Expression Of Reprogramming Factors Research Articles

Inverse genetics tracing the differentiation pathway of human chondrocytes

ObjectiveMammalian somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) via the forced expression of Yamanaka reprogramming factors. However, only a limited population of the cells that pass through a particular pathway can metamorphose into iPSCs, while the others do not. This study aimed to clarify the pathways that chondrocytes follow during the reprogramming process. DesignThe fate of human articular chondrocytes under reprogramming was investigated through a time-coursed single-cell transcriptomic analysis, which we termed an inverse genetic approach. The iPS interference technique was also employed to verify that chondrocytes inversely return to pluripotency following the proper differentiation pathway. ResultsWe confirmed that human chondrocytes could be converted into cells with an iPSC phenotype. Moreover, it was clarified that a limited population that underwent the silencing of SOX9, a master gene for chondrogenesis, at a specific point during the proper transcriptome transition pathway, could eventually become iPSCs. Interestingly, the other cells, which failed to be reprogrammed, followed a distinct pathway toward cells with a surface zone chondrocyte phenotype. The critical involvement of cellular communication network factors (CCNs) in this process was indicated. The idea that chondrocytes, when reprogrammed into iPSCs, follow the differentiation pathway backward was supported by the successful iPS interference using SOX9. ConclusionsThis inverse genetic strategy may be useful for seeking candidates for the master genes for the differentiation of various somatic cells. The utility of CCNs in articular cartilage regeneration is also supported.

Reprogramming Pancreatic Ductal Adenocarcinoma to Pluripotency.

The generation of induced pluripotent stem cells (iPSCs) using transcription factors has been achieved from almost any differentiated cell type and has proved highly valuable for research and clinical applications. Interestingly, iPSC reprogramming of cancer cells, such as pancreatic ductal adenocarcinoma (PDAC), has been shown to revert the invasive PDAC phenotype and override the cancer epigenome. The differentiation of PDAC-derived iPSCs can recapitulate PDAC progression from its early pancreatic intraepithelial neoplasia (PanIN) precursor, revealing the molecular and cellular changes that occur early during PDAC progression. Therefore, PDAC-derived iPSCs can be used to model the earliest stages of PDAC for the discovery of early-detection diagnostic markers. This is particularly important for PDAC patients, who are typically diagnosed at the late metastatic stages due to a lack of reliable biomarkers for the earlier PanIN stages. However, reprogramming cancer cell lines, including PDAC, into pluripotency remains challenging, labor-intensive, and highly variable between different lines. Here, we describe a more consistent protocol for generating iPSCs from various human PDAC cell lines using bicistronic lentiviral vectors. The resulting iPSC lines are stable, showing no dependence on the exogenous expression of reprogramming factors or inducible drugs. Overall, this protocol facilitates the generation of a wide range of PDAC-derived iPSCs, which is essential for discovering early biomarkers that are more specific and representative of PDAC cases.

An engineered ligand-responsive Csy4 endoribonuclease controls transgene expression from Sendai virus vectors

BackgroundViral vectors are attractive gene delivery vehicles because of their broad tropism, high transduction efficiency, and durable expression. With no risk of integration into the host genome, the vectors developed from RNA viruses such as Sendai virus (SeV) are especially promising. However, RNA-based vectors have limited applicability because they lack a convenient method to control transgene expression by an external inducer.ResultsWe engineered a Csy4 switch in Sendai virus-based vectors by combining Csy4 endoribonuclease with mutant FKBP12 (DD: destabilizing domain) that becomes stabilized when a small chemical Shield1 is supplied. In this Shield1-responsive Csy4 (SrC) switch, Shield1 increases Csy4 fused with DD (DD-Csy4), which then cleaves and downregulates the transgene mRNA containing the Csy4 recognition sequence (Csy4RS). Moreover, when Csy4RS is inserted in the viral L gene, the SrC switch suppresses replication and transcription of the SeV vector in infected cells in a Shield1-dependent manner, thus enabling complete elimination of the vector from the cells. By temporally controlling BRN4 expression, a BRN4-expressing SeV vector equipped with the SrC switch achieves efficient, stepwise differentiation of embryonic stem cells into neural stem cells, and then into astrocytes.ConclusionSeV-based vectors with the SrC switch should find wide applications in stem cell research, regenerative medicine, and gene therapy, especially when precise control of reprogramming factor expression is desirable.

Partial Cell Reprogramming as a Method of Revitalizing Living Systems

Aging and associated diseases are an acute problem of modern biology and medicine. Although aging cannot be prevented at present, its impact on the lifespan and health of the elderly can potentially be minimized by interventions aimed at returning these cellular processes to normal functioning. The ongoing search for ways to rejuvenate and improve the regenerative capacity of cells led to the discovery of partial reprogramming in 2016. Partial reprogramming is based on the short-term expression of reprogramming factors (Oct4, Sox2, Klf4 and c-Myc). As a result, the young epigenetic signature of aging cells is restored. The efficacy of the method has been shown in both in vitro and in vivo systems. In this review we discuss the main successes of partial reprogramming, as well as the problems and unresolved issues faced by the researchers. Separately, we focus on the data on molecular changes during partial reprogramming. The method of partial reprogramming provides a wide range of opportunities for fundamental research of aging and rejuvenation. Further work in this direction can lead to the development of therapeutic strategies to alleviate age-related diseases and thus improve health and longevity.

Epidermal growth factor receptor regulates lineage plasticity driving transformation to small cell lung cancer

Epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) is clinically and genetically heterogeneous, with concurrent RB1/TP53 mutations, indicating an increased risk of transformation into small cell lung cancer (SCLC). When tumor cells convert into a different histological subtype, they lose their dependence on the original oncogenic driver, resulting in therapeutic resistance. However, the molecular details associated with this transformation remain unclear. It has been difficult to define molecular mechanisms of neuroendocrine (NE) transformation in lung cancer due to a lack of pre- and post-transformation clinical samples. In this study, we established a NSCLC cell line with concurrent RB1/TP53 mutations and built corresponding patient-derived xenograft (PDX) models to investigate the mechanisms underlying transformation to SCLC. Studying these PDX models, we demonstrate that EGFR loss facilitates lineage plasticity of lung adenocarcinoma initiated by biallelic mutations of TP53 and RB1. Gene expression analysis of these EGFR knockout tumors revealed altered expression of neuroendocrine synapse-associated lineage genes. There is an increased expression of epigenetic reprogramming factors like Sox2 and gene associated with neural development like NTRK in these EGFR knockout tumors. These findings uncovered the role of EGFR in the acquisition of plasticity, which is the ability of a cell to substantially modify its identity and take on a new phenotype, and defined a novel landscape of potential drivers of NE transformation in lung cancer.

Improved Cardiac Function in Postischemic Rats Using an Optimized Cardiac Reprogramming Cocktail Delivered in a Single Novel Adeno-Associated Virus.

Cardiac reprogramming is a technique to directly convert nonmyocytes into myocardial cells using genes or small molecules. This intervention provides functional benefit to the rodent heart when delivered at the time of myocardial infarction or activated transgenically up to 4 weeks after myocardial infarction. Yet, several hurdles have prevented the advancement of cardiac reprogramming for clinical use. Through a combination of screening and rational design, we identified a cardiac reprogramming cocktail that can be encoded in a single adeno-associated virus. We also created a novel adeno-associated virus capsid that can transduce cardiac fibroblasts more efficiently than available parental serotypes by mutating posttranslationally modified capsid residues. Because a constitutive promoter was needed to drive high expression of these cell fate-altering reprogramming factors, we included binding sites to a cardiomyocyte-restricted microRNA within the 3' untranslated region of the expression cassette that limits expression to nonmyocytes. After optimizing this expression cassette to reprogram human cardiac fibroblasts into induced cardiomyocyte-like cells in vitro, we also tested the ability of this capsid/cassette combination to confer functional benefit in acute mouse myocardial infarction and chronic rat myocardial infarction models. We demonstrated sustained, dose-dependent improvement in cardiac function when treating a rat model 2 weeks after myocardial infarction, showing that cardiac reprogramming, when delivered in a single, clinically relevant adeno-associated virus vector, can support functional improvement in the postremodeled heart. This benefit was not observed with GFP (green fluorescent protein) or a hepatocyte reprogramming cocktail and was achieved even in the presence of immunosuppression, supporting myocyte formation as the underlying mechanism. Collectively, these results advance the application of cardiac reprogramming gene therapy as a viable therapeutic approach to treat chronic heart failure resulting from ischemic injury.

Abstract P1116: Histone Deacetylase Complexes Regulate Direct Cardiac Conversion From Human Fibroblasts

Direct cardiac reprogramming is a promising approach to generate functional cardiomyocytes from non-myocytes for regenerative medicine, drug screening, and disease modeling. This method involves the transformation of specialized cells into functional cardiomyocytes using specific transcription factors or molecular signals. Epigenetic modulators, such as histone deacetylase (HDAC) complexes, may play a critical role in chromatin remodeling underlying cardiac reprogramming. To investigate the role of HDAC complexes in direct cardiac conversion, induced cardiomyocyte-like cells (iCMs) were derived from human fibroblasts through ectopic expression of reprogramming factors, and the changes of histone acetylation were evaluated by western blotting. The results showed decreased levels of H3K9ac, H3K14ac, and H3K27ac along with direct cardiac reprogramming, suggesting the significant chromatin remodeling and gene regulation. A loss-of-function screen of all the components associated with HDAC complex was performed to determine the responsible histone acetylation modifiers. The screen results showed that most of the HDAC components are necessary for direct cardiac reprogramming. Further investigation focused on a newly identified HDAC complex, mitotic deacetylase complex (MiDAC), consisting of mitotic deacetylase associated SANT domain protein MiDEAS (ELMSAN1), DNTTIP1, and HDAC1. Knocking down each of the MiDAC components led to similar reprogramming repression and cell death, indicating that MiDAC plays a critical role in cardiac reprogramming. In addition, the expression analysis of DNTTIP1 and HDAC1 showed a gradual decrease throughout the conversion, while ELMSAN1 diminished at the early stage of reprogramming, suggesting that ELMSAN1 is likely required for MiDAC stability. Furthermore, overexpression of ELMSAN1 significantly improved reprogramming efficiency and led to the increase of H3K9ac, H3K14ac, and H3K27ac levels globally, suggesting that ELMSAN1 and MiDAC might be responsible for the regulation of such histone modifications during the process. Overall, our findings provide novel insights into the epigenetic regulation of direct cardiac reprogramming and reveal the potential role of MiDAC in this process.

CircHULC accelerates the growth of human liver cancer stem cells by enhancing chromatin reprogramming and chromosomal instability via autophagy

BackgroundAlthough CircHULC was overexpressed in several cancers, the role of CircHULC in malignancies has yet to be elucidated. MethodsGene infection, tumorigenesis test in vitro and in vivo and the signaling pathway analysis were performed. Resultsour results indicate that CircHULC promotes growth of human liver cancer stem cells and the malignant differentiation of hepatocyte-like cells. Mechanistically, CircHULC enhances the methylation modification of PKM2 via CARM1 and the deacetylase Sirt1. Moreover, CircHULC enhances the binding ability of TP53INP2/DOR with LC3 and LC3 with ATG4, ATG3, ATG5, ATG12. Therefore, CircHULC promotes the formation of autophagosomes. In particular, the binding ability of phosphorylated Beclin1 (Ser14) to Vps15, Vps34, ATG14L were significantly increased after CircHULC was overexpressed. Strikingly, CircHULC affects the expression of chromatin reprogramming factors and oncogenes through autophagy. Thereafter, Oct4, Sox2, KLF4, Nanog, and GADD45 were significantly decreased and C-myc was increased after CircHULC was overexpressed. Thus, CircHULC promotes the expression of H-Ras, SGK, P70S6K, 4E-BP1, Jun, and AKT. Interestingly, both CARM1 and Sirt1 determine the cancerous function of CircHULC dependent on autophagy. Conclusionswe shed light on the fact that the targeted attenuation of deregulated functioning of CircHULC could be a viable approach for cancer treatment, and CircHULC may acts as the potential biomarker and therapeutic target for liver cancer.

Generation of induced pluripotent stem cell (iPSC) from NY-ESO-I-specific cytotoxic T cells isolated from the melanoma patient with minor HLAs: The practical pilot study for the adoptive immunotherapy for melanoma using iPSC technology.

Melanoma is one of the most severe skin cancers, derived from melanocytes. Among various therapies for melanoma, adoptive immunotherapy using tumor-infiltrating lymphocytes/chimeric antigen receptor-T cells (TCs) is advanced in recent years; however, the efficacy is still limited, and major challenges remain in terms of safety and cell supply. To solve the issues of adoptive immunotherapy, we utilized induced pluripotent stem cells (iPSCs), which have an unlimited proliferative ability and various differentiation capability. First, we monoclonally isolated CD8+ TCs specifically reactive with NY-ESO-1, one of tumor antigens, from the melanoma patient's monocytes after stimulated with NY-ESO-1 peptide by manual procedure, and cultured NY-ESO-1-specific TCs until proliferated and formed colonies. iPSCs were consequently generated from colony-forming TCs by exogenous expression of reprogramming factors using Sendai virus vector. After the RAG2 gene in TC-derived iPSCs (T-iPSCs) was knocked out for preventing T-cell receptor (TCR) rearrangement, T-iPSCs were re-differentiated into rejuvenated cytotoxic TCs. We confirmed that TCR of T-iPSC-derived TC was maintained as the same of original TCs. In conclusion, T-iPSCs have a potential to be an unlimited cell source for providing cytotoxic TCs. Our study could be a "touchstone" to develop iPSC-based adoptive immunotherapy for the treatment of melanoma for the future clinical use.

An Alternate Approach to Generate Induced Pluripotent Stem Cells with Precise CRISPR/Cas9 Tool.

The induced pluripotent stem cells (iPSCs) are considered powerful tools in pharmacology, biomedicine, toxicology, and cell therapy. Multiple approaches have been used to generate iPSCs with the expression of reprogramming factors. Here, we generated iPSCs by integrating the reprogramming cassette into a genomic safe harbor, CASH-1, with the use of a precise genome editing tool, CRISPR/Cas9. The integration of cassette at CASH-1 into target cells did not alter the pattern of proliferation and interleukin-6 secretion as a response to ligands of multiple signaling pathways involving tumor necrosis factor-α receptor, interleukin-1 receptor, and toll-like receptors. Moreover, doxycycline-inducible expression of OCT4, SOX2, and KLF4 reprogrammed engineered human dermal fibroblasts and human embryonic kidney cell line into iPSCs. The generated iPSCs showed their potential to make embryoid bodies and differentiate into the derivatives of all three germ layers. Collectively, our data emphasize the exploitation of CASH-1 by CRISPR/Cas9 tool for therapeutic and biotechnological applications including but not limited to reprogramming of engineered cells into iPSCs.

Probing cell identity hierarchies by fate titration and collision during direct reprogramming.

Despite the therapeutic promise of direct reprogramming, basic principles concerning fate erasure and the mechanisms to resolve cell identity conflicts remain unclear. To tackle these fundamental questions, we established a single‐cell protocol for the simultaneous analysis of multiple cell fate conversion events based on combinatorial and traceable reprogramming factor expression: Collide‐seq. Collide‐seq revealed the lack of a common mechanism through which fibroblast‐specific gene expression loss is initiated. Moreover, we found that the transcriptome of converting cells abruptly changes when a critical level of each reprogramming factor is attained, with higher or lower levels not contributing to major changes. By simultaneously inducing multiple competing reprogramming factors, we also found a deterministic system, in which titration of fates against each other yields dominant or colliding fates. By investigating one collision in detail, we show that reprogramming factors can disturb cell identity programs independent of their ability to bind their target genes. Taken together, Collide‐seq has shed light on several fundamental principles of fate conversion that may aid in improving current reprogramming paradigms.

Investigating Peripheral Regional Anesthesia Using Induced Pluripotent Stem Cell Technology: Exploring Novel Terrain.

Investigating Peripheral Regional Anesthesia Using Induced Pluripotent Stem Cell Technology: Exploring Novel Terrain.

Mechanical signals induces reprogramming of mature adipocytes through the YAP/TAZ-binding motif

Tissue engineering technology will be the main approach to tissue regeneration in the future and are promising for the treatment of large-area burns and refractory wounds. Dedifferentiated fat cells (DFAT) derived from mature adipocytes (MAs) as a seed cell have great potential in cell therapy and tissue engineering for the treatment of a variety of clinical diseases because of their wider availability, stronger proliferation ability, multidirectional redifferentiation potential, higher cell purity, lower heterogeneity, and greater biosafety profile. However, the triggering mechanism for MAs reprogramming in vitro is unclear. In this study, MAs were successfully induced to dedifferentiate into DFAT in a short time in vitro using an “improved ceiling culture method". Flow cytometry, adipogenic, and osteogenic differentiation experiments verified that DFAT cells present the biological characteristics of stem cells. In addition, changing the stiffness of the extracellular matrix can inhibit the dedifferentiation of MAs to DFAT, and increase the expression of Yes-associated protein/transcriptional co-activator with the PDZ-binding motif (YAP/TAZ), nuclear translocation, and the expression of reprogramming transcription factors. In conclusion, extracellular matrix stiffness can induce MAs to dedifferentiate into DFAT in vitro, and can directly transmit mechanical force signals to the nucleus via YAP/TAZ binding to trigger the expression of stem cell-related reprogramming factors.

In vivo partial reprogramming alters age-associated molecular changes during physiological aging in mice.

Partial reprogramming by expression of reprogramming factors (Oct4, Sox2, Klf4 and c-Myc) for short periods of time restores a youthful epigenetic signature to aging cells and extends the life span of a premature aging mouse model. However, the effects of longer-term partial reprogramming in physiologically aging wild-type mice are unknown. Here, we performed various long-term partial reprogramming regimens, including different onset timings, during physiological aging. Long-term partial reprogramming lead to rejuvenating effects in different tissues, such as the kidney and skin, and at the organismal level; duration of the treatment determined the extent of the beneficial effects. The rejuvenating effects were associated with a reversion of the epigenetic clock and metabolic and transcriptomic changes, including reduced expression of genes involved in the inflammation, senescence and stress response pathways. Overall, our observations indicate that partial reprogramming protocols can be designed to be safe and effective in preventing age-related physiological changes. We further conclude that longer-term partial reprogramming regimens are more effective in delaying aging phenotypes than short-term reprogramming.

Structurally-discovered KLF4 variants accelerate and stabilize reprogramming to pluripotency

SummaryNon-genetically modified somatic cells can only be inefficiently and stochastically reprogrammed to pluripotency by exogenous expression of reprogramming factors. Low competence of natural reprogramming factors may prevent the majority of cells to successfully and synchronously reprogram. Here we screened DNA-interacting amino acid residues in the zinc-finger domain of KLF4 for enhanced reprogramming efficiency using alanine-substitution scanning methods. Identified KLF4 L507A mutant accelerated and stabilized reprogramming to pluripotency in both mouse and human somatic cells. By testing all the variants of L507 position, variants with smaller amino acid residues in the KLF4 L507 position showed higher reprogramming efficiency. L507A bound more to promoters or enhancers of pluripotency genes, such as KLF5, and drove gene expression of these genes during reprogramming. Molecular dynamics simulations predicted that L507A formed additional interactions with DNA. Our study demonstrates how modifications in amino acid residues of DNA-binding domains enable next-generation reprogramming technology with engineered reprogramming factors.

Expression of reprogramming factors in mesenchymal stem cells isolated from equine umbilical cord Wharton’s jelly and amniotic fluid

Stem cells represent the most promising population for regenerative cell therapy and have gained much attention during the recent past. Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into trilineages. Like haematopoietic cells, mesenchymal cells have been shown to proliferate and form fibroblast-like colonies in vitro. Despite major progress in our general knowledge related to the application of adult stem cells, finding alternative sources for bone marrow MSCs has remained a challenge. A wide diversity of isolation procedures for mesenchymal stromal cells from various tissues of the placenta, umbilical cord and Wharton's jelly have been described for humans and other species. In this study, we isolated established umbilical cord Wharton’s jelly as a primary source for isolation of mesenchymal stem cells since it is a rich source of stem cells and no ethical concerns are involved. Equine umbilical cord Wharton’s jelly segments were collected during foaling time and digested enzymatically and cultured in-vitro in culture medium. In addition to the study of their morphology and colony forming units, the expression of reprogramming factors by the isolated MSCs were also studied. The isolated MSCs were observed to be plastic adherent, clonogenic and their morphology were polygonal, star shaped and fibroblast like. They revealed a strong expression of pluripotent stemness markers OCT-4, SOX-2, Nanog and KLF-4. From the current study, it can be concluded that Wharton's jelly is a rich source of stem cells with stemness properties expressing the reprogramming factors and mesenchymal like morphology and could be used as an alternate for the bone marrow derived mesenchymal stem cells for cell based regenerative therapies.

Continuous expression of reprogramming factors induces and maintains mouse pluripotency without specific growth factors and signaling inhibitors.

ObjectivesDerivation and maintenance of pluripotent stem cells (PSCs) generally require optimized and complex culture media, which hinders the derivation of PSCs from various species. Expression of Oct4, Sox2, Klf4, and c‐Myc (OSKM) can reprogram somatic cells into induced PSCs (iPSCs), even for species possessing no optimal culture condition. Herein, we explored whether expression of OSKM could induce and maintain pluripotency without PSC‐specific growth factors and signaling inhibitors.MethodsThe culture medium of Tet‐On‐OSKM/Oct4‐GFP mouse embryonic stem cells (ESCs) was switched from N2B27 with MEK inhibitor, GSK3β inhibitor, and leukemia inhibitory factor (LIF) (2iL) to N2B27 with doxycycline. Tet‐On‐OSKM mouse embryonic fibroblast (MEF) cells were reprogrammed in N2B27 with doxycycline. Cell proliferation was traced. Pluripotency was assessed by expression of ESC marker genes, teratoma, and chimera formation. RNA‐Seq was conducted to analyze gene expression.ResultsVia continuous expression of OSKM, mouse ESCs (OSKM‐ESCs) and the resulting iPSCs (OSKM‐iPSCs) reprogrammed from MEF cells propagated stably, expressed pluripotency marker genes, and formed three germ layers in teratomas. Transcriptional landscapes of OSKM‐iPSCs resembled those of ESCs cultured in 2iL and were more similar to those of ESCs cultured in serum/LIF. Furthermore, OSKM‐iPSCs contributed to germline transmission.ConclusionsExpression of OSKM could induce and maintain mouse pluripotency without specific culturing factors. Importantly, OSKM‐iPSCs could produce gene‐modified animals through germline transmission, with potential applications in other species.

Transient reprogramming of postnatal cardiomyocytes to a dedifferentiated state.

In contrast to mammals, lower vertebrates are capable of extraordinary myocardial regeneration thanks to the ability of their cardiomyocytes to undergo transient dedifferentiation and proliferation. Somatic cells can be temporarily reprogrammed to a proliferative, dedifferentiated state through forced expression of Oct3/4, Sox2, Klf4 and c-Myc (OSKM). Here, we aimed to induce transient reprogramming of mammalian cardiomyocytes in vitro utilising an OSKM-encoding non-integrating vector. Reprogramming factor expression in postnatal rat and mouse cardiomyocytes triggered rapid but limited cell dedifferentiation. Concomitantly, a significant increase in cell viability, cell cycle related gene expression and Ki67 positive cells was observed consistent with an enhanced cell cycle activation. The transient nature of this partial reprogramming was confirmed as cardiomyocyte-specific cell morphology, gene expression and contractile activity were spontaneously recovered by day 15 after viral transduction. This study provides the first evidence that adenoviral OSKM delivery can induce partial reprogramming of postnatal cardiomyocytes. Therefore, adenoviral mediated transient reprogramming could be a novel and feasible strategy to recapitulate the regenerative mechanisms of lower vertebrates.

Inhibition of EZH2 primes the cardiac gene activation via removal of epigenetic repression during human direct cardiac reprogramming

Cardiovascular disease, until now, is still the leading cause of death in the United States. Due to the limited regenerative capacity of adult hearts, the damage caused by heart injury cannot be reversed and eventually progress into heart failure. In need of cardiovascular disease treatment, many therapies aimed at either cell transplantation or cell regeneration have been proposed. Direct reprogramming of somatic cells into induced cardiomyocytes (iCMs) is considered to be a promising strategy for regenerative medicine. The induction of cardiomyocytes from non-myocytes can be achieved efficiently via ectopic expression of reprogramming factors both in vitro and in vivo in the mouse model, however, the generation of human induced cardiomyocyte-like cells (hiCMs) remains challenging. The inefficiency of hiCMs production called for the identification of the additional epigenetic memories in non-myocytes which might be damping the hiCM reprogramming. Here, we conducted an unbiased loss-of-function screening focusing on epigenetic regulators and identified enhancer of zeste homolog 2 (EZH2) as an important epigenetic barrier during hiCM reprogramming. We found that the removal of EZH2 via genetic knockdown or treatment of EZH2 selective degrader significantly increased the hiCM reprogramming efficiency and led to profound activation of cardiac genes and repression of collagen and extracellular matrix genes. Furthermore, EZH2 inhibitors targeting its catalytic activity also promotes hiCM reprogramming, suggesting that EZH2 may restrain cardiac conversion through H3K27me3-mediated gene repression. Indeed, genomic profiling of H3K27me3 revealed a subset of cardiac genes that remain repressed with high levels of H3K27me3 despite of the delivery of the reprogramming factors. Inhibition of EZH2, however, leads to reduced H3K27me3 occupancy and robust activation of these cardiac genes. Taken together, our data suggested that EZH2 inhibition facilitates the activation of cardiac genes in fibroblasts and eases the production of hiCMs.

Generation of human induced pluripotent stem cell (iPSC) lines (UUMCBi001-A, UUMCBi002-A) from two healthy donors.

Availability of numerous high-quality iPSC lines is needed to overcome donor-associated variability caused by genetic background effects. We generated two human iPSC lines from dermal fibroblasts of two healthy females using Sendai virus reprogramming. Quality assessment of the iPSC lines confirmed the expression of pluripotency markers, trilineage differentiation capacity and absence of exogenous expression of reprogramming factors. Both iPSC lines were genetically stable with a genotype that matched the fibroblast lines of donors. These iPSC lines add to available reference lines as a resource for disease modeling of polygenic and multifactorial diseases, for evaluation of differentiation protocols and toxicology screening.