Ultrasonographic and histological characterization of the placenta of somatic nuclear transfer-derived pregnancies in dairy cattle

The impact of in vitro embryo production on placental and umbilical cord vascularization is minimized by the addition of reproductive fluids

Animals born from in-vitro-produced (IVP) embryos show changes in the placenta and umbilical cord vascularization. This study compares the placental and umbilical vascular morphometry in pigs (n = 19) born through artificial insemination (AI group) or after transfer of IVP embryos cultured with (RF-IVP group) or without (C-IVP group) reproductive fluids. The relationship between vascular parameters and animal growth during the first year of life was also analyzed. Samples were collected at birth, fixed, paraffin-embedded, cut in sections, stained, and photographed for vascular and morphometric analysis with ImageJ® and Slide Viewer®. The average daily weight gain was individually scored from birth to the first year of life. No differences were found in placental vascular morphometry among groups, except for the vascular area of small vessels (arterioles, venules, and small vessels) that was higher in the C-IVP group. Regarding the umbilical cord, the values for perimeter (AI: 26.40 ± 3.93 mm; IVP: 30.51 ± 4.74 mm), diameter (AI: 8.35 ± 1.01 mm; IVP: 10.26 ± 1.85 mm), area (AI: 43.18 ± 12.87; IVP: 56.61 ± 14.89 mm2), and Wharton's jelly area (AI: 36.86 ± 12.04 mm2; IVP 48.88 ± 12.80 mm2) were higher in IVP-derived than AI-derived animals, whereas arterial and venous morphometric data were similar between groups. A correlation study showed that placental and umbilical cord vascular phenotypes affect the further growth of pigs. In conclusion, assisted reproductive technologies impact small caliber vessels in the placenta and morphometric parameters in the umbilical cord. The addition of reproductive fluids in IVP-embryo contributes to reduce the differences with in vivo-derived animals.

Blastocyst Cell Number and Allocation Affect the Developmental Potential and Transcriptome of Bovine Somatic Cell Nuclear Transfer Embryos

Cloning cattle using somatic cell nuclear transfer (SCNT) is inefficient. Although the rate of development of SCNT embryos in vitro is similar to that of fertilized embryos, most fail to develop into healthy calves. In this study, we aimed to identify developmentally competent embryos according to blastocyst cell composition and perform transcriptome analysis of single embryos. Transgenic SCNT embryos expressing nuclear-localized HcRed gene at day 7 of development were imaged by confocal microscopy for cell counting and individually transferred to recipient heifers. Pregnancy rates were determined by ultrasonography. Embryos capable of establishing pregnancy by day 35 had an average of 117 ± 6 total cells, whereas embryos with an average of 128 ± 5 cells did not establish pregnancy (P < 0.05). A lesser average number of 41 ± 3 cells in the inner cell mass (ICM) also resulted in pregnancies (<0.05) than a greater number of 48 ± 2 cells in the ICM. Single embryos were then subjected to RNA sequencing for transcriptome analysis. Using weighted gene coexpression network analysis, we identified clusters of genes in which gene expression correlated with the number of total cells or ICM cells. Gene ontology analysis of these clusters revealed enriched biological processes in coenzyme metabolic process, intracellular signaling cascade, and glucose catabolic process, among others. We concluded that SCNT embryos with fewer total and ICM cell numbers resulted in greater pregnancy establishment rates and that these differences are reflected in the transcriptome of such embryos.

Ultrasonographic measurements in first trimester concepti identify predictors of birth weight and postnatal development in cattle

The placenta is a major driver of prenatal growth and involved in programming of postnatal performance. We therefore determined placental and embryo-fetal ultrasonographic parameters in early pregnancy and their relationships with birth weight and postnatal weights in a Bos indicus-Bos taurus composite beef cattle population. Pregnancies were generated in 2-yr-old Droughtmaster heifers by artificial insemination after estrus synchronization in 2 consecutive years (2009, n = 36 and 2010, n = 57), with a subset of 2010 heifers used again as lactating 3-yr-old cows in 2011 (n = 24). Each cohort was managed as 1 contemporary group for measurements of Corpus luteum diameter, amnion length and width, placentome width and thickness, and embryo-fetal crown-rump length, at 7 and 8 wk of gestation. This was followed by recordings of birth weight, branding weight at 5 to 6 mo of age and weaning weight 2 mo later. At a significance threshold of P < 0.05, placentome thickness at week 7 was negatively correlated with weights at birth (r = -0.23), branding (r = -0.25), and weaning (r = -0.35), whereas placentome width at week 7 (r = 0.24) and thickness at week 8 (r = 0.29) were positively correlated with birth weight. Thicker placentomes in males at week 7 (7%) difference mirrored sex differences in weights at birth (7%), branding (10%), and weaning (6%). The sex difference trend for birth weight was not consistent across sire-year combinations, ranging from -3.2 to +4.7 kg (birth weight of males - females per sire). These results support the hypothesis that placental parameters at the transition from embryo to fetal stage are major predictors of fetal and postnatal growth, albeit with significant environmentally induced plasticity, in stabilized B. indicus-B. taurus composite populations, and suggest that elements of B. indicus-B. taurus reciprocal differences in birth weight persist in composite populations.

Placental abnormalities in equine pregnancies generated by SCNT from one donor horse

Placental changes associated with SCNT have been described in several species, but little information is available in this area in the horse. We evaluated the ultrasonographic, gross, and histopathological characteristics of placentas from three successful and five unsuccessful equine SCNT pregnancies, established using cells from a single donor horse. Starting at approximately 6-month gestation, the pregnancies were monitored periodically using transrectal (TR) and transabdominal (TA) ultrasonography (US) to examine the placentas, fetal fluids, and fetuses. Of the five mares that aborted, one mare did so suddenly without any abnormal signs detected by US and four had enlarged umbilical vessels visible on TA-US before abortion. Placental edema (TR-US) and intravascular thrombi in the umbilical cords were seen (TA-US) in two of these four mares; one mare aborted shortly after acute placental separation was identified on TA-US. In three mares that delivered live foals, TA-US showed engorged allantoic vessels and enlarged umbilical vessels. Two of these mares had placental thickening visible on TR-US, interpreted as a sign of placentitis, that subsided after aggressive medical treatment. Seven of the eight placentas were submitted for gross and histopathological examinations after delivery. All placentas had some degree of edema, abnormally engorged allantoic vessels, and enlarged umbilical vessels. Placentitis, large allantoic vesicles, cystic pouches in the fetal part of the cord, and hemorrhages and thrombi in the umbilical vessels were detected only in placentas from mares that aborted. Equine pregnancies resulting from SCNT may be associated with placental pathologies that can be detected using ultrasonography. However, interpreting their severity is difficult. Although placental abnormalities have been observed in SCNT pregnancies in other species, to the best of our knowledge, placentitis has not been previously reported and may be an important complication of equine SCNT pregnancies, leading to pregnancy loss.

Neonatal Care and Management of Foals Derived by Somatic Cell Nuclear Transfer

There are few reports on the birth of foals resulting from equine adult somatic cell nuclear transfer (NT). On evaluation of reports of 28 live-born adult somatic-cell NT (clone) foals, 3 died within 2 weeks of birth of complications. Approximately 50 % of all reported cloned foals had complications, some requiring aggressive supportive care. The most common abnormalities reported were neonatal maladjustment syndrome, enlarged umbilical remnant, and angular deformity of the forelimbs, similar to problems described in cloned cattle. In contrast, large offspring syndrome and gross abnormalities of the fetal membranes which are described in cloned cattle are not reported in cloned foals. Reports of the health of foals produced by nuclear transfer suggest that NT foals should be treated aggressively as at-risk foals until all parameters are normal.

Ultrasonographic fetal parameters and neonatal survival in somatic cell nuclear transfer-derived beef calves

The objectives of this study were to identify prognostic indicators of calf survival in SCNT-derived beef calves. Ultrasonographic parameters of fetal well-being and development, maternal clinical parameters, and neonatal parameters were evaluated as predictors of calf survival in cows carrying SCNT-derived beef fetuses (n = 38). Calf survival was 61.5% (88.2% female and 40.9% male calves; P = 0.0026). Cow respiratory rate and cow temperature were significantly greater in the nonsurviving (NS) group 1 week prepartum. In surviving (S) calves, fetal heart rate (FHR) decreased during the last 2 weeks of gestation (P < 0.01). However, this final deceleration was not observed in NS calves, resulting in higher FHRs in this group (P < 0.0001). Fetal movement and fluid scores did not differ with calf classification. Mean amniotic fluid depth was smaller in S (5.5 ± 0.7 cm) than NS (8.7 ± 1.4 cm) calves (P = 0.0398). However, mean allantoic fluid depth did not differ (P = 0.6120). There was a significant association between the body weight of calf and the diameter of the fetal aorta (P = 0.0115; r(2) = 0.3762). Surviving calves were lighter at birth (P = 0.0028) and were born later (P = 0.007) than NS calves. Calves born vaginally had a smaller fetal aorta (2.1 ± 0.1 cm vaginal and 2.4 ± 0.1 cm Cesarean) (P = 0.0487) and a lighter birth weight (41.4 ± 4.2 kg vaginal and 60.4 ± 2.1 kg Cesarean) (P = 0.0001) than calves born by Cesarean. Also, calves that underwent spontaneous labor (52.2% S and 0% NS; P = 0.0029) had a lighter birth weight (44.9 ± 3.8 kg) than calves that did not initiate labor (61.6 ± 2.2 kg) (P = 0.0004). Frequent ultrasonographic fetal monitoring allowed identification of differences between S and NS calves. Calves without a final decrease in FHR or with a large aortic diameter were more likely to require a Cesarean because of failure to initiate labor or fetomaternal disproportion. Parameters of fetal well-being and development during the last 3 weeks of gestation were first described in SCNT-derived beef calves.

Incidence of abnormal offspring from cloning and other assisted reproductive technologies

In animals produced by assisted reproductive technologies, two abnormal phenotypes have been characterized. Large offspring syndrome (LOS) occurs in offspring derived from in vitro cultured embryos, and the abnormal clone phenotype includes placental and fetal changes. LOS is readily apparent in ruminants, where a large calf or lamb derived from in vitro embryo production or cloning may weigh up to twice the expected body weight. The incidence of LOS varies widely between species. When similar embryo culture conditions are applied to nonruminant species, LOS either is not as dramatic or may even be unapparent. Coculture with serum and somatic cells was identified in the 1990s as a risk factor for abnormal development of ruminant pregnancies. Animals cloned from somatic cells may display a combination of fetal and placental abnormalities that are manifested at different stages of pregnancy and postnatally. In highly interventional technologies, such as nuclear transfer (cloning), the incidence of abnormal offspring continues to be a limiting factor to broader application of the technique. This review details the breadth of phenotypes found in nonviable pregnancies, together with the phenotypes of animals that survive the transition to extrauterine life. The focus is on animals produced using in vitro embryo culture and nuclear transfer in comparison to naturally occurring phenotypes.

Effect of calf death loss on cloned cattle herd derived from somatic cell nuclear transfer: clones with congenital defects would be removed by the death loss

To increase public understanding on cloned cattle derived from somatic cell nuclear transfer (SCNT), the present review describes the effect of calf death loss on an SCNT cattle herd. The incidence of death loss in SCNT cattle surviving more than 200 days reached the same level as that in conventionally bred cattle. This process could be considered as removal of SCNT cattle with congenital defects caused by calf death loss. As a result of comparative studies of SCNT cattle and conventionally bred cattle, the substantial equivalences in animal health status, milk and meat productive performance have been confirmed. Both sexes of SCNT cattle surviving to adulthood were fertile and their reproductive performance, including efficiency of progeny production, was the same as that in conventionally bred cattle. The presence of substantial equivalence between their progeny and conventionally bred cattle also existed. Despite these scientific findings, the commercial use of food products derived from SCNT cattle and their progeny has not been allowed by governments for reasons including the lack of public acceptance of these products and the low efficiency of animal SCNT. To overcome this situation, communication of the low risk of SCNT technology and research to improve SCNT efficiency are required.

Developmental and epigenetic anomalies in cloned cattle

Many of the developmental anomalies observed in cloned animals are related to foetal and placental overgrowth, a phenomenon known as the 'large offspring syndrome' (LOS) in ruminants. It has been hypothesized that the epigenetic control of imprinted genes, that is, genes that are expressed in a parental-specific manner, is at the root of LOS. Our recent research has focused on understanding epigenetic alterations to imprinted genes that are associated with assisted reproductive technologies (ART), such as early embryo in vitro culture (IVC) and somatic cell nuclear transfer (SCNT) in cattle. We have sought and identified single nucleotide polymorphisms in Bos indicus DNA useful for the analysis of parental-specific alleles and their respective transcripts in tissues from hybrid embryos derived by crossing Bos indicus and Bos taurus cattle. By analysing differentially methylated regions (DMRs) of imprinted genes SNRPN, H19 and the IGF2R in cattle, we demonstrated that there is a generalized hypomethylation of the imprinted allele and the biallelic expression of embryos produced by SCNT when compared to the methylation patterns observed in vivo (artificially inseminated). Together, these results indicate that imprinting marks are erased during the reprogramming of the somatic cell nucleus during early development, indicating that such epigenetic anomalies may play a key role in mortality and morbidity of cloned animals.

Aberrant expression of E-cadherin and β-catenin proteins in placenta of bovine embryos derived from somatic cell nuclear transfer

Abnormal placental development is common in the bovine somatic cell nuclear transfer (SCNT)-derived fetus. In the present study, we characterised the expression of E-cadherin and β-catenin, structural proteins of adherens junctions, in SCNT gestations as a model for impaired placentation. Cotyledonary tissues were separated from pregnant uteri of SCNT (n = 6) and control pregnancies (n = 8) obtained by artificial insemination. Samples were analysed by western blot, quantitative RT-PCR (qRT-PCR) and immunohistochemistry. Bovine trophectoderm cell lines derived from SCNT and control embryos were analysed to compare with the in utero condition. Although no differences in E-cadherin or β-catenin mRNA abundance were observed in fetal tissues between the two groups, proteins encoded by these genes were markedly under-expressed in SCNT trophoblast cells. Immunohistochemistry revealed a different pattern of E-cadherin and total β-catenin localisation in SCNT placentas compared with controls. No difference was observed in subcellular localisation of dephosphorylated active-β-catenin protein in SCNT tissues compared with controls. However, qRT-PCR confirmed that the wingless (WNT)/β-catenin signalling pathway target genes CCND1, CLDN1 and MSX1 were downregulated in SCNT placentas. No differences were detected between two groups of bovine trophectoderm cell lines. Our results suggest that impaired expression of E-cadherin and β-catenin proteins, along with defective β-catenin signalling during embryo attachment, specifically during placentation, is a molecular mechanism explaining insufficient placentation in the bovine SCNT-derived fetus.

Environmental regulation of placental phenotype: implications for fetal growth

Environmental conditions during pregnancy determine birthweight, neonatal viability and adult phenotype in human and other animals. In part, these effects may be mediated by the placenta, the principal source of nutrients for fetal development. However, little is known about the environmental regulation of placental phenotype. Generally, placental weight is reduced during suboptimal conditions like maternal malnutrition or hypoxaemia but compensatory adaptations can occur in placental nutrient transport capacity to help maintain fetal growth. In vivo studies show that transplacental glucose and amino acid transfer adapt to the prevailing conditions induced by manipulating maternal calorie intake, dietary composition and hormone exposure. These adaptations are due to changes in placental morphology, metabolism and/or abundance of specific nutrient transporters. This review examines environmental programming of placental phenotype with particular emphasis on placental nutrient transport capacity and its implications for fetal growth, mainly in rodents. It also considers the systemic, cellular and molecular mechanisms involved in signalling environmental cues to the placenta. Ultimately, the ability of the placenta to balance the competing interests of mother and fetus in resource allocation may determine not only the success of pregnancy in producing viable neonates but also the long-term health of the offspring.

Morphometric analysis of yak placentomes during gestation

To study the morphological characteristics of placentomes during gestation, thirty-one yaks were used to determine anatomical and histological data of placentomes by morphometric method. The results showed that there were no significant changes in the total number of yak placentomes during gestation, but remarkably fewer placentomes in the non-pregnant horn compared with the pregnant horn. The mean size of placentomes increased significantly from <61 days to 181-210 days and decreased in 211+ days. The development of placentomes in the pregnant horn were obviously different from that of the non-pregnant horn except <61 days, which were longer, wider, and thicker. The volume density of fetal villi increased during gestation, with a concomitant reduction in the volume density of caruncular endometrium. However, there was no significant change in the surface density of fetal villi. The volume density of binucleate cell increased in prophase and then decreased. No apparent changes in the volume densities of maternal and fetal pyknotic cell occurred throughout gestation. There was a significant increase in the average total volume of yak placentomes from 61-90 days to 181-210 days and a significant decrease in 211+ days. The same patterns were showed in the average total volumes of caruncular endometrium and binucleate cell as well as the mean total surface area of fetal villi. However, the mean total volumes of fetal villi, maternal and fetal pyknotic cell increased constantly with increasing gestation time. Three types of placentome shape were identified in yak. The results showed that the maternal-fetal contact area of yak was enlarged by increasing the placentome size as well as the total volume and surface area of placentome component during pregnancy, so placental function could be enhanced further to meet the needs of fetal development.

Physical and clinicopathologic findings in foals derived by use of somatic cell nuclear transfer: 14 cases (2004-2008)

OBJECTIVE

To describe the health status of foals derived by use of somatic cell nuclear transfer (NT) at a university laboratory.

DESIGN

Retrospective case series.

ANIMALS

14 live-born NT-derived foals.

PROCEDURES

Medical records from 2004 through 2008 were evaluated to identify all pregnancies resulting in live-born NT-derived foals. Information obtained included gestation length, birth weight, foaling complications, gross abnormalities of the fetal membranes, appearance of the umbilicus, mentation of the foal, limb deformities, and any other abnormalities detected in the neonatal period. Clinicopathologic data were also evaluated when available. Records of 4 recipient mares during gestation were included.

RESULTS

Six foals were clinically normal for all evaluated variables. The most common abnormalities detected in the remaining 8 foals included maladjustment, enlarged umbilical remnant, and angular deformity of the forelimbs. Two foals died within 7 days after parturition; in the remaining foals, these conditions all resolved with medical or surgical management. Large offspring syndrome and gross abnormalities of the fetal membranes were not detected. The 12 surviving foals remained healthy.

CONCLUSIONS AND CLINICAL RELEVANCE

Associated problems of calves resulting from use of NT have been reported, but there are few data on the outcome of foals resulting from adult somatic cell NT in horses. Although this population of foals had a lower perinatal mortality rate than has been reported for NT-derived calves, some NT-derived foals required aggressive supportive care. Birth of foals derived from NT should take place at a center equipped to handle critical care of neonates.

Delivery of cloned offspring: experience in Zebu cattle (Bos indicus)

The production of a healthy cloned calf is dependent on a multitude of successful steps, including reprogramming mediated by the oocyte, the development of a functional placenta, adequate maternal–fetal interaction, the establishment of a physiological metabolic setting and the formation of a complete set of well-differentiated cells that will eventually result in well-characterised and fully competent tissues and organs. Although the efficiency of nuclear transfer has improved significantly since the first report of a somatic cell nuclear transfer-derived animal, there are many descriptions of anomalies concerning cloned calves leading to high perinatal morbidity and mortality. The present article discusses some our experience regarding perinatal and neonatal procedures for cloned Zebu cattle (B. indicus) that has led to improved survival rates in Nellore cloned calves following the application of such ‘labour-intensive technology’.

Evolução morfométrica dos anexos embrionários e fetais bovinos obtidos por monta natural, com 10 a 70 dias da gestação

O período inicial da gestação de bovinos é caracterizado por grandes perdas embrionárias. Considerando a importância deste fator no âmbito da reprodução animal foram estudados os anexos embrionários e fetais bovinos fecundados por monta natural de 15-70 dias de gestação, com o objetivo de estabelecer parâmetros morfométricos da placenta na fase inicial da gestação. Com uso de um paquímetro foram realizadas mensurações do comprimento (crânio caudal), largura (latero lateral) e altura (dorso ventral) das membranas corioalantóide e amniótica. O início da formação dos cotilédones foi observado e quantificado, assim como, o peso placentário. O peso médio do saco gestacional aumentou com o evoluir da idade gestacional, entretanto, o crescimento foi acelerado a partir de 20-30 dias de gestação. O comprimento crânio caudal e dorso ventral da membrana corioalantóide e do âmnio apresentaram crescimento lento e gradual com o evoluir dos períodos gestacionais analisados. Com 30-40 dias de gestação, os primeiro cotilédones já eram visualizados e contatos com facilidade na superfície coriônica. Os períodos de crescimento coincidiram com os maiores índices de perdas gestacionais em bovinos. Os parâmetros aqui analisados poderão servir para futuras investigações dos anexos embrionários de organismos manipulados em laboratório.

Initial development of bovine placentation (Bos indicus) from the point of view of the allantois and amnion

The aim of this study was to perform a morphological characterization of the initial bovine placental development, between 20 and 70 days post-insemination (p.i.), with emphasis on the differentiation of the allantois and amnion. After collection, the conceptuses were dissected, macroscopically measured and photographically documented. The extraembryonic membranes were cut into fragments measuring 5 cm(2), and then fixed in 4% paraformaldehyde for analysis using light microscopy, and in 2.5% glutaraldehyde for use in scanning and transmission electron microscopy. The extraembryonic and fetal membranes presented variable degrees of development throughout the periods analysed. The macroscopic appearance of vascularization of the allantois, its attempt to merge with the chorium and the effective appearance of the first cotyledons in development were the events observed from 30 to 40 days of pregnancy. The measurements of the amnion increased gradually as gestation developed. The allantoic epithelia presented cellular dimorphism from 20 to 25 days of pregnancy, but was shown to be immature from 60 to 70 days of pregnancy.