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Synergistic Cryoprotection and Molecular Mechanisms of LEA Protein on Vitrification Cryopreservation of Human Oocytes

ABSTRACT: Vitrification cryopreservation of oocytes is an enabling technology for assisted reproductive technology. However, many factors in the vitrification process, such as the toxicity of cryoprotectant, osmotic stress, ice crystal formation during rewarming, will cause fatal damage to oocytes, thus affecting the embryo developmental potential and subsequent clinical outcomes. Therefore, oocyte vitrification still faces significant challenges. Recent studies have shown that LEA protein has the potential to improve oocyte cryopreservation, while the molecular mechanism by which it exerts protective effects is still unclear. Therefore, we have systematically investigated the effects of LEA proteins on the vitrification cryopreservation and their molecular mechanisms. Results revealed that the proteins improved the developmental potential of human oocytes following cryopreservation, mostly by downregulating FOS genes and reducing oxidative stress. Moreover, the synergistic cryoprotection of LEA proteins by inhibiting the formation of ice crystals was given full play. This study provides a new strategy for high-quality cryopreservation of human oocytes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE239302 | GEO | 2024/04/01

REPOSITORIES: GEO

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Project description:Vitrification is a method for long-term biological sample cryopreservation without causing intra- and extra-cellular ice formation. We recently established a novel closed vitrification system to cryopreserve mouse ovarian follicles. Using the 3D alginate hydrogel encapsulated in vitro follicle growth (eIVFG) method, we have demonstrated that compared to freshly-harvested follicles, vitrified follicles have normal follicle and oocyte reproductive outcomes. Our recent study further demonstrated the faithful preservation of molecular signatures of follicle-stimulating hormone (FSH)-stimulated follicle maturation in vitrified follicles. However, it is unknown whether ovulation, another crucial gonadotropin-dependent follicular event, and involved ovulatory gene regulatory pathways are well conserved in vitrified follicles. Fresh and vitrified follicles grown for 8 days by eIVFG were collected at 0, 1, 4 and 8-hour post human chorionic gonadotropin (hCG) treatment for the single-follicle RNA sequencing. Principal component analysis (PCA) and Pearson’s correlation analysis revealed that vitrified follicles have similar transcriptomic profiles to fresh follicles. Furthermore, the expression of several genes essential for ovulation were comparable between vitrified and fresh follicles. In summary, these results demonstrate that our closed vitrification system preserves follicular transcriptomic dynamics during ex vivo ovulation. Together with our previous findings that vitrification preserves FSH-stimulated follicle maturation, the integration of vitrification of immature follicles and eIVFG has a great potential to serve as an additional fertilization preservation approach for young cancer patients and endangerers species. Moreover, follicle vitrification enables a high-content ovarian follicle biobank, which can greatly improve the throughput of eIVFG for studying ovulation biology, anovulatory disease, toxicology, and novel contraceptive drug development targeting ovulation.

Project description:Study question: Does storage time impact on transcriptome of slowly frozen cryopreserved human metaphase II (MII) oocytes? Summary answer: For the first time, we demonstrate that the length of cryostorage has no effect on the gene expression profile of human metaphase II oocytes. What is known already: Oocyte cryopreservation is a largely-used technique in IVF for storage of surplus oocytes, as well as for fertility preservation (i.e., women undergoing gonadotoxic therapies) and oocyte donation programs. Although it is known that cryopreservation negatively impacts on oocyte physiology and it is associated with decrease of transcripts, no experimental data about the effect of storage time on the oocyte molecular profile are available to date. Study design, size, duration: This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed. Participants/materials, setting, methods: Pools of ?10 oocytes for each group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on 4x44K v2 microarrays (Agilent). Analyses were performed by R v3.1.3 software using the limma package v3.22.7. Main results and the role of chance: Comparison of gene expression profiles between surviving thawed oocytes after 3 and 6 years of storage in liquid nitrogen found no differently expressed genes. The expression profiles of cryopreserved MII oocytes significantly differed from those of non-cryopreserved oocytes in 107 probe sets corresponding to 73 down-regulated and 29 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that cryopreservation deregulates genes involved in oocyte function and early embryo development, such as chromosome organization, RNA splicing and processing, cell cycle process, response to DNA damage stimulus, cellular response to stress and DNA repair, calcium ion binding, malate dehydrogenase activity, mitochondrial membrane respiratory chain. Among the probes significantly up-regulated in cryopreserved oocytes, 2 corresponded to ovary-specific expressed large intergenic noncoding (linc)RNAs. This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed.

Project description:Study question: Does storage time impact on transcriptome of slowly frozen cryopreserved human metaphase II (MII) oocytes? Summary answer: For the first time, we demonstrate that the length of cryostorage has no effect on the gene expression profile of human metaphase II oocytes. What is known already: Oocyte cryopreservation is a largely-used technique in IVF for storage of surplus oocytes, as well as for fertility preservation (i.e., women undergoing gonadotoxic therapies) and oocyte donation programs. Although it is known that cryopreservation negatively impacts on oocyte physiology and it is associated with decrease of transcripts, no experimental data about the effect of storage time on the oocyte molecular profile are available to date. Study design, size, duration: This study included 27 women undergoing IVF treatment, < 38 years aged, without any ovarian pathology. Surplus MII oocytes were donated after written informed consent. A total of 31 non-cryopreserved oocytes and 68 surviving slow-frozen/rapid-thawed oocytes (32 oocytes cryostored for 3 years and 36 cryostored for 6 years) were analyzed. Participants/materials, setting, methods: Pools of ≈10 oocytes for each group were prepared. Total RNA was extracted from each pool, amplified, labeled and hybridized on 4x44K v2 microarrays (Agilent). Analyses were performed by R v3.1.3 software using the limma package v3.22.7. Main results and the role of chance: Comparison of gene expression profiles between surviving thawed oocytes after 3 and 6 years of storage in liquid nitrogen found no differently expressed genes. The expression profiles of cryopreserved MII oocytes significantly differed from those of non-cryopreserved oocytes in 107 probe sets corresponding to 73 down-regulated and 29 up-regulated unique transcripts. Gene Ontology analysis by DAVID bioinformatics resource disclosed that cryopreservation deregulates genes involved in oocyte function and early embryo development, such as chromosome organization, RNA splicing and processing, cell cycle process, response to DNA damage stimulus, cellular response to stress and DNA repair, calcium ion binding, malate dehydrogenase activity, mitochondrial membrane respiratory chain. Among the probes significantly up-regulated in cryopreserved oocytes, 2 corresponded to ovary-specific expressed large intergenic noncoding (linc)RNAs.

Project description:Vitrification is a method for long-term biological sample cryopreservation that transforms cells into a glass-like state by cooling without causing intra- and extra-cellular ice formation, which is a major driver of cell cryoinjury. Using an alginate hydrogel encapsulated in vitro follicle growth (eIVFG) system, we have recently demonstrated that compared to freshly-harvested follicles, vitrified follicles have normal follicle and oocyte reproductive outcomes as well as comparable expression levels of several genes that are essential for gonadotropin-dependent folliculogenesis and oogenesis. However, it is unknown whether vitrification preserves the molecular signatures of folliculogenesis at the whole transcriptomic level, which is the primary research focus in this study. Multilayered secondary follicles with a diameter of 130 -160 µm were mechanically isolated from 16-day-old CD-1 female mice and vitrified using the closed vitrification method. After a 2-week storage in liquid nitrogen, vitrified follicles were warmed, and together with freshly-harvested follicles, cultured for 8 days using the eIVFG method. Next, mature antral follicles from day 8 were collected for single-follicle RNA sequencing using the SMART-seq RNA-seq method. Principal component analysis (PCA) and Pearson’s correlation analysis revealed that vitrified follicles have similar transcriptomic profiles to fresh follicles. Using the criterion of fold change >2 or <0.5 and a false discovery rate (FDR) adjusted p-value < 0.05, there were 35 differentially expressed genes out of a total of 11,806 detected genes between vitrified and fresh follicles, among which 17 were up-regulated and 18 were down-regulated in vitrified follicles. To the best of our knowledge, none of those differentially expressed genes identified between vitrified and fresh follicles have been shown to be critical to folliculogenesis and oogenesis. Meanwhile, gene ontology (GO) and KEGG pathway analysis over these 35 genes using the functional annotation tool DAVID revealed that no GO terms or signaling pathways were significantly enriched. Furthermore, the expression of several genes essential for the gonadotropin-dependent folliculogenesis and oogenesis were comparable between vitrified and fresh follicles, including granulosa cell-specific genes (Cyp19a1, Amh, Inha, Inhba, Inhbb, and Fshr), theca cell-specific genes (Cyp17a1, Col1a2, and Col3a1), and oocyte-specific genes (Gdf9, Bmp15, Zp1, Zp2, and Zp3). Equally important, Lhcgr, the gene that is primarily expressed in theca cells of preantral follicles and then greatly induced in mural granulosa cells in antral follicles to prepare for the luteinizing hormone (LH) surge and ovulation, also had comparable mRNA expression levels between vitrified and fresh follicles. Taken together, these results demonstrate that vitrification preserves the follicular cell transcriptome and molecular signatures of gonadotropin-dependent folliculogenesis in the eIVFG system. In conclusion, our study re-evaluates individual follicle cryopreservation by using the closed vitrification method in a more in-depth perspective and proves that vitrification preserves the follicular cell transcriptome in the eIVFG system, thus providing a robust model for fertility preservation, conservation of endangered species, and also establishing a high-content ovarian follicle biobank for studying ovarian biology and female reproductive toxicology.

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Synergistic Cryoprotection and Molecular Mechanisms of LEA Protein on Vitrification Cryopreservation of Human Oocytes

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