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PubMed1988

Oxytocin activates the inositol-phospholipid-protein kinase-C system and stimulates prostaglandin production in human amnion cells.

It has been postulated that fetal hormonal signals act upon amnion to trigger labor via prostaglandin (PG) production. Human amnion epithelial cell cultures were established to test the effects of potential activators of the inositol phospholipid-protein kinase-C effector system on intracellular inositol phosphate turnover, intracellular free calcium ([ Ca2+]i), and PGE2 production. Oxytocin provoked 3-, 2.5-, and 4-fold increases in inositol triphosphate, inositol bisphosphate, and inositol monophosphate, respectively. [Ca2+]i, measured with the fluorescent dye fura-2, was stimulated by oxytocin and vasopressin (oxytocin greater than vasopressin) in a dose-dependent manner. The [Ca2+]i transient produced by oxytocin reached a peak in 15 sec, followed by a slow return to baseline over 10 min. Preincubation with phorbol 12-myristate-13 acetate (PMA) markedly blunted the oxytocin-induced transient. No [Ca2+]i transient was seen with leukotrienes, PG, serotonin, angiotensin, or alpha- or beta-adrenergic agents. PGE2 production increased 30- to 50-fold with phospholipase-C and PMA, and 10-fold with the calcium ionophore A23187. Oxytocin and vasopressin produced 10- and 3-fold PGE2 increases, respectively. Increased PGE2 production induced by PMA, oxytocin, and A23187 was first seen after 8 hr of incubation and reached maximal levels at 24 h. Minimal PGE2 stimulation occurred with agents that produced no [Ca2+]i transient. Direct activators of the inositol phospholipid-protein kinase-C system in human amnion induce large increases in PGE2 in human amnion cells. Oxytocin and vasopressin are hormonal activators of this system in these cells, as demonstrated by their effects on inositol phosphate turnover and [Ca2+]i. These hormones also increase PGE2 production and may influence labor by stimulating PGE2 production in amnion through the inositol phospholipid-protein kinase-C system.

Amnion↗
PubMed1993

Up-regulation of oxytocin receptors in rabbit amnion by glucocorticoids: potentiation by cyclic adenosine 3',5'-monophosphate.

Oxytocin (OT) receptors (OTR) in rabbit amnion increase more than 200-fold at the end of gestation. In the present report, we studied the basis of this up-regulation. Incubation of amnion cells with cortisol (20 nM) for 24 h increased the amount of 125I-labeled OT antagonist bound by 16- to 18-fold. The effects of cortisol were dose and steroid dependent. Administration of glucocorticoid to pregnant does also increased the concentration of OTRs in amnion. The effects of cortisol in vitro were potentiated by the addition of forskolin (50 microM), so that OTR number increased by as much as 182 times. The effects of cortisol and forskolin, either separately or in combination, were inhibited by activation of protein kinase-C or coincubation with transforming growth factor-alpha (10 nM). Cyclosporin-A (5 microM) selectively inhibited cortisol-induced rises in the OTR concentration. The addition of cortisol to amnion cells increased OT-stimulated prostaglandin E2 (PGE2) release almost 100-fold; the combination of forskolin and cortisol increased the PGE2 response to OT about 5600 times. Judging from the greater effects on PGE2 release, these results suggest that forskolin and cortisol up-regulate the signal response mechanism to OT as well as the OTR concentration. The findings show that changes occurring in the amnion in vivo can be mimicked in vitro, and they elucidate the mechanism of up-regulation of OTR concentrations.

Amnion↗
PubMed1985

Epidermal growth factor binding to human amnion, chorion, decidua, and placenta from mid- and term pregnancy: quantitative light microscopic autoradiographic studies.

All of the cell types, but not noncellular elements, found in amnion, chorion, decidua, and placenta of mid- and term pregnancy contained numerous silver grains after incubation with 1 nM [125I]epidermal growth factor ([125I]EGF). These grains completely disappeared when excess unlabeled EGF, but not unlabeled insulin, was added with [125I]EGF, suggesting the presence of specific EGF receptors. Light cells of amnion contained more EGF receptors than dark cells of amnion, and the number of light cells decreased from mid- to term pregnancy. Numerous syncytiotrophoblasts containing a greater number of receptors than darkly stained cells in connective tissue were found in chorion from midpregnancy. The chorionic syncytiotrophoblasts were considerably reduced at term. Dark cells of decidua contained more receptors than light cells of decidua, and these cell numbers did not change during pregnancy. Placental syncytiotrophoblasts contained the EGF receptors. At mid- and term pregnancy, placenta contained the highest number of EGF receptors, followed by chorion greater than decidua greater than amnion. The receptor number in all tissues was higher at mid-compared to term pregnancy. A decrease in number of cells as well as a decrease or fewer receptors per cell during pregnancy may explain the tissue and mid- vs. term pregnancy differences. The higher number of EGF receptors in amnion, chorion, decidua, and placenta at midpregnancy, at a time when the maternal and fetal blood EGF levels are at their peak, suggests that EGF may exert maximal biological effects on the feto-placental unit at midpregnancy.

Amnion↗
PubMed2002

The in vivo control of prostaglandin H synthase-2 messenger ribonucleic acid expression in the human amnion at parturition.

Prostaglandin H synthase-2 (PGHS-2) activity and mRNA rise in the human amnion at late gestation, contributing to the increase in intrauterine PG production crucial for labor and delivery. In the present investigation we have determined the mechanism that controls amniotic PGHS-2 mRNA levels in vivo at term parturition. Amnion membranes were collected after elective cesarean section (n = 20), and after spontaneous labor (n = 20). PGHS-2 relative gene transcription rates were determined by transcriptional run-on, and PGHS-2 mRNA and heterogeneous nuclear RNA (hnRNA) relative abundance were measured by quantitative real-time RT-PCR. The PGHS-2 mRNA degradation rate was determined by incubating amnion in the presence of the transcription inhibitor 5,6-dichlorobenzimidazole riboside. The dynamics of PGHS-2 hnRNA and mRNA abundance were characterized in 0- to 24-h tissue incubations. The PGHS-2 relative gene transcription rate was a significant (P < 0.05) predictor of PGHS-2 hnRNA and mRNA abundance, and PGHS-2 hnRNA was also a predictor (P < 0.01) of PGHS-2 mRNA levels both before and after labor. Interestingly, even though PGHS-2 gene activity remained unchanged, PGHS-2 mRNA abundance increased with labor and displayed constitutive stability before and after labor. PGHS-2 mRNA levels spontaneously increased by 400% (P < 0.01) upon incubation for 24 h, whereas the transcription rate dropped by 95% during the first 2 h, then rebounded significantly between 6-24 h. Thus, PGHS-2 mRNA abundance is transcriptionally controlled in term amnion. Labor does not increase PGHS-2 gene activity or mRNA stability. The PGHS-2 gene is probably induced before labor by a factor(s) originating in the amnion membrane, and the resulting stable mRNA accumulates progressively in the tissue throughout labor and delivery.

Amnion↗
PubMed1999

The effect of cytokines on parathyroid hormone-related protein (PTH-rP) production in human amnion cells.

In the present study, the effects of various cytokines on parathyroid hormone-related protein (PTH-rP) production and PTH-rP mRNA expression in human amnion cells were studied. Immunoreactive (ir) PTH-rP was measured by immunoradiometric assay and the expression of PTH-rP mRNA was determined by Northern blot analysis. The addition of interleukin-1beta (IL-1beta, 10 ng/ml) and IL-6 (10 ng/ml) in culture medium for 24 hours resulted in a significant increase in ir-PTH-rP levels by 1.5 and 1.6 fold, respectively. The effects of these agents were dose dependent. In contrast, IL-2 (10 ng/ml) and IL-8 (10 ng/ml) showed no effect on the production of ir-PTH-rP from amnion cells. Treatment with IL-1beta or IL-6 for 6 hours increased the expression of PTH-rP mRNA in amnion cells. The stimulatory effect of IL-1beta was reduced by IL-1 receptor antagonist (IL-1Ra) in a dose dependent manner. Both tetradecanoyl phorbol acetate (TPA), and forskolin increased PTH-rP mRNA levels and the PTH-rP production in amnion cells, and the effect of TPA was much greater than that of forskolin. The findings of the present study suggest of the participation of inflammatory cytokines for the regulation of PTH-rP production in human amnion cells.

Amnion↗
PubMed1999

Labour-associated changes in the regulation of production of immunomodulators in human amnion by glucocorticoids, bacterial lipopolysaccharide and pro-inflammatory cytokines.

Parturition is associated with changes in the production of inflammatory mediators by gestational tissues. An explant system was established to study the change in response of human amnion to various regulating factors during labour. Disks of tissue (6 mm) were excised from amnion membranes obtained either at term by Caesarian section before labour (n = 5-6) or after spontaneous vaginal delivery (n = 3-7). After 24 h equilibration in media, the tissues were treated with interleukin 1 beta (10 ng ml-1), tumour necrosis factor alpha (100 ng ml-1), lipopolysaccharide (5 micrograms ml-1) and dexamethasone (1 mumol l-1) or an appropriate vehicle control for 24 h (n = 3 wells per treatment). Media were harvested and interleukin 10, interleukin 6 and prostaglandin E2 concentrations were determined by immunoassay. In tissues taken both before and after the onset of labour, basal interleukin 10 production by amnion explants was near to the limit of detection. Basal production rates of PGE2 by amnion explants were significantly higher (P < 0.0012; Mann-Whitney U test) in tissues taken during labour than in tissues taken before the onset of labour, while interleukin 6 production was not significantly altered by labour. Production rates of interleukin 6 and prostaglandin E2 were significantly increased by interleukin 1 beta, tumour necrosis factor alpha and lipopolysaccharide in explants from tissues taken during and before labour, while the responsiveness of interleukin 10 production to these treatments was inconsistent. Dexamethasone had no effect on interleukin 6 production by amnion explants, but significantly inhibited prostaglandin E2 production, although this inhibition was approximately 30% lower in tissues obtained after the onset of labour. These results support the presence of inflammatory positive feedback cycles, coincident with a deficiency of an anti-inflammatory factor within gestational tissue, which may be involved in the progression or maintenance of labour.

Adjuvants, Immunologic↗
PubMed1996

Expression of prostaglandin G/H synthase-1 and -2 in ovine amnion and placenta following glucocorticoid-induced labour onset.

Parturition in the sheep is preceded by an increase in the synthesis of prostaglandins by intrauterine tissues. Prostaglandin G/H synthase (PGHS) is the central enzyme involved in prostanoid production. Its expression is enhanced during late gestation in the ewe. Recent studies have identified two PGHS isozymes, termed PGHS-1 and PGHS-2. The labour-associated expression of the two isozymes of PGHS in the sheep has not been characterized. This study investigated the changes in expression of immunoreactive PGHS-1 and PGHS-2 in ovine amnion and placenta following glucocorticoid-induced labour. Ewes underwent surgery to implant fetal and maternal vascular cannulae and uterine electromyogram electrodes between 118 and 125 days of gestation. Fetal sheep were administered either the glucocorticoid betamethasone (n = 5) or saline (control n = 6) by direct transabdominal intrafetal injection. Ewes from the betamethasone-injected group were killed in the first stage of labour as indicated by uterine electromyographic activity. Ewes from the saline-injected group were killed at the same time to obtain age-matched control tissue. The time taken to euthanasia following induced-labour onset in the glucocorticoid-injected animals was 56.6 +/- 0.8 h post-injection. Plasma endocrine profiles in the maternal and fetal circulation following glucocorticoid injection were comparable to those observed following normal spontaneous delivery. At post-mortem, amnion and cotyledons were collected in liquid N2 and stored at -70 degrees C. Solubilized tissue extracts were prepared and analysed by Western blots using polyclonal antibodies to PGHS-1 and PGHS-2 isozymes. Fetal amnion contained PGHS-1 isozyme at day 133 of gestation, as demonstrated in the saline-injected animals. Slightly higher PGHS-1 immunoreactivity was observed following induced-labour onset, although this did not reach statistical significance (P > 0.05). PGHS-2 enzyme was not detectable in amnion. PGHS-2 expression was also not induced following labour onset. In contrast, PGHS-2 demonstrated enhanced expression following glucocorticoid-induced labour in ovine cotyledon. This tissue contained PGHS-1 enzyme, but immunoreactive levels were minimal and demonstrated limited regulation at labour. These data suggest that the previously reported rise in placental PG production at term in the sheep is predominantly due to increased expression of the PGHS-2 isozyme. This suggests that PGHS-2 contributes to PG production at term labour in sheep or is induced by the mechanisms controlling ovine parturition. PGHS-1 isozyme is produced constitutively in ovine amnion and may contribute to the gestational increase in PG formation by intrauterine tissues.

Amnion↗
PubMed2000

Comparison of equine amnion and a nonadherent wound dressing material for bandaging pinch-grafted wounds in ponies.

OBJECTIVE: To evaluate healing of pinch-grafted wounds on the distal aspect of the limbs of ponies bandaged with equine amnion or a standard nonadherent wound dressing material. ANIMALS: 6 ponies. PROCEDURE: A 2.5x2.5-cm full-thickness section of skin was removed from the dorsal aspect of each limb at the midpoint of the metacarpus or metatarsus. Six days later, wounds were grafted with partial-thickness pinch grafts. Half the wounds were bandaged with amnion, and the other half were bandaged with a nonadherent dressing. Bandages were changed every 3 days until wound healing was complete. At each bandage change, numbers of grafts lost were recorded, and wounds were measured. RESULTS: Percentage of grafts lost from wounds bandaged with amnion was not significantly different from percentage lost from wounds bandaged with the nonadherent dressing. Median healing time for wounds bandaged with amnion (30 days) was significantly less than median healing time for wounds bandaged with the nonadherent dressing (39 days). All wounds were healed by day 45. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that amnion can be used for bandaging pinch-grafted wounds on the distal aspect of the limbs of ponies.

Amnion↗
PubMed1994

Reversal of hemiparkinsonian syndrome in nonhuman primates by amnion implantation into caudate nucleus.

Although recent animal and human experiments suggest that tissue implantation can ameliorate parkinsonism, there is controversy about what mechanism underlies recovery. Secretion of dopamine from the graft seems unlikely to be the sole restorative factor. Regenerative sprouting by the host brain may also underlie behavioral recovery. Fetal amnion and term amnion, which were shown to produce and secrete a factor that supports the outgrowth of neurite processes in vitro, were implanted in hemiparkinsonian monkeys. Fetal amnion implants induced sprouting of dopaminergic fibers from the host brain and behavioral improvement, despite failure of the grafts to survive. Animals implanted with term amnion also had some sprouted dopaminergic fibers and behavioral improvement, but these were limited and were similar to the recovery, in prior experiments using the same primate model of parkinsonism, of animals that received surgical cavitation only. Recovery after central nervous system grafting with fetal amnion, a fetal accessory tissue, does not require secretion of a deficient neurotransmitter(s) from the graft and occurs despite the failure of graft survival. Recovery after cerebral implantation of fetal tissues appears to depend more on the regenerative and recuperative processes of the host brain than on graft replacement of deficient neurotransmitters or development of functional synaptic connections between the graft and the host brain.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1999

Tyrosine kinase inhibitors block the glucocorticoid stimulation of prostaglandin endoperoxide H synthase expression in amnion cells.

Human amnion cells in primary culture respond to glucocorticoids in a characteristic fashion by the increased expression of the inducible prostaglandin endoperoxide H synthase isoenzyme, PGHS-2. Since PGHS-2 induction by agonists generally involves tyrosine kinases, we examined the possibility that the glucocorticoid stimulation of PGHS-2 in the amnion cells is tyrosine kinase dependent. PGHS-2 expression was stimulated in confluent, serum-starved amnion cells with dexamethasone, and the effect of the tyrosine kinase inhibitors herbimycin A and tyrphostins AG126, AG1288, and A1 on enzyme activity induction was determined. All four inhibitors blocked the increase of PGHS activity in a concentration-dependent manner with IC50 values of 0.077 +/- 0.05, 15.38 +/- 5.14, 20.91 +/- 3.1, and 29.77 +/- 8.21 microM, respectively (mean +/- SE, n = 4). Dexamethasone increased (approximately twofold) the tyrosine phosphorylation of 120-, 110-, and 77-kDa proteins in cell extracts, and herbimycin A selectively blocked the phosphorylation of the 110-kDa phosphoprotein. The stimulation of the steady-state level of PGHS-2 mRNA by dexamethasone was also inhibited by herbimycin A. These results suggest that glucocorticoids induce PGHS-2 expression in amnion cells with the involvement of tyrosine kinase(s). The role of tyrosine kinase dependent mechanisms in the control of amnion cell responsiveness to corticosteroids remains to be established.

Amnion↗
PubMedDate not supplied

Regulation of activin A, inhibin A, and follistatin production in human amnion and choriodecidual explants by inflammatory mediators.

OBJECTIVE: To determine the effects of inflammatory mediators on the production of activin A, inhibin A, and the binding protein follistatin in term amnion and choriodecidual tissues. METHODS: The effects of interleukin-1 beta (IL-1 beta; 1 ng/mL), tumor necrosis factor-alpha (TNF-alpha; 10 ng/mL), and bacterial lipopolysaccharide (LPS; 5 microg/mL) on production rates of activin A, inhibin A, and follistatin by term choriodecidual and amnion membranes in explant culture were determined using specific enzyme-linked immunoabsorbent assays. RESULTS: All explants (n = 6 placentas) produced detectable amounts of activin A, inhibin A, and follistatin under basal conditions; choriodecidual production rates were more than tenfold higher than amnion rates. In amnion explants, activin A production was stimulated by IL-1 beta and TNF-alpha to 450 +/- 155.4% and 531 +/- 170.8% of control, respectively (mean +/- standard error of the mean; P <.05 by analysis of variance), whereas production of inhibin and follistatin was stimulated to a much more modest extent. Similar responses were observed in the choriodecidual explants. Lipopolysaccharide had no significant effect on amnion activin A production, but stimulated choriodecidual production to 290 +/- 34% of control. Lipopolysaccharide exerted only limited effects on inhibin A and follistatin production. CONCLUSIONS: Treatment with proinflammatory mediators resulted in a preferential increase in activin A production compared with that of inhibin A or follistatin. These findings suggest that inflammation of the gestational membranes could result in increased local activin A production and bioactivity.

Activins↗
PubMedDate not supplied

[The motor activity of the chick embryo amnion in the late stages of development. The role of serotonin and noradrenaline].

Experiments with 13- to 19-day-old chicken embryos maintained at 37 degrees C were conducted using direct registration of embryonic movements and amnion pulsation. It is shown that in the non-innervated and lacking blood vessels non-striated-muscled amnion, motoric activity could be observed nearly up to the end of the embryonic development, not only during 5 to 14 days old interval as it was supposed earlier. In accordance with our previous results indicating important role of biogenic amines (serotonin and noradrenaline) in the regulation of motoric activity of the chicken embryo amnion at earlier and middle ages, this study provides some evidences of the humoral regulatory mechanism even at later embryonic stages. After being injected into amniotic fluid of older embryos, the serotonin stimulates and noradrenaline inhibits amnion motoric activity (the both are taken at final concentration of 10(-7) to 10(-6) M). Serotonin's receptors blocator, the cyprogeptadin, suppress while beta-adrenoreceptors' blocator, the propranolol, activates intact amnion motorics ( both are taken at final concentration of 10(-7) to 10(-5) M).

Amnion↗
PubMed2006

[Human amnion cells express the phenotypes of neural cells and adipocytes in vitro].

OBJECTIVE: To search for culture conditions in which the cells from human amnion could diferentiate into neural cells and hence to explore a new cell source for neural transplantaion. METHODS: Amnion cells from human were cultured with tissue piece method, passaged by trypsin digestion and identified with immunocytochemistry. RESULTS: Amnion cells migrated from explants and primary culture was established; they could multiply and expand steadily in a short time, and they could be passaged by trypsin digestion. When cultured in serum-free neural stem cell media, these cells could form the same spheroid shape as the neurospheres of neural stem cells. They could express alpha smooth muscle actin and differentiate into smooth muscle cells spontaneously, and could express nestin and vimentin, the markers for neural progenitors. Moreover, they could he stained by anti-beta III-tubulin, anti-neurofilament 200 and anti-NSE; the majorities could he stained by antityrosine hydroxylase, the marker for dopaminergic neurons. Lower than 0.1% of the total cells were stained by GFAP, indicating the existence of astrocytes. The amnion cells could also differentiate into adipocytes under specific induction. CONCLUSION: Amnion cells could differentiate into adipocytes and smooth muscle cells; they could express the protein for neural cells; thus may represent an alternative stem cell source for CNS cell transplantation.

Adipocytes↗
PubMedDate not supplied

[The motor activity of the chick embryo and amnion during embryogenesis].

Studies have been made on the motor activity of amnion and chick embryo from the 5th to the 14th day of development. Between the 5th and the 8th day of embryogenesis, when embryonic movements are rather poor, amnion contractions are mainly observed, their frequency being maximum to the 7th day. On further development (8-14 days), with the increase in the mass of the limbs which account for embryonic movements (body extremities), the increase in the intensity of their motor activity is paralleled by the decrease in the frequency of amnion contractions. Therefore, during the intensive growth and development of mainly frontal part of the embryo, the deficiency of motor activity of rather undeveloped body and extremities is presumably compensated by temporal motor activity of the amnion. Between the 8th and the 10th day, synchronous movements of embryo and amnion are observed. Possible mechanisms of synchronization are discussed.

Amnion↗
PubMed1989

Comparison of tumor cell invasion assays: human amnion versus reconstituted basement membrane barriers.

This study compares two well-known tumor cell invasion assays: the human amnion model versus the reconstituted basement membrane (RBM) system in the membrane invasion culture system (MICS). Our purpose was to present the quantification of tumor cell invasion using visual counts and radioactivity assessment in a side-by-side comparison and then to determine reasons for discrepancies in data collection and reporting. Basically, the data showed that: (1) fewer tumor cells invade the amnion membrane compared with the RBM, and substantially more variability exists among the data generated from the amnion assay (probably due to differences in membrane thickness); and (2) the invasive ability of the tumor cells appears to be greater using the radiolabel technique in both the amnion and RBM assay, a portion of which appears to be artifactual. Using the RBM, it was possible to sequentially select several subpopulations of highly invasive tumor cells, which was not possible with the human amnion. The invasive and metastatic potentials of these subpopulations were compared with those of established cell lines (selected in vivo). When analyzed independently, a direct relationship was shown between an increase in invasive ability and an increase in metastatic potential for the sublines selected in vitro and the established lines. However, collectively, it is more difficult to correlate the invasive and metastatic profiles of the sublines versus the established lines, which can probably be attributed to selection factors present during the establishment of the individual cell populations.

Amnion↗
PubMed1988

Inhibition by human recombinant tissue inhibitor of metalloproteinases of human amnion invasion and lung colonization by murine B16-F10 melanoma cells.

The human tissue inhibitor of metalloproteinases (TIMP) is a glycoprotein with a molecular weight of 28,000. It appears to be ubiquitous in human mesoderm tissues and has previously been shown to be identical to the collagenase inhibitor isolated from human skin fibroblasts. TIMP inhibits type I- and IV-specific collagenases and other neutral metalloendoproteinases that may be responsible for the degradation of extracellular matrix in tumor cell metastasis. In this work we have utilized recombinant human TIMP (rTIMP) obtained by expression of its cDNA gene (Carmichael et al., Proc. Natl. Acad. Sci. USA, 83:2407, 1986). The rTIMP is shown to have similar inhibition properties as natural TIMP against human skin fibroblast collagenase. In an in vitro amnion invasion assay system, rTIMP inhibited the invasion of B16-F10 murine melanoma cells through the human amniotic membrane at an identical concentration to that reported previously for natural TIMP. The mechanism by which rTIMP inhibits amniotic membrane invasion was compared to the mechanism by which the fibronectin receptor binding peptide RGDS and the aminin receptor binding peptide YIGSR inhibit amnion invasion. RGDS and YIGSR inhibited strong binding of the tumor cells to the amniotic membrane. In contrast rTIMP did not inhibit the cell adhesion step in amnion invasion, but actually increased the number of tumor cells that were tightly bound to the amnion. Thus rTIMP appears to inhibit a later step in the amnion invasion process, following B16-F10 cell adhesion. C57BL/6 mice treated with i.p. injections of rTIMP every 12 h for 6.5 days showed a significant inhibition of metastatic lung colonization by B16-F10 murine melanoma cells. While the rTIMP inhibited the number of metastatic lung tumors formed, it had no significant effect on the size of the lung tumors. Furthermore, tumors grown s.c. in mice receiving 12-h i.p. injections of rTIMP for 6.5 days, as in the in vivo colonization assay, showed no difference in size from controls. Thus the anticolonization effect of rTIMP appears not be due to an effect on tumor growth, but on the invasion step itself. The inhibition of lung colonization in C57BL/6 mice by rTIMP is one of the first examples showing an antimetastatic effect of a selective metalloproteinase inhibitor in a mammalian animal model, and supports an essential role for metalloproteinase(s) in the extravasation and invasion of tumor cells during lung colonization by blood-borne tumor cells.

Amnion↗
PubMed1982

Interactions of tumor cells with human amnion membrane: a model for studying tumor invasion in vitro.

The human amnion membrane consisting of a single layer of epithelium attached to the continuous basement membrane and the underlying collagenous stroma has been used to study tumor invasion in vitro by means of electron microscopy. Three cell lines utilized in these experiments were established from surgical specimens of human squamous cell carcinomas of the tongue and larynx. The cultivation of amnion membrane for 48h or longer leads to some alterations in the morphological appearance. All three carcinomas form aggregates which appear firmly attached to the amnion epithelium and are able to establish contacts to the basement membrane within 96h. In two cases the basement membrane reveals local defects and some cells have extended processes into the collagenous tissue. However, none of the tumor cells of the three carcinomas have broken through the basement membrane and grown into the collagenous stroma. Some differences of interaction between amnion epithelial cells and tumor cells of the three carcinomas are apparent. These ultrastructural findings show, that the amnion membrane model allows morphological analysis of various steps of tumor invasion under standardized conditions.

Amnion↗
PubMed1994

Extraembryonic membranes of the endoparasitic wasp Cotesia congregata: presence of a separate amnion and serosa.

Little information is available describing the development of endoparasitic Hymenoptera prior to hatching of the first instar larva. The present study reveals that in Cotesia congregata, and likely other braconid wasp parasites, the serosa and amnion comprise separate layers encasing the developing first instar larva. Examination of newly hatched first instar parasites in the hemocoel of Manduca sexta confirmed that the larvae were ensheathed in the remnants of an "amnion" at hatching, with patches of nucleated cells seen adhering in thin sheets to the larva. The amnion is delaminated from a cellular serosal membrane that lies directly beneath the chorion, which subsequently gives rise to teratocytes. Scanning electron micrographs indicate that remnants of the amnion remained associated with the larvae for a longer period posthatch than did the teratocytes, which rapidly dispersed into the host hemolymph. The presence of an amnion-like layer in braconid endoparasitic wasps may prove to be significant with respect to our understanding of host-parasite immunological interactions occurring during the initiation of the relationship of the parasites with their host.

Amnion↗