IVF News

Male-factor infertility remains one of the most persistent “known unknowns” in reproductive medicine. We can measure sperm concentration, motility, morphology, and DNA fragmentation with increasing sophistication, yet the molecular levers that govern successful spermatogenesis are still difficult to interrogate directly. That challenge is especially pronounced for genes on the Y chromosome, where repetitive sequence, paralogy, and limited reagent availability can turn straightforward protein-level questions into slow, uncertain work.

A January 2026 update from the University of Hawaiʻi at Mānoa highlights a practical step forward: new mouse models that enable researchers to track the key Y-linked transcription factors encoded by Zfy1 and Zfy2 at the protein level. The value here is not a single new mechanistic conclusion, but an experimental platform that makes deeper mechanistic questions feasible.

Zfy1 and Zfy2 encode zinc finger proteins long implicated in murine fertility, with evidence for nonredundant roles across meiosis and spermiogenesis. Yet protein-level confirmation of expression patterns and interaction partners has been constrained by a deceptively basic limitation. ZFY1 and ZFY2 are highly similar in sequence, and antibody specificity has been a recurring bottleneck. When two proteins are nearly indistinguishable by standard immunoreagents, it becomes hard to establish when each factor is present, where it localizes, and what complexes it forms.

This matters because loss-of-function studies can reveal necessity without clarifying direct mechanism. Prior knockout work referenced by the Hawaiʻi team showed that loss of both homologs resulted in complete infertility with severe spermatogenic defects. Follow-on transcriptomics implicated broad dysregulation across pathways tied to apoptosis, chromatin organization, and spermatogenic progression. These observations support a transcriptional regulatory role, but they do not pinpoint direct targets or stage-specific actions.

In the BMC Genomics study, Holmlund and colleagues address the reagent bottleneck by generating epitope-tagged knock-in alleles using CRISPR/Cas9. They created multiple lines, including Zfy1-HA, Zfy2-FLAG, Zfy2-3xFLAG, Zfy2-HA, and a double knock-in combining Zfy1-HA with Zfy2-MYC. Targeting was validated by genotyping and sequencing, with attention paid to potential off-target candidates.

A key strength of the approach is that it remains close to native biology. The knock-in animals were fertile and showed normal sperm parameters overall, indicating that tagging at the endogenous locus did not obviously compromise reproductive function. That point is essential, because these models are intended as a foundation for downstream chromatin, interaction, and regulatory studies rather than as artificial overexpression systems.

With the tagged lines in hand, the group could detect ZFY proteins in testes by Western blot and immunofluorescence. That allowed the authors to ask two basic questions that RNA data alone cannot resolve cleanly: which germ cells express ZFY1 versus ZFY2, and when expression begins during the first wave of spermatogenesis.

By immunofluorescence, both ZFY1 and ZFY2 were detected in zygotene spermatocytes. In addition, ZFY2 signal extended into post-meiotic development, with detection reported in spermatids at steps 7 to 8 and step 9. These cell-stage assignments are important because they sharpen hypotheses about which regulatory transitions each factor may be influencing, and they provide practical guidance for designing follow-up assays that enrich for the relevant cell populations.

The paper also delivers a useful technical lesson for anyone planning similar work on Y-linked genes. Not all tags behaved equally well. ZFY2-FLAG was not detectable in whole testis by Western blot or in sections by immunofluorescence, while ZFY2-3xFLAG produced weak knock-in-specific bands around 140 kDa. By contrast, HA-tagged lines provided robust detection. Zfy1-HA yielded a band near the expected 88 kDa plus an additional band near 140 kDa, and Zfy2-HA was primarily seen near 140 kDa. The authors discuss plausible explanations for the larger-than-expected species, including dimerization or heavy post-transcriptional modification, and frame these findings as part of the real-world complexity of endogenous tagging on the Y chromosome.

From an IVF-facing perspective, these models are best understood as infrastructure. They do not claim to complete the ZFY mechanistic story, but they remove a major barrier to completing it. Once ZFY targets and co-regulators are defined, the downstream implications could include more interpretable links between Y-linked variation and spermatogenic failure, sharper stratification of idiopathic male-factor cases, and clearer biological hypotheses for why some men present with severe defects that do not align neatly with conventional semen parameters.

The University of Hawaiʻi news release frames the work as a foundation for understanding and eventually treating male infertility, emphasizing ZFY as a key Y-chromosome regulator in male reproductive cells. In practical terms, the most immediate impact is that researchers can now realistically pursue immunoprecipitation and mass spectrometry to identify interaction partners, and integrate tagging with chromatin-centric assays to map direct transcriptional targets. For reproductive scientists, the excitement is less about a single result and more about the acceleration of everything that becomes possible once a difficult protein finally becomes experimentally accessible.

Sources

19 December 2025. BMC Genomics

• CRISPR/Cas9-mediated knock-in of the murine Y chromosomal genes Zfy1 and Zfy2

13 January 2026. University of Hawai'i News

• UH researchers advance study of key male fertility gene

Implantation is where assisted reproduction meets the least observable part of early human development. We can grade blastocysts, optimize transfer, and quantify endocrine markers, yet the decisive step still happens out of sight: a conceptus engages a hormonally primed endometrium, finds purchase, and begins a sequence of reciprocal signaling that rapidly commits both tissues to pregnancy. The difficulty is not only ethical access to implanting embryos, but also the lack of in vitro systems that behave like a receptive uterine surface rather than a simplified cell layer.

A cluster of late 2025 papers and accompanying coverage point to a meaningful shift. Instead of asking whether an embryo can attach to something, these approaches aim to reproduce the architecture, compartmentalization, and endocrine responsiveness of the superficial endometrium, then measure what embryo and maternal tissues do to each other once contact is made. The result is not a single “womb in a dish” headline, but a set of platforms that map onto different scientific and translational questions: discovery of embryo endometrium communication, mechanistic perturbation, and patient-stratified failure phenotypes with drug screening. 

One of the most visible examples comes from work highlighted by the Babraham Institute, describing a culture system engineered to replicate key features of the womb lining and then used with donated IVF embryos. The model is built from primary endometrial epithelial and stromal cells, assembled to reproduce a layered tissue organization resembling a biopsy, and tuned to show hormone-driven receptivity. In that setting, early-stage embryos proceed through adhesion and invasion into the scaffold, and the system responds with pregnancy-like supportive outputs rather than remaining a passive substrate. This matters because it moves the experimental readout from attachment alone to the quality of the maternal response and the emergent behavior of the interface as a unit. 

At a biological level, the platform is positioned to address two long-standing limitations. First, it supports observation of post-implantation hallmarks approaching the day 12 to day 14 window, a period that is central to lineage segregation and early placental program initiation but has been largely inaccessible. Second, it enables molecular profiling of the implantation sites, effectively turning the interface into a measurable signaling landscape. The Babraham summary emphasizes single-cell analysis to characterize cell states and infer communication between embryo-derived and endometrium-derived compartments, with particular attention to early placental landmarks and the emergence of specialized trophoblast populations. 

The paired Cell paper, “Modeling human embryo implantation in vitro,” formalizes this as a 3D endometrial model that recapitulates luminal, glandular, and stromal compartments of receptive human endometrium, and supports implantation not only of embryos but also of blastoids. Two details are especially important for readers thinking about experimental leverage. First, the inclusion of glandular and luminal features alongside stroma is not cosmetic; it creates distinct microenvironments that are likely to shape ligand availability, polarity, and the physical boundary conditions that trophoblast encounters. Second, the authors explicitly use single-cell RNA sequencing at day 14 to uncover predicted ligand-receptor interactions at the interface, then test causality by disrupting specific signaling routes. In their reported perturbation, interfering with extravillous trophoblast to stromal signaling leads to defects in trophoblast outgrowth, providing a concrete example of how these systems can move from descriptive atlases to mechanism. 

In parallel, a second Cell study takes a more explicitly translational route by building an “in-chip” implantation model designed to be scalable and patient-aware. In “A 3D in vitro model for studying human implantation and implantation failure,” the authors co-culture human blastoids or blastocysts with a bioengineered human endometrial tissue termed an endometrioid, housed within microfluidic chips. The microfluidic framing is not a superficial engineering flourish. It supports controlled delivery of factors, standardized geometry, and potentially a path toward throughput, which becomes essential if the goal is to compare cohorts and run compound screens. 

The implantation failure question is handled directly by incorporating endometrial samples from patients with recurrent implantation failure (RIF) and comparing their performance to endometrioids derived from fertile controls. In this model, RIF-derived endometrioids show significantly reduced implantation capability. That observation is valuable even before mechanism because it suggests the platform is sensitive to clinically relevant endometrial phenotypes, not just embryo quality. The study then uses a targeted screen of FDA-approved compounds to identify candidates that improve implantation efficiency in RIF-derived endometrioids. This is a notable conceptual change: rather than generalizing from an “average” endometrium, it hints at individualized testing where the endometrium itself is the experimental variable and therapeutic target. 

A third related advance appears in Cell Stem Cell with a 3D co-culture that supports post-implantation development to day 14 while enabling reciprocal embryo-maternal communication via endometrial organoids. The emphasis here is on developmental fidelity and the breadth of embryonic milestones that can be reached in co-culture conditions. The abstract reports structural and molecular correspondence to Carnegie stage landmarks, including yolk sac formation, primordial germ cell specification, and trophoblast maturation. It also reports that the endometrial niche accelerates extravillous trophoblast emergence around day 9 and primes invasive programs, while blockade of maternal signals, including disruption of hCG signaling, impairs embryonic progression. For scientists, this reads as a platform built to test how uterine cues shape lineage timing and trophoblast trajectories rather than a platform optimized for screening. 

Taken together, these three systems suggest a workable division of labor that the field has needed for a long time. A biomimetic, compartmentalized endometrium scaffold co-cultured with embryos and blastoids can reveal the communication topology at the interface and support perturbation experiments that assign causality. A microfluidic endometrioid approach can turn implantation failure into a measurable, patient-derived phenotype and provides a plausible route to identifying candidate interventions using approved compound libraries. A co-culture system tuned for post-implantation fidelity can focus on developmental events that are otherwise inferential in humans, especially those tied to trophoblast maturation and early placental programs. 

The mainstream coverage around these publications reflects how quickly implantation modeling is becoming platform science. The Guardian’s reporting captures the core experimental idea in accessible terms: build a physiologically relevant womb lining from donated tissue, show that embryos can implant and produce pregnancy-associated signals, then analyze the molecular dialogue at the embedding sites. It also points out the practical ceiling of day 14 culture, which is exactly where many of these models aim to be maximally informative, because it sits at the intersection of ethically permitted observation and rapidly diversifying cell fate decisions. 

Science’s news coverage focuses on the idea that replicas of the uterine lining can be used not only to observe implantation, but to test compounds that might improve pregnancy success, aligning closely with the RIF-oriented screening narrative. Meanwhile, technology press coverage, including MIT Technology Review, signals broader interest in microfluidic uterus-on-a-chip framing, which may accelerate standardization, commercialization, and cross-disciplinary tool development even if the underlying biology remains the central challenge. 

For IVF and reproductive medicine, the near-term implications should be interpreted with care. These models do not replace clinical embryo selection, and they do not yet solve the heterogeneity of endometrial receptivity across cycles, patients, immunologic states, and endocrine regimens. But they do provide a credible experimental bridge between clinical observations like recurrent implantation failure and mechanistic hypotheses that can be tested in human-relevant tissue architectures. If these platforms continue to mature, the most interesting translational path may be endometrium-first diagnostics and interventions: identifying which signaling modules, mechanical properties, or endocrine response states distinguish a receptive endometrium from a superficially normal but functionally incompatible one, then using that information to guide therapy rather than relying on repeated transfer attempts.

For scientists, the most exciting aspect may be methodological. Implantation has long been a field where we built stories from constrained data. The new generation of 3D endometrium platforms, especially those that support embryo and blastoid implantation and permit single-cell, spatial, and functional perturbation assays, make it realistic to treat embryo-maternal communication as a testable system. That is a substantial upgrade in experimental resolution, and it arrives at a moment when the tools to interpret complex multicellular signaling, from ligand-receptor inference to causal perturbation, are finally mature enough to match the biology. 

Sources

17 December 2025. Babraham Institute

Researchers 'listen in' to embryo-mother interactions during implantation using a culture system replicating the womb lining

23 December 2025. Science

Replicas of the uterine lining reveal drugs that may boost pregnancy success

23 December 2025. MIT Technology Review

Researchers are getting organoids pregnant with human embryos

23 December 2025. The Guardian

Scientists create replica human womb lining and implant early-stage embryos

23 December 2025. Cell

Modeling human embryo implantation in vitro

23 December 2025. Cell

A 3D in vitro model for studying human implantation and implantation failure

23 December 2025. Cell Stem Cell
3D post-implantation coculture of human embryo and endometrium

Training Batch Schedule February 2026

Batch - II :    09th  to 23th  February

The International School of Embryology a unit of Chennai Fertility Centre and Research Institute was established to offer training in Advanced Reproductive Techniques and Embryology for clinicians and embryologists. It will help them to know in-depth knowledge and have good hands-on training. The members of our teaching faculty aim to bring Clinician and Embryologists to the highest level of knowledge about Assisted Reproductive Technology and practical capability.

Our courses cover basics in Andrology, Embryology, ICSI & Cryosciences (Hands-on).

Limited Seats. For admission Contact  9003111598 / 8428278218 

On Friday 26^th September Churchill Archives Centre hosted an evening panel session on the life and legacy of Sir Robert Edwards, IVF pioneer. This was the second part of a two-part day conference Bob Edwards centenary: His life, work and legacy.  

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The IVF toolkit keeps expanding, but the supporting evidence does not expand evenly. Some tests and interventions are well anchored in outcomes, others remain plausible but unproven, and a third group can look beneficial only when judged by narrow endpoints. A practical way to read the field is to treat IVF as a pathway rather than a single event: stimulation, retrieval, fertilization, embryo culture, optional biopsy and testing, optional cryopreservation, transfer strategy, and follow-up transfers. In that pathway framing, it becomes clear why evidence can feel contradictory and why the same intervention can look “effective” in one analysis and neutral in another. Medscape’s recent overview leans into this variability and reinforces a point that is sometimes underemphasized in the add-on era: age remains the most reliable predictor of IVF success, and many additional tests do not outperform it as a global predictor. 

Issue 1: The endpoint problem (per transfer vs per started cycle)

Many claims in IVF are supported by intermediate outcomes that do not necessarily translate into higher cumulative live birth per started cycle or per retrieval. Implantation rate, clinical pregnancy per transfer, euploidy rate, and miscarriage rate can all be meaningful, but they are vulnerable to pathway effects. Any intervention that changes how many patients reach transfer, how many embryos remain available for transfer, how long it takes to reach transfer, or how much cost and burden accumulates can shift per-transfer statistics without improving, and sometimes while worsening, cumulative outcomes. This is why intention-to-treat analyses and cumulative live birth remain the load-bearing endpoints when deciding whether a test or add-on should be routine, selective, or research-only.

Issue 2: Analytic validity is not clinical utility

Reproductive medicine has become extremely good at measuring signals, categorizing embryos, and generating scores. That technical progress is real. The scientific gap is that a measurable signal is not automatically a clinically actionable signal. Clinical utility requires that the test changes management and that the management change improves outcomes that matter. This distinction is central to the current debate around several popular tools: the assays can be repeatable and biologically plausible, yet still fail to improve live birth, shorten time-to-pregnancy, or reduce burden when deployed in routine care.

Issue 3: Ovarian reserve testing works best when treated as a response tool, not a fertility forecast

AMH and antral follicle count are useful for predicting ovarian response and helping guide stimulation planning, expected oocyte yield, and risk counseling. The misstep is turning them into broad predictions about natural fertility, egg quality, or time to pregnancy in people without infertility. ACOG’s committee opinion states that using serum AMH levels for fertility counseling in women without a diagnosis of infertility is not currently supported by high-quality data.  In other words, ovarian reserve markers can be valuable within their validated use-case, but they do not function as general-purpose fertility prediction tools and should not be framed that way to patients or clinicians.

Issue 4: PGT-A shows how embryo selection can improve a slice of the pathway without improving the whole pathway

PGT-A is one of the most common places where endpoint choice and pathway effects collide. The promise is efficiency: avoid transfers with low implantation potential and reduce miscarriage by prioritizing euploid embryos. The evidence, however, remains mixed when evaluated at the level of patient-important outcomes across diverse populations and clinic workflows. ASRM’s 2024 committee opinion states that the value of PGT-A as a routine screening test for all IVF patients has not been demonstrated.  That framing does not claim “no one benefits,” but it does set a high bar for routine use and highlights the need to match PGT-A to specific indications, clear counseling goals, and trial-quality evidence using cumulative endpoints.

Issue 5: Endometrial receptivity testing has not earned a routine role in randomized evidence

Endometrial receptivity testing is appealing because it offers a clean narrative: identify an individual window of implantation and time transfer accordingly. In a large randomized clinical trial in patients undergoing single euploid frozen embryo transfer, timing guided by endometrial receptivity testing did not improve live birth compared with standard timing, and the authors conclude the findings do not support routine use to guide timing.  This is a good example of why personalization claims need to clear a higher evidentiary threshold than mechanistic plausibility, especially when the test adds biopsy burden, cost, and cycle complexity.

Issue 6: Add-ons are increasingly treated as an evidence governance issue

A growing proportion of IVF innovation arrives as “add-ons,” often priced as optional enhancements and adopted unevenly across clinics. The scientific and ethical problem is not innovation itself, but routine adoption without robust, patient-relevant outcome data. ESHRE’s add-ons guidance and its good practice recommendations explicitly focus on safety, efficacy, and transparent counseling about whether an add-on is likely to improve live birth.  The HFEA has operationalized a related goal with its evidence ratings for treatment add-ons, designed to make evidence quality legible and to discourage routine use when benefit is unclear or unsupported.  Even outside the add-on label, this approach helps bring the field back to a consistent standard: routine care should be reserved for interventions with credible evidence of meaningful benefit.

Issue 7: Emerging genomics changes the risk profile because precision can outpace validity

The next wave of embryo selection includes polygenic embryo screening and other high-dimensional scoring approaches. These differ from earlier add-ons because they can look quantitatively precise while carrying unresolved issues around predictive accuracy, ancestry portability, calibration, and clinical meaning at the individual embryo level. ASRM’s Ethics and Practice Committees concluded in December 2025 that polygenic embryo screening is not ready for clinical use, citing lack of proven clinical utility and significant scientific and ethical concerns.  This is likely a preview of how the field will increasingly evaluate new tools: not just whether they produce a number, but whether that number is stable, generalizable, and tied to outcomes that matter.

Issue 8: Standardization pressure is rising, driven by evidence gaps and practice variation

Clinical variation is often a marker of uncertainty, not personalization. NICE is actively updating fertility guidance, with an expected publication date of March 19, 2026, reflecting ongoing efforts to reduce practice variation and scrutinize unproven interventions.  Across regions and regulators, the shared direction is a higher expectation that routine interventions should demonstrate benefit on outcomes like live birth and time-to-pregnancy, not only on intermediate metrics or mechanistic plausibility.

Taken together, these issues point to a simple scientific posture that is increasingly useful in IVF. Treat new tests and add-ons as hypotheses until they demonstrate clinical utility across the pathway. Prefer evidence anchored to intention-to-treat analyses and cumulative live birth. Be explicit about what a test predicts well and what it does not. And keep age, diagnosis, and pathway design as the baseline comparators, because many tools are competing against a surprisingly strong predictor and a surprisingly complex sequence.

Sources

• Medscape. December 05, 2025
 IVF Tests and Treatments Are Backed by Varying Evidence

• American Society for Reproductive Medicine. 
The use of preimplantation genetic testing for aneuploidy: a committee opinion 

• American Society for Reproductive Medicine. 8 Dec 2025. 
ASRM Ethics and Practice Committees Release New Report Concluding Polygenic Embryo Screening Is Not Ready for Clinical Use 

• ESHRE. 
Add-ons 

• Human Reproduction. 
Good practice recommendations on add-ons in reproductive medicine 

• Human Fertilisation and Embryology Authority. 
Treatment add-ons with limited evidence 

• Fertility and Sterility. 
Live birth after transfer of a single euploid vitrified-warmed blastocyst according to standard timing versus timing as recommended by endometrial receptivity analysis

• NICE. 19 Mar 2026 (expected publication).
Fertility problems: assessment and treatment – update 1 and 2

16th December, 3pm EST, 8pm UK, 9pm CET

Moderators: 
Dr Pierre Comizzoli
Panelist: Matt Pettit

Presenters:
Tullis Matson FRAgS, HonDTech, DL: Life after Life
Professor Andrew Pask: Restoring the past to protect our future
Dr Andres Gambini: All in the Family: In Vitro Embryo Production in Horses, Donkeys, Mules and Zebras

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9th December, 3pm EST, 8pm UK, 9pm CET

Moderators:
Dr Mina Alikani
Dr Başak Balaban

Presenters:

• Dr Lodovico Parmegiani: Universal post-warming dilution of
  vitrified embryos: impact of different vitrification/warming kits, warming
  volume and rapid dilution/rehydration steps on survival and clinical outcomes
• Dr Juergen Liebermann: Life in the fast lane
• Dr Ana Cobo: Comparison of one-step and conventional warming in sibling donor oocytes: a proof-of-concept study

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New clinical report challenges assumptions about embryo viability and highlights the complexity of PGT-A interpretation

The first documented birth of healthy twins following the transfer of embryos diagnosed as aneuploid has been reported, adding an important data point to the ongoing discussion about the limitations of preimplantation genetic testing for aneuploidy. The findings come from a case report published in Fertility and Sterility and summarised by EMJ Reviews. Together, they describe a scenario that underscores how embryo genetics, early developmental dynamics, and biopsy sampling can interact in unexpected ways.

The case involved a patient who underwent IVF with PGT-A. Two blastocysts were classified as aneuploid by trophectoderm biopsy. Both embryos were transferred after counselling, and both implanted. The pregnancy progressed normally, and the patient delivered healthy twins with no structural anomalies. Postnatal karyotyping confirmed that the twins were chromosomally normal.

This outcome reinforces the growing understanding that a trophectoderm biopsy represents only a small fraction of the embryo. False positive aneuploid calls can occur if the sampled cells contain mosaic or transient abnormalities that are not representative of the inner cell mass, which forms the fetus. As the field has recognised in recent years, some embryos labelled as aneuploid may still have the developmental capacity to self-correct or may have had normal ICM lineages from the start.

The authors emphasise that this report does not suggest routine transfer of embryos diagnosed as aneuploid. Instead, it highlights the need for careful counselling and the importance of ongoing research into the predictive value of PGT-A. Clinicians continue to debate how best to interpret low-level mosaicism, segmental abnormalities, and complex profiles, especially when patients have limited embryos available for transfer.

From a scientific standpoint, this case provides further evidence that embryo genetics is more nuanced than binary categories can capture. The discordance between the biopsy result and the clinical outcome underscores the importance of technical precision, biological variability, and thoughtful interpretation.

For IVF laboratories and clinicians, the report ultimately serves as a reminder that the embryo is a dynamic system. While PGT-A remains a widely used screening tool, individual outcomes like this one highlight the need for continued refinement of testing methods and more robust data to guide clinical decision-making.

Sources