Nuclear transfer technologies: between successes and doubts

Eicosanoid pathway expression in bovine endometrial epithelial and stromal cells in response to lipopolysaccharide, interleukin 1 beta, and tumor necrosis factor alpha

During endometrial inflammation, bovine endometrium responds by increasing the production of pro-inflammatory mediators, such as interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNFα), and eicosanoids. The purpose of this study was to establish and characterize an in vitro model of endometrial inflammation using bovine endometrial epithelial (bEEL) and stromal (bCSC) cell lines. We evaluated the effects of the infectious agent (bacterial lipopolysaccharide; LPS) and pro-inflammatory mediators (IL-1β and TNFα) on eicosanoid biosynthesis pathway gene expression and production by bEEL and bCSC cells. Based on concentration-response experiments, the optimal concentrations for responses were 1 μg/mL LPS, 10 ng/mL IL-1β and 50 ng/mL TNFα. Real-time PCR results show that there was an upregulation of relative mRNA expression of PTGS2 when bEEL and bCSC were treated with LPS, IL-1β and TNFα. An increase in PTGES3 expression was observed when bEEL cells were treated with LPS and IL-1β and PTGES2 when treated with IL-1β. In bCSC cells, FAAH relative mRNA was decreased upon treatments. Rate of production of PGE₂, PGF_2α, PGE₂-EA and PGF_2α-EA were also determined using liquid chromatography tandem mass spectrometry. Our results show that eicosanoid production was increased in both cell lines in response to LPS, IL-1β, and TNFα. We suggest that the characteristics of bEEL and bCSC cell lines mimic the physiological responses found in mammals with endometrial infection, making them excellent in vitro models for intrauterine environment studies.

Can Reprogramming of Overall Epigenetic Memory and Specific Parental Genomic Imprinting Memory within Donor Cell-Inherited Nuclear Genome be a Major Hindrance for the Somatic Cell Cloning of Mammals? – A Review

Successful cloning of animals by somatic cell nuclear transfer (SCNT) requires epigenetic transcriptional reprogramming of the differentiated state of the donor cell nucleus to a totipotent embryonic ground state. It means that the donor nuclei must cease its own program of gene expression and restore a particular program of the embryonic genome expression regulation that is necessary for normal development. Transcriptional activity of somatic cell-derived nuclear genome during embryo pre- and postimplantation development as well as foetogenesis is correlated with the frequencies for spatial remodeling of chromatin architecture and reprogramming of cellular epigenetic memory. This former and this latter process include such covalent modifications as demethylation/re-methylation of DNA cytosine residues and acetylation/deacetylation as well as demethylation/re-methylation of lysine residues of nucleosomal core-derived histones H3 and H4. The main cause of low SCNT efficiency in mammals turns out to be an incomplete reprogramming of transcriptional activity for donor cell-descended genes. It has been ascertained that somatic cell nuclei should undergo the wide DNA cytosine residue demethylation changes throughout the early development of cloned embryos to reset their own overall epigenetic and parental genomic imprinting memories that have been established by re-methylation of the nuclear donor cell-inherited genome during specific pathways of somatic and germ cell lineage differentiation. A more extensive understanding of the molecular mechanisms and recognition of determinants for epigenetic transcriptional reprogrammability of somatic cell nuclear genome will be helpful to solve the problems resulting from unsatisfactory SCNT effectiveness and open new possibilities for common application of this technology in transgenic research focused on human biomedicine.

Regulation of inflammatory mediator expression in bovine endometrial cells: effects of lipopolysaccharide, interleukin 1 beta, and tumor necrosis factor alpha

An abnormal uterine environment can influence maternal-fetal communication, conception rate and disrupt normal embryo development, thereby affecting fertility and the reproductive performance of dairy cows. Animal variability means that development of endometrial cell lines with appropriate characteristic are required. We evaluated the effect of an infectious agent (i.e., bacterial lipopolysaccharide; LPS) and proinflammatory mediators (i.e., Interleukin 1 beta; IL-1β, and tumor necrosis factor alpha; TNFα) on inflammatory mediator gene expression and production by bovine endometrial epithelial (bEEL) and stromal (bCSC) cell lines. Expression of CXCL8/IL8, IL1A, IL1B, and IL6 cytokine genes was significantly upregulated in both epithelial and stromal cells when treated with LPS and IL-1β. LPS treatment of epithelial cells (compared with treatment by IL-1β and TNFα) exhibited greater CXCL8/IL8, IL1A, IL1B, and IL6 cytokine gene expression. Whereas, in stromal cells, IL-1β treatment (compared with LPS and TNFα) exhibited greater CXCL8/IL8, IL1A, IL1B, and IL6 cytokine gene expression. Interestingly, bEEL and bCSC cells treated with IL-1β increased IL1B gene expression, suggesting that IL-1β may act unusually in an autocrine-positive feedback loop. Cytokine production was stimulated by these agents in both cell types. We suggest that the characteristics of these two cell lines make them excellent tools for the study of intrauterine environment.

Is cloning horses ethical?

This paper assesses whether cloning horses is ethical by reviewing ethical arguments against cloning of nonequine species and determining whether they apply to horses, analysing ethical arguments about horse cloning which do not apply to noncompetitive species and considering the ethical dilemmas faced by veterinarians involved in horse cloning. The author concludes that concerns about the health and welfare of cloned horses render the technique ethically problematic and that the onus is on those providing commercial equine cloning services to collate data and provide a stronger evidence base for ethical decision-making.

Phenotype of Cloned Mice: Development, Behavior, and Physiology

Cloning technology has potential to be a valuable tool in basic research, clinical medicine, and agriculture. However, it is critical to determine the consequences of this technique in resulting offspring before widespread use of the technology. Mammalian cloning using somatic cells was first demonstrated in sheep in 1997 and since then has been extended to a number of other species. We examined development, behavior, physiology, and longevity in B6C3F1 female mice cloned from adult cumulus cells. Control mice were naturally fertilized embryos subjected to the same in vitro manipulation and culture conditions as clone embryos. Clones attained developmental milestones similar to controls. Activity level, motor ability and coordination, and learning and memory skills of cloned mice were comparable with controls. Interestingly, clones gained more body weight than controls during adulthood. Increased body weight was attributable to higher body fat and was associated with hyperleptinemia and hyperinsulinemia indicating that cloned mice are obese. Cloned mice were not hyperphagic as adults and had hypersensitive leptin and melanocortin signaling systems. Longevity of cloned mice was comparable with that reported by the National Institute on Aging and the causes of death were typical for this strain of mouse. These studies represent the first comprehensive set of data to characterize cloned mice and provide critical information about the long-term effects of somatic cell cloning.

Welfare in horse breeding

Welfare problems related to the way horses are bred, whether by coitus or by the application of artificial reproduction techniques (ARTs), have been given no discrete consideration within the academic literature. This paper reviews the existing knowledge base about welfare issues in horse breeding and identifies areas in which data is lacking. We suggest that all methods of horse breeding are associated with potential welfare problems, but also that the judicious use of ARTs can sometimes help to address those problems. We discuss how negative welfare effects could be identified and limited and how positive welfare effects associated with breeding might be maximised. Further studies are needed to establish an evidence base about how stressful or painful various breeding procedures are for the animals involved, and what the lifetime welfare implications of ARTs are for future animal generations.

CRISPR/Cas9 nuclease-mediated gene knock-in in bovine-induced pluripotent cells

Efficient and precise genetic engineering in livestock such as cattle holds great promise in agriculture and biomedicine. However, techniques that generate pluripotent stem cells, as well as reliable tools for gene targeting in livestock, are still inefficient, and thus not routinely used. Here, we report highly efficient gene targeting in the bovine genome using bovine pluripotent cells and clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 nuclease. First, we generate induced pluripotent stem cells (iPSCs) from bovine somatic fibroblasts by the ectopic expression of yamanaka factors and GSK3β and MEK inhibitor (2i) treatment. We observed that these bovine iPSCs are highly similar to naïve pluripotent stem cells with regard to gene expression and developmental potential in teratomas. Moreover, CRISPR/Cas9 nuclease, which was specific for the bovine NANOG locus, showed highly efficient editing of the bovine genome in bovine iPSCs and embryos. To conclude, CRISPR/Cas9 nuclease-mediated homologous recombination targeting in bovine pluripotent cells is an efficient gene editing method that can be used to generate transgenic livestock in the future.

HOW SHOULD THE WELFARE OF FETAL AND NEUROLOGICALLY IMMATURE POSTNATAL ANIMALS BE PROTECTED?

Legal protection of the welfare of prenatal animals has not previously been addressed as a discrete subject within the academic literature on animal welfare, ethics and law. This paper aims to rectify this by reviewing the protections (or absence of protections) provided for fetuses by existing legislation in various jurisdictions, and considering the extent to which legal protection of animal fetuses can be justified on animal welfare grounds. Questions related to the need to protect the welfare of neurologically immature postnatal animals are also considered. We argue that there are reasons to protect animal fetuses, both in order to protect fetuses themselves against possible suffering, and in order to protect the animals which fetuses will become against negative welfare impacts that originate prenatally. We review the science on whether fetuses can suffer, and argue that extant regulations do not fully reflect current scientific understanding. Following the precautionary principle, we further argue that regulators should consider the possibility that foetuses and neurologically immature postnatal animals may suffer due to subcortically based 'raw basic affects' (i.e. relatively undifferentiated experiences of discomfort suggested to be generated by neural processing at levels below the cerebral cortex). Furthermore we show that there are reasons for affording fetuses protection in order to safeguard the long-term welfare of future animals. However, it may be possible to provide such protection via rules or laws relating to the use of certain techniques and the management of pregnant animals, rather than via direct legal protection of fetuses themselves. In order to provide such protection effectively we need to know more about the relationship between maternal nutrition, stress, exercise, management and fetal health, and about the impact of the timing of a fetal insult on long-term postnatal welfare.

Resurrection of an alpha-1,3-galactosyltransferase gene-targeted miniature pig by recloning using postmortem ear skin fibroblasts

Animals with a targeted disruption of genes can be produced by somatic cell nuclear transfer (SCNT). However, difficulties in clonal selection of somatic cells with a targeted mutation often result in heterogeneous nuclear donor cells, including gene-targeted and non-targeted cells, and impose a risk of producing undesired wildtype cloned animals after SCNT. In addition, the efficiency of cloning by SCNT has remained extremely low. Most cloned embryos die in utero, and the few that develop to term show a high incidence of postnatal death and abnormalities. In the present study, resurrection of an alpha-1,3-galactosyltransferase (αGT) gene-targeted miniature pig by recloning using postmortem ear skin fibroblasts was attempted. Three cloned piglets were produced from the first round of SCNT, including one stillborn and two who died immediately after birth due to respiratory distress syndrome and cardiac dysfunction. Among the three piglets, two were confirmed to be αGT gene-targeted. Fibroblasts derived from postmortem ear skin biopsies were used as nuclear donor cells for the second round of SCNT, and a piglet was produced. As expected, PCR and Southern analyses confirmed that the piglet produced from recloning was αGT gene-targeted. Currently, the piglet is fourteen months of age, and no overt health problems have been observed. Results from the present study demonstrate that loss of an invaluable animal, such as a gene-targeted miniature pig, may be rescued by recloning, with assurance of the desired genetic modification.

Colcemid-treatment of heifer oocytes enhances nuclear transfer embryonic development, establishment of pregnancy and development to term

Four experiments were designed to examine the effects of colcemid, a microtubule assembly inhibitor, on the development of bovine nuclear transfer (NT) embryos in vitro and in vivo. Recipient oocytes matured at different times were exposed to colcemid. Approximately 80-93% of the exposed oocytes, with or without the first polar body (PB1), developed obvious membrane projections. In Experiment 1, oocytes matured for either 14-15 or 16-17 hr, treated with colcemid and used as recipient cytoplasm for NT resulted in over 40% blastocyst development. In Experiment 2, oocytes matured for 16-17 hr were treated with either 0.2 or 0.4 microg/ml colcemid for 2-3 or 5-6 hr, respectively. The percentages of blastocyst development (39-42%) were not statistically different among the different colcemid treatment groups, but were both higher (P < 0.05) than the control group (30%). Colcemid concentrations and length of colcemid treatment of oocytes did not affect their ability to support NT embryo development to the blastocyst and hatched blastocyst stages. Results from Experiment 3 indicate that semi-defined medium increases morula and blastocyst development of NT embryos derived from colcemid-treated oocytes under 5% CO2 in air atmosphere. In addition, cell numbers of blastocysts in colcemid-treated groups were numerically higher than the control groups. After embryo transfer, higher (P < 0.05) pregnant rates were obtained from the colcemid-treated group than the nontreated group. Five of 40 recipients (12.5%) which received embryos from colcemid-treated oocytes delivered healthy calves, significantly higher than those recipients (3.3%) that received embryos derived from nontreated oocytes.

Differential proteomic analysis of bovine conceptus fluid proteins in pregnancies generated by assisted reproductive technologies

Proteomic analysis of bovine conceptus fluid proteins during early pregnancy has the potential to expose protein species indicative of both the overall health of the fetal-maternal environment and fetal developmental status. In this study, we examined the differential abundance of bovine conceptus fluid proteins (5-50 kDa fraction) from naturally conceived, in vitro fertilisation (IVF) and somatic cell nuclear transfer (SCNT)-derived pregnancies at days 45 and 90 of gestation. In day 45 allantoic fluid (AllF) samples, an atypical cluster of low molecular weight ( approximately 14-16 kDa), low pI (between 3.0 and 4.5 pH units) protein species was increased in three of four IVF samples (30-100-fold increase in protein spot volumes compared to normal). These proteins were identified as paralogs of the bovine cathelicidin antimicrobial protein (CAMP) by MALDI-TOF MS peptide mass fingerprint and MALDI-TOF MS/MS peptide sequence analysis. Peptidoglycan recognition protein and serine (or cysteine) proteinase inhibitor clade B1, were also significantly increased in the corresponding IVF samples. In two of four SCNT AllF samples, a 2-10-fold increase in CAMP protein spot volumes were detected. No aberrant abundance levels of individual protein species were observed in amniotic fluid samples, or in day 90 IVF AllF samples. Identification of unique protein species present in the normal bovine AllF proteome at day 45 is also reported.

Animal models of chronic lung infection with Pseudomonas aeruginosa: useful tools for cystic fibrosis studies

Cystic fibrosis (CF) is caused by a defect in the transmembrane conductance regulator (CFTR) protein that functions as a chloride channel. Dysfunction of the CFTR protein results in salty sweat, pancreatic insufficiency, intestinal obstruction, male infertility and severe pulmonary disease. In most patients with CF life expectancy is limited due to a progressive loss of functional lung tissue. Early in life a persistent neutrophylic inflammation can be demonstrated in the airways. The cause of this inflammation, the role of CFTR and the cause of lung morbidity by different CF-specific bacteria, mostly Pseudomonas aeruginosa, are not well understood. The lack of an appropriate animal model with multi-organ pathology having the characteristics of the human form of CF has hampered our understanding of the pathobiology and chronic lung infections of the disease for many years. This review summarizes the main characteristics of CF and focuses on several available animal models that have been frequently used in CF research. A better understanding of the chronic lung infection caused particularly by P. aeruginosa, the pathophysiology of lung inflammation and the pathogenesis of lung disease necessitates animal models to understand CF, and to develop and improve treatment.

Cell-cycle synchronization of fibroblasts derived from transgenic cloned cattle ear skin: effects of serum starvation, roscovitine and contact inhibition

The purpose of the present study was to evaluate the effects of serum-starvation, contact-inhibition and roscovitine treatments on cell-cycle synchronization at the G0/G1 stage of ear skin fibroblasts isolated from transgenic cloned cattle. The developmental competence of re-cloned embryos was also examined. Our results showed that the proportion of G0/G1 cells from the serum-starved group at 3, 4 or 5 days was significantly higher compared with 1 or 2 days only (91.5, 91.7 and 93.5% versus 90.1 and 88.8%, respectively, p < 0.05); whilst there was no statistical difference among cells at 3, 4 or 5 days. For roscovitine-treated cells, the proportion of G0/G1 cells at 2, 3, 4 or 5 days was significantly higher than those treated for 1 day only (91.1, 90.1, 89.4 and 91.3% versus 86.51%, respectively, p < 0.05). The proportion of contact-inhibited G0/G1 cells rose significantly with treatment time, but was similar at 3, 4 and 5 days (89.4, 90.4, 91.4, 91.6 and 92.1%, respectively, p < 0.05). The efficiency of obtaining G0/G1 phase cells was lower when roscovitine treatment was employed to synchronize the cell cycle compared with the serum-starvation and contact-inhibition methods (89.7 versus 91.1% and 91.0%, p < 0.05). Moreover, obvious differences were observed in the rate of fused couplets and blastocysts (89.88 +/- 2.70 versus 87.40 +/- 5.13; 44.10 +/- 8.62 versus 58.38 +/- 13.28, respectively, p < 0.05), when nuclear transfer embryos were reconstructed using donors cells that had been serum starved or contact inhibited for 3 days. Our data indicate that 3 day treatment is feasible for harvesting sufficient G0/G1 cells to produce re-cloned transgenic bovine embryos, regardless of whether serum-starvation, contact-inhibition or roscovitine treatments are used as the synchronization methods.

Genomics and ethics: the case of cloned and/or transgenic animals

The point of the present study is to illustrate and, if possible, promote the existing link between genomics and ethics, taking the example of cloned and transgenic animals. These ‘new animals’ raise theoretical and practical problems that concern applied ethics. We will explore more particularly an original strategy showing that it is possible, starting from philosophical questioning about the nature of identity, to use a genomic approach, based on amplification fragment length polymorphism (AFLP) and methylation-sensitive amplification polymorphism (MSAP) detection, to provide useful tools to define more rigorously what cloned animals are, by testing their genetic and epigenetic identity. We expect from the future results of this combined approach to stimulate the creativity of the philosophical and ethical reflection about the impact of biotechnology on animals, and to increase scientific involvement in such issues.

Aberrant gene expression in deceased transgenic cloned calves

Several transgenic cloned species have been obtained; however, the efficiency of transgenic cloning remains very low, even lower than cloning. Many experiments have demonstrated abnormal growth and development, and inappropriate gene expression in cloned animals. In this study, we examined the expression of 19 development-related genes in lungs of three normal controls and three aberrant transgenic cloned calves. Results showed in transgenic cloned calves, 84.2% genes had decreased expression levels, however, 5.3% genes had increased levels. This study suggests transgenic cloning and the aberrant expression would cause abnormal growth and development in transgenic cloned calves. To our knowledge, this is the first time that gene expression was examined in transgenic cloned cattle. These findings may have some implications in understanding the low efficiency of the transgenic cloning.

Cloned horse pregnancies produced using adult cumulus cells

The objectives of the present study were to: (1) clone horses using adult cumulus cells; and (2) determine whether the cumulus cell donor affected the outcome. In vivo-matured cumulus-oocyte complexes were obtained using transvaginal ultrasound-guided follicle aspiration; oocytes were used as cytoplasts, whereas cumulus cells (from one of three different mares) were used as donor cells. Immediately following nuclear transfer and activation procedures, cloned embryos were transferred surgically to the oviduct of recipient mares (n = 2-5 embryos per recipient) that had ovulated within 24 h prior to the transfer. An initial pregnancy examination was performed between Days 14 and 16 (Day 0 = surgery); subsequent examinations were then performed every 7-10 days. A total of 136 follicles were aspirated in 96 mares, from which 72 oocytes were recovered (53%). Sixty-two cloned embryos were transferred to recipient mares, which resulted in seven (11.3%) ultrasonographically detectable conceptuses between Days 14 and 16. All seven conceptuses were lost spontaneously between Days 16 and 80. Cumulus cells from Mare 160 tended (P = 0.08) to result in a higher embryo survival rate than cumulus cells from Mare 221 (4/17 v. 1/25 respectively). To our knowledge, this is the first report documenting the establishment of cloned equine pregnancies derived from adult cumulus cells.

Dairy cattle exploratory and social behaviors: is there an effect of cloning?

While an increasing number of animals are produced by means of somatic cloning, behavioral studies on cloned animals are still rare. The aim of this study was to investigate whether the somatic cloning procedure has an influence on locomotion, exploratory, vocal and social behaviors of heifers. Ten heifers were used in the present study. Five of them were cloned heifers derived from somatic cells of three different Prim'Holstein cows and five others were same-age control heifers produced by artificial insemination. In addition to observations of social behaviors in the stable group, each animal was placed individually for a short time in an unfamiliar environment. Our results failed to show any statistical differences between clones and their controls both in frequencies of agonistic and non-agonistic behaviors. However, cloned heifers showed significantly more non-agonistic and less agonistic behaviors towards other cloned partners than towards control ones. This result also stood for control heifers. As far as their Hierarchical Index was concerned, three cloned heifers were highest ranking and two others lowest ranking. In this herd, social dominance appeared to be linked to body weight and age rather than to a cloning effect. In an unfamiliar environment, cloned and control subjects exhibited the same level of locomotion and vocalization. However, cloned heifers showed more exploratory behaviors than did control ones. This difference could be due to environmental factors during the postnatal period rather than to cloning.

Supplementation of fructose in chemically defined protein-free medium enhances the in vitro development of bovine transgenic cloned embryos

The present study evaluated the possible embryotrophic role of fructose supplementation in chemically defined protein-free KSOM on in vitro development of bovine transgenic cloned embryos. Bovine fetal fibroblasts transfected with expression plasmids for bovine prion protein (PrP) mutant gene with GFP marker gene were used as donor nuclei for reconstruction of slaughterhouse-derived in vitro matured oocytes. The reconstructed oocytes were cultured in KSOM supplemented with 0.01% PVA (KSOM-PVA) at 39 degrees C in a humidified atmosphere of 5% CO2, 5% O2 and 90% N2 for 192 h. In Experiment 1, when reconstructed oocytes were cultured in KSOM-PVA supplemented with glucose (0.2 mM), fructose (1.5 mM) or combined glucose and fructose (0.2 and 1.5 mM, respectively), significantly (p < 0.05) higher blastocyst (19.2%) and hatching/hatched blastocyst (13.1%) formation rates were obtained in combined fructose and glucose supplemented medium than glucose supplemented counterpart (10.0% and 5.7%, respectively). In Experiment 2, when reconstructed oocytes were cultured in KSOM-PVA supplemented with 0.0, 0.2, 1.5, 3.0 and 5.6 mM fructose in combination with 0.2 mM glucose, the blastocyst formation rate was significantly higher (17.6%) in 1.5 mM fructose supplemented group than that of no fructose supplemented counterpart (9.7%; p > 0.05). In conclusion, supplementation of combined fructose (1.5 mM) and glucose (0.2 mM) in chemically defined protein-free KSOM enhances the in vitro development of bovine transgenic cloned embryos.

Somatic cell nuclear transfer in pigs: recent achievements and future possibilities

During the past 6 years, considerable advancement has been achieved in experimental embryology of pigs. This process was mainly generated by the rapidly increasing need for transgenic pigs for biomedical research purposes, both for future xenotransplantation to replace damaged human organs or tissues, and for creating authentic animal models for human diseases to study aetiology, pathogenesis and possible therapy. Theoretically, among various possibilities, an established somatic cell nuclear transfer system with genetically engineered donor cells seems to be an efficient and reliable approach to achieve this goal. However, as the result of unfortunate coincidence of known and unknown factors, porcine embryology had been a handicapped branch of reproductive research in domestic animals and a very intensive and focused research was required to eliminate or minimise this handicap. This review summarises recent achievements both in the background technologies (maturation, activation, embryo culture) and the actual performance of the nuclear replacement. Recent simplified methods for in vivo development after embryo transfer are also discussed. Finally, several fields of potential application for human medical purposes are discussed. The authors conclude that although in this early phase of research no direct evidence can be provided about the practical use of transgenic pigs produced by somatic cell nuclear transfer as organ donors or disease models, the future chances even in medium term are good, and at least proportional with the efforts and sums that are invested into this research area worldwide.

Effect of embryonic cell cycle of nuclear donor embryos on the efficiency of nuclear transfer in Japanese black cattle

In the present study, the development in vitro and in vivo of nuclear transfer (NT) embryos reconstructed with embryonic cells (blastomeres) at the 32- to 63-cell (sixth cell cycle) and 64- to 127-cell (seventh cell cycle) stages was investigated to determine the optimum range of embryonic cell cycles for yielding the highest number of identical calves in Japanese black cattle. Rates of development to the blastocyst stage (overall efficiency) were higher in the sixth cell-cycle stage (45%) than in the seventh cell-cycle stage (12%). After the transfer of the blastocysts reconstructed with blastomeres of the sixth and seventh cell cycle-stage embryos to recipient heifers, there were no differences in the pregnancy (14/35: 40% versus 3/13: 23%, respectively) or calving rates (11/39: 28% versus 3/13: 23%, respectively). These results indicate that the highest number of identical calves would be obtained by using sixth cell cycle (32- to 63-cell)-stage embryos as nuclear donors.

Somatic cell nuclear transfer using transported in vitro-matured oocytes in cynomolgus monkey

Somatic cell nuclear transfer (SCNT) is not successful so far in non-human primates. The objective of this study was to investigate the effects of stimulation cycles (first and repeat) on oocyte retrieval and in vitro maturation (IVM) and to evaluate the effects of stimulation cycles and donor cell type (cumulus and fetal skin fibroblasts) on efficiency of SCNT with transported IVM oocytes. In this study, 369 immature oocytes were collected laparoscopically at 24 h following human chorionic gonadotrophin (hCG) treatment from 12 cynomolgus macaque (Macaca fascicularis) in 24 stimulation cycles, and shipped in pre-equilibrated IVM medium for a 5 h journey, placed in a dry portable incubator (37 °C) without CO2 supplement. A total of 70.6% (247/350) of immature oocytes reached metaphase II (MII) stage at 36 h after hCG administration, MII spindle could be seen clearly in 80.6% (104/129) of matured IVM oocytes under polarized microscopy. A total of 50.0% (37/74) of reconstructive SCNT embryos cleaved after activation; after cleavage, 37.8% (14/37) developed to the 8-cell stage and 8.1% (3/37) developed to morula, but unfortunately none developed to the blastocyst stage. Many more oocytes could be retrieved per cycle from monkeys in the first cycle than in repeated cycles (19.1 vs. 11.7, p < 0.05). There were no significant differences in the maturation rate (70.0 vs. 71.4%, p > 0.05) and MII spindle rate under polarized microscopy (76.4 vs. 86.0%, p > 0.05) between the first and repeat cycles. There were also no significant differences in the cleavage rate, and the 4-cell, 8-cell and morula development rate of SCNT embryos between the first and repeat cycles. When fibroblast cells and cumulus cells were used as the donor cells for SCNT, first cleavage rate was not significantly different, but 4-cell (50.0 vs. 88.9%, p < 0.05) and 8-cell (0 vs. 51.9%, p < 0.01) development rate were significantly lower for the former. In conclusion, the number of stimulation cycles has a significant effect on oocyte retrieval, but has no effect on maturation and SCNT embryo development; however, different donor cell types (cumulus and fibroblast) resulted in different developmental potentials of SCNT embryos.

Dynamic changes in microtubules and early development of reconstructed embryos after somatic cell nuclear transfer in a non-human primate

In order to improve somatic cell nuclear transfer (SCNT) efficiency and to understand cellular changes in SCNT, the dynamic changes in microtubules/DNA and early development of SCNT embryos with single or multiple pronuclei were investigated, along with activation timing on efficiency of SCNT, were studied in the Cynomolgus monkey. The confocal images showed that microtubules assembled around condensed DNA at 1h after cell injection; normal or abnormal reconstructed spindle formed at 2 h after cell injection; and reconstructed spindle separated at 2 h after activation. The results of nuclear formation showed that 61.3% of the reconstructed embryos did not form pronuclei; 19.3% formed a single nucleus, and 11.9% and 7.5% formed two and more than two reconstructed pronuclei, respectively. The cleavage and 8-cell development rates of SCNT embryos with pronuclei were significantly higher than those without pronuclei, but there was no difference in development rates among NT embryos with single, two and more then two pronuclei. Activation at 2 h after cell injection yielded more embryos with pronuclei and yielded 8-cell NT embryos more reliably than did activation at 3-4 h. In conclusion, microtubules assembled around condensed DNA at 1-2 h after cell injection, and formed a spindle at 2 h after SCNT, which separated at 2 h after activation; early development was affected by activation time, but no different between single and multiple pronuclei.

Cloning cattle: the methods in the madness

Somatic cell nuclear transfer (SCNT) is much more widely and efficiently practiced in cattle than in any other species, making this arguably the most important mammal cloned to date. While the initial objective behind cattle cloning was commercially driven--in particular to multiply genetically superior animals with desired phenotypic traits and to produce genetically modified animals-researchers have now started to use bovine SCNT as a tool to address diverse questions in developmental and cell biology. In this paper, we review current cattle cloning methodologies and their potential technical or biological pitfalls at any step of the procedure. In doing so, we focus on one methodological parameter, namely donor cell selection. We emphasize the impact of epigenetic and genetic differences between embryonic, germ, and somatic donor cell types on cloning efficiency. Lastly, we discuss adult phenotypes and fitness of cloned cattle and their offspring and illustrate some of the more imminent commercial cattle cloning applications.

Early development of reconstructed embryos after somatic cell nuclear transfer in a non-human primate

To improve efficiency and assess variation in nuclear transfer techniques in non-human primates, we investigated the following factors: type of donor cell, interval between enucleation and cell injection, activation after electrical pulsing and cytokinesis inhibitors. An average of 16.4 oocytes were recovered from 91 retrievals; however, 15 (14%) additional retrieval attempts yielded no oocytes due to a failure of follicular stimulation. Oocyte maturation rates at 36, 38 and 40 h post-hCG were 46.2, 52.6 and 61.2%, respectively. The MII spindle could be seen clearly using polarized microscopy in 89.1% (614/689) of oocytes. Nuclei were seen in 42% of the NT couplets, 53% of those cleaved to the 2-cell stage and 63% of the 2-cell embryos developed to the 8-cell stage by Day 3. There was no difference in the occurrence of nuclear formation between couplets created using fibroblasts or cumulus cells, although embryos were more reliably produced with fibroblasts. The interval (2, 3 and 4 h) between enucleation and cell injection did not affect NT efficiency. Ethanol treatment after electrical pulses yielded more 2-cell NT embryos than did treatment with ionomycin, but the frequency of nuclear formation and development to the 8-cell stage was not different. Treatment of couplets with cycloheximide and cytochalasin B for 5 h after activation had no impact on NT efficiency.

Placental abnormalities associated with post-natal mortality in sheep somatic cell clones

We report on cloning experiments designed to explore the causes of peri- and post-natal mortality of cloned lambs. A total of 93 blastocysts obtained by nuclear transfer of somatic cells (granulosa cells) were transferred into 41 recipient ewes, and pregnancies were monitored by ultrasound scanning. In vitro derived, fertilized embryos (IVF, n=123) were also transferred to assess oocyte competence, and naturally mated ewes (n=120) were analysed as well. Cloned embryos developed to the blastocyst stage and implanted at the same rate as IVF embryos. After day 30 of gestation, however, dramatic losses occurred, and only 12 out of 93 (13%) clones reached full-term development, compared to 51 out of 123 (41.6%) lambs born from the IVF control embryos. Three full-term lamb clones were delivered stillborn, as a result of placental degeneration. A further five clone recipients developed hydroallantois. Their lambs died within 24h following delivery by caesarian section, and displayed degenerative lesions in liver and kidney resulting from the severe hydroallantois. One set of twins was delivered by assisted parturition at day 150, but died 24h later due to respiratory distress syndrome. The remaining two clone recipients underwent caesarian section, and the corresponding two lambs displayed signs of respiratory dysfunction and died at approximately 1 month of age due to a bacterial complication. Blood samples collected from the cloned lambs after birth revealed a wide range of abnormalities indicative of kidney and liver dysfunction. Macroscopical and histopathological examination of the placentae revealed a marked reduction in vascularization, particularly at the apex of the villous processes, as well as a loss of differentiation of the trophoblastic epithelium. Our results strongly suggest that post-mortality in cloned lambs is mainly caused by placental abnormalities.

Comparison of gene expression in individual preimplantation bovine embryos produced by in vitro fertilisation or somatic cell nuclear transfer

In vitro fertilisation (IVF) and somatic cell nuclear transfer (SCNT) have been implicated in a variety of developmental abnormalities. Aberrant gene expression is likely to account for much of the diminished viability and developmental abnormalities observed. In the present study, the expression of multiple genes in IVF and SCNT bovine blastocyst-stage embryos were evaluated and compared with in vivo-produced embryos. Eleven genes expressed at and following maternal-zygotic transcription transition were evaluated in individual blastocysts by real-time polymerase chain reaction following RNA amplification. A subset of those genes was also evaluated in individual IVF and SCNT eight-cell embryos. A fibroblast-specific gene, expressed by nuclear donor cells, was also evaluated in IVF and SCNT embryos. The observed gene expression pattern at the eight-cell stage was not different between IVF and SCNT embryos (P > 0.05). In vitro fertilisation and SCNT blastocyst expression was lower (P < 0.01) for all genes compared with their in vivo-produced counterparts, except for lactate dehydrogenase isoenzyme A (P < 0.001). The patterns of gene expression of the IVF and SCNT blastocysts were indistinguishable. Neither SCNT eight-cell nor blastocyst-stage embryos expressed the gene used as a fibroblast marker (collagen VIalpha1). For the genes evaluated, the level of expression was influenced more by the environment than by the method used to produce the embryos. These results support the notion that if developmental differences observed in IVF- and SCNT-produced fetuses and neonates are the result of aberrant gene expression during the preimplantation stage, those differences in expression are subtle.

Embryo technologies and animal health – consequences for the animal following ovum pick-up, in vitro embryo production and somatic cell nuclear transfer

Mammalian reproductive technologies that aim either to complement or to transcend conventional livestock breeding options have contributed to some of the most remarkable achievements in the field of reproductive biology in recent decades. In so doing they have extended our horizons in two distinct dimensions, the first concerning what it is technically possible to achieve and the second relating to the time-frame within which an individual's life-long developmental capability is initially established and ultimately realized or undermined. Our impressions of the benefits and values, or otherwise, of technologies such as in vitro embryo production and nuclear transfer are rightly influenced by the extent to which they impinge on the health of animals either subjected to or derived from them. Here, we consider some of the health implications of oocyte/embryo-centric technologies applied to farm livestock.

Generation of transgenic rabbits by the novel technique of chimeric somatic cell cloning

A novel technique of chimeric somatic cell cloning was applied to produce a transgenic rabbit (NT20). Karyoplasts of transgenic adult skin fibroblasts with Tg(Wap-GH1) gene construct as a marker were microsurgically transferred into one, previously enucleated, blastomere of 2-cell non-transgenic embryos, while the second one remained intact. The reconstructed embryos either were cultured in vitro up to the blastocyst stage (Experiment I) or were transferred into recipient-females immediately after the cloning procedure (Experiment II). In Experiment I, 25/102 (24.5%) embryos formed blastocysts from whole embryos and 46/102 (44.12%) embryos developed to the blastocyst stage from single non-operated blastomeres, while the reconstructed blastomeres were damaged and degenerated. Thirteen (12.7%) embryos did not exceed 3- to 4-cell stages and 18 (17.7%) embryos were inhibited at the initial 2-cell stage. Out of 14 blastocysts which were subjected to molecular analysis, the transgene was detected in the cells of 4 blastocysts. In Experiment II, 163/217 (75.0%) embryos were transferred into 9 pseudopregnant recipient-rabbits (an average of 18 embryos per recipient). Four recipient-females (44.4%) became pregnant and delivered a total of 24 (14.7%) pups. Molecular analysis confirmed that two pups (1.2%), one live and one stillborn, showed a positive transgene signal. Live transgenic rabbit NT20 appeared healthy and anatomically as well as physiologically normal. The results of our experiments showed that transgenic adult skin fibroblast cell nuclei, which have been introduced into the cytoplasmic microenvironment of single enucleated blastomeres from 2-cell stage rabbit embryos, are able to direct the development of chimeric embryos not only to the blastocyst stage but also up to term.

Transgenic modifications of the rat genome

The laboratory rat (R. norvegicus) is a very important experimental animal in several fields of biomedical research. This review describes the various techniques that have been used to generate transgenic rats: classical DNA microinjection and more recently described techniques such as lentiviral vector-mediated DNA transfer into early embryos, sperm-mediated transgenesis, embryo cloning by nuclear transfer and germline mutagenesis. It will also cover techniques associated to transgenesis such as sperm cryopreservation, embryo freezing and determination of zygosity. The availability of several technologies allowing genetic manipulation in the rat coupled to genomic data will allow biomedical research to fully benefit from the rat as an experimental animal.

Equine cloning: applications and outcomes

Cloning is one of several new assisted reproductive techniques being developed for clinical use in the equine industry. Potential uses of equine cloning include: (1) the preservation of genetics from individual animals that would otherwise not be able to reproduce, such as geldings; (2) the preservation of genetic material of endangered and/or exotic species, such as the Mongolian wild horse (Przewalski’s horse); and (3) because of the companion animal role that horses fill for some individuals, it is likely that some horse owners will have individual animals cloned for emotional fulfillment. Although equine cloning has been successful, like other species, it remains a very inefficient process (<3% success). In most species, the inefficiency of cloning results from a high incidence of embryonic, fetal and/or placental developmental abnormalities that contribute to extremely high rates of embryonic loss, abortion and stillbirths throughout gestation and compromised neonatal health after birth. The present review describes some of the ultrasonographic, endocrinological and histopathological characteristics of successful (produced viable offspring) and unsuccessful (resulted in pregnancy failure) cloned equine (mule and horse) pregnancies we have produced. A total of 21 cloned mule pregnancies were established using fetal fibroblast cells, whereas a total of seven cloned horse pregnancies were established using adult cumulus cells. Three of the cloned mule conceptuses were carried to term, resulting in the birth of three healthy clones. This information adds to an accumulating body of knowledge about the outcome of cloned equine pregnancies, which will help to establish when, and perhaps why, many cloned equine pregnancies fail.

Agro-economic impact of cattle cloning

The purpose of this paper is to review the economic and social implications of cloned cattle, their products, and their offspring as related to production agriculture. Cloning technology in cattle has several applications outside of traditional production agriculture. These applications can include bio-medical applications, such as the production of pharmaceuticals in the blood or milk of transgenic cattle. Cloning may also be useful in the production of research models. These models may or may not include genetic modifications. Uses in agriculture include many applications of the technology. These include making genetic copies of elite seed stock and prize winning show cattle. Other purposes may range from "insurance" to making copies of cattle that have sentimental value, similar to cloning of pets. Increased selection opportunities available with cloning may provide for improvement in genetic gain. The ultimate goal of cloning has often been envisioned as a system for producing quantity and uniformity of the perfect dairy cow. However, only if heritability were 100%, would clone mates have complete uniformity. Changes in the environment may have significant impact on the productivity and longevity of the resulting clones. Changes in consumer preferences and economic input costs may all change the definition of the perfect cow. The cost of producing such animals via cloning must be economically feasible to meet the intended applications. Present inefficiencies limit cloning opportunities to highly valued animals. Improvements are necessary to move the applications toward commercial application. Cloning has additional obstacles to conquer. Social and regulatory acceptance of cloning is paramount to its utilization in production agriculture. Regulatory acceptance will need to address the animal, its products, and its offspring. In summary, cloning is another tool in the animal biotechnology toolbox, which includes artificial insemination, sexing of semen, embryo sexing and in vitro fertilization. While it will not replace any of the above mentioned, its degree of utilization will depend on both improvement in efficiency as well as social and regulatory acceptance.

Growth, Reproduction, and Lactation in Somatic Cell Cloned Cows with Short Telomeres

We previously showed that telomere lengths of 10 somatic cell cloned cows were significantly shorter than normal. In this study, we investigated growth, reproduction, and lactation in these animals to determine if shortened telomeres have any effect on these characteristics. Six Holstein and 4 Jersey cloned cows, derived from oviduct cells, were reared under general group feeding. Body weights were recorded from birth to 48 mo of age. A number of reproductive characteristics were screened during the prepubertal, postpubertal, and postpartum periods. After parturition, milk yields were recorded daily and percentages of milk fat, proteins, and solids-not-fat were measured at monthly intervals. These data were used to estimate production of milk components over a 305-d period. Overall, the cloned heifers exceeded standard growth rates for each breed. The cows were inseminated at the first estrus after they reached 450 d of age, and delivered normal calves except for one stillbirth in the Holstein group. They were inseminated at postpartum estrus to provide second and third parturitions and, again, these pregnancies were normal. Gestational periods and birth weights of the calves were both within the normal range. The average total milk yield per cow in Holstein group clones was less than that of the original cow, whereas Jersey group clones showed a higher average milk yield than the original cow. In both groups of cloned cows, inter-individual variation in milk production was relatively large; however, the coefficient of variation was less than 10%. Our results suggest that the cloned cows have normal growth, reproductive, and lactation characteristics, and thus normal productivity, despite having reduced telomere lengths.

Improving in vitro development of cloned bovine embryos with hybrid (Holstein–Chinese Yellow) recipient oocytes recovered by ovum pick up

In the present study, oocytes from F1 hybrid cattle, as well as their parental lines, were recovered by ovum pick up (OPU) and used as recipient cytoplasm for somatic cell nuclear transfer (SCNT). Four F1 hybrid (Holstein dam x Chinese Yellow sire), 10 Holstein and four Chinese Yellow cattle were subjected to OPU once weekly. There were no significant differences among breeds for number of recovered oocytes per session (overall average, 7.8+/-0.5; mean+/-S.E.M.), quality of the recovered oocytes, or oocyte maturation rate (72-73%). Matured oocytes were all used as recipient cytoplasm (without selection) and a single batch of cumulus cells collected from a Holstein cow were used as donor cells. Although reconstructed embryos initiated cleavage sooner when the recipient cytoplasm was from hybrid cattle versus the two parental breeds, the overall cleavage rate was indistinguishable among breeds. At Day 8, the blastocyst rate from the cleaved embryos (51% versus 37% and 27%), the total number of cells per blastocyst (135+/-4.1 versus 116+/-3.6 and 101+/-4.2), and the percentage of Grade-A (excellent quality) blastocysts (54% versus 42% and 29%) in the hybrid group were all higher than that of Holstein and Yellow groups. Furthermore, the proportion of blastocysts obtained at Day 7 (as a percentage of the total number of blastocysts) was greater in the hybrid group than in Holstein and Yellow groups (89% versus 71% and 63%). In conclusion, the use of F1 hybrid oocytes as recipient cytoplasm significantly improved in vitro development of cloned bovine embryos relative to oocytes derived from the parental lines.

X chromosome reactivation and regulation in cloned embryos

Somatic cell nuclear transfer embryos exhibit extensive epigenetic abnormalities, including aberrant methylation and abnormal imprinted gene expression. In this study, a thorough analysis of X chromosome inactivation (XCI) was performed in both preimplantation and postimplantation nuclear transfer embryos. Cloned blastocysts reactivated the inactive somatic X chromosome, possibly in a gradient fashion. Analysis of XCI by Xist RNA and Eed protein localization revealed heterogeneity within cloned embryos, with some cells successfully inactivating an X chromosome and others failing to do so. Additionally, a significant proportion of cells contained more than two X chromosomes, which correlated with an increased incidence of tetraploidy. Imprinted XCI, normally found in preimplantation embryos and extraembryonic tissues, was not observed in blastocysts or placentae from later stage clones, although fetuses recapitulated the Xce effect. We conclude that, although SCNT embryos can reactivate, count, and inactivate X chromosomes, they are not able to regulate XCI consistently. These results illustrate the heterogeneity of epigenetic changes found in cloned embryos.

The problematic in-vitro embryo in the age of epigenetics

During use of many assisted reproductive technologies, the embryo spends time in vitro. The immediate and long-term epigenetic impacts of this exposure to an in-vitro environment are discussed in the context of the health of the offspring. Three exemplary types of possible epigenetic impact are discussed: embryonic cell numbers, mitochondria, and genomic imprints. There is evidence that all of these can be affected in the short term and that these short-term impacts can have heritable consequences across developmental cell generations into maturity. There is also evidence of association between the observed impact and pathology, but as yet no unequivocal evidence of causality for humans and mice. The problematic in-vitro embryo is considered paradigmatic for a central question facing biology: how does the environment interact epigenetically with the genome to produce variable phenotypic outcomes?

Effects of Confluent, Roscovitine Treatment and Serum Starvation on the Cell-cycle Synchronization of Bovine Foetal Fibroblasts

The present study was designed to examine the effects of cell-cycle synchronization protocols, such as confluent, roscovitine treatment and serum starvation, in bovine foetal fibroblasts on synchronization accuracy at G0/G1, viability, apoptosis, necrosis and ploidy for use as a nuclei donor. The cells in 5-10 passages were randomly allocated into three treated groups. Cells were cultured either in Dulbecco's modified Eagle's medium (DMEM) + 10% foetal bovine serum (FBS) until 90% confluent (group 1, confluent), in DMEM + 10% FBS + 30 microM roscovitine for 12 h (group 2, roscovitine), or in DMEM + 0.5% FBS for 5 days (group 3, serum starvation). Most of the cells (>80%) in all groups were arrested at the G0/G1 stage. Although the rates did not differ, cells in group 1 showed an increased cell population arrested at the G0/G1 phase. Significantly (p < 0.05) higher rates of apoptosis occurred in group 3 than in group 1 and 2 (10% vs 6% and 6%, respectively). No differences in chromosomal abnormality were observed among groups. However, by increasing the number of cell culture passages up to 15, significantly (p < 0.05) higher chromosomal abnormality was observed than in 5 and 10 passages (39% vs 28% and 23%, respectively) in group 1. The results clearly indicated that bovine foetal fibroblasts could be effectively synchronized at G0/G1 stages by all the three different treatments, confluent, roscovitine and serum starvation. However, cells in confluent showed reduced apoptosis and necrosis when they underwent 5-10 passages, exhibiting increased percentage of cells with stable chromosome diversity. Hence, cells in confluent merit further studies before they could be used as nuclear donors.

Birth of calves expressing the enhanced green fluorescent protein after transfer of fresh or vitrified/thawed blastocysts produced by somatic cell nuclear transfer

The present study examined effects of genetic manipulation and serum starvation on in vitro developmental potential of bovine somatic cell nuclear transfer (SCNT) embryos and vitrification on in vivo developmental competence of transgenic SCNT blastocysts. Fetal oviduct epithelial cells (FOECs) were isolated from the oviduct of a Day 147 bovine fetus and transfected with a plasmid (pCE-EGFP-IRES-NEO) containing the enhanced green fluorescent protein (EGFP) and neomycin-resistant (Neor) genes. There were no significant differences (P > 0.05) in cleavage rates or development rates to the blastocyst stage for SCNT embryos derived from FOECs (72.5 and 47.8%, respectively) or transfected FOECs (TFOECs, 73.8 and 47.7%, respectively); nor from serum-fed (73.6 and 47.2%, respectively) or serum-starved (72.7 and 48.3%, respectively) cells. Seventeen of Day 7 GFP-embryos (eight fresh blastocysts and nine vitrified/thawed blastocysts ) were transferred to recipients with one embryo per recipient. Two (25%) recipients were confirmed pregnant at Day 60 in fresh blastocysts group, and three recipients (33%) were confirmed pregnant at Day 60 in vitrified/thawed blastocysts group. Two healthy calves (25%) were obtained from fresh blastocysts and one (11%) from vitrified/thawed blastocysts. Microsatellite analysis confirmed that the three clones were genetically identical to the donor cells. Moreover, PCR and Southern blot demonstrated integration of transgene in genomic DNA of all three cloned calves. Expression of GFP in skin biopsies isolated from transgenic cloned calves and fibroblasts derived from the skin biopsies revealed the activity of EGFP gene, and G418 resistance in vitro of these fibroblasts confirmed the activity of Neor gene. Our results show that genetic manipulation and serum starvation of donor cells (FOECs) do not affect in vitro developmental competence of bovine SCNT embryos, and vitrified transgenic SCNT blastocysts can develop to term successfully.

Comparison of two approaches to nuclear transfer in the bovine: hand-made cloning with modifications and the conventional nuclear transfer technique

The aim of the present study was to compare the in vitro and in vivo developmental competence of hand-made cloning (HMC) embryos with the conventional nuclear transfer (NT) method using five somatic cell lines and in vitro-fertilised (IVF; control) embryos. Modifications to the HMC procedure included fusion efficiency optimisation, effect of cytoplasmic volume and cloned embryo aggregation. The developmental competence of blastocysts from each of the treatment groups and cell lines used was assessed following transfer to 345 recipients. Vitrification was also used to enable management of recipient resources and to assess the susceptibility of membranes to cryopreservation following zona removal. Increasing cytoplasmic volume to 150% or aggregating two embryos improved the blastocyst development rate and increased the total cell number. Although HMC embryo transfers established a significantly higher pregnancy rate on Day 30 than fresh IVF or NT embryo transfers, the overall outcome in terms of cloned live births derived from either fresh or vitrified/thawed HMC or NT embryo transfers across the five cell lines did not differ. The birth and continued survival of clones produced with HMC technology with equivalent efficiency to NT shows that it can be used as an alternative method for the generation of cloned offspring in the bovine.

Activated bovine cytoplasts prepared by demecolcine-induced enucleation support development of nuclear transfer embryos in vitro

Demecolcine-induced enucleation (IE) of mouse oocytes has been shown to improve development to term of cloned mice. In this study, we characterized the kinetics and morphological progression of bovine oocytes subjected to IE, and evaluated their ability to support embryo development to the blastocyst stage after nuclear transfer (NT). In vitro matured bovine oocytes were parthenogenetically activated and subsequently exposed to demecolcine at various times post-activation. Onset and duration of demecolcine treatment significantly altered activation and IE frequencies, which varied from 7.1% to 100% and 33.3% to 91.7%, respectively, at 5 hr post-activation. A significant decrease in IE frequencies was observed at 17 hr post-activation (3.4%-46.1%), possibly due to reincorporation of chromosomes into the oocyte after incomplete second polar body (PB) extrusion. Oocytes were reconstructed by NT before (treatment 1) or after (treatment 2) activation and demecolcine treatment, and cultured in vitro. Cleavage (48.1%-54.2%) and blastocyst rates (15.7%-19%) were equivalent for the two treatments, as well as the total cell number in NT blastocysts. Furthermore, most of the blastocysts were completely diploid (treatment 2) or heteroploid but with a majority of diploid nuclei (treatment 1). Our results demonstrate that the IE method can be successfully used to produce enucleated bovine cytoplasts that are competent to support development to the blastocyst stage after NT. This technically simple approach may provide a more efficient method to enhance the success rate of NT procedures. Further studies are needed to improve the in vitro development efficiency and to expand our understanding of the mechanism(s) involved in demecolcine-induced enucleation.

Subzonal Older Adult Fibroblast Insertion in Both In Vivo–Fertilized and Nuclear Transfer Rabbit Zygotes and Embryos: Effects on Further In Vitro Embryo Development

In the present work, we evaluated the effect on further in vitro embryo development of inserting rabbit adult fibroblasts into in vivo-fertilized rabbit embryos. To this end, we inserted either 4 or 15-20 rabbit adult fibroblasts in two different early embryo stages of development, 1-cell stage and 4-8-cell stage embryos. We observed that fibroblast insertion not only did not negatively affect further embryo development, but also may have exerted a positive effect on development on it. Therefore, in forthcoming works were where we intend to study a possible cell helper role on early embryo development. The early embryo microenvironment may reprogram somatic cell gene expression of fibroblasts inserted within the embryo, making them suitable as nuclear donors.

Gene Therapy: The Potential Applicability of Gene Transfer Technology to the Human Germline

The theoretical possibility of applying gene transfer methodologies to the human germline is explored. Transgenic methods for genetically manipulating embryos may in principle be applied to humans. In particular, microinjection of retroviral vector appears to hold the greatest promise, with transgenic primates already obtained from this approach. Sperm-mediated gene transfer offers potentially the easiest route to the human germline, however the requisite methodology is presently underdeveloped. Nuclear transfer (cloning) offers an alternative approach to germline genetic modification, however there are major health concerns associated with current nuclear transfer methods. It is concluded that human germline gene therapy remains for all practical purposes a future possibility that must await significant and important advances in gene transfer technology.