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PubMed1998

Induction of oxytocin receptor gene expression in rabbit amnion cells.

Oxytocin (OT)-stimulated PGE2 release by rabbit amnion is enhanced by the up-regulation of oxytocin receptors (OTR), which increase about 200-fold at the end of pregnancy. As recent studies have shown that PGs are essential for parturition, the rise in amnion OTR and associated PGE2 synthesis are probably essential for labor initiation. The present work was directed toward understanding the mechanisms of OTR up-regulation. Levels of agents that stimulate adenylyl cyclase activity and cortisol are increased in amniotic fluid at the end of pregnancy. Addition of either forskolin or cortisol to cultured amnion cells caused an increase in OTR ligand-binding sites and steady state OTR messenger RNA (mRNA) levels. Forskolin treatment elevated OTR mRNA levels rapidly, but transiently, whereas cortisol's effects were slower and sustained. Actinomycin or cycloheximide, added 3 h after forskolin, led to a sustained elevation in OTR mRNA levels, suggesting that forskolin increases the activities of OTR mRNA-destabilizing factors along with increasing OTR mRNA concentration. Cortisol did not appear to affect OTR mRNA stability. Measurement of OTR mRNA transcription rates showed that forskolin's effects were maximal within 1 h of treatment. In contrast, cortisol-induced transcription was not apparent until 8 h. The effects of forskolin and cortisol on OTR gene transcription were synergistic. Thus, the increase in OTR mRNA levels occurring after either forskolin or cortisol treatments is the result of induction of OTR gene expression, but the effects of the two agents appear to occur at separate sites.

Amino Acid Sequence↗
PubMed2005

15-Deoxy-{delta}12,14-prostaglandin j2 inhibits interleukin-1{beta}-induced nuclear factor-{kappa}b in human amnion and myometrial cells: mechanisms and implications.

Proinflammatory cytokines and prostaglandins play key roles in term and preterm human labor. The expression of the prostaglandin synthetic enzyme cyclooxygenase (COX)-2 and cytokines IL-1beta and IL-8 increases within the uterus at the time of labor, and each is regulated by the transcription factor nuclear factor-kappaB (NF-kappaB). In addition to its role in driving inflammation, COX-2 may also synthesize 15-deoxy-Delta (12, 14)-prostaglandin J(2) (15d-PGJ(2)), an antiinflammatory cyclopentenone prostaglandin (cyPG), which acts in some cells as an agonist of peroxisome proliferator-activated receptors (PPARs). We found that PPARalpha and -gamma proteins are expressed in both amnion epithelial and myometrial cells, but synthetic PPAR agonists could not inhibit NF-kappaB activity or COX-2 expression. 15d-PGJ(2) inhibited NF-kappaB activity and COX-2 expression in both cell types. This was unaffected by a PPAR antagonist and could be mimicked by the cyPG PGA(1) but not 9,10-dihydro-15d-PGJ(2) in which the cyclopentenone ring is disrupted. This shows that, in amnion and myometrium, inhibition of NF-kappaB activity and COX-2 expression by 15d-PGJ(2) is independent of PPARs and requires the cyclopentenone ring. We further show that 15d-PGJ(2) acts at multiple levels in the NF-kappaB pathway: blocking inhibitor of kappaBalpha degradation by repressing inhibitor of kappaB kinase activation and the 26S proteasome and also repressing NF-kappaB DNA binding and phosphorylation. Our data suggest that PPARs are unlikely to play a role in the regulation of either NF-kappaB or COX-2 in human amnion and myometrium. Targeting of NF-kappaB is a potential therapeutic strategy in preterm labor. PPAR agonists are unlikely to be effective in this context, but cyPGs may have potential.

Amnion↗
PubMed1988

Stimulation of human amnion prostaglandin E2 production by activators of protein kinase-C.

We tested the possibility that the activation of protein kinase-C by the tumor-promoter phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or diacylglycerol stimulates the production of prostaglandin E2 (PGE2) by the amnion. Confluent primary cultures of human amnion epithelial cells were adapted to serum-free medium and treated with the agonists for up to 8 h. Cumulative PGE2 output in the medium was measured by RIA. TPA, a potent activator of protein kinase-C, stimulated basal PGE2 output from less than 50 pg/well.5 h to 3 ng/well.5 h (P less than 0.01) in a time- and dose-dependent manner. 4-Methoxy-TPA, a weak tumor promoter derivative of TPA, was ineffective when tested in the same concentration range as TPA (1 nmol/L to 1 mumol/L). Neither calcium ionophore A23187 (20 nmol/L) nor arachidonate (1 mumol/L) stimulated PGE2 output alone, but each agonist potentiated the effect of TPA as much as 5-fold (P less than 0.01). 1,2-Dioctanoyl-sn-glycerol stimulated PGE2 output 4- to 7-fold (P less than 0.05), and this effect was potentiated by Ca ionophore and arachidonate. Studies involving actinomycin-D and cycloheximide indicated that the stimulatory effect of TPA was dependent on RNA synthesis during the first 60 min and on protein synthesis during the entire length of the phorbol ester treatment period (300 min). TPA was also able to stimulate PGE2 production after irreversible inactivation of PG endoperoxide synthase activity with acetylsalicylic acid. These results suggest that activation of protein kinase-C in amnion cells increases the de novo synthesis of the PG endoperoxide synthase enzyme in a RNA synthesis-dependent manner. Elevated intracellular calcium levels contribute to the stimulation apparently by increasing the availability of endogenous arachidonate for subsequent conversion to PGE2.

Amnion↗
PubMed1988

Glucocorticoids stimulate prostaglandin synthesis in human amnion cells by a receptor-mediated mechanism.

Prostaglandin E2 (PGE2) synthesis by human amnion increases with the onset of labor and is thought to participate in the initiation and maintenance of parturition. Since cortisol levels increase in amniotic fluid in late pregnancy, we studied the effects of glucocorticoids on cultured term human amnion cell PGE2 output. In 24-h studies, the synthetic glucocorticoid dexamethasone stimulated basal PGE2 output 2-fold over control levels at 16-500 nmol/L. PGE2 output was dramatically stimulated (greater than 10-fold) when, after dexamethasone pretreatment, the cells were incubated with calcium ionophore A23187 or arachidonic acid (AA) for 2 h. Maximum effects were achieved at 31 nmol/L dexamethasone. Basal PGE2 output was stimulated at 12 h of dexamethasone treatment, whereas A23187- or AA-stimulated PGE2 output was enhanced after 3-6 h of dexamethasone pretreatment. Cortisol (50 and 500 nmol/L) also enhanced basal and stimulated PGE2 output, while dehydroepiandrosterone sulfate, 17 beta-estradiol, and progesterone were ineffective. The glucocorticoid receptor antagonist RU 38486 attenuated dexamethasone-enhanced basal and stimulated PGE2 output. Dexamethasone pretreatment had no effect on basal or stimulated PGE2 output from cultured term chorion cells, suggesting tissue specificity. We conclude that glucocorticoids specifically enhance PGE2 output from cultured amnion cells via a receptor-mediated mechanism. We speculate that the action of glucocorticoids is to increase the capacity of the cells to convert AA to PGE2.

Amnion↗
PubMed1990

Arachidonic acid release from cultured human amnion cells: the effect of dexamethasone.

Glucocorticoids inhibit prostaglandin (PG) synthesis in several cell types, presumably by inhibiting arachidonic acid (AA) deacylation from phospholipids. We studied the effects of glucocorticoids on cultured term human amnion cell AA release. Confluent monolayer cultures of amnion cells were adapted to serum-free medium, and phospholipids were labeled for 18 h with [14C]AA. The calcium ionophore A23187 (0.2-5.0 mumol/L) stimulated [14C]AA release (up to 2.2-fold) in a dose- and time-dependent manner. The apparent sources of the liberated [14C]AA were phosphatidylcholine and phosphatidylethanolamine. Pretreatment for 24 h with the synthetic glucocorticoid dexamethasone (0.1-1000 nmol/L) significantly inhibited (P less than 0.01) basal (unstimulated) [14C]AA release by 69% in subsequent 1-h experiments. The sole apparent source of free [14C]AA during this inhibitory state was phosphatidylethanolamine. Dexamethasone pretreatment slightly inhibited (13%; P less than 0.05) calcium ionophore-stimulated [14C]AA release; however, it was still 3.8-fold greater than basal release, suggesting that the glucocorticoid effect on stimulated AA release was not biologically relevant. Further characterization of the glucocorticoid effect revealed that preincubation of the cultures with dexamethasone for as little as 20 min inhibited basal [14C]AA release. Furthermore, studies involving actinomycin-D and cycloheximide demonstrated that inhibition of RNA and protein synthesis failed to block the glucocorticoid inhibition of basal AA liberation. The glucocorticoid receptor antagonist RU 38486, alone or in the presence of dexamethasone, also inhibited unstimulated [14C]AA release. Cortisol, dehydroisoandrosterone sulfate, 17 beta-estradiol, and progesterone all inhibited basal [14C]AA liberation. We conclude that glucocorticoids inhibit unstimulated AA release from cultured amnion cells, but do not prevent calcium ionophore from stimulating a large increase in AA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Amnion↗
PubMed2001

Maintenance of the differentiated type II cell characteristics by culture on an acellular human amnion membrane.

We have developed a Culture system for guinea pig alveolar type II cells using an epithelium-denuded human amnion membrane as a substratum. The differentiated morphology was maintained for 3 wk by both air-interface feeding and immersion feeding when type II cells were cultured on the basement membrane side of the amnion with fibroblasts on the opposite side (coculture). Functionally high levels of surfactant protein B (SP-B) and C (SP-C) messenger ribonucleic acids (mRNAs) were expressed even after the 3-wk cultivation and surfactant protein A mRNA was detected on day 10 of the culture. The differentiation was also maintained when fibroblasts were cultured on lower chambers of the culture plates (separate culture). In contrast, culture of type II cells without fibroblasts (monoculture) could not preserve the mature morphology. When the monoculture was supplemented with keratinocyte growth factor or hepatocyte growth factor, a monolayer of rather cuboidal type II cells with apical microvilli was maintained. However, the percent area of lamellar bodies in these cells was significantly less than that in freshly isolated type II cells, and mRNA expressions of SP-B and SP-C were also considerably suppressed. These findings suggest that other growth factors or combinations of these factors are necessary for the maintenance of the differentiated phenotype. As substratum, a permeable collagen membrane or a thin gel layer of Engelbreth-Holm-Swarm mouse sarcoma extracts did not preserve the mature characteristics. This culture system using an acellular human amnion membrane may provide novel models for research in type II cells.

Amnion↗
PubMed1984

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)

Amnion↗
PubMed1993

Studies on the action of dexamethasone on prostaglandin production by freshly dispersed amnion cells.

The human amnion may be an important source of prostaglandins (PGs) during pregnancy and possibly labor. Glucocorticoids stimulate PG production in confluent amnion cell cultures, but in freshly dispersed cells they inhibit PG production. The purpose of the present study was to determine if this inhibitory effect occurred at the level of arachidonic acid release from lipids. Cells were labeled with radioactive arachidonate and the release of radioactivity was measured in the presence or absence of dexamethasone. No significant effect of dexamethasone treatment was observed. The possibility that glucocorticoid treatment inhibited the release of arachidonate from a specific species of phospholipid was also examined. However, no difference was found in the distribution of arachidonate between lipids isolated from glucocorticoid-treated and untreated cells. Furthermore, dexamethasone treatment did not alter the lipocortin 1 and 2 content of dispersed cells, determined following sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting. These studies indicate that the inhibition of prostaglandin production by dispersed amnion cells by glucocorticoids most likely occurs at a point distal to arachidonic acid release.

Amnion↗
PubMed1987

Immunohistochemical localization of relaxin, prolactin and prostaglandin synthase in human amnion, chorion and decidua.

Relaxin, prolactin and prostaglandin synthase were localized by the avidin-biotin immunoglucose oxidase method in human amnion, chorion and decidua. Specimens from ten normal spontaneous deliveries and four elective Caesarean section deliveries with no labour were compared. Relaxin was found more consistently in the cells of the chorionic cytotrophoblast than in the cells of the parietal decidua adherent to the fetal membranes. Only half the tissues after spontaneous delivery contained positive relaxin-stained cells, whereas all the tissues from elective Caesarean sections contained cells positively stained with antiserum to relaxin. In both series of tissues prolactin was localized predominantly in the parietal decidual cells and was very infrequently found in the chorionic cytotrophoblast. Polyclonal antiserum to prostaglandin synthase was used to identify those cells producing prostaglandin in amnion, chorion and decidua. The cells of the amnion and chorion showed positive immunolocalization with no differences between tissues collected before or after labour. Double immunostaining using avidin-biotin immunoperoxidase for prolactin, followed by avidin-biotin immunoglucose oxidase for prostaglandin synthase, produced identical results in the same series of tissues examined with the single-staining method.

Amnion↗
PubMed2006

Mechanisms regulating prostaglandin H2 synthase-2 mRNA level in the amnion and chorion during pregnancy.

Increasing prostaglandin H(2) synthase (PGHS)-2 expression in the fetal membranes is implicated in the production of prostaglandins (PGs) that stimulate labour. We have determined the activity of the PGHS-2 gene in the amnion and chorion throughout gestation and defined the contribution of transcriptional and post-transcriptional mechanisms to the increase of PGHS-2 mRNA levels. We also measured PGHS-1 mRNA abundance to assess the participation of the two isoenzymes in fetal membrane PG-production during pregnancy. Amnion and chorion were collected from non-labouring women at 10-19 weeks (early), at 28-36 weeks (preterm) and at term (37-41 weeks). We determined PGHS-1 and -2 mRNA abundance and assessed PGHS-2 gene activity by measuring PGHS-2 heterogeneous nuclear RNA levels using real-time RT-PCR. PGHS-2 gene activity and mRNA levels were up-regulated in both tissues with advancing gestation. Path analysis demonstrated that the PGHS-2 mRNA up-regulation involved both transcriptional and post-transcriptional components. PGHS-2 mRNA abundance increased 9-11 fold between the early (10-19 weeks) and preterm (28-36 weeks) groups and remained high at term. The underlying mechanism was predominantly transcriptional in the amnion and post-transcriptional in the chorion. PGHS-1 mRNA expression precipitously decreased between early gestation and term. Thus, PGHS-2 mRNA abundance is up-regulated well in advance of term and is not a trigger for labour. There is a switch in PGHS mRNA expression during pregnancy with PGHS-1 dominating in the early period and PGHS-2 dominating at term.

Amnion↗
PubMed1983

Human amnion in the treatment of chronic ulceration of the legs.

A prospective study to evaluate the efficacy of human amniotic membrane dressings in the treatment of chronic leg ulcers was conducted on 15 patients. Patients with two ulcers were selected. One ulcer was treated with human amnion and the other, treated with standard dressings, served as a control. The rate of healing of the two ulcers was observed and compared. Chronic ulcers of post-phlebitic, post-irradiation and post-burn origin responded to treatment with human amnion and healed more rapidly than the control ulcer. Ulcers associated with rheumatoid arthritis and vasculitis showed no improvement. It was observed that all ulcers treated with human amnion quickly became pain-free.

Aged↗
PubMed1982

Ultrasonic demonstration of the amnion.

The amnion can be visualized in most pregnancies before the 12th week. It appears as a thin membrane separating the amniotic cavity, which contains the fetus, from the extra-embryonic coelom and the secondary yolk sac. In a prospective study of 32 women in the first 12 weeks of pregnancy, the amnion was demonstrated ultrasonographically in 27 (84 per cent). The embryonic origin of the amnion and possible difficulties in its demonstration by ultrasound are described.

Amnion↗
PubMed1997

A comparative study of gut suture, human amnion collagen, bovine skin collagen and Vicryl suture implants in rats.

This study compares the persistence and histological characteristics of gut suture with those of human amnion collagen, bovine collagen, and Vicryl suture implants in rats. Gut suture and human amnion collagen more resembled living tissue than did bovine collagen and were characterized by their cellularity and the presence of numerous capillaries. The Vicryl suture implants were quickly absorbed. Picrosirius polarization revealed the synthesis of host collagen by rat fibroblasts which immigrated into the gut suture and human amnion collagen implants. The authors suggest the potential of gut suture as a soft tissue substitute to improve linear skin contour deficits.

Absorbable Implants↗
PubMed2000

Female urethral reconstruction with amnion grafts.

BACKGROUND: About 1-5% of female babies are born with Müllerian duct abnormalities such as Mayer-Rokitansky-Küster-Hauser syndrome, urogenital sinus, and cloacal malformation. In some intersex cases the urethra and vagina both empty into a urogenital sinus. One major issue in single-stage surgical reconstruction of large urethral defects is tissue availability. AIM: To investigate the usefulness of amnion grafts in female urethral reconstruction. METHODS: This is a prospective cohort study describing the use of amnion grafts for urethral reconstruction in 8 patients with ambiguous genitalia associated with low or mid-portion urethrovaginal confluence or vaginal agenesis with low external urethral meatus implantation. RESULTS: The procedure was felt to be easy, quick and effective for appropriate restoration of both the function and the cosmetics of the lower urogenital tract. CONCLUSIONS: Amnion grafts add a valuable option to the surgical armamentarium and offers potential advantages for urogenital reconstructive surgery.

Adolescent↗
PubMedDate not supplied

[Conduit drainage and preserved amnion in pathologies of the cornea concomitant with glaucoma].

The authors improved the anterior-chamber bypass technique implemented simultaneously with reconstructive penetrating keratoplasty or with trabeculotomy in order to enhance the efficiency of antiglaucomatous drainage surgeries in organic lesions of the anterior segment of the eye combined with active inflammatory processes in it and concomitant with secondary glaucoma. The use of conduit drainage was supplemented with wrapping the distal end with conserved amnion, which prevented the postoperative obstruction of drainage or its heading in the outward direction. Amnion, exceeding the size of the scleral flap, was placed in trabeculotomy with active inflammatory signs between scleral strata, thus, preventing an excessive postoperative scarring. A total of 45 patients were operated on with the follow-up reaching 3 years. The efficiency of antiglaucomatous interventions made up 88-93% of cases. The suggested new drainage techniques with conserved amnion can be successfully used surgeries combined with keratoplasty as well as in independently in secondary glaucomas of various etiologies and in primary refractive glaucoma.

Adolescent↗
PubMed1992

Decrease of cellular growth potential in "in vitro" culture of amnions with premature rupture of membranes.

The "in vitro" cellular growth of 8 amniotic membranes from preterm deliveries with premature rupture of membrane (PROM) in absence of risk factors as cervical or vaginal infection (microbiologic negativity), cervical incontinence and other mechanical factors, was compared with cellular growth of 9 amnions from preterm deliveries without PROM. Amniotic membranes were set up in the Eagle basal medium with Earle salts and heat-inactivated fetal bovine serum (10%), gentamicin 50 micrograms/ml and amphotericin B 0.5 micrograms/ml. The results suggested that the growth potential of the cells (epithelial cells and fibroblasts) obtained from amnions with PROM was lower than that of cells obtained from amnions without PROM. We postulated that the premature rupture of membranes in patients without risk factors for PROM, would be conditioned by an intrinsic decrease of cellular growth potential.

Amnion↗
PubMed2004

[Effect of human acellular amnion membrane on tendon adhesion in rat].

OBJECTIVE: To investigate the effects of human acellular amnion membrane on SD rat tendon adhesion and to obtain the experimental data for clinical application in preventing postoperative tendon adhesion. METHODS: The tendons of 28 adult SD rats hindlimb were cut and sutured. The tendons of left hindlimb were encapsulated by human accellular amnion membrane as the experimental group and the ones of the other side were not encapsulated as control group. The rats were killed 1, 2, 4, 6, 8 and 12 weeks after operation. The results were evaluated grossly and histologically. RESULTS: There were no differences in healing of injury tendon and inflammatory response between the two groups. The anatomical and histological results showed the experimental group had less adhesion than the control group (P < 0.05). CONCLUSION: Human acellular amnion membrane can prevent adhesion of tendon without affecting tendon healing and is an optimal biological material to prevent tendon adhesion.

Amnion↗
PubMed1991

Superoxide anion increases intracellular pH, intracellular free calcium, and arachidonate release in human amnion cells.

We determined the effects of superoxide anion, produced by addition of xanthine oxidase to hypoxanthine, on the intracellular pH (pHi) and intracellular free calcium concentration ([Ca2+]i) and release of arachidonate in human cultured amnion cells. Superoxide anion induced a prompt increase of pHi and subsequent increase of [Ca2+]i. The evoked pHi was inhibited by pretreatment with anion channel blockers but not affected by omission of extracellular Na+ or addition of amiloride. The increase of [Ca2+]i was inhibited significantly by the absence of extracellular calcium or by the addition of a calcium channel blocker, cobalt. NH4Cl, which can generally increase pHi, also increased [Ca2+]i of amnion cells. But the increase of [Ca2+]i induced by the NH4Cl was significantly less than that induced by the amount of superoxide anion causing a similar increase in pHi. These results show that superoxide anion, crossed through anion channel in membrane, increased [Ca2+]i at least partially via increase of pHi and that the calcium mobilization was dependent on both extracellular and intracellular sources. Superoxide anion induced the release of arachidonate in a dose-dependent manner and this induction was inhibited by omission of extracellular calcium. These data suggest that the release of arachidonate was dependent on the increase of [Ca2+]i. We also determined the viability of cells in the presence of superoxide anion by flow cytometry. Superoxide anion at the levels used in these experiments did not change the percentage of viable cells. These findings suggested that superoxide anion may regulate biological functions in amnion cells via pHi, [Ca2+]i mobilization, and the release of arachidonate without damaging the cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗