Stem Cell Reports最新文献

Cell communication via signaling exchange plays a pivotal role in multicellular development for building up functional tissues and organs. In the Drosophila testis, a pair of somatic cyst cells (CCs) encapsulate the germline that differentiates through close-range EGFR signaling activation. The Dlg/Scrib/Lgl polarity complex and clathrin-mediated endocytosis attenuate EGFR signaling in CCs, and loss of their function leads to EGFR overactivation and death of the neighboring germ cells. Here, we show that EGFR overactivation leads to upregulation of JNK and p38 signaling in CCs and ROS levels in germ cells destined to die. Our data uncover a bidirectional-feedback mechanism between JNK signaling and ROS who regulate each other, while reducing the levels of either JNK or ROS restored germ cell survival. This study provides a framework of how polarity and cellular trafficking regulate the output of multiple signaling responses cell-intrinsically and across cells, to coordinate tissue-specific responses and maintain homeostasis.

Organ-on-chips (OoCs) are controlled microfluidic platforms that replicate specific organ-level functionalities and pathological processes using cultured cells. OoCs promise to enhance drug discovery, reduce dependence on animal models, and enable personalized treatments. However, OoCs also introduce ethical challenges. This article provides a mapping review of the philosophical and ethical issues associated with developing and using OoCs. Given the limited literature on OoC ethics, the review takes a comparative analytical approach, drawing on organoid, digital twin, and precision medicine literature. Ethical issues are categorized across three consecutive phases-research, clinical testing, and implementation. Nine key themes are identified: privacy and confidentiality, informed consent, evidence, ontology and moral status, animal experimentation, evidence standards, patient care, intellectual property and commercialization, and distributive justice. Overall, the review highlights several key challenges that require further normative inquiry and hold significance for both research and policy. These include underrepresented groups in OoC research, complexities and limitations related to different consent models, the need for clear criteria to determine evidence standards for replacing animal models, accountability in the standardization of OoC research, and sustainability.

The self-renewal and differentiation of spermatogonial stem cells (SSCs) play essential roles in spermatogenesis. Extracellular vesicle (EV) is a universal strategy for intercellular communications in stem cell niches. However, the involvement of EVs in regulating SSCs remains largely unknown. This study revealed that testis EVs from postnatal day 7 (PND7) neonatal mouse testis guided spermatogonia into a transit-amplifying state with increased proliferation while retaining their differentiation potential. We profiled the repertoires of proteins and small RNAs by proteomic and small RNA transcriptomic analyses, respectively. We further showed that the EVs secreted by undifferentiated spermatogonia and the Sertoli cell lines, but not from more differentiated germ cell lines, conveyed let-7b/7c microRNA (miRNA) cargoes to spermatogonia, which mediated the effect of EVs on spermatogonial transit amplification. Together, this study has deciphered crucial let-7b/7c cargoes of EV-mediated communication within the spermatogonial niche, providing a new insight into the regulation of SSCs and spermatogenesis.

The initiation of synovial joint development and subsequent differentiation of progenitor cells toward anatomically and functionally distinct joint tissues are not well understood, despite being highly relevant to joint health and disease. We generated a dual reporter mouse embryonic stem cell (mESC) line to quantify cells expressing growth differentiation factor five (Gdf5), an early marker of joint formation, and Prg4, a lubricating proteoglycan found in joint tissues. Transforming growth factor β (TGF-β) signaling was necessary and sufficient for the induction of Gdf5-RFP and Prg4-GFP. Inhibition of either Wnt or MAPK signaling significantly increased the induction of Gdf5-RFP, while activation of either pathway prohibited this induction. Single cell transcriptomics demonstrated the chondrogenic identity of Gdf5+ cells in in vitro cultures and in mouse embryonic limb buds. We validated the roles of these signaling pathways in joint-specific ex vivo limb bud cultures. Thus, this in vitro model enhances our understanding of joint development and offers new insights into potential therapeutic approaches for joint disorders.

Long noncoding RNAs in gene desert regions remain largely uncharacterized despite their potential regulatory roles in cell differentiation. Here, we identify LINC01612 as a crucial modulator of human definitive endoderm differentiation. LINC01612 exhibits stage-specific expression and lacks protein-coding potential during endoderm differentiation. Depletion of LINC01612, through either short hairpin RNA (shRNA)-mediated knockdown or promoter deletion, severely impairs human endoderm differentiation. Mechanistically, LINC01612 interacts with DVL2, a WNT regulator essential for early development, and enhances DVL2 protein stability by reducing its ubiquitination. Loss of LINC01612 or DVL2 impairs WNT signaling, while both WNT activation and DVL2 overexpression can rescue endoderm differentiation defect in the absence of LINC01612. These findings reveal the LINC01612-DVL2-WNT regulatory axis as a key modulator of human definitive endoderm differentiation.

Oligodendrocyte precursor cells (OPCs) display functional plasticity beyond myelination. Kuwata et al. explore how hypoxia shapes OPC features after ischemic stroke. Combining single-cell transcriptomics with in vivo and ex vivo models, they reveal oxygen-dependent OPC phenotypes promoting angiogenesis and remyelination, highlighting OPC versatility and potential for novel stroke cell therapies.

METTL3 is a key regulator of RNA metabolism, yet its genomic and epitranscriptomic roles in tissue development are largely unexplored. Using embryonic stem cell-derived 3D retinal organoids to model retinal progenitor cell (RPC) differentiation, we integrated transcriptome-wide m6A profiling (GLORI), protein-DNA (chromatin immunoprecipitation sequencing [ChIP-seq] and CUT&RUN) and chromatin accessibility (ATAC-seq) mapping, and targeted m6A engineering (dCas13b-FTO) to dissect METTL3 function. Loss of METTL3 nuclear m6A activity disrupted Rx+ retinal anlage formation in vitro, with dCas13b-FTO epitranscriptome engineering revealing that m6A at the Six3 3'UTR governs its stability. Surprisingly, while METTL3 loss altered histone modifications and chromatin accessibility, its direct chromatin targets showed little transcriptional correlation. A degron-based METTL3 degradation strategy, paired with protein-RNA interaction profiling, exposed rapid regulatory shifts in RPCs, revealing a METTL3-Ythdf1 protein-RNA axis. Our multi-omics approach establishes METTL3-dependent m6A as a critical epitranscriptomic layer in retinal development, unveiling a genomic paradigm in which chromatin accessibility diverges from transcriptional output.

Generation of in vitro human induced pluripotent cell (hiPSC)-derived skeletal muscle progenitor cells (SMPCs) holds great promise for regenerative medicine for skeletal muscle wasting diseases, for example Duchenne muscular dystrophy (DMD). While multiple approaches have been described to obtain SMPCs in vitro, hiPSC-derived SMPCs generated using transgene-free protocols are usually obtained in a low amount and resemble a more embryonal/fetal stage of differentiation. Here, we demonstrate that modulation of the JAK2/STAT3 signaling pathway during an in vitro skeletal muscle differentiation protocol increases the yield of PAX7⁺ and CD54⁺ human SMPCs (hSMPCs) and drives them to a higher maturation stage, in both human embryonic stem (ES) and patient-derived induced pluripotent cells (iPSCs). Importantly, the obtained SMPCs are able to differentiate into multinucleated myotubes in vitro and engraft in vivo. These findings reveal that modulation of the JAK2/STAT3 signaling pathway is a potential therapeutic avenue to generate SMPCs in vitro with potential for cell therapy approaches.

Hematopoietic stem and progenitor cells (HSPCs) maintain homeostasis of the blood system by balancing proliferation and differentiation. Many extrinsic signals in the bone marrow (BM) microenvironment that regulate this balance are still unknown. We report gamma-aminobutyric acid (GABA) metabolite produced in the BM as a regulator of HSPCs. Deletion of the genes encoding the glutamate decarboxylase enzymes (Gad1 and Gad2) that produce GABA in either B lineages or endothelial cells (ECs) led to a slight reduction in BM HSPCs but not GABA levels. However, simultaneous blockade of GABA production from both hematopoietic cells and ECs resulted in a greater reduction of HSPCs and a significant reduction of BM GABA levels. Lower GABA levels in the BM altered the gene expression profile of HSPCs, with expression reduced for proliferation-associated genes and increased for B lineage genes. Our findings suggest GABA from multiple sources coordinates to regulate HSPC activity.

Sex chromosomes shape male (XY)-female (XX) differences in development and disease. These differences can be modeled in vitro by comparing XY and XX human induced pluripotent stem cells (hiPSCs). However, in this system, inter-individual autosomal variation and unstable X-dosage compensation can confound identification of sex chromosomal effects. Here, we utilize sex chromosome loss in XXY fibroblasts to generate XX and XY hiPSCs that are autosomally isogenic and exhibit stable X-dosage compensation. We also create X-monosomic (XO) hiPSCs, to investigate X-Y dosage effects. Using these autosomally isogenic lines, we examine sex differences in pluripotent stem cell expression. Transcriptional differences between XX and XY hiPSCs are surprisingly modest. However, X-haploinsufficiency induces transcriptional deregulation predominantly affecting autosomes. This effect is mediated by Y-genes with broad housekeeping functions that have X-homologs escaping X inactivation. Our isogenic hiPSC lines provide a resource for exploring sex chromosome effects on development and disease in vitro.