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SummaryKnowledge of cell signaling pathways that drive human neural crest differentiation into craniofacial chondrocytes is incomplete,yet essential for using stem cells to regenerate craniomaxillofacial structures. To accelerate translational progress,we developed a differentiation protocol that generated self-organizing craniofacial cartilage organoids from human embryonic stem cell-derived neural crest stem cells. Histological staining of cartilage organoids revealed tissue architecture and staining typical of elastic cartilage. Protein and post-translational modification (PTM) mass spectrometry and snRNA-seq data showed that chondrocyte organoids expressed robust levels of cartilage extracellular matrix (ECM) components: many collagens,aggrecan,perlecan,proteoglycans,and elastic fibers. We identified two populations of chondroprogenitor cells,mesenchyme cells and nascent chondrocytes,and the growth factors involved in paracrine signaling between them. We show that ECM components secreted by chondrocytes not only create a structurally resilient matrix that defines cartilage,but also play a pivotal autocrine cell signaling role in determining chondrocyte fate. Graphical abstract Highlights•Craniofacial cartilage organoids were grown from human neural crest stem cells•These organoids exhibited elastic cartilage architecture and characteristic markers•Paracrine signaling drove chondrogenesis in mesenchyme cells and nascent chondrocytes•ECM components cemented chondrocyte cell fate through autocrine signaling Natural sciences; Biological sciences; Biochemistry; Cell biology; Stem cells research; Specialized functions of cells View Publication

Development requires coordinated interactions between the epiblast,which generates the embryo proper; the trophectoderm,which generates the placenta; and the hypoblast,which forms both the anterior signalling centre and the yolk sac. These interactions remain poorly understood in human embryogenesis because mechanistic studies have only recently become possible. Here we examine signalling interactions post-implantation using human embryos and stem cell models of the epiblast and hypoblast. We find anterior hypoblast specification is NODAL dependent,as in the mouse. However,while BMP inhibits anterior signalling centre specification in the mouse,it is essential for its maintenance in human. We also find contrasting requirements for BMP in the naive pre-implantation epiblast of mouse and human embryos. Finally,we show that NOTCH signalling is important for human epiblast survival. Our findings of conserved and species-specific factors that drive these early stages of embryonic development highlight the strengths of comparative species studies. Weatherbee,Weberling,Gantner et al. find contrasting requirements for BMP in the anterior signalling centre and pre-implantation epiblast between mice and humans. They further find that NOTCH may be indispensable for human epiblast survival. View Publication

Abnormal trophoblast self-renewal and differentiation during early gestation is the major cause of miscarriage,yet the underlying regulatory mechanisms remain elusive. Here,we show that trophoblast specific deletion of Kat8,a MYST family histone acetyltransferase,leads to extraembryonic ectoderm abnormalities and embryonic lethality. Employing RNA-seq and CUT&Tag analyses on trophoblast stem cells (TSCs),we further discover that KAT8 regulates the transcriptional activation of the trophoblast stemness marker,CDX2,via acetylating H4K16. Remarkably,CDX2 overexpression partially rescues the defects arising from Kat8 knockout. Moreover,increasing H4K16ac via using deacetylase SIRT1 inhibitor,EX527,restores CDX2 levels and promoted placental development. Clinical analysis shows reduced KAT8,CDX2 and H4K16ac expression are associated with recurrent pregnancy loss (RPL). Trophoblast organoids derived from these patients exhibit impaired TSC self-renewal and growth,which are significantly ameliorated with EX527 treatment. These findings suggest the therapeutic potential of targeting the KAT8-H4K16ac-CDX2 axis for mitigating RPL,shedding light on early gestational abnormalities. Embryo implantation failure is a leading cause of miscarriage,though the mechanisms underlying trophoblast defects are not well understood. Here they show that the histone acetyltransferase KAT8 is essential for proper activation of the trophoblast stemness gene CDX2,and that placental development can be partially rescued by inhibiting histone deacetylase activity. View Publication

Stem cell fate decisions,including proliferation,differentiation,morphological changes,and viability,are impacted by microenvironmental cues such as physical and biochemical signals. However,the specific impact of matrix elasticity on kidney cell development and function remains less understood due to the lack of models that can closely recapitulate human kidney biology. An established protocol to differentiate podocytes from human-induced pluripotent stem (iPS) cells provides a promising avenue to elucidate the role of matrix elasticity in kidney tissue development and lineage determination. In this study,we synthesized polyacrylamide hydrogels with different stiffnesses and investigated their ability to promote podocyte differentiation and biomolecular characteristics. We found that 3 kPa and 10 kPa hydrogels significantly support the adhesion,differentiation,and viability of podocytes. Differentiating podocytes on a more compliant (0.7 kPa) hydrogel resulted in significant cell loss and detachment. Further investigation of the mechanosensitive proteins yes-associated protein (YAP) and synaptopodin revealed nuanced molecular distinctions in cellular responses to matrix elasticity that may otherwise be overlooked if morphology and cell spreading alone were used as the primary metric for selecting matrices for podocyte differentiation. Specifically,hydrogels with kidney-like rigidities outperformed traditional tissue culture plates at modulating the molecular-level expression of active mechanosensitive proteins critical for podocyte health and function. These findings could guide the development of physiologically relevant platforms for kidney tissue engineering,disease modeling,and mechanistic studies of organ physiology and pathophysiology. Such advances are critical for realizing the full potential of in vitro platforms in accurately predicting human biological responses. View Publication

Creation of disease models utilizing hiPSCs in combination with CRISPR/Cas9 gene editing enable mechanistic insights into differential pharmacological responses. This allows translation of efficacy and safety findings from a healthy to a diseased state and provides a means to predict clinical outcome sooner during drug discovery. Calcium handling disturbances including reduced expression levels of the type 2 ryanodine receptor (RYR2) are linked to cardiac dysfunction; here we have created a RYR2 deficient human cardiomyocyte model that mimics some aspects of heart failure. RYR2 deficient cardiomyocytes show differential pharmacological responses to L-type channel calcium inhibitors. Phenotypic and proteomic characterization reveal novel molecular insights with altered expression of structural proteins including CSRP3,SLMAP,and metabolic changes including upregulation of the pentose phosphate pathway and increased sensitivity to redox alterations. This genetically engineered in vitro cardiovascular model of RYR2 deficiency supports the study of pharmacological responses in the context of calcium handling and metabolic dysfunction enabling translation of drug responses from healthy to perturbed cellular states. View Publication

HiBiT is an engineered luciferase’s 11-amino-acid component that can be introduced as a tag at either terminus of a protein of interest. When the LgBiT component and a substrate are present,HiBiT and LgBiT dimerize forming a functional luciferase. The HiBiT technology has been extensively used for high-throughput protein turnover studies in cells. Here,we have adapted the use of the HiBiT technology to quantify messenger RNA (mRNA) translation temporally in vitro in the rabbit reticulocyte system and in cellulo in HEK293 cells constitutively expressing LgBiT. The assay system can uniquely detect differences in cap,5?UTR,modified nucleotide composition,coding sequence optimization and poly(A) length,and their effects on mRNA translation over time. Importantly,using these assays we established the optimal mRNA composition varied depending on the encoded protein of interest,highlighting the importance of screening methods tailored to the protein of interest,and not reliant on reporter proteins. Our findings demonstrated that HiBiT can be easily and readily adapted to monitor real-time mRNA translation in live cells and offers a novel and highly favourable method for the development of mRNA-based therapeutics. View Publication

Human induced pluripotent stem cells (hiPSCs) derived into neurons offer a powerful in vitro model to study cellular processes. One method to characterize functional network properties of these cells is using multielectrode arrays (MEAs). MEAs can measure the electrophysiological activity of cellular cultures for extended periods of time without disruption. Here we used WTC11 hiPSCs with a doxycycline-inducible neurogenin 2 (NGN2) transgene differentiated into neurons co-cultured with primary human astrocytes. We achieved a synchrony index ?0.9 in as little as six-weeks with a mean firing rate of ?13 Hz. Previous reports show that derived 3D brain organoids can take several months to achieve similar strong network burst synchrony. We also used this co-culture to model aspects of blood-brain barrier breakdown by using human serum. Our fully human co-culture achieved strong network burst synchrony in a fraction of the time of previous reports,making it an excellent first pass,high-throughput method for studying network properties and neurodegenerative diseases. View Publication

Mohr-Tranebjaerg syndrome (MTS) is a rare X-linked recessive neurodegenerative disorder caused by mutations in the Translocase of Inner Mitochondrial Membrane 8A (TIMM8A) gene,which encodes TIMM8a,a protein localized to the mitochondrial intermembrane space (IMS). The pathophysiology of MTS remains poorly understood. To investigate the molecular mechanisms underlying MTS,we established induced pluripotent stem cells (iPSCs) from a male MTS patient carrying a novel TIMM8A mutation (c.225-229del,p.Q75fs95*),referred to as MTS-iPSCs. To generate an isogenic control,we introduced the same mutation into healthy control iPSCs (CTRL-iPSCs) using the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9 (CRISPR/Cas9),resulting in mutant iPSCs (MUT-iPSCs). We differentiated the three iPSC lines into neurons and evaluated their mitochondrial function and neuronal development. Both MTS- and MUT-iPSCs exhibited impaired neuronal differentiation,characterized by smaller somata,fewer branches,and shorter neurites in iPSC-derived neurons. Additionally,these neurons showed increased susceptibility to apoptosis under stress conditions,as indicated by elevated levels of cytochrome c and cleaved caspase-3. Mitochondrial function analysis revealed reduced protein levels and activity of complex IV,diminished ATP synthesis,and increased reactive oxygen species (ROS) generation in MTS- and MUT-neurons. Furthermore,transmission electron microscopy revealed mitochondrial fragmentation in MTS-neurons. RNA sequencing identified differentially expressed genes (DEGs) involved in axonogenesis,synaptic activity,and apoptosis-related pathways. Among these DEGs,coiled-coil-helix-coiled-coil-helix domain-containing 2 (CHCHD2),which encodes a mitochondrial IMS protein essential for mitochondrial homeostasis,was significantly downregulated in MTS-neurons. Western blot analysis confirmed decreased CHCHD2 protein levels in both MTS- and MUT-neurons. Overexpression of CHCHD2 rescued mitochondrial dysfunction and promoted neurite elongation in MTS-neurons,suggesting that CHCHD2 acts as a downstream effector of TIMM8a in the pathogenesis of MTS. In summary,loss-of-function of TIMM8a leads to a downstream reduction in CHCHD2 levels,collectively impairing neurogenesis by disrupting mitochondrial homeostasis. TIMM8a mutation (p.Q75fs95*) leads to mitochondrial dysfunction and neuronal defects in iPSC-derived neurons from patient with Mohr-Tranebjaerg syndrome,which are rescued by overexpression of CHCHD2. TIMM8a translocase of inner mitochondrial membrane 8a,CHCHD2 coiled-coil-helix-coiled-coil-helix domain-containing protein 2,MTS Mohr-Tranebjaerg syndrome,I mitochondrial complex I,II mitochondrial complex II,III mitochondrial complex III,IV mitochondrial complex IV,Q coenzyme Q10,Cyt c cytochrome c. View Publication

ABSTRACTThe ultimate aim of nuclear reprogramming is to provide stem cells or differentiated cells from unrelated cell types as a cell source for regenerative medicine. A popular route towards this is transcription factor induction,and an alternative way is an original procedure of transplanting a single somatic cell nucleus to an unfertilized egg. A third route is to transplant hundreds of cell nuclei into the germinal vesicle (GV) of a non-dividing Amphibian meiotic oocyte,which leads to the activation of silent genes in 24 h and robustly induces a totipotency-like state in almost all transplanted cells. We apply this third route for potential therapeutic use and describe a procedure by which the differentiated states of cells can be reversed so that totipotency and pluripotency gene expression are regained. Differentiated cells are exposed to GV extracts and are reprogrammed to form embryoid bodies,which shows the maintenance of stemness and could be induced to follow new directions of differentiation. We conclude that much of the reprogramming effect of eggs is already present in meiotic oocytes and does not require cell division or selection of dividing cells. Reprogrammed cells by oocytes could serve as replacements for defective adult cells in humans. Summary: Stem cell therapy has shed light on incurable diseases. We describe a novel method for cell reprogramming and provide personalized stem cell sources for stem cell therapies. View Publication

Introduction: The lack of functional hepatocytes poses a significant challenge for drug safety testing and therapeutic applications due to the inability of mature hepatocytes to expand and their tendency to lose functionality in vitro. Previous studies have demonstrated the potential of Human Liver Stem Cells (HLSCs) to differentiate into hepatocyte-like cells within an in vitro rotary cell culture system,guided by a combination of growth factors and molecules known to regulate hepatocyte maturation. In this study,we employed a matrix multi-assay approach to comprehensively characterize HLSC differentiation. Methods: We evaluated the expression of hepatic markers using qRT-PCR,immunofluorescence,and Western blot analysis. Additionally,we measured urea and FVIII secretion into the supernatant and developed an updated indocyanine green in vitro assay to assess hepatocyte functionality. Results: Molecular analyses of differentiated HLSC aggregates revealed significant upregulation of hepatic genes,including CYP450,urea cycle enzymes,and uptake transporters exclusively expressed on the sinusoidal side of mature hepatocytes,evident as early as 1 day post-differentiation. Interestingly,HLSCs transiently upregulated stem cell markers during differentiation,followed by downregulation after 7 days. Furthermore,differentiated aggregates demonstrated the ability to release urea and FVIII into the supernatant as early as the first 24 h,with accumulation over time. Discussion: These findings suggest that a 3D rotation culture system may facilitate rapid hepatic differentiation of HLSCs. Despite the limitations of this rotary culture system,its unique advantages hold promise for characterizing HLSC GMP batches for clinical applications. View Publication

The cytoplasmic RIG-I-like receptors (RLRs) recognize viral RNA and initiate innate antiviral immunity. RLR signaling also triggers glycolytic reprogramming through glucose transporters (GLUTs),whose role in antiviral immunity is elusive. Here,we unveil that insulin-responsive GLUT4 inhibits RLR signaling independently of glucose uptake in adipose and muscle tissues. At steady state,GLUT4 is docked at the Golgi matrix by ubiquitin regulatory X domain 9 (UBXN9,TUG). Following RNA virus infection,GLUT4 is released and translocated to the cell surface where it spatially segregates a significant pool of cytosolic RLRs,preventing them from activating IFN-? responses. UBXN9 deletion prompts constitutive GLUT4 trafficking,sequestration of RLRs,and attenuation of antiviral immunity,whereas GLUT4 deletion heightens RLR signaling. Notably,reduced GLUT4 expression is uniquely associated with human inflammatory myopathies characterized by hyperactive interferon responses. Overall,our results demonstrate a noncanonical UBXN9-GLUT4 axis that controls antiviral immunity via plasma membrane tethering of cytosolic RLRs. View Publication

A reliable suspension-based platform for scaling engineered cardiac tissue (ECT) production from human induced pluripotent stem cells (hiPSCs) is crucial for regenerative therapies. Here,we compared the production and functionality of ECTs formed using our scaffold-based,engineered tissue microsphere differentiation approach with those formed using the prevalent scaffold-free aggregate platform. We utilized a microfluidic system for the rapid (1 million cells/min),high density (30,40,60 million cells/ml) encapsulation of hiPSCs within PEG-fibrinogen hydrogel microspheres. HiPSC-laden microspheres and aggregates underwent suspension-based cardiac differentiation in chemically defined media. In comparison to aggregates,microspheres maintained consistent size and shape initially,over time,and within and between batches. Initial size and shape coefficients of variation for microspheres were eight and three times lower,respectively,compared to aggregates. On day 10,microsphere cardiomyocyte (CM) content was 27 % higher and the number of CMs per initial hiPSC was 250 % higher than in aggregates. Contraction and relaxation velocities of microspheres were four and nine times higher than those of aggregates,respectively. Microsphere contractile functionality also improved with culture time,whereas aggregate functionality remained unchanged. Additionally,microspheres displayed improved ?-adrenergic signaling responsiveness and uniform calcium transient propagation. Transcriptomic analysis revealed that while both microspheres and aggregates demonstrated similar gene regulation patterns associated with cardiomyocyte differentiation,heart development,cardiac muscle contraction,and sarcomere organization,the microspheres exhibited more pronounced transcriptional changes over time. Taken together,these results highlight the capability of the microsphere platform for scaling up biomanufacturing of ECTs in a suspension-based culture platform. Graphical abstractImage 1 Highlights•Comparison of scaffold-based and scaffold-free 3D hiPSC cardiac differentiation.•Microsphere provided tighter control of size and shape with higher reproducibility.•Microspheres showed higher cardiomyocyte (CM) content and more CMs/initial hiPSC.•Microsphere contracted faster than aggregate with higher cell structural maturity.•Microsphere platform exhibited more pronounced transcriptional changes over time. View Publication