Stem Cell Reports最新文献

In mammals, X chromosome dosage is balanced between sexes through the silencing of one X chromosome in females. Recent single-cell RNA sequencing analysis demonstrated that the inactivation of the X chromosome is accompanied by the upregulation of the active X chromosome (Xa) during mouse embryogenesis. Here, we have investigated if the reactivation of inactive-X (Xi) leads to the loss of Xa upregulation in different cellular or developmental contexts. We find that while Xi reactivation and loss of Xa upregulation are tightly coupled in mouse embryonic epiblast and induced pluripotent stem cells, that is not the case in germ cells. Moreover, we demonstrate that partial reactivation of Xi in mouse extra-embryonic endoderm stem cells and human B cells does not result in the loss of Xa upregulation. Finally, we have established a mathematical model for the transcriptional coordination of two X chromosomes. Together, we conclude that the reactivation of Xi is not always synchronized with the loss of Xa upregulation.

The oral cavity is a multifunctional organ composed of structurally heterogeneous mucosal tissues that remain poorly characterized. Oral mucosal tissues are highly stratified and segmented along an epithelial-lamina propria axis. Here, we performed spatial transcriptomics (tomo-seq) on the tongue, cheeks, and palate of the adult mouse to understand the cues that maintain the oral mucosal sites. We define molecular markers of unique and shared cellular niches and differentiation programs across oral sites. Using a comparative approach, we identify fibroblast growth factor (FGF) pathway components as potential stem cell niche factors for oral epithelial stem cells. Using organoid-forming efficiency assays, we validated three FGF ligands (FGF1, FGF7, and FGF10) as site-specific niche factors in the dorsal and ventral tongue. Our dataset of the spatially resolved genes across major oral sites represents a comprehensive resource for unraveling the molecular mechanisms underlying the adult homeostasis of the oral mucosa and its stem cell niches.

The key amendment to the Act on the Safety of Regenerative Medicine in June 2024 is regarding on-site inspections and the criteria for disqualifying the Certified Special Committees for Regenerative Medicine and Certified Committees for Regenerative Medicine. Appropriate regulations are needed after the legal amendment to stop the widespread use of unproven interventions and move away from the concept of a "Therapeutic Haven."

Hematopoietic stem cells (HSCs) develop from hemogenic endothelial cells (HECs) during mouse embryogenesis. Understanding the signaling molecules required for HSC development is crucial for the in vitro derivation of HSCs. We previously induced HSCs from embryonic HECs, isolated at embryonic day 10.5 (E10.5), in serum-free culture conditions with stem cell factor, thrombopoietin, and an endothelial feeder layer. Here, we aimed to elucidate signal requirements for inducing HSCs from earlier-stage HECs. Single-cell RNA sequencing (RNA-seq) analysis detected bone morphogenetic protein (BMP) signaling activation in E9.5 HECs. Adding BMP4 to the culture conditions led to the induction of HSCs from E9.5 HECs. Furthermore, isolating BMP4 receptor-expressing HECs from E9.5 embryos enriched progenitors with HSC-forming ability. This study identified BMP4 as an essential factor promoting the differentiation of early HECs into HSCs, opening up new possibilities for the in vitro derivation of HSCs.

The production of mature functioning thyroid follicular cells (TFCs) from human induced pluripotent stem cells (iPSCs) is critical for potential novel therapeutic approaches to post-surgical and congenital hypothyroidism. To accomplish this, we developed a novel human iPSC line that expresses fluorophores targeted to the NKX2-1 and PAX8 loci, allowing for the identification and purification of cells destined to become TFCs. Optimizing a sequence of defined, serum-free media to promote stepwise developmental directed differentiation, we found that bone morphogenic protein 4 (BMP4) and fibroblast growth factor 2 (FGF2) stimulated lineage specification into TFCs from multiple iPSC lines. Single-cell RNA sequencing demonstrated that BMP4 withdrawal after lineage specification promoted TFC maturation, with mature TFCs representing the majority of cells present within 1 month. After xenotransplantation into athyreotic immunodeficient mice, engrafted cells exhibited thyroid follicular organization with thyroglobulin protein detected in the lumens of NKX2-1-positive follicles. While our iPSC-derived TFCs presented durable expression of thyroid-specific proteins, they were unable to rescue hypothyroidism in vivo.

Genetic prion diseases are caused by mutations in PRNP, which encodes the prion protein (PrP^C). Why these mutations are pathogenic, and how they alter the properties of PrP^C are poorly understood. We have consented and accessed 22 individuals of a multi-generational Israeli family harboring the highly penetrant E200K PRNP mutation and generated a library of induced pluripotent stem cells (iPSCs) representing nine carriers and four non-carriers. iPSC-derived neurons from E200K carriers display abnormal synaptic architecture characterized by misalignment of postsynaptic NMDA receptors with the cytoplasmic scaffolding protein PSD95. Differentiated neurons from mutation carriers do not produce PrP^Sc, the aggregated and infectious conformer of PrP, suggesting that loss of a physiological function of PrP^C may contribute to the disease phenotype. Our study shows that iPSC-derived neurons can provide important mechanistic insights into the pathogenesis of genetic prion diseases and can offer a powerful platform for testing candidate therapeutics.

Understanding the molecular mechanisms of epicardial epithelial-to-mesenchymal transition (EMT), particularly in directing cell fate toward epicardial derivatives, is crucial for regenerative medicine using human induced pluripotent stem cell (iPSC)-derived epicardium. Although transforming growth factor β (TGF-β) plays a pivotal role in epicardial biology, orchestrating EMT during embryonic development via downstream signaling through SMAD proteins, the function of SMAD proteins in the epicardium in maintaining vascular homeostasis or mediating the differentiation of various epicardial-derived cells (EPDCs) is not yet well understood. Our study reveals that TGF-β-independent SMAD3 expression autonomously predicts epicardial cell specification and lineage maintenance, acting as a key mediator in promoting the angiogenic-oriented specification of the epicardium into cardiac pericyte progenitors. This finding uncovers a novel role for SMAD3 in the human epicardium, particularly in generating cardiac pericyte progenitors that enhance cardiac microvasculature angiogenesis. This insight opens new avenues for leveraging epicardial biology in developing more effective cardiac regeneration strategies.

Translating genetic findings for neurodevelopmental and psychiatric disorders (NPDs) into actionable disease biology would benefit from large-scale and unbiased functional studies of NPD genes. Leveraging the cytosine base editing (CBE) system, we developed a pipeline for clonal loss-of-function (LoF) allele mutagenesis in human induced pluripotent stem cells (hiPSCs) by introducing premature stop codons (iSTOP) that lead to mRNA nonsense-mediated decay (NMD) or protein truncation. We tested the pipeline for 23 NPD genes on 3 hiPSC lines and achieved highly reproducible, efficient iSTOP editing in 22 genes. Using RNA sequencing (RNA-seq), we confirmed their pluripotency, absence of chromosomal abnormalities, and NMD. Despite high editing efficiency, three schizophrenia risk genes (SETD1A, TRIO, and CUL1) only had heterozygous LoF alleles, suggesting their essential roles for cell growth. We found that CUL1-LoF reduced neurite branches and synaptic puncta density. This iSTOP pipeline enables a scaled and efficient LoF mutagenesis of NPD genes, yielding an invaluable shareable resource.

Neural degeneration is a hallmark of spinal cord injury (SCI). Multipotent neural precursor cells (NPCs) have the potential to reconstruct the damaged neuron-glia network due to their tri-lineage capacity to generate neurons, astrocytes, and oligodendrocytes. However, astrogenesis is the predominant fate of resident or transplanted NPCs in the SCI milieu adding to the abundant number of resident astrocytes in the lesion. How NPC-derived astrocytes respond to the inflammatory milieu of SCI and the mechanisms by which they contribute to the post-injury recovery processes remain largely unknown. Here, we uncover that activated NPC-derived astrocytes exhibit distinct molecular signature that is immune modulatory and foster neurogenesis, neuronal maturity, and synaptogenesis. Mechanistically, NPC-derived astrocytes perform regenerative matrix remodeling by clearing inhibitory chondroitin sulfate proteoglycans (CSPGs) from the injury milieu through LAR and PTP-σ receptor-mediated endocytosis and the production of ADAMTS1 and ADAMTS9, while most resident astrocytes are pro-inflammatory and contribute to the pathologic deposition of CSPGs. These novel findings unravel critical mechanisms of NPC-mediated astrogenesis in SCI repair.

Each pluripotent stem cell line has a physical entity as well as a digital phenotype, but linking the two unambiguously is confounded by poor naming practices and assumed knowledge. Registration gives each line a unique and persistent identifier that links to phenotypic data generated over the lifetime of that line. Registration is a key recommendation of the 2023 ISSCR Standards for the use of human stem cells in research. Here we consider how community adoption of stem cell line registration could facilitate the establishment of integrated digital phenotypes of specific human pluripotent stem cell (hPSC) lines.