IFPA Gabor Than Award lecture: molecular control of placental growth: the emerging role of microRNAs

Identification and validation of reference genes of circulating microRNAs for use as control in gestational toxoplasmosis

Toxoplasmosis causes serious harm to the fetus, as tachyzoite dissemination, during pregnancy in women developing the primo-infection. The microRNAs (miRNAs) are small non-coding RNAs, which have regulatory roles in cells by silencing messenger RNA. Circulating miRNA are promising biomarkers for diagnosis and prognosis of numerous diseases. The miRNAs levels are estimated by quantitative real-time PCR (qPCR), however, the relative quantification of each miRNA expression requires proper normalization methods using endogenous miRNAs as control. This study analyzed the expression of three endogenous miRNAs (miR-484, miR -423-3p and miR-26b-5p) for use as normalizers in future studies of target miRNAs for gestational toxoplasmosis (GT). A total of 32 plasma samples were used in all assays divided in 21 from women with GT and 11 from healthy women. The stability of each endogenous miRNA was evaluated by the algorithm methods RefFinder that included GeNorm, Normfinder, BestKeeper and comparative delta-CT programs. The miR-484 was the most stably gene, and equivalently expressed in GT and NC groups. These results contribute to future studies of target miRNAs in clinical samples of women with gestational toxoplasmosis.

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.

Roles of MicroRNA across Prenatal and Postnatal Periods

Communication between mother and offspring in mammals starts at implantation via the maternal-placental-fetal axis, and continues postpartum via milk targeted to the intestinal mucosa. MicroRNAs (miRNAs), short, noncoding single-stranded RNAs, of about 22 nucleotides in length, are actively involved in many developmental and physiological processes. Here we highlight the role of miRNA in the dynamic signaling that guides infant development, starting from implantation of conceptus and persisting through the prenatal and postnatal periods. miRNAs in body fluids, particularly in amniotic fluid, umbilical cord blood, and breast milk may offer new opportunities to investigate physiological and/or pathological molecular mechanisms that portend to open novel research avenues for the identification of noninvasive biomarkers.

Review: placenta-specific microRNAs in exosomes - good things come in nano-packages

MicroRNAs (miRNAs) are small noncoding RNA gene products that commonly regulate mRNA expression by repression of translation and/or transcript decay. Whereas common and unique types of miRNAs are expressed by the placenta during pregnancy, the functions of most placental miRNA species are unknown. In addition to their intracellular silencing function, miRNAs are also released to the extracellular space and systemic circulation, where they can potentially target cells to regulate mRNA and protein expression, providing a non-hormonal means of intercellular communication that contributes to tissue homeostasis and disease pathophysiology. This review centers on extracellular miRNAs that originate in trophoblasts and that could mediate crosstalk between the feto-placental unit and the mother during pregnancy. We specifically detail the function of miRNAs from the primate-specific chromosome 19 miRNA cluster. These miRNAs are highly expressed in human placentas and in the serum of pregnant women. They are also packaged into extracellular vesicles of diverse sizes, including exosomes, and endow non-trophoblastic cells with resistance to a variety of viruses.

Soluble human leukocyte antigen-g5 activates extracellular signal-regulated protein kinase signaling and stimulates trophoblast invasion

Soluble human leukocyte antigen-G (HLA-G) is a non-classical class Ib HLA molecule that is secreted from blastocysts. Soluble HLA-G modulates the immune tolerance of the mother and can be used as a prognostic factor for the clinical pregnancy rate. However, the underlying mechanism of how soluble HLA-G5 affects pregnancy remains largely unknown. We hypothesized that soluble HLA-G5 promotes successful implantation and pregnancy by modulating trophoblast invasion through receptor binding and activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Recombinant HLA-G5 protein over-expressed in E. coli BL21 was purified to near homogeneity. We studied the expression of HLA-G5 and its receptors, the leukocyte immunoglobulin-like receptor subfamily B1 (LILRB1) and killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), in primary trophoblasts and trophoblastic (JAr and JEG-3) cell lines by florescence-labeled HLA-G5. HLA-G5 was detected in the primary trophoblasts and JEG-3 cells. The LILRB1 and KIR2DL4 receptors were expressed in both primary trophoblasts and trophoblastic cell lines. HLA-G5 stimulated cell invasion (p<0.05) and increased urokinase (uPA) and matrix metalloproteinases (MMPs) transcripts and their activity (p<0.05) in trophoblastic cells. HLA-G5 activated the ERK signaling pathway and induced ERK1/2 phosphorylation in the trophoblastic cell lines. Addition of ERK inhibitors (U0126 and PD98059) nullified the stimulatory effect of HLA-G5 on trophoblastic cell invasion. Taken together, HLA-G5 induced trophoblast invasion by binding to KIR2DL4 and LILRB1, by increasing uPA and MMPs expressions and by activating the ERK signaling pathway.