Developmental differences in the expression of FGF receptors between human and mouse embryos.

INTRODUCTION: Fibroblast growth factor (FGF) signaling is essential for early trophoblast expansion and maintenance in the mouse, but is not required for trophectoderm specification during blastocyst formation. This signaling pathway is stably activated to expand the trophoblast stem cell compartment in vivo, while in vitro, FGFs are used for the derivation of trophoblast stem (TS) cells from blastocysts and early post-implantation mouse embryos. However, the function of FGFs during human trophoblast development is not known. METHODS: We sought to derive TS cells from human blastocysts in a number of culture conditions, including in the presence of FGFs and stem cell factor (SCF). We also investigated the expression of FGF receptors (FGFRs) in blastocysts, and the expression of FGFR2 and activated ERK1/2 in first trimester human placentae. RESULTS: We found that SCF, but not FGF2/4, improved the quality of blastocyst outgrowths, but we were unable to establish stable human TS cell lines. We observed CDX2 expression in the trophectoderm of fully blastocysts, but rarely observed transcription of FGFRs. FGFR2 protein was not detected in human blastocysts, but was strongly expressed in mouse blastocysts. However, we found robust FGFR2 expression and activated ERK1/2 in the cytotrophoblast layer of early human placenta. DISCUSSION: Our data suggests that initiation of FGF-dependent trophoblast expansion may occur later in human development, and is unlikely to drive maintenance of a TS cell compartment during the peri-implantation period. These findings suggest that cytotrophoblast preparations from early placentae may be a potential source of FGF-dependent human TS cells.

Enhanced endocytotic and transcytotic activity in the rat endometrium prior to embryo implantation.

BACKGROUND: Understanding the mechanisms by which fluid absorption and secretion occur in the endometrium is clinically important since conditions that deregulate this process reduce fertility. It has been suggested that luminal epithelial cells induce a crucial step in the process of embryo implantation called uterine closure via endocytotic fluid uptake. Uterine lumen closure is a key step in the process of embryo implantation and is absent in some infertile strains of mice. METHODS: To investigate the process of uterine closure a ferritin-based tracer, used as a marker of endocytosis, was injected into the uterine lumen on day 5 of pregnancy when closure occurs. RESULTS: Unexpectedly, luminal epithelial uptake of tracer was minimal on day 5 of pregnancy discrediting endocytosis as the induction method of uterine closure. In contrast, ferritin was found deep in the stromal portion of the endometrium in pre-pregnant animals. CONCLUSIONS: We have shown for the first time that uterine closure is not induced by luminal epithelial cell driven endocytosis. Another novel finding of this study was the passage of the tracer ferritin up to 15 cells deep into the endometrium suggesting an as yet unstudied mechanism by which information can be transported from the uterine lumen to the underlying stroma.

Epigenetics and imprinting of the trophoblast -- a workshop report.

Genomic imprinting is a remarkable process that causes genes to be expressed or repressed depending on their parental-origin. Imprinted genes play important roles in prenatal growth and organ development. Postnatally, imprinted genes can contribute to the regulation of metabolic pathways and behaviour associated with the control of resources. One of the most important sites of imprinted gene action is the placenta. During this workshop at the 11th meeting of the International Federation of Placenta Associations/European Placenta Group held in Glasgow, a series of short talks were presented providing an overview of the evolution, function and mechanisms of imprinting in mammals with particular reference to the placenta. In addition, epigenetic control of trophoblast development and function were considered. This report summarises the contributions to the workshop.

A new approach to immunological sexing of sperm.

A non-invasive, immunological method for sexing mammalian sperm would be of benefit to agricultural industries. This paper presents a new approach, based on the hypothesis that sex-specific proteins (SSPs) are evolutionarily more highly conserved than non-SSPs. Antibodies to non-SSPs were raised and used in an affinity procedure to remove non-SSPs and enrich for SSPs. Thereafter, using column chromatography, purified SSPs were obtained. Sex-specific antibodies (SSAbs) raised against these SSPs appear to bind to sex-chromosome-specific proteins (SCSPs) on the sperm membrane and make possible a sperm-sexing procedure. Antibodies to SCSPs were raised and used to identify putative SCSPs by affinity chromatography. The preliminary results presented here suggest that a viable immunological sperm sexing procedure can be developed.

Growth inhibition by cyclosporine A in vivo and in vitro.

Cyclosporine A is a commonly used immunosuppressant in organ transplant. However, in addition to its nephro- and hepato-toxicity, we now report that it also exerts growth inhibiting effects in vivo and in vitro. Rats treated with daily Cyclosporine A I.P. injections of 10 mg or 20 mg/kg body weight gained weight at significantly lower rates than controls over a six week period. This growth retardation was completely reversible. By 6 weeks post treatment, the body weights of the treated animals were the same as controls. In contrast, rats treated with lower doses of cyclosporine A (5 mg/kg) did not suffer any growth retardation throughout. In vitro, rat primary cultured fibroblasts treated with greater than 1 microgram/ml Cyclosporine A suffered 25-60% cell loss in the post-log phase but the cytotoxic effect was not apparent during the log phase of growth. Fibroblasts treated with less than or equal to 1 microgram/ml of Cyclosporine A did not suffer any cell loss. In conclusion, Cyclosporine A exerts growth inhibitory effects in vivo when given at greater than 5 mg/kg body weight and cytotoxic effects in vitro at greater than 1 microgram/ml.