Cord blood erythropoietin and interleukin-6 for prediction of intraventricular hemorrhage in the preterm neonate

OBJECTIVE

To evaluate cord blood erythropoietin (EPO) and interleukin-6 (IL-6) levels to predict preterm infants at risk of developing intraventricular hemorrhage (IVH).

METHODS

Levels of umbilical cord EPO, acid-base status and IL-6 were analyzed in 116 consecutive, preterm newborns (GA at delivery: 29 [23-34 ] weeks) born to mothers who had a clinically indicated amniocentesis to rule out infection. Early-onset neonatal sepsis (EONS) was diagnosed using symptoms, hematological criteria and blood cultures.

RESULTS

IVH was diagnosed by cranial ultrasounds. The prevalence of IVH in our population was 25% (29/116). There was a direct relationship between cord blood EPO and cord blood IL-6 concentration (r = 0.225, p = 0.014), independent of GA at birth. Elevated cord blood EPO levels (r = 0.182, p = 0.016) and GA at birth (r =  -0.236, p = 0.004) remained significant independent factors associated with the risk of IVH, when evaluated with stepwise logistic regression analyses. Cord blood IL-6, pH, and EONS were not associated with IVH. These relationships remained following correction for GA at birth (p = 0.027).

CONCLUSIONS

Our results suggest that elevation in cord blood EPO may predict newborns at risk for IVH, independent of fetal inflammatory status. Further studies are warranted to confirm this association.

Cesarean scar ectopic pregnancy: case series and review of the literature

Cesarean scar ectopic pregnancy is becoming increasingly common at tertiary care hospitals around the world. It is a condition in which the embryo implants within the myometrium at the site of a previous cesarean hysterotomy, and it can occur in women with only one prior cesarean delivery. We present four cases of cesarean scar ectopic pregnancy diagnosed within a 6-month period between 2007 and 2008. Their initial presentations and management are discussed, followed by a review of the published literature summarizing both diagnostic and management recommendations.

Congenital heart defects in twin gestations

As ultrasound technology advances, diagnosis of fetal malformations, particularly congenital heart defects (CHD) is becoming standard practice. Currently, a key element of obstetrical care is the use of ultrasound to diagnose chorionicity in multiple gestations. Given the difference in incidence and types of complications between dichorionic and monochorionic pregnancies, early diagnosis of chorionicity is critical to determine the type of care and counseling a patient receives throughout the pregnancy. Early diagnosis of chorionicity allows investigators to more accurately determine the risk of CHD in monochorionic pregnancies. It has been long known that twin gestations incur a higher risk of congenital malformations, including CHD. However, it was not until recently that the incidence could be determined according to chorionicity. Previous studies looking at risk of malformations including CHD used the like-sex technique as a proxy for chorionicity, thereby overestimating the prevalence of monochorionic twins because roughly two-thirds of all twin gestations (including dichorionic) are the same sex. The rate of multiple gestations is increasing in the developed world. Assisted reproductive technology (ART) is partly responsible for the increased incidence of multiples. While many of the ART conceived pregnancies are dichorionic multiples, there is evidence that ART increases the risk of monochorionic multiple gestations. Presently, it is not technically feasible, nor practical, to screen all pregnancies with fetal echocardiography. Thus, many perinatal ultrasound centers screen women for risk factors that place them at higher risk for having a fetus with CHD. This higher risk' group then receives a fetal echocardiogram. The available literature regarding risk of CHD in monochorionic multiple gestations strongly points to a significant increase over the general population risk of 0.5-0.8%. Fetal echocardiography is technically feasible in twin pregnancies and increasingly available. Monochorionic multiple gestations should be screened with fetal echocardiography.

Independent activation of MAP kinase and MPF during the initiation of meiotic maturation in pig oocytes

Mitogen-activated protein (MAP) kinase is universally activated during oocyte maturation in all vertebrates studied to date. Its role in the resumption of meiosis and in the activation of maturation-promoting factor (MPF) remains unclear, especially in domestic species such as the pig. This study aimed to clarify the temporal and causal relationships between MAP kinase and MPF during meiotic maturation, particularly during the resumption of meiosis. Pig oocytes were matured synchronously in culture by treatment with cycloheximide. Kinase activities were analysed using a sensitive in vitro double-kinase assay and the specific MAP kinase pathway inhibitor U0126. MAP kinase and MPF were activated simultaneously at the time of germinal vesicle breakdown (GVBD; 6 h after removal of cycloheximide); they reached significant activity at 7 h (P < 0.05). The activities increased in parallel during GVBD (6-10 h) and peaked when the oocytes entered metaphase I (MI; 10 h). Whereas MAP kinase remained stable at peak activity thereafter, MPF activity significantly declined during the MI-MII transition (16-20 h) but increased to a second peak at MII (22 h). MAP kinase activity in denuded and cumulus-cell enclosed oocytes was completely inhibited by 20 and 80 mmicro mol U0126 l(-1), respectively. Oocytes without detectable MAP kinase activity underwent normal GVBD in terms of nuclear morphology and timing, although later meiotic stages were abnormal. The kinetics of MPF activity during GVBD were unaffected by U0126. This study has demonstrated that MAP kinase is activated simultaneously with MPF at GVBD, but that its activation is not essential for the activation of MPF nor for the resumption of the first meiosis in pig oocytes.

Nuclear transfer in practice

The technique of nuclear transfer (NT) allows the production of embryos, fetuses, and offspring from a range of embryonic, fetal, and adult derived cell types in a range of species. Successful development is dependent upon numerous factors, including type of recipient cell, source of recipient cell, method of reconstruction, activation, embryo culture, donor cell type, and donor and recipient cell cycle stages. The present review will discuss the uses of NT, the techniques presently available, and the factors affecting subsequent development.

Cloned pigs produced by nuclear transfer from adult somatic cells

Since the first report of live mammals produced by nuclear transfer from a cultured differentiated cell population in 1995 (ref. 1), successful development has been obtained in sheep, cattle, mice and goats using a variety of somatic cell types as nuclear donors. The methodology used for embryo reconstruction in each of these species is essentially similar: diploid donor nuclei have been transplanted into enucleated MII oocytes that are activated on, or after transfer. In sheep and goat pre-activated oocytes have also proved successful as cytoplast recipients. The reconstructed embryos are then cultured and selected embryos transferred to surrogate recipients for development to term. In pigs, nuclear transfer has been significantly less successful; a single piglet was reported after transfer of a blastomere nucleus from a four-cell embryo to an enucleated oocyte; however, no live offspring were obtained in studies using somatic cells such as diploid or mitotic fetal fibroblasts as nuclear donors. The development of embryos reconstructed by nuclear transfer is dependent upon a range of factors. Here we investigate some of these factors and report the successful production of cloned piglets from a cultured adult somatic cell population using a new nuclear transfer procedure.

Production of gene-targeted sheep by nuclear transfer from cultured somatic cells

It is over a decade since the first demonstration that mouse embryonic stem cells could be used to transfer a predetermined genetic modification to a whole animal. The extension of this technique to other mammalian species, particularly livestock, might bring numerous biomedical benefits, for example, ablation of xenoreactive transplantation antigens, inactivation of genes responsible for neuropathogenic disease and precise placement of transgenes designed to produce proteins for human therapy. Gene targeting has not yet been achieved in mammals other than mice, however, because functional embryonic stem cells have not been derived. Nuclear transfer from cultured somatic cells provides an alternative means of cell-mediated transgenesis. Here we describe efficient and reproducible gene targeting in fetal fibroblasts to place a therapeutic transgene at the ovine alpha1(I) procollagen (COL1A1) locus and the production of live sheep by nuclear transfer.

Nuclear transfer from somatic cells: applications in farm animal species

The reconstruction of mammalian embryos by transfer of a blastomere nucleus to an enucleated oocyte or zygote allows for the production of genetically identical individuals. This has advantages for research (that is, as biological controls) and commercial applications (that is, multiplication of genetically valuable livestock). However, the number of offspring that can be produced from a single embryo is limited both by the number of blastomeres (embryos at the 32-64-cell stage are the most widely used in farm animal species) and the limited efficiency of the nuclear transfer procedure. The ability to produce live offspring by nuclear transfer from cells that can be propagated and maintained in culture offers many advantages, including the production of many identical offspring over an extended period (since cultured cells can be frozen and stored indefinitely) and the ability to modify genetically or to select populations of cells of specific genotypes or phenotypes before embryo reconstruction. This objective has been achieved with the production of lambs using nuclei from cultured cells established from embryonic, fetal and adult material. In addition, lambs transgenic for human factor IX have been produced from fetal fibroblasts transfected and selected in culture.

Production of live calves derived from embryonic stem-like cells aggregated with tetraploid embryos

To date, cloned farm animals have been produced by nuclear transfer from embryonic, fetal, and adult cell types. However, mice completely derived from embryonic stem (ES) cells have been produced by aggregation with tetraploid embryos. The objective of the present study was to generate offspring completely derived from bovine ES-like cells. ES-like cells isolated from the inner cell mass of in vitro-produced embryos were aggregated with tetraploid bovine embryos generated by electrofusion at the 2-cell stage. A total of 77 embryo aggregates produced by coculture of two 8-cell-stage tetraploid embryos and a clump of ES-like cells were cultured in vitro. Twenty-eight of the aggregates developed to the blastocyst stage, and 12 of these were transferred to recipient cows. Six calves representing 2 singletons and 2 sets of twins were produced from the transfer of the chimeric embryos. Microsatellite analysis for the 6 calves demonstrated that one calf was chimeric in the hair roots and the another was chimeric in the liver. However, unfortunately, both of these calves died shortly after birth. Two of the placentae from the remaining pregnancies were also chimeric. These results indicate that the bovine ES-like cells used in these studies were able to contribute to development.

New advances in somatic cell nuclear transfer: application in transgenesis

The ability to produce live offspring by nuclear transfer from cultured somatic cells provides a route for the precise genetic manipulation of large animal species. Such modifications include the addition, or "knock-in", and the removal or inactivation, "knock-out", of genes or their control sequences. This paper will review some of the factors which affect the development of embryos produced by nuclear transfer, the advantages of using cultured cells as donors of genetic material, and methods that have been developed to enrich gene targeting frequency. Commercial applications of this technology in biomedicine and agriculture will also be addressed.

Embryonic and somatic cell cloning

Revolutionary opportunities in biology, medicine and agriculture arise from the observation that offspring are obtained after nuclear transfer if somatic donor cells are induced to become quiescent. Exploitation of many of these opportunities will depend upon optimizing procedures for nuclear transfer. This may come about through an understanding of the means by which factors in the oocyte cytoplasm act upon the DNA of the transferred nucleus to regulate gene expression. Similarly, research will extend the procedure to other species. This technology may be used for embryo production, the introduction of genetic change and the derivation of cells needed to treat human diseases. Groups of genetically identical animals will be used in research to control genetic variation and to allow transfer of cells between individuals. In agriculture, production of a small number of clones will separate genetic and environmental effects, whereas production of larger numbers of offspring will disseminate genetic improvement from nucleus herds. Precise genetic modification will be achieved by site specific recombination in the donor cells before nuclear transfer. In all mammals it will become possible to define the role of any gene product and to analyse the mechanisms that regulate gene expression. Medical uses of these techniques will include the production of proteins needed to treat disease and the supply of organs such as hearts, livers and kidneys from pigs. As genome mapping projects identify loci associated with traits of commercial importance in agriculture then gene targeting will be used to study this effect. Finally, cells capable of differentiation into any of the tissues of a patient will provide treatment for diseases reflecting damage to a specific cell population that neither repairs nor replaces itself.

Nuclear transfer in farm animal species

CLONE 'a group of two or more individuals with identical genetic makeup derived, by asexual reproduction, from a single common parent or ancestor' (The Chambers Dictionary 1993, Chambers Harrap). The term clone was originally applied to plants but has subsequently been used in a much broader context to include a person or thing closely similar to another, a copy or replica. In animals, true clones, as defined above, may be produced by embryo splitting or blastomere separation either artificially, or as occurs naturally in the production of identical twins. In these individuals all of the components making up the individual, including nuclear genetic material (the genome) and other maternally derived factors are derived from a single unique embryo which is the result of sexual reproduction. The term clone has been applied to animals produced by the technique of nuclear transfer. In this asexual process, nuclear genetic material is transferred from a donor cell (karyoplast) into a recipient cell (cytoplast) from which the genetic material has been removed. In farm animals the cytoplast of choice is the matured oocyte (or unfertilised egg) thus the animals developing from this technique are not true clones as each cytoplast is often derived from a different animal. The resultant animals may therefore be more aptly described as 'genomic copies'. In mammals, successful development of embryos reconstructed by nuclear transfer was originally restricted to using early embryos as nuclear donors, however, recent progress has demonstrated successful development using nuclei from embryonic, foetal and adult derived cell populations. Numerous factors affect the development of embryos reconstructed by nuclear transfer including; the cell cycle stage of the recipient cell, the cell cycle stage of the donor nucleus, the differentiated state of the donor nucleus, activation of the recipient cell, the culture method. In addition, there are variations in success between species, these may be related to differences in organisation of the cytoskeleton and/or the meiotic spindle in the recipient cell,differences in cell cycle control during early development, the onset of zygotic transcription or differences in the metabolic requirements of early embryos in vitro. The aim of this article is to describe and discuss some of these factors in relation to the successful development of nuclear transfer reconstructed embryos and in particular to the 'reprogramming' or 'remodeling' of the donor genetic material to attain successful development.

Nuclear Equivalence, Nuclear Transfer, and the Cell Cycle

The last 20 years have seen the development of techniques for the production of mammals by nuclear transfer. Originally limited to the swapping of pronuclei and the use of early cleavage-stage embryos as nuclear donors, nuclear transfer came of age in 1995 with the birth of 2 Welsh Mountain lambs, Megan and Morag, that were produced using cultured differentiated cells as donors of genetic material. In 1996, Dolly was the first animal to be produced using the genetic material from an adult-derived somatic cell. The techniques used in the production of these animals have now been reproduced in both sheep and cattle, and as predicted, successful development has been obtained using donor cells taken directly ex vivo. This article reviews the current status of mammalian nuclear transfer and the biological background to these successes.

Maintenance of bovine oocytes in meiotic arrest and subsequent development In vitro: A comparative evaluation of antral follicle culture with other methods

The frequency of development of bovine embryos produced by maturation, fertilization, and culture in vitro is lower than that observed in vivo. One factor that may affect both the frequency of development and the quality of the embryos produced is the developmental competence of the oocyte. In current in vitro production systems, oocyte maturation, characterized by the resumption of meiosis, occurs after oocyte aspiration from the follicle. The developmental competence of individual oocytes may be improved by inducing maturation after culturing under conditions that inhibit the resumption of meiosis. In order to test this hypothesis, a system has been established in which intact antral follicles (3-8 mm in diameter) are cultured in vitro. During this period the oocytes are maintained at the germinal vesicle (GV) stage under the inhibitory effects of the follicle. Culture of intact antral follicles was compared with two other "physiological" methods for the maintenance of GV arrest: oocytes were cultured attached to a small part of the follicle wall or within hemisections of follicles. It was found that 96.8% of oocytes recovered from intact antral follicles-as compared to 24.6% attached to a small part of the follicle wall and 62.7% within hemisections of follicles-were maintained at the GV stage after 24-h culture. The effects on GV arrest and subsequent maturation of the oocytes were evaluated after longer periods of antral follicle culture (2, 4, and 7 days). As the culture period increased, the number of GV-arrested oocytes decreased; the maximum percentage of GV arrest was observed after 24-h culture. The majority of these oocytes matured to metaphase II. A comparison of blastocyst production was made after fertilization and subsequent development of oocytes obtained following follicle culture and of control oocytes aspirated directly from antral follicles. The cleavage rate and percentage of blastocyst production in these two groups were 54.6 +/- 13.9%, 48.4 +/- 8.4% and 68.6 +/- 8.6%, 32.8 +/- 10.8%, respectively. Statistical analysis showed significant differences in both cleavage rate and blastocyst production between these two groups. Total cell numbers in the control group were 144.6 +/- 7.28 and 152.0 +/- 25.8 after follicle culture. It is concluded that culture of intact antral follicles for 24 h is an alternative method for the maintenance of bovine oocytes in meiotic arrest and that these oocytes acquire a greater developmental competence in vitro.

Human factor IX transgenic sheep produced by transfer of nuclei from transfected fetal fibroblasts

Ovine primary fetal fibroblasts were cotransfected with a neomycin resistance marker gene (neo) and a human coagulation factor IX genomic construct designed for expression of the encoded protein in sheep milk. Two cloned transfectants and a population of neomycin (G418)-resistant cells were used as donors for nuclear transfer to enucleated oocytes. Six transgenic lambs were liveborn: Three produced from cloned cells contained factor IX and neo transgenes, whereas three produced from the uncloned population contained the marker gene only. Somatic cells can therefore be subjected to genetic manipulation in vitro and produce viable animals by nuclear transfer. Production of transgenic sheep by nuclear transfer requires fewer than half the animals needed for pronuclear microinjection.

Viable offspring derived from fetal and adult mammalian cells

Fertilization of mammalian eggs is followed by successive cell divisions and progressive differentiation, first into the early embryo and subsequently into all of the cell types that make up the adult animal. Transfer of a single nucleus at a specific stage of development, to an enucleated unfertilized egg, provided an opportunity to investigate whether cellular differentiation to that stage involved irreversible genetic modification. The first offspring to develop from a differentiated cell were born after nuclear transfer from an embryo-derived cell line that had been induced to become quiescent. Using the same procedure, we now report the birth of live lambs from three new cell populations established from adult mammary gland, fetus and embryo. The fact that a lamb was derived from an adult cell confirms that differentiation of that cell did not involve the irreversible modification of genetic material required for development to term. The birth of lambs from differentiated fetal and adult cells also reinforces previous speculation that by inducing donor cells to become quiescent it will be possible to obtain normal development from a wide variety of differentiated cells.

Sheep cloned by nuclear transfer from a cultured cell line

Nuclear transfer has been used in mammals as both a valuable tool in embryological studies and as a method for the multiplication of 'elite' embryos. Offspring have only been reported when early embryos, or embryo-derived cells during primary culture, were used as nuclear donors. Here we provide the first report, to our knowledge, of live mammalian offspring following nuclear transfer from an established cell line. Lambs were born after cells derived from sheep embryos, which had been cultured for 6 to 13 passages, were induced to quiesce by serum starvation before transfer of their nuclei into enucleated oocytes. Induction of quiescence in the donor cells may modify the donor chromatin structure to help nuclear reprogramming and allow development. This approach will provide the same powerful opportunities for analysis and modification of gene function in livestock species that are available in the mouse through the use of embryonic stem cells.

Cell cycle co-ordination in embryo cloning by nuclear transfer

Exciting new opportunities in embryo cloning have been made possible by recent studies on the interaction of the donor nucleus with the recipient cytoplasm after embryo reconstruction. This article reviews information regarding the co-ordination of nuclear and cytoplasmic events during embryo reconstruction, in particular the direct and indirect effects of maturation/ meiosis/mitosis-promoting factor (MPF), upon the transferred nucleus. This will be discussed in relation to DNA replication, the maintenance of correct ploidy, the occurrence of chromosomal abnormalities and development of reconstructed embryos. Although this review is primarily concerned with the reconstruction of mammalian embryos, specific examples from amphibians will also be cited.

Isolation and characterization of permanent cell lines from inner cell mass cells of bovine blastocysts

Inner cell masses (ICM) from in vitro produced day 8 or 9 bovine blastocysts were isolated by immunosurgery and cultured under different conditions in order to establish which of two feeder cell types and culture media were most efficient in supporting attachment and outgrowth of the bovine ICM cells. The efficiency of attachment and outgrowth of the ICM cells could be markedly improved when STO feeder cells were used instead of bovine uterus epithelial cells, and by using charcoal-stripped serum instead of normal serum to supplement the culture medium. More than 20 stable cell lines were obtained. Some of these lines were examined by immunofluorescence for developmentally regulated markers. From these results we conclude that the cell lines resemble epithelial cells, rather than pluripotent ICM cells. The developmental potential of cells of one of the lines was tested in the nuclear transfer assay. The cell line could support the initial development of enucleated oocytes, but none of the reconstructed embryos passed the eight-cell block.

Transfer of nuclei from 8-cell stage mouse embryos following use of nocodazole to control the cell cycle

Mouse 2-, 4-, 8-, and 16-cell embryos were exposed to nocodazole in M16 culture medium. The effect of different concentrations and exposure times on the efficiency of cell cycle synchronization and the development of the treated embryos after release from the drug was determined. The minimum effective concentration (> 95% of arrested nuclei) for 4-, 8-, and 16-cell embryos was 5 microM nocodazole. The effect upon subsequent development of mouse embryos depended upon both the stage of development of the embryo at treatment (P < 0.001) and the length of exposure to nocodazole (P < 0.001). Exposure to any concentration of nocodazole within the range 2.5-10 microM for 12 hr caused a reduction in the proportion of embryos that formed blastocysts. As the period of exposure to 5 microM nocodazole increased from 12 to 24 hr, the proportion of embryos developing to the blastocyst stage decreased. The lower proportion of embryos developing to the blastocyst stage and to term (P < 0.01) suggests that the more advanced stages were more susceptible to damage as a result of exposure to nocodazole. The rate of development of 4-cell embryos to blastocysts was not affected when an exposure time of 9 hr was used. Together these results show that it is possible to use nocodazole to arrest mouse embryonic cells in mitosis but that it is not appropriate to culture the embryos in the presence of this drug for prolonged periods. Individual blastomeres completed mitosis at 60-90 min and started DNA synthesis at 120-150 min after release from nocodazole.(ABSTRACT TRUNCATED AT 250 WORDS)