Long noncoding RNA: a new contributor and potential therapeutic target in fibrosis

The role of long noncoding RNA MEG3 in fibrosis diseases

Fibrosis is a prevalent pathological condition observed in various organs and tissues. It primarily arises from the excessive and abnormal accumulation of the extracellular matrix, resulting in the structural and functional impairment of tissues and organs, which can culminate in death. Many forms of fibrosis, including liver, cardiac, pulmonary, and renal fibrosis, are considered irreversible. Maternally expressed gene 3 (MEG3) is an imprinted RNA gene. Historically, the downregulation of MEG3 has been linked to tumor pathogenesis. However, recent studies indicate an emerging association of MEG3 with fibrotic diseases. In this review, we delve into the current understanding of MEG3's role in fibrosis, aiming to shed light on the molecular mechanisms of fibrosis and the potential of MEG3 as a novel therapeutic target.

LncRNA GAS5 Attenuates Cardiac Electrical Remodeling Induced by Rapid Pacing via the miR-27a-3p/HOXa10 Pathway

Previous studies indicated long non-coding RNAs (lncRNAs) participated in the pathogenesis of atrial fibrillation (AF). However, little is known about the role of lncRNAs in AF-induced electrical remodeling. This study aimed to investigate the regulatory effect of lncRNA GAS5 (GAS5) on the electrical remodeling of neonatal rat cardiomyocytes (NRCMs) induced by rapid pacing (RP). RNA microarray analysis yielded reduced GAS5 level in NRCMs after RP. RT-qPCR, western blot, and immunofluorescence yielded downregulated levels of Nav1.5, Kv4.2, and Cav1.2 after RP, and whole-cell patch-clamp yielded decreased sodium, potassium, and calcium current. Overexpression of GAS5 attenuated electrical remodeling. Bioinformatics tool prediction analysis and dual luciferase reporter assay confirmed a direct negative regulatory effect for miR-27a-3p on lncRNA-GAS5 and HOXa10. Further analysis demonstrated that either miR-27a-3p overexpression or the knockdown of HOXa10 further downregulated Nav1.5, Kv4.2, and Cav1.2 expression. GAS5 overexpression antagonized such effects in Nav1.5 and Kv4.2 but not in Cav1.2. These results indicate that, in RP-treated NRCMs, GAS5 could restore Nav1.5 and Kv4.2 expression via the miR-27a-3p/HOXa10 pathway. However, the mechanism of GAS5 restoring Cav1.2 level remains unclear. Our study suggested that GAS5 regulated cardiac ion channels via the GAS5/miR-27a-3p/HOXa10 pathway and might be a potential therapeutic target for AF.

Genetic Deletion of the LINC00520 Homolog in Mouse Aggravates Angiotensin II-Induced Hypertension

(1) Background: Hypertension is a complex, multifactorial disease that is caused by genetic and environmental factors. Apart from genetic predisposition, the mechanisms involved in this disease have yet to be fully understood. We previously reported that LEENE (lncRNA enhancing endothelial nitric oxide expression, transcribed from LINC00520 in the human genome) regulates endothelial cell (EC) function by promoting the expression of endothelial nitric oxide synthase (eNOS) and vascular growth factor receptor 2 (VEGFR2). Mice with genetic deletion of the LEENE/LINC00520 homologous region exhibited impaired angiogenesis and tissue regeneration in a diabetic hindlimb ischemia model. However, the role of LEENE in blood pressure regulation is unknown. (2) Methods: We subjected mice with genetic ablation of leene and wild-type littermates to Angiotensin II (AngII) and monitored their blood pressure and examined their hearts and kidneys. We used RNA-sequencing to identify potential leene-regulated molecular pathways in ECs that contributed to the observed phenotype. We further performed in vitro experiments with murine and human ECs and ex vivo experiments with murine aortic rings to validate the select mechanism. (3) Results: We identified an exacerbated hypertensive phenotype of leene-KO mice in the AngII model, evidenced by higher systolic and diastolic blood pressure. At the organ level, we observed aggravated hypertrophy and fibrosis in the heart and kidney. Moreover, the overexpression of human LEENE RNA, in part, restored the signaling pathways impaired by leene deletion in murine ECs. Additionally, Axitinib, a tyrosine kinase inhibitor that selectively inhibits VEGFR suppresses LEENE in human ECs. (4) Conclusions: Our study suggests LEENE as a potential regulator in blood pressure control, possibly through its function in ECs.

LncRNA DACH1 protects against pulmonary fibrosis by binding to SRSF1 to suppress CTNNB1 accumulation

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with unknown etiology and limited therapeutic options. Activation of fibroblasts is a prominent feature of pulmonary fibrosis. Here we report that lncRNA DACH1 (dachshund homolog 1) is downregulated in the lungs of IPF patients and in an experimental mouse model of lung fibrosis. LncDACH1 knockout mice develop spontaneous pulmonary fibrosis, whereas overexpression of LncDACH1 attenuated TGF-β1-induced aberrant activation, collagen deposition and differentiation of mouse lung fibroblasts. Similarly, forced expression of LncDACH1 not only prevented bleomycin (BLM)-induced lung fibrosis, but also reversed established lung fibrosis in a BLM model. Mechanistically, LncDACH1 binding to the serine/arginine-rich splicing factor 1 (SRSF1) protein decreases its activity and inhibits the accumulation of Ctnnb1. Enhanced expression of SRSF1 blocked the anti-fibrotic effect of LncDACH1 in lung fibroblasts. Furthermore, loss of LncDACH1 promoted proliferation, differentiation, and extracellular matrix (ECM) deposition in mouse lung fibroblasts, whereas such effects were abolished by silencing of Ctnnb1. In addition, a conserved fragment of LncDACH1 alleviated hyperproliferation, ECM deposition and differentiation of MRC-5 cells driven by TGF-β1. Collectively, LncDACH1 inhibits lung fibrosis by interacting with SRSF1 to suppress CTNNB1 accumulation, suggesting that LncDACH1 might be a potential therapeutic target for pulmonary fibrosis.

The Roles and Mechanisms of lncRNAs in Liver Fibrosis

Long non-coding RNAs (lncRNAs) can potentially regulate all aspects of cellular activity including differentiation and development, metabolism, proliferation, apoptosis, and activation, and benefited from advances in transcriptomic and genomic research techniques and database management technologies, its functions and mechanisms in physiological and pathological states have been widely reported. Liver fibrosis is typically characterized by a reversible wound healing response, often accompanied by an excessive accumulation of extracellular matrix. In recent years, a range of lncRNAs have been investigated and found to be involved in several cellular-level regulatory processes as competing endogenous RNAs (ceRNAs) that play an important role in the development of liver fibrosis. A variety of lncRNAs have also been shown to contribute to the altered cell cycle, proliferation profile associated with the accelerated development of liver fibrosis. This review aims to discuss the functions and mechanisms of lncRNAs in the development and regression of liver fibrosis, to explore the major lncRNAs involved in the signaling pathways regulating liver fibrosis, to elucidate the mechanisms mediated by lncRNA dysregulation and to provide new diagnostic and therapeutic strategies for liver fibrosis.

Elevation of LncRNA ENST00000453774.1 Prevents Renal Fibrosis by Upregulating FBN1, IGF1R, and KLF7

INTRODUCTION

Transforming growth factor-β (TGF-β), a common outcome of various progressive chronic kidney diseases, can regulate and induce fibrosis.

OBJECTIVE

The study aimed to identify downstream targets of lncRNA ENST00000453774.1 (lnc453774.1) and outline their functions on the development of renal fibrosis.

METHODS

HK-2 cells were induced with 5 ng/mL TGF-β1 for 24 h to construct a renal fibrosis cell model. Differentially expressed genes (DEGs) targeted by lnc453774.1 in TGF-β1-induced renal fibrosis were identified using RNA sequencing. The dataset GSE23338 was employed to identify DEGs in 48-h TGF-β1-stimulated human kidney epithelial cells, and these DEGs were intersected with genes in the key module using weighted gene co-expression network analysis to generate key genes associated with renal fibrosis. MicroRNAs (miRs) that had targeting relationship with keys genes and lnc453774.1 were predicted by using Miranda software, and important genes were intersected with key genes that had targeting relationship with these miRs. Key target genes by lnc453774.1 were identified in a protein-protein interaction network among lnc453774.1, important genes, and reported genes related to autophagy, oxidative stress, and cell adhesion.

RESULTS

Key genes in the key module (turquoise) were intersected with DEGs in the dataset GSE23338 and yielded 20 key genes regulated by lnc453774.1 involved in renal fibrosis. Fourteen miRs had targeting relationship with lnc453774.1 and key genes, and 8 important genes targeted by these 14 miRs were identified. Fibrillin-1 (FBN1), insulin-like growth factor 1 receptor (IGF1R), and Kruppel-like factor 7 (KLF7) were identified to be involved in autophagy, oxidative stress, and cell adhesion and were elevated in the lnc453774.1-overexpressing TGF-β1-induced cells.

CONCLUSION

These results show FBN1, IGF1R, and KLF7 serve as downstream targets of lnc453774.1, and that lnc453774.1 may protect against renal fibrosis through competing endogenous miRs which target FBN1, IGF1R, and KLF7 mRNAs.

Transforming Growth Factor-β and Long Non-coding RNA in Renal Inflammation and Fibrosis

Renal fibrosis is one of the most characterized pathological features in chronic kidney disease (CKD). Progressive fibrosis eventually leads to renal failure, leaving dialysis or allograft transplantation the only clinical option for CKD patients. Transforming growth factor-β (TGF-β) is the key mediator in renal fibrosis and is an essential regulator for renal inflammation. Therefore, the general blockade of the pro-fibrotic TGF-β may reduce fibrosis but may risk promoting renal inflammation and other side effects due to the diverse role of TGF-β in kidney diseases. Long non-coding RNAs (lncRNAs) are RNA transcripts with more than 200 nucleotides and have been regarded as promising therapeutic targets for many diseases. This review focuses on the importance of TGF-β and lncRNAs in renal inflammation, fibrogenesis, and the potential applications of TGF-β and lncRNAs as the therapeutic targets and biomarkers in renal fibrosis and CKD are highlighted.

Long Non-Coding RNA 554 Promotes Cardiac Fibrosis via TGF-β1 Pathway in Mice Following Myocardial Infarction

Rationale: Cardiac fibrosis is observed in nearly every form of myocardial disease. Long non-coding RNAs (lncRNAs) have been shown to play an important role in cardiac fibrosis, but the detailed molecular mechanism remains unknown.

Object: We aimed at characterizing lncRNA 554 expression in murine cardiac fibroblasts (CFs) after myocardial infarction (MI) to identify CF-enriched lncRNA and investigate its function and contribution to cardiac fibrosis and function.

Methods and Results: In this study, we identified lncRNA NONMMUT022554 (lncRNA 554) as a regulator of MI-induced cardiac fibrosis. We found that lncRNA 554 was significantly up-regulated in the mouse hearts following MI. Further study showed that lncRNA 554 was predominantly expressed in cardiac fibroblasts, indicating a potential role of lncRNA 554 in cardiac fibrosis. In vitro knockdown of lncRNA 554 by siRNA suppressed fibroblasts migration and expression of extracellular matrix (ECM); while overexpression of lncRNA 554 promoted expression of ECM genes. Consistently, lentivirus mediated in vivo knockdown of lncRNA 554 could inhibit cardiac fibrosis and improve cardiac function in mouse model of MI. More importantly, TGF-β1 inhibitor (TEW-7197) could reverse the pro-fibrotic function of lncRNA 554 in CFs. This suggests that the effects of lncRNA 554 on cardiac fibrosis is TGF-β1 dependent.

Conclusion: Collectively, our study illustrated the role of lncRNA 554 in cardiac fibrosis, suggested that lncRNA 554 might be a novel target for cardiac fibrosis.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

Targeting chromatin dysregulation in organ fibrosis

Fibrosis leads to destruction of organ architecture accompanied by chronic inflammation and loss of function. Fibrosis affects nearly every organ in the body and accounts for ∼45% of total deaths worldwide. Over the past decade, tremendous progress has been made in understanding the basic mechanisms leading to organ fibrosis. However, we are limited with therapeutic options and there is a significant need to develop highly effective anti-fibrotic therapies. Recent advances in sequencing technologies have advanced the burgeoning field of epigenetics towards molecular understanding at a higher resolution. Here we provide a comprehensive review of the recent advances in chromatin regulatory processes, specifically DNA methylation, post-translational modification of histones, and chromatin remodeling complexes in kidney, liver and lung fibrosis. Although this research field is young, we discuss new strategies for potential therapeutic interventions for treating organ fibrosis.

Peritoneal fibrosis and epigenetic modulation

Peritoneal dialysis (PD) is an effective treatment for patients with end-stage renal disease. However, peritoneal fibrosis (PF) is a common complication that ultimately leads to ultrafiltration failure and discontinuation of PD after long-term PD therapy. There is currently no effective therapy to prevent or delay this pathologic process. Recent studies have reported epigenetic modifications involved in PF, and accumulating evidence suggests that epigenetic therapies may have the potential to prevent and treat PF clinically. The major epigenetic modifications in PF include DNA methylation, histone modification, and noncoding RNAs. The mechanisms of epigenetic regulation in PF are complex, predominantly involving modification of signaling molecules, transcriptional factors, and genes. This review will describe the mechanisms of epigenetic modulation in PF and discuss the possibility of targeting them to prevent and treat this complication.

The TGF-β1 Induces the Endothelial-to-Mesenchymal Transition via the UCA1/miR-455/ZEB1 Regulatory Axis in Human Umbilical Vein Endothelial Cells

Transforming growth factor-beta 1 (TGF-β1) plays important roles in the endothelial-to-mesenchymal transition (EndMT). Recently, long noncoding RNAs (lncRNAs) have been identified to be involved in the physiological and pathological processes of human diseases. However, the role of endothelial lncRNAs in the TGF-β1-mediated control of angiogenesis and its underlying mechanism remains largely unclear. In this study, we first demonstrated that TGF-β1 induced EndMT; promoted cell viability, proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs). Second, our study displayed that TGF-β1 upregulated the lncRNA UCA1 expression in HUVECs, knocked down UCA1 with small interfering RNAs, and inhibited the function of TGF-β1 in HUVECs. Third, our study showed that UCA1 was located in the cytoplasm and absorbed miR-455 in TGF-β1-treated HUVECs. Further, the miR-455 inhibitor restored the role of the inhibited UCA1 in HUVECs treated with TGF-β1. Fourth, our study revealed that miR-455 inhibited ZEB1 expression, and overexpression of ZEB1 restored the role of miR-455 in HUVECs treated with TGF-β1. Finally, our study revealed that UCA1 exerted its role via regulating the UCA1/miR-455/ZEB1 regulatory axis in HUVECs treated with TGF-β1. Collectively, our study identified the role of the UCA1/miR-455/ZEB1 pathway in HUVECs treated with TGF-β1 and indicated the potential therapeutic role of this regulatory axis in angiogenesis.

The mechanisms of lncRNA GAS5 in cardiovascular cells and its potential as novel therapeutic target

Long noncoding RNAs (lncRNAs) are a large class of non (protein)-coding RNAs, which are longer beyond 200 nucleotides. LncRNA GAS5 is widely considered as a tumour suppressor in cell proliferation, apoptosis, cell migration and invasion of tumour cells. Recently, a growing body of evidences indicated that GAS5 was also widely involved in the pathologic process of cardiovascular cells, including regulation of apoptosis and inflammatory injury of cardiomyocytes; proliferation, apoptosis, autophagy and angiogenesis of endothelial cells; and proliferation, migration, apoptosis and differentiation of VSMCs. In this regard, we summarised current studies of GAS5 in cardiovascular cells, which shed light on not only our understanding of the mechanisms of GAS5 in cardiovascular cells but also understanding of the potential of GAS5 as novel therapeutic target.

Long noncoding RNAs as novel players in the pathogenesis of hypertension

Long noncoding RNAs (lncRNAs) are non-(protein)-coding RNAs longer than ~200 nucleotides and have been reported to be involved in multiple human diseases by regulating gene expression. A growing body of evidence has demonstrated that lncRNAs are also widely implicated in mechanisms of hypertension, including regulation of the proliferation, migration, and apoptosis of VSMCs; the production of iNOS and NO; and the angiogenic function of endothelial cells. Several lncRNAs were also differentially expressed in the renal and cardiac tissues of hypertensive rats and even in placental samples from preeclampsia patients. In particular, several circulating lncRNAs have been identified as novel biomarkers of hypertension. In this review, we summarize the current studies of lncRNAs in the pathogenesis of hypertension in order to aid in better understanding the molecular mechanism of hypertension and provide a basis to explore new therapeutic targets.

Differential expression of lncRNAs during silicosis and the role of LOC103691771 in myofibroblast differentiation induced by TGF-β1

OBJECTIVE

The role and molecular mechanism of long non-coding RNA (lncRNA)-related pathways in silicosis have not been elucidated clearly. The aims of this study were to evaluate the expression of lncRNAs during silica-induced pulmonary fibrosis and verify the function and molecular mechanism of LOC103691771 in myofibroblast differentiation induced by transforming growth factor-β1 (TGF-β1).

METHODS

RNA-sequencing was performed to assess differential expression of lncRNAs in control and silicotic rat lungs. Differential expression of lncRNAs was analyzed by Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes to identify their biological roles. LOC103691771, LOC102549714, LOC102550137, LOC103693125, and LOC103692016 were selected to verify their expression by real-time PCR of silicotic rat lung tissue and lung fibroblasts stimulated by TGF-β1. Specific small interfering RNA and an LOC103691771 overexpression plasmid were used to analyze the molecular mechanism in myofibroblast differentiation induced by TGF-β1.

RESULT

A total of 306 lncRNAs were expressed differentially in silicotic rat lungs, including 224 upregulated and 82 downregulated lncRNAs. The expression of LOC103691771, LOC102549714 and LOC102550137 was upregulated, while the expression of LOC103693125 and LOC103692016 was downregulated in silicotic rat lungs and TGF-β1-induced fibroblast, which was consistent with the results of RNA-sequencing. Furthermore, LOC103691771 gene silencing attenuated myofibroblast differentiation, whereas LOC103691771 overexpression promoted myofibroblast differentiation via regulation of the TGF-β1-Smad2/3 signaling pathway.

CONCLUSION

Our findings revealed that differential expression of lncRNAs was related to the development of silicosis, and LOC103691771 played a major role in myofibroblast differentiation induced by TGF-β1, which may serve as a potential therapeutic target for silicosis.

Diagnostic, Prognostic, and Therapeutic Value of Non-Coding RNA Expression Profiles in Renal Transplantation

End-stage renal disease is a public health problem responsible for millions of deaths worldwide each year. Although transplantation is the preferred treatment for patients in need of renal replacement therapy, long-term allograft survival remains challenging. Advances in high-throughput methods for large-scale molecular data generation and computational analysis are promising to overcome the current limitations posed by conventional diagnostic and disease classifications post-transplantation. Non-coding RNAs (ncRNAs) are RNA molecules that, despite lacking protein-coding potential, are essential in the regulation of epigenetic, transcriptional, and post-translational mechanisms involved in both health and disease. A large body of evidence suggests that ncRNAs can act as biomarkers of renal injury and graft loss after transplantation. Hence, the focus of this review is to discuss the existing molecular signatures of non-coding transcripts and their value to improve diagnosis, predict the risk of rejection, and guide therapeutic choices post-transplantation.

Aberrant expression of long noncoding RNAs in the serum and myocardium of spontaneous hypertensive rats

Circulating long noncoding RNAs as biomarkers of diseases have attracted increasing attention recently. However, circulating lncRNAs in hypertension is still unexplored niche. The levels of lncRNAs GAS5, NR024118, MRAK134679, AX765700 and MRNR026574 were measured in the serum and myocardium of hypertensive rats and normal controls with real time PCR. The levels of GAS5 were significantly higher both in the myocardium (P = 0.0067) and serum (P < 0.0001) of hypertensive rats compared with controls. The levels of NR024118 were remarkably higher in the myocardium of hypertensive rats (P = 0.0202) while the levels of serum NR024118 were not statistically significant in two groups (P = 0.6926). The levels of serum AX765700 (P = 0.0644) and cardiac AX765700 (P = 0.1938) were not statistically significant in hypertensive rats and controls. The levels of MRAK134679 were not different in the myocardium of two groups (P = 0.1692) and were too low in the serum to be detected. The levels of MRNR026574 were significantly higher in the myocardium of hypertensive rats compared with controls (P < 0.0001) and were too low in the serum to be detected. In conclusions, the levels of GAS5, NR024118 and MRNR026574 were increased in the myocardium of hypertensive rats, suggesting that they participate in the pathogenesis of hypertensive cardiac remodeling. Although, the levels of GAS5 in the serum and heart tissue were both significantly increased in SH rats, the potential biomarker capacity of GAS5 for HT needs to be further explored on larger human cohorts.

Regulatory network of two circRNAs and an miRNA with their targeted genes under astilbin treatment in pulmonary fibrosis

Circular RNAs (circRNAs) are becoming new therapeutic drug targets. However, their profiles under astilbin treatment have not been reported yet. In this study, we analysed the global reprogramming of circRNA transcriptome and a regulatory network of circRNAs with their targeted genes under astilbin treatment in pulmonary fibrosis. A total of 145 circRNAs were differentially expressed in the astilbin-treated group compared with the bleomycin-treated group using RNA sequencing. In the bleomycin- and astilbin-treated groups, 29 coexpressed circRNAs were found. The maximum number of circRNAs was distributed on chromosome two, and their length varieties were mainly within 1000 bp. Four differentially expressed circRNAs (circRNA-662, 949, 394 and 986) were tested to validate the RNA sequencing data, and their targeted microRNAs and genes were analysed by qRT-PCR, Western blot, Pearson correlation coefficient, a dual-luciferase reporter system and anti-AGO2 RNA immunoprecipitation. The results showed that circRNA-662 and 949 can act as "miR-29b sponges" targeting Gli2 and STAT3 to exert their functions. Our work suggests that the transcriptome complexity at the circRNA level under astilbin treatment. These circRNAs may be potential molecular targets for drug action.

miR-185 affected the EMT, cell viability, and proliferation via DNMT1/MEG3 pathway in TGF-β1-induced renal fibrosis

Kidney fibrosis is usually the final manifestation of a wide variety of renal diseases. Recent years, research reported that long non-coding RNAs (lncRNAs) played important roles in a variety of human diseases. However, the role and underlying mechanisms of lncRNAs in kidney fibrosis were complicated and largely unclear. In our study, we constructed the cell model of renal fibrosis in HK2 cells using transforming growth factor β1 (TGF-β1) and found that lncRNA maternally expressed gene 3 (MEG3) was downregulated in TGF-β1-induced renal fibrosis. We then found that overexpressed MEG3 inhibited the TGF-β1-induced promotion of epithelial-mesenchymal transition, cell viability, and proliferation. Furthermore, we demonstrated that DNA methyltransferases 1 (DNMT1) regulated the MEG3 expression by altering the CpGs methylation level of MEG3 promoter in TGF-β1-induced renal fibrosis. In addition, we further revealed that miR-185 could regulate the DNMT1 expression and thus, modulate the MEG3 in TGF-β1-induced renal fibrosis. Ultimately, our study illustrated that the modulation of the miR-185/ DNMT1/ MEG3 pathway exerted important roles in TGF-β1-induced renal fibrosis. In summary, our finding displayed a novel regulatory mechanism for TGF-β1-induced renal fibrosis, which provided a new potential therapeutic target for renal fibrosis.

Circular RNAs as novel regulators, biomarkers and potential therapies in fibrosis

Fibrosis is the excess deposition of extracellular matrix components which ultimately leads to the disruption of organ architecture and loss of function. Circular RNAs (circRNAs) are a newly discovered type of long noncoding RNAs with single-stranded covalently closed loops. It is known that circRNAs are novel regulators of gene expression via various ways, including miRNA sponge, protein sponge, regulation of transcription and post transcription. Recently, a growing body of evidence suggests that circular RNAs are also involved in tissue fibrosis in several organs. In this review, we summarized current studies of circular RNAs in fibrosis and hopefully aid in better understanding the molecular mechanism of fibrosis and provide a basis to explore new therapeutic targets of fibrosis.

Fibroblasts in the Infarcted, Remodeling, and Failing Heart

Expansion and activation of fibroblasts following cardiac injury is important for repair but may also contribute to fibrosis, remodeling, and dysfunction. The authors discuss the dynamic alterations of fibroblasts in failing and remodeling myocardium. Emerging concepts suggest that fibroblasts are not unidimensional cells that act exclusively by secreting extracellular matrix proteins, thus promoting fibrosis and diastolic dysfunction. In addition to their involvement in extracellular matrix expansion, activated fibroblasts may also exert protective actions, preserving the cardiac extracellular matrix, transducing survival signals to cardiomyocytes, and regulating inflammation and angiogenesis. The functional diversity of cardiac fibroblasts may reflect their phenotypic heterogeneity.

Non-Coding RNAs as New Therapeutic Targets in the Context of Renal Fibrosis

Fibrosis, or tissue scarring, is defined as the excessive, persistent and destructive accumulation of extracellular matrix components in response to chronic tissue injury. Renal fibrosis represents the final stage of most chronic kidney diseases and contributes to the progressive and irreversible decline in kidney function. Limited therapeutic options are available and the molecular mechanisms governing the renal fibrosis process are complex and remain poorly understood. Recently, the role of non-coding RNAs, and in particular microRNAs (miRNAs), has been described in kidney fibrosis. Seminal studies have highlighted their potential importance as new therapeutic targets and innovative diagnostic and/or prognostic biomarkers. This review will summarize recent scientific advances and will discuss potential clinical applications as well as future research directions.

Regulatory Non-coding RNAs Network in Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) spectrum comprises simple steatosis and non-alcoholic steatohepatitis (NASH) that can lead to fibrosis and cirrhosis. The patients usually have no history of excessive alcohol consumption and other etiologies that can cause fatty liver. Understanding of the pathophysiology of NAFLD has revealed that non-coding RNAs (ncRNAs) play significant roles in modulating the disease susceptibility, pathogenesis and progression. Currently, the ncRNAs are grouped according to their sizes and their regulatory or housekeeping functions. Each of these ncRNAs has a wide range of involvement in the regulation of the genes and biological pathways. Here, we briefly review the current literature the regulatory ncRNAs in NAFLD pathogenesis and progression, mainly the microRNAs, long non-coding RNAs and circular RNAs. We also discuss the co-regulatory functions and interactions between these ncRNAs in modulating the disease pathogenesis. Elucidation of ncRNAs in NAFLD may facilitate the identification of early diagnostic biomarkers and development of therapeutic strategies for NAFLD.

Involvement of lncR-30245 in Myocardial Infarction-Induced Cardiac Fibrosis Through Peroxisome Proliferator-Activated Receptor-γ-Mediated Connective Tissue Growth Factor Signalling Pathway

BACKGROUND

Long noncoding RNAs (lncRNAs) are emerging as important mediators of cardiac pathophysiology. The aim of the present study is to investigate the effects of lncR-30245, an lncRNA, on cardiac fibrogenesis and the underlying mechanism.

METHODS

Myocardial infarction (MI) and transforming growth factor (TGF)-β1 were used to induce fibrotic phenotypes. Cardiac fibrosis was detected by Masson's trichrome staining. Cardiac function was evaluated by echocardiography. Western blot, quantitative reverse transcription-polymerase chain reaction, and pharmacological approaches were used to investigate the role of lncR-30245 in cardiac fibrogenesis.

RESULTS

Expression of lncR-30245 was significantly increased in MI hearts and TGF-β1-treated cardiac fibroblasts (CFs). LncR-30245 was mainly located in the cytoplasm. Overexpression of lncR-30245 promoted collagen production and CF proliferation. Knockdown of lncR-30245 significantly inhibited TGF-β1-induced collagen production and CF proliferation. LncR-30245 overexpression inhibited the antifibrotic role of peroxisome proliferator-activated receptor (PPAR)-γ and increased connective tissue growth factor (CTGF) expression, whereas lncR-30245 knockdown exerted the opposite effects. Rosiglitazone, a PPAR-γ agonist, significantly inhibited lncR-30245-induced CTGF upregulation and collagen production in CFs. In contrast, T0070907, a PPAR-γ antagonist, attenuated the inhibitory effects of lncR-30245 small interfering RNA (siRNA) on TGF-β1-induced CTGF expression and collagen production. LncR-30245 knockdown significantly enhanced ejection fraction and fractional shortening and attenuated cardiac fibrosis in MI mice.

CONCLUSION

Our study indicates that the lncR-30245/PPAR-γ/CTGF pathway mediates MI-induced cardiac fibrosis and might be a therapeutic target for various cardiac diseases associated with fibrosis.

Upregulated long noncoding RNA LOC105375913 induces tubulointerstitial fibrosis in focal segmental glomerulosclerosis

Tubulointerstitial fibrosis impacts renal prognosis of focal segmental glomerulosclerosis (FSGS). Based on transcriptomic analysis, we found that the level of LOC105375913 was increased in tubular cells of FSGS patients. C3a induced the expression of LOC105375913, which promoted the expression of fibronectin and collagen I in tubular cells. Silence of snail reversed the level of fibronectin and collagen I in cells overexpressing LOC105375913. MiR-27b was predicted and confirmed to regulate the expression of snail in tubular cells, and LOC105375913 contained the response element of miR-27b. The competitive binding between LOC105375913 and miR-27b increased the level of snail and promoted fibrogenesis in tubular cells. Upstream, p38 and XBP-1s regulated the expression of LOC105375913. Inhibition of p38 or silence of XBP-1s decreased the level of LOC105375913, and suppressed the expression of snail, fibronectin and collagen I in tubular cells treated with C3a. Overexpression of LOC105375913 decreased the level of miR-27b, increased the level of snail and caused tubulointerstitial fibrosis in mice. In conclusion, the activation of C3a/p38/XBP-1s pathway induces the expression of LOC105375913 in tubular cells, and LOC105375913 increases the level of snail and induces tubulointerstitial fibrosis through competitive binding of miR-27b in tubular cells of FSGS patients.

Long noncoding RNA homeobox A11 antisense promotes transforming growth factor β1‑induced fibrogenesis in cardiac fibroblasts

Cardiac fibrosis is closely associated with various heart diseases and is an important pathological feature of cardiac remodeling. However, detailed mechanisms underlying cardiac fibrosis remain largely unknown. Long noncoding RNAs (lncRNAs) are reported to serve significant roles in the development of cardiac fibrosis. The present study aimed to identify the role of a novel lncRNA, homeobox A11 antisense (HOXA11‑AS), in cardiac fibrosis. Overexpression of HOXA11‑AS in mouse cardiac fibroblasts (CFs) increased the expression of transforming growth factor β1 (TGFβ1) and its downstream molecules, while knockdown of HOXA11‑AS inhibited the TGFβ1 signaling pathway. Furthermore, as determined by colony formation and MTT assays, HOXA11‑AS overexpression promoted colony formation and viability in mouse CFs, while HOXA11‑AS knockdown had the opposite effect. In addition, overexpression of HOXA11‑AS increased cell migration and invasion in the Transwell assays, whereas expression knockdown decreased the metastatic ability of cells. In order to explore the detailed mechanism, co‑transfection of HOXA11‑AS expression plasmid and siTGFβ1 into CFs resulted in increased cell proliferative rate and cell metastasis through the TGFβ1 signaling pathway. Taken together, the present study suggested that the lncRNA HOXA11‑AS may be a potential therapeutic target against cardiac fibrosis, and provided a novel insight into the diagnosis and treatment of clinical cardiac fibrosis.

Integrated Analysis of lncRNA and mRNA Transcriptomes Reveals New Regulators of Ubiquitination and the Immune Response in Silica-Induced Pulmonary Fibrosis

Objectives

As an epigenetic player, long noncoding RNAs (LncRNAs) have been reported to participate in multiple biological processes; however, their biological functions in silica-induced pulmonary fibrosis (SIPF) occurrence and development remain incompletely understood.

Methods

Five case/control pairs were used to perform integrated transcriptomes analysis of lncRNA and mRNA. Prediction of lncRNA and mRNA functions was aided by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Additionally, we constructed a coexpression network of lncRNAs and mRNAs to identify targets of regulation.

Results

In total, 1069 differentially expressed mRNAs and 366 lncRNAs were identified with the changes more than 2 times (p<0.05), of which 351 downregulated mRNA and 31 downregulated lncRNA were <0.5 (p<0.05) and those of 718 upregulated mRNAs and 335 upregulated lncRNA were >2 (p<0.05). The levels of 10 lncRNAs were measured via qRT-PCR; the results were consistent with the microarray data. Four genes named of FEM1B, TRIM39, TRIM32, and KLHL15 were enriched significantly with ubiquitination and immune response. Cytokine-cytokine receptor interaction was the most significantly enriched KEGG pathway in both mRNAs and lncRNAs. The coexpression network revealed that a single lncRNA can interact with multiple mRNAs, and vice versa.

Conclusions

lncRNA and mRNA expression were aberrant in patients with SIPF compared to controls, indicating that differentially expressed lncRNAs and mRNAs may play critical roles in SIPF development. Our study affords new insights into the molecular mechanisms of SIPF and identifies potential biomarkers and targets for SIPF diagnosis and treatment.

Advanced glycation end products of bovine serum albumin affect the cell growth of human umbilical vein endothelial cells via modulation of MEG3/miR-93/p21 pathway

Advanced glycation end products of BSA (AGE-BSA) contribute to the pathogenesis of diabetic vascular diseases. However, the roles and underlying mechanisms of AGE-BSA in diabetic vascular diseases remain largely unclear. Long non-coding RNAs (lncRNAs) are widely identified and known as gene regulators. However, the roles of lncRNAs in diabetic vascular disease are still vague. In this study, we sought to investigate the contributions of lncRNAs in human umbilical vein endothelial cells (HUVECs) treated with AGE-BSA. We first demonstrated that AGE-BSA reduced the cell viability and inhibited the cell proliferation of HUVECs. Then, we found that lncRNA MEG3 was up-regulated in HUVECs treated with AGE-BSA. Furthermore, inhibition of MEG3 restored the AGE-BSA-induced repression of cell viability and proliferation. In addition, our results revealed that MEG3 played its role via modulation of miR-93 expression in HUVECs treated with AGE-BSA. Furthermore, we illustrated that miR-93 played its role via regulation of p21 in HUVECs treated with AGE-BSA. Ultimately, our study displayed that AGE-BSA exerted its function via modulation of MEG3/miR-93/p21 pathway in HUVECs. Thus, for the first time, we identified the MEG3/miR-93/p21 axis in HUVECs treated with AGE-BSA, which might be a novel regulatory network in diabetic vascular cells, and possess the potential therapeutic value for diabetes mellitus.

The long noncoding RNA LOC105374325 causes podocyte injury in individuals with focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a common kidney disease that results in nephrotic syndrome. FSGS arises from dysfunction and apoptosis of podocytes in the glomerulus of the kidney, leading to podocytopathy. The molecular mechanisms underlying podocyte apoptosis remain incompletely understood. Using an array of gene expression profiling, PCR, and in situ hybridization assay, we found here that the levels of the long noncoding RNA LOC105374325 were elevated in the renal podocytes of individuals with FSGS. We also observed that the microRNAs miR-34c and miR-196a/b down-regulated the expression of the apoptosis regulators BCL2-associated X, apoptosis regulator (Bax), and BCL2 antagonist/killer 1 (Bak) in podocytes. Competitive binding between LOC105374325 and miR-34c or miR-196a/b increased Bax and Bak levels and caused podocyte apoptosis. Of note, the mitogen-activated protein kinase P38 and the transcription factor CCAAT enhancer-binding protein β (C/EBPβ) up-regulated LOC105374325 expression. P38 inhibition or C/EBPβ silencing decreased LOC105374325 levels and inhibited apoptosis in adriamycin-treated podocytes. LOC105374325 overexpression decreased miR-34c and miR-196a/b levels, increased Bax and Bak levels, and induced proteinuria and focal segmental lesions in mice. In conclusion, activation of the P38/C/EBPβ pathway stimulates the expression of LOC105374325, which, in turn, increases Bax and Bak levels and causes apoptosis by competitively binding to miR-34c and miR-196a/b in the podocytes of individuals with FSGS.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

lncRNA PFAL promotes lung fibrosis through CTGF by competitively binding miR-18a

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic parenchymal lung disease of unknown etiology and lacks an effective intervention. Long noncoding RNAs (lncRNAs) participate in organ fibrosis and various pulmonary diseases, but the role of lncRNAs in lung fibrosis is not fully understood. In the present study, we identified that lncRNA NONMMUT021928, designated as pulmonary fibrosis-associated lncRNA (PFAL), was up-regulated in the lungs of mice with experimental lung fibrosis, and in TGF-β1-induced fibrotic lung fibroblasts. Further study showed that overexpression of PFAL promoted cell proliferation, migration, and fibroblast-myofibroblast transition. Overexpression further resulted in extracellular matrix deposition and fibrogenesis in lung fibroblasts through regulation of microRNA-18a (miR-18a). Importantly, knockdown of PFAL alleviated lung fibrosis both in vitro and in vivo. Mechanistically, our study showed that PFAL promoted lung-fibroblast activation and fibrogenesis by acting as a competing endogenous RNA for miR-18a: forced expression of PFAL inhibited the expression and activity of miR-18a, whereas silencing of PFAL had the opposite effect. Furthermore, we found that miR-18a was decreased during lung fibrosis in vitro and in vivo, as well as in patients with IPF. Moreover, knockdown of miR-18a led to fibrogenesis in lung fibroblasts, whereas enhanced expression of miR-18a attenuated TGF-β1-induced lung fibrosis by directly targeting the regulation of connecting tissue growth factor. Taken together, these results revealed the effect and mechanism of lncRNA PFAL in pulmonary fibrosis and suggested that PFAL depletion may provide a novel strategy for the treatment of lung fibrosis.-Li, X., Yu, T., Shan, H., Jiang, H., Sun, J., Zhao, X., Su, W., Yang, L., Shan, H., Liang, H. lncRNA PFAL promotes lung fibrosis through CTGF by competitively binding miR-18a.