A logic-incorporated gene regulatory network deciphers principles in cell fate decisions.

Organisms utilize gene regulatory networks (GRN) to make fate decisions, but the regulatory mechanisms of transcription factors (TF) in GRNs are exceedingly intricate. A longstanding question in this field is how these tangled interactions synergistically contribute to decision-making procedures. To comprehensively understand the role of regulatory logic in cell fate decisions, we constructed a logic-incorporated GRN model and examined its behavior under two distinct driving forces (noise-driven and signal-driven). Under the noise-driven mode, we distilled the relationship among fate bias, regulatory logic, and noise profile. Under the signal-driven mode, we bridged regulatory logic and progression-accuracy trade-off, and uncovered distinctive trajectories of reprogramming influenced by logic motifs. In differentiation, we characterized a special logic-dependent priming stage by the solution landscape. Finally, we applied our findings to decipher three biological instances: hematopoiesis, embryogenesis, and trans-differentiation. Orthogonal to the classical analysis of expression profile, we harnessed noise patterns to construct the GRN corresponding to fate transition. Our work presents a generalizable framework for top-down fate-decision studies and a practical approach to the taxonomy of cell fate decisions.

Repressing miR-23a promotes the transdifferentiation of pancreatic α cells to ß cells via negatively regulating the expression of SDF-1α.

Pancreatic ß-cell failure is a pathological feature in type 1 diabetes. One promising approach involves inducing transdifferentiation of related pancreatic cell types, specifically α cells that produce glucagon. The chemokine stromal cell-derived factor-1 alpha (SDF-1α) is implicated in pancreatic α-to-ß like cell transition. Here, the serum level of SDF-1α was lower in T1D with C-peptide loss, the miR-23a was negatively correlated with SDF-1α. We discovered that exosomal miR-23a, secreted from ß cells, functionally downregulates the expression of SDF-1α, leading to increased Pax4 expression and decreased Arx expression in vivo. Adenovirus-vectored miR-23a sponge and mimic were constructed to further explored the miR-23a on pancreatic α-to-ß like cell transition in vitro, which yielded results consistent with our cell-based assays. Suppression of miR-23a upregulated insulin level and downregulated glucagon level in STZ-induced diabetes mice models, effectively promoting α-to-ß like cell transition. Our findings highlight miR-23a as a new therapeutic target for regenerating pancreatic ß cells from α cells.

Temporal evolution reveals bifurcated lineages in aggressive neuroendocrine small cell prostate cancer trans-differentiation.

Trans-differentiation from an adenocarcinoma to a small cell neuroendocrine state is associated with therapy resistance in multiple cancer types. To gain insight into the underlying molecular events of the trans-differentiation, we perform a multi-omics time course analysis of a pan-small cell neuroendocrine cancer model (termed PARCB), a forward genetic transformation using human prostate basal cells and identify a shared developmental, arc-like, and entropy-high trajectory among all transformation model replicates. Further mapping with single cell resolution reveals two distinct lineages defined by mutually exclusive expression of ASCL1 or ASCL2. Temporal regulation by groups of transcription factors across developmental stages reveals that cellular reprogramming precedes the induction of neuronal programs. TFAP4 and ASCL1/2 feedback are identified as potential regulators of ASCL1 and ASCL2 expression. Our study provides temporal transcriptional patterns and uncovers pan-tissue parallels between prostate and lung cancers, as well as connections to normal neuroendocrine cell states.

FOXC2-AS1/FOXC2 axis mediates matrix stiffness-induced trans-differentiation of hepatic stellate cells into fibrosis-promoting myofibroblasts.

Matrix stiffness is a central modulator of hepatic stellate cells (HSCs) activation and hepatic fibrogenesis. However, the long non-coding RNAs (lncRNAs)-regulated transcriptional factors linking matrix stiffness to alterations in HSCs phenotype are not completely understood. In this study, we investigated the effects of matrix stiffness on HSCs activation and its potential mechanism. Through analysis the RNA-seq data with human primary HSCs cultured on 0.4 kPa and 25.6 kPa hydrogel, we identified that forkhead box protein C2 (FOXC2) and its antisense lncRNA FXOC2-AS1 as the new mechanosensing transcriptional regulators that coordinate HSCs responses to the matrix stiffness, moreover, FOXC2 and FOXC2-AS1 expression were also elevated in human fibrosis and cirrhosis tissues. The matrix stiffness was sufficient to activate HSCs into myofibroblasts, resulting in nuclear accumulation of FOXC2. Disrupting FOXC2 and FOXC2-AS1 level abrogated stiffness-induced activation of HSCs. Further mechanistic studies displayed that stiffness-upregulated lncRNA FOXC2-AS1 had no influence on transcription of FOXC2. FOXC2-AS1 exerted its biological function through maintaining the RNA stability of FOXC2, and protecting FOXC2 mRNA from degradation by RNA exosome complex. Additionally, rescue assays confirmed that reintroduction of FOXC2 in FOXC2-AS1-depleted HSCs reversed the repression of FOXC2-AS1 knockdown on stiffness-induced HSCs activation. In AAV6-treated mice fibrotic models, targeting FOXC2 in vivo lead to a reduced degree of liver fibrosis. In sum, our study uncovers a reciprocal crosstalk between matrix stiffness and FOXC2-AS1/FOXC2 axis leading to modulation of HSCs mechanoactivation and liver fibrosis, and present AAV6 shRNA as an effective strategy that targets FOXC2 leading to the resolution of liver fibrosis.

Single-cell epigenome analysis identifies molecular events controlling direct conversion of human fibroblasts to pancreatic ductal-like cells.

Cell fate can be reprogrammed by ectopic expression of lineage-specific transcription factors (TFs). However, the exact cell state transitions during transdifferentiation are still poorly understood. Here, we have generated pancreatic exocrine cells of ductal epithelial identity from human fibroblasts using a set of six TFs. We mapped the molecular determinants of lineage dynamics using a factor-indexing method based on single-nuclei multiome sequencing (FI-snMultiome-seq) that enables dissecting the role of each individual TF and pool of TFs in cell fate conversion. We show that transition from mesenchymal fibroblast identity to epithelial pancreatic exocrine fate involves two deterministic steps: an endodermal progenitor state defined by activation of HHEX with FOXA2 and SOX17 and a temporal GATA4 activation essential for the maintenance of pancreatic cell fate program. Collectively, our data suggest that transdifferentiation-although being considered a direct cell fate conversion method-occurs through transient progenitor states orchestrated by stepwise activation of distinct TFs.

Positive effect of miR-2392 on fibroblast to cardiomyocyte-like cell fate transition: An in silico and in vitro study.

INTRODUCTION: Somatic cell fate transition is now gained great importance in tissue regeneration. Currently, research is focused on heart tissue regeneration by reprogramming diverse cells into cardiomyocyte-like cells. Here, we examined the possible effect of miRNAs on the transdifferentiation of fibroblasts into cardiomyocyte-like cells. METHODS: First heart-specific miRNAs were identified by comparing the gene expression profiles of heart tissue to other body tissues using bioinformatic techniques. After identifying heart-specific miRNAs, their cellular and molecular functions were studied using the miRWalk and miRBase databases. Then the candidate miRNA was cloned into a lentiviral vector. Following, human dermal fibroblasts were cultured and treated with compounds forskolin, valproic acid, and CHIR99021. After 24 h, the lentivector harboring miRNA gene was transfected into the cells to initiate the transdifferentiation process. Finally, after a two-week treatment period, the efficiency of transdifferentiation was examined by inspecting the appearance of the cells and measuring the expression levels of cardiac genes and proteins using RT-qPCR and immunocytochemistry techniques. RESULTS: Nine miRNAs were identified with higher expression in the heart. The miR-2392 was nominated as the candidate miRNA due to its function and specific expression in the heart. This miRNA has a direct connection with genes involved in cell growth and differentiation; e.g., MAPK and Wnt signaling pathways. According to in vitro results cardiac genes and proteins demonstrated an increase in expression in the fibroblasts that simultaneously received the three chemicals and miR-2392. CONCLUSION: Considering the ability of miR-2392 to induce the expression of cardiac genes and proteins in fibroblast cells, it can induce fibroblasts to differentiate into cardiomyocyte-like cells. Therefore, miR-2392 could be further optimized for cardiomyocyte regeneration, tissue repair, and drug design studies.

Cell Transdifferentiation: A Challenging Strategy with Great Potential.

With the discovery and development of somatic cell nuclear transfer, cell fusion, and induced pluripotent stem cells, cell transdifferentiation research has presented unique advantages and stimulated a heated discussion worldwide. Cell transdifferentiation is a phenomenon by which a cell changes its lineage and acquires the phenotype of other cell types when exposed to certain conditions. Indeed, many adult stem cells and differentiated cells were reported to change their phenotype and transform into other lineages. This article reviews the differentiation of stem cells and classification of transdifferentiation, as well as the advantages, challenges, and prospects of cell transdifferentiation. This review discusses new research directions and the main challenges in the use of transdifferentiation in human cells and molecular replacement therapy. Overall, such knowledge is expected to provide a deep understanding of cell fate and regulation, which can change through differentiation, dedifferentiation, and transdifferentiation, with multiple applications.

Organoid models of fibrolamellar carcinoma mutations reveal hepatocyte transdifferentiation through cooperative BAP1 and PRKAR2A loss.

Fibrolamellar carcinoma (FLC) is a lethal primary liver cancer, affecting young patients in absence of chronic liver disease. Molecular understanding of FLC tumorigenesis is limited, partly due to the scarcity of experimental models. Here, we CRISPR-engineer human hepatocyte organoids to recreate different FLC backgrounds, including the predominant genetic alteration, the DNAJB1-PRKACA fusion, as well as a recently reported background of FLC-like tumors, encompassing inactivating mutations of BAP1 and PRKAR2A. Phenotypic characterizations and comparisons with primary FLC tumor samples revealed mutant organoid-tumor similarities. All FLC mutations caused hepatocyte dedifferentiation, yet only combined loss of BAP1 and PRKAR2A resulted in hepatocyte transdifferentiation into liver ductal/progenitor-like cells that could exclusively grow in a ductal cell environment. BAP1-mutant hepatocytes represent primed cells attempting to proliferate in this cAMP-stimulating environment, but require concomitant PRKAR2A loss to overcome cell cycle arrest. In all analyses, DNAJB1-PRKACAfus organoids presented with milder phenotypes, suggesting differences between FLC genetic backgrounds, or for example the need for additional mutations, interactions with niche cells, or a different cell-of-origin. These engineered human organoid models facilitate the study of FLC.

Potential involvement of miR-183/96/182 cluster-gene target interactions in transdifferentiation of human retinal pigment epithelial cells into retinal neurons.

miR-183/96/182 cluster plays a critical role in the developing retina by regulating many target genes involved in signaling pathways. This study aimed to survey the miR-183/96/182 cluster-target interactions that, potentially contribute to human retinal pigmented epithelial (hRPE) cell differentiation into photoreceptors. Target genes of the miR-183/96/182 cluster were obtained from miRNA-target databases and applied to construct miRNA-target networks. Gene ontology and KEGG pathway analysis was performed. miR-183/96/182 cluster sequence was cloned into an eGFP-intron splicing cassette in an AAV2 vector and overexpressed in hRPE cells. The expression level of target genes including HES1, PAX6, SOX2, CCNJ, and RORΒ was evaluated using qPCR. Our results showed that miR-183, miR-96, and miR-182 share 136 target genes that are involved in cell proliferation pathways such as PI3K/AKT and MAPK pathway. qPCR data indicated a 22-, 7-, and 4-fold overexpression of miR-183, miR-96, and miR-182, respectively, in infected hRPE cells. Consequently, the downregulation of several key targets such as PAX6, CCND2, CDK5R1, and CCNJ and upregulation of a few retina-specific neural markers such as Rhodopsin, red opsin, and CRX was detected. Our findings suggest that the miR-183/96/182 cluster may induce hRPE transdifferentiation by targeting key genes that involve in the cell cycle and proliferation pathways.

Phenotypic and genotypic infidelity in B-lineage neoplasms, including transdifferentiation following targeted therapy: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: Session 2 of the 2021 Society for Hematopathology and European Association for Haematopathology Workshop collected examples of lineage infidelity and transdifferentiation in B-lineage neoplasms, including after targeted therapy. METHODS: Twenty cases were submitted. Whole-exome sequencing and genome-wide RNA expression analysis were available on a limited subsample. RESULTS: A diagnosis of B-cell acute lymphoblastic leukemia (B-ALL) was rendered on at least 1 biopsy from 13 patients. There was 1 case of acute myeloid leukemia (AML); the remaining 6 cases were mature B-cell neoplasms. Targeted therapy was administered in 7 cases of B-ALL and 4 cases of mature B-cell neoplasms. Six cases of B-ALL underwent lineage switch to AML or mixed-phenotype acute leukemia at relapse, 5 of which had rearranged KMT2A. Changes in maturational state without lineage switch were observed in 2 cases. Examples of de novo aberrant T-cell antigen expression (n = 2) were seen among the mature B-cell lymphoma cohort, and their presence correlated with alterations in tumor cell gene expression patterns. CONCLUSIONS: This cohort of cases enabled us to illustrate, discuss, and review current concepts of lineage switch and aberrant antigen expression in a variety of B-cell neoplasms and draw attention to the role targeted therapies may have in predisposing neoplasms to transdifferentiation as well as other, less expected changes in maturational status.

Epigenome editing based on CRISPR/dCas9p300 facilitates transdifferentiation of human fibroblasts into Leydig-like cells.

Recently, Leydig cell (LCs) transplantation has a promising potential to treat male hypogonadism. However, the scarcity of seed cells is the actual barrier impeding the application of LCs transplantation. Utilizing the cutting-edge CRISPR/dCas9VP64 technology, human foreskin fibroblasts (HFFs) were transdifferentiated into Leydig-like cells（iLCs） in previous study, but the efficiency of transdifferentiation is not very satisfactory. Therefore, this study was conducted to further optimize the CRISPR/dCas9 system for obtaining sufficient iLCs. First, the stable CYP11A1-Promoter-GFP-HFFs cell line was established by infecting HFFs with CYP11A1-Promoter-GFP lentiviral vectors, and then co-infected with dCas9p300 and the combination of sgRNAs targeted to NR5A1, GATA4 and DMRT1. Next, this study adopted quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot, and immunofluorescence to determine the efficiency of transdifferentiation, the generation of testosterone, the expression levels of steroidogenic biomarkers. Moreover, we utilized chromatin immuno-precipitation (ChIP) followed by quantitative polymerase chain reaction (ChIP-qPCR) to measure the levels of acetylation of targeted H3K27. The results revealed that advanced dCas9p300 facilitated generation of iLCs. Moreover, the dCas9p300-mediated iLCs significantly expressed the steroidogenic biomarkers and produced more testosterone with or without LH treatment than the dCas9VP64-mediated. Additionally, preferred enrichment in H3K27ac at the promoters was detected only with dCas9p300 treatment. The data provided here imply that the improved version of dCas9 can aid in the harvesting of iLCs, and will provide sufficient seed cells for cell transplantation treatment of androgen deficiency in the future.

Oxidative stress-triggered Wnt signaling perturbation characterizes the tipping point of lung adeno-to-squamous transdifferentiation.

Lkb1 deficiency confers the Kras-mutant lung cancer with strong plasticity and the potential for adeno-to-squamous transdifferentiation (AST). However, it remains largely unknown how Lkb1 deficiency dynamically regulates AST. Using the classical AST mouse model (Kras LSL-G12D/+;Lkb1flox/flox, KL), we here comprehensively analyze the temporal transcriptomic dynamics of lung tumors at different stages by dynamic network biomarker (DNB) and identify the tipping point at which the Wnt signaling is abruptly suppressed by the excessive accumulation of reactive oxygen species (ROS) through its downstream effector FOXO3A. Bidirectional genetic perturbation of the Wnt pathway using two different Ctnnb1 conditional knockout mouse strains confirms its essential role in the negative regulation of AST. Importantly, pharmacological activation of the Wnt pathway before but not after the tipping point inhibits squamous transdifferentiation, highlighting the irreversibility of AST after crossing the tipping point. Through comparative transcriptomic analyses of mouse and human tumors, we find that the lineage-specific transcription factors (TFs) of adenocarcinoma and squamous cell carcinoma form a "Yin-Yang" counteracting network. Interestingly, inactivation of the Wnt pathway preferentially suppresses the adenomatous lineage TF network and thus disrupts the "Yin-Yang" homeostasis to lean towards the squamous lineage, whereas ectopic expression of NKX2-1, an adenomatous lineage TF, significantly dampens such phenotypic transition accelerated by the Wnt pathway inactivation. The negative correlation between the Wnt pathway and AST is further observed in a large cohort of human lung adenosquamous carcinoma. Collectively, our study identifies the tipping point of AST and highlights an essential role of the ROS-Wnt axis in dynamically orchestrating the homeostasis between adeno- and squamous-specific TF networks at the AST tipping point.

Trans-differentiation of trophoblast stem cells: implications in placental biology.

Trophoblast invasion is a hallmark of hemochorial placentation. Invasive trophoblast cells replace the endothelial cells of uterine spiral arteries. The mechanism by which the invasive trophoblast cells acquire this phenotype is unknown. Here, we demonstrate that, during differentiation, a small population of trophoblast stem (TS) cells trans-differentiate into a hybrid cell type expressing markers of both trophoblast (TC) and endothelial (EC) cells. In addition, a compendium of EC-specific genes was found to be associated with TS cell differentiation. Using functional annotation, these genes were categorized into angiogenesis, cell adhesion molecules, and apoptosis-related genes. HES1 repressed transcription of EC genes in TS cells. Interestingly, differentiated TCs secrete TRAIL, but its receptor DR4 is expressed only in ECs and not in TCs. TRAIL induced apoptosis in EC but not in TC. Co-culture of ECs with TC induced apoptosis in ECs via extrinsic apoptotic pathway. These results highlight that (a) TS cells possess the potential to trans-differentiate into "trophendothelial" phenotype, regulated by HES1 and (b) trophoblast differentiation-induced TRAIL secretion directs preferential demise of ECs located in their vicinity.

Temporal Analysis Reveals the Transient Differential Expression of Transcription Factors That Underlie the Trans-Differentiation of Human Monocytes to Macrophages.

The activation of monocytes and their trans-differentiation into macrophages are critical processes of the immune response. Prior work has characterized the differences in the expression between monocytes and macrophages, but the transitional process between these cells is poorly detailed. Here, we analyzed the temporal changes of the transcriptome during trans-differentiation of primary human monocytes into M0 macrophages. We find changes with many transcription factors throughout the process, the vast majority of which exhibit a maximally different expression at the intermediate stages. A few factors, including AP-1, were previously known to play a role in immunological transitions, but most were not. Thus, these findings indicate that this trans-differentiation requires the dynamic expression of many transcription factors not previously discussed in immunology, and provide a foundation for the delineation of the molecular mechanisms associated with healthy or pathological responses that involve this transition.

Loss of SUMO-specific protease 2 causes isolated glucocorticoid deficiency by blocking adrenal cortex zonal transdifferentiation in mice.

SUMOylation is a dynamic posttranslational modification, that provides fine-tuning of protein function involved in the cellular response to stress, differentiation, and tissue development. In the adrenal cortex, an emblematic endocrine organ that mediates adaptation to physiological demands, the SUMOylation gradient is inversely correlated with the gradient of cellular differentiation raising important questions about its role in functional zonation and the response to stress. Considering that SUMO-specific protease 2 (SENP2), a deSUMOylating enzyme, is upregulated by Adrenocorticotropic Hormone (ACTH)/cAMP-dependent Protein Kinase (PKA) signalling within the zona fasciculata, we generated mice with adrenal-specific Senp2 loss to address these questions. Disruption of SENP2 activity in steroidogenic cells leads to specific hypoplasia of the zona fasciculata, a blunted reponse to ACTH and isolated glucocorticoid deficiency. Mechanistically, overSUMOylation resulting from SENP2 loss shifts the balance between ACTH/PKA and WNT/ß-catenin signalling leading to repression of PKA activity and ectopic activation of ß-catenin. At the cellular level, this blocks transdifferentiation of ß-catenin-positive zona glomerulosa cells into fasciculata cells and sensitises them to premature apoptosis. Our findings indicate that the SUMO pathway is critical for adrenal homeostasis and stress responsiveness.

Genomics of sexual cell fate transdifferentiation in the mouse gonad.

Sex determination in mammals hinges on a cell fate decision in the fetal bipotential gonad between formation of male Sertoli cells or female granulosa cells. While this decision normally is permanent, loss of key cell fate regulators such as the transcription factors Dmrt1 and Foxl2 can cause postnatal transdifferentiation from Sertoli to granulosa-like (Dmrt1) or vice versa (Foxl2). Here, we examine the mechanism of male-to-female transdifferentiation in mice carrying either a null mutation of Dmrt1 or a point mutation, R111G, that alters the DNA-binding motif and causes human XY gonadal dysgenesis and sex reversal. We first define genes misexpressed during transdifferentiation and then show that female transcriptional regulators driving transdifferentiation in the mutant XY gonad (ESR2, LRH1, FOXL2) bind chromatin sites related to those normally bound in the XX ovary. We next define gene expression changes and abnormal chromatin compartments at the onset of transdifferentiation that may help destabilize cell fate and initiate the transdifferentiation process. We model the R111G mutation in mice and show that it causes dominant gonadal dysgenesis, analogous to its human phenotype but less severe. We show that R111G partially feminizes the testicular transcriptome and causes dominant disruption of DMRT1 binding specificity in vivo. These data help illuminate how transdifferentiation occurs when sexual cell fate maintenance is disrupted and identify chromatin sites and transcripts that may play key roles in the transdifferentiation process.

The role of DNA demethylation in liver to pancreas transdifferentiation.

BACKGROUND: Insulin producing cells generated by liver cell transdifferentiation, could serve as an attractive source for regenerative medicine. The present study assesses the relationship between DNA methylation pTFs induced liver to pancreas transdifferentiation. RESULTS: The transdifferentiation process is associated with DNA demethylation, mainly at gene regulatory sites, and with increased expression of these genes. Active inhibition of DNA methylation promotes the pancreatic transcription factor-induced transdifferentiation process, supporting a causal role for DNA demethylation in this process. CONCLUSIONS: Transdifferentiation is associated with global DNA hypomethylation, and with increased expression of specific demethylated genes. A combination of epigenetic modulators may be used to increase chromatin accessibility of the pancreatic transcription factors, thus promoting the efficiency of the developmental process.

Characterization and perturbation of CTCF-mediated chromatin interactions for enhancing myogenic transdifferentiation.

Expression of key transcription factors can induce transdifferentiation in somatic cells; however, this conversion is usually incomplete due to undefined intrinsic barriers. Here, we employ MyoD-induced transdifferentiation of fibroblasts as a model to illustrate the chromatin structures that impede the cell-fate transition. Focusing on the three-dimensional (3D) chromatin interactions, we show that MyoD directly establishes chromatin loops to activate myogenic transcriptional program. Similarly, dynamic changes of CTCF-mediated chromatin interactions are favorable for fibroblast-to-myoblast conversion. However, a substantial portion of CTCF-mediated chromatin interactions remain stable, and the associated genes are steady in expression and enriched for fibroblast function that may restrict cell-identity transformation. Temporal CTCF depletion can interrupt the resistant chromatin loops to enhance myogenic transdifferentiation in mice, pig, and chicken fibroblasts. Therefore, during induced transdifferentiation, the transcription factor can directly reorganize the 3D chromatin interactions, and perturbation of CTCF-mediated genome topology may resolve the limitations of cell fate transitions.

From IL-17 to IFN-γ in inflammatory skin disorders: Is transdifferentiation a potential treatment target?

The targeted inhibition of effector cytokines such as interleukin 17 (IL-17) in psoriasis and IL-13 in atopic dermatitis offers impressive efficacy with a favorable side effect profile. In contrast, the downregulation of interferon gamma (IFN-γ) in T helper (Th) 1-dominant skin disorders may lead to more adverse events, given the crucial role of IFN-γ in antiviral and antitumoral immunity. Modulating Th17 and Th2 cell differentiation is performed by blocking IL-23 and IL-4, respectively, whereas anti-IL-12 antibodies are only moderately effective in downregulating Th1 lymphocyte differentiation. Therefore, a targeted approach of IFN-γ-driven disorders remains challenging. Recent literature suggests that certain pathogenic Th17 cell subsets with Th1 characteristics, such as CD4+CD161+CCR6+CXCR3+IL-17+IFN-y+ (Th17.1) and CD4+CD161+CCR6+CXCR3+IL-17-IFN-y+ (exTh17), are important contributors in Th1-mediated autoimmunity. Differentiation to a Th17.1 or exTh17 profile results in the upregulation of IFN-y. Remarkably, these pathogenic Th17 cell subsets are resistant to glucocorticoid therapy and the dampening effect of regulatory T cells (Treg). The identification of Th17.1/exTh17 cells in auto-immune disorders may explain the frequent treatment failure of conventional immunosuppressants. In this review, we summarize the current evidence regarding the cellular plasticity of Th17 cells in inflammatory skin disorders. A deeper understanding of this phenomenon may lead to better insights into the pathogenesis of various skin diseases and the discovery of a potential new treatment target.

Kruppel Like Factor 5 Enhances High Glucose-Induced Renal Tubular Epithelial Cell Transdifferentiation in Diabetic Nephropathy.

Background - Diabetic nephropathy (DN) is a principal reason for kidney disease worldwide. High glucose (HG) is a major factor for DN. Kruppel like factor 5 (KLF5) participates in DN development. In the present study, we aim to elaborate the role of KLF5 in HG-induced renal tubular epithelial cell (RTEC) transdifferentiation in DN. Methods - RTECs (HK-2 cells) were treated with HG and were transfected with si-KLF5 or oe-HMGB1. Afterwards, expression of KLF5 and HMGB1 was detected, HK cell viability was determined, and levels of alpha-smooth muscle actin (α-SMA), E-cadherin, vimentin, and transforming growth factor beta 1 (TGF-ß1) were assessed. Additionally, the binding relation between KLF5 and HMGB1 was analyzed. Results - In HK-2 cells with HG treatment, expression of KLF5 and HMGB1 was upregulated; levels of α-SMA, vimentin, and TGF-ß1 were increased; and E-cadherin level was decreased. Moreover, KLF5 silencing resulted in down-regulated levels of α-SMA, vimentin, and TGF-ß1 but upregulated level of E-cadherin. On the other hand, KLF5 could bind to the HMGB1 promoter and activate HMGB1 transcription. HMGB1 overexpression partially counteracted the inhibitive effect of KLF5 silencing on HG-induced HK-2 transdifferentiation. Conclusion - HG induced overexpressed KLF5 in RTECs, and as a transcription factor, KLF5 could bind to the HMGB1 promoter, thereby promoting HMGB1 transcription and RTEC transdifferentiation.