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Regular Article |
b INRA, Biologie du Développement et Biotechnologies, 78 352 Jouy en Josas, France
c UNCEIA, Services Techniques, 94 703 Maisons-Alfort, France
d INRA, Physiologie Animale, 78 352 Jouy en Josas, France
e INA-PG, 1 rue Cl. Bernard, 75231 Paris, France
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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assisted reproductive technology, conceptus, embryo, placenta, pregnancy
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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These long-lasting effects of cloning are associated with excessive accumulation of allantoic fluid and increased fetal or birth weight [4, 13, 14]. This syndrome is similar to large offspring syndrome (LOS), which has been reported previously for in vitro-derived blastocysts in sheep and cattle [15, 16]. LOS is related to in vitro culture conditions of embryos before their transfer to recipient females [17] and/or to adverse effects associated with exposure of normally grown embryos to an advanced uterine environment [18]. This raises the question of whether the high incidence of late gestation losses in pregnancy after cloning is mainly due to in vitro culture conditions or to associated reprogramming effects of the reconstructed embryos by nuclear transfer.
Several cases of pathologic placentation during pregnancy after somatic cloning have been described. Transfer of blastocysts derived from adult mural granulosa cells by Wells et al. [4] has resulted in the loss of fetuses in the third trimester of pregnancy, due to an excessive accumulation of allantoic fluid. In a preliminary report, we observed three cases of recipients developing hydroallantois (grossly abnormal abdominal distension) from 6 mo to the end of gestation out of 20 recipients that carried cloned embryos that were derived from fetal or adult fibroblasts [13]. However, we had previously observed that the incidence of late abortion was relatively low (10%) in our laboratory after embryonic cloning, and that LOS was limited to 3% of the calves born [19]. We have now extended these preliminary observations by comparing the incidence of late-gestational effects resulting from the transfer of embryonic or somatic cloned embryos cultured up to the blastocyst stage under similar conditions.
To monitor the evolution of pregnancies up to parturition, we combined different methods to check placental and fetal normality or abnormality. Such information is important because the different organs of the fetus are already formed by that time and should be growing, as was described many years ago by bovine embryologists [20, 21]. Repeated ultrasonography has been used to evaluate fetal growth in horses from 100 days of gestation to parturition [22], but this technique has to be adapted to the bovine species, in which visualization of the fetus is more difficult by the rectal route after 3 mo of pregnancy. Placental development can also be evaluated by maternal levels of pregnancy proteins such as pregnancy-specific protein B [23], pregnancy-associated glycoprotein [24], and pregnancy serum protein 60 (PSP60), a protein of 60 kDa [25]. Except for some biochemical differences, these proteins are similar. PSP60, which is secreted by the binucleated cells of the placenta, is a specific marker of pregnancy in cattle and is easily assayed from a blood sample of the dam [25].
Late losses have a serious economic effect on the cost of generating cloned offspring because recipients have to be kept under controlled conditions for several months without a final result. They also expose the recipients to conditions that threaten their welfare. The possibility of predicting the occurrence of a pathologic evolution of pregnancy, by combined use of ultrasonography and pregnancy-specific protein assays on the recipient, would be very useful for the better care and management of the recipients in order to improve their welfare. We therefore examined the possibility of using PSP60 measurements as an early predictor of late gestation failure.
The objectives of this study were 1) to follow the evolution of pregnancy after somatic cloning in order to detect the occurrence of fetal loss and its frequency compared with embryo cloning or IVF and 2) to establish accurate criteria for predicting abnormal fetal or placental growth during late pregnancy.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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All the blastocysts transferred to recipients were produced in vitro through embryo or somatic nuclear transfer; control embryos were derived through IVF.
Oocyte preparation Bovine ovaries were collected from two different abattoirs, washed several times with fresh saline solution, and then transported in sterile PBS at 33°C to the laboratory within 3 h of collection. Cumulus oocyte complexes (COCs) were aspirated from follicles 2–6 mm in diameter, washed in HEPES-buffered TCM-199, and selected on the basis of their morphology for in vitro maturation according to the density of their cumulus cell layers. For in vitro maturation, groups of 30–40 COCs were incubated in TCM 199 (Life Technologies, Paisley, Scotland) supplemented with 10% (v/v) fetal calf serum, 10 µg FSH ml-1 (Stimufol, Merial, Lyon, France), and 1 µg LH ml-1 for 22 h at 39°C in a humidified atmosphere of 5% CO2 and air. At the end of the maturation period, oocytes from the same batch were used either to provide a recipient cytoplast for cloning or for IVF (i.e., the IVF embryo control group).
Embryo nuclear transfer Embryo cloning was performed as previously described by our laboratory [26]. Briefly, in vitro-matured oocytes had all their cumulus cells removed by gentle pipetting after exposure to TCM 199 supplemented with 0.5% (w/v) hyaluronidase (Sigma Chemical Co., St. Louis, MO) for 10 min. Oocytes were incubated in TCM 199 supplemented with 0.5 µg Hoechst 33342 ml-1 (bisbenzimide, Sigma) for 20 min in order to stain chromatin, and were then enucleated by micromanipulation under an inverted microscope (Olympus IMT2) equipped with epifluorescence and an intensified camera (LHESA, France). The efficiency of enucleation was directly checked by controlling the presence of the metaphase plate and polar body in the enucleation pipette. For embryo cloning, cytoplasts were preactivated by aging and cooling prior to fusion with blastomeres isolated from Day 6 in vivo-produced or in vitro-produced morulae of the Holstein breed. Fusion was achieved by electrostimulation (Grass stimulator, 1.3 kV for 50 µsec in 0.3 M mannitol solution) [27].
Somatic nuclear transfer For somatic cloning, donor cells were cultured over several passages (3 to 12) from fetal or adult skin biopsies processed as previously described [3] on five genotypes. The fibroblasts were grown in 60-mm Petri dishes in order to obtain either a growing or a quiescent population of cells on the day of nuclear transfer. Just before nuclear transfer, the cells were mechanically scraped, pelleted at 1200 x g for 5 min, and resuspended in fresh TCM 199. Each isolated cell was inserted under the zona pellucida of the recipient cytoplast and fused by electrostimulation [3].
In vitro development of nuclear transfer embryos All the reconstituted embryos from embryonic or somatic cells were cultured under the same conditions (i.e., in microdrops of 50 µl B2 medium [CCD, Paris, France] supplemented with 2.5% fetal calf serum and seeded with Vero cells according to the culture system used in our laboratory for bovine IVF embryos) [28]. The droplets were overlaid with mineral oil (M8410 Sigma Co., St. Louis, MO) and incubated for 7 days at 39°C under 5% CO2. Cleavage was assessed at Day 2 after fusion and blastocyst formation was evaluated at Day 7. Expanding or early hatching blastocysts (grades 1 and 2) by Day 7 were removed from the culture drops and used for transfer to recipient heifers.
Control IVF embryos Control groups of IVF embryos were obtained from the same batches of in vitro-matured oocytes. Twenty-four hours after onset of maturation, oocytes were coincubated with heparin-capacitated frozen-thawed spermatozoa in Tyrode albumin lactate pyruvate medium for 18 h according to the standard technique routinely used in the laboratory [29]. A single batch of frozen sperm from the same Holstein bull was used throughout the experiment to produce the control embryos. After IVF, presumptive zygotes were cultured until Day 7 under the same conditions as nuclear transfer embryos. By Day 7, blastocysts of grades 1 and 2 quality were used for transfer to recipients.
Embryo Transfer
Animals Recipient animals were beef-breed Charolais or cross-bred heifers raised under the same conditions and transported to the experimental farm by the age of 12–14 mo. They were certified free of all major infectious cattle diseases by repeated serological testing prior to transport. They were then checked for normal cyclicity before being used as recipients for embryo transfer by the age of 15–18 mo.
Estrous cycles were synchronized in each group of recipients using a progestagen implant for 9 days (Crestar Intervet) associated with a prostaglandin analogue injection (2 ml Estrumate) 2 days before implant removal. After estrus detection, heifers that were synchronous ± 24 h with embryo age and carrying a palpable corpus luteum were selected for embryo transfer.
Day 7 blastocysts that were developed in vitro after nuclear transfer or IVF had the same age at time of transfer (Day 0 being the time of fertilization or nuclear transfer). They were loaded into 0.25-ml straws (IMV, L'Aigle, France), one embryo per straw, and transported in a thermos flask at 39°C from the laboratory to the experimental farm. Embryo transfer was performed nonsurgically into the uterine horn ipsilateral to the corpus luteum (single transfer) using the miniaturized embryo transfer syringe and sheath (IMV) under slight epidural anesthesia.
Pregnancy Monitoring
Plasma progesterone assay A heparinized blood sample was taken at Day 21 (2 wk after transfer) from each recipient by venipuncture of the caudal vein and centrifuged immediately. Plasma was separated and frozen before being assayed for a rapid estimation of progesterone concentration by radioimmunoassay. Recipients were considered nonpregnant if progesterone concentration by Day 21 was <1 ng/ml and presumed pregnant when concentration was >2 ng/ml.
PSP60 assay Concentrations of PSP60 were measured in the peripheral blood of recipients from frozen plasma samples stored after monthly blood venipuncture by radioimmunoassay as described by Mialon et al. [25]. Sensitivity of the PSP60 assay was 0.2 ng/ml plasma, and intraassay and interassay coefficients of variation were 6% and 12%, respectively. The cutoff minimum/maximum levels were 0.2 and 6.2 ng/ml. For higher concentrations in late gestation, plasma samples were diluted accordingly. The PSP60 levels in recipients that became pregnant from embryonic or somatic clones were compared with those of a group of control animals that became pregnant after artificial insemination in order to evaluate whether this measurement can be a predictive criterion for detecting abnormal development of placenta in cloned fetuses.
Ultrasonography All recipients were examined for the presence or absence of a viable fetus at Day 35 ± 2 days using transrectal ultrasonography (Pie medical ultrasound equipped with a 5.0 MHz probe). Pregnant recipients were then repeatedly checked on Days 50, 70, and 90 of pregnancy.
From Day 120 of pregnancy, recipients carrying a somatic clone fetus or a control fetus were submitted to repeated transabdominal ultrasonography using a 3.5 MHz probe, every 2 wk until calving. The viability of the fetus as well as the ultrasonographic aspect of the placenta were thus monitored. Contemporary pregnant heifers (through artificial insemination) of the same breed were used as controls and to establish a normal range (n = 13). Fetal heartbeat was recorded and the aortic diameter was measured just outside the heart as described in other species [30, 31] as a possible criterion for oversize. For placental evaluation, the size of placentomes was estimated by measuring the surface on the screen at their maximal size. We measured in each recipient the size of four placentomes localized in the same ventral area close to the udder. Because no reference values exist, we established these reference values on control animals at the same stages of gestation. Qualitative aspects (visualization or absence of edema estimated by contrast levels of tissues on the screen) were also recorded.
Transabdominal ultrasonography was performed in order to detect any pathologic evolution of pregnancy such as abnormal fetal growth (aortic diameter), fetal stress, or hypoxia (heartbeat). Placental abnormalities or severe hydroallantois was detected by an increase in fluids associated with difficulty in locating the fetus in the uterine cavity. It was accompanied by a progressive deterioration of the clinical status of the recipient (loss of appetite, body condition). When several criteria from at least two successive ultrasound examinations confirmed that the pregnancy was abnormal, the pregnant recipient was humanely killed before her clinical status became critical, and the uterus and the fetus were recovered for examination.
Calving
Pregnant recipients were kept until calving. Cloned calves were delivered by cesarean delivery following maternal treatment with 20 mg dexamethasone (Dexadreson) i.m., 36 h before surgery, when natural calving had not occurred by Day 282 of pregnancy. Calving was scored according to the ease of delivery (from 1 = no assistance, to 4 = cesarean delivery). Newborn calves were given colostrum within 2 h after calving, and birth weight, sex, and the length of gestation were recorded for each group of in vitro-produced embryos. LOS was considered to occur when birth weight was higher than the mean birth weight plus two standard deviations within the same herd [31]. Calves were isolated and followed up to the age of 2 mo.
Experimental Design and Statistical Analysis
Evolution of pregnancy rates was followed on four groups of recipient animals over a 3-yr period. For each group, at least part of the transfers were contemporary with the other groups:
Placentome size, fetal heartbeat, and aortic diameter were measured by ultrasound, comparing pregnant recipients in groups 1 and 2 (somatic cloning, n = 21) and normal pregnancies in a control group of animals that became pregnant through artificial insemination (n = 13). For each gestational period, the Student t-test was used.
PSP60 assays were performed on some of the recipients in groups 1 and 2 (somatic cloning, n = 30) and group 3 (embryo cloning, n = 22). For each stage of pregnancy, values were averaged for recipients that developed pathologic pregnancies after somatic cloning. Reference values for PSP60 levels in normal pregnancies were obtained from a monthly sampling of a group of 11 contemporary cows that became pregnant through artificial insemination.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Pregnancy results for the four groups of recipients are presented in Table 1. Transfer of IVF embryos, embryo clones, and fetal or adult somatic clones resulted in the same range of initiated pregnancy rates (55.6%–62.7%). However, evolution of pregnancy rates was quite different between groups. Confirmed pregnancy rate by Day 35 assessed by ultrasonographic scanning was significantly lower in group 1 (somatic adult, 33.8%) and group 2 (somatic fetal, 27.5%) compared with the controls, group 4 (IVF; 52.9%; P < 0.01). At Days 50–90, pregnancy rates were confirmed to be significantly lower in groups 1 and 2 than in groups 3 or 4 (P < 0.05).
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Placental and fetal development in pregnant recipients after somatic cloning was monitored using repeated scanning on the same animals every 2 wk from the fourth month of pregnancy until calving, in order to detect any pathologic evolution. Placentome sizes were recorded from 21 recipients that were pregnant from somatic clones, and compared with those of 13 control animals (artificial insemination). Results presented in Figure 1 indicate that in recipients that carried somatic clones, the mean size of placentomes between 4 and 6 mo was significantly higher than in control pregnancies, regardless of the outcome of pregnancy. There was a linear regression between placentome size and stage of pregnancy in clones and controls (r2 = 0.84 for clones, P < 0.01; and r2 = 0.69 for controls, P < 0.05).
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Fetal heartbeat was recorded every 2 wk in clones and control fetuses. No significant differences were observed. Whatever the pregnancy stage, frequency of heartbeat was >100 per min. There was a slight tendency toward decreasing frequency by the end of pregnancy. By Day 262, heartbeat was 116 ± 11.9 per min, and 100.5 ± 14.8 per min for somatic clone and control fetuses, respectively. Scanning was also used to measure the aortic diameter in clone and control fetuses. Evolution of aortic diameter was not significantly different between clone and control fetuses. There was, however, also a significant correlation between gestational age and aortic diameter in clones (r2 = 0.60) and in controls (r2 = 0.62).
Frequency of Late Fetal Losses
The proportion of late-gestation losses between Day 90 and calving reached 43.7% in recipients carrying adult somatic clones and 33.3% for fetal somatic clones, whereas only 4.3% of the pregnancies were lost during the same period after embryo cloning, and no late loss was detected in the control IVF group (Table 2).
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Using repeated scanning on 21 recipients carrying somatic clone fetuses, 5 cases of late abnormal pregnancies were detected, and recipients were killed between Days 155 and 233 of gestation. In both cases severe hydroallantois was confirmed at autopsy and the size of placentomes was measured after dissection of the uterus. Mean placentome weight was 142.3 ± 61.7 g compared with 46.7 ± 22.7 g for placentomes in three cases of normal pregnancy at the same stage. Severe hydroallantois was often associated with fetal abnormalities (Table 3); three fetuses presented LOS and one was completely hydropic.
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PSP60 Profiles and Late Losses
PSP60 concentrations were measured on blood samples from recipients between Day 35 and calving. During the first trimester of pregnancy (Fig. 2, a and b), PSP60 concentrations increased from Day 35 to Day 90 in recipients that were confirmed pregnant at 3 mo and, for each stage of pregnancy (Day 50, 70, or 90) there were no significant differences in the mean levels of PSP60 concentrations between groups that further developed to full-term pregnancy. However, for recipients of the somatic clone group, which subsequently lost their pregnancy as detected by ultrasound scanning (Fig. 2a), we found a significantly higher level of PSP60 by Day 50 than for those that maintained pregnancy (7.77 ± 3.3 ng/ml vs. 2.45 ± 0.27 ng/ml for normal pregnancies, P < 0.05). These higher levels were detected at Day 50 even though pregnancies were lost before Day 100 in these animals. Moreover, PSP60 levels over 4 mo of pregnancy appeared to be significantly increased in animals in which pathologic pregnancy was detected by ultrasonography in late gestation (Fig. 2c). This was true only for somatic cloning compared with other groups (P < 0.05 by Day 150, P < 0.001 by Day 180, and P < 0.01 by Day 210). In those situations, the plasma PSP60 concentrations in recipients that developed severe hydroallantois were very high, up to 400 ng/ml by Day 180 of pregnancy, when levels in other groups were less than 100 ng/ml at the same stage. No significant difference was observed in the PSP60 concentrations in recipients that delivered live, full-term calves after embryo or somatic cloning compared with the control group.
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Calving and Postnatal Survival
Proportions of calves born differed significantly between groups (6.8% in group 1 [adult somatic cloning], 15.0% in group 2 [fetal somatic cloning], and 34.3% in group 3 [embryo cloning], respectively, compared with 49.0% in the controls, group 4 [IVF], P < 0.01).
Information on calves born, birth weight, length of gestation, and postnatal survival for the different groups are given in Table 4. Mean birth weight of adult somatic cloned calves was significantly higher than that of control IVF calves (53.1 ± 2.0 kg compared with 44.5 ± 2.1 kg for IVF calves, P < 0.05). Calving score was higher for recipients carrying somatic clones due to the high proportion of cesarean deliveries performed in these groups. Postnatal survival of live-born calves was satisfactory (>80% survival after 1 mo) for three groups (control IVF, embryo clones, and somatic fetal clones). Calves born from adult somatic cloning had a lower survival rate; 33% (3 of 9) died during the first week but 6 of 9 were alive after 1 mo and developed normally.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Maternal secretion of pregnancy-specific proteins is generally used as a simple pregnancy test in cattle [23, 24]. Our objective in measuring PSP60 levels was also to try to find a predictive criterion for normal/abnormal pregnancy. We observed that an abnormal gestation outcome in recipients that carried embryonic or somatic clones was linked to high levels of PSP60 in the blood. The PSP60 protein is secreted by the binucleated cells in the fetal cotyledons and can be detected in maternal blood. The circulating level of pregnancy-specific protein has been used as a criterion to discriminate between single and twin pregnancies after artificial insemination or embryo transfer in cattle [33]. The levels of PSP60, if significantly increased, could be a good indicator of abnormal placenta development in some of the recipients that carried somatic clones. This was observed as early as Day 50 in recipients that later lost their fetus after somatic cloning, as the level of PSP60 was significantly increased in such recipients. Hill et al. [12] reported that pregnancy-specific protein b was higher at Day 35 in the pregnancies that failed by Day 90. By Days 150 and 180 of pregnancy, mean levels of PSP60 were also significantly higher in recipients that carried somatic clones and developed pathologic pregnancies, which suggests an overactive placental secretion of this glycoprotein. This was further confirmed by scanning measurements of placentome sizes, which were significantly larger in the five recipients of this somatic clone group that clearly developed hydroallantois. Autopsy of these recipients after slaughter confirmed the occurrence of this placental pathology in all cases. Postmortem dissection of the recipient uterus showed the presence of large-size hydropic cotyledons, some of which weighed up to 0.5 kg. This observation is in agreement with the high level of PSP60 detected. The fact that recipients that developed pathological pregnancy showed an increase in PSP60 levels about 1 mo earlier than recipients that carried normal pregnancies can be used to detect an overactive placenta. This is in accordance with recent observations by Farin et al. [34], who indicated that at 63 days following embryo transfer, bovine placentas from embryos produced in vitro had increased volume densities of binucleate cells compared with placentas from embryos produced in vivo. Further studies on morphometry and histology of the bovine pathologic placenta recovered at later stages of pregnancy after somatic cloning are underway in our laboratory and will presumably give an explanation of the increased levels of PSP60 that we have observed.
Increased incidence of late hydroallantois as well as increased mean birth weight of calves derived from somatic cloning could be related to inappropriate expression of some imprinted genes [35]. In humans, it is known that overexpression of insulin-like growth factor 2 (IGF2) by loss of imprinting induces the Beckwith-Wiedeman syndrome, which is characterized by a large-size baby at birth, macroglossia, and polyhydramnios [36]. In our laboratory, preliminary assays suggest that the plasma concentration of IGFs and IGF binding proteins differ between neonatal clones and control calves [37]. These findings may be the consequence of abnormal growth and placental development in fetal life. In a recent study by Blondin et al. [38], it was shown that bovine fetuses originating from in vitro production systems possess altered levels of IGF mRNA in both liver and skeletal muscle. From our observations on somatic cloned fetuses recovered at slaughter after detection of hydroallantois, enlarged liver (up to 7% of body weight) was one of the characteristics of these fetuses (data not shown). Observed abnormalities may be the consequence of deregulation of imprinted genes such as IGF receptor 2, which has recently been shown to be associated with fetal overgrowth in sheep [39].
Full-term development rates after fetal or adult somatic cloning were 15% and 6.8%, respectively, and were significantly lower than in the control group after transfer of IVF embryos in the same experimental farm. These rates are comparable to those already published for somatic cloning using fetal or adult skin fibroblasts as the source of cells [5, 40].
By the time of embryo transfer, the quality of the blastocysts as evaluated by their morphology (grades 1 and 2) was similar for the different groups, and all of them were developed in vitro under the same culture conditions [28]. Total cell counts on Day 7 blastocysts derived from embryo cloning and somatic cloning were not different from those of control IVF blastocysts. However, the proportion of inner cell mass cells was lower in somatic cloned blastocysts [41]. This means that these four groups of in vitro-produced blastocysts of similar morphological grading can have very different potential for full-term development, although the initiated pregnancy rate as assessed by progesterone level on Day 21 is similar.
At birth, the incidence of LOS seemed to be higher for somatic clones than for embryonic clones or IVF calves. If we consider that LOS occurs when birth weight is higher than the mean birth weight plus two standard deviations, then calves weighing more than 59.5 kg at birth were considered to be large calves. The incidence of LOS at birth was 13.3% for somatic cloning, compared with 8.6% for embryonic cloning and 9.5% for the group of IVF calves. This proportion is somewhat lower than the 14.4% of calves exceeding 60 kg reported on a larger scale after in vitro embryo production [15]. After somatic cloning, the incidence of LOS could be related to the source of donor cells. According to Kato et al. [11], when donor cells were derived from cumulus and oviduct, calf body weights at birth were in the normal range, but when calves were derived from skin, ear, or liver donor cells, they observed a 47% rate of LOS (9 cases out of 19 calves born). Under our conditions, with a similar source of cells (fibroblasts derived from ear skin biopsy), our proportion of large calves was very limited (13.3%) compared with other reports. However, the maximal birth weight of our calves born in the different groups was 62 kg, and the occurrence of these large calves had no incidence on postnatal survival except for group 1, in which three calves out of nine did not survive longer than 2 mo. Postnatal survival of calves in group 1 (adult somatic clones) was lower than in all other groups, whereas the total number of animals is still limited. After embryo cloning and fetal somatic cloning, survival rates longer than 1 mo were high (>80%) and not different from those obtained for IVF calves. This is much higher than survival rates reported for embryo clones in cattle. Lewis et al. [42] reported 13 healthy calves at 2 mo from 22 full-term fetuses (60% survival), but in his experiment, twinning could have contributed to poor survival, which was not the case in the present study because only single transfers were performed. In the group of adult somatic clones, one animal died at the age of 2 mo from a thymic hypoplasia [43]. The five remaining animals are healthy and normal. Some of the females are more than 1 yr old and are cycling normally. The five animals in the group of fetal somatic clones are still alive and show no pathological manifestation. Among them, two males are already adult and have proved to be fertile. Sperm has been collected and frozen from these two bulls and is now routinely used in an IVF research program. However, according to Institut National de la Recherche Agronomique regulations, animals derived from cloning may not enter the human food chain and must be killed at the end of the experiment. This will be the case for animals in this experiment when all measurements have been made at the adult stage.
In conclusion, our experiments suggest that maternal PSP60 assays can be a good predictor of abnormal fetal development after somatic cloning in cattle, and that somatic cloning from adult cells induces higher levels of abnormalities and late losses than embryo cloning.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Correspondence. FAX 33 1 34 65 26 77; heyman{at}biotec.jouy.inra.fr 
Accepted: August 9, 2001.
Received: May 22, 2001.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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|
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O. V. Patel, O. Yamada, K. Kizaki, T. Takahashi, K. Imai, S. Takahashi, Y. Izaike, L. A. Schuler, T. Takezawa, and K. Hashizume Expression of Trophoblast Cell-Specific Pregnancy-Related Genes in SomaticCell-Cloned Bovine Pregnancies Biol Reprod, April 1, 2004; 70(4): 1114 - 1120. [Abstract] [Full Text] [PDF]
|
|
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|
 |
|
 L. J. Mullins, I. Wilmut, and J. J. Mullins Nuclear transfer in rodents J. Physiol., January 1, 2004; 554(1): 4 - 12. [Abstract] [Full Text] [PDF]
|
|
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|
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R. S.F. Lee, A. J. Peterson, M. J. Donnison, S. Ravelich, A. M. Ledgard, N. Li, J. E. Oliver, A. L. Miller, F. C. Tucker, B. Breier, et al. Cloned Cattle Fetuses with the Same Nuclear Genetics Are More Variable Than Contemporary Half-Siblings Resulting from Artificial Insemination and Exhibit Fetal and Placental Growth Deregulation Even in the First Trimester Biol Reprod, January 1, 2004; 70(1): 1 - 11. [Abstract] [Full Text] [PDF]
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 S. Schutt, A. R. Florl, W. Shi, M. Hemberger, A. Orth, S. Otto, W. A. Schulz, and R. H. Fundele DNA Methylation in Placentas of Interspecies Mouse Hybrids Genetics, September 1, 2003; 165(1): 223 - 228. [Abstract] [Full Text] [PDF]
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