TNF receptor II fusion protein with tandemly repeated Fc domains

The extracellular domain of tumour necrosis factor (TNF) receptor II fused with the human IgG1 Fc region (TNFRII-Fc), as well as antibodies against TNF, has been used to treat rheumatoid arthritis. However, TNFRII-Fc is less effective than these antibodies in terms of antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) against cells bearing TNF on the cell surface. We hypothesized that these activities could be increased by fusing TNFRII with tandemly repeated Fc (TNFRII-Fc-Fc). The affinities of TNFRII-Fc-Fc for soluble TNF-α and transmembrane TNF-α and the TNF-α cytotoxicity-inhibitory activity were as potent as those of TNFRII-Fc. TNFRII-Fc-Fc showed much higher binding avidity for Fcγ receptors than TNFRII-Fc and was more potent in terms of both ADCC and CDC against cells expressing transmembrane TNF-α. TNFRII-Fc-Fc of 80 kDa, as well as TNFRII-Fc-Fc of 200 kDa, was detected. TNFRII-Fc-Fc (80 kDa) was as potent as TNFRII-Fc in terms of both ADCC and CDC. These results suggest that Fc multimerization of receptor-Fc fusion proteins can augment effector functions such as ADCC and CDC, and thereby have the potential to provide a superior therapeutic effect. This may be the case not only for TNFRII-Fc but also for other receptor-Fc fusion proteins.

42 LARGE-SCALE PRODUCTION OF CLONED TRANSGENIC PIGS: EFFICIENCY AND SIDE EFFECTS

Generation of transgenic pigs by somatic cell nuclear transfer (SCNT) has provided a new avenue for medical research. However, low efficiency of SCNT greatly hinders its practical applications. In this study we evaluated the efficiency of producing cloned transgenic pigs as well as the side effects of cloning observed in several piglets. As nuclear donors, we used 31 different cell cultures of porcine fetal fibroblasts, kidney cells, or skin fibroblasts derived from commercial breeds. Donor cells were modified by additive gene transfer or knockout with 21 different gene constructs or genes of interest. For additive gene transfer, a mixed cell population without previous expression analysis was used. For re-cloning, kidney or skin fibroblasts from cloned transgenic pigs were used. SCNT was performed using in vitro matured oocytes as previously reported (Kurome et al. 2006 Transgenic Res. 15, 229–240). Reconstructed oocytes were transferred laparoscopically to oestrus synchronized recipient gilts. After transfer of 9317 reconstructed oocytes into 112 recipients, 58% of recipients became pregnant and 42% of them gave birth to offspring. Birth was induced by injection of a PGF2α-analogon. Out of 159 cloned piglets, 65 (40%) were clinically healthy and developed further normally, whereas 35 (22%) cloned piglets were stillborn and 46 (30%) died soon after birth. The major reason of early neonatal death was severe underweight (<700 g), which has been found in 26 cases of several cloned litters. In rare cases, we also observed malformations like oversized tongue, cleft palate, or atresia ani. Thirteen piglets were lost because of other circumstances (killed by mother or infectious disease). The in vivo developmental competence of donor cells was analysed regarding the effects of genomic modification and re-cloning. Interestingly, we did not find significant differences in the pregnancy and delivery rates when using transfected and non-transfected cells. While the litter size from transfected cells was slightly smaller compared with non-transfected cells, the ratio of piglets per litter which survived the critical neonatal age was similar, namely 1.8 from transfected and 2.0 from non-transfected cells. Compared to the data from cloning, re-cloning resulted in lower pregnancy and delivery rates. Furthermore, efficiency with respect to the litter size or the number of clinically healthy piglets was significantly lower, as we obtained only 6 piglets from 4 pregnancies and 5 of them died at the neonatal age. In conclusion, cloned transgenic pigs were produced with several types of donor cells and genetic modifications. Nearly half of them showed abnormalities, which were not associated with the type of donor cells or the transgene used. Cloning efficiency was not affected by the procedure of genomic modification but was negatively influenced by re-cloning probably because of epigenetic alterations in the genome of donor cells. Supported by the DFG (FOR535, FOR793), by the Bayerische Forschungsstiftung, and by Mukoviszidose e.V.

338 BACTERIAL ARTIFICIAL CHROMOSOME (BAC) VECTORS FACILITATE EFFICIENT GENE TARGETTING IN KIDNEY CELLS OF PIG

Site-directed mutagenesis provided a powerful tool for studying gene functions in mice, but the lack of embryonic stem cells in other species limited the application of this technology to other species. Various attempts using negative selection, viral vectors, or other auxiliary means promoted specific projects but did not provide methods for routine experiments. Here, we describe a novel approach that enabled the site-directed modification of 3 different porcine genes relevant for biomedical research. Three main technologies were combined to achieve these goals: bacterial artificial chromosome (BAC) vectors, somatic cell transfection, and nuclear transfer (SCNT). BAC vectors contain large genomic regions in bacterial plasmids. They are superior to conventional targeting tools, as they provide extended regions of homology of several kilobases. Novel recombination tools using bacterial enzymes enable the modification of any DNA region of interest and thus allow the introduction of desired mutations into BACs. After verification of the wt-BAC sequence, it was altered by using modification vectors carrying the desired mutation. The modified BAC vectors are linearized and transfected after verification into primary kidney cell lines, and cells are selected for integration of the vectors. Kidney cells provide both good proliferation and high targeting rates, and thus improve the efficiency compared to fetal fibroblasts. Singularized clones are screened for the replacement of wild-type targeting loci by quantitative PCR. Targeted clones are used for SCNT and transfer of the resulting embryos into synchronized gilts. We have evaluated this technology by the modification of the porcine CFTR, GGTA1, and DMD genes. All 3 genes are relevant for biomedical research, as mutations in CFTR are causative for cystic fibrosis, the knockout of GGTA1 is essential for overcoming hyperacute rejection in xenotransplantation, and various deletions in the DMD gene are responsible for Duchenne muscular dystrophy. Gaining 13 targeted clones out of 1152 for CFTR, 9 out of 306 for GGTA1 and 6 out of 203 for DMD, we obtained efficiencies higher than 1% for each of the target genes. The power of our approach is underlined by the fact that CFTR and DMD are loci that are thought to be difficult to manipulate. The viability of targeted kidney cells and their suitability for nuclear transfer is accentuated by the pregnancy rates (2 out of 3) and the delivery of 4 to 10 piglets or fetuses in the case of CFTR and GGTA1. The heterozygous fetuses or piglets are verified by qPCR. In the case of the X-chromosomal DMD gene, we have generated the first full knockout by transfecting male cells. Pregnancies of a successfully targeted clone are under way. Thus, we consider the combination of modified BAC vectors, transfection of kidney cells, and nuclear transfer to be a technology with the potential for routine production of site-directed mutations. Supported by the Mukoviszidose e.V. and the Bayerische Forschungsstiftung.

192 INDUCIBLE TRANSGENE EXPRESSION IN PIGS

Genetically modified pigs are important models for biomedical research. For certain applications, tightly controlled transgene expression is mandatory. For instance, expression of soluble receptor activator of the NFκB ligand (RANKL) is an established principle for inducing clinically relevant osteoporosis (Mizuno et al. 2002 J. Bone Miner. Metab. 20, 337–344). However, constitutive overexpression of RANKL is lethal; thus, an inducible system is required. A second example is the expression of porcine CTLA-4Ig to prevent co-stimulation of T-cells in pig-to-primate xenotransplantation. Because constitutive expression of porcine CTLA-4Ig causes immunosuppression in pigs (Phelps et al. 2009 Xenotransplantation 16, 477–485), an inducible expression system is desirable. The Tet-On system is used most widely. It is based on a tetracycline transactivator (TA) and a transactivator response element (TARE), which drives expression of the coding sequence for the transgene product of choice. Association of doxycyclin with TA allows binding to TARE, resulting in activation of transgene expression. Although widely used in mice, this system has not yet been established in pigs. Because consistently high expression of TA is required for a functional system, we first cloned an expression vector for TA under the control of the CMV enhancer/chicken β-actin promoter (CAG). A floxed neomycin resistance cassette was linked to this vector to facilitate selection of stable clones after transfection of primary porcine kidney cells. The latter were used for nuclear transfer, and cloned embryos were transferred to synchronized recipient gilts, resulting in the birth of 5 CAG-TA transgenic piglets. A spectrum of organs and tissues was investigated by RT-PCR and Western blot for TA mRNA and protein expression. Primary kidney cells from all 5 TA transgenic piglets were transfected with TARE-RANKL and TARE-CTLA-4Ig constructs linked with a blasticidin resistance cassette to facilitate selection of double transgenic/transfected cell clones. These cell clones were individually stimulated with doxycyclin to identify cell clones with low background and high inducibility of expression of RANKL or CTLA-4Ig. For both combinations, several clones meeting these criteria were identified. Such cell clones were used for nuclear transfer to produce double-transgenic pigs. Application of doxycyclin (25 to 50 mg kg–1 of body weight/day) to a TA/TARE-RANKL transgenic pig resulted in a marked increase in plasma RANKL concentrations. In addition, 4 TA/TARE-CTLA-4Ig transgenic piglets have been born, which will undergo doxycyclin stimulation experiments in the near future. In summary, CAG-TA transgenic pigs serve as a reliable basis for inducible transgene expression, as shown in the present study for RANKL and CTLA-4Ig. Studies to show the biological functionality of the transgene are currently underway. Supported by DFG (FOR793) and BFS (FORZebRA).

Effect of immunoglobulin G (IgG) interchain disulfide bond cleavage on efficacy of intravenous immunoglobulin for immune thrombocytopenic purpura (ITP)

Intravenous immunoglobulin (IVIG) has been used widely to treat immune thrombocytopenic purpura (ITP), but the mechanisms of its action remain unclear. We investigated the affinity for Fcγ receptors (FcγRs) and the thrombocytopenia-ameliorating effect of S-sulfonated gammaglobulin (SGG) and S-alkylated gammaglobulin (AGG), in comparison with unmodified gammaglobulin (GG), in a mouse ITP model. Cleavage of immunoglobulin (Ig)G interchain disulfide bonds by either S-sulfonation or S-alkylation did not decrease the affinity for FcγRIIA (CD32A) and FcγRIIB (CD32B), but did decrease the affinity for FcγRIA (CD64A) and FcγRIIIA (CD16A), presumably because of changes in H-chain configuration. The interchain disulfide bond cleavage decreased the affinity much more for mouse FcγRIV than for mouse FcγRIIB. The ability of AGG to ameliorate ITP was greatly diminished, while SGG, whose disulfide bonds are reconstituted in vivo, was as effective as GG. These results suggest that the interchain disulfide bonds are important for therapeutic effect. It is also suggested that the interaction of IVIG with the inhibitory receptor FcγRIIB is insufficient for effective amelioration of ITP and that, at least in this model, direct binding of IVIG to FcγRIIIA is also required.

Severe rotational deformity, quadriparesis and respiratory embarrassment due to osteomyelitis at the occipito-atlantoaxial junction

We present the case of an 83-year-old man who developed quadriparesis and respiratory embarrassment following osteomyelitis at the occipito-atlantoaxial junction. He had developed an abscess at this site after an earlier urinary infection with methicillin-resistant staphylococcus aureus. Stabilisation of the neck and antibiotic therapy led to an almost complete neurological recovery without recourse to anterior surgery.

[Enhancement of antibody-dependent cellular cytotoxicity by tandem Fc multimerization]

Monoclonal antibodies are being used as therapeutics for a number of cancers, such as leukemia, breast and colon cancers, and a lot of monoclonal antibodies specific for tumor-related antigens have been on clinical trials. Antibody-dependent cellular cytotoxicity (ADCC) is one of the major mechanisms by which antibodies exert anti-tumor effects. ADCC occurs through interaction between the Fc domains of IgG antibodies bound to target cells and Fcgamma receptors on the surface of effector cells. In our study, a chimeric antibody, designated M-Ab, was constructed with the V regions from mouse anti-CD20 mAb 1F5 and the C regions from human IgG1 and kappa chain. Two or three Fc domains were tandemly repeated downstream of the C-terminus of the M-Ab to give D0-Ab (Fc dimer Ab without a linker), T0-Ab (Fc trimer Ab without a linker), and T3-Ab (Fc trimer Ab with a (GGGGS)(3) linker in front of the second and third hinge regions). Here, we show that Fc tandem repeat antibodies bind to all the low-affinity Fcgamma receptors with very potent avidities and have greatly enhanced ADCC activity. T3-Ab is about 100 times more potent than the parental 1F5 chimeric antibody in terms of both Fcgamma receptor binding and exerted ADCC activity at a 50-100 times less concentration as compared with the parental antibody. Thus, Fc tandem repeat antibodies are anticipated to be candidates for anti-tumor therapeutics and useful tools to elucidate the biological roles of Fcgamma receptors.

425 HIGH-LEVEL EXPRESSION OF LEA29Y IN PANCREATIC ISLETS OF TRANSGENIC PIGS

Among the candidate organs or tissues for pig-to-primate xenotransplantation, pancreatic islets are probably closest to clinical application. Rejection of islet xenografts occurs mainly by cellular mechanisms; that is, T cells. A candidate molecule to protect porcine islets against the attack by human T cells is CTLA-4Ig, which represents the T-cell-inactivating extracellular domain of the human CTLA-4 protein linked to a region of the human immunoglobulin (Ig). This recombinant soluble fusion protein binds to CD80 and CD86, blocking their interaction with CD28 and thereby inhibiting T-cell proliferation and T-cell-dependent antibody production. The survival of human, rabbit, and porcine islets after transplantation into streptozotocin-treated diabetic mice was found to be prolonged after treatment with CTLA-4Ig. In order to facilitate local protection of pig-to-primate islet xenografts, we generated transgenic pigs expressing LEA29Y, a modification of the original CTLA-4Ig with higher potency, specifically in the pancreatic islets. In LEA29Y, 2 amino acids in the binding region of CTLA-4 are altered. The LEA29Y coding sequence was placed under the control of the 1.3-kb core promoter from the porcine insulin gene (INS), and the polyadenylation signal from the bovine growth hormone gene (GH) was added. The construct was linked with a floxed neomycin resistance cassette and transfected into porcine fetal fibroblasts. The cells were selected and stable clones were pooled and used as donors for nuclear transfer. After electrofusion and activation, embryos were transferred to 2 synchronized gilts; 8 piglets survived to term with 7 of them carrying the transgene. Southern blot analysis suggested that the founder animals contain 1 or 2 independent integration sites. Four founders were autopsied at the age of 3 months to evaluate expression of LEA29Y in the pancreatic islets by immunohistochemistry. The ratio of immunohistochemically stained islet cell profiles to all islet cell profiles in the islet profiles visible in the sections was estimated. The staining intensity was also estimated qualitatively, by grading from weak to strong immunoreactivity (brown color, using DAB as chromogen). Although 2 founders exhibited single LEA29Y-positive islet cells in some pancreatic islet profiles, the other 2 founders showed a high percentage of strongly positive cells in all islet profiles examined, suggesting beta-cell specific expression. Fibroblasts from the latter 2 founders are currently being used for recloning to generate multiple pigs with constitutive expression of LEA29Y in the pancreatic islets. The protective effect of this strategy will be tested by transplanting LEA29Y-expressing porcine islets in diabetic mouse models with a humanized immune system and in diabetic nonhuman primate models. Supported by the Deutsche Forschungsgemeinschaft (FOR 535).

433 NEW TRANSGENIC PIG DIABETES MODEL EXPRESSING THE MUTANT Insulinc93S FOR THE STUDY OF THE PANCREATIC BETA CELL DYSFUNCTION

We previously established a mutant mouse line showing diabetes which was caused by a point mutation in the Insulin 2 (Ins2) gene. The point mutation leads to the amino acid exchange C95S and the loss of the A6-A11 intrachain disulfide bond of insulin. Male heterozygous Ins2C95S mutant mice develop progressive diabetes mellitus with strong reduction of the total pancreatic islet volume and the total beta cell volume together with severe alterations of the beta cell structure. As pigs share many anatomical and physiological characteristics with humans, we aimed to establish a transgenic pig model expressing the mutant insulin by additive gene transfer for the subsequent study of beta cell dysfunction in diabetes mellitus. The transgene consisted of German Landrace insulin sequences including 1.3 kb of the insulin promoter and 1 kb insulin gene sequences with the 3 exons and the T to A (C93S) point mutation in exon 3 analogous to the mutant mouse insulin. A floxed neomycin resistance gene at the 3′ end of the transgene was used as a selection marker. After successful transfection of male fetal fibroblasts of both the German Landrace and the Schwaebisch- Haellisch pig breeds, pooled transgenic fibroblasts were used for somatic cell nuclear transfer (SCNT). Five hundred three reconstructed pig embryos were generated and endoscopically transferred to 5 synchronized recipients. One pregnancy with German Landrace genetic background and one pregnancy with Schwaebisch-Haellisch genetic background of the cloned embryos developed to term, which gave rise to 3 living offspring from each of the 2 pregnancies; 5 of the 6 piglets were transgenic. Southern blot analysis showed different transgene signal patterns in all animals examined. Transgenic pigs of both litters revealed unaltered fasting blood glucose levels up to an age of 8 months. However, disturbed intravenous glucose tolerance and reduced insulin secretion were detected in 1 transgenic pig of the first litter at 8 months of age. The area under the glucose curve of this transgenic pig was 75% larger (22 136 v. 12617) and the area under the insulin curve 53% smaller (1250 v. 2670) compared with the control. Ongoing analyses comprise glucose tolerance tests in the second litter as well as pathohistologic analysis of the pancreata of both litters. Cells from suitable transgenic founders will be used for recloning to establish a new transgenic pig model expressing the mutant InsulinC93S for an in-depth study of pancreatic beta cell dysfunction in diabetes mellitus. Supported by the Deutsche Forschungsgemeinschaft (GRK1029).

426 TRANSGENIC PIGS EXPRESSING HIGH LEVELS OF HUMAN THROMBOMODULIN ON VASCULAR ENDOTHELIUM

The development of a1,3-galactosyltransferase deficient pigs along with overexpression of complement regulatory proteins was an important step to overcome hyperacute rejection of pig organs transplanted into primates. However, the lack of galactose-α1,3-galactose (αGal) epitopes does not protect against subsequent rejection mechanisms, such as acute vascular rejection, which plays a crucial role to achieve prolonged graft survival in pig-to-human xenotransplantation. Acute vascular rejection involves incompatibilities between human blood and porcine endothelial cells, leading to coagulation disorders. Indeed, thrombotic microangiopathy is one of the key characteristics of rejected pig-to-primate grafts from aGal-deficient donor animals. One of the strategies to overcome this coagulation problem by genetic modification of donor pigs is expression of human thrombomodulin (TM) on the porcine endothelium. Although porcine TM is able to bind circulating human thrombin, the resulting heterodimer is unable to cleave human protein C, which promotes the coagulation cascade. We addressed this problem by the development of a vector placing the single-exon open reading frame of human TM under the control of a 6-kb promoter fragment obtained from the porcine TM gene. In addition, we replaced the 3′-untranslated region (UTR) by a polyadenylation box from the bovine growth hormone gene to avoid interferon-y-dependent destabilization of thrombomodulin transcripts. This vector was linked to a floxed neomycin cassette and transfected into porcine fetal fibroblasts. Positive cell clones were selected with G418, mixed, and then used for nuclear transfer. Donor fibroblasts were electrofused with enucleated oocytes resulting in 358 reconstructed embryos (91.1% fusion rate). One or two days later, 294 embryos were transferred to 3 synchronized gilts. In total, 8 cloned transgenic piglets with 1 or 2 independent integration sites of the transgene were born. Heart, kidney, lung, and liver of 5 founder animals were analyzed by immunohistochemistry They were found to express thrombomodulin strongly and strictly limited to the vascular endothelium of at least heart and kidney. The staining intensity was estimated qualitatively, by grading from weak to strong immunoreactivity (brown color, using DAB as chromogen). Cells from founder pigs expressing TM strongly have been used for recloning. The effect of human TM to normalize blood coagulation will be tested in experiments involving ex vivo perfusion of transgenic hearts and kidneys with human blood. Supported by the Deutsche Forschungsgemeinschaft (FOR 535).

Aggressive and invasive growth of tectal glioma after surgical intervention and chemoradiotherapy

A tectal glioma presenting with late-onset aqueduct stenosis and obstructive hydrocephalus is usually categorized as a benign glioma. Apparent clinical or radiological progression justifies biopsy of the tumour. In this case, an unusual tumour shows aggressive and invasive growth after surgical intervention and chemoradiotherapy.

Embolization of Arteriovenous Malformation. Efficacy and Safety of Preoperative Embolization Followed by Surgical Resection of AVM

SUMMARY

Treatment options for cerebral arteriovenous malformation (AVM) are still controversial due to the recent result of stereotactic radiosurgery and the improved result of microsurgical resection. We investigated previously treated AVM cases and discussed the efficacy and safety of preoperative embolization especially for microsurgical resection of high-grade AVM in the Spetzler-Martin grading. Efficacy of preoperative embolization was evaluated based on 126 previously treated AVM cases at Shinshu University Hospital during the last 25 years. The safety of embolization was evaluated based on our previously-embolized 58 AVM cases (91 procedures) in the last 11 years after introduction of preoperative embolization for AVM. In all 126 cases, 82 were treated before introduction of embolization and 44 were treated after introduction of embolization. In 82 cases of the pre-embolization era, 63 lesions were removed totally in 63 AVMs (77%), partially resected in 11 (13%) and untreated in eight (10%). In 74 surgically removed cases, 11 (15%) cases showed severe intra/postoperative bleeding. In 44 cases of the embolization era, lesions were removed totally in 29 AVMs (66%), disappeared only with embolization in one (2%), disappeared with radiosurgery in seven (16%) and were untreated in five (11%). In 32 surgically removed cases, only one (2%) case showed severe intra/postoperative bleeding. In all 58 embolized cases, 44 were surgically removed, six were treated with radiosurgery, one was eliminated with embolization alone and six were partially obliterated and followed up for their location. In 91 procedures for 58 cases, two haemorrhagic and three ischemic complications occurred, three were transient and two remained having neurological deficits. The introduction of preoperative embolization improved the total removal rate and reduced the intra/postoperative bleeding rate in surgical removal of AVM. The total risk of embolization is low and well-designed preoperative embolization makes surgical resection safer even in high-grade AVM in the Spetzler-Martin grading.

Tandemly repeated Fc domain augments binding avidities of antibodies for Fcgamma receptors, resulting in enhanced antibody-dependent cellular cytotoxicity

Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism by which antibodies exert anti-tumor effects. Here, we show that Fc multimerization augments the binding avidities for all of the low-affinity Fcgamma receptors, increasing ADCC activity very much. A chimeric antibody, designated M-Ab, was constructed with the V regions from mouse anti-CD20 mAb 1F5 and the C regions from human IgG1 and kappa chain. Two or three Fc domains were tandemly repeated downstream of the C-terminus of the M-Ab to give D0-Ab (Fc dimer Ab without a linker), T0-Ab (Fc trimer Ab without a linker), and T3-Ab (Fc trimer Ab with a (GGGGS)(3) linker in front of the second and third hinge regions). HPLC and SDS-PAGE analyses of the purified antibodies indicated that the H and L chains were appropriately linked with interchain disulfide bonds and that the Ab preparations did not contain aggregated molecules. Although flow cytometry indicated that Fc multimerization decreased the binding activity for CD20-bearing cells to 1/3 approximately 1/4, the binding avidities for the extracellular domains of low-affinity Fcgamma receptors were greatly augmented. The avidities were in the order of T3-Ab, T0-Ab, D0-Ab and M-Ab, with T3-Ab showing about 100 times greater avidity than M-Ab not only for FcgammaRIIIA, but also for FcgammaRIIA and FcgammaRIIB. The rank order of ADCC activity with human PBMC was the same, and T3-Ab induced ADCC at a 50-100 times less concentration, compared to M-Ab. These Fc tandem repeat antibodies are promising candidates for anti-tumor therapeutics, and should also be useful as tools to elucidate the biological roles of FcgammaRIIA, FcgammaRIIB, and FcgammaRIIIA.

305 TRANSGENIC CLONED PIGS EXPRESSING ORANGE FLUORESCENT PROTEIN KUSABIRA-ORANGE

Transgenic (Tg)-cloned pigs expressing fluorescent proteins are very useful in research such as cell or tissue transplantation studies. In this study, we produced Tg-cloned pigs with an orange fluorescent protein, humanized Kusabira-Orange (huKO), and analyzed the characteristics of these pigs. Fetal fibroblast cells transduced with huKO gene by a gene silencing-resistant retroviral vector, pDΔNhuKO (Suzuki et al. 2002 J. Neurochem. 82, 953–960) were used as nuclear donors. Recipient cytoplasts were prepared using oocytes matured in vitro in NCSU23. The nuclear transfer (NT) embryos were transferred into oviducts of estrus-synchronized recipient gilts after culture in PZM-5 for 1 or 2 days. Cloned pigs obtained were analyzed by Southern blotting for the transgene integration. A total of 23 organs and tissues, including brain, eye, internal and reproductive organs, skin, skeletal muscle, and cartilage were examined by fluorescence stereomicroscopy. Cryo- and paraffin-embedded tissue sections were also prepared to examine fluorescence expression. Immunofluorescent staining of brain cryosection and flow cytometry analysis of peripheral blood cells were performed to identify huKO-expressing cells. Transfer of 429 NT embryos into 4 recipients resulted in 18 (4.2%) cloned offspring. Southern blotting analysis of the cloned pigs confirmed transduction of 2 to 17 copies of the huKO gene in each pig. Autopsy was performed in 6 pigs, and orange fluorescence was confirmed in all the tissues and organs examined in each pig. In addition, prominent orange fluorescence was detected in pancreatic islets and renal glomeruli, indicating that these transgenic pigs are ideal for islet cell transplantation studies. Expression of huKO was also detected in neurons, microglia, and astrocytes in the brain, and granulocytes, monocytes, macrophages, lymphocytes, and platelets in the peripheral blood cells, whereas the expression level in red blood cells was lower. Re-cloning was performed using primary culture fibroblast cells established from 2 Tg-cloned pigs. Transfer of 300 re-cloned embryos into 4 recipients resulted in 3 pregnancies. A re-cloned fetus at Day 44 of gestation showed systemic fluorescence. These results demonstrate that the retroviral vector pD?NhuKO is resistant to gene silencing in pigs, that transduction and expression of the huKO gene had no lethal effects on fetal development, and that a Tg-cloned pig expressing orange fluorescence can be produced by NT of fetal fibroblast cells transduced with the huKO gene. This study was supported by PROBRAIN.

59 IN VITRO DEVELOPMENT OF FELINE CLONED EMBRYOS RECONSTRUCTED WITH PREADIPOCYTES

The technique of somatic cell nuclear transfer (NT) in domestic cats is expected to contribute to the conservation of wildcats, for which extinction is a concern. In this study, we examined in vitro developmental ability of cloned embryos produced using the preadipocytes of domestic cats as nuclear donors. Primary cultures of preadipocytes were established as reported previously (Yagi et al. 2004 Biochem. Biophys. Res. Commun. 321, 967–974). Briefly, fat tissue (2–3 g) was excised from an adult female cat and digested using 0.1% collagenase for 1 h at 37�C followed by centrifugation. Only mature adipocytes that were floating near the surface of the supernatant were collected and placed in a 12.5-cm2 culture flask filled with DMEM containing 20% FBS. The flask was filled with medium, tightly capped, and cultured upside down for 7–10 days, so that the floating adipocytes attached to the inner ceiling surface of the flask. When firm attachment of the cells to the ceiling surface of the flask was confirmed, the flask was then inverted and culture was continued using the routine cell culture technique for adherent cells. In vivo-matured oocytes were collected from the ovaries of domestic cats superovulated by eCG and hCG. IVM oocytes were obtained by culturing cumulus–oocyte complexes from the ovaries collected at local veterinary clinics in TCM199-based medium for 24 to 30 h. In vivo-matured and IVM oocytes were enucleated by aspirating the first polar body and adjacent cytoplasm using a bevelled pipette in the presence of 7.5 µg mL–1 cytochalasin B. The nuclei of the donor cells were transferred to enucleated in vivo-matured and IVM oocytes by means of electric fusion (300 V mm–1, 30 µs, twice). The reconstructed embryos were activated electrically (125 V mm–1, 60 µs, twice), followed by treatment with 10 µg mL–1 cycloheximide and 5 µg mL–1 cytochalasin B. The cloned embryos were cultured in vitro for 7 days in MK-1 so that their developmental ability might be examined. The fusion rate of donor cells was similar between in vivo-matured and IVM oocytes (56.8%, 21/37 v. 54.5%, 42/77). The developmental ability of NT embryos reconstructed with in vivo-matured oocytes was similar to that of NT embryos reconstructed with IVM oocytes (cleavage: 52.4%, 11/21 v. 42.9%, 18/42; development to blastocysts: 9.5%, 2/21 v. 11.9%, 5/42). The results indicate that cloned feline embryos reconstructed using preadipocytes can develop in vitro into blastocysts.

85 VITRIFICATION OF IN VITRO-MATURED PORCINE OOCYTES AT THE METAPHASE-II STAGE

Cryopreservation of mammalian metaphase-II (M-II) oocytes is still impractical compared to that of early stage embryos. In this study we examined the effects of delipation and mitotic spindle stabilization in order to improve the post-vitrification survival rate of in vitro-matured (IVM) porcine oocytes at the M-II stage. Cumulus–oocyte complexes that had been collected from slaughterhouse ovaries were matured in vitro in NCSU23 supplemented with 0.6 mm cysteine, 10 ng mL–1 epidermal growth factor (EGF), 10% porcine follcular fluid (PFF), and 10 IU mL–1 eCG and hCG. The denuded M-II oocytes were vitrified in the presence of 30% ethylene glycol and 0.5 m sucrose using the minimum volume cooling (MVC) method with a MVC plate (Cryotop�; Kitazato Supply, Tokyo, Japan). Vitrified embryos were rewarmed by immersing the MVC plate directly into rewarming solution containing 1 m sucrose and 20% calf serum at 39�C for 1 min, followed by stepwise dilution of the cryoprotectants. We compared the effects of previtrification treatments, namely, (1) delipation, (2) mitotic spindle stabilization, (3) delipation + mitotic spindle stabilization, and (4) no treatment. For delipation, we used a noninvasive method (Esaki et al. 2004 Biol. Reprod. 71, 432–437) that we had published previously with slight modification. The embryos were treated with 4% trypsin at 38�C for approximately two min to expand the zona pellucida, and then centrifuged (12 000g, 38�C 23 min) with 7.5 µg mL–1 cytochalasin B to polarize cytoplasmic lipid droplets within the perivitelline space. For mitotic spindle stabilization, M-II oocytes were vitrified in the presence of 1 µm paclitaxel. After the oocytes were rewarmed, electrical activation of the oocytes (150 V mm–1, 100 µs, one time) was carried out to induce parthenogenesis. These parthenogenetic embryos were cultured in PZM-5 for 7 days, and the number of vitrified embryos that developed into blastocysts with respect to each treatment was determined. The blastcyst formation rate and mean cell numbers of the blastcysts were compared among the treatment groups (chi-square test, Tukey's test). Of the 50 M-II oocytes that had been vitrified without pretreatment, only one oocyte (2.0%) developed into a blastocyst with 20 cells. By contrast, the number of vitrified embryos that developed into blastocysts was significantly high when they were delipated prior to vitrification (37.8%, 14/37, 64.0 � 9.6; P < 0.01). Mitotic spindle stabilization also improved the survival rate of vitrified oocytes (18.6%, 21/113, 56.7 � 9.6; P < 0.01). The combination of delipation and mitotic spindle stabilization produced the highest number of vitrified oocytes that developed into blastocysts (43.8%, 35/80, 69.4 � 6.4), although the difference between the combination group and the delipation group was not significant. These results indicate that blastocysts can be produced very efficiently from IVM porcine oocytes that have been vitrified at the M-II stage using both noninvasive delipation and mitotic spindle stabilization procedures.