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Effective Oocyte Vitrification and Survival Techniques for Bovine Somatic Cell Nuclear Transfer.

ABSTRACT: Bovine somatic cell nuclear transfer (SCNT) using vitrified-thawed (VT) oocytes has been studied; however, the cloning efficiency of these oocytes is not comparable with that of nonvitrified (non-V) fresh oocytes. This study sought to optimize the survival and cryopreservation of VT oocytes for SCNT. Co-culture with feeder cells that had been preincubated for 15 h significantly improved the survival of VT oocytes and their in vitro developmental potential following SCNT in comparison to co-culture with feeder cells that had been preincubated for 2, 5, or 24 h (p<0.05). Spindle assessment via the Oosight Microscopy Imaging System and microtubule staining revealed that vitrified metaphase II oocytes (VT group) were not suitable for SCNT. However, enucleating and/or activating oocytes prior to freezing enhanced their developmental potential and suitability for SCNT. The cloning efficiency of the enucleated-activated-vitrified-thawed (EAVT) group (21.6%) was better than that of the other vitrification groups [enucleated-vitrified-thawed (EVT) group, 13.7%; VT group, 15.0%; p<0.05] and was comparable with that of the non-V group (25.9%). The reactive oxygen species level was significantly lower in the EAVT group than in the other vitrification groups (p<0.05). mRNA levels of maternal genes (ZAR1, BMP15, and NLRP5) and a stress gene (HSF1) were lower in the vitrification groups than in the non-V group (p<0.05), whereas the level of phospho-p44/42 mitogen-activated protein kinase did not differ among the groups. Among the vitrification groups, blastocysts in the EAVT group had the best developmental potential, as judged by their high mRNA expression of developmental potential-related genes (POU5f1, Interferon-tau, and SLC2A5) and their low expression of proapoptotic (CASP3) and stress (Hsp70) genes. This study demonstrates that SCNT using bovine frozen-thawed oocytes can be successfully achieved using optimized vitrification and co-culture techniques.

SUBMITTER: Park MJ

PROVIDER: S-EPMC4487599 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Effective Oocyte Vitrification and Survival Techniques for Bovine Somatic Cell Nuclear Transfer.

Park Min Jee MJ Lee Seung Eun SE Kim Eun Young EY Lee Jun Beom JB Jeong Chang Jin CJ Park Se Pill SP

Cellular reprogramming 20150518 3

Bovine somatic cell nuclear transfer (SCNT) using vitrified-thawed (VT) oocytes has been studied; however, the cloning efficiency of these oocytes is not comparable with that of nonvitrified (non-V) fresh oocytes. This study sought to optimize the survival and cryopreservation of VT oocytes for SCNT. Co-culture with feeder cells that had been preincubated for 15 h significantly improved the survival of VT oocytes and their in vitro developmental potential following SCNT in comparison to co-cultu ...[more]

PMID: 25984830

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Project description:Since the first cloned animal Dolly Sheep was successfully created by using somatic cell nuclear transfer(SCNT) technique. It has become an irreplaceable tool to understand nuclear reprogramming and totipotency and holds huge potentials for regenerative medicine. However, extremely poor development rate of SCNT embryos indicates it is still questionable. The nature of reprogramming oocyte factors and their mechanism of action remain largely unknown.It is evident that the major barrier that hinders the developing iSCNT embryo mainly appears at the time of embryonic genome activation (EGA), which primarily occurs at the eight-cell stage in mammalian. The interspecies somatic cell nuclear transfer (iSCNT) is desired model for nuclear reprogramming research and a powerful tool for discovering the master genome activation genes. In this study, a valuable transcriptome recourse of iSCNT embryos was established, which derived from more than 2000 clone embryos of four different inter-family donor cells. Based on weighted gene co-expression network (WGCNA) approach, we provide an extensive transcriptome analysis of differentially expressed genes(DEG) for iSCNT embryos. The total gene expression patterns of different iSCNT embryos were discussed. 26 cell-specific modules with were identified, and those module significance and GO enriched categories were analyzed. The regulatory pathways of reprogramming barriers were further enriched. As master genome trigger genes, the transcripts related to TFIID subunit, RNA polymerase and Mediator were incomplete activated in iSCNT embryos. This indicated that pioneer factors, present in the cytoplasm of the oocyte, were failed to bind the sequence target on the heterology nuclear genome. This genomic incompatibility between the nuclear donor cell and the cytoplast may be as a major contributing factor causes the developmental failure of iSCNT cloned embryos. This study demonstrates that the iSCNT embryos undergoes only partial or incomplete reprogramming at eight-cell stage in mammalian. Our results offered convincing evidence that the abnormal expression of key master pathways may be caused the embryo developmental block of cloning embryo. This work will contribute to a better understanding of the molecular interaction between nuclear–cytoplasmic interaction and provides insight into the molecular determinants of nuclear reprogramming, human embryonic stem cell (hESC)-based therapies and rescuing highly endangered species.

Project description:Study questionDoes the use of a new cryoprotectant agent (CPA) exchange protocol designed to minimize osmotic stress improve oocyte or zygote vitrification by reducing sublethal cryodamage?Summary answerThe use of a new CPA exchange protocol made possible by automated microfluidics improved oocyte and zygote vitrification with superior morphology as indicated by a smoother cell surface, higher sphericity, higher cytoplasmic lipid retention, less cytoplasmic leakage and higher developmental competence compared with conventional methods.What is known alreadyThe use of more 'steps' of CPA exposure during the vitrification protocol increases cryosurvival and development in the bovine model. However, such an attempt to eliminate osmotic stress is limited by the practicality of performing numerous precise pipetting steps in a short amount of time.Study design, size, durationMurine meiotically competent germinal vesicle intact oocytes and zygotes were harvested from the antral follicles in ovaries and ampulla, respectively. Bovine ovaries were obtained from a local abattoir at random stages of the estrous cycle. A total of 110 murine oocytes, 802 murine zygotes and 52 bovine oocytes were used in this study.Participants/materials, setting, methodsMicrofluidic devices were fabricated using conventional photo- and soft-lithography. CPAs used were 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for equilibration solution and 15% EG, 15% DMSO and 0.5 M sucrose for vitrification solution. End-point analyses include mathematical modeling using Kedem-Katchalsky equations, morphometrics assessed by conventional and confocal microscopy, cytoplasmic lipid quantification by nile red staining, cytoplasmic leakage quantification by fluorescent dextran intercalation and developmental competence analysis by 96 h embryo culture and blastomere quantification.Main results and the role of chanceThe automated microfluidics protocol decreased the shrinkage rate of the oocyte and zygote by 13.8 times over its manual pipetting alternative. Oocytes and zygotes with a lower shrinkage rate during CPA exposure experienced less osmotic stress resulting in better morphology, higher cell quality and improved developmental competence. This microfluidic procedure resulted in murine zygotes with a significantly smoother cell surface (P < 0.001), more spherical cellular morphology (P < 0.001), increased cytoplasmic lipid retention in vitrified and warmed bovine oocytes (P < 0.01), decreased membrane perforations and cytoplasmic leakage in CPA-exposed murine zygotes (P < 0.05) and improved developmental competence of vitrified and warmed murine zygotes (P < 0.05) than CPA exposure using the current clinically used manual pipetting method.Limitations, reasons for cautionIt is necessary to design the microfluidic device to be more user-friendly for widespread use.Wider implications of the findingsThe theory and approach of eliminating osmotic stress by decreasing shrinkage rate is complementary to the prevalent osmotic stress theory in cryobiology which focuses on a minimum cell volume at which the cells shrink. The auto-microfluidic protocol described here has immediate applications for improving animal and human oocyte, zygote and embryo cryopreservation. On a fundamental level, the clear demonstration that at the same minimum cell volume, cell shrinkage rate affects sublethal damage should be broadly useful for cryobiology.Study funding/competing interestsThis project was funded by the National Institutes of Health and the University of Michigan Reproductive Sciences Program. The authors declare no conflicts of interest.

Dataset Information

Effective Oocyte Vitrification and Survival Techniques for Bovine Somatic Cell Nuclear Transfer.

Publications

Effective Oocyte Vitrification and Survival Techniques for Bovine Somatic Cell Nuclear Transfer.

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