in mesenchymal cells was appreciably greater than that in epithelial cells, and this difference was maintained during culture of these cells. The level of type 2 messenger ribonucleic acid was similar in both cell types and was maintained during culture. The levels of type 1 or 2 messenger ribonucleic acids were not affected by treatment of amnion epithelial or mesenchymal cells in culture with a variety of test agents, including steroid hormones, cytokines, and growth factors. CONCLUSION: The amnion mesenchymal cells are the primary source of tissue inhibitor of metalloproteinase-1 in human amnion, whereas both cell types have the potential to produce tissue inhibitor of metalloproteinase-2.
Amnion↗
Characterization of the major phosphoinositide-specific phospholipase C of human amnion.
Most of the phosphoinositide-specific phospholipase C activity in human amnion at term was found to be attributable to a single isoform (Mr 85,000). Phospholipase C purified from amnion catalyzed the calcium-dependent hydrolysis of both phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate. The high phospholipase C activity of amnion cells isolated at 38-41 weeks of gestation declined greater than 80% during the initial 2-5 days of culture to values characteristic of amnion tissue in early gestation. Activities of phospholipase A2 and phosphatidylinositol synthase remained essentially unaltered during this period of culture. Loss of phospholipase C activity was apparently due neither to the appearance of an inhibitor nor to the loss of an activator and most likely reflected a decrease in the amount of enzyme in amnion cells. Basal production of prostaglandin E2 (PGE2) by amnion cells also declined greatly during the period of loss of phospholipase C activity. Involvement of phospholipase C in the regulation of amnion prostaglandin production was also supported by the finding that the phospholipase C inhibitor, U-73122, potently inhibited amnion cell PGE2 production. In contrast, vasopressin, which appears to stimulate prostaglandin production in amnion cells by a phospholipase C-dependent mechanism, was equipotent in stimulating PGE2 production by amnion cells on Day 2 and Day 5 of culture, even though phospholipase C activity had declined by more than 75%. Furthermore, epidermal growth factor stimulation of PGE2 production by amnion cells appeared to be largely attributable to an increase in prostaglandin H synthase activity and did not involve an increase in phospholipase C activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Amnion↗
Amnion epithelial cells, in contrast to trophoblast cells, express all classical HLA class I molecules together with HLA-G.
PROBLEM: The expression of the non-classical HLA-G gene has been shown at the protein level on trophoblast-derived embryonic tissue, like the extravillous cytotrophoblast. However, the presence of HLA-G on embryoblast-derived cells is currently controversial. The amnion epithelium is an embryoblast-derived cell layer covering the amnion cavity and is the main source for the amnion fluid. METHOD: The expression of HLA class I molecules was investigated by immunohistochemical, biochemical, and molecular biological methods in amnion membranes and amnion fluid. RESULTS: Immunohistochemically, HLA-C and occasionally also-B molecules as well as HLA-A and/or -G molecules have been identified on amnion epithelial cells. These results were extended by Western blotting with purified amnion epithelial cells where HLA-B and/or -C, HLA-A and HLA-G antigens have been detected. As expected HLA-G mRNA was detected in amino epithelial cells. Furthermore, classical HLA molecules as well as HLA-G were found in amnion fluid. CONCLUSION: These results show that the amnion epithelium frequently expresses classical HLA class I molecules as well as HLA-G. The expression of HLA-G antigens on amnion epithelial cells and their presence in the amnion fluid, which is continually ingested by the fetus, may be particularly relevant for the induction of peripheral tolerance.
Amnion↗
Reduction of extracellular matrix protein expression in human amnion epithelial cells by glucocorticoids: a potential role in preterm rupture of the fetal membranes.
Low levels of expression of extracellular matrix (ECM) proteins in chorioamniotic membranes is a characteristic of prematurely ruptured membranes, a condition associated with 40% of preterm deliveries. In light of the rise in levels of glucocorticoids (GC) in amniotic fluid associated with preterm labor, in the present study we examined the effects of GC on the expression of major ECM proteins in cultures of amnion epithelial cells recovered after digestion of human term amnions. Amnion cells were maintained with and without 10(-7) mol/L dexamethasone (DEX), and levels of the ECM protein fibronectin (FN) were determined by enzyme-linked immunosorbent assay. DEX treatment reduced FN expression in amnion epithelial cells to 15-30% of control levels and reduced FN expression in placental cells to 30-50% of control levels. Conversely, DEX treatment weakly stimulated FN expression in chorion cell cultures. DEX treatment did not affect the total level of amnion cell protein, indicating that the effects of DEX in amnion cells did not result from a general reduction in protein synthesis. Cortisol and DEX reduced FN expression in amnion cells, with half-maximal effective concentrations of approximately 60 and 8 nmol/L, respectively. In immunoprecipitation studies, DEX treatment reduced FN and collagen III synthesis to 20% of control levels, suggesting that GC may coordinately reduce the synthesis of major ECM proteins in amnion cells. Similarly, DEX treatment reduced the levels of FN messenger ribonucleic acids in amnion cells to approximately 15% of control levels. DEX treatment also promoted a marked reduction in FN expression in amnion cells cultured in serum-free medium to 10-50% of control levels. Our results indicate that GC negatively regulate ECM protein expression in amnion epithelial cells, suggesting a potential role in the genesis of altered fetal membrane ECM protein expression associated with prematurely ruptured membranes.
Adult↗
Correlation of measured amnionic fluid volume to sonographic and magnetic resonance predictions.
OBJECTIVE: The purpose of this study was to compare the relationship between the actual amnionic fluid volume that was measured at delivery and magnetic resonance amnionic fluid volume determination, largest vertical pocket, and amnionic fluid index. STUDY DESIGN: Three hours before cesarean delivery, 80 women had sonographic measurement of the amnionic fluid index and the largest vertical pocket. Magnetic resonance imaging was then completed, and the magnetic resonance amnionic fluid volume was determined. At surgery, the amnionic fluid was collected. Pearson correlations were determined. Receiver operating characteristic curves were developed for each method as a measure of predictability for oligohydramnios. RESULTS: The correlations for the magnetic resonance amnionic fluid volume, amnionic fluid index, and largest vertical pocket to amnionic fluid volume was 0.84, 0.77, and 0.71, respectively. Magnetic resonance amnionic fluid volume has a statistically higher correlation than the largest vertical pocket ( P = .046). The 3 methods, however, are statistically comparable for identifying oligohydramnios. CONCLUSION: Magnetic resonance imaging is comparable with ultrasound evaluation for the prediction of oligohydramnios. Correlations to actual amnionic fluid volume are also comparable.
Adult↗
The identification and characterization of beta-adrenergic receptors in human amnion tissue.
With the use of [125I]iodocyanopindolol as a beta-receptor ligand, beta-receptors were identified and characterized in human amnion tissue. [125I]lodocyanopindolol was found to bind to a total particulate fraction prepared from amnion tissue obtained at term. At low concentrations of [125I]iodocyanopindolol, more than 80% of total [125I]iodocyanopindolol bound was at specific high-affinity sites and could be displaced by an excess of (+/-)-propranolol. The Kd and Bmax for binding of [125I]iodocyanopindolol to amnion beta-receptors were 10.1 +/- 1.1 pM and 46.8 +/- 3.2 fmol/mg protein, respectively. Analysis of the competition for binding to amnion beta-receptors between [125I]iodocyanopindolol and ligands that discriminated between beta 1- and beta 2-receptors revealed that the beta-receptors of human amnion were almost entirely of the beta 2-subtype. The density of beta-receptors found in the amnion at term was approximately three times that found early in the second trimester of gestation. The beta-receptors in human amnion appear to be functional since the in vitro exposure of amnion tissue pieces to isoproterenol (10(-5)M), resulted in a fivefold increase in the intracellular concentration of cyclic adenosine monophosphate. The presence of beta-receptors in the amnion is in keeping with the proposed importance of the catecholamines found in amniotic fluid in the regulation of prostaglandin production by the amnion.
Amnion↗
Transforming growth factor-beta inhibits prostaglandin production in amnion and A431 cells.
We studied the effect of transforming growth factor-beta (TGF-beta) on prostaglandin E2 (PGE2) production and mitogenesis in human amnion cells and compared the response in amnion cells with that in A431 cells. Both amnion cells and A431 cells respond to epidermal growth factor (EGF) with increased production of PGE2 whereas EGF promotes mitogenesis in amnion cells but not in A431 cells. In amnion cells, TGF-beta was not mitogenic, and did not alter the mitogenic response of cells to EGF. Treatment of amnion cells with TGF-beta did, however, cause a decrease in PGE2 production relative to untreated cells, although EGF stimulated PGE2 production was not attenuated. In A431 cells, TGF-beta acted to decrease PGE2 production relative to untreated cells and to attenuate the stimulation of PGE2 production effected by EGF. The inhibitory action of TGF-beta on PG production in amnion and A431 cells is contrary to the stimulation of PG production in mouse calvaria reported by others and is suggestive that the effect of TGF-beta on prostaglandin production, like its effect on growth, varies between different cell types. Inhibition of PG production by treatment of amnion or A431 cells with mefenamic acid did not alter thymidine incorporation into DNA in response to EGF; similarly, the addition of PGE2 or PGF2 alpha to culture media of amnion or A431 cells had no effect on mitogenesis (in the absence or presence of EGF). Based on these findings, we conclude that PG production and EGF action on proliferation (stimulation in amnion cells; inhibition in A431 cells) are dissociated.
Amnion↗
Glucocorticoids induce cytosolic phospholipase A2 and prostaglandin H synthase type 2 but not microsomal prostaglandin E synthase (PGES) and cytosolic PGES expression in cultured primary human amnion cells.
This study examines the regulation of major enzymes in prostaglandin E(2) (PGE(2)) synthesis by glucocorticoids in separate cultures of human amnion epithelial and fibroblast cells at term. Cytosolic phospholipase A(2) (cPLA(2)), cytosolic PGES (cPGES), and microsomal PGES (mPGES) mRNA were expressed at similar levels in both cell types, whereas a greater prostaglandin H synthase type 2 (PGHS-2) mRNA expression was observed in amnion fibroblasts than in epithelial cells. Amnion fibroblasts produced 50-fold more PGE(2) per cell than epithelial cells. Dexamethasone (0.01-1 microM) increased PGE(2) production in amnion fibroblasts in a concentration-dependent manner but did not affect PGE(2) production in amnion epithelial cells. Both mRNA and protein expression of cPLA(2) and PGHS-2 but not cPGES and mPGES were increased in a dose-dependent manner by dexamethasone (0.01-1 microM) in amnion fibroblasts. Induction of cPLA(2) and PGHS-2 mRNA by dexamethasone was blocked by RU486. Dexamethasone did not affect PGHS-2, cPGES, and mPGES mRNA expression in amnion epithelial cells. In conclusion, amnion fibroblasts express a higher level of PGHS-2 mRNA and produced more PGE(2) per cell than amnion epithelial cells at term of human pregnancy. Glucocorticoids increase PGE(2) production only in the amnion fibroblasts mainly through induction of cPLA(2) and PGHS-2 expression.
Amnion↗
Smad5 determines murine amnion fate through the control of bone morphogenetic protein expression and signalling levels.
Smad5 is an intracellular mediator of bone morphogenetic protein (Bmp) signalling. It is essential for primordial germ cell (PGC) development, for the development of the allantois and for amnion closure, as demonstrated by loss of Bmp signalling. By contrast, the appearance of ectopic PGC-like cells and regionalized ectopic vasculogenesis and haematopoiesis in thickened Smad5(m1/m1) amnion are amnion defects that have not been associated with loss of Bmp signalling components. We show that defects in amnion and allantois can already be detected at embryonic day (E) 7.5 in Smad5 mutant mice. However, ectopic Oct4-positive (Oct4(+)) and alkaline phosphatase-positive (AP(+)) cells appear suddenly in thickened amnion at E8.5, and at a remote distance from the allantois and posterior primitive streak, suggesting a change of fate in situ. These ectopic Oct4(+), AP(+) cells appear to be Stella negative and hence cannot be called bona fide PGCs. We demonstrate a robust upregulation of Bmp2 and Bmp4 expression, as well as of Erk and Smad activity, in the Smad5 mutant amnion. The ectopic expression of several Bmp target genes in different domains and the regionalized presence of cells of several Bmp-sensitive lineages in the mutant amnion suggest that different levels of Bmp signalling may determine cell fate. Injection of rBMP4 in the exocoelom of wild-type embryos can induce thickening of amnion, mimicking the early amnion phenotype in Smad5 mutants. These results support a model in which loss of Smad5 results paradoxically in gain of Bmp function defects in the amnion.
Alleles↗
Amnion membrane epithelial cells express class I HLA and contain class I HLA mRNA.
Amnion epithelial cells in membranes from term deliveries, which have been reported not to express histocompatibility Ag, were evaluated for HLA by using an avidin-biotin immunoperoxidase staining system and for class I HLA mRNA by Northern blotting and in situ hybridization. There were three major findings from these studies. 1) Amnion cells frequently expressed class I HLA. Three mAb to monomorphic determinants of class I HLA were used: 61D2, PA2.6, and W6/32. 61D2 identified 1 of 8 fresh amnion membranes as class I positive whereas PA2.6 identified 4/8 and W6/32 identified 5/8. 2) Amnion cells contained class I HLA mRNA. RNA extracted from amnion membranes hybridized to a class I HLA probe (pHLA1.1) in Northern blotting. In situ hybridization procedures with pHLA1.1 showed that essentially all amnion cells contained class I HLA mRNA. 3) Levels of class I HLA mRNA in amnion cells could be modulated. Exposure of amnion explants to medium containing IFN-gamma enhanced levels of class I HLA mRNA in amnion cells, whereas epidermal growth factor diminished those levels. The results suggest that amnion cells transcribe class I HLA genes and are capable of synthesizing class I H chains but that expression may be modulated by extrinsic regulatory molecules.
Amnion↗