Functional consequences of mitochondrial mismatch in reconstituted embryos and offspring

The effect of L-carnitine supplementation during in vitro maturation on oocyte maturation and somatic cloned embryo development

The quality of the recipient cytoplasm was reported as a crucial factor in maintaining the vitality of SCNT embryos and SCNT efficiency for dairy cows. Compared with oocytes matured in vivo, oocytes matured in vitro showed abnormal accumulation and metabolism of cytoplasmic lipids. L-carnitine treatment was found to control fatty acid transport into the mitochondrial β-oxidation pathway, which improved the process of lipid metabolism. The results of this study show that 0.5 mg/ml L-carnitine significantly reduced the cytoplasmic lipid content relative to control. No significant difference was observed in the rate of oocyte nuclear maturation, but the in vitro developmental competence of SCNT embryos was improved in terms of increased blastocyst production and lower apoptotic index in the L-carnitine treatment group. In addition, the pregnancy rate with SCNT embryos in the treatment group was significantly higher than in the control group. In conclusion, the present study demonstrated that adding L-carnitine to the maturation culture medium could improve the developmental competence of SCNT embryos both in vitro and in vivo by reducing the lipid content of the recipient cytoplasm.

Cloning in action: can embryo splitting, induced pluripotency and somatic cell nuclear transfer contribute to endangered species conservation?

The term 'cloning' refers to the production of genetically identical individuals but has meant different things throughout the history of science: a natural means of reproduction in bacteria, a routine procedure in horticulture, and an ever-evolving gamut of molecular technologies in vertebrates. Mammalian cloning can be achieved through embryo splitting, somatic cell nuclear transfer, and most recently, by the use of induced pluripotent stem cells. Several emerging biotechnologies also facilitate the propagation of genomes from one generation to the next whilst bypassing the conventional reproductive processes. In this review, we examine the state of the art of available cloning technologies and their progress in species other than humans and rodent models, in order to provide a critical overview of their readiness and relevance for application in endangered animal conservation.

Treatments of Porcine Nuclear Recipient Oocytes and Somatic Cell Nuclear Transfer-Generated Embryos with Various Reactive Oxygen Species Scavengers Lead to Improvements of Their Quality Parameters and Developmental Competences by Mitigating Oxidative Stress-Related Impacts

This study investigated the antioxidant effects of β-cryptoxanthin (BCX), hesperetin (HES), and icariin (ICA), and their effects on in vitro maturation of porcine oocytes and subsequent embryonic development of somatic cell nuclear transfer (SCNT). Treatment with 1 μM BCX (BCX-1) increased the developmental rate of porcine oocytes more than treatment with 100 μM HES (HES-100) or 5 μM ICA (ICA-5). The glutathione level and mRNA expression of antioxidant genes (NFE2L2, SOD1, and SOD2) were more increased in the BCX-1 group than in the HES-100 and ICA-5 groups, while the reactive oxygen species level was more decreased. Moreover, BCX improved the developmental capacity and quality of SCNT embryos. The total cell number, apoptotic cell rate, and development-related gene expression were modulated in the BCX-1 group to enhance embryonic development of SCNT. These results show that the antioxidant effects of BCX enhance in vitro maturation of porcine oocytes and subsequent embryonic development of SCNT.

Mitochondrial Inheritance Following Nuclear Transfer: From Cloned Animals to Patients with Mitochondrial Disease

Mitochondria are indispensable power plants of eukaryotic cells that also act as a major biochemical hub. As such, mitochondrial dysfunction, which can originate from mutations in the mitochondrial genome (mtDNA), may impair organism fitness and lead to severe diseases in humans. MtDNA is a multi-copy, highly polymorphic genome that is uniparentally transmitted through the maternal line. Several mechanisms act in the germline to counteract heteroplasmy (i.e., coexistence of two or more mtDNA variants) and prevent expansion of mtDNA mutations. However, reproductive biotechnologies such as cloning by nuclear transfer can disrupt mtDNA inheritance, resulting in new genetic combinations that may be unstable and have physiological consequences. Here, we review the current understanding of mitochondrial inheritance, with emphasis on its pattern in animals and human embryos generated by nuclear transfer.

Resurrecting biodiversity: advanced assisted reproductive technologies and biobanking

Biodiversity is defined as the presence of a variety of living organisms on the Earth that is essential for human survival. However, anthropogenic activities are causing the sixth mass extinction, threatening even our own species. For many animals, dwindling numbers are becoming fragmented populations with low genetic diversity, threatening long-term species viability. With extinction rates 1000–10,000 times greater than natural, ex situ and in situ conservation programmes need additional support to save species. The indefinite storage of cryopreserved (−196°C) viable cells and tissues (cryobanking), followed by assisted or advanced assisted reproductive technology (ART: utilisation of oocytes and spermatozoa to generate offspring; aART: utilisation of somatic cell genetic material to generate offspring), may be the only hope for species’ long-term survival. As such, cryobanking should be considered a necessity for all future conservation strategies. Following cryopreservation, ART/aART can be used to reinstate lost genetics back into a population, resurrecting biodiversity. However, for this to be successful, species-specific protocol optimisation and increased knowledge of basic biology for many taxa are required. Current ART/aART is primarily focused on mammalian taxa; however, this needs to be extended to all, including to some of the most endangered species: amphibians. Gamete, reproductive tissue and somatic cell cryobanking can fill the gap between losing genetic diversity today and future technological developments. This review explores species prioritisation for cryobanking and the successes and challenges of cryopreservation and multiple ARTs/aARTs. We here discuss the value of cryobanking before more species are lost and the potential of advanced reproductive technologies not only to halt but also to reverse biodiversity loss.

The Molecular Quality and Mitochondrial Activity of Porcine Cumulus-Oocyte Complexes Are Affected by Their Exposure to Three Endocrine-Active Compounds under 3D In Vitro Maturation Conditions

Thus far, the potential short- and long-term detrimental effects of a variety of environmental chemicals designated as endocrine-active compounds (EACs) have been found to interfere with histo- and anatomo-physiological functions of the reproductive system in humans and wildlife species. For those reasons, this study sought to examine whether selected EACs, which encompass the fungicide vinclozolin (Vnz), the androgenic anabolic steroid nandrolone (Ndn) and the immunosuppressant cyclosporin A (CsA), affect the developmental competence and molecular quality (MQ) of porcine cumulus–oocyte complexes (COCs) subjected to in vitro maturation (IVM) under 3D culture conditions. The COCs underwent 3D-IVM in the presence of Vnz, Ndn or CsA for 48 h. To explore whether the selected EACs induce internucleosomal DNA fragmentation in cumulus cells (CCs), TUNEL-assisted detection of late apoptotic cells was performed. Additionally, for the detailed evaluation of pro- and antiapoptotic pathways in COCs, apoptosis proteome profiler arrays were used. To determine changes in intracellular metabolism in COCs, comprehensive assessments of mitochondrial ultrastructure and activity were carried out. Moreover, the relative abundances (RAs) of mRNAs transcribed from genes that are involved in scavenging reactive oxygen species (ROS), such as SIRT3 and FOXO3, and intramitochondrial bioenergetic balance, such as ATP synthase subunit (ATP5A1), were ascertained. Finally, to investigate the extent of progression of oocyte maturation, the intraooplasmic levels of cAMP and the RAs of mRNA transcripts encoding regulatory and biocatalytic subunits of a heterodimeric meiosis-promoting factor, termed cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2), were also estimated. The obtained results provide, for the first time, strong evidence that both Vnz and Ndn decrease the developmental competence of oocytes and stimulate apoptosis processes in CCs. The present study is also the first to highlight that Vnz accelerates the maturation process in immature oocytes due to both increased ROS production and the augmented RA of the CCNB1 gene. Furthermore, Vnz was proven to trigger proapoptotic events in CCs by prompting the activity of the FOXO3 transcription factor, which regulates the mitochondrial apoptosis pathway. In turn, Ndn was shown to inhibit oocyte maturation by inducing molecular events that ultimately lead to an increase in the intraooplasmic cAMP concentration. However, due to the simultaneous enhancement of the expression of TNF-β and HSP27 proteins in CCs, Ndn might be responsible for the onset of their neoplastic transformation. Finally, our current investigation is the first to clearly demonstrate that although CsA did not interfere with the nuclear and cytoplasmic maturation of oocytes, by inducing mitophagy in CCs, it disrupted oocyte metabolism, consequently attenuating the parameters related to the MQ of COCs. Summing up, Vnz, Ndn and CsA reduced not only the processes of growth and IVM but also the MQ of porcine COCs, which might make them unsuitable for assisted reproductive technologies (ARTs) such as in vitro fertilization by either gamete co-incubation or intracytoplasmic sperm injection (ICSI) and cloning by somatic cell nuclear transfer (SCNT).

Ex Situ Conservation and Genetic Rescue of Endangered Polish Cattle and Pig Breeds with the Aid of Modern Reproductive Biotechnology – A Review

The development and optimization of reproductive biotechnology – specifically semen cryopreservation, spermatological diagnostics, and intraspecies cloning by somatic cell nuclear transfer (SCNT) – have become essential techniques to conserve the genetic resources and establish genetic reserves of endangered or vanishing native Polish livestock breeds. Moreover, this biotechnology is necessary for perpetuating biological diversity and enhancing genetic variability as well as for restoring and reintroducing breeds into anthropogenic agricultural ecosystems. On the one hand, the purpose of our paper is to interpret recent efforts aimed at the ex situ conservation of native cattle and pig breeds. On the other, it emphasizes the prominent role played by the National Research Institute of Animal Production (NRIAP) in maintaining biodiversity in agricultural environmental niches. Furthermore, our paper provides an overview of the conventional and modern strategies of the banking and cryopreservation of germplasm-carrier biological materials and somatic cell lines, spermatological diagnostics, and semen-based and SCNT-mediated assisted reproductive technologies (ART s). These are the most reliable and powerful tools for ex situ protection of the genetic resources of endangered breeds of livestock, especially cattle and pigs.

The Resurrection of Mabrokan: Production of Multiple Cloned Offspring from Decade-Old Vitrified Tissue Collected from a Deceased Champion Show Camel

Somatic cell nuclear transfer (SCNT) provides a unique opportunity to reproduce animals with superior genetics. Viable cell lines are usually established from tissues collected by biopsy from living animals in the SCNT program. In the present study, tissues were collected and preserved from a suddenly deceased champion camel. We established cell lines from these decade-old tissues and used them as nuclear donors. After 42 h of in vitro maturation, 68.00 ± 2.40% of oocytes reached the metaphase II (M II) stage while 87.31 ± 2.57% in vivo collected oocytes were matured at collection (p < 0.05). We observed a higher blastocyst formation rate when in vivo matured oocytes (43.45 ± 2.07%) were used compared to in vitro matured oocytes (21.52 ± 1.74%). The live birth rate was 6.45% vs. 16.67% for in vitro and in vivo matured oocytes, respectively. Microsatellite analysis of 13 camel loci revealed that all the SCNT-derived offspring were identical to each other and with their somatic cell donor. The present study succeeded in the resurrection of 11 healthy offspring from the decade-old vitrified tissues of a single somatic cell donor individual using both in vitro and in vivo matured oocytes.

Genome stabilization by RAD51-stimulatory compound 1 enhances efficiency of somatic cell nuclear transfer-mediated reprogramming and full-term development of cloned mouse embryos

OBJECTIVES

The genetic instability and DNA damage arise during transcription factor-mediated reprogramming of somatic cells, and its efficiency may be reduced due to abnormal chromatin remodelling. The efficiency in somatic cell nuclear transfer (SCNT)-mediated reprogramming is also very low, and it is caused by development arrest of most reconstituted embryos.

MATERIALS AND METHODS

Whether the repair of genetic instability or double-strand breaks (DSBs) during SCNT reprogramming may play an important role in embryonic development, we observed and analysed the effect of Rad 51, a key modulator of DNA damage response (DDR) in SCNT-derived embryos.

RESULTS

Here, we observed that the activity of Rad 51 is lower in SCNT eggs than in conventional IVF and found a significantly lower level of DSBs in SCNT embryos during reprogramming. To address this difference, supplementation with RS-1, an activator of Rad51, during the activation of SCNT embryos can increase RAD51 expression and DSB foci and thereby increased the efficiency of SCNT reprogramming. Through subsequent single-cell RNA-seq analysis, we observed the reactivation of a large number of genes that were not expressed in SCNT-2-cell embryos by the upregulation of DDR, which may be related to overcoming the developmental block. Additionally, there may be an independent pathway involving histone demethylase that can reduce reprograming-resistance regions.

CONCLUSIONS

This technology can contribute to the production of comparable cell sources for regenerative medicine.

Inhibition of Suv39h1/2 expression improves the early development of Debao porcine somatic cell nuclear transfer embryos

Suppressor of variegation 3-9 homolog (Suv39h)1 and 2, Histone H3 lysine 9 trimethylation (H3K9me3)-specific methyltransferases, are mainly involved in regulating the dynamic changes of H3K9me3. Regulating Suv39h expression influences the early development of mice somatic cell nuclear transfer (SCNT) embryos, there are few reports concerning their features in domestic animals. The aim of the present study was to characterize the Suv39h function in early development of Debao porcine SCNT embryos. The global level of H3K9me3 and the expression profiles of Suv39h1/2 in porcine early embryos were analysed by immunohistochemistry and qRT-PCR methods, respectively. Their roles in cell proliferation and histone modification of Debao porcine foetal fibroblast cells (PFFs), and developmental competence of porcine SCNT embryos were investigated by shRNA technology. The methylation levels of H3K9me3 and the expression patterns of Suv39h1 and Suv39h2 were similar (p < .05), and both of them displayed higher levels in Debao porcine SCNT embryos compared with that in PA embryos. The global levels of H3K9me3 and the expressions of G9a, HDAC1 and DNMT1 were decreased by combined inhibition of Suv39h1 and Suv39h2 (p < .05), while the expression of HAT1 was increased (p < .05). Downregulation of Suv39h1/2 also promoted cell proliferation and resulted in a significant increase in the expression of CyclinA2, CyclinB and PCNA in PFFs (p < .05). Furthermore, the use of donor somatic nuclei which depleted H3K9me3 by inhibiting Suv39h1/2 expression markedly increased the cleavage rate, the blastocyst rate and the total cell number of blastocysts of Debao porcine SCNT embryos (p < .05). Altogether, the above results indicate that H3K9me3 levels and Suv39h1/2 expressions display similar patterns in porcine early embryo, and low levels of them are critical to cell proliferation of PFFs and early development of SCNT embryos.

Extranuclear Inheritance of Mitochondrial Genome and Epigenetic Reprogrammability of Chromosomal Telomeres in Somatic Cell Cloning of Mammals

The effectiveness of somatic cell nuclear transfer (SCNT) in mammals seems to be still characterized by the disappointingly low rates of cloned embryos, fetuses, and progeny generated. These rates are measured in relation to the numbers of nuclear-transferred oocytes and can vary depending on the technique applied to the reconstruction of enucleated oocytes. The SCNT efficiency is also largely affected by the capability of donor nuclei to be epigenetically reprogrammed in a cytoplasm of reconstructed oocytes. The epigenetic reprogrammability of donor nuclei in SCNT-derived embryos appears to be biased, to a great extent, by the extranuclear (cytoplasmic) inheritance of mitochondrial DNA (mtDNA) fractions originating from donor cells. A high frequency of mtDNA heteroplasmy occurrence can lead to disturbances in the intergenomic crosstalk between mitochondrial and nuclear compartments during the early embryogenesis of SCNT-derived embryos. These disturbances can give rise to incorrect and incomplete epigenetic reprogramming of donor nuclei in mammalian cloned embryos. The dwindling reprogrammability of donor nuclei in the blastomeres of SCNT-derived embryos can also be impacted by impaired epigenetic rearrangements within terminal ends of donor cell-descended chromosomes (i.e., telomeres). Therefore, dysfunctions in epigenetic reprogramming of donor nuclei can contribute to the enhanced attrition of telomeres. This accelerates the processes of epigenomic aging and replicative senescence in the cells forming various tissues and organs of cloned fetuses and progeny. For all the above-mentioned reasons, the current paper aims to overview the state of the art in not only molecular mechanisms underlying intergenomic communication between nuclear and mtDNA molecules in cloned embryos but also intrinsic determinants affecting unfaithful epigenetic reprogrammability of telomeres. The latter is related to their abrasion within somatic cell-inherited chromosomes.