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Germ cell depletion in recipient testis has adverse effects on spermatogenesis in orthotopically transplanted testis pieces via retinoic acid insufficiency. Sci Rep 2020; 10:10796. [PMID: 32612133 PMCID: PMC7330030 DOI: 10.1038/s41598-020-67595-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/09/2020] [Indexed: 12/22/2022] Open
Abstract
Germ cell depletion in recipient testes is indispensable for successful transplantation of spermatogonial stem cells. However, we found that such treatment had an adverse effect on spermatogenesis of orthotopically transplanted donor testis tissues. In the donor tissue, the frequency of stimulated by retinoic acid (RA) 8 (STRA8) expression was reduced in germ cells, suggesting that RA signalling indispensable for spermatogenesis was attenuated in germ cell-depleted recipient testes. In this context, germ cell depletion diminished expression of testicular Aldh1a2, which is responsible for testicular RA synthesis, while Cyp26b1, which is responsible for testicular RA metabolism, was still expressed even after germ cell depletion, suggesting an alteration of the RA synthesis/metabolism ratio. These observations suggested that RA insufficiency was one of the causes of the defective donor spermatogenesis. Indeed, repetitive RA administrations significantly improved donor spermatogenesis to produce fertile offspring without any side effects. These findings may contribute to improving fertility preservation techniques for males, especially to prevent iatrogenic infertility induced by chemotherapy in prepubertal cancer patients.
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Moreno-Del Val G, Muñoz-Robledano P. Revitalizing genetically-modified mouse strains using frozen-thawed sperm after up to 192 h of refrigerated epididymis transportation. Lab Anim 2017; 51:526-529. [PMID: 28166693 DOI: 10.1177/0023677217692612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the scientific interchange of genetically-modified mouse strains the transportation of refrigerated epididymis has several advantages over the transportation of live animals, especially with regard to the 3R (replacement, reduction and refinement) principles. The major limiting factor is the duration of the transportation. Previous reports have shown that sperm collected from transported epididymis maintained their fertility for around 72 h, but there are no published data with longer transportation times, and this window of time may be too short, especially for international shipments and where locations are not well connected. In this study live pups were born using frozen-thawed sperm after up to 192 h (8 days) of transportation, using a special in vitro fertilization design which resulted in a fertilization rate of 10.5%.
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Affiliation(s)
- Gonzalo Moreno-Del Val
- Transgenic and Cryopreservation Laboratory, Servicio de Experimentación Animal UMH, Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas /Universidad Miguel Hernández, Alicante, Spain
| | - Patricia Muñoz-Robledano
- Transgenic and Cryopreservation Laboratory, Servicio de Experimentación Animal UMH, Instituto de Neurociencias de Alicante, Consejo Superior de Investigaciones Científicas /Universidad Miguel Hernández, Alicante, Spain
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Yoon SJ, Rahman MS, Kwon WS, Park YJ, Pang MG. Addition of Cryoprotectant Significantly Alters the Epididymal Sperm Proteome. PLoS One 2016; 11:e0152690. [PMID: 27031703 PMCID: PMC4816509 DOI: 10.1371/journal.pone.0152690] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 03/17/2016] [Indexed: 12/11/2022] Open
Abstract
Although cryopreservation has been developed and optimized over the past decades, it causes various stresses, including cold shock, osmotic stress, and ice crystal formation, thereby reducing fertility. During cryopreservation, addition of cryoprotective agent (CPA) is crucial for protecting spermatozoa from freezing damage. However, the intrinsic toxicity and osmotic stress induced by CPA cause damage to spermatozoa. To identify the effects of CPA addition during cryopreservation, we assessed the motility (%), motion kinematics, capacitation status, and viability of epididymal spermatozoa using computer-assisted sperm analysis and Hoechst 33258/chlortetracycline fluorescence staining. Moreover, the effects of CPA addition were also demonstrated at the proteome level using two-dimensional electrophoresis. Our results demonstrated that CPA addition significantly reduced sperm motility (%), curvilinear velocity, viability (%), and non-capacitated spermatozoa, whereas straightness and acrosome-reacted spermatozoa increased significantly (p < 0.05). Ten proteins were differentially expressed (two decreased and eight increased) (>3 fold, p < 0.05) after CPA, whereas NADH dehydrogenase flavoprotein 2, f-actin-capping protein subunit beta, superoxide dismutase 2, and outer dense fiber protein 2 were associated with several important signaling pathways (p < 0.05). The present study provides a mechanistic basis for specific cryostresses and potential markers of CPA-induced stress. Therefore, these might provide information about the development of safe biomaterials for cryopreservation and basic ground for sperm cryopreservation.
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Affiliation(s)
- Sung-Jae Yoon
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, Republic of Korea
| | - Md Saidur Rahman
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, Republic of Korea
| | - Woo-Sung Kwon
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, Republic of Korea
| | - Yoo-Jin Park
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, Republic of Korea
| | - Myung-Geol Pang
- Department of Animal Science and Technology, Chung-Ang University, Anseong, Gyeonggi-do, Republic of Korea
- * E-mail:
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Ohtsuka M, Miura H, Mochida K, Hirose M, Hasegawa A, Ogura A, Mizutani R, Kimura M, Isotani A, Ikawa M, Sato M, Gurumurthy CB. One-step generation of multiple transgenic mouse lines using an improved Pronuclear Injection-based Targeted Transgenesis (i-PITT). BMC Genomics 2015; 16:274. [PMID: 25887549 PMCID: PMC4404087 DOI: 10.1186/s12864-015-1432-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 03/04/2015] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND The pronuclear injection (PI) is the simplest and widely used method to generate transgenic (Tg) mice. Unfortunately, PI-based Tg mice show uncertain transgene expression due to random transgene insertion in the genome, usually with multiple copies. Thus, typically at least three or more Tg lines are produced by injecting over 200 zygotes and the best line/s among them are selected through laborious screening steps. Recently, we developed technologies using Cre-loxP system that allow targeted insertion of single-copy transgene into a predetermined locus through PI. We termed the method as PI-based Targeted Transgenesis (PITT). A similar method using PhiC31-attP/B system was reported subsequently. RESULTS Here, we developed an improved-PITT (i-PITT) method by combining Cre-loxP, PhiC31-attP/B and FLP-FRT systems directly under C57BL/6N inbred strain, unlike the mixed strain used in previous reports. The targeted Tg efficiency in the i-PITT typically ranged from 10 to 30%, with 47 and 62% in two of the sessions, which is by-far the best Tg rate reported. Furthermore, the system could generate multiple Tg mice simultaneously. We demonstrate that injection of up to three different Tg cassettes in a single injection session into as less as 181 zygotes resulted in production of all three separate Tg DNA containing targeted Tg mice. CONCLUSIONS The i-PITT system offers several advantages compared to previous methods: multiplexing capability (i-PITT is the only targeted-transgenic method that is proven to generate multiple different transgenic lines simultaneously), very high efficiency of targeted-transgenesis (up to 62%), significantly reduces animal numbers in mouse-transgenesis and the system is developed under C57BL/6N strain, the most commonly used pure genetic background. Further, the i-PITT system is freely accessible to scientific community.
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Affiliation(s)
- Masato Ohtsuka
- Department of Molecular Life Science, Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
| | - Hiromi Miura
- Department of Molecular Life Science, Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
| | - Keiji Mochida
- RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074, Japan.
| | - Michiko Hirose
- RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074, Japan.
| | - Ayumi Hasegawa
- RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074, Japan.
| | - Atsuo Ogura
- RIKEN BioResource Center, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074, Japan. .,Graduate School of Life and Environmental Science, University of Tsukuba, 1-1-1 Ten-noudai, Tsukuba, Ibaraki, 305-8572, Japan.
| | - Ryuta Mizutani
- Graduate School of Engineering, Tokai University, Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan.
| | - Minoru Kimura
- Department of Molecular Life Science, Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
| | - Ayako Isotani
- Immunology Frontier Research Center, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Masahito Ikawa
- Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Masahiro Sato
- Section of Gene Expression Regulation, Frontier Science Research Center, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima, Kagoshima, 890-8544, Japan.
| | - Channabasavaiah B Gurumurthy
- Mouse Genome Engineering Core Facility, Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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Kamimura S, Hatanaka Y, Hirasawa R, Matsumoto K, Oikawa M, Lee J, Matoba S, Mizutani E, Ogonuki N, Inoue K, Kohda T, Ishino F, Ogura A. Establishment of Paternal Genomic Imprinting in Mouse Prospermatogonia Analyzed by Nuclear Transfer1. Biol Reprod 2014; 91:120. [DOI: 10.1095/biolreprod.114.120451] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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Kenyon J, Guan M, Bogani D, Marschall S, Raspa M, Pickard A, Takeo T, Nakagata N, Fray M. Transporting mouse embryos and germplasm as frozen or unfrozen materials. ACTA ACUST UNITED AC 2014; 4:47-65. [PMID: 25723918 DOI: 10.1002/9780470942390.mo140064] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The 21st century has seen a huge proliferation in the availability of genetically altered mice. The availability of these resources has been accompanied by ever greater opportunities for international collaborations between laboratories involving the exchange of mouse strains. This exchange can involve significant costs in terms of animal welfare and transportation expenses. In an attempt to mitigate some of these costs, the mouse community has developed a battery of techniques that can be used to avoid transporting live mice. Transporting frozen embryos and sperm at liquid nitrogen (LN2 ) temperatures using dry shippers has been common practice for some time. However, current advances in this field have refined transportation procedures and introduced new techniques for disseminating embryos and sperm: for example, shipping frozen sperm on dry ice, exchanging unfrozen epididymides from which sperm can be extracted, and transporting frozen/thawed embryos in isotonic media. This article discusses some of the current practices used by laboratories to transport mouse strains around the world without having to exchange live mice.
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Affiliation(s)
- Janet Kenyon
- Mary Lyon Centre, Medical Research Council, Harwell Science and Innovation Campus, Oxfordshire, United Kingdom
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Takeo T, Fukumoto K, Kondo T, Haruguchi Y, Takeshita Y, Nakamuta Y, Tsuchiyama S, Yoshimoto H, Shimizu N, Li MW, Kinchen K, Vallelunga J, Lloyd KCK, Nakagata N. Investigations of motility and fertilization potential in thawed cryopreserved mouse sperm from cold-stored epididymides. Cryobiology 2013; 68:12-7. [PMID: 24201107 DOI: 10.1016/j.cryobiol.2013.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/23/2013] [Accepted: 10/24/2013] [Indexed: 11/26/2022]
Abstract
Cold transport of epididymides from genetically modified mice is an efficient alternative to the shipment of live animals between research facilities. Mouse sperm from epididymides cold-stored for short periods can maintain viability. We previously reported that cold storage of mouse epididymides in Lifor® perfusion medium prolonged sperm motility and fertilization potential and that the sperm efficiently fertilized oocytes when reduced glutathione was added to the fertilization medium. Cryopreservation usually results in decreased sperm viability; an optimized protocol for cold storage of epididymides plus sperm cryopreservation has yet to be established. Here, we examined the motility and fertilization potential of cryopreserved, thawed (frozen-thawed) sperm from previously cold-stored mouse epididymides. We also examined the protective effect of sphingosine-1-phosphate (S1P) on sperm viability when S1P was added to the preservation medium during cold storage. We assessed viability of frozen-thawed sperm from mouse epididymides that had been cold-transported domestically or internationally and investigated whether embryos fertilized in vitro with these sperm developed normally when implanted in pseudo-pregnant mice. Our results indicate that frozen-thawed sperm from epididymides cold-stored for up to 48 h maintained high fertilization potential. Fertilization potential was reduced after cold storage for 72 h, but not if S1P was included in the cold storage medium. Live pups were born normally to recipients after in vitro fertilization using frozen-thawed sperm from cold-transported epididymides. In summary, we demonstrate an improved protocol for cold-storage of epididymides that can facilitate transport of genetically engineered-mice and preserve sperm viability after cryopreservation.
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Affiliation(s)
- Toru Takeo
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Kiyoko Fukumoto
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Tomoko Kondo
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Yukie Haruguchi
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Yumi Takeshita
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Yuko Nakamuta
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Shuuji Tsuchiyama
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Hidetaka Yoshimoto
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
| | - Norihiko Shimizu
- Animal Laboratory for Medical Research, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa 078-8510, Japan
| | - Ming-Wen Li
- Mouse Biology Program, University of California, Davis, CA 95618, USA
| | - Kristy Kinchen
- Mouse Biology Program, University of California, Davis, CA 95618, USA
| | - Jadine Vallelunga
- Mouse Biology Program, University of California, Davis, CA 95618, USA
| | - K C Kent Lloyd
- Mouse Biology Program, University of California, Davis, CA 95618, USA
| | - Naomi Nakagata
- Division of Reproductive Engineering, Center for Animal Resources and Development, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
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Oikawa M, Inoue K, Shiura H, Matoba S, Kamimura S, Hirose M, Mekada K, Yoshiki A, Tanaka S, Abe K, Ishino F, Ogura A. Understanding the X chromosome inactivation cycle in mice: a comprehensive view provided by nuclear transfer. Epigenetics 2013; 9:204-11. [PMID: 24172050 DOI: 10.4161/epi.26939] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
During mouse development, imprinted X chromosome inactivation (XCI) is observed in preimplantation embryos and is inherited to the placental lineage, whereas random XCI is initiated in the embryonic proper. Xist RNA, which triggers XCI, is expressed ectopically in cloned embryos produced by somatic cell nuclear transfer (SCNT). To understand these mechanisms, we undertook a large-scale nuclear transfer study using different donor cells throughout the life cycle. The Xist expression patterns in the reconstructed embryos suggested that the nature of imprinted XCI is the maternal Xist-repressing imprint established at the last stage of oogenesis. Contrary to the prevailing model, this maternal imprint is erased in both the embryonic and extraembryonic lineages. The lack of the Xist-repressing imprint in the postimplantation somatic cells clearly explains how the SCNT embryos undergo ectopic Xist expression. Our data provide a comprehensive view of the XCI cycle in mice, which is essential information for future investigations of XCI mechanisms.
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Affiliation(s)
- Mami Oikawa
- RIKEN BioResource Center; Tsukuba, Japan; Medical Research Institute; Tokyo Medical and Dental University; Tokyo, Japan
| | - Kimiko Inoue
- RIKEN BioResource Center; Tsukuba, Japan; Graduate School of Life and Environmental Science; University of Tsukuba; Tsukuba, Japan
| | | | | | - Satoshi Kamimura
- RIKEN BioResource Center; Tsukuba, Japan; Graduate School of Life and Environmental Science; University of Tsukuba; Tsukuba, Japan
| | | | | | | | - Satoshi Tanaka
- Department of Animal Resource Sciences/Veterinary Medical Sciences; University of Tokyo; Tokyo, Japan
| | - Kuniya Abe
- RIKEN BioResource Center; Tsukuba, Japan; Graduate School of Life and Environmental Science; University of Tsukuba; Tsukuba, Japan
| | - Fumitoshi Ishino
- Medical Research Institute; Tokyo Medical and Dental University; Tokyo, Japan
| | - Atsuo Ogura
- RIKEN BioResource Center; Tsukuba, Japan; Graduate School of Life and Environmental Science; University of Tsukuba; Tsukuba, Japan; Center for Disease Biology and Integrative Medicine; University of Tokyo; Tokyo, Japan
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9
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Okae H, Matoba S, Nagashima T, Mizutani E, Inoue K, Ogonuki N, Chiba H, Funayama R, Tanaka S, Yaegashi N, Nakayama K, Sasaki H, Ogura A, Arima T. RNA sequencing-based identification of aberrant imprinting in cloned mice. Hum Mol Genet 2013; 23:992-1001. [PMID: 24105465 DOI: 10.1093/hmg/ddt495] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Animals cloned by somatic cell nuclear transfer (SCNT) provide a unique model for understanding the mechanisms of nuclear epigenetic reprogramming to a state of totipotency. Though many phenotypic abnormalities have been demonstrated in cloned animals, the underlying mechanisms are not well understood. In this study, we performed transcriptome-wide allelic expression analyses in brain and placental tissues of cloned mice. We found that Gab1, Sfmbt2 and Slc38a4 showed loss of imprinting in all cloned mice analyzed, which might be involved in placentomegaly of cloned mice. These three genes did not require de novo DNA methylation in growing oocytes for the establishment of imprinting, implying the involvement of a de novo DNA methylation-independent mechanism. Loss of Dlk1-Dio3 imprinting was also observed in nearly half of cloned mouse embryos and showed a strong correlation with embryonic lethality. Our findings are essential to understand the underlying mechanisms of developmental abnormalities of cloned animals. We also emphasize that particular attention should be paid to specific imprinted genes for therapeutic and agricultural applications of SCNT.
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Affiliation(s)
- Hiroaki Okae
- Department of Informative Genetics, Environment and Genome Research Center
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10
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Mochida K, Hasegawa A, Li MW, Fray MD, Kito S, Vallelunga JM, Lloyd KCK, Yoshiki A, Obata Y, Ogura A. High osmolality vitrification: a new method for the simple and temperature-permissive cryopreservation of mouse embryos. PLoS One 2013; 8:e49316. [PMID: 23341870 PMCID: PMC3547031 DOI: 10.1371/journal.pone.0049316] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 10/07/2012] [Indexed: 11/24/2022] Open
Abstract
Procedures for cryopreserving embryos vary considerably, each having its specific advantages and disadvantages in terms of technical feasibility, embryo survival yield, temperature permissibility and species- or strain-dependent applicability. Here we report a high osmolality vitrification (HOV) method that is advantageous in these respects. Cryopreservation by vitrification is generally very simple, but, unlike slow freezing, embryos should be kept at a supercooling temperature (below –130°C) to avoid cryodamage. We overcame this problem by using an HOV solution containing 42.5% (v/v) ethylene glycol, 17.3% (w/v) Ficoll and 1.0 M sucrose. This solution is more viscous than other cryopreservation solutions, but easy handling of embryos was assured by employing a less viscous equilibration solution before vitrification. Most (>80%) embryos cryopreserved in this solution survived at –80°C for at least 30 days. Normal mice were recovered even after intercontinental transportation in a conventional dry-ice package for 2–3 days, indicating that special containers such as dry shippers with liquid nitrogen vapor are unnecessary. The HOV solution could also be employed for long-term storage in liquid nitrogen, as with other conventional cryoprotectants. Finally, we confirmed that this new vitrification method could be applied successfully to embryos of all six strains of mice we have tested so far. Thus, our HOV method provides an efficient and reliable strategy for the routine cryopreservation of mouse embryos in animal facilities and biomedical laboratories, and for easy and cheap transportation.
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Affiliation(s)
| | | | - Ming-Wen Li
- Mouse Biology Program, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Martin D. Fray
- Medical Research Council Mary Lyon Centre, Harwell Science and Innovation Centre, Oxon, United Kingdom
| | - Seiji Kito
- National Institute of Radiological Sciences, Chiba-shi, Chiba, Japan
| | - Jadine M. Vallelunga
- Mouse Biology Program, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - K. C. Kent Lloyd
- Mouse Biology Program, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | | | - Yuichi Obata
- RIKEN BioResource Center, Tsukuba, Ibaraki, Japan
| | - Atsuo Ogura
- RIKEN BioResource Center, Tsukuba, Ibaraki, Japan
- Graduate School of Life and Environmental Science, University of Tsukuba, Ibaraki, Japan
- The Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Tokyo, Japan
- * E-mail:
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11
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Overview of new developments in and the future of cryopreservation in the laboratory mouse. Mamm Genome 2012; 23:572-9. [PMID: 22936001 DOI: 10.1007/s00335-012-9423-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 07/30/2012] [Indexed: 10/27/2022]
Abstract
The large-scale mutagenesis programmes underway around the world are generating thousands of novel GA mouse strains that need to be securely archived. In parallel with advances in mutagenesis, the procedures used to cryopreserve mouse stocks are being continually refined in order to keep pace with demand. Moreover, the construction of extensive research infrastructures for systematic phenotyping is fuelling demand for these novel strains of mice and new approaches to the distribution of frozen and unfrozen embryos and gametes are being developed in order to reduce the dependency on the transportation of live mice. This article highlights some contemporary techniques used to archive, rederive, and transport mouse strains around the world.
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12
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Takeo T, Tsutsumi A, Omaru T, Fukumoto K, Haruguchi Y, Kondo T, Nakamuta Y, Takeshita Y, Matsunaga H, Tsuchiyama S, Sakoh K, Nakao S, Yoshimoto H, Shimizu N, Nakagata N. Establishment of a transport system for mouse epididymal sperm at refrigerated temperatures. Cryobiology 2012; 65:163-8. [PMID: 22722060 DOI: 10.1016/j.cryobiol.2012.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/01/2012] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
The exchange of genetically engineered mouse strains between research facilities requires transporting fresh mouse sperm under refrigerated temperatures. Although sperm generally maintains fertility for 48 h at cold temperatures, in vitro fertilization rates of C57BL/6 mouse sperm are low after 48-h cold storage. Furthermore, 48 h is often not sufficient for the specimens to reach their destinations. To increase the availability of this technology, we aimed to extend the cold storage period while maintaining sperm fertility. In this study, we determined the optimal medium for sperm preservation and evaluated the effect of reduced glutathione in the fertilization medium on sperm fertility after cold storage. We found that higher fertility levels were maintained after 72-h cold storage in the preservation medium Lifor compared with storage in paraffin oil, M2 medium, or CPS-1 medium. In addition, 1.0 mM glutathione enhanced sperm fertility. After transporting sperm from Asahikawa Medical University to our laboratory, embryos were efficiently produced from the cold-stored sperm. After transfer, these embryos developed normally into live pups. Finally, we tested the transport system using genetically engineered mouse strains and obtained similar high fertilization rates with all specimens. In summary, we demonstrated that cold storage of sperm in Lifor maintains fertility, and glutathione supplementation increased the in vitro fertilization rates of sperm after up to 96 h of cold storage. This improved protocol provides a simple alternative to transporting live animals or cryopreserved samples for the exchange of genetically engineered mouse strains among research facilities.
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Affiliation(s)
- Toru Takeo
- Division of Reproductive Engineering, Center for Animal Resources and Development-CARD, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
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13
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Hasegawa A, Mochida K, Matoba S, Yonezawa K, Ohta A, Watanabe G, Taya K, Ogura A. Efficient production of offspring from Japanese wild-derived strains of mice (Mus musculus molossinus) by improved assisted reproductive technologies. Biol Reprod 2012; 86:167, 1-7. [PMID: 22337332 DOI: 10.1095/biolreprod.111.098491] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Because the genetic diversity of the laboratory mouse (Mus musculus) is very limited, wild-derived strains from this genus could provide invaluable experimental models for studies of mouse genetics and epigenetics such as quantitative trait locus analysis. However, such strains generally show poor reproductive performance under conventional husbandry conditions, so their use for large-scale analyses has been limited. This study was undertaken to devise assisted reproductive technologies (ARTs) for the efficient production of offspring in two wild-derived strains, MSM/Ms and JF1/Ms (Mus musculus molossinus). First, as females of these strains are poor responders to equine chorionic gonadotropin (eCG) stimulation, we examined the efficiency of superovulation by injecting anti-inhibin serum followed by human chorionic gonadotropin (hCG). Approximately four to six times more oocytes were ovulated than with eCG-hCG treatment in both strains, reaching ∼25-30 oocytes per female. Consequently, the procedures for in vitro fertilization using these superovulated oocytes and cryopreservation of embryos and spermatozoa could be optimized for both of the wild-derived strains. However, MSM/Ms embryos but not JF1/Ms embryos failed to develop to term after embryo transfer because of intrauterine death at mid to late gestation. We were able to overcome this obstacle by cotransfer of these embryos with those from laboratory strains combined with treatment of recipient females with an immunosuppressant (cyclosporin A). Thus, a series of ARTs essential for efficient production and preservation of the wild-derived strains were successfully devised. These technologies will facilitate systematic studies of mouse genetics and epigenetics using a wider range of genetic diversity than currently available in the genus Mus.
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Li C, Mizutani E, Ono T, Terashita Y, Jia XF, Shi HJ, Wakayama T. Intracytoplasmic Sperm Injection with Mouse Spermatozoa Preserved Without Freezing for Six Months Can Lead to Full-Term Development1. Biol Reprod 2011; 85:1183-90. [DOI: 10.1095/biolreprod.111.091827] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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RNAi-mediated knockdown of Xist can rescue the impaired postimplantation development of cloned mouse embryos. Proc Natl Acad Sci U S A 2011; 108:20621-6. [PMID: 22065773 DOI: 10.1073/pnas.1112664108] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cloning mammals by somatic cell nuclear transfer (SCNT) is highly inefficient. Most SCNT-generated embryos die after implantation because of unidentified, complex epigenetic errors in the process of postimplantation embryonic development. Here we identify the most upstream level of dysfunction leading to impaired development of clones by using RNAi against Xist, a gene responsible for X chromosome inactivation (XCI). A prior injection of Xist-specific siRNA into reconstructed oocytes efficiently corrected SCNT-specific aberrant Xist expression at the morula stage, but failed to do so thereafter at the blastocyst stage. However, we found that shortly after implantation, this aberrant XCI status in cloned embryos had been corrected autonomously in both embryonic and extraembryonic tissues, probably through a newly established XCI control for postimplantation embryos. Embryo transfer experiments revealed that siRNA-treated embryos showed 10 times higher survival than controls as early as embryonic day 5.5 and this high survival persisted until term, resulting in a remarkable improvement in cloning efficiency (12% vs. 1% in controls). Importantly, unlike control clones, these Xist-siRNA clones at birth showed only a limited dysregulation of their gene expression, indicating that correction of Xist expression in preimplantation embryos had a long-term effect on their postnatal normality. Thus, contrary to the general assumption, our results suggest that the fate of cloned embryos is determined almost exclusively before implantation by their XCI status. Furthermore, our strategy provides a promising breakthrough for mammalian SCNT cloning, because RNAi treatment of oocytes is readily applicable to most mammal species.
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Hasegawa A, Yonezawa K, Ohta A, Mochida K, Ogura A. Optimization of a protocol for cryopreservation of mouse spermatozoa using cryotubes. J Reprod Dev 2011; 58:156-61. [PMID: 22041277 DOI: 10.1262/jrd.11-097n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The rapid increase in the number of genetically modified mouse strains has produced a high demand for their frozen spermatozoa from laboratories and mouse banking facilities. Historically, plastic straws have been used preferentially as containers for frozen mammalian spermatozoa because spermatozoa frozen in plastic straws have a high survival rate after thawing. However, plastic straws are more fragile and are used less often than the cryotubes used for conventional cell freezing. In this study, we sought to develop a new protocol for sperm freezing using cryotubes as the container to increase the accessibility of mouse sperm cryopreservation. Epididymal spermatozoa were collected from mature ICR or C57BL/6J (B6) males and were suspended in 18% raffinose and 3% skim milk solution. We then optimized the following conditions using the sperm survival rate as an index: 1) distance of cryotubes from the surface of the liquid nitrogen at freezing, 2) volume of the sperm suspension in the cryotube and 3) temperature of warming sperm during thawing. The best result was obtained when cryotubes containing 10 µl of sperm suspension were immersed 1 cm below the surface of the liquid nitrogen and then thawed at 50 C. The fertilization rates using spermatozoa frozen and thawed using this method were 63.1% in ICR mice and 28.2% in B6 mice. The latter rate was increased to 62.3% by adding reduced glutathione to the fertilization medium. After embryo transfer, 68% and 62% of the fertilized oocytes developed into normal offspring in the ICR and B6 strains, respectively. These results show that cryotubes can be used for cryopreservation of mouse spermatozoa under optimized conditions. This protocol is easy and reproducible, and it may be used in laboratories that do not specialize in sperm cryopreservation.
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Kohda T, Ogonuki N, Inoue K, Furuse T, Kaneda H, Suzuki T, Kaneko-Ishino T, Wakayama T, Wakana S, Ogura A, Ishino F. Intracytoplasmic sperm injection induces transcriptome perturbation without any transgenerational effect. Biochem Biophys Res Commun 2011; 410:282-8. [PMID: 21658372 DOI: 10.1016/j.bbrc.2011.05.133] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 05/25/2011] [Indexed: 12/20/2022]
Abstract
Faithful transcriptome regulation is important in development and also crucial for applications in reproductive and regenerative medicine. Intracytoplasmic sperm injection (ICSI), one of the human assisted reproductive technologies (ART), has long raised concerns about its influence on development. No clear consensus has been reached, however, in spite of many cohort studies carried out in the last two decades on the children conceived by ICSI and/or in vitro fertilization (IVF). In this study, the pre- and postnatal effects of ICSI were assessed using comprehensive transcriptome and phenotypic analyses in mice under strict conditions. Here we demonstrate that, in contrast to IVF, ICSI induces distinct long-lasting transcriptome change that remains at the neonatal stage. Importantly, no remarkable differences were observed in the ICSI adults in either the gene expression or phenotypic profiles, and there was no indication of transmission to the next generation via natural mating. Our results suggest there are no lifelong or transgenerational effects of ICSI, but the ICSI effects during neonatal period remain to be evaluated.
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Affiliation(s)
- Takashi Kohda
- Department of Epigenetics, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan
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18
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Fulka H, Hirose M, Inoue K, Ogonuki N, Wakisaka N, Matoba S, Ogura A, Mosko T, Kott T, Fulka J. Production of Mouse Embryonic Stem Cell Lines from Maturing Oocytes by Direct Conversion of Meiosis into Mitosis. Stem Cells 2011; 29:517-27. [PMID: 21425414 DOI: 10.1002/stem.585] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Helena Fulka
- Department of Biology of Reproduction, Institute of Animal Science, Prague, Czech Republic
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19
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Successful pregnancy after intracytoplasmic sperm injection with testicular spermatozoa transported only under refrigeration. Reprod Med Biol 2010; 9:173-177. [PMID: 29699340 DOI: 10.1007/s12522-010-0053-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2009] [Accepted: 04/24/2010] [Indexed: 10/19/2022] Open
Abstract
Purpose This case report describes two successful pregnancies after intracytoplasmic sperm injection (ICSI) with testicular spermatozoa that were transported under refrigeration. Methods Two first-time couples consulted our clinic concerned about their primary infertility. No sperm were present in the semen samples from either of the husbands and they were referred to the urology department (UD) of a neighbouring hospital. At the UD, seminiferous tubules were obtained by testicular sperm extraction. The tissue samples were put in a centrifuge tube with phosphate-buffered saline at 6°C and placed with refrigerant in a cushioned styrofoam box that was then transported to our clinic. Immediately upon arrival at our clinic, testicular spermatozoa were extracted. On the same day, ovum pickup was performed and mature oocytes were extracted that were then inseminated by conventional ICSI. Fertilized eggs were cultured for 2 days, and then cleaved embryos were cryopreserved. In one case after 4 months and in the other case after 2 months of cryopreservation, the frozen-thawed embryos were transferred. Result Both patients became pregnant and normal, healthy babies were born. Conclusions These results suggest that cases of obstructive azoospermia can be treated with ICSI by refrigerated transport of the seminiferous tubules, in cooperation with a UD, in a small single departmental obstetrics and gynecology clinic.
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Abstract
As more and more genetically modified mouse lines are being generated, it becomes increasingly common to share animal models among different research institutions. Live mice are routinely transferred between animal facilities. Due to various issues concerning animal welfare, intellectual property rights, colony health status and biohazard, significant paperwork and coordination are required before any animal travel can take place. Shipping fresh or frozen preimplantation embryos, gametes, or reproductive organs can bypass some of the issues associated with live animal transfer, but it requires the receiving facilities to be able to perform delicate and sometimes intricate procedures such as embryo transfer, in vitro fertilization (IVF), or ovary transplantation. Here, we summarize the general requirements for live animal transport and review some of the assisted reproductive technologies (ART) that can be applied to shipping and reviving mouse lines. Intended users of these methods should consult their institution's responsible official to find out whether each specific method is legal or appropriate in their own animal facilities.
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Affiliation(s)
- Yubin Du
- Transgenic Core Facility, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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Kaneko T, Fukumoto K, Haruguchi Y, Kondo T, Machida H, Koga M, Nakagawa Y, Tsuchiyama S, Saiki K, Noshiba S, Nakagata N. Fertilization of C57BL/6 mouse sperm collected from cauda epididymides after preservation or transportation at 4 degrees C using laser-microdissected oocytes. Cryobiology 2009; 59:59-62. [PMID: 19394323 DOI: 10.1016/j.cryobiol.2009.04.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 04/15/2009] [Accepted: 04/16/2009] [Indexed: 10/20/2022]
Abstract
The C57BL/6 mouse is commonly used to produce transgenic and knockout strains for biomedical research. However, the motility and fertility of its sperm decrease markedly with freezing. Short-term preservation of sperm without freezing can avoid this. Furthermore, such samples can be transported safety without the special skills or equipment needed for the transportation of live animals or frozen products. We evaluated the motility and fertility of sperm collected from cauda epididymides after preservation or transportation at 4 degrees C. Oocytes with the zona pellucida subjected to laser-microdissection were used to assist fertilization in vitro. Although the motility of sperm gradually decreased with storage (P<0.05), no disruption of the sperm plasma membrane was seen. The proportion of zona-intact oocytes fertilized with sperm preserved for 0, 24, 48 and 72h were 70, 14, 5 and 1%, respectively. On the other hand, 45, 20 and 14% of laser-microdissected oocytes were fertilized by sperm preserved for 24, 48 and 72h, respectively (P<0.05). The fertility of sperm collected from cauda epididymides of two transgenic strains after transportation at 4 degrees C were also significantly increased using laser-microdissected oocytes rather than zona-intact oocytes (57 and 68% vs. 5%, P<0.05). Efficient production of offspring from sperm preserved or transported at 4 degrees C was achieved using laser-microdissected oocytes. Thus the fertility of sperm preserved or transported at 4 degrees C could be maintained, although motility gradually decreased with storage. Laser-microdissected oocytes will contribute to the efficient production of embryos and offspring using such preserved sperm samples.
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Affiliation(s)
- Takehito Kaneko
- Division of Reproductive Engineering, Center for Animal Resources and Development (CARD), Kumamoto University, Honjo, Kumamoto, Japan.
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Miki H, Wakisaka N, Inoue K, Ogonuki N, Mori M, Kim JM, Ohta A, Ogura A. Embryonic rather than extraembryonic tissues have more impact on the development of placental hyperplasia in cloned mice. Placenta 2009; 30:543-6. [PMID: 19345413 DOI: 10.1016/j.placenta.2009.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/08/2009] [Accepted: 03/10/2009] [Indexed: 11/15/2022]
Abstract
Somatic cell cloning by nuclear transfer (NT) in mice is associated with hyperplastic placentas at term. To dissect the effects of embryonic and extraembryonic tissues on this clone-associated phenotype, we constructed diploid (2n) fused with (<-->) tetraploid (4n) chimeras from NT- and fertilization-derived (FD) embryos. Generally, the 4n cells contributed efficiently to all the extraembryonic tissues but not to the embryo itself. Embryos constructed by 2n NT<-->4n FD aggregation developed hyperplastic placentas (0.33+/-0.22 g) with a predominant contribution by NT-derived cells. Even when the population of FD-derived cells in placentas was increased using multiple FD embryos (up to four) for aggregation, most placentas remained hyperplastic (0.36+/-0.13 g). By contrast, placentas of the reciprocal combination, 2n FD<-->4n NT, were less hyperplastic (0.15+/-0.02 g). These nearly normal-looking placentas had a large proportion of NT-derived cells. Thus, embryonic rather than extraembryonic tissues had more impact on the onset of placental hyperplasia, and that the abnormal placentation in clones occurs in a noncell-autonomous manner. These findings suggest that for improvement of cloning efficiency we should understand the mechanisms regulating placentation, especially those of embryonic origin that might control the proliferation of trophoblastic lineage cells.
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Affiliation(s)
- H Miki
- Bioresource Center, RIKEN, Tsukuba, Ibaraki 305-0074, Japan
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Wakisaka N, Inoue K, Ogonuki N, Miki H, Sekita Y, Hanaki K, Akatsuka A, Kaneko-Ishino T, Ishino F, Ogura A. Ultrastructure of placental hyperplasia in mice: comparison of placental phenotypes with three different etiologies. Placenta 2008; 29:753-9. [PMID: 18602690 DOI: 10.1016/j.placenta.2008.05.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 05/19/2008] [Accepted: 05/22/2008] [Indexed: 11/28/2022]
Abstract
Hyperplastic placentas have been reported in several experimental mouse models, including animals produced by somatic cell nuclear transfer, by inter(sub)species hybridization, and by somatic cytoplasm introduction to oocytes followed by intracytoplasmic sperm injection. Of great interest are the gross and histological features common to these placental phenotypes--despite their quite different etiologies--such as the enlargement of the spongiotrophoblast layers. To find morphological clues to the pathways leading to these similar placental phenotypes, we analyzed the ultrastructure of the three different types of hyperplastic placenta. Most cells affected were of trophoblast origin and their subcellular ultrastructural lesions were common to the three groups, e.g., a heavy accumulation of cytoplasmic vacuoles in the trophoblastic cells composing the labyrinthine wall and an increased volume of spongiotrophoblastic cells with extraordinarily dilatated rough endoplasmic reticulum. Although the numbers of trophoblastic glycogen cells were greatly increased, they maintained their normal ultrastructural morphology, including a heavy glycogen deposition throughout the cytoplasm. The fetal endothelium and small vessels were nearly intact. Our ultrastructural study suggests that these three types of placental hyperplasias, with different etiologies, may have common pathological pathways, which probably exclusively affect the development of certain cell types of the trophoblastic lineage during mouse placentation.
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Affiliation(s)
- N Wakisaka
- Bioresouce Center, RIKEN, Tsukuba, Ibaraki 305-0074, Japan
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Fan ZQ, Li XW, Liu Y, Meng QG, Wang YP, Hou YP, Zhou GB, Zhu SE. Piezo-assisted in vitro fertilization of mouse oocytes with spermatozoa retrieved from epididymides stored at 4 degree C. J Reprod Dev 2008; 54:107-12. [PMID: 18239354 DOI: 10.1262/jrd.19118] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study was performed to investigate the effect of partial zona pellucida incision by piezo micromanipulation (ZIP) on the in vitro fertilizing ability of stored mouse spermatozoa. The storage conditions were optimized by storing the mouse epididymides at 4 C in mineral oil or in the mouse body for up to 4 days after death, and the retrieved spermatozoa were used to fertilize fresh oocytes. No significant difference was observed in fertilization rates between the treatments when epididymides were stored for up to 2 days, but the fertilization rates in mineral oil were higher (P<0.05) than those in the mouse body at 3 (41.4 vs. 16.2%) and 4 days (26.0 vs. 15.8%). Spermatozoa retrieved from epididymides stored in mineral oil were then used to fertilize fresh and vitrified oocytes with or without ZIP treatment. The fertilization rates of the ZIP fresh oocytes were higher than those of the zona-intact oocytes at each time point (1 to 4 days). After ZIP, the fertilization rates of spermatozoa stored for 1 and 2 days (91.2 and 86.6%, respectively) were similar (P>0.05) to that of fresh spermatozoa (91.9%). In regard to vitrified oocytes, the fertilization rates of zona-intact and ZIP oocytes using fresh spermatozoa were 46.7 and 84.7%, while the fertilization rates of vitrified ZIP oocytes using spermatozoa stored for 1 to 4 days ranged from 49.3 to 79.6%. When 2-cell embryos derived from ZIP fresh and vitrified oocytes inseminated with 2 day-stored spermatozoa were transferred into recipient females, 47.9 and 15.0% of the embryos developed to term, respectively. These results indicate that storing mouse epididymides at 4 C in mineral oil is more suitable than storage in the mouse body and that the ZIP technique improves the in vitro fertilizing ability of stored mouse spermatozoa in fresh oocytes and significantly increases the fertilization rate of vitrified oocytes with fresh spermatozoa.
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Affiliation(s)
- Zhi-Qiang Fan
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, Beijing, China
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