bims-mamemb 2026-09-06 papers

bims-mamemb

Biomed News

on Mammalian embryogenesis

Issue of 2026–09–06
nine papers selected by
Latangi Venkatraman, Indian Institute of Technology Madras

Culture of the Human Embryo.
Modeling Early Human Embryo Implantation Using Human Endometrial Organoids and Embryo Surrogate Co-cultures for microRNA Transfection.
Oocyte quality in endometriosis-associated infertility: a narrative analysis of mechanisms and therapeutic options.
Evaluating Preimplantation Embryo Metabolism Through Imaging of Cellular Autofluorescence.
Molecular Regulation of Primordial Germ Cell Specification and Implications for In Vitro Gametogenesis.
Single-Cell and Single-Embryo RNA Sequencing.
Clustered Regularly Interspaced Palindromic Repeats (CRISPR) Applied to Gametes and Embryos.
Beyond the Clock: Reprogramming Fertility in Diminished Ovarian Reserve.
Molecular and Developmental Integrity Following Trophectoderm Biopsy: Evidence from Human and Mouse Models.

Methods Mol Biol. 2026 ;3038 107-119

Culture of the Human Embryo.

Kathryn H Gurner, David K Gardner.

  Fundamental to the success of the IVF laboratory is the use of an optimized embryo culture system that facilitates the production of high-quality blastocysts. This is achieved through the establishment of a culture system that encompasses the provision of essential nutrients by use of appropriate culture media, the maintenance of a stable environment in vitro and establishment of effective quality control protocols within the laboratory. While there is considerable variability in the culture systems used in IVF laboratories worldwide, as no standardized system exists, all modern embryo culture systems could be optimized by following these fundamental principles. This chapter describes one method for human blastocyst culture using a time-lapse culture system and highlights key considerations for optimizing embryo culture protocols.

Keywords:  Blastocyst; In vitro embryo culture; Low oxygen tension; Sequential medium; Time-lapse

DOI:  https://doi.org/10.1007/978-1-0716-5292-3_7
Methods Mol Biol. 2026 ;3038 385-398

Modeling Early Human Embryo Implantation Using Human Endometrial Organoids and Embryo Surrogate Co-cultures for microRNA Transfection.

Wei Zhou, Michaela Sacco, Evdokia Dimitriadis.

  In vitro models of human implantation offer a powerful approach to studying the molecular and cellular events critical for a successful pregnancy. In this chapter, we describe a method that combines human endometrial epithelial organoids with human embryo surrogate co-cultures to model the early stages of implantation. Endometrial epithelial organoids, derived from primary tissue, are co-cultured with human cytotrophoblast progenitor cells to simulate the uterine microenvironment during implantation. This model enables a focused study of embryo adhesion and key signaling pathways, offering insights into the molecular mechanisms underlying implantation and reproductive disorders such as infertility.

Keywords:  Cellular interactions; Embryo adhesion; Endometrial organoids; Human embryo implantation; In vitro model; Infertility; Molecular mechanisms

DOI:  https://doi.org/10.1007/978-1-0716-5292-3_21
Mol Biol Rep. 2026 Sep 03. pii: 1518. [Epub ahead of print]53(1):

Oocyte quality in endometriosis-associated infertility: a narrative analysis of mechanisms and therapeutic options.

Lipsa Samal, Chidananda Dash, Sujata Pradhan.

  Endometriosis is a challenging gynaecological condition that can lead to infertility. This unique narrative review summarises the impact of endometriosis, focusing on oocyte quality, its subcellular and molecular mechanisms, clinical effects, and therapeutic options. The disease is associated with a hostile follicular microenvironment caused by inflammation, oxidative stress, granulosa and cumulus cell dysfunction, and hormonal dysregulation. It further leads to spindle disorders, mitochondrial DNA breakdown, and delayed cytoplasmic maturation. Women with stage III-IV endometriosis have low ovarian reserve, fewer retrieved and matured (MII) oocytes, and lower fertilisation and blastocyst development rates, resulting in worse cumulative pregnancy outcomes. However, when good-quality embryos are transferred, implantation and live birth rates are often similar to those of controls, suggesting that the problem is primarily oocyte-driven rather than endometrium-related. Therapeutic options include lifestyle modifications with a healthy diet, yoga, exercise, adequate sleep, and stress management, in addition to individualised assisted reproductive technology (ART) treatments, to enhance prognosis, though with sub-optimal proven mechanisms.

Keywords:  Endometriosis; Infertility; Inflammation; Oocyte quality; Oxidative stress

DOI:  https://doi.org/10.1007/s11033-026-12714-w
Methods Mol Biol. 2026 ;3038 171-195

Evaluating Preimplantation Embryo Metabolism Through Imaging of Cellular Autofluorescence.

Darren J X Chow, Tiffany C Y Tan, Kishan Dholakia, Kylie R Dunning.

  Optical imaging offers a non-invasive approach for assessing embryo viability. This may be achieved through capturing fluorescence from endogenous fluorophores that are associated with cellular metabolism. By recording and analysing natural autofluorescence emitted by molecules involved in metabolism, such as NADH and FAD, this technique offers crucial insights into the metabolic state of embryos, in the absence of exogenous labels. This approach is particularly valuable for preimplantation embryos developed in vitro, where the ability to identify those with high developmental potential may lead to improved outcomes in a clinical setting. Light sheet microscopy has recently emerged as a powerful imaging modality suitable for recording autofluorescence from the developing embryo. In contrast to standard point-scanning (confocal) approaches, it only illuminates the plane of interest, minimising light exposure and photodamage while enabling rapid 3D image acquisition. These aspects make light sheet microscopy particularly well-suited for metabolic imaging of live preimplantation embryos. In this chapter, we describe a general procedure to perform metabolic imaging of live mammalian embryos using light sheet microscopy. This protocol enables direct observation of metabolic changes within embryos in a spatial manner and provides guidelines for optimising imaging parameters to ensure accuracy and reproducibility.

Keywords:  Autofluorescence; Confocal microscopy; Label-free; Light sheet microscopy; Metabolism; Murine preimplantation embryo; Optical imaging

DOI:  https://doi.org/10.1007/978-1-0716-5292-3_11
Biol Reprod. 2026 Sep 03. pii: ioag188. [Epub ahead of print]

Molecular Regulation of Primordial Germ Cell Specification and Implications for In Vitro Gametogenesis.

Maddison Marshall, Eryl Bevan, Yuan Wang.

  Primordial germ cells (PGCs) are the embryonic precursors of gametes, essential for transmitting genetic and epigenetic information across generations. However, PGC specification occurs within a narrow developmental window and involves only a small number of cells, making it difficult to study in vivo. In vitro models using pluripotent stem cells have enabled the generation of primordial germ cell-like cells, but these systems often rely on exogenous signaling and exhibit variability in efficiency and epigenetic fidelity. In this review, we synthesize current understanding of PGC specification in mouse and human systems, emphasizing the integration of signaling pathways, transcriptional networks, epigenetic reprogramming, and metabolic regulation. Canonical regulators, including PRDM1, PRDM14, TFAP2C, and SOX17, function within a broader, interconnected network that establishes for PGC competence. Understanding these interactions will be crucial for advancing in vitro gametogenesis and improving mammalian reproduction.

Keywords:  mammalian reproduction; pluripotent stem cells; primordial germ cells

DOI:  https://doi.org/10.1093/biolre/ioag188
Methods Mol Biol. 2026 ;3038 309-335

Single-Cell and Single-Embryo RNA Sequencing.

Bastien Ducreux, Lucile Ferreux, Julie Firmin, Catherine Patrat, Patricia Fauque.

  The scarcity of available donated human embryos for research and technical difficulties present numerous challenges for human development research. Developments in RNA-seq technologies for small inputs, such as single embryos and single cells, now make human applications possible. This chapter outlines single-embryo RNA-seq, with adaptations noted for single-cell RNA-seq and single embryonic/abembryonic compartment applied to preimplantation embryo analysis, from embryo collection to bioinformatic data processing, and the specificities of applications of these techniques in reproductive biology.

Keywords:  Inner cell mass; Preimplantation embryo; Single-cell RNA-seq; Single-embryo RNA-seq; Transcriptome; Trophectoderm

DOI:  https://doi.org/10.1007/978-1-0716-5292-3_18
Methods Mol Biol. 2026 ;3038 447-475

Clustered Regularly Interspaced Palindromic Repeats (CRISPR) Applied to Gametes and Embryos.

Munuse C Savash Ishanzadeh, Dagan Wells.

  Preimplantation genetic testing (PGT) facilitates the identification of embryos affected by specific types of genetic abnormalities. However, PGT does not seek to treat the genetic abnormality, rather it is an embryo selection tool, employing a strategy of detection and exclusion. Until recently, the notion that mutations and aneuploidies could be corrected in gametes, or in embryos produced using in vitro fertilization (IVF), seemed improbable. However, rapid progress in the evolution of gene editing technologies may make this a realistic possibility in the near future. Not only would such an approach help to avoid the discard of human embryos, which some find challenging from ethical or religious perspectives, but it would also increase the number of embryos considered suitable for transfer, potentially leading to higher pregnancy rates than achieved in PGT cycles. This chapter considers the use of genome editing applied to human preimplantation embryos, describing a protocol that can be used to inactivate genes for research purposes, and which might, in the future, allow for the correction of pathogenic mutations.

Keywords:  CRISPR-Cas9; Double strand breaks; Genome editing; Genome sequencing; Human embryo

DOI:  https://doi.org/10.1007/978-1-0716-5292-3_24
Reproduction. 2026 Sep 04. pii: xaag112. [Epub ahead of print]

Beyond the Clock: Reprogramming Fertility in Diminished Ovarian Reserve.

Tingyu Lang, Xiaolei Liang, Yongxiu Yang.

  Diminished Ovarian Reserve (DOR) is a significant manifestation of female reproductive aging that profoundly impacts fertility and quality of life. In recent years, the emergence of aging reprogramming technologies has provided new insights into the mechanisms underlying DOR and potential therapeutic approaches. This review synthesizes current knowledge on the role of aging reprogramming in DOR, focusing on key molecular events such as telomere shortening, mitochondrial dysfunction, and epigenetic alterations. Furthermore, we summarize clinical diagnostic criteria and emerging biomarkers for DOR, while exploring the limitations of existing treatment strategies and the potential interventions based on aging reprogramming. By addressing these issues, this review aims to highlight the interplay between aging processes and ovarian function, paving the way for innovative therapeutic avenues to improve reproductive health in women experiencing DOR.

Keywords:  Aging reprogramming; Diminished ovarian reserve; Epigenetics; Mitochondrial dysfunction; Stem cell therapy

DOI:  https://doi.org/10.1093/reprod/xaag112
F S Sci. 2026 Sep 01. pii: S2666-335X(26)00062-5. [Epub ahead of print]

Molecular and Developmental Integrity Following Trophectoderm Biopsy: Evidence from Human and Mouse Models.

Blair R McCallie, Michelle M Denomme, Kerri A Bochantin-Winders, Mary E Haywood, Jason R Wilson, Keelee J McCarty, Cameron M Hebert, Jennifer M Hamm, William B Schoolcraft, Mandy G Katz-Jaffe.

   OBJECTIVE: To determine whether trophectoderm (TE) biopsy performed for preimplantation genetic testing induces molecular, epigenetic, or developmental perturbations in preimplantation embryos and subsequent placental development.
DESIGN: Comparative multi-omics investigation of human blastocysts combined with a murine embryo transfer model.
SUBJECTS: Surplus cryopreserved human euploid blastocysts donated to research and murine blastocysts that were either subjected to TE biopsy or no biopsy.
EXPOSURE: The impact of blastocyst-stage trophectoderm biopsy on transcriptomic, epigenomic, developmental, and/or placental outcomes.
MAIN OUTCOME MEASURES: Differential gene expression, imprinting methylation, whole-genome DNA methylation of inner cell mass (ICM) and TE, mitotic cell division mechanics, implantation rates, fetal and placental growth, placental methylation.
RESULTS: Trophectoderm biopsy was not associated with biologically meaningful molecular or epigenetic alterations in human blastocysts. Gene expression, imprinting methylation, global DNA methylation, and DNA budding/shedding were comparable between biopsied and non-biopsied embryos. In a murine model, biopsy had no effect on implantation rates, fetal or placental growth, placental methylome, or imprinting methylation status.
CONCLUSION: A comprehensive multi-omics assessment of human blastocysts, supported by developmental and placental analyses in a murine model, found no evidence that trophectoderm biopsy adversely affects early embryonic molecular regulation or subsequent developmental outcomes. These findings support the use of TE biopsy as a minimally invasive micro-manipulation procedure.

Keywords:  PGT-A; Trophectoderm biopsy; epigenetics; imprinting; placenta; transcriptomics

DOI:  https://doi.org/10.1016/j.xfss.2026.08.003