Reprogramming Of Fibroblasts Research Articles

Virus‐Engineered Microsol Electrospun Scaffold Promotes the Reprogramming of Fibroblasts to Neurons

AbstractLentiviral‐vector‐based therapies, widely used for treating various diseases, face limitations because of release burst, rapid clearance, and immune activation. Herein, a lentiviral vector delivery platform is proposed utilizing a virus‐engineered microsol electrospun scaffold. Identifying a remarkable upregulation of polypyrimidine tract binding protein1 (PTB) in spinal cord injury (SCI) rats, a scaffold is constructed comprising a hyaluronic acid (HA) core encapsulating brain‐derived neurotrophic factor (BDNF) and a polydopamine (PDA)‐modified linear poly‐l‐lactic acid (PLLA) shell, with shPTB lentiviral vectors (LV‐shPTB) grafted via PDA. In vitro, the LV‐shPTB achieves an infection efficiency of 70%, and the oriented scaffolds significantly reduce the expression of inflammatory factors, induce the reprogramming of fibroblasts into neurons, and sustain the release of BDNF for over 2 weeks. In vivo, the scaffolds provide physical support and neural guidance, as well as released BDNF and LV‐shPTB. LV‐shPTB delivery leads to the reprogramming of fibroblasts into neurons, and the sustained BDNF delivery maintains the neurons’ proliferation and growth, which further promotes the recovery of neurological function in SCI rats. These results demonstrate the potential application of virus‐engineered delivery platforms in SCI treatment and other medical fields.

Nicotinamide N-methyltransferase mediates lipofibroblast–myofibroblast transition and apoptosis resistance

Metabolism controls cellular phenotype and fate. In this report, we demonstrate that nicotinamide N-methyltransferase (NNMT), a metabolic enzyme that regulates developmental stem cell transitions and tumor progression, is highly expressed in human idiopathic pulmonary fibrosis (IPF) lungs, and is induced by the pro-fibrotic cytokine, transforming growth factor-β1 (TGF-β1) in lung fibroblasts. NNMT silencing reduces the expression of extracellular matrix proteins, both constitutively and in response to TGF-β1. Furthermore, NNMT controls the phenotypic transition from homeostatic, pro-regenerative lipofibroblasts to pro-fibrotic myofibroblasts. This effect of NNMT is mediated, in part, by the downregulation of lipogenic transcription factors, TCF21 and PPARγ, and the induction of a less proliferative but more differentiated myofibroblast phenotype. NNMT confers an apoptosis-resistant phenotype to myofibroblasts that is associated with the downregulation of pro-apoptotic members of the Bcl-2 family, including Bim and PUMA. Together, these studies indicate a critical role for NNMT in the metabolic reprogramming of fibroblasts to a pro-fibrotic and apoptosis-resistant phenotype and support the concept that targeting this enzyme may promote regenerative responses in chronic fibrotic disorders such as IPF.

Generation of iPSC lines from three Stargardt patients carrying bi-allelic ABCA4 variants

Stargardt disease, a progressive retinal disorder, is associated with bi-allelic variants in ABCA4, a protein that is expressed in the retina. Induced pluripotent stem cell lines (RMCGENi005-A, SCTCi018-A, SCTCi017-A) were generated by lentivirus reprogramming of fibroblasts derived from Stargardt patients carrying different bi-allelic ABCA4 variants. All the generated lines showed pluripotent characteristics and no chromosomal aberrations. The availability of these lines will allow us to generate patient-derived photoreceptor precursor cells and retinal organoids to further study ABCA4 and thereby, Stargardt disease in relevant model systems carrying the patient’s genetic background.

BayesTME: An end-to-end method for multiscale spatial transcriptional profiling of the tissue microenvironment.

Spatial variation in cellular phenotypes underlies heterogeneity in immune recognition and response to therapy in cancer and many other diseases. Spatial transcriptomics holds the potential to quantify such variation, but existing analysis methods are limited by their focus on individual tasks such as spot deconvolution. We present BayesTME, an end-to-end Bayesian method for analyzing spatial transcriptomics data. BayesTME unifies several previously distinct analysis goals under a single, holistic generative model. This unified approach enables BayesTME to deconvolve spots into cell phenotypes without any need for paired single-cell RNA-seq. BayesTME then goes beyond spot deconvolution to uncover spatial expression patterns among coordinated subsets of genes within phenotypes, which we term spatial transcriptional programs. BayesTME achieves state-of-the-art performance across myriad benchmarks. On human and zebrafish melanoma tissues, BayesTME identifies spatial transcriptional programs that capture fundamental biological phenomena such as bilateral symmetry and tumor-associated fibroblast and macrophage reprogramming. BayesTME is open source.

Role of vitamin C and SVCT2 in neurogenesis.

Different studies have established the fundamental role of vitamin C in proliferation, differentiation, and neurogenesis in embryonic and adult brains, as well as in in vitro cell models. To fulfill these functions, the cells of the nervous system regulate the expression and sorting of sodium-dependent vitamin C transporter 2 (SVCT2), as well as the recycling of vitamin C between ascorbic acid (AA) and dehydroascorbic acid (DHA) via a bystander effect. SVCT2 is a transporter preferentially expressed in neurons and in neural precursor cells. In developmental stages, it is concentrated in the apical region of the radial glia, and in adult life, it is expressed preferentially in motor neurons of the cerebral cortex, starting on postnatal day 1. In neurogenic niches, SVCT2 is preferentially expressed in precursors with intermediate proliferation, where a scorbutic condition reduces neuronal differentiation. Vitamin C is a potent epigenetic regulator in stem cells; thus, it can induce the demethylation of DNA and histone H3K27m3 in the promoter region of genes involved in neurogenesis and differentiation, an effect mediated by Tet1 and Jmjd3 demethylases, respectively. In parallel, it has been shown that vitamin C induces the expression of stem cell-specific microRNA, including the Dlk1-Dio3 imprinting region and miR-143, which promotes stem cell self-renewal and suppresses de novo expression of the methyltransferase gene Dnmt3a. The epigenetic action of vitamin C has also been evaluated during gene reprogramming of human fibroblasts to induced pluripotent cells, where it has been shown that vitamin C substantially improves the efficiency and quality of reprogrammed cells. Thus, for a proper effect of vitamin C on neurogenesis and differentiation, its function as an enzymatic cofactor, modulator of gene expression and antioxidant is essential, as is proper recycling from DHA to AA by various supporting cells in the CNS.

Direct cellular reprogramming and transdifferentiation of fibroblasts on wound healing-Fantasy or reality?

Induced pluripotent stem cell (iPSC) technology is one of the de novo approaches in regeneration medicine and has led to new research applications for wound healing in recent years. Fibroblasts have attracted wide attention as the first cell line used for differentiation into iPSCs. Researchers have found that fibroblasts can be induced into different types of cells in variable mediums or microenvironments. This indicates the potential "stem" characteristics of fibroblasts in terms of direct cellular reprogramming compared with the iPSC detour. In this review, we described the morphology and biological function of fibroblasts. The stem cell characteristics and activities of fibroblasts, including transdifferentiation into myofibroblasts, osteogenic cells, chondrogenic cells, neurons, and vascular tissue, are discussed. The biological values of fibroblasts are then briefly reviewed. Finally, we discussed the potential applications of fibroblasts in clinical practice.

PHDs-seq: a large-scale phenotypic screening method for drug discovery through parallel multi-readout quantification

High-throughput phenotypic screening is a cornerstone of drug development and the main technical approach for stem cell research. However, simultaneous detection of activated core factors responsible for cell fate determination and accurate assessment of directional cell transition are difficult using conventional screening methods that focus on changes in only a few biomarkers. The PHDs-seq (Probe Hybridization based Drug screening by sequencing) platform was developed to evaluate compound function based on their transcriptional effects in a wide range of signature biomarkers. In this proof-of-concept demonstration, several sets of markers related to cell fate determination were profiled in adipocyte reprogramming from dermal fibroblasts. After validating the accuracy, sensitivity and reproducibility of PHDs-seq data in molecular and cellular assays, a panel of 128 signalling-related compounds was screened for the ability to induce reprogramming of keloid fibroblasts (KF) into adipocytes. Notably, the potent ATP-competitive VEGFR/PDGFR inhibitor compound, ABT869, was found to promote the transition from fibroblasts to adipocytes. This study highlights the power and accuracy of the PHDs-seq platform for high-throughput drug screening in stem cell research, and supports its use in basic explorations of the molecular mechanisms underlying disease development.

Generation of Patient-Derived Podocytes from Skin Biopsies.

Podocytes are epithelial cells sitting on the urinary site of the glomerular filtration barrier that contribute to the selective filter function of the glomerulus. Mutations in podocyte-specific genes can cause focal segmental glomerulosclerosis (FSGS), and podocytes are also affected in many other primary and secondary nephropathies. Due to their differentiated nature, primary cell culture models are limited for podocytes.Therefore, commonly conditionally immortalized cells are used. However, these conditionally immortalized podocytes (ciPodocytes) have several limitations: the cells can dedifferentiate in culture, especially when they reach confluency, and several podocyte-specific markers are either only slightly or not expressed at all. This brings the use of ciPodocytes and their applicability for physiological, pathophysiological, and clinical reach into question. Here, we describe a protocol for the generation of human podocytes-including patient-specific podocytes-from a skin punch biopsy by episomal reprogramming of dermal fibroblasts into hiPSCs and subsequent differentiation into podocytes. These podocytes resemble in vivo podocytes much better in terms of morphological characteristics, like the development of foot processes and the expression of the podocyte-specific marker. Finally, yet importantly, these cells maintain patients' mutations, resulting in an improved ex vivo model to study podocyte diseases and potential therapeutic substances in an individualized approach.

Transcriptome-based chemical screens identify CDK8 as a common barrier in multiple cell reprogramming systems

Fibroblasts can be chemically induced to pluripotent stem cells (CiPSCs) through an extraembryonic endoderm (XEN)-like state or directly converted into other differentiated cell lineages. However, the mechanisms underlying chemically induced cell-fate reprogramming remain unclear. Here, a transcriptome-based screen of biologically active compounds uncovered that CDK8 inhibition was essential to enable chemically induced reprogramming from fibroblasts into XEN-like cells, then CiPSCs. RNA-sequencing analysis showed that CDK8 inhibition downregulated proinflammatory pathways that suppress chemical reprogramming and facilitated the induction of a multi-lineage priming state, indicating the establishment of plasticity in fibroblasts. CDK8 inhibition also resulted in a chromatin accessibility profile like that under initial chemical reprogramming. Moreover, CDK8 inhibition greatly promoted reprogramming of mouse fibroblasts into hepatocyte-like cells and induction of human fibroblasts into adipocytes. These collective findings thus highlight CDK8 as a general molecular barrier in multiple cell reprogramming processes, and as a common target for inducing plasticity and cell fate conversion.

MyoD-induced reprogramming of human fibroblasts and urinary stem cells in vitro: protocols and their applications.

The conversion of fibroblasts into myogenic cells is a powerful tool to both develop and test therapeutic strategies and to perform in-depth investigations of neuromuscular disorders, avoiding the need for muscle biopsies. We developed an easy, reproducible, and high-efficiency lentivirus-mediated transdifferentiation protocol, that can be used to convert healthy donor fibroblasts and a promising new cellular model, urinary stem cells (USCs), into myoblasts, that can be further differentiated into multinucleated myotubes in vitro. Transcriptome and proteome profiling of specific muscle markers (desmin, myosin, dystrophin) was performed to characterize both the myoblasts and myotubes derived from each cell type and to test the transdifferentiation-inducing capacity of MYOD1 in fibroblasts and USCs. Specifically, the Duchenne muscular dystrophy (DMD) transcripts and proteins, including both the full-length Dp427 and the short Dp71 isoform, were evaluated. The protocol was firstly developed in healthy donor fibroblasts and USCs and then used to convert DMD patients' fibroblasts, with the aim of testing the efficacy of an antisense drug in vitro. Technical issues, limitations, and problems are explained and discussed. We demonstrate that MyoD-induced-fibroblasts and USCs are a useful in vitro model of myogenic cells to investigate possible therapies for neuromuscular diseases.

Abstract IA19: Oncogenic KRAS and the regulation of the pancreatic cancer microenvironment.

Abstract Pancreatic ductal adenocarcinoma, the most common form of pancreatic cancer, is characterized by almost universal presence of oncogenic KRAS. A key characteristic of pancreatic cancer is the abundant accumulation of tumor microenvironment, rich in infiltrating immune cells and an extensive fibroblast population. Pancreatic cancer is preceded by precursor lesions known as Pancreatic Intraepithelial Neoplasia (PanIN); PanIN formation is accompanied by the formation of a pre-TME. Analysis of donor pancreas from healthy individual revealed that PanIN is common in human samples, and accompanied by pre-TME accumulation in human samples. We sought to determine whether oncogenic KRAS drives accumulation and maintenance of the pre-TME. For this purpose, we utilized the iKRAS mouse model of pancreatic cancer, which allows tissue-specific, inducible and reversible activation of KRASG12D, the most common mutant form in human pancreatic cancer. Activation of oncogenic KRAS in iKRAS mice leads to PanIN formation. We observed that fibroblast activation occurs upon KRAS activation and precedes the formation of overt lesions. Further, epithelial oncogenic KRAS is required to maintain fibroblast reprogramming in PanIN. To comprehensively understand changes in fibroblasts, we used single cell RNA sequencing, and observed that the fibroblast transcriptional program is extrinsically regulated by epithelial oncogenic KRAS. The reprogramming process can be modeled in vivo using conditioned media from pancreatic cancer cells expressing oncogenic KRAS, and is mediated by JAK/STAT3 signaling in fibroblasts. We then sought to determine whether the extrinsic effects of oncogenic KRAS induced reprogramming of fibroblasts at distal sites. We chose to study the lung, which is a common site of metastasis for pancreatic cancer. Our data show that lung fibroblasts are activated following expression of oncogenic KRAS in the pancreas; fibroblast activation is accompanied by phospho-Stat3 signaling, a readout of the JAK/Stat3 pathway, and precedes metastasis outgrowth in the pancreas. Thus, oncogenic KRAS extrinsically reprograms the local and systemic environments, possibly facilitating metastatic spread of pancreatic cancer. Citation Format: Marina Pasca di Magliano. Oncogenic KRAS and the regulation of the pancreatic cancer microenvironment. [abstract]. In: Proceedings of the AACR Special Conference: Targeting RAS; 2023 Mar 5-8; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Res 2023;21(5_Suppl):Abstract nr IA19.

Abstract LB039: Ovarian cancer cell-derived exosomal UCA1 reprograms glucose metabolism in stromal fibroblasts

Abstract Tumor progression is stringently regulated by the co-ordinated signaling between the tumor cells and the tumor microenvironment (TME) through diverse autocrine, paracrine and exocrine signaling mechanisms. Recent studies have shown that the exosomes that play a crucial role in the transfer of oncogenic macromolecules and oncometabolites to different cellular components of the TME can be targeted for therapy. Therefore, with the focus on identifying the exosomal long non-coding RNA (lncRNA) that can be therapeutically targeted, we investigated the profile of ovarian cancer cell derived lncRNAs and their functional role in ovarian cancer pathophysiology. Analysis of exosomes derived from a panel of high grade serous ovarian cancer cell lines indicated that UCA1 (Urothelial Cancer Associated 1) is the most abundantly packaged lncRNA in the exosomes. Similarly, exosomes from patient-derived ovarian cancer cells exhibited higher levels of UCA1. Ascites from ovarian cancer patients also indicated high levels of UCA1 in the ascites-derived exosomes. Results using PKH67-labelled ovarian cancer cell-derived exosomes and MRC5 fibroblast cell line indicated the exosomal transfer of UCA1 to the fibroblasts. Since paracrine signaling has been shown to induce metabolic reprogramming of peritumoral fibroblasts, we interrogated whether exosomal transfer of UCA1 could reprogram the glucose metabolism in the fibroblasts. Results from the Agilent Seahorse glycolytic stress assay indicate that the exosomal UCA1 promotes reprogramming of glucose metabolism in fibroblast cells while depleting of UCA1 in the exosomes failed to induce such metabolic reprogramming. Results from the analysis of the key glycolytic enzymes in the stromal fibroblasts, post-exosomal UCA1 uptake also corroborate this conclusion. Thus our results provide primary evidence that the exosomal-UCA1 induces pro-tumorigenic metabolic reprogramming in peri-tumoral fibroblasts. Together with the known oncogenic role of UCA1 in many different cancer cells, our findings indicate that targeting UCA1 could form a productive precision cancer strategy in ovarian cancer, targeting both the tumor cells and tumor stromal cells. This research was supported by the Department of Defense Ovarian Cancer Research Program Award W81XWH-18-1-0066, W81XWH-22-1-0415, the National Institute of General Medical Sciences grant P20 GM103639 and The National Cancer Institute of the National Institutes of Health grant P30 CA225520. Citation Format: Revathy Nadhan, Ji Hee Ha, Muralidharan Jayaraman, Srishti Kashyap, Danny N. Dhanasekaran. Ovarian cancer cell-derived exosomal UCA1 reprograms glucose metabolism in stromal fibroblasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB039.

Protocol Optimization for Direct Reprogramming of Primary Human Fibroblast into Induced Striatal Neurons.

The modeling of neuropathology on induced neurons obtained by cell reprogramming technologies can fill a gap between clinical trials and studies on model organisms for the development of treatment strategies for neurodegenerative diseases. Patient-specific models based on patients' cells play an important role in such studies. There are two ways to obtain induced neuronal cells. One is based on induced pluripotent stem cells. The other is based on direct reprogramming, which allows us to obtain mature neuronal cells from adult somatic cells, such as dermal fibroblasts. Moreover, the latter method makes it possible to better preserve the age-related aspects of neuropathology, which is valuable for diseases that occur with age. However, direct methods of reprogramming have a significant drawback associated with low cell viability during procedures. Furthermore, the number of reprogrammable neurons available for morphological and functional studies is limited by the initial number of somatic cells. In this article, we propose modifications of a previously developed direct reprogramming method, based on the combination of microRNA and transcription factors, which allowed us to obtain a population of functionally active induced striatal neurons (iSNs) with a high efficiency. We also overcame the problem of the presence of multinucleated neurons associated with the cellular division of starting fibroblasts. Synchronization cells in the G1 phase increased the homogeneity of the fibroblast population, increased the survival rate of induced neurons, and eliminated the presence of multinucleated cells at the end of the reprogramming procedure. We have demonstrated that iSNs are functionally active and able to form synaptic connections in co-cultures with mouse cortical neurons. The proposed modifications can also be used to obtain a population of other induced neuronal types, such as motor and dopaminergic ones, by selecting transcription factors that determine differentiation into a region-specific neuron.

Abstract 5843: miR-224 activates cancer-associated fibroblasts to promote cancer cell invasion in lung tumor microenvironment

Abstract Cancer-associated fibroblasts (CAFs) promote EMT (epithelial-mesenchymal transition), invasion, and metastasis of cancer cells in the tumor microenvironment. To identify microRNAs (miRNAs) associated with the reprogramming of normal lung fibroblasts (LFs) into CAFs, global miRNA expression was profiled in LFs and CAFs through Nanostring nCounter. miR-224 was one of the increased miRNAs in CAFs, and its expression was higher in tumors than in normal tissues in dbDEMC and TCGA_lung adenocarcinoma data. miR-224 levels were then checked by qRT-PCR in paraffine-embedded tumor samples from patients with lung adenocarcinoma. Kaplan-Meier survival analysis showed that high miR-224 expression was related to poor survival. These data show that lung cancer progression is promoted by miR-224. To discover the roles of increased miR-224 in CAFs, miR-224 was overexpressed by lentiviral infection in LFs. LF_miR-224 overexpression enhanced the expression of CAF activation markers including Fap, S100a4, and Vim. In spheroid invasion assay using co-culture of LFs and cancer cells, as an experimental model of the tumor microenvironment, LF_miR-224 promoted invasion of lung cancer cells compared with control LFs. In transwell migration assay, LF_miR-224 stimulated migration of lung cancer cells more than control LFs. Collectively, these results indicate that CAFs reprogrammed by miR-224 promote the migration and invasion of lung cancer cells. Citation Format: Seonyeong Oh, Inyoung Cheon, Young-Ho Ahn. miR-224 activates cancer-associated fibroblasts to promote cancer cell invasion in lung tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5843.

Reprogramming of cardiac cell fate as a therapeutic strategy for ischemic heart disease

Direct reprogramming of resident cardiac fibroblasts to induced cardiomyocytes is an attractive therapeutic strategy to restore function and remuscularize the injured heart. The cardiac transcription factors Gata4, Mef2c, and Tbx5 have been the mainstay of direct cardiac reprogramming strategies for the past decade. Yet, recent discoveries have identified alternative epigenetic factors capable of reprogramming human cells in the absence of these canonical factors. Further, single-cell genomics evaluating cellular maturation and epigenetics in the setting of injury and heart failure models following reprogramming have continued to inform the mechanistic underpinnings of this process and point toward future areas of discovery for the field. These discoveries and others covered in this review have provided complementary approaches that further enhance the effectiveness of reprogramming as a means of promoting cardiac regeneration following myocardial infarction and heart failure.

Direct reprogramming of human fibroblasts into insulin-producing cells using transcription factors

Direct lineage reprogramming of one somatic cell into another without transitioning through a progenitor stage has emerged as a strategy to generate clinically relevant cell types. One cell type of interest is the pancreatic insulin-producing β cell whose loss and/or dysfunction leads to diabetes. To date it has been possible to create β-like cells from related endodermal cell types by forcing the expression of developmental transcription factors, but not from more distant cell lineages like fibroblasts. In light of the therapeutic benefits of choosing an accessible cell type as the cell of origin, in this study we set out to analyze the feasibility of transforming human skin fibroblasts into β-like cells. We describe how the timed-introduction of five developmental transcription factors (Neurog3, Pdx1, MafA, Pax4, and Nkx2-2) promotes conversion of fibroblasts toward a β-cell fate. Reprogrammed cells exhibit β-cell features including β-cell gene expression and glucose-responsive intracellular calcium mobilization. Moreover, reprogrammed cells display glucose-induced insulin secretion in vitro and in vivo. This work provides proof-of-concept of the capacity to make insulin-producing cells from human fibroblasts via transcription factor-mediated direct reprogramming.

Pancreatic cancer and fibrosis: Targeting metabolic reprogramming and crosstalk of cancer-associated fibroblasts in the tumor microenvironment.

Pancreatic cancer is one of the most dangerous types of cancer today, notable for its low survival rate and fibrosis. Deciphering the cellular composition and intercellular interactions in the tumor microenvironment (TME) is a necessary prerequisite to combat pancreatic cancer with precision. Cancer-associated fibroblasts (CAFs), as major producers of extracellular matrix (ECM), play a key role in tumor progression. CAFs display significant heterogeneity and perform different roles in tumor progression. Tumor cells turn CAFs into their slaves by inducing their metabolic dysregulation, exacerbating fibrosis to acquire drug resistance and immune evasion. This article reviews the impact of metabolic reprogramming, effect of obesity and cellular crosstalk of CAFs and tumor cells on fibrosis and describes relevant therapies targeting the metabolic reprogramming.

Chemical reprogramming of human embryonic fibroblasts into neural progenitor cells in vitro

To establish a protocol for reprogramming human embryonic fibroblasts (HEFs) into chemically induced neural progenitor cells (ciNPCs). In the two-staged reprogramming of HEFs, the intermediate compact cell colonies were first chemically induced in KSR medium containing small-molecule compounds (VCR) for 15 days in normoxia, followed by the lineage-specific induction stage, in which the compact cell colonies were digested with 0.25% trypsin and the cells were cultured in low adhesion plates. After formation of a large number of free-floating neurospheres 2 days later, the ciNPCs were labeled with CM-DiI and transplanted into rat models of Parkinson's disease (PD)to observe the survival, migration and differentiation of the cells in PD brain. After induction with VCR for 10 days under normoxic condition, compact cell colonies occurred in HEF cultures (approximately 40 colonies in each well containing 1×105 HEFs), and most of the colonies expressed high levels of alkaline phosphatase. A large number of free-floating neurospheres formed 2 days after passage and were defined as P1 ciNPCs. These ciNPCs exhibited typical neurosphere-like structures and expressed NPC-specific markers (nestin, Sox2, and Pax6). Under neuronal or glial differentiation condition, the ciNPCs expressed the neuron-specific marker Tuj1 and the astrocyte-specific marker GFAP. These ciNPCs could differentiate into Tuj1+, GFAP+, TH+ and GABA+ cells 4 weeks after transplantation into the brain of PD rats. HEFs can be directly reprogrammed into ciNPCs using smallmolecule compounds without the need of introducing exogenous genes. This success may provide a solution to the shortage of donor materials for neuroscience research and treatment of neurodegenerative diseases.

Strategic Application of Epigenetic Regulators for Efficient Neuronal Reprogramming of Human Fibroblasts.

Cellular reprogramming in regenerative medicine holds great promise for treating patients with neurological disorders. In this regard, small molecule-mediated cellular conversion has attracted special attention because of its ease of reproducibility, applicability, and fewer safety concerns. However, currently available protocols for the direct conversion of somatic cells to neurons are limited in clinical application due of their complex nature, lengthy process, and low conversion efficiency. Here, we report a new protocol involving chemical-based direct conversion of human fibroblasts (HF) to matured neuron-like cells with a short duration and high conversion efficiency using temporal and strategic dual epigenetic regulation. In this protocol, epigenetic modulation by inhibition of histone deacetylase and bromodomain enabled to overcome "recalcitrant" nature of adult fibroblasts and shorten the duration of neuronal reprogramming. We further observed that an extended epigenetic regulation is necessary to maintain the induced neuronal program to generate a homogenous population of neuron-like cells. Therefore, our study provides a new protocol to produce neurons-like cells and highlights the need of proper epigenetic resetting to establish and maintain neuronal program in HF.

Rig1 receptor plays a critical role in cardiac reprogramming via YY1 signaling.

We discovered that innate immunity plays an important role in the reprogramming of fibroblasts into cardiomyocytes. In this report, we define the role of a novel retinoic acid-inducible gene 1 Yin Yang 1 (Rig1:YY1) pathway. We found that fibroblast to cardiomyocyte reprogramming efficacy was enhanced by specific Rig1 activators. To understand the mechanism of action, we performed various transcriptomic, nucleosome occupancy, and epigenomic approaches. Analysis of the datasets indicated that Rig1 agonists had no effect on reprogramming-induced changes in nucleosome occupancy or loss of inhibitory epigenetic motifs. Instead, Rig1 agonists were found to modulate cardiac reprogramming by promoting the binding of YY1 specifically to cardiac genes. To conclude, these results show that the Rig1:YY1 pathway plays a critical role in fibroblast to cardiomyocyte reprogramming.