Generating human blastoids modeling blastocyst-stage embryos and implantation

Transplantation of beige adipose organoids fabricated using adipose acellular matrix hydrogel improves metabolic dysfunction in high-fat diet-induced obesity and type 2 diabetes mice

Transplantation of brown adipose tissue (BAT) is a promising approach for treating obesity and metabolic disorders. However, obtaining sufficient amounts of functional BAT or brown adipocytes for transplantation remains a major challenge. In this study, we developed a hydrogel that combining adipose acellular matrix (AAM) and GelMA and HAMA that can be adjusted for stiffness by modulating the duration of light-crosslinking. We used human white adipose tissue-derived microvascular fragments to create beige adipose organoids (BAO) that were encapsulated in either a soft or stiff AAM hydrogel. We found that BAOs cultivated in AAM hydrogels with high stiffness demonstrated increased metabolic activity and upregulation of thermogenesis-related genes. When transplanted into obese and type 2 diabetes mice, the HFD + BAO group showed sustained improvements in metabolic rate, resulting in significant weight loss and decreased blood glucose levels. Furthermore, the mice showed a marked reduction in nonalcoholic liver steatosis, indicating improved liver function. In contrast, transplantation of 2D-cultured beige adipocytes failed to produce these beneficial effects. Our findings demonstrate the feasibility of fabricating beige adipose organoids in vitro and administering them by injection, which may represent a promising therapeutic approach for obesity and diabetes.

Validation of a mouse 3D gastruloid-based embryotoxicity assay in reference to the ICH S5(R3) guideline chemical exposure list

There is growing interest in establishing alternative methods in place of conventional animal tests to assess the developmental and reproductive toxicity (DART) of chemicals. Gastruloids are 3D aggregates of pluripotent stem cells that spontaneously exhibit axial elongation morphogenesis similar to gastrulation. They have been explored as in vitro embryogenesis models for developmental and toxicological studies. Here, a mouse gastruloid-based assay was validated for DART assessment in accordance with the ICH S5(R3) guideline, which provides the plasma concentration data of various reference drugs in rodents, specifically Cmax and AUC for NOAEL and LOAEL. First, adverse effect concentrations of the reference drugs and their known metabolites on gastruloid development were determined based on morphological impact, namely reduced growth or aberrant elongation. Then, the NOAEL to LOAEL concentration range obtained from the gastruloid assay was compared with that in rodents to examine similarities in sensitivity between the in vitro and in vivo assays for each chemical. For 18 out of the 24 reference drugs that have both NOAEL and LOAEL information in rodents, the sensitivity of the gastruloid assay was comparable to the in vivo assay within an 8-fold concentration margin. For 7 out of the 8 additional reference drugs that have only NOAEL or LOAEL information in rodents, the gastruloid assay was in line with the in vivo data. Altogether, these results support the effectiveness of the gastruloid assay, which may be exploited as a non-animal alternative method for DART assessment.

Engineering pluripotent stem cells with synthetic biology for regenerative medicine

Pluripotent stem cells (PSCs), characterized by self-renewal and capacity of differentiating into three germ layers, are the programmable building blocks of life. PSC-derived cells and multicellular systems, particularly organoids, exhibit great potential for regenerative medicine. However, this field is still in its infancy, partly due to limited strategies to robustly and precisely control stem cell behaviors, which are tightly regulated by inner gene regulatory networks in response to stimuli from the extracellular environment. Synthetic receptors and genetic circuits are powerful tools to customize the cellular sense-and-response process, suggesting their underlying roles in precise control of cell fate decision and function reconstruction. Herein, we review the progress and challenges needed to be overcome in the fields of PSC-based cell therapy and multicellular system generation, respectively. Furthermore, we summarize several well-established synthetic biology tools and their applications in PSC engineering. Finally, we highlight the challenges and perspectives of harnessing synthetic biology to PSC engineering for regenerative medicine.

A combined clinical and specific genes' model to predict live birth for in vitro fertilization and embryo transfer patients

BACKGROUND

We aimed to develop an accurate model to predict live birth for patients receiving in vitro fertilization and embryo transfer (IVF-ET) treatment.

METHODS

This is a prospective nested case-control study. Women aged between 18 and 38 years, whose body mass index (BMI) were between the range of 18.5-24 kg/m2, who had an endometrium of ≥ 8 mm at the thickest were enrolled from 2018/9 to 2020/8. All patients received IVF-ET treatment and were followed up until Jan. 2022 when they had reproductive outcomes. Endometrial samples during the window of implantation (LH + 6 to 9 days) were subjected to analyze specific endometrial receptivity genes' expression using real-time PCR (RT-PCR). Patients were divided into live birth group and non-live birth group based on IVF-ET outcomes. Clinical signatures relevant to live birth were collected, analyzed, and used to establish a predictive model for live birth by univariate analysis (clinical model). Specific endometrial receptivity genes' expression was analyzed, selected, and used to construct a predictive model for live birth by The Least Absolute Shrinkage and Selection Operator (LASSO) analysis (gene model). Finally, significant clinical factors and genes were used to construct a combined model for predicting live birth using multivariate logistical regression (combined model). Different models' Area Under Curve (AUC) were compared to identify the most predictive model.

RESULTS

Thirty-nine patients were enrolled in the study, twenty-four patients had live births, fifteen did not. In univariate analysis, the odds of live birth for women with ovulation dysfunction was 4 times higher than that for women with other IVF-ET indications (OR = 4.0, 95% CI: 1.125 - 8.910, P = 0.018). Age, body mass index, duration of infertility, primary infertility, repeated implantation failure, antral follicle counting, ovarian sensitivity index, anti-Mullerian hormone, controlled ovarian hyperstimulation protocol and duration, total dose of FSH/hMG, number of oocytes retrieved, regiment of endometrial preparation, endometrium thickness before embryo transfer, type of embryo transferred were not associated with live birth (P > 0.05). Only ovulation dysfunction was used to construct the clinical model and its AUC was 0.688. In lasso analysis, GAST, GPX3, THBS2 were found to promote the risk of live birth. AUCs for GAST, GPX3, THBS2 reached to 0.736, 0.672, and 0.678, respectively. The gene model was established based on these three genes and its AUC was 0.772. Ovulation dysfunction, GAST, GPX3, and THBS2 were finally used to construct the combined model, reaching the highest AUC (AUC = 0.842).

CONCLUSIONS

Compared to the single model, the combined model of clinical (Ovulation dysfunction) and specific genes (GAST, GPX3, THBS2) was more accurate to predict live birth for IVF-ET patients.

Wnt and BMP signalling direct anterior-posterior differentiation in aggregates of mouse embryonic stem cells

Stem-cell-based embryo models have allowed greater insight into peri-implantation mammalian developmental events that are otherwise difficult to manipulate due to the inaccessibility of the early embryo. The rapid development of this field has resulted in the precise roles of frequently used supplements such as N2, B27 and Chiron in driving stem cell lineage commitment not being clearly defined. Here, we investigate the effects of these supplements on embryoid bodies to better understand their roles in stem cell differentiation. We show that Wnt signalling has a general posteriorising effect on stem cell aggregates and directs differentiation towards the mesoderm, as confirmed through the upregulation of posterior and mesodermal markers. N2 and B27 can mitigate these effects and upregulate the expression of anterior markers. To control the Wnt gradient and the subsequent anterior versus posterior fate, we make use of a BMP4 signalling centre and show that aggregates in these conditions express cephalic markers. These findings indicate that there is an intricate balance between various culture supplements and their ability to guide differentiation in stem cell embryo models.

Technical challenges of studying early human development

Recent years have seen exciting progress across human embryo research, including new methods for culturing embryos, transcriptional profiling of embryogenesis and gastrulation, mapping lineage trajectories, and experimenting on stem cell-based embryo models. These advances are beginning to define the dynamical principles of development across stages, tissues and organs, enabling a better understanding of human development before birth in health and disease, and potentially leading to improved treatments for infertility and developmental disorders. However, there are still significant roadblocks en route to this goal. Here, we highlight technical challenges to studying early human development and propose ways and means to overcome some of these constraints.

Human organoid systems in modeling reproductive tissue development, function, and disease

Research focused on human reproductive biology has primarily relied upon clinical samples affording mainly descriptive studies with limited implementation of functional or mechanistic understanding. More importantly, restricted access to human embryonic material has necessitated the use of animals, primarily rats and mice, and short-term primary cell cultures derived from human patient material. While reproductive developmental processes are generally conserved across mammals, specific features unique to human reproduction have resulted in the development of human-based in vitro systems designed to retain or recapitulate key molecular and cellular processes important in humans. Of note, major advances in 3D epithelial stem cell-based systems modeling human reproductive organ development have been made. These cultures, broadly referred to as organoids, enable research aimed at understanding cellular hierarchies and processes controlling cellular differentiation and function. Moreover, organoids allow the pre-clinical testing of pharmacological substances, both from safety and efficacy standpoints, and hold large potential in driving aspects of personalized medicine that were previously not possible with traditional models. In this mini-review, we focus on summarizing the current state of regenerative organoid culture systems of the female and male reproductive tracts that model organ development, maintenance, and function. Specifically, we will introduce stem cell-based organoid models of the ovary/fallopian tube, endometrium, cervix, prostate gland, and testes. We will also describe organoid systems of the pre-implanting blastocyst and trophoblast, as the blastocyst and its extraembryonic trophectoderm are central to fetal, maternal, and overall pregnancy health. We describe the foundational studies leading to their development and outline the utility as well as specific limitations that are unique and common to many of these in vitro platforms.