Placental Drug Delivery to Treat Pre-Eclampsia and Fetal Growth Restriction

Pre-eclampsia and fetal growth restriction (FGR) continue to cause unacceptably high levels of morbidity and mortality, despite significant pharmaceutical and technological advances in other disease areas. The recent pandemic has also impacted obstetric care, as COVID-19 infection increases the risk of poor pregnancy outcomes. This review explores the reasons why it lacks effective drug treatments for the placental dysfunction that underlies many common obstetric conditions and describes how nanomedicines and targeted drug delivery approaches may provide the solution to the current drug drought. The ever-increasing range of biocompatible nanoparticle formulations available is now making it possible to selectively deliver drugs to uterine and placental tissues and dramatically limit fetal drug transfer. Formulations that are refractory to placental uptake offer the possibility of retaining drugs within the maternal circulation, allowing pregnant individuals to take medicines previously considered too harmful to the developing baby. Liposomes, ionizable lipid nanoparticles, polymeric nanoparticles, and adenoviral vectors have all been used to create efficacious drug delivery systems for use in pregnancy, although each approach offers distinct advantages and limitations. It is imperative that recent advances continue to be built upon and that there is an overdue investment of intellectual and financial capital in this field.

Translational use of homing peptides: Tumor and placental targeting

HYPOTHESIS

Tissue-specific homing peptides have been shown to improve chemotherapeutic efficacy due to their trophism for tumor cells. Other sequences that selectively home to the placenta are providing new and safer therapeutics to treat complications in pregnancy. Our hypothesis is that the placental homing peptide RSGVAKS (RSG) may have binding affinity to cancer cells, and that insight can be gained into the binding mechanisms of RSG and the tumor homing peptide CGKRK to model membranes that mimic the primary lipid compositions of the respective cells.

EXPERIMENTS

Following cell culture studies on the binding efficacy of the peptides on a breast cancer cell line, a systematic translational characterization is delivered using ellipsometry, Brewster angle microscopy and neutron reflectometry of the extents, structures, and dynamics of the interactions of the peptides with the model membranes on a Langmuir trough.

FINDINGS

We start by revealing that RSG does indeed have binding affinity to breast cancer cells. The peptide is then shown to exhibit stronger interactions and greater penetration than CGKRK into both model membranes, combined with greater disruption to the lipid component. RSG also forms aggregates bound to the model membranes, yet both peptides bind to a greater extent to the placental than cancer model membranes. The results demonstrate the potential for varying local reservoirs of peptide within cell membranes that may influence receptor binding. The innovative nature of our findings motivates the urgent need for more studies involving multifaceted experimental platforms to explore the use of specific peptide sequences to home to different cellular targets.

Liposome-Encapsulated Anti-inflammatory Proteins for Targeted Delivery to the Placenta to Treat Fetal Growth Restriction

Fetal growth restriction (FGR), the failure of a fetus to reach its genetically determined growth potential, is a serious complication affecting up to 10% of pregnancies. FGR is a major risk factor for stillbirth and, in the survivors, neurodevelopmental disorders. We have recently identified that the anti-inflammatory and pro-resolving molecule, lipoxin A4 (LXA4) and its soluble receptor, formyl-peptide receptor-2 (FPR-2) are significantly decreased in human placentas from FGR pregnancy. The LXA4 synthetic analog Compound 43 (C43) is considered a safe, anti-inflammatory therapy and is being developed as a treatment for disease conditions with an inflammatory basis, for example, asthma in children. Identification of therapies to treat FGR in utero comes with the need to mitigate their potential side effects and the use of nanoparticle-mediated delivery systems could facilitate this. Our current studies are focused on targeting the resolution of inflammation observed in FGR placentas, by synthesizing liposome-encapsulated C43 as a novel therapeutic to improve placental function in FGR. In this chapter, we provide a detailed methodological procedure for the preparation of liposomes and conjugation of the peptide sequences, which selectively bind to the outer placental syncytiotrophoblast layer or the vascular endothelium of the uterine spiral arterioles.

Acute respiratory distress syndrome: potential of therapeutic interventions effective in treating progression from COVID-19 to treat progression from other illnesses-a systematic review

BACKGROUND

Acute respiratory distress syndrome (ARDS) is the most severe form of lung injury, rendering gaseous exchange insufficient, leading to respiratory failure. Despite over 50 years of research on the treatment of ARDS when developed from illnesses such as sepsis and pneumonia, mortality remains high, and no robust pharmacological treatments exist. The progression of SARS-CoV-2 infections to ARDS during the recent global pandemic led to a surge in the number of clinical trials on the condition. Understandably, this explosion in new research focused on COVID-19 ARDS (CARDS) rather than ARDS when developed from other illnesses, yet differences in pathology between the two conditions mean that optimal treatment for them may be distinct.

AIM

The aim of the present work is to assess whether new therapeutic interventions that have been developed for the treatment of CARDS may also hold strong potential in the treatment of ARDS when developed from other illnesses. The study objectives are achieved through a systematic review of clinical trials.

RESULTS

The COVID-19 pandemic led to the identification of various therapeutic interventions for CARDS, some but not all of which are optimal for the management of ARDS. Interventions more suited to CARDS pathology include antithrombotics and biologic agents, such as cytokine inhibitors. Cell-based therapies, on the other hand, show promise in the treatment of both conditions, attributed to their broad mechanisms of action and the overlap in the clinical manifestations of the conditions. A shift towards personalised treatments for both CARDS and ARDS, as reflected through the increasing use of biologics, is also evident.

CONCLUSIONS

As ongoing CARDS clinical trials progress, their findings are likely to have important implications that alter the management of ARDS in patients that develop the condition from illnesses other than COVID-19 in the future.

Internal Mammary Arteries as a Model to Demonstrate Restoration of the Impaired Vasodilation in Hypertension, Using Liposomal Delivery of the CYP1B1 Inhibitor, 2,3',4,5'-Tetramethoxystilbene

A significant number of patients with severe cardiovascular disease, undergoing coronary artery bypass grafting (CABG), present with hypertension. While internal mammary arteries (IMAs) may be a better alternative to vein grafts, their impaired vasodilator function affects their patency. Our objectives were to (1) determine if inhibition of the cytochrome P450 enzyme CYP1B1, using liposome-encapsulated 2,3′,4,5′-tetramethoxystilbene (TMS), can potentiate vasodilation of IMAs from CABG patients, and (2) assess mechanisms involved using coronary arteries from normal rats, in an ex vivo model of hypertension. PEGylated liposomes were synthesized and loaded with TMS (mean diameter 141 ± 0.9 nm). Liposomal delivery of TMS improved its bioavailability Compared to TMS solution (0.129 ± 0.02 ng/mL vs. 0.086 ± 0.01 ng/mL at 4 h; p < 0.05). TMS-loaded liposomes alleviated attenuated endothelial-dependent acetylcholine (ACh)-induced dilation in diseased IMAs (@ACh 10−4 M: 56.9 ± 5.1%; n = 8 vs. 12.7 ± 7.8%; n = 6; p < 0.01) for TMS-loaded liposomes vs. blank liposomes, respectively. The alleviation in dilation may be due to the potent inhibition of CYP1B1 by TMS, and subsequent reduction in reactive oxygen species (ROS) moieties and stimulation of nitric oxide synthesis. In isolated rat coronary arteries exposed to a hypertensive environment, TMS-loaded liposomes potentiated nitric oxide and endothelium-derived hyperpolarization pathways via AMPK. Our findings are promising for the future development of TMS-loaded liposomes as a promising therapeutic strategy to enhance TMS bioavailability and potentiate vasodilator function in hypertension, with relevance for early and long-term treatment of CABG patients, via the sustained and localized TMS release within IMAs.

Placental expression of Estrogen related receptor gamma (ESRRG) is reduced in FGR pregnancies and is mediated by hypoxia

Fetal growth restriction (FGR) describes a fetus which has not achieved its genetic growth potential; it is closely linked to placental dysfunction and uteroplacental hypoxia. Estrogen-related receptor gamma (ESRRG) is regulated by hypoxia and is highly expressed in the placenta. We hypothesized ESRRG is a regulator of hypoxia-mediated placental dysfunction in FGR pregnancies. Placentas were collected from women delivering appropriate for gestational age (AGA; n = 14) or FGR (n = 14) infants. Placental explants (n = 15) from uncomplicated pregnancies were cultured for up to 4 days in 21% or 1% O₂, or with 200 μM cobalt chloride (CoCl₂), or treated with the ESRRG agonists DY131 under different oxygen concentrations. RT-PCR, Western blotting, and immunochemistry were used to assess mRNA and protein levels of ESRRG and its localization in placental tissue from FGR or AGA pregnancies, and in cultured placental explants. ESRRG mRNA and protein expression were significantly reduced in FGR placentas, as was mRNA expression of the downstream targets of ESRRG, hydroxysteroid 11-beta dehydrogenase 2 (HSD11B2), and cytochrome P-450 (CYP19A1.1). Hypoxia-inducible factor 1-alpha protein localized to the nuclei of the cytotrophoblasts and stromal cells in the explants exposed to CoCl₂ or 1% O₂. Both hypoxia and CoCl₂ treatment decreased ESRRG and its downstream genes’ mRNA expression, but not ESRRG protein expression. DY131 increased the expression of ESRRG signaling pathways and prevented abnormal cell turnover induced by hypoxia. These data show that placental ESRRG is hypoxia-sensitive and altered ESRRG-mediated signaling may contribute to hypoxia-induced placental dysfunction in FGR. Furthermore, DY131 could be used as a novel therapeutic approach for the treatment of placental dysfunction.

Sex-specific effects of Bisphenol a on the signalling pathway of ESRRG in the human placenta

Bisphenol A (BPA) exposure during pregnancy is associated with low fetal weight, particularly in male fetuses. The expression of estrogen-related receptor gamma (ESRRG), a receptor for BPA in the human placenta, is reduced in fetal growth restriction. This study sought to explore whether ESRRG signaling mediates BPA-induced placental dysfunction and determine whether changes in the ESRRG signaling pathway are sex-specific. Placental villous explants from 18 normal term pregnancies were cultured with a range of BPA concentrations (1 nM–1 μM). Baseline BPA concentrations in the placental tissue used for explant culture ranged from 0.04 to 5.1 nM (average 2.3 ±1.9 nM; n = 6). Expression of ESRRG signaling pathway constituents and cell turnover were quantified. BPA (1 μM) increased ESRRG mRNA expression after 24 h in both sexes. ESRRG mRNA and protein expression was increased in female placentas treated with 1 μM BPA for 24 h but was decreased in male placentas treated with 1 nM or 1 μM for 48 h. Levels of 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1) and placenta specific-1 (PLAC1), genes downstream of ESRRG, were also affected. HSD17B1 mRNA expression was increased in female placentas by 1 μM BPA; however, 1 nM BPA reduced HSD17B1 and PLAC1 expression in male placentas at 48 h. BPA treatment did not affect rates of proliferation, apoptosis, or syncytiotrophoblast differentiation in cultured villous explants. This study has demonstrated that BPA affects the ESRRG signaling pathway in a sex-specific manner in human placentas and a possible biological mechanism to explain the differential effects of BPA exposure on male and female fetuses observed in epidemiological studies.

Conjugation to PEG as a Strategy to Limit the Uptake of Drugs by the Placenta: Potential Applications for Drug Administration in Pregnancy

Here, we evaluated the feasibility of non-prodrug PEG-drug conjugates to decrease the accumulation of drugs within the placental tissues. The results showed that PEG was biocompatible with the human placenta with no alteration of the basal rate of proliferation or apoptosis in term placental explants. No significant changes in the released levels of lactate dehydrogenase and the human chorionic gonadotropin were observed after PEG treatment. The cellular uptake studies revealed that conjugating Cy5.5 and haloperidol to PEG significantly reduced (by up to ∼40-fold) their uptake by the placenta. These findings highlight the viability of novel non-prodrug polymer-drug conjugates to avoid the accumulation of drugs within the placenta.

The lexicon of antimicrobial peptides: a complete set of arginine and tryptophan sequences

Our understanding of the activity of cationic antimicrobial peptides (AMPs) has focused on well-characterized natural sequences, or limited sets of synthetic peptides designed de novo. We have undertaken a comprehensive investigation of the underlying primary structural features that give rise to the development of activity in AMPs. We consider a complete set of all possible peptides, up to 7 residues long, composed of positively charged arginine (R) and / or hydrophobic tryptophan (W), two features most commonly associated with activity. We found the shortest active peptides were 4 or 5 residues in length, and the overall landscapes of activity against gram-positive and gram-negative bacteria and a yeast were positively correlated. For all three organisms we found a single activity peak corresponding to sequences with around 40% R; the presence of adjacent W duplets and triplets also conferred greater activity. The mechanistic basis of these activities comprises a combination of lipid binding, particularly to negatively charged membranes, and additionally peptide aggregation, a mode of action previously uninvestigated for such peptides. The maximum specific antimicrobial activity appeared to occur in peptides of around 10 residues, suggesting ‘diminishing returns’ for developing larger peptides, when activity is considered per residue of peptide.

Clark et al. comprehensively explore the primary structural features underlying the activity of a complete set of antimicrobial peptides (AMPs). They find that the shortest active peptides were 4 or 5 residues in length, with activity being associated with 40% arginine, and multiple adjacent tryptophan residues. This study provides insights into the design of effective AMPs.

Microfluidic-assisted fabrication of phosphatidylcholine-based liposomes for controlled drug delivery of chemotherapeutics

Microfluidic enables precise control over the continuous mixing of fluid phases at the micrometre scale, aiming to optimize the processing parameters and to facilitate scale-up feasibility. The optimization of parameters to obtain monodispersed drug-loaded liposomes however is challenging. In this work, two phosphatidylcholines (PC) differing in acyl chain length were selected, and used to control the release of the chemotherapeutic agent doxorubicin hydrochloride, an effective drug used to treat breast cancer. Microfluidics was used to rapidly screen manufacturing parameters and PC formulations to obtain monodispersed unilamellar liposomal formulations with a reproducible size (i.e. < 200 nm). Cholesterol was included in all liposomal formulations; some formulations also contained DMPC(1,2-dimyristoyl-sn-glycero-3-phosphocholine) and/or DSPC(1,2-distearoyl-sn-glycero-3-phosphocholine). Systematic variations in microfluidics total flow rate (TFR) settings were performed, while keeping a constant flow rate ratio (FRR). A total of six PC-based liposomes were fabricated using the optimal manufacturing parameters (TFR 500 μL/min, FRR 0.1) for the production of reproducible, stable liposome formulations with a narrow size distribution. Liposomes actively encapsulating doxorubicin exhibited high encapsulation efficiencies (>80%) for most of the six formulations, and sustained drug release profiles in vitro over 48 h. Drug release profiles varied as a function of the DMPC/DSPC mol content in the lipid bilayer, with DMPC-based liposomes exhibiting a sustained release of doxorubicin when compared to DSPC liposomes. The PC-based liposomes, with a slower release of doxorubicin, were tested in vitro, as to investigate their cytotoxic activity against three human breast cancer cell lines: the non-metastatic ER+/PR + MCF7 cells, the triple-negative aggressive MDA-MB 231 cells, and the metastatic HER2-overexpressing/PR + BT474 cells. Similar cytotoxicity levels to that of free doxorubicin were reported for DMPC₅ and DMPC₃ binary liposomes (IC₅₀ ~ 1 μM), whereas liposomes composed of a single PC were less cytotoxic (IC₅₀ ~ 3-4 μM). These results highlight that microfluidics is suitable for the manufacture of monodispersed and size-specific PC-based liposomes in a controlled single-step; furthermore, selected PC-based liposome represent promising nanomedicines for the prolonged release of chemotherapeutics, with the aim of improving outcomes for patients.

The potential role of the E SRRG pathway in placental dysfunction

Normal placental development and function is of key importance to fetal growth. Conversely aberrations of placental structure and function are evident in pregnancy complications including fetal growth restriction (FGR) and preeclampsia. Although trophoblast turnover and function is altered in these conditions, their underlying aetiologies and pathophysiology remains unclear, which hampers development of therapeutic interventions. Here we review evidence that supports a role for estrogen related receptor-gamma (ESRRG) in the development of placental dysfunction in FGR and preeclampsia. This relationship deserves particular consideration because ESRRG is highly expressed in normal placenta, is reduced in FGR and preeclampsia and its expression is altered by hypoxia, which is thought to result from deficient placentation seen in FGR and preeclampsia. Several studies have also found microRNA (miRNA) or other potential upstream regulators of ESRRG negatively influence trophoblast function which could contribute to placental dysfunction seen in FGR and preeclampsia. Interestingly, miRNAs regulate ESRRG expression in human trophoblast. Thus, if ESRRG is pivotally associated with the abnormal trophoblast turnover and function it may be targeted by microRNAs or other possible upstream regulators in the placenta. This review explores altered expression of ESRRG and upstream regulation of ESRRG-mediated pathways resulting in the trophoblast turnover, placental vascularisation, and placental metabolism underlying placental dysfunctions. This demonstrates that the ESRRG pathway merits further investigation as a potential therapeutic target in FGR and preeclampsia.

Functional Evaluation of STOX1 (STORKHEAD-BOX PROTEIN 1) in Placentation, Preeclampsia, and Preterm Birth

Revaluation of the association of the STOX1 (STORKHEAD_BOX1 PROTEIN 1) transcription factor mutation (Y153H, C allele) with the early utero-vascular origins of placental pathology is warranted. To investigate if placental STOX1 Y153H genotype affects utero-vascular remodeling-compromised in both preterm birth and preeclampsia-we utilized extravillous trophoblast (EVT) explant and placental decidual coculture models, transfection of STOX1 wild-type and mutant plasmids into EVT-like trophoblast cell lines, and a cohort of 75 placentas from obstetric pathologies. Primary EVT and HTR8/SVneo cells carrying STOX1 Y153H secreted lower levels of IL (interleukin) 6, and IL-8, and higher CXCL16 (chemokine [C-X-C motif] ligand 16) and TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) than wild-type EVT and Swan71 cells. Media from wild-type EVT or Swan71 cells transfected with wild-type STOX1 stimulated: endothelial chemokine expression, angiogenesis, and decidual natural killer cell and monocyte migration. In contrast, Y153H EVT conditioned medium, Swan71 transfected with the Y153H plasmid, or HTR8/SVneo media had no effect. Genotyping of placental decidual cocultures demonstrated association of the placental STOX1 CC allele with failed vascular remodeling. Decidual GG NODAL R165H increased in failed cocultures carrying the placental CC alleles of STOX1. Multivariate analysis of the placental cohort showed that the STOX1 C allele correlated with premature birth, with or without severe early-onset preeclampsia, and small for gestational age babies. In conclusion, placental STOX1 Y153H is a precipitating factor in preterm birth and placental preeclampsia due to defects in early utero-placental development.

Manufacturing drug co-loaded liposomal formulations targeting breast cancer: Influence of preparative method on liposomes characteristics and in vitro toxicity

Developing more efficient manufacturing methods for nano therapeutic systems is becoming important, not only to better control their physico-chemical characteristics and therapeutic efficacy but also to ensure scale-up is cost-effective. The principle of cross-flow chemistry allows precise control over manufacturing parameters for the fabrication of uniform liposomal formulations, as well as providing reproducible manufacturing scale-up compared to conventional methods. We have herein investigated the use of microfluidics to produce PEGylated DSPC liposomes loaded with doxorubicin and compared their performance against identical formulations prepared by the thin-film method. The isoprenylated coumarin umbelliprenin was selected as a co-therapeutic. Umbelliprenin-loaded and doxorubicin:umbelliprenin co-loaded liposomes were fabricated using the optimised microfluidic set-up. The role of umbelliprenin as lipid bilayer fluidity modulation was characterized, and we investigated its role on liposomes size, size distribution, shape and stability compared to doxorubicin-loaded liposomes. Finally, the toxicity of all liposomal formulations was tested on a panel of human breast cancer cells (MCF-7, MDA-MB 231, BT-474) to identify the most potent formulation by liposomal fabrication method and loaded compound(s). We herein show that the microfluidic system is an alternative method to produce doxorubicin:umbelliprenin co-loaded liposomes, allowing fine control over liposome size (100-250 nm), shape, uniformity and doxorubicin drug loading (>80%). Umbelliprenin was shown to confer fluidity to model lipid biomembranes, which helps to explain the more homogeneous size and shape of co-loaded liposomes compared to liposomes without umbelliprenin. The toxicity of doxorubicin:umbelliprenin co-loaded liposomes was lower than that of free doxorubicin, due to the delayed release of doxorubicin from liposomes. An alternative, rapid and easy manufacturing method for the production of liposomes has been established using microfluidics to effectively produce uniform doxorubicin:umbelliprenin co-loaded liposomal formulations with proven cytotoxicity in human breast cancer cell lines in vitro.

The role of insulin-like growth factor 2 receptor-mediated homeobox gene expression in human placental apoptosis, and its implications in idiopathic fetal growth restriction

Fetal growth restriction (FGR) is caused by poor placental development and function early in gestation. It is well known that placentas from women with FGR exhibit reduced cell growth, elevated levels of apoptosis and perturbed expression of the growth factors, cytokines and the homeobox gene family of transcription factors. Previous studies have reported that insulin-like growth factor-2 (IGF2) interacts with its receptor-2 (IGF2R) to regulate villous trophoblast survival and apoptosis. In this study, we hypothesized that human placental IGF2R-mediated homeobox gene expression is altered in FGR and contributes to abnormal trophoblast function. This study was designed to determine the association between IGF2R, homeobox gene expression and cell survival in pregnancies affected by FGR. Third trimester placentas were collected from FGR-affected pregnancies (n = 29) and gestation matched with control pregnancies (n = 30). Functional analyses were then performed in vitro using term placental explants (n = 4) and BeWo trophoblast cells. mRNA expression was determined by real-time PCR, while protein expression was examined by immunoblotting and immunohistochemistry. siRNA transfection was used to silence IGF2R expression in placental explants and the BeWo cell-line. cDNA arrays were used to screen for downstream targets of IGF2R, specifically homeobox gene transcription factors and apoptosis-related genes. Functional effects of silencing IGF2R were then verified by β-hCG ELISA, caspase activity assays and a real-time electrical cell-impedance assay for differentiation, apoptosis and cell growth potential, respectively. IGF2R expression was significantly decreased in placentas from pregnancies complicated by idiopathic FGR (P < 0.05 versus control). siRNA-mediated IGF2R knockdown in term placental explants and the trophoblast cell line BeWo resulted in altered expression of homeobox gene transcription factors, including increased expression of distal-less homeobox gene 5 (DLX5), and decreased expression of H2.0-Like Homeobox 1 (HLX) (P < 0.05 versus control). Knockdown of IGF2R transcription increased the expression and activity of caspase-6 and caspase-8 in placental explants, decreased BeWo proliferation and increased BeWo differentiation (all P < 0.05 compared to respective controls). This is the first study linking IGF2R placental expression with changes in the expression of homeobox genes that control cellular signalling pathways responsible for increased trophoblast cell apoptosis, which is a characteristic feature of FGR.

Tetramethoxystilbene-Loaded Liposomes Restore Reactive-Oxygen-Species-Mediated Attenuation of Dilator Responses in Rat Aortic Vessels Ex vivo

The methylated analogue of the polyphenol resveratrol (RV), 2,3′,4,5′-tetramethoxystilbene (TMS) displays potent antioxidant properties and is an effective cytochrome P450 (CYP) 1B1 inhibitor. The bioavailability of TMS is low. Therefore, the use of liposomes for the encapsulation of TMS is a promising delivery modality for enhanced uptake into tissues. We examined the effect of delivery of TMS in liposomes on the restoration of vasodilator responses of isolated aortic vessels after acute tension elevation ex vivo. Aortic vessels from young male Wistar rats were isolated, and endothelial-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) responses assessed. Acute tension elevation (1 h) significantly reduced ACh dilator responses, which were restored following incubation with superoxide dismutase or apocynin (an NADPH oxidase inhibitor). Incubation with TMS-loaded liposomes (mean diameter 157 ± 6 nm; PDI 0.097) significantly improved the attenuated dilator responses following tension elevation, which was sustained over a longer period (4 h) when compared to TMS solution. Endothelial denudation or co-incubation with L-NNA (Nω-nitro-l-arginine; nitric oxide synthase inhibitor) resulted in loss of dilator function. Our findings suggest that TMS-loaded liposomes can restore attenuated endothelial-dependent dilator responses induced by an oxidative environment by reducing NADPH-oxidase-derived ROS and potentiating the release of the vasodilator nitric oxide. TMS-loaded liposomes may be a promising therapeutic strategy to restore vasodilator function in vascular disease.

IGF signalling and endocytosis in the human villous placenta in early pregnancy as revealed by comparing quantum dot conjugates with a soluble ligand

A complex combination of trafficking and signalling occurs at the surface of the placenta. The system delivers maternal nutrients to the fetus and facilitates gaseous exchange, whilst mediating signal transduction to support and stimulate the growth of the placenta itself. IGF-I is acknowledged as a maternally-derived ligand important in the regulation of placental growth. Here we show that quantum dots bearing IGF can stimulate IGF receptor (IGF1R) phosphorylation in the syncytio- (maternal-facing) and cyto- (fetal-facing) trophoblast bilayer that forms the outer boundary of the placenta, in a distribution similar to the one resulting from exposure to a soluble ligand. The conjugates are internalised by a clathrin-dependent pathway and delivered to a syncytioplasmic compartment that differs from conventional late endosomes and lysosomes. Two discrete downstream responses are evident in different cellular compartments: phosphorylation of P70S6K in the non-proliferative syncytiotrophoblast and of AKT in the cytotrophoblast. Co-conjugation of IGF-quantum dots with an RGD-containing ligand permits penetration beyond the syncytium, into the cytoplasm of the underlying cytotrophoblast. These data reveal the existence of a trans-syncytial pathway that allows maternal mitotic signals to penetrate to the inner progenitor cells, which must proliferate to support placental and consequently fetal growth.

Delineating differential regulatory signatures of the human transcriptome in the choriodecidua and myometrium at term labor

Preterm deliveries remain the leading cause of neonatal morbidity and mortality. Current therapies target only myometrial contractions and are largely ineffective. As labor involves multiple coordinated events across maternal and fetal tissues, identifying fundamental regulatory pathways of normal term labor is vital to understanding successful parturition and consequently labor pathologies. We aimed to identify transcriptomic signatures of human normal term labor of two tissues: in the fetal-facing choriodecidua and the maternal myometrium. Microarray transcriptomic data from choriodecidua and myometrium following term labor were analyzed for functional hierarchical networks, using Cytoscape 2.8.3. Hierarchically high candidates were analyzed for their regulatory casual relationships using Ingenuity Pathway Analysis. Selected master regulators were then chemically inhibited and effects on downstream targets were assessed using real-time quantitative PCR (RT-qPCR). Unbiased network analysis identified upstream molecular components in choriodecidua including vimentin, TLR4, and TNFSF13B. In the myometrium, candidates included metallothionein 2 (MT2A), TLR2, and RELB. These master regulators had significant differential gene expression during labor, hierarchically high centrality in community cluster networks, interactions amongst the labor gene set, and strong causal relationships with multiple downstream effects. In vitro experiments highlighted MT2A as an effective regulator of labor-associated genes. We have identified unique potential regulators of the term labor transcriptome in uterine tissues using a robust sequence of unbiased mathematical and literature-based in silico analyses. These findings encourage further investigation into the efficacy of predicted master regulators in blocking multiple pathways of labor processes across maternal and fetal tissues, and their potential as therapeutic approaches.

The use of tail-anchored protein chimeras to enhance liposomal cargo delivery

Background

Liposomes are employed as drug delivery vehicles offering a beneficial pharmacokinetic/distribution mechanism for in vivo therapeutics. Therapeutic liposomes can be designed to target specific cell types through the display of epitope-specific targeting peptides on their surface. The majority of peptides are currently attached by chemical modification of lipid constituents. Here we investigate an alternative and novel method of decorating liposomes with targeting ligand, using remotely and spontaneously inserting chimeric tail-anchored membrane (TA) proteins to drug loaded liposomes.

Methods and results

An artificial TA protein chimera containing the transmembrane domain from the spontaneously inserting TA protein cytochrome b5 (Cytb5) provided a robust membrane tether for the incorporation of three different targeting moieties into preformed liposomes. The moieties investigated were the transactivator of transcription (TAT) peptide, the EGF-receptor binding sequence GE11 and the placental and tumour homing ligand CCGKRK. In all cases, TA protein insertion neither significantly altered the size of the liposomes nor reduced drug loading. The efficacy of this novel targeted delivery system was investigated using two human cell lines, HeLa M and BeWo. Short term incubation with one ligand-modified TA chimera, incorporating the TAT peptide, significantly enhanced liposomal delivery of the encapsulated carboxyfluorescein reporter.

Conclusion

The Cytb5 TA was successfully employed as a membrane anchor for the incorporation of the desired peptide ligands into a liposomal drug delivery system, with minimal loss of cargo during insertion. This approach therefore provides a viable alternative to chemical conjugation and its potential to accommodate a wider range of targeting ligands may provide an opportunity for enhancing drug delivery.

Failure of Decidualization and Maternal Immune Tolerance Underlies Uterovascular Resistance in Intra Uterine Growth Restriction

Failure of uterine vascular transformation is associated with pregnancy complications including Intra Uterine Growth Restriction (IUGR). The decidua and its immune cell populations play a key role in the earliest stages of this process. Here we investigate the hypothesis that abnormal decidualization and failure of maternal immune tolerance in the second trimester may underlie the uteroplacental pathology of IUGR. Placental bed biopsies were obtained from women undergoing elective caesarian delivery of a healthy term pregnancy, an IUGR pregnancy or a pregnancy complicated by both IUGR and preeclampsia. Decidual tissues were also collected from second trimester terminations from women with either normal or high uterine artery Doppler pulsatile index (PI). Immunohistochemical image analysis and flow cytometry were used to quantify vascular remodeling, decidual leukocytes and decidual status in cases vs. controls. Biopsies from pregnancies complicated by severe IUGR with a high uterine artery pulsatile index (PI) displayed a lack of: myometrial vascular transformation, interstitial, and endovascular extravillous trophoblast (EVT) invasion, and a lower number of maternal leukocytes. Apoptotic mural EVT were observed in association with mature dendritic cells and T cells in the IUGR samples. Second trimester pregnancies with high uterine artery PI displayed a higher incidence of small for gestational age fetuses; a skewed decidual immunology with higher numbers of; CD8 T cells, mature CD83 dendritic cells and lymphatic vessels that were packed with decidual leukocytes. The decidual stromal cells (DSCs) failed to differentiate into the large secretory DSC in these cases, remaining small and cuboidal and expressing lower levels of the nuclear progesterone receptor isoform B, and DSC markers Insulin Growth Factor Binding protein-1 (IGFBP-1) and CD10 as compared to controls. This study shows that defective progesterone mediated decidualization and a hostile maternal immune response against the invading endovascular EVT contribute to the failure of uterovascular remodeling in IUGR pregnancies.

Decidual leucocytes infiltrating human spiral arterioles are rich source of matrix metalloproteinases and degrade extracellular matrix in vitro and in situ

PROBLEM

During pregnancy, the decidual spiral arterioles (SpAs) that supply maternal blood to the placenta undergo a series of changes to optimise the transfer of nutrients and oxygen to the developing foetus. Recent studies have shown that initiation of SpA transformation coincides with decidual leucocyte infiltration. Leucocytes are known to be a source of matrix metalloproteinases (MMPs); however, the complete profile of MMPs expressed by decidual NK cells (dNK) and macrophages has not been characterised. We hypothesised that leucocyte-derived MMPs contribute to SpA remodelling.

METHODS

Decidual NK cells and macrophages were isolated from first trimester decidua and their MMP repertoire profiled by qRT-PCR (n = 10; 5-11 weeks). Dual immunofluorescence was used to localise MMP expression in situ (n = 3; 5-12 weeks). Gelatin zymography was carried out to assess whether leucocyte-derived MMPs can degrade ECM. In situ zymography and immunofluorescence identified MMP activity in tissue-resident dNK and macrophages.

RESULTS

Decidual NK cells cells and macrophages expressed MMP2, -7, -9, -11, -16, -19 and tissue inhibitors of metalloproteinase-1, -2, and -3. Both cell types degraded gelatin using MMP2 and MMP9 and broke down collagen in an in vitro model of the SpA. Extravillous trophoblasts (EVTs) expressed a similar repertoire of MMPs.

CONCLUSION

We suggest that matrix remodelling in SpA is initiated by infiltrating leucocytes, while EVTs become involved at later stages.

An investigation of mechanical nociceptive thresholds in dogs with hind limb joint pain compared to healthy control dogs

This study investigated the effects of osteoarthritis (OA) on somatosensory processing in dogs using mechanical threshold testing. A pressure algometer was used to measure mechanical thresholds in 27 dogs with presumed hind limb osteoarthritis and 28 healthy dogs. Mechanical thresholds were measured at the stifles, radii and sternum, and were correlated with scores from an owner questionnaire and a clinical checklist, a scoring system that quantified clinical signs of osteoarthritis. The effects of age and bodyweight on mechanical thresholds were also investigated. Multiple regression models indicated that, when bodyweight was taken into account, dogs with presumed osteoarthritis had lower mechanical thresholds at the stifles than control dogs, but not at other sites. Non-parametric correlations showed that clinical checklist scores and questionnaire scores were negatively correlated with mechanical thresholds at the stifles. The results suggest that mechanical threshold testing using a pressure algometer can detect primary, and possibly secondary, hyperalgesia in dogs with presumed osteoarthritis. This suggests that the mechanical threshold testing protocol used in this study might facilitate assessment of somatosensory changes associated with disease progression or response to treatment.

Selective Targeting of a Novel Vasodilator to the Uterine Vasculature to Treat Impaired Uteroplacental Perfusion in Pregnancy

Fetal growth restriction (FGR) in pregnancy is commonly caused by impaired uteroplacental blood flow. Vasodilators enhance uteroplacental perfusion and fetal growth in humans and animal models; however, detrimental maternal and fetal side effects have been reported. We hypothesised that targeted uteroplacental delivery of a vasodilator would enhance drug efficacy and reduce the risks associated with drug administration in pregnancy. Phage screening identified novel peptides that selectively accumulated in the uteroplacental vasculature of pregnant mice. Following intravenous injection, the synthetic peptide CNKGLRNK selectively bound to the endothelium of the uterine spiral arteries and placental labyrinth in vivo; CNKGLRNK-decorated liposomes also selectively bound to these regions. The nitric oxide donor 2-[[4-[(nitrooxy)methyl]benzoyl]thio]-benzoic acid methyl ester (SE175) induced significant relaxation of mouse uterine arteries and human placental arteries in vitro; thus, SE175 was encapsulated into these targeted liposomes and administered to healthy pregnant C57BL/6J mice or endothelial nitric oxide synthase knockout (eNOS-/-) mice, which exhibit impaired uteroplacental blood flow and FGR. Liposomes containing SE175 (0.44mg/kg) or PBS were administered on embryonic (E) days 11.5, 13.5, 15.5 and 17.5; fetal and placental weights were recorded at term and compared to mice injected with free PBS or SE175. Targeted uteroplacental delivery of SE175 had no effect on fetal weight in C57BL/6J mice, but significantly increased fetal weight and mean spiral artery diameter, and decreased placental weight, indicative of improved placental efficiency, in eNOS-/- mice; free SE175 had no effect on fetal weight or spiral artery diameter. Targeted, but not free SE175 also significantly reduced placental expression of 4-hydroxynonenal, cyclooxygenase-1 and cyclooxygenase-2, indicating a reduction in placental oxidative stress. These data suggest that exploiting vascular targeting peptides to selectively deliver SE175 to the uteroplacental vasculature may represent a novel treatment for FGR resulting from impaired uteroplacental perfusion.

Placental Homing Peptide-microRNA Inhibitor Conjugates for Targeted Enhancement of Intrinsic Placental Growth Signaling

Suboptimal placental growth and development are the underlying cause of many pregnancy complications. No treatments are available, primarily due to the risk of causing fetal teratogenicity. microRNAs (miRNAs) are short, non-coding RNA sequences that regulate multiple downstream genes; miR-145 and miR675 have previously been identified as negative regulators of placental growth. In this proof of principle study, we explored the feasibility of delivering miRNA inhibitors to the placentas of pregnant mice and developed novel placental homing peptide-microRNA inhibitor conjugates for targeted enhancement of intrinsic placental growth signalling. Scrambled-, miR-145- or miR-675 inhibitor sequences were synthesised from peptide nucleic acids and conjugated to the placental homing peptide CCGKRK. Intravenous administration of the miR-145- and miR-675 conjugates to pregnant C57BL/6J mice significantly increased fetal and placental weights compared to controls; the miR-675 conjugate significantly reduced placental miR-675 expression. When applied to human first trimester placental explants, the miR-145 conjugate significantly reduced placental miR-145 expression, and both conjugates induced significant enhancement of cytotrophoblast proliferation; no effect was observed in term placental explants. This study demonstrates that homing peptide-miRNA inhibitor conjugates can be exploited to promote placental growth; these novel therapeutics may represent an innovative strategy for targeted treatment of compromised placental development.

Extravillous Trophoblast and Endothelial Cell Crosstalk Mediates Leukocyte Infiltration to the Early Remodeling Decidual Spiral Arteriole Wall

Decidual spiral arteriole (SpA) remodeling is essential to ensure optimal uteroplacental blood flow during human pregnancy, yet very little is known about the regulatory mechanisms. Uterine decidual NK (dNK) cells and macrophages infiltrate the SpAs and are proposed to initiate remodeling before colonization by extravillous trophoblasts (EVTs); however, the trigger for their infiltration is unknown. Using human first trimester placenta, decidua, primary dNK cells, and macrophages, we tested the hypothesis that EVTs activate SpA endothelial cells to secrete chemokines that have the potential to recruit maternal immune cells into SpAs. Gene array, real-time PCR, and ELISA analyses showed that treatment of endothelial cells with EVT conditioned medium significantly increased production of two chemokines, CCL14 and CXCL6. CCL14 induced chemotaxis of both dNK cells and decidual macrophages, whereas CXCL6 also induced dNK cell migration. Analysis of the decidua basalis from early pregnancy demonstrated expression of CCL14 and CXCL6 by endothelial cells in remodeling SpAs, and their cognate receptors are present in both dNK cells and macrophages. Neutralization studies identified IL-6 and CXCL8 as factors secreted by EVTs that induce endothelial cell CCL14 and CXCL6 expression. This study has identified intricate crosstalk between EVTs, SpA cells, and decidual immune cells that governs their recruitment to SpAs in the early stages of remodeling and has identified potential key candidate factors involved. This provides a new understanding of the interactions between maternal and fetal cells during early placentation and highlights novel avenues for research to understand defective SpA remodeling and consequent pregnancy pathology.

Tumor-homing peptides as tools for targeted delivery of payloads to the placenta

The availability of therapeutics to treat pregnancy complications is severely lacking mainly because of the risk of causing harm to the fetus. As enhancement of placental growth and function can alleviate maternal symptoms and improve fetal growth in animal models, we have developed a method for targeted delivery of payloads to the placenta. We show that the tumor-homing peptide sequences CGKRK and iRGD bind selectively to the placental surface of humans and mice and do not interfere with normal development. Peptide-coated nanoparticles intravenously injected into pregnant mice accumulated within the mouse placenta, whereas control nanoparticles exhibited reduced binding and/or fetal transfer. We used targeted liposomes to efficiently deliver cargoes of carboxyfluorescein and insulin-like growth factor 2 to the mouse placenta; the latter significantly increased mean placental weight when administered to healthy animals and significantly improved fetal weight distribution in a well-characterized model of fetal growth restriction. These data provide proof of principle for targeted delivery of drugs to the placenta and provide a novel platform for the development of placenta-specific therapeutics.

Changes in vascular extracellular matrix composition during decidual spiral arteriole remodeling in early human pregnancy

Uterine spiral arteriole (SA) remodeling in early pregnancy involves a coordinated series of events including decidual immune cell recruitment, vascular cell disruption and loss, and colonization by placental-derived extravillous trophoblast (EVT). During this process, decidual SA are converted from narrow, muscular vessels into dilated channels lacking vasomotor control. We hypothesized that this extensive alteration in SA architecture must require significant reorganization and/or breakdown of the vascular extracellular matrix (ECM). First trimester decidua basalis (30 specimens) was immunostained to identify spiral arterioles undergoing trophoblast-independent and -dependent phases of remodeling. Serial sections were then immunostained for a panel of ECM markers, to examine changes in vascular ECM during the remodeling process. The initial stages of SA remodeling were characterized by loss of laminin, elastin, fibrillin, collagen types III, IV and VI from the basement membrane, vascular media and/or adventitia, and surrounding decidual stromal cells. Loss of ECM correlated with disruption and disorganization of vascular smooth muscle cells, and the majority of changes occurred prior to extensive colonization of the vessel wall by EVT. The final stages of SA remodeling, characterized by the arrival of EVT, were associated with the increased mural deposition of fibronectin and fibrinoid. This study provides the first detailed analysis of the spatial and temporal loss of ECM from the walls of remodeling decidual SA in early pregnancy.

Human dNK cell function is differentially regulated by extrinsic cellular engagement and intrinsic activating receptors in first and second trimester pregnancy

Decidual natural killer (dNK) cells express an array of activation receptors to regulate placental immunity and development during early pregnancy. We investigated the functional character of human dNK cells during the first and second trimester of gestation and the interaction between dNK and trophoblast cells. Although the frequency of CD56⁺CD16^- dNK among the total CD45⁺ leukocytes did not change over this period, the expression of the activating receptors, NKp80 and NKG2D, was greatly upregulated. We observed a significantly higher number of extravillous trophoblast cells in proximity to the dNK cells in the first trimester in comparison with the second trimester decidua. NKG2D expression by first trimester dNK cells was decreased when co-cultured with the HTR-8 trophoblast cell line. In the second trimester, functional markers of dNK activation, i.e., angiogenic factor production (e.g., vascular endothelial growth factor, interleukin-8, interferon-gamma), remained stable despite an increase in NKp80 or NKG2D surface expression. Furthermore, the degranulation capacity of dNK cells, as assessed by CD107a, was decreased in the second trimester. We suggest that in the first trimester, trophoblast-dNK interactions generate a population of dNK cells with a suppressed activating phenotype. In the second trimester, the loss of trophoblast-dNK interactions led to the inhibition of dNK cell function, although their activating receptor expression was increased. We speculate that during pregnancy, two mechanisms operate to modulate the dNK cell activation:suppression of activating receptor levels in the first trimester by trophoblasts and disengagement of receptor-ligand coupling in the second trimester.

Transcriptomic profiling of human choriodecidua during term labor: inflammation as a key driver of labor

PROBLEM

Inflammation is a driver of labor in myometrium and cervix; however, the involvement of decidua is poorly defined. We have reported decidual leukocyte infiltration prior to and during labor; the regulators of these inflammatory processes are unknown.

METHOD OF STUDY

Choriodecidua RNA obtained after term labor or elective cesarean delivery was applied to Affymetrix GeneChips. Pathway analysis and gene validation were performed.

RESULTS

Extensive inflammatory activation was identified in choriodecidua following labor, predominantly upregulation of genes regulating leukocyte trafficking and cytokine signalling. Genes governing cell fate, tissue remodelling, and translation were also altered. Upregulation of candidate genes (ICAM1, CXCR4, CD44, TLR4, SOCS3, BCL2A, and IDO) was confirmed. NFκB, STAT1&3, HMGB1, and miRNA-21, miRNA-46, miRNA-141, and miRNA-200 were predicted upstream regulators.

CONCLUSION

This study confirms inflammatory processes are major players in labor events in choriodecidua, as in other gestational tissues. Suppressing uterine inflammation is likely to be critical for arresting premature labor.

Elastin-derived peptides stimulate trophoblast migration and invasion: a positive feedback loop to enhance spiral artery remodelling

Elastin breakdown in the walls of uterine spiral arteries during early pregnancy facilitates their transformation into dilated, high-flow, low-resistance channels. Elastin-derived peptides (EDP) can influence cell migration, invasion and protease activity, and so we hypothesized that EDP released during elastolysis promote extravillous trophoblast (EVT) invasion and further elastin breakdown. Treatment of the trophoblast cell line SGHPL4 with the elastin-derived matrikine VGVAPG (1 μg/ml) significantly increased total elastase activity, promoted migration in a wound healing assay and increased invasion through Matrigel-coated transwells compared with vehicle control (0.1% DMSO) or the scrambled sequence VVGPGA. Furthermore, treatment of first-trimester placental villous explants with this EDP significantly increased both the area of trophoblast outgrowth and distance of migration away from the villous tips. Primary first-trimester cytotrophoblast exposed to VGVAPG (1 μg/ml) for 30 min showed increased phosphorylation of endothelial nitric oxide synthase and activation of the mitogen activated protein kinase pathway, events also associated with tumour cell migration and invasion. These in vitro observations suggest liberation of bioactive EDP during induction of elastolysis in the uterine spiral arteries may orchestrate a positive feedback loop that promotes EVT invasion and further elastin breakdown, contributing to the process of vascular remodelling.

A role for the mitochondrial-associated protein p32 in regulation of trophoblast proliferation

p32 is a conserved eukaryotic protein which is primarily expressed in the mitochondria and regulates cell proliferation, migration and metabolism in various tissues. In this study, we sought to examine the expression and function of p32 in the human placenta. p32 was highly expressed in the syncytiotrophoblast, the underlying cytotrophoblast (CTB), the vascular endothelium and by a proportion of cells in the villous stroma in first trimester and term placenta. p32 mRNA and protein expression was significantly higher in the first trimester of pregnancy than at term, and expression in the trophoblast was significantly reduced in placentas from women with fetal growth restriction (FGR). Small interfering RNA (siRNA)-mediated knockdown of p32 in term placental explants significantly reduced the number of Ki67-positive CTB, but did not alter CTB apoptosis or necrosis. p32 knockdown increased lactate production, reduced glucose extraction from culture medium and was associated with reduced MitoTracker dye accumulation in trophoblast mitochondria. p32 knockdown was also associated with a significant reduction in expression of the mitochondrial respiratory complexes I and IV. These data suggest that p32 expression is important for CTB proliferation, via a mechanism involving regulation of normal mitochondrial function. As p32 expression is reduced in FGR placentas, this may contribute to some of the observed placental pathology, such as reduced CTB proliferation and mitochondrial dysfunction.

Uterine natural killer cells initiate spiral artery remodeling in human pregnancy

Uterine spiral artery remodeling is required for successful human pregnancy; impaired remodeling is associated with pregnancy complications, including late miscarriage, preeclampsia, and fetal growth restriction. The molecular triggers of remodeling are not known, but it is now clear that there are "trophoblast-independent" and "trophoblast-dependent" stages. Uterine natural killer (uNK) cells are abundant in decidualized endometrium in early pregnancy; they surround spiral arteries and secrete a range of angiogenic growth factors. We hypothesized that uNK cells mediate the initial stages of spiral artery remodeling. uNK cells and extravillous trophoblast (EVT) cells were isolated from early pregnancy decidua and placenta. Chorionic plate arteries from full-term placentas and spiral arteries from nonpregnant myometrium were cultured with angiogenic growth factors or conditioned medium (CM) from uNK cells or EVT or uNK cell/EVT cocultures. In both vessel models, uNK cell CM induced disruption of vascular smooth muscle cells (VSMCs) and breakdown of extracellular matrix components. Angiopoietin (Ang)-1, Ang-2, interferon-γ, and VEGF-C also disrupted VSMC integrity with an Ang-2 inhibitor abrogating the effect of uNK cell CM. These results provide compelling evidence that uNK cells contribute to the early stages of spiral artery remodeling; failure of this process could contribute to pregnancy pathology.

Biology and significance of signalling pathways activated by IGF-II

Insulin-like growth factor-II (IGF-II) affects many aspects of cellular function through its ability to activate several different receptors and, consequently, numerous intracellular signalling molecules. Thus, IGF-II is a key regulator of normal foetal development and growth. However, abnormalities in IGF-II function are associated with cardiovascular disease and cancer. Here, we review the cellular mechanisms by which IGF-II's physiological and pathophysiological actions are exerted by discussing the involvement of the type 1 and type 2 IGF receptors (IGF1R and IGF2R), the insulin receptor and the downstream MAP kinase, PI-3 kinase and G-protein-coupled signalling pathways in mediating IGF-II stimulated cellular proliferation, survival, differentiation and migration.

IFPA Meeting 2010 Workshop Report I: Immunology; ion transport; epigenetics; vascular reactivity; epitheliochorial placentation; proteomics

Workshops are an important part of the IFPA annual meeting. At IFPA Meeting 2010 there were twelve themed workshops, six of which are summarized in this report. 1. The immunology workshop focused on normal and pathological functions of the maternal immune system in pregnancy. 2. The transport workshop dealt with regulation of ion and water transport across the syncytiotrophoblast of human placenta. 3. The epigenetics workshop covered DNA methylation and its potential role in regulating gene expression in placental development and disease. 4. The vascular reactivity workshop concentrated on methodological approaches used to study placental vascular function. 5. The workshop on epitheliochorial placentation covered current advances from in vivo and in vitro studies of different domestic species. 6. The proteomics workshop focused on a variety of techniques and procedures necessary for proteomic analysis and how they may be implemented for placental research.

IFPA Gabor Than Award lecture: Transformation of the spiral arteries in human pregnancy: key events in the remodelling timeline

During human pregnancy, the uterine spiral arteries are progressively remodelled to form dilated conduits lacking maternal vasomotor control. This phenomenon ensures that a constant supply of blood is delivered to the materno-fetal interface at an optimal velocity for nutrient exchange. Conversion of a tonic maternal arteriole composed of multiple layers of vascular smooth muscle, elastin and numerous other extracellular matrix components, into a highly dilated yet durable vessel, requires tight regulatory control and the coordinated actions of multiple cell types. Initial disruption of the vascular wall, characterised by foci of endothelial cell loss, and separation and misalignment of vascular smooth muscle cells (VSMC), is coincident with an influx of uterine natural killer (uNK) cells and macrophages. uNK cells are a source of angiogenic growth factors and matrix degrading proteases, thus they possess the capacity to initiate changes in VSMC phenotype and instigate extracellular matrix catabolism. However, complete vascular cell loss, mediated in part by apoptosis and dedifferentiation, is only achieved following colonisation of the arteries by extravillous trophoblast (EVT). EVT produce a variety of chemokines, cytokines and matrix degrading proteases, enabling them to influence the fate of other cells within the placental bed and complete the remodelling process. The complex interplay of cell-cell and cell-matrix interactions required for effective vascular transformation will be examined, with a particular focus on the role of (i) uNK cells and (ii) the enzyme matrix metalloproteinase-12 (MMP-12). Parallels with remodelling events occurring in other vascular beds will also be drawn.

IGF2 actions on trophoblast in human placenta are regulated by the insulin-like growth factor 2 receptor, which can function as both a signaling and clearance receptor

Insulin-like growth factor 2 (IGF2) enhances proliferation and survival of human first-trimester cytotrophoblasts (CTB) by signaling through the insulin-like growth factor 1 receptor (IGF1R). However, the role of the IGF2 receptor (IGF2R) in regulating trophoblast kinetics is unclear: It could act as a clearance receptor for trafficking excess ligand to lysosomes for degradation and/or directly mediate IGF2 signaling. We used an IGF2R knockdown strategy in BeWo cells and placental villous explants to investigate trophoblast proliferation and survival in response to stimulation by IGF. Both IGF1 and IGF2 significantly (P < 0.001) increased mitosis and reduced apoptosis in serum-starved BeWo cells. Small interfering RNA (siRNA)-mediated knockdown of IGF2R further enhanced IGF2-stimulated mitosis (P < 0.01), and IGF2-mediated rescue of apoptosis (P < 0.001) in these cells. Leu(27)IGF2, an IGF2 analogue that binds to IGF2R but not IGF1R, also protected IGF2R-expressing BeWo cells from apoptosis but did not increase mitosis. IGF treatment of term placental villous explants with reduced syncytial expression of IGF2R increased CTB proliferation (P < 0.001) and decreased apoptosis (P < 0.01) compared to untreated controls. Moreover, IGF2-mediated rescue of CTB apoptosis was significantly greater than that in tissue with normal IGF2R expression. Leu(27)IGF2 promoted mitogenesis and survival only in explants with intact IGF2R expression. Given that altered CTB turnover is observed in pregnancies complicated by fetal growth restriction, the development of strategies to manipulate the IGF2R signaling axis in the syncytiotrophoblast may provide a therapeutic avenue for treating this condition.

Trophoblast- and vascular smooth muscle cell-derived MMP-12 mediates elastolysis during uterine spiral artery remodeling

During the first trimester of pregnancy, the uterine spiral arteries are remodeled, creating heavily dilated conduits that lack maternal vasomotor control but allow the placenta to meet an increasing requirement for nutrients and oxygen. To effect permanent vasodilatation, the internal elastic lamina and medial elastin fibers must be degraded. In this study, we sought to identify the elastolytic proteases involved in this process. Primary first-trimester cytotrophoblasts (CTBs) derived from the placenta exhibited intracellular and membrane-associated elastase activity; membrane-associated activity was primarily attributable to matrix metalloproteinases (MMP). Indeed, Affymetrix microarray analysis and immunocytochemistry implicated MMP-12 (macrophage metalloelastase) as a key mediator of elastolysis. Cultured human aortic smooth muscle cells (HASMCs) exhibited constitutive membrane-associated elastase activity and inducible intracellular elastase activity; these cells also expressed MMP-12 protein. Moreover, a specific inhibitor of MMP-12 significantly reduced CTB- and HASMC-mediated elastolysis in vitro, to 31.7 ± 10.9% and 23.3 ± 8.7% of control levels, respectively. MMP-12 is expressed by both interstitial and endovascular trophoblasts in the first-trimester placental bed and by vascular SMCs (VSMCs) in remodeling spiral arteries. Perfusion of isolated spiral artery segments with CTB-conditioned medium stimulated MMP-12 expression in medial VSMCs. Our data support a model in which trophoblasts and VSMCs use MMP-12 cooperatively to degrade elastin during vascular remodeling in pregnancy, with the localized release of elastin peptides and CTB-derived factors amplifying elastin catabolism.

Review: Trophoblast-vascular cell interactions in early pregnancy: how to remodel a vessel

During the first twenty weeks of human pregnancy, extravillous trophoblasts (EVT) colonise the decidua and remodel the uterine spiral arteries as far as the first third of the myometrium. This process leads to an irreversible vasodilatation, ensuring that maximal blood flow is delivered to the materno-fetal interface at an optimal velocity for nutrient exchange. There is accumulating evidence that subtle changes in vascular structure precede EVT colonisation; however, full physiological transformation is only achieved in the presence of trophoblast. This review discusses the mechanisms employed to facilitate arterial dilatation, including recent data regarding the contribution of vascular cell apoptosis, the importance of elastin catabolism and the source of candidate elastases. It also examines how the complex interplay between EVT, endothelial cells, smooth muscle cells and decidual leukocytes (macrophages and uterine natural killer cells) leads to enhanced receptivity to invasion, vascular cell loss and extracellular matrix remodelling.

Evidence for immune cell involvement in decidual spiral arteriole remodeling in early human pregnancy

Decidual artery remodeling is essential for a healthy pregnancy. This process involves loss of vascular smooth muscle cells and endothelium, which are replaced by endovascular trophoblasts (vEVTs) embedded in fibrinoid. Remodeling is impaired during pre-eclampsia, a disease of pregnancy that results in maternal and fetal mortality and morbidity. Early vascular changes occur in the absence of vEVTs, suggesting that another cell type is involved; evidence from animal models indicates that decidual leukocytes play a role. We hypothesized that leukocytes participate in remodeling through the triggering of apoptosis or extracellular matrix degradation. Decidua basalis samples (8 to 12 weeks gestation) were examined by immunohistochemistry to elucidate associations between leukocytes, vEVTs, and key remodeling events. Trophoblast-independent and -dependent phases of remodeling were identified. Based on a combination of morphological attributes, vessel profiles were classified into a putative temporal series of four stages. In early stages of remodeling, vascular smooth muscle cells showed dramatic disruption and disorganization before vEVT presence. Leukocytes (identified as uterine natural killer cells and macrophages) were apparent infiltrating vascular smooth muscle cells layers and were matrix metalloproteinase-7 and -9 immunopositive. A proportion of vascular smooth muscle cells and endothelial cells were terminal deoxynucleotidyl transferase dUTP nick-end labeling positive, suggesting remodeling involves apoptosis. We thus confirm that vascular remodeling occurs in distinct trophoblast-independent and -dependent stages and provide the first evidence of decidual leukocyte involvement in trophoblast-independent stages.

Trophoblast-derived heparanase is not required for invasion

To invade the decidua and myometrium, extravillous trophoblast must degrade an assortment of extracellular matrix (ECM) components. The uterine wall is rich in heparan sulphate proteoglycans (HSPG), which interact with collagen, laminin and fibronectin, and bind a variety of growth factors. HSPG are catabolised by heparanase, an enzyme that is highly expressed in the placenta. The aim of this study was to investigate the role of heparanase in first trimester trophoblast invasion. First trimester cytotrophoblasts (CTB) were isolated by trypsin digestion followed by centrifugation on a Percoll gradient. Cells were cultured on Matrigel to promote an extravillous phenotype. Heparanase expression was studied by immunohistochemistry and confocal microscopy. Trophoblast invasion was assessed using an in vitro transwell assay. A high level of heparanase was observed in isolated first trimester trophoblast; however, a function-blocking antibody did not inhibit invasion of primary CTB or the extravillous trophoblast cell line SGHPL-4 at 21% oxygen. In contrast to cancer cells, heparanase expression was not increased following culture at 3% oxygen, and trophoblast invasion was not retarded by the blocking antibody under these conditions. Heparanase expression was observed in stromal cells and vascular endothelium in first trimester parietal decidua. Expression was evident on the cell surface and in the nucleus of trophoblast and decidual cells. In conclusion, trophoblast heparanase is not required for invasion in vitro. Its abundant expression suggests another role during pregnancy, perhaps in controlling the availability of ECM-bound growth factors or acting as a transcription factor.

S-nitrosylation of proteins at the leading edge of migrating trophoblasts by inducible nitric oxide synthase promotes trophoblast invasion

Nitric oxide regulates many important cellular processes including motility and invasion. Many of its effects are mediated through the modification of specific cysteine residues in target proteins, a process called S-nitrosylation. Here we show that S-nitrosylation of proteins occurs at the leading edge of migrating trophoblasts and can be attributed to the specific enrichment of inducible nitric oxide synthase (iNOS/NOS2) in this region. Localisation of iNOS to the leading edge is co-incidental with a site of extensive actin polymerisation and is only observed in actively migrating cells. In contrast endothelial nitric oxide synthase (eNOS/NOS3) shows distribution that is distinct and non-colocalised with iNOS, suggesting that the protein S-nitrosylation observed at the leading edge is caused only by iNOS and not eNOS. We have identified MMP-9 as a potential target for S-nitrosylation in these cells and demonstrate that it co-localises with iNOS at the leading edge of migrating cells. We further demonstrate that iNOS plays an important role in promoting trophoblast invasion, which is an essential process in the establishment of a successful pregnancy.

Regulation of trophoblast invasion - a workshop report

Trophoblast invasion during placental development helps to establish efficient physiological exchange between maternal and fetal circulatory systems. Trophoblast stem cells differentiate into multiple subtypes, including some that are highly invasive. Signalling to the trophoblast from decidua, uterine natural killer cells and vascular smooth muscle can regulate extravillous trophoblast differentiation. Important questions remain about how these cellular interactions promote trophoblast invasion and the signalling pathways that are involved. New and established biological models are being used to experimentally examine these interactions and the underlying molecular mechanisms.

Vascular remodeling and extracellular matrix breakdown in the uterine spiral arteries during pregnancy

During pregnancy, trophoblasts invade and transform the maternal spiral arteries that supply blood to the placenta. Recent work has revealed that this process occurs in several stages, and details of the molecular and cellular mechanisms are beginning to emerge, including changes that precede or accompany trophoblastic colonization of the vascular media. Disruption and eventual loss of smooth muscle cells and their associated extracellular matrix are central to physiological transformation. Advances in understanding will lead to the identification of the causative factors involved in failure of remodeling in pathological pregnancies and suggest novel diagnostic and therapeutic avenues.

BeWo cells stimulate smooth muscle cell apoptosis and elastin breakdown in a model of spiral artery transformation

BACKGROUND

During pregnancy, extravillous trophoblast invades the uterine wall and enters the spiral arteries. Remodelling ensues, with loss of vascular smooth muscle cells (SMCs) to create high flow, low resistance vessels. Pregnancies complicated by pre-eclampsia are characterized by incomplete arterial remodelling. Endovascular trophoblast is not easily accessible for studies to establish the pathogenesis of pre-eclampsia, so we have developed a model appropriate to carry out mechanistic studies of vessel wall transformation.

METHODS AND RESULTS

Segments of human spiral artery were perfused with the choriocarcinoma cell line, BeWo; cells invaded the vessel wall and induced apoptosis of vascular SMC. Perfusion of vessels with BeWo-conditioned medium also induced SMC apoptosis, indicating the presence of a soluble apoptotic factor. BeWo express Fas ligand (FasL) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL). Treatment of BeWo-conditioned medium with antibodies against FasL inhibited vascular SMC apoptosis in vitro. Antibodies that blocked TRAIL receptor function had no effect. Extracellular matrix degradation is also a prerequisite for vascular remodelling; BeWo express matrix metalloproteinase-12 (MMP-12) and BeWo-conditioned medium increased MMP-12 expression in spiral artery SMC.

CONCLUSIONS

BeWo induce arterial remodelling via FasL- and MMP-12-dependent mechanisms. BeWo-derived factors up-regulate protease expression in spiral artery SMC to facilitate matrix breakdown.

Mechanism of the antioxidant to pro-oxidant switch in the behavior of dehydroascorbate during LDL oxidation by copper(II) ions

Oxidised low density lipoprotein (LDL) may be involved in the pathogenesis of atherosclerosis. We have therefore investigated the mechanisms underlying the antioxidant/pro-oxidant behavior of dehydroascorbate, the oxidation product of ascorbic acid, toward LDL incubated with Cu(2+) ions. By monitoring lipid peroxidation through the formation of conjugated dienes and lipid hydroperoxides, we show that the pro-oxidant activity of dehydroascorbate is critically dependent on the presence of lipid hydroperoxides, which accumulate during the early stages of oxidation. Using electron paramagnetic resonance spectroscopy, we show that dehydroascorbate amplifies the generation of alkoxyl radicals during the interaction of copper ions with the model alkyl hydroperoxide, tert-butylhydroperoxide. Under continuous-flow conditions, a prominent doublet signal was detected, which we attribute to both the erythroascorbate and ascorbate free radicals. On this basis, we propose that the pro-oxidant activity of dehydroascorbate toward LDL is due to its known spontaneous interconversion to erythroascorbate and ascorbate, which reduce Cu(2+) to Cu(+) and thereby promote the decomposition of lipid hydroperoxides. Various mechanisms, including copper chelation and Cu(+) oxidation, are suggested to underlie the antioxidant behavior of dehydroascorbate in LDL that is essentially free of lipid hydroperoxides.