Reprogramming mechanism dissection and trophoblast replacement application in monkey somatic cell nuclear transfer

The Complexities of Interspecies Somatic Cell Nuclear Transfer: From Biological and Molecular Insights to Future Perspectives

For nearly three decades, interspecies somatic cell nuclear transfer (iSCNT) has been explored as a potential tool for cloning, regenerative medicine, and wildlife conservation. However, developmental inefficiencies remain a major challenge, largely due to persistent barriers in nucleocytoplasmic transport, mitonuclear communication, and epigenome crosstalk. This review synthesized peer-reviewed English articles from PubMed, Web of Science, and Scopus, spanning nearly three decades, using relevant keywords to explore the molecular mechanisms underlying iSCNT inefficiencies and potential improvement strategies. We highlight recent findings deepening the understanding of interspecies barriers in iSCNT, emphasizing their interconnected complexities, including the following: (1) nucleocytoplasmic incompatibility may disrupt nuclear pore complex (NPC) assembly and maturation, impairing the nuclear transport of essential transcription factors (TFs), embryonic genome activation (EGA), and nuclear reprogramming; (2) mitonuclear incompatibility could lead to nuclear and mitochondrial DNA (nDNA-mtDNA) mismatches, affecting electron transport chain (ETC) assembly, oxidative phosphorylation, and energy metabolism; (3) these interrelated incompatibilities can further influence epigenetic regulation, potentially leading to incomplete epigenetic reprogramming in iSCNT embryos. Addressing these challenges requires a multifaceted, species-specific approach that balances multiple incompatibilities rather than isolating a single factor. Gaining insight into the molecular interactions between the donor nucleus and recipient cytoplast, coupled with optimizing strategies tailored to specific pairings, could significantly enhance iSCNT efficiency, ultimately transforming experimental breakthroughs into real-world applications in reproductive biotechnology, regenerative medicine, and species conservation.

Towards Practical Conservation Cloning: Understanding the Dichotomy Between the Histories of Commercial and Conservation Cloning

Over 40 years ago, scientists imagined ways cloning could aid conservation of threatened taxa. The cloning of Dolly the sheep from adult somatic cells in 1996 was the breakthrough that finally enabled the conservation potential of the technology. Until the 2020s, conservation cloning research efforts yielded no management applications, leading many to believe cloning is not yet an effective conservation tool. In strong contrast, domestic taxa are cloned routinely for scientific and commercial purposes. In this review, we sought to understand the reasons for these divergent trends. We scoured peer-reviewed and gray literature and sent direct inquiries to scientists to analyze a more comprehensive history of the field than was analyzed in previous reviews. While most previous reviewers concluded that a lack of reproductive knowledge of wildlife species has hindered advances for wider conservation applications, we found that resource limitations (e.g., numbers of surrogates, sustainable funding) and widely held misconceptions about cloning are significant contributors to the stagnation of the field. Recent successes in cloning programs for the endangered black-footed ferret (Mustela nigripes) and Przewalski's horse (Equus przewalskii), the world's first true applied-conservation cloning efforts, are demonstrating that cloning can be used for significant conservation impact in the present. When viewed alongside the long history of cloning achievements, these programs emphasize the value of investing in the science and resources needed to meaningfully integrate cloning into conservation management, especially for species with limited genetic diversity that rely on the maintenance of small populations for many generations while conservationists work to restore habitat and mitigate threats in the wild.

Heterologous expression of bovine histone H1foo into porcine fibroblasts alters the transcriptome profile but not embryo development following nuclear transfer

PURPOSE

Somatic cell nuclear transfer (SCNT) is a valuable tool for investigating reprogramming mechanisms and creating animal clones for applications in production, conservation, companionship, and biomedical research. However, SCNT efficiency remains low. Expression of nuclear proteins associated with an undifferentiated chromatin state, such as the oocyte-specific variant of the linker histone H1 (H1foo), represents a strategy for improving reprogramming outcomes, but this approach has not been tested in the context of SCNT.

METHODS

Bovine H1foo (bH1foo) was transfected into porcine fibroblasts via electroporation for expression until SCNT. The transcriptomic profile of these cells was analyzed, and their potential as donor cells for SCNT was evaluated 48 h post-electroporation.

RESULTS

Strong nuclear localization of bH1foo persisted for 48 h post-electroporation. A total of 447 genes were differentially expressed, and lower levels of H3K4me3 and H3K27me3 were detected in bH1foo-expressing cells, indicating changes in chromatin remodeling and function. Embryo development and total cell number per blastocyst were similar between SCNT embryos produced with control and bH1foo-expressing cells. mRNA levels of genes involved in embryonic genome activation were comparable between embryos derived from control and bH1foo-expressing cells on days 3 and 4 of development, suggesting that bH1foo did not disrupt this critical process.

CONCLUSIONS

The heterologous expression of bovine H1foo altered the chromatin function of porcine fibroblasts without impairing development to the blastocyst stage following SCNT. These results highlight the potential of expressing nuclear proteins as a strategy to enhance cell reprogramming and cloning efficiency, including interspecies cloning applications.

The Mammalian Oocyte: A Central Hub for Cellular Reprogramming and Stemness

The mammalian oocyte is pivotal in reproductive biology, acting as a central hub for cellular reprogramming and stemness. It uniquely contributes half of the zygotic nuclear genome and the entirety of the mitochondrial genome, ensuring individual development and health. Oocyte-mediated reprogramming, exemplified by nuclear transfer, resets somatic cell identity to achieve pluripotency and has transformative potential in regenerative medicine. This process is critical for understanding cellular differentiation, improving assisted reproductive technologies, and advancing cloning and stem cell research. During fertilization, the maternal-zygotic transition shifts developmental control from maternal factors to zygotic genome activation, establishing totipotency. Oocytes also harbor reprogramming factors that guide nuclear remodeling, epigenetic modifications, and metabolic reprogramming, enabling early embryogenesis. Structures like mitochondria, lipid droplets, and cytoplasmic lattices contribute to energy production, molecular regulation, and cellular organization. Recent insights into oocyte components, such as ooplasmic nanovesicles and endolysosomal vesicular assemblies (ELVAS), highlight their roles in maintaining cellular homeostasis, protein synthesis, and reprogramming efficiency. By unraveling the reprogramming mechanisms inherent in oocytes, we advance our understanding of cloning, cell differentiation, and stem cell therapy, highlighting their valuable significance in developmental biology and regenerative medicine.

Molecular Mechanisms of Somatic Cell Cloning and Other Assisted Reproductive Technologies in Mammals: Which Determinants Have Been Unraveled Thus Far?-Current Status, Further Progress and Future Challenges

Taking into consideration recent reports on the successful creation of cloned rhesus monkeys [...].

Why non-human primates are needed in stroke preclinical research

Numerous seemingly promising cerebroprotectants previously validated in rodents almost all have failed in stroke clinical trials. The failure of clinical translation strikes an essential need to employ more ideal animal models in stroke research. Compared with the most commonly used rodent models of stroke, non-human primates (NHPs) are far more comparable to humans regarding brain anatomy, functionality and pathological features. The aim of this perspective was to summarise the advantages of NHPs stroke models over rodents, discuss the current limitations of NHPs models, and cast an outlook on the future development of NHPs in stroke preclinical research.

Genome-Scale Analyses Reveal Roadblocks to Monkey Cloning

Cloning by somatic cell nuclear transfer (SCNT) remained challenging for Rhesus monkeys, mostly due to its low efficiency and neonatal death. Genome-scale analyses revealed that monkey SCNT embryos displayed widespread DNA methylation and transcriptional alterations, thus including loss of genomic imprinting that correlated with placental dysfunction. The transfer of inner cell masses (ICM) from cloned blastocysts into ICM-depleted fertilized embryos rescued placental insufficiency and gave rise to a cloned Rhesus monkey that reached adulthood without noticeable abnormalities.

Advancing primatology through ethical and scientific perspectives on rhesus monkey (Macaca mulatta) cloning

A critical turning point was reached in research with the recent success in cloning rhesus monkeys (Macaca mulatta), a major advancement in primatology. This breakthrough marks the beginning of a new age in biomedical research, ushered by improved somatic cell nuclear transfer techniques and creative trophoblast replacement strategies. The successful cloning of rhesus monkeys presents the possibility of producing genetically homogeneous models that are highly advantageous for studying complex biological processes, testing drugs, and researching diseases. However, this achievement raises important ethical questions, particularly regarding animal welfare and the broader ramifications of primate cloning. Approaching the future of primate research with balance is critical, as the scientific world stands on the brink of these revolutionary breakthroughs. This paper aims to summarise the consequences, ethical challenges and possible paths forward in primatology arising from rhesus monkey cloning.

Unlocking trophectoderm mysteries: In vivo and in vitro perspectives on human and mouse trophoblast fate induction

In recent years, the pursuit of inducing the trophoblast stem cell (TSC) state has gained prominence as a compelling research objective, illuminating the establishment of the trophoblast lineage and unlocking insights into early embryogenesis. In this review, we examine how advancements in diverse technologies, including in vivo time course transcriptomics, cellular reprogramming to TSC state, chemical induction of totipotent stem-cell-like state, and stem-cell-based embryo-like structures, have enriched our insights into the intricate molecular mechanisms and signaling pathways that define the mouse and human trophectoderm/TSC states. We delve into disparities between mouse and human trophectoderm/TSC fate establishment, with a special emphasis on the intriguing role of pluripotency in this context. Additionally, we re-evaluate recent findings concerning the potential of totipotent-stem-like cells and embryo-like structures to fully manifest the trophectoderm/trophoblast lineage's capabilities. Lastly, we briefly discuss the potential applications of induced TSCs in pregnancy-related disease modeling.