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Energy is crucial to the development of human civilization. Energy infrastructure, such as oil and gas pipelines, power generation systems, and storage facilities, provide core support for the exploitation and utilization of various types of energy. Thus, energy infrastructure is vital to the economic sustainable development of a country. This paper provides the motivations and a brief introduction to the Special Issue entitled “Frontiers in Construction Technology of Advanced Energy Infrastructure”, which aims to present advanced technologies and theories for energy infrastructure. The primary challenges in the current construction technology of energy infrastructure are described. Furthermore, the focus of current research in this field addressed in this Special Issue is presented. A comparison of the articles included or considered for inclusion in this Special Issue with other available literature on this topic is performed, which proves the prospects and relevance of this Special Issue. Finally, perspectives on future directions of energy utilization and energy infrastructure construction are provided.

N 6 -methyladenosine (m 6 A) has been demonstrated to regulate RNA metabolism and various biological processes, including gametogenesis and embryogenesis. However, the landscape and function of m 6 A at single cell resolution have not been extensively studied in mammalian oocytes or during pre-implantation. In this study, we developed a single-cell m 6 A sequencing (scm 6 A-seq) method to simultaneously profile the m 6 A methylome and transcriptome in single oocytes/blastomeres of cleavage-stage embryos. We found that m 6 A deficiency leads to aberrant RNA clearance and consequent low quality of Mettl3 Gdf9 conditional knockout (cKO) oocytes. We further revealed that m 6 A regulates the translation and stability of modified RNAs in metaphase II (MII) oocytes and during oocyte-to-embryo transition, respectively. Moreover, we observed m 6 A-dependent asymmetries in the epi-transcriptome between the blastomeres of two-cell embryo. scm 6 A-seq thus allows in-depth investigation into m 6 A characteristics and functions, and the findings provide invaluable single-cell resolution resources for delineating the underlying mechanism for gametogenesis and early embryonic development. Modification of RNA with N6-methyladenosine can regulate RNA metabolism. Here they developed scm 6 A-seq to profile the methylome and transcriptome in single cells, and reveal the functions of m 6 A modification during oocyte maturation and early embryo development.

Tbx3 boosts iPS quality While much attention has been given to the study of different genetic and chemical methods for the generation of iPS (induced pluripotent stem) cell lines, relatively little is known about the variability in overall quality of iPS cells. This paper identifies a transcription factor, Tbx3, that significantly improves the quality of iPS cells. Tbx3 also accelerates the reprogramming process of mouse embryonic fibroblasts into iPS cells and significantly improves the germ-line transmission of iPS-derived germ cells in chimaeric animals. The transcription factor Tbx3 is shown to significantly improve the quality of induced pluripotent stem (iPS) cells. Tbx3 binding sites in embryonic stem cells are present in genes involved in pluripotency and reprogramming factors. Furthermore, there are intrinsic qualitative differences in iPS cells generated by different methods in terms of their pluripotency, thus highlighting the need to rigorously characterize iPS cells beyond in vitro studies. Induced pluripotent stem (iPS) cells can be obtained by the introduction of defined factors into somatic cells 1 . The combination of Oct4 (also known as Pou5f1), Sox2 and Klf4 (which we term OSK) constitutes the minimal requirement for generating iPS cells from mouse embryonic fibroblasts. These cells are thought to resemble embryonic stem cells (ESCs) on the basis of global gene expression analyses; however, few studies have tested the ability and efficiency of iPS cells to contribute to chimaerism, colonization of germ tissues, and most importantly, germ-line transmission and live birth from iPS cells produced by tetraploid complementation. Using genomic analyses of ESC genes that have roles in pluripotency and fusion-mediated somatic cell reprogramming, here we show that the transcription factor Tbx3 significantly improves the quality of iPS cells. iPS cells generated with OSK and Tbx3 (OSKT) are superior in both germ-cell contribution to the gonads and germ-line transmission frequency. However, global gene expression profiling could not distinguish between OSK and OSKT iPS cells. Genome-wide chromatin immunoprecipitation sequencing analysis of Tbx3-binding sites in ESCs suggests that Tbx3 regulates pluripotency-associated and reprogramming factors, in addition to sharing many common downstream regulatory targets with Oct4, Sox2, Nanog and Smad1. This study underscores the intrinsic qualitative differences between iPS cells generated by different methods, and highlights the need to rigorously characterize iPS cells beyond in vitro studies.

Telomere reprogramming and silencing of exogenous genes have been demonstrated in mouse and human induced pluripotent stem cells (iPS cells). Pigs have the potential to provide xenotransplant for humans, and to model and test human diseases. We investigated the telomere length and maintenance in porcine iPS cells generated and cultured under various conditions. Telomere lengths vary among different porcine iPS cell lines, some with telomere elongation and maintenance, and others telomere shortening. Porcine iPS cells with sufficient telomere length maintenance show the ability to differentiate in vivo by teratoma formation test. IPS cells with short or dysfunctional telomeres exhibit reduced ability to form teratomas. Moreover, insufficient telomerase and incomplete telomere reprogramming and/or maintenance link to sustained activation of exogenous genes in porcine iPS cells. In contrast, porcine iPS cells with reduced expression of exogenous genes or partial exogene silencing exhibit insufficient activation of endogenous pluripotent genes and telomerase genes, accompanied by telomere shortening with increasing passages. Moreover, telomere doublets, telomere sister chromatid exchanges and t-circles that presumably are involved in telomere lengthening by recombination also are found in porcine iPS cells. These data suggest that both telomerase-dependent and telomerase-independent mechanisms are involved in telomere reprogramming during induction and passages of porcine iPS cells, but these are insufficient, resulting in increased telomere damage and shortening, and chromosomal instability. Active exogenes might compensate for insufficient activation of endogenous genes and incomplete telomere reprogramming and maintenance of porcine iPS cells. Further understanding of telomere reprogramming and maintenance may help improve the quality of porcine iPS cells.

Cultured meat production has emerged as a breakthrough technology for the global food industry with the potential to reduce challenges associated with environmental sustainability, global public health, animal welfare, and competition for food between humans and animals. The muscle stem cell lines currently used for cultured meat cannot be passaged in vitro for extended periods of time. Here, we develop a directional differentiation system of porcine pre-gastrulation epiblast stem cells (pgEpiSCs) with stable cellular features and achieve serum-free myogenic differentiation of the pgEpiSCs. We show that the pgEpiSCs-derived skeletal muscle progenitor cells and skeletal muscle fibers have typical muscle cell characteristics and display skeletal muscle transcriptional features during myogenic differentiation. Importantly, we establish a three-dimensional differentiation system for shaping cultured tissue by screening plant-based edible scaffolds of non-animal origin, followed by the generation of pgEpiSCs-derived cultured meat. These advances provide a technical approach for the development of cultured meat. Cultured meat technology promises to alleviate protein shortages, but still faces many challenges. Here, the authors achieve serum-free myogenic differentiation of porcine pre-gastrulation epiblast stem cells and generate meat-like tissue via edible plant-based scaffolds without any animal compounds.

Cultured meat needs edible bio-scaffolds that provide not only a growth milieu for muscle and adipose cells, but also biomimetic stiffness and tissue-sculpting topography. Current meat-engineering technologies struggle to achieve scalable cell production, efficient cell differentiation, and tissue maturation in one single culture system. Here we propose an autoclaving strategy to transform common vegetables into muscle- and adipose-engineering scaffolds, without undergoing conventional plant decellularization. We selected vegetables with natural anisotropic and isotropic topology mimicking muscle and adipose microstructures respectively. We further adjusted vegetable stiffness by autoclaving, to emulate the mechanical properties of animal tissues. Autoclaved vegetables preserve rich cell-affinitive moieties, yielding a good cell culture effect with simplified processing. Autoclaved Chinese chive and Shiitake mushroom with anisotropic micro-patterns support the scalable expansion of muscle cells, improved cell alignment and myogenesis. Autoclaved isotropic loofah encourages adipocyte proliferation and lipid accumulation. Our engineered muscle- and fat-on-vegetables can further construct meat stuffing or layered meat chips. Autoclaved vegetables possess tissue-mimicking stiffness and topology, and bring biochemical benefits, operational ease, cost reduction and bioreactor compatibility. Without needing decellularization, these natural biomaterials may see scale-up applications in meat analog bio-fabrication. Traditional cultured meat scaffolds employ animal-derived biomaterials or intricate manufacturing, but plant-based scaffolds offer an appealing alternative. Here the authors present a simple shortcut method to transform common vegetables into edible bioscaffolds via autoclaving, which mimics meat stiffness and microstructure.

Spatially ordered embryo-like structures self-assembled from blastocyst-derived stem cells can be generated to mimic embryogenesis in vitro. However, the assembly system and developmental potential of such structures needs to be further studied. Here, we devise a nonadherent-suspension-shaking system to generate self-assembled embryo-like structures (ETX-embryoids) using mouse embryonic, trophoblast and extra-embryonic endoderm stem cells. When cultured together, the three cell types aggregate and sort into lineage-specific compartments. Signaling among these compartments results in molecular and morphogenic events that closely mimic those observed in wild-type embryos. These ETX-embryoids exhibit lumenogenesis, asymmetric patterns of gene expression for markers of mesoderm and primordial germ cell precursors, and formation of anterior visceral endoderm-like tissues. After transplantation into the pseudopregnant mouse uterus, ETX-embryoids efficiently initiate implantation and trigger the formation of decidual tissues. The ability of the three cell types to self-assemble into an embryo-like structure in vitro provides a powerful model system for studying embryogenesis. The precise cellular patterning and decisions of early embryogenesis have been hard to mimic in vitro. Here, the authors culture murine embryonic and trophoblast stem cells together with extra-embryonic endoderm stem cells to form embryo-like structures (ETX-embryoids), which can initiate an implantation response.

Preimplantation embryos undergo zygotic genome activation and lineage specification resulting in three distinct cell types in the late blastocyst. The molecular mechanisms underlying this progress are largely unknown in bovines. Here, we sought to analyze an extensive set of regulators at the single-cell level to define the events involved in the development of the bovine blastocyst. Using a quantitative microfluidics approach in single cells, we analyzed mRNA levels of 96 genes known to function in early embryonic development and maintenance of stem cell pluripotency in parallel in 384 individual cells from bovine preimplantation embryos. The developmental transitions can be distinguished by distinctive gene expression profiles and we identified NOTCH1, expressed in early developmental stages, while T-box 3 (TBX3) and fibroblast growth factor receptor 4 (FGFR4), expressed in late developmental stages. Three lineages can be segregated in bovine expanded blastocysts based on the expression patterns of lineage-specific genes such as disabled homolog 2 (DAB2), caudal type homeobox 2 (CDX2), ATPase H+/K+ transporting non-gastric alpha2 subunit (ATP12A), keratin 8 (KRT8), and transcription factor AP-2 alpha (TFAP2A) for trophectoderm; GATA binding protein 6 (GATA6) and goosecoid homeobox (GSC) for primitive endoderm; and Nanog homeobox (NANOG), teratocarcinoma-derived growth factor 1 (TDGF1), and PR/SET domain 14 (PRDM14) for epiblast. Moreover, some lineage-specific genes were coexpressed in blastomeres from the morula. The commitment to trophectoderm and inner cellmass lineages in bovines occurs later than in the mouse, and KRT8 might be an earlier marker for bovine trophectoderm cells. We determined that TDGF1 and PRDM14 might play pivotal roles in the primitive endoderm and epiblast specification of bovine blastocysts. Our results shed light on early cell fate determination in bovine preimplantation embryos and offer theoretical support for deriving bovine embryonic stem cells. Summary Sentence Gene expression analysis of single blastomeres from zygote to blastocyst sheds light on the early cell fate determination in bovine preimplantation embryos and offers theoretical support for deriving bovine embryonic stem cells.

Microbially induced carbonate precipitation (MICP) has been utilized as a new method to improve loess soil strength. In this study, we investigated the influence of the main parameters on the shear strength of MICP-treated loess specimens. Initially, culture media with different formulas and pH values were examined to identify the most efficient medium for loess soil. To explore the shear behavior of MICP-treated loess under general stress levels, unconfined compressive strength (UCS) tests and triaxial tests relevant to the compression strength and vertical loads were performed on MICP-treated loess with different calcium sources, cementation concentrations, and curing periods. Subsequently, calcium chloride was selected as the optimal calcium source based on the ultimate strength of the MICP-treated loess. The effective cementation concentration in the loess soil was between 1.0 and 1.25 M. The ultimate strength of the MICP-treated loess was 3.6 times of the untreated loess. The stress-strain curves indicate that a higher cementing effect can be expected with an increase in the curing period. The formation process of calcium carbonate and the micromorphology of the MICP-treated loess samples were examined using scanning electron microscopy. In this study, we present an environmentally friendly technique for improving loess soil strength.

In the process of long-distance and large-diameter pipe jacking, thixotropic mud is generally injected into the outer surface of the pipe wall to reduce the frictional resistance between the pipe and the soil. The process of pipe jacking may be stopped due to various reasons such as pipe rupture and equipment damage. When the pipe is restarted after being stopped for a period of time, the interface mechanical properties usually change substantially, resulting in a substantial increase in frictional resistance compared to before the stop. However, the mechanical properties and shear mechanism of the pipe-soil interface after jacking is restarted have not been sufficiently investigated. In this paper, a series of gravelly sand-concrete direct shear tests are carried out, in which lubricant is injected into the interface between gravelly sand and concrete, and the effect of construction stagnation time is considered. The mechanical properties of the interface when the concrete pipe is restarted after stagnation is studied by the direct shear tests. The results show that the friction coefficient of pipe-soil interface increases with the stagnation time, which is determined by the thixotropic mud state and the content of gravelly sand involved in shear. In a short period of stagnation, the friction coefficient is determined by the cohesion caused by thixotropic mud and the friction angle produced by the gravelly sand involved in the shearing action. With the increase of stagnation time, the friction angle gradually becomes the decisive factor for the increase of friction coefficient.