Desarrollo embriológico e importancia clínica de la membrana amniótica: revisión narrativa de literatura / Embryological development and clinical significance of the amniotic membrane: narrative literature review

La membrana amniótica (MA), ubicada en el lado interno de la placenta fetal, ha sido objeto de múltiples investigaciones para intentar dilucidar su papel embriológico y su potencial celular terapéutico. Actualmente las limitaciones del estudio en fetos humanos hacen que parte de su funcionamiento sea una incógnita, sin embargo algunos estudios clínicos y básicos nos dan luz sobre su papel en la médica moderna. Se realizó una revisión bibliográfica de la literatura desde 1960 hasta 2022, empleando bases de datos como PubMed, SciELO y Scopus, siendo incluidos un total de 50 artículos y dos textos de embriología. El objetivo de esta revisión narrativa fue sintetizar la información sobre la angiogénesis y su importancia clínica. La información recopilada permitió evidenciar que las propiedades de curación de la piel del feto se deben a factores intrínsecos del feto, y a que las células epiteliales amnióticas humanas poseen una diferenciación similar a las células madre embrionarias, con la capacidad de diferenciación similar al de las células mesenquimales, resaltando su importancia clínica por sus características regenerativas. En conclusión, el desarrollo embrionario humano sigue siendo relativamente inexplicable, pero su conocimiento ha permitido grandes avances, que podrían ser útiles en terapias de regeneración, reparación de tejidos y órganos lesionados.

The amniotic membrane, located on the inner side of the fetal placenta, has been the subject of multiple investigations to try to elucidate its embryological role and its therapeutic cellular potential. Currently, the limitations of the study in human fetuses mean that part of its functioning is unknown, however, some clinical and basic studies shed light on its role in modern medicine. A bibliographic review of the literature was carried out from 1960 to 2022, using databases such as PubMed, SciELO and Scopus, including a total of 50 articles and two embryology texts. The objective of this narrative review was to synthesize information on angiogenesis and its clinical importance. The information collected made it possible to show that the healing properties of the fetal skin are due to intrinsic factors of the fetus, and that human amniotic epithelial cells have a differentiation similar to embryonic stem cells, with the differentiation capacity similar to that of mesenchymal cells, highlighting their clinical importance due to their regenerative characteristics. In conclusion, human embryonic development remains relatively inexplicable, but its knowledge has allowed great advances, which could be useful in regeneration therapies, repair of injured tissues and organs.

The associations of gestational weight gain and midpregnancy lipid levels with placental size and placental-to-birth weight ratio: findings from a chinese birth cohort study.

BACKGROUND: The placenta serves as the sole maternal organ responsible for transmitting nutrients to the fetus, playing a crucial role in supporting standard fetal growth and development. To date, only a small number of studies have investigated the impact of maternal gestational weight gain and lipid concentrations on placental development. This study aimed to explore the influence of weight gain during pregnancy and lipid levels in the second trimester on placental weight, volume, and the placental weight ratio. METHODS: This birth cohort study encompassed 1,358 mother-child pairs. Placental data for each participant was gathered immediately post-delivery, and the study incorporated data on gestational weight gain throughout pregnancy and lipid profiles from the mid-trimester. A linear regression model was employed to assess the correlations between gestational weight gain, mid-trimester lipid levels, and metrics such as placental weight, placental volume, and the placental-to-birth weight ratio (PFR). RESULTS: In the study groups of pre-pregnancy underweight, normal weight, and overweight, the placental weight increased by 4.93 g (95% CI: 1.04-8.81), 2.52 g (95% CI: 1.04-3.99), and 3.30 g (95% CI: 0.38-6.22) per 1 kg of gestational weight gain, respectively. Within the pre-pregnancy underweight and normal weight groups, the placental volume increased by 6.79 cm^3 (95% CI: 3.43-10.15) and 2.85 cm^3 (95% CI: 1.31-4.39) per 1 kg of gestational weight gain, respectively. Additionally, placental weight exhibited a positive correlation with triglyceride (TG) levels (ß = 9.81, 95% CI: 3.28-16.34) and a negative correlation with high-density lipoprotein (HDL-C) levels (ß = - 46.30, 95% CI: - 69.49 to - 23.11). Placental volume also showed a positive association with TG levels (ß = 14.54, 95% CI: 7.69-21.39). Conversely, PFR demonstrated a negative correlation with increasing HDL-C levels (ß = - 0.89, 95% CI: - 1.50 to - 0.27). CONCLUSIONS: Gestational weight gain was significantly correlated with both placental weight and volume. This association was especially pronounced in women who, prior to pregnancy, were underweight or of normal weight. Additionally, TG and HDL-C levels during the mid-trimester were linked to placental development.

Participação dos neutrófilos durante a implantação embrionária no desenvolvimento da placenta em camundongos / Participation of neutrophils during embryonic implantation in the placental development in mice

A implantação do embrião na parede uterina é um processo complexo que consiste na interação do blastocisto com as células epiteliais do útero, e depende de diferentes tipos celulares do microambiente uterino. Embora a literatura mostre a participação de neutrófilos neste processo, os dados ainda são incipientes para proposição da função exata destas células nos períodos iniciais da gestação. Dados do nosso grupo de pesquisa mostraram que neutrófilos pró-angiogênicos induzem a tolerância gestacional, e que a depleção de neutrófilos durante as fases iniciais da gestação prejudica a implantação do blastocisto e a progressão da gestação. Com base nestes resultados, o presente estudo visou investigar se a depleção de neutrófilos na fase pré-receptiva da janela de implantação do blastocisto altera a morfologia placentária. Para tanto, foi utilizado o modelo de gestação alogênica, onde camundongos fêmeas C57BL/6, após cruzamento com machos Balb/C foram tratadas com anticorpo anti-Ly6G ou isotipo no dia 1,5 da gestação (24 horas após a detecção do plug vaginal) em dose suficiente para manter a depleção de neutrófilos circulantes por 48 horas (200µg/ 500µL; i.p). No final da gestação (dia 18,5), o sangue periférico foi coletado e, em seguida, os animais foram submetidos a laparotomia para retirada da placenta, a qual foi submetida à análise histológica. As análises dos leucócitos circulantes evidenciaram a efetividade do tratamento para depleção de neutrófilos periféricos. A análise histológica mostrou alterações significativas na morfologia da placenta nos animais tratados com anti-Ly6G. Foram detectadas a redução da zona juncional, de células trofoblásticas e de fatores angiogênicos, como fator de crescimento do endotélio vascular (VEGF), e das moléculas de adesão intracelular-1 (ICAM-1) e de plaqueta e endotélio (PECAM-1). Esses dados evidenciam a importância dos neutrófilos nos primeiros dias de gestação para o desenvolvimento da placenta

Blastocyst implantation is a complex process, consisting of the interaction between blastocyst and uterine epithelial cells. Also, it is well known that the implantation site resembles an inflammatory response, with a profusion of recruited immune cells into the endometrial stroma and lumen from the blood. The role of macrophages, natural killers, and dendritic cells have been extensively studied, however, the participation of neutrophils in this process remains unclear. Data from our research group showed that pro-angiogenic neutrophils induced gestation tolerance, also peripheral neutrophils depletion at the time of active placental development led to smaller embryo sizes and abnormal placentation in mice. In this context, the present study aimed to investigate whether pharmacological depletion of neutrophils in mice in the blastocyst implantation phase alters placental morphology. Therefore, C7/BL/6 female mice, after mating with Balb/C males, were treated with an anti-Ly6G antibody or isotype on day 1 of gestation (after detection of the vaginal plug) at a dose sufficient to maintain the depletion of circulating neutrophils for 48 hours (200 µg/500µL; i.p). At the end of the gestational day (day 18), peripheral blood was collected, and then the animals were submitted to laparotomy for the placenta removal and subsequent histological analysis. The analysis of circulating leukocytes from neutrophils depleted mice showed a reduction of peripheral neutrophils up to 48 hours after antibody injection. The histological analysis showed significant alterations in the placenta morphology of the animals treated with anti-Ly6G. The morphometric analyses showed a reduction in the size of neutrophils depleted placenta due to diminished junctional zone and reduction of trophoblast cells. Also, it was observed a reduction of vascular endothelial growth factors (VEGF), reduction of adhesion molecules intracell-1 (ICAM-1), and platelets and endothelium (PECAM-1) positive cells in the junctional zone. In conclusion, these data show the importance of neutrophils on the first days of pregnancy for the development of the placenta

PEG10 viral aspartic protease domain is essential for the maintenance of fetal capillary structure in the mouse placenta.

The therian-specific gene paternally expressed 10 (Peg10) plays an essential role in placenta formation: Peg10 knockout mice exhibit early embryonic lethality as a result of severe placental defects. The PEG10 protein exhibits homology with long terminal repeat (LTR) retrotransposon GAG and POL proteins; therefore, we generated mice harboring a mutation in the highly conserved viral aspartic protease motif in the POL-like region of PEG10 because this motif is essential for the life cycle of LTR retrotransposons/retroviruses. Intriguingly, frequent perinatal lethality, not early embryonic lethality, was observed with fetal and placental growth retardation starting mid-gestation. In the mutant placentas, severe defects were observed in the fetal vasculature, where PEG10 is expressed in the three trophoblast cell layers that surround fetal capillary endothelial cells. Thus, Peg10 has essential roles, not only in early placenta formation, but also in placental vasculature maintenance from mid- to late-gestation. This implies that along the feto-maternal placenta interface an interaction occurs between two retrovirus-derived genes, Peg10 and retrotransposon Gag like 1 (Rtl1, also called Peg11), that is essential for the maintenance of fetal capillary endothelial cells.

The imbalance of TNF and IL-6 levels and FOXP3 expression at the maternal-fetal interface is involved in adverse pregnancy outcomes in a susceptible murine model of congenital toxoplasmosis.

Vertical transmission of Toxoplasma gondii leads to adverse pregnancy outcomes depending on the time at which the infection occurs and the immunological state of the mother. C57BL/6 and BALB/c mice have been described as susceptible and resistant mouse lineages to congenital T. gondii infection, respectively. This study aimed to elucidate the systemic and local cytokine profile of pregnant mice infected with T. gondii and whether the expression of the transcription factor FOXP3, related to T regulatory cells, is associated with the resistance/susceptibility of these lineages of mice in the context of experimental congenital toxoplasmosis. For this purpose, C57BL/6 and BALB/c females were orally infected with the T. gondii ME-49 strain on the day of vaginal plug detection or day 14 of gestation, examined 7 or 5 days later, respectively, as models of early and late pregnancy. Cytokine levels were measured systemically and in the uterus/placenta. Additionally, the uterus/placenta were evaluated macroscopically for resorption rates and histologically for parasite and FOXP3 immunostaining. The FOXP3 protein expression was also evaluated by western blotting assay. It was found that, during early pregnancy, the infection leads to high IFN-γ, TNF and IL-6 levels systemically, with the TNF levels being higher in C57BL/6 mice. At the maternal-fetal interface, the infection induced high levels of IFN-γ in both mouse lineages; however, higher levels were observed in BALB/c, while high TNF and IL-6 levels were found in C57BL/6, but not in BALB/c mice. In contrast, in late gestation, T. gondii interfered less strongly with the cytokine profile. In early pregnancy, a reduction of FOXP3 expression at the maternal-fetal interface of infected mice was also observed, and the reduction was larger in C57BL/6 compared with BALB/c mice. Additionally, the parasite was seldom found in the uterus/placenta. Thus, the worse pregnancy outcomes observed in C57BL/6 mice were associated with higher TNF systemically, and TNF and IL-6 at the maternal-fetal interface, with lower FOXP3 expression.

X chromosome-dependent disruption of placental regulatory networks in hybrid dwarf hamsters.

Embryonic development in mammals is highly sensitive to changes in gene expression within the placenta. The placenta is also highly enriched for genes showing parent-of-origin or imprinted expression, which is predicted to evolve rapidly in response to parental conflict. However, little is known about the evolution of placental gene expression, or if divergence of placental gene expression plays an important role in mammalian speciation. We used crosses between two species of dwarf hamsters (Phodopus sungorus and Phodopus campbelli) to examine the genetic and regulatory underpinnings of severe placental overgrowth in their hybrids. Using quantitative genetic mapping and mitochondrial substitution lines, we show that overgrowth of hybrid placentas was primarily caused by genetic differences on the maternally inherited P. sungorus X chromosome. Mitochondrial interactions did not contribute to abnormal hybrid placental development, and there was only weak correspondence between placental disruption and embryonic growth. Genome-wide analyses of placental transcriptomes from the parental species and first- and second-generation hybrids revealed a central group of co-expressed X-linked and autosomal genes that were highly enriched for maternally biased expression. Expression of this gene network was strongly correlated with placental size and showed widespread misexpression dependent on epistatic interactions with X-linked hybrid incompatibilities. Collectively, our results indicate that the X chromosome is likely to play a prominent role in the evolution of placental gene expression and the accumulation of hybrid developmental barriers between mammalian species.

Intraplacental Fetal Vessel Diameter May Help Predict for Placental Invasiveness in Pregnant Women at High Risk for Placenta Accreta Spectrum Disorders.

Background Prenatal identification of placenta accreta spectrum (PAS) disorder is essential for treatment planning. More objective means for predicting PAS and clinical outcome may be provided by MRI descriptors. Purpose To investigate the association of intraplacental fetal vessel (IFV) diameter at MRI with PAS and peripartum complications. Materials and Methods Between March 2016 and October 2019, 160 gravid women suspected of having PAS underwent placental MRI as part of a prospective trial. Secondary analysis was performed by two experienced genitourinary radiologists for presence and maximum diameter of IFVs. Relative risk ratios were computed to test the association of IFVs with presence and depth of PAS invasiveness. Receiver operating characteristic analysis was used to evaluate the ability of IFV diameter to help predict PAS, placenta percreta, and peripartum complications and for comparison of the area under the curve (AUC) versus that from other combined MRI predictors of PAS (eg, myometrial thinning, intraplacental T2-hypointense bands, uterine bulge, serosal hypervascularity, and signs of extrauterine placental spread). Intraoperative and histopathologic findings were the reference standard. Results A total of 155 women were evaluated (mean age, 35 years ± 5 [standard deviation]; mean gestational age, 32 weeks ± 3). PAS was diagnosed in 126 of 155 women (81%) (placental percreta in 68 of 126 [54%]). At delivery, 30 of 126 women (24%) experienced massive blood loss (>2000 mL). IFVs were detected at MRI in 109 of 126 women with PAS (86%) and in 67 of 68 women with placental percreta (98%). The relative risk ratio was 2.4 (95% CI: 1.6, 3.4; P < .001) for PAS and 10 (95% CI: 1.5, 70.4; P < .001) for placental percreta when IFVs were visible. IFVs of 2 mm or greater were associated with PAS (AUC, 0.81; 95% CI: 0.67, 0.95; P = .04). IVFs of 3 mm or greater were associated with placenta percreta (AUC, 0.81; 95% CI: 0.73, 0.89; P < .001) and with peripartum complications, including massive bleeding (AUC, 0.80; 95% CI: 0.71, 0.89; P < .001). Combining assessment of IFVs with other MRI descriptors improved the ability of MRI to predict PAS (AUC, 0.94 vs 0.89; P = .009). Conclusion Assessment of intraplacental fetal vessels with other MRI descriptors improved the ability of MRI to help predict PAS. Vessel diameter of 3 mm or greater was predictive of placenta percreta and peripartum complications. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Dighe in this issue.

Profiling of Tryptophan Metabolic Pathways in the Rat Fetoplacental Unit During Gestation.

Placental homeostasis of tryptophan is essential for fetal development and programming. The two main metabolic pathways (serotonin and kynurenine) produce bioactive metabolites with immunosuppressive, neurotoxic, or neuroprotective properties and their concentrations in the fetoplacental unit must be tightly regulated throughout gestation. Here, we investigated the expression/function of key enzymes/transporters involved in tryptophan pathways during mid-to-late gestation in rat placenta and fetal organs. Quantitative PCR and heatmap analysis revealed the differential expression of several genes involved in serotonin and kynurenine pathways. To identify the flux of substrates through these pathways, Droplet Digital PCR, western blot, and functional analyses were carried out for the rate-limiting enzymes and transporters. Our findings show that placental tryptophan metabolism to serotonin is crucial in mid-gestation, with a subsequent switch to fetal serotonin synthesis. Concurrently, at term, the close interplay between transporters and metabolizing enzymes of both placenta and fetal organs orchestrates serotonin homeostasis and prevents hyper/hypo-serotonemia. On the other hand, the placental production of kynurenine increases during pregnancy, with a low contribution of fetal organs throughout gestation. Any external insult to this tightly regulated harmony of transporters and enzymes within the fetoplacental unit may affect optimal in utero conditions and have a negative impact on fetal programming.

The effect of laser-assisted hatching on the methylation and expression pattern of imprinted gene IGF2/H19 in mouse blastocysts and offspring.

PURPOSE: This study aimed to determine the effects of drilling and thinning treatment of laser-assisted hatching on the expression and methylation of imprinted gene IGF2/H19 in embryos and offspring. METHODS: The prehatching blastocysts with treatment of drilling or thinning, or control prehatching blastocysts, were transplanted in surrogate uteri. The DNA methylation of IGF2/H19 imprinting control region (ICR) and the expression of IGF2 and H19 were respectively evaluated using bisulfite conversion-mediated sequencing and real-time PCR. RESULTS: The drilling group showed a significant increase in the development rate of hatched blastocysts in comparison with the control and thinning group. DNA methylation level of IGF2/H19 ICR of hatched blastocysts in the thinning group was 27.33% in comparison with the 38.67% and 36% observed in the control and drilling group. The thinning treatment increased the DNA methylation level of IGF2/H19 ICR in the placenta in comparison with the control and drilling group. The drilling and thinning treatment decreased the expression level of H19 mRNA in prehatching and hatched blastocysts as well as placenta, while a significant increase in the expression level of H19 mRNA of offspring was observed in the thinning group. The thinning treatment increased the expression level of IGF2 mRNA of prehatching blastocysts and offspring and a significant decrease in placenta, while the drilling treatment resulted in a significant increase in the expression level of IGF2 mRNA of hatched blastocysts and placenta. CONCLUSION: These observations suggested that drilling used for hatching of in vitro cultured mouse blastocysts may improve the production of offspring.