Derivation and applications of human hepatocyte-like cells

Human hepatocyte-like cells (HLCs) derived from human pluripotent stem cells (hPSCs) promise a valuable source of cells with human genetic background, physiologically relevant liver functions, and unlimited supply. With over 10 years’ efforts in this field, great achievements have been made. HLCs have been successfully derived and applied in disease modeling, toxicity testing and drug discovery. Large cohorts of induced pluripotent stem cells-derived HLCs have been recently applied in studying population genetics and functional outputs of common genetic variants in vitro. This has offered a new paradigm for genomewide association studies and possibly in vitro pharmacogenomics in the nearly future. However, HLCs have not yet been successfully applied in bioartificial liver devices and have only displayed limited success in cell transplantation. HLCs still have an immature hepatocyte phenotype and exist as a population with great heterogeneity, and HLCs derived from different hPSC lines display variable differentiation efficiency. Therefore, continuous improvement to the quality of HLCs, deeper investigation of relevant biological processes, and proper adaptation of recent advances in cell culture platforms, genome editing technology, and bioengineering systems are required before HLCs can fulfill the needs in basic and translational research. In this review, we summarize the discoveries, achievements, and challenges in the derivation and applications of HLCs.

Genetically modified pigs:Emerging animal models for hereditary hearing loss

Hereditary hearing loss(HHL),a genetic disorder that impairs auditory function,significantly affects quality of life and incurs substantial economic losses for society.To investigate the underlying causes of HHL and evaluate therapeutic outcomes,appropriate animal models are necessary.Pigs have been extensively used as valuable large animal models in biomedical research.In this review,we highlight the advantages of pig models in terms of ear anatomy,inner ear morphology,and electrophysiological characteristics,as well as recent advancements in the development of distinct genetically modified porcine models of hearing loss.Additionally,we discuss the prospects,challenges,and recommendations regarding the use pig models in HHL research.Overall,this review provides insights and perspectives for future studies on HHL using porcine models.

Stem Cell-Based Hair Cell Regeneration and Therapy in the Inner Ear

Hearing loss has become increasingly prevalent and causes considerable disability,thus gravely burdening the global economy.Irreversible loss of hair cells is a main cause of sensorineural hearing loss,and currently,the only relatively effective clinical treatments are limited to digital hearing equipment like cochlear implants and hearing aids,but these are of limited benefit in patients.It is therefore urgent to understand the mechanisms of damage repair in order to develop new neuroprotective strategies.At present,how to promote the regeneration of functional hair cells is a key scientific question in the field of hearing research.Multi-ple signaling pathways and transcriptional factors trigger the activation of hair cell progenitors and ensure the maturation of newborn hair cells,and in this article,we first review the principal mechanisms underlying hair cell reproduction.We then further discuss therapeutic strategies involving the co-regulation of multiple signaling pathways in order to induce effective functional hair cell regeneration after degeneration,and we summarize current achievements in hair cell regeneration.Lastly,we discuss potential future approaches,such as small molecule drugs and gene therapy,which might be applied for regenerating functional hair cells in the clinic.

Ionically Imprinting-Based Copper(Ⅱ)Label-Free Detection for Preventing Hearing Loss

Copper is a microelement with important physiological functions in the body.However,the excess copper ion(Cu^(2+))may cause severe health problems,such as hair cell apoptosis and the resultant hearing loss.Therefore,the assay of Cu^(2+)is important.We integrate ionic imprinting technology(IIT)and structurally colored hydrogel beads to prepare chitosan-based ionically imprinted hydrogel beads(IIHBs)as a low-cost and high-specificity platform for Cu^(2+)detection.The IIHBs have a macroporous microstructure,uniform size,vivid structural color,and magnetic responsiveness.When incubated in solution,IIHBs recognize Cu^(2+)and exhibit a reflective peak change,thereby achieving label-free detection.In addition,benefiting from the IIT,the IIHBs display good specificity and selectivity and have an imprinting factor of 19.14 at 100μmol·L^(-1).These features indicated that the developed IIHBs are promising candidates for Cu^(2+)detection,particularly for the prevention of hearing loss.

Unraveling brain aging through the lens of oral microbiota

The oral cavity is a complex physiological community encompassing a wide range of microorganisms.Dysbiosis of oral microbiota can lead to various oral infectious diseases,such as periodontitis and tooth decay,and even affect systemic health,including brain aging and neurodegenerative diseases.Recent studies have highlighted how oral microbes might be involved in brain aging and neurodegeneration,indicating potential avenues for intervention strategies.In this review,we summarize clinical evidence demonstrating a link between oral microbes/oral infectious diseases and brain aging/neurodegenerative diseases,and dissect potential mechanisms by which oral microbes contribute to brain aging and neurodegeneration.We also highlight advances in therapeutic development grounded in the realm of oral microbes,with the goal of advancing brain health and promoting healthy aging.

Conductive PS inverse opals for regulating proliferation and differentiation of neural stem cells

The development of neural tissue engineering has brought new hope to the treatment of spinal cord injury(SCI).Up to date,various scaffolds have been developed to induce the oriented growth and arrangement of nerves to facilitate the repair after injury.In this work,a conductive and anisotropic inverse opal substrate was presented by modifying polystyrene(PS)inverse opal films with carbon nanotubes and then stretching them to varying degrees.The film had good biocompatibility,and neural stem cells(NSCs)grown on the film displayed good orientation along the stretching direction.In addition,benefiting from the conductivity and anisotropy of the film,NSCs differentiated into neurons significantly.These results suggest that the conductive and anisotropic PS inverse opal substrates possess value in nerve tissue engineering regeneration.

Immunity-and-matrix-regulatory cells enhance cartilage regeneration for meniscus injuries: a phase I dose-escalation trial

Immunity-and-matrix-regulatory cells(IMRCs)derived from human embryonic stem cells have unique abilities in modulating immunity and regulating the extracellular matrix,which could be mass-produced with stable biological properties.Despite resemblance to mesenchymal stem cells(MSCs)in terms of self-renew and tri-lineage differentiation,the ability of IMRCs to repair the meniscus and the underlying mechanism remains undetermined.Here,we showed that IMRCs demonstrated stronger immunomodulatory and pro-regenerative potential than umbilical cord MSCs when stimulated by synovial fluid from patients with meniscus injury.Following injection into the knees of rabbits with meniscal injury,IMRCs enhanced endogenous fibrocartilage regeneration.In the dose-escalating phase I clinical trial(NCT03839238)with eighteen patients recruited,we found that intra-articular IMRCs injection in patients was safe over 12 months post-grafting.Furthermore,the effective results of magnetic resonance imaging(MRI)of meniscus repair and knee functional scores suggested that 5×107 cells are optimal for meniscus injury treatment.In summary,we present the first report of a phase I clinical trial using IMRCs to treat meniscus injury.Our results demonstrated that intra-articular injection of IMRCs is a safe and effective therapy by providing a permissive niche for cartilage regeneration.

CRL2^(APPBP2)-mediated TSPYL2 degradation counteracts human mesenchymal stem cell senescence

Cullin-RING E3 ubiquitin ligases(CRLs),the largest family of multi-subunit E3 ubiquitin ligases in eukaryotic cells,represent core cellular machinery for executing protein degradation and maintaining proteostasis.Here,we asked what roles Cullin proteins play in human mesenchymal stem cell(hMSC)homeostasis and senescence.To this end,we conducted a comparative aging phenotype analysis by individually knocking down Cullin members in three senescence models:replicative senescent hMSCs,Hutchinson-Gilford Progeria Syndrome hMSCs,and Werner syndrome hMSCs.Among all family members,we found that CUL2 deficiency rendered hMSCs the most susceptible to senescence.To investigate CUL2-specific underlying mechanisms,we then applied CRISPR/Cas9-mediated gene editing technology to generate CUL2-deficient human embryonic stem cells(hESCs).When we differentiated these into h MSCs,we found that CUL2 deletion markedly accelerates hMSC senescence.Importantly,we identified that CUL2 targets and promotes ubiquitin proteasome-mediated degradation of TSPYL2(a known negative regulator of proliferation)through the substrate receptor protein APPBP2,which in turn downregulates one of the canonical aging marker-P21^(waf1/cip1),and thereby delays senescence.Our work provides important insights into how CRL2^(APPBP2)-mediated TSPYL2 degradation counteracts hMSC senescence,providing a molecular basis for directing intervention strategies against aging and aging-related diseases.

Genome-edited rabbits:Unleashing the potential of a promising experimental animal model across diverse diseases

Animal models are extensively used in all aspects of biomedical research,with substantial contributions to our understanding of diseases,the development of pharmaceuticals,and the exploration of gene functions.The field of genome modification in rabbits has progressed slowly.However,recent advancements,particularly in CRISPR/Cas9-related technologies,have catalyzed the successful development of various genome-edited rabbit models to mimic diverse diseases,including cardiovascular disorders,immunodeficiencies,agingrelated ailments,neurological diseases,and ophthalmic pathologies.These models hold great promise in advancing biomedical research due to their closer physiological and biochemical resemblance to humans compared to mice.This review aims to summarize the novel gene-editing approaches currently available for rabbits and present the applications and prospects of such models in biomedicine,underscoring their impact and future potential in translational medicine.

Advance and Application of Single‑cell Transcriptomics in Auditory Research

Hearing loss and deafness,as a worldwide disability disease,have been troubling human beings.However,the auditory organ of the inner ear is highly heterogeneous and has a very limited number of cells,which are largely uncharacterized in depth.Recently,with the development and utilization of single-cell RNA sequencing(scRNA-seq),researchers have been able to unveil the complex and sophisticated biological mechanisms of various types of cells in the auditory organ at the single-cell level and address the challenges of cellular heterogeneity that are not resolved through by conventional bulk RNA sequencing(bulk RNAseq).Herein,we reviewed the application of scRNA-seq technology in auditory research,with the aim of providing a reference for the development of auditory organs,the pathogenesis of hearing loss,and regenerative therapy.Prospects about spatial transcriptomic scRNA-seq,single-cell based genome,and Live-seq technology will also be discussed.

Telomere-dependent and telomereindependent roles of RAP1 in regulating human stem cell homeostasis

RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclea匚 Here we generated RAP1 -deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via directed differentiation. In both hMSCs and hNSCs, RAP1 not only negatively regulated telomere length but also acted as a transcriptional regulator of RELN by tuning the methylation status of its gene promoter. RAP1 deficiency enhanced self-renewal and delayed senescence in hMSCs, but not in hNSCs, suggesting complicated lineage-specific effects of RAP1 in adult stem cells.Altogether, these results demonstrate for the first time that RAP1 plays both telomeric and nontelomeric roles in regulating human stem cell homeostasis.

Dual human iPSC-derived cardiac lineage cell-seeding extracellular matrix patches promote regeneration and long-term repair of infarcted hearts

Human pluripotent stem cell-derived cardiovascular progenitor cells (hCVPCs) and cardiomyocytes (hCMs) possess therapeutic potential for infarcted hearts;however, their efficacy needs to be enhanced. Here we tested the hypotheses that the combination of decellularized porcine small intestinal submucosal extracellular matrix (SIS-ECM) with hCVPCs, hCMs, or dual of them (Mix, 1:1) could provide better therapeutic effects than the SIS alone, and dual hCVPCs with hCMs would exert synergic effects in cardiac repair. The data showed that the SIS patch well supported the growth of hCVPCs and hCMs. Epicardially implanted SIS-hCVPC, SIS-hCM, or SIS-Mix patches at 7-day post-myocardial infarction significantly ameliorated functional worsening, ventricular dilation and scar formation at 28- and 90-day post-implantation in C57/B6 mice, whereas the SIS only mildly improved function at 90-day post-implantation. Moreover, the SIS and SIS-cell patches improved vascularization and suppressed MI-induced cardiomyocyte hypertrophy and expression of Col1 and Col3, but only the SIS-hCM and the SIS-Mix patches increased the ratio of collagen III/I fibers in the infarcted hearts. Further, the SIS-cell patches stimulated cardiomyocyte proliferation via paracrine action. Notably, the SIS-Mix had better improvements in cardiac function and structure, engraftments, and cardiomyocyte proliferation. Proteomic analysis showed distinct biological functions of exclusive proteins secreted from hCVPCs and hCMs, and more exclusive proteins secreted from co-cultivated hCVPCs and hCMs than mono-cells involving in various functional processes essential for infarct repair. These findings are the first to demonstrate the efficacy and mechanisms of mono- and dual-hCVPC- and hCM-seeding SIS-ECM for repair of infarcted hearts based on the side-by-side comparison.

MSC-mediated mitochondrial transfer restores mitochondrial DNA and function in neural progenitor cells of Leber’s hereditary optic neuropathy

Leber’s hereditary optic neuropathy(LHON)is a debilitating mitochondrial disease associated with mutations in mitochondrial DNA(mtDNA).Unfortunately,the available treatment options for LHON patients are limited due to challenges in mitochondrial replacement.In our study,we reprogramming LHON urine cells into induced pluripotent stem cells(iPSCs)and differentiating them into neural progenitor cells(NPCs)and neurons for disease modeling.Our research revealed that LHON neurons exhibited significantly higher levels of mtDNA mutations and reduced mitochondrial function,confirming the disease phenotype.However,through co-culturing LHON iPSC-derived NPCs with mesenchymal stem cells(MSCs),we observed a remarkable rescue of mutant mtDNA and a significant improvement in mitochondrial metabolic function in LHON neurons.These findings suggest that co-culturing with MSCs can enhance mitochondrial function in LHON NPCs,even after their differentiation into neurons.This discovery holds promise as a potential therapeutic strategy for LHON patients.

Exosomes from antler stem cells alleviate mesenchymal stem cell senescence and osteoarthritis

Dear Editor,Stem cell therapy holds enormous and revolutionary promise to treat various age-related diseases,such as diabetes,heart failure,and Parkinson’s disease.However,low retention and survival rate of delivered stem cells,partially due to immunological rejection,constitute major hurdles for the clinical implementation of stem cell therapy(Lei et al.,2021a).Since mounting evidence showed that several types of stem cells mainly exert their therapeutic effects through the secretion of paracrine effects,exosomes,which are released by stem cells and execute most paracrine functions,have begun to draw attention in the field(Tran and Damaser,2015).Exosomes are membrane-enclosed vesicles with an average diameter of∼100 nanometers secreted by the cells,containing cytokines.

Programmable synthetic receptors:the next-generation of cell and gene therapies

Cell and gene therapies hold tremendous promise for treating a range of difficult-to-treat diseases.However,concerns over the safety and efficacy require to be further addressed in order to realize their full potential.Synthetic receptors,a synthetic biology tool that can precisely control the function of therapeutic cells and genetic modules,have been rapidly developed and applied as a powerful solution.Delicately designed and engineered,they can be applied to finetune the therapeutic activities,i.e.,to regulate production of dosed,bioactive payloads by sensing and processing user-defined signals or biomarkers.This review provides an overview of diverse synthetic receptor systems being used to reprogram therapeutic cells and their wide applications in biomedical research.With a special focus on four synthetic receptor systems at the forefront,including chimeric antigen receptors(CARs)and synthetic Notch(synNotch)receptors,we address the generalized strategies to design,construct and improve synthetic receptors.Meanwhile,we also highlight the expanding landscape of therapeutic applications of the synthetic receptor systems as well as current challenges in their clinical translation.

Regeneration of immunocompetent B lymphopoiesis from pluripotent stem cells guided by transcription factors

Regeneration of functional B lymphopoiesis from pluripotent stem cells(PSCs)is challenging,and reliable methods have not been developed.Here,we unveiled the guiding role of three essential factors,Lhx2,Hoxa9,and Runx1,the simultaneous expression of which preferentially drives B lineage fate commitment and in vivo B lymphopoiesis using PSCs as a cell source.In the presence of Lhx2,Hoxa9,and Runx1 expression,PSC-derived induced hematopoietic progenitors(iHPCs)immediately gave rise to pro/pre-B cells in recipient bone marrow,which were able to further differentiate into entire B cell lineages,including innate B-1a,B-1b,and marginal zone B cells,as well as adaptive follicular B cells.In particular,the regenerative B cells produced adaptive humoral immune responses,sustained antigen-specific antibody production,and formed immune memory in response to antigen challenges.The regenerative B cells showed natural B cell development patterns of immunoglobulin chain switching and hypermutation via cross-talk with host T follicular helper cells,which eventually formed T cell-dependent humoral responses.This study exhibits de novo evidence that B lymphopoiesis can be regenerated from PSCs via an HSC-independent approach,which provides insights into treating B cell-related deficiencies using PSCs as an unlimited cell resource.

Proteins in DNA methylation and their role in neural stem cell proliferation and differentiation

Background:Epigenetic modifications,namely non-coding RNAs,DNA methylation,and histone modifications such as methylation,phosphorylation,acetylation,ubiquitylation,and sumoylation play a significant role in brain development.DNA methyltransferases,methyl-CpG binding proteins,and ten-eleven translocation proteins facilitate the maintenance,interpretation,and removal of DNA methylation,respectively.Different forms of methylation,including 5-methylcytosine,5-hydroxymethylcytosine,and other oxidized forms,have been detected by recently developed sequencing technologies.Emerging evidence suggests that the diversity of DNA methylation patterns in the brain plays a key role in fine-tuning and coordinating gene expression in the development,plasticity,and disorders of the mammalian central nervous system.Neural stem cells(NSCs),originating from the neuroepithelium,generate neurons and glial cells in the central nervous system and contribute to brain plasticity in the adult mammalian brain.Main body:Here,we summarized recent research in proteins responsible for the establishment,maintenance,interpretation,and removal of DNA methylation and those involved in the regulation of the proliferation and differentiation of NSCs.In addition,we discussed the interactions of chemicals with epigenetic pathways to regulate NSCs as well as the connections between proteins involved in DNA methylation and human diseases.Conclusion:Understanding the interplay between DNA methylation and NSCs in a broad biological context can facilitate the related studies and reduce potential misunderstanding.

Dynamic cell transition and immune response landscapes of axolotl limb regeneration revealed by single-cell analysis

Dear Editor,The axolotl,Ambystoma mexicanum,has extraordinary capability to fully recover multiple tissues after lost,whereas such capability has disappeared in mammals.Thus,deci-phering detailed mechanisms underlying axolotl regenera-tion could provide valuable lessons for regenerative medicine.However,many questions,such as the origin of essential progenitor cells and key responses of individual types of cells for regeneration remain elusive(Haas and Whited,2017).Newly developed single-cell RNA sequenc-ing(scRNA-seq)method enables researchers to observe cellular and molecular dynamics in axolotl regeneration at the single-cell resolution(Gerber et al.,2018;Leigh et al.,2018),but the reported transcriptome landscapes are only for certain cell types or in certain regenerative stages.A complete overview of the regeneration process for all cell types is still lacking.

MAVS Antagonizes Human Stem Cell Senescence as a Mitochondrial Stabilizer

Mitochondrial dysfunction is a hallmark feature of cellular senescence and organ aging.Here,we asked whether the mitochondrial antiviral signaling protein(MAVS),which is essential for driving antiviral response,also regulates human stem cell senescence.To answer this question,we used CRISPR/Cas9-mediated gene editing and directed differentiation techniques to generate various MAVS-knockout human stem cell models.We found that human mesenchymal stem cells(hMSCs)were sensitive to MAVS deficiency,as manifested by accelerated senescence phenotypes.We uncovered that the role of MAVS in maintaining mitochondrial structural integrity and functional homeostasis depends on its interaction with the guanosine triphosphatase optic atrophy type 1(OPA1).Depletion of MAVS or OPA1 led to the dysfunction of mitochondria and cellular senescence,whereas replenishment of MAVS or OPA1 in MAVS-knockout hMSCs alleviated mitochondrial defects and premature senescence phenotypes.Taken together,our data underscore an uncanonical role of MAVS in safeguarding mitochondrial homeostasis and antagonizing human stem cell senescence.

Human ESC-derived vascular cells promote vascular regeneration in a HIF-1α dependent manner

Hypoxia-inducible factor(HIF-1α),a core transcription factor responding to changes in cellular oxygen levels,is closely associated with a wide range of physiological and pathological conditions.However,its differential impacts on vascular cell types and molecular programs modulating human vascular homeostasis and regeneration remain largely elusive.Here,we applied CRISPR/Cas9-mediated gene editing of human embryonic stem cells and directed differentiation to generate HIF-ia-deficient human vascular cells including vascular endothelial cells,vascular smooth muscle cells,and mesenchymal stem cells(MsCs),as a platform for discovering cell type-specific hypox-ia-induced response mechanisms.Through comparative molecular profiling across cell types under normoxic and hypoxic conditions,we provide insight into the indispensable role of HIF-1αin the promotion of ischemic vascular regeneration.We found human MSCs to be the vascular cell type most susceptible to HIF-1a deficiency,and that transcriptional inactivation of ANKZF1,an effector of HIF-1a,impaired pro-angiogenic processes.Altogether,our findings deepen the understanding of HIF-ia in human angiogenesis and support further explorations of novel therapeutic strategies of vascular regeneration against ischemic damage.