miR-26a regulates mouse hepatocyte proliferation via directly targeting the 3' untranslated region of CCND2 and CCNE2

Epigenetic regulation in liver regeneration

The liver is considered unique in its enormous capacity for regeneration and self-repair. In contrast to other regenerative organs (i.e., skin, skeletal muscle, and intestine), whether the adult liver contains a defined department of stem cells is still controversial. In order to compensate for the massive loss of hepatocytes following liver injury, the liver processes a precisely controlled transcriptional reprogram that can trigger cell proliferation and cell-fate switch. Epigenetic events are thought to regulate the organization of chromatin architecture and gene transcription during the liver regenerative process. In this review, we will summarize how changes to the chromatin by epigenetic modifiers are translated into cell fate transitions to restore liver homeostasis during liver regeneration.

The role of microRNAs in the different phases of liver regeneration

INTRODUCTION

Since the first discovery of microRNAs (miRs) extensive evidence reveals their indispensable role in different patho-physiological processes. They are recognized as critical regulators of hepatic regeneration, as they modulate multiple complex signaling pathways affecting liver regeneration. MiR-related translational suppression and degradation of target mRNAs and proteins are not limited to one specific gene, but act on multiple targets.

AREAS COVERED

In this review, we are going to explore the role of miRs in the context of liver regeneration and discuss the regulatory effects attributed to specific miRs. Moreover, specific pathways crucial for liver regeneration will be discussed, with a particular emphasis on the involvement of miRs within the respective signaling cascades.

EXPERT OPINION

The considerable amount of studies exploring miR functions in a variety of diseases paved the way for the development of miR-directed therapeutics. Clinical implementation has already shown promising results, but additional research is warranted to assure safe and efficient delivery. Nevertheless, given the broad functional properties of miRs and their critical involvement during hepatic regeneration, they represent an attractive treatment target to promote liver recovery after hepatic resection.

Overexpression of miR-125a-5p Inhibits Hepatocyte Proliferation through the STAT3 Regulation In Vivo and In Vitro

microRNAs (miRNAs) are critically involved in liver regeneration (LR). miR-125a-5p (miR-125a) is a tumor-suppressing miRNA, but its role in LR has not been studied. Our previous studies have proved that miR-125a was related to LR at the initiation phase, while the mechanism hepatocyte proliferation triggered by miR-125a in LR has been rarely evaluated. Herein, we mainly studied the molecular mechanism of miR-125a in triggering hepatocyte proliferation and the proliferation stage of LR. Firstly, a striking reduction of miR-125a was found at 24 h as well as 30 h following partial hepatectomy (PH) in rat liver tissue by miRNAs expression profiles as well as qRT-PCR analysis. Furthermore, in vitro, upregulation of miR-125a decreased proliferation as well as G1/S conversion, which promoted hepatocytes apoptosis. STAT3 was the target of miR-125a. In vivo, upregulation of miR-125a by tail vein injection of agomir inhibited LR index. Upregulation of miR-125a inhibited LR index and hepatocytes proliferation by STAT3/p-STAT3/JUN/BCL2 axis. In summary, these current discoveries indicated that miR-125a inhibited hepatocytes proliferation as well as LR by targeting STAT3 and via acting on the STAT3/p-STAT3/JUN/BCL2 axis.

The antagonistic effects and mechanisms of microRNA-26a action in hypertensive vascular remodelling

BACKGROUND AND PURPOSE

Hypertensive vascular remodelling is responsible for end-organ damage and is the result of increased extracellular matrix accumulation and excessive vascular smooth muscle cell (VSMC) proliferation. MicroRNA-26a (miR-26a), a non-coding small RNA, is involved in several cardiovascular diseases. We aimed to validate the effect and mechanisms of miR-26a in hypertensive vascular remodelling.

EXPERIMENTAL APPROACH

Male spontaneously hypertensive rats (SHRs) were injected intravenously with recombinant adeno-associated virus-miR-26a. Samples of thoracic aorta were examined histologically with H&E staining. In vitro, angiotensin II (AngII)-induced VSMCs cultured from thoracic aortae of female Sprague-Dawley rats, were transfected with miR-26a mimic or inhibitor. Western blots, qRT-PCR and immunohistological methods were used, along with chromatin-immunoprecipitation and luciferase reporter assays. Specific siRNAs were used to silence Smad production in VSMCs KEY RESULTS: Levels of miR-26a were lower in the thoracic aorta and plasma of SHRs than in WKY rats. Overexpression of miR-26a inhibited extracellular matrix deposition by targeting connective tissue growth factor (CTGF) and decreased VSMC proliferation by regulating the enhancer of zeste homologue 2 (EZH2)/p21 pathway both in vitro and in vivo. AngII-mediated Smad3 activation suppressed miR-26a expression, which in turn promoted Smad3 activation via targeted regulation of Smad4, leading to further down-regulation of miR-26a.

CONCLUSION AND IMPLICATIONS

Our data show that AngII stimulated a Smads/miR-26a positive feedback loop, which further reduced expression of miR-26a, leading to collagen production and VSMC proliferation and consequently vascular remodelling. MiR-26a has an antagonistic effect on hypertensive vascular remodelling and can be a strategy for treating hypertensive vascular remodelling.

MiR-203a-3p targets PTEN to promote hepatocyte proliferation by regulating PI3K/Akt pathway in BRL-3A cells

This study was designed to investigate the role of miR-203a-3p in hepatocyte proliferation. Data analysis showed that up-regulation of miR-203a-3p increased the cell viability and cell proliferation, and inhibited apoptosis. Further experiments demonstrated that PTEN was a target gene of miR-203a-3p, and miR-203a-3p targeted PTEN to regulate the above functions. Overexpression of PTEN partially reversed the inhibition of PTEN and the activation of p-Akt/Akt induced by miR-203a-3p mimic. Our study revealed that miR-203a-3p might activate PI3K/Akt signaling pathway by inhibiting PTEN expression, thereby promoting cell proliferation.

MicroRNA-26a targets the mdm2/p53 loop directly in response to liver regeneration

Liver regeneration (LR) is the result of a dynamic balance between the increased proliferation and decreased apoptosis of hepatocytes. However, the role of microRNA (miR)‑26a in regulating complex signalling networks involving E3 ubiquitin‑protein ligase Mdm2 (mdm2), p53, p21 and p27 in the process of LR is currently unclear. In the present study, it was hypothesized that miR‑26a may negatively regulate the mdm2/p53 signalling loop in response to LR. In vitro experiments were performed, whereby mouse liver cells were transfected with an miR‑26a vector or an anti/miR‑26a vector. Cell proliferation was analysed using an MTS assay and cell apoptosis, and cell cycle progression were analysed by flow cytometry. In addition, the expression of mdm2, p53, p21 and p27 were assessed using western blotting and reverse transcription‑quantitative polymerase chain reaction analyses. Dual‑luciferase reporter assays were also used to examine the association between mdm2 and miR‑26a. A 70% partial hepatectomy in C57BL/6J mice was then performed, which was followed by injection with an mdm2‑cDNA vector or an mdm2‑small interfering RNA vector. The liver‑to‑body weight ratio and liver function of mice were measured at 72 h following vector administration. The results demonstrated an increase in hepatocyte proliferation accompanied by decreased hepatocyte apoptosis levels. In addition, inhibition of miR‑26a expression was associated with a marked increase in mdm2 expression, while the expression of p53, p21 and p27 was decreased when compared with negative controls. The opposite effects were observed when miR‑26a was overexpressed. Notably, miR‑26a was demonstrated to target the 3'‑untranslated region of mdm2 directly. The results of the present study are the first to demonstrate as far as the authors are aware that the mdm2/p53 negative feedback loop may be targeted by miR‑26a directly in response to LR, and that mdm2 negatively regulates p53, p21 and p27 but not miR‑26a. miR‑26a may therefore function as an important factor that regulates the interaction between mdm2 and p53.

MiR-26a promotes apoptosis of porcine granulosa cells by targeting the 3β-hydroxysteroid-Δ24-reductase gene

Objective

Apoptosis of ovarian granulosa cells (GCs) affects mammalian follicular development and fecundity. This study aimed to explore the regulatory relationship between microRNA-26a (miR-26a) and the 3β-hydroxysteroid-Δ24-reductase gene (DHCR24) gene in porcine follicular granular cells (pGCs), and to provide empirical data for the development of methods to improve the reproductive capacity of pigs.

Methods

The pGCs were transfected with miR-26a mimic, miR-26a inhibitor and DHCR24-siRNA in vitro. The cell apoptosis rate of pGCs was detected by the flow cytometry. The secretion levels of estradiol (E2) and progesterone (P) in pGCs were detected by enzyme-linked immunosorbent assay. Double luciferase validation system was used to detect the binding sites between miR-26a and DHCR24 3′-UTR region. Qualitative real-time polymerase chain reaction and Western blotting were used to verify the DHCR24 mRNA and protein expression in pGCs, respectively, after transfecting with miR-26a mimic and miR-26a inhibitor.

Results

Results showed that enhancement of miR-26a promoted apoptosis, and inhibited E2 and P secretion in pGCs. Meanwhile, inhibition of DHCR24 also upregulated the Caspase-3 expression, reduced the BCL-2 expression, promoted pGCs apoptosis, and inhibited E2 and P secretion in pGCs. There were the binding sites of miR-26a located within DHCR24 3′-UTR. Up-regulation of miR-26a inhibited DHCR24 mRNA and protein expression in pGCs.

Conclusion

This study demonstrates that miR-26a can promote cell apoptosis and inhibit E2 and P secretion by inhibiting the expression of DHCR24 in pGCs.

MicroRNA-26a: An Emerging Regulator of Renal Biology and Disease

MicroRNAs (miRNAs) are short, single-stranded, noncoding RNAs that modulate many key biological processes by simultaneously suppressing multiple target genes. Among them, miR-26a, a conserved miRNA among vertebrates, is highly expressed in various tissues. Accumulating evidence demonstrates that miR-26a plays pivotal roles in cellular differentiation, cell growth, apoptosis, and metastasis, thereby participating in the initiation and development of various human diseases, such as metabolic disease and cancer. More recently, miR-26a was found as a versatile regulator of renal biology and disease. miR-26a is intensively involved in the maintenance of podocyte homeostasis and the actin cytoskeleton. It is also able to modulate the homeostasis and function of mesangial cells. In addition, miR-26a affects the expansion of regulatory T cells in the context of ischemia-reperfusion injury and autoimmune diabetes and thus protects the renal system from immune attack. These available data strongly suggest that renal miR-26a possesses critical pathological functions and represents a potential target for renal disease therapies. This review summarizes current knowledge of miR-26a in renal biology and disease, laying the foundation for exploring its previously unknown functions and mechanisms in the renal system.

Comparison of the Transcriptomes and Proteomes of Serum Exosomes from Marek's Disease Virus-Vaccinated and Protected and Lymphoma-Bearing Chickens

Marek's disease virus (MDV) is the causative agent of Marek's disease (MD), a complex pathology of chickens characterized by paralysis, immunosuppression, and T-cell lymphomagenesis. MD is controlled in poultry production via vaccines administered in ovo or at hatch, and these confer protection against lymphoma formation, but not superinfection by MDV field strains. Despite vaccine-induced humoral and cell-mediated immune responses, mechanisms eliciting systemic protection remain unclear. Here we report the contents of serum exosomes to assess their possible roles as indicators of systemic immunity, and alternatively, tumor formation. We examined the RNA and protein content of serum exosomes from CVI988 (Rispens)-vaccinated and protected chickens (VEX), and unvaccinated tumor-bearing chickens (TEX), via deep-sequencing and mass spectrometry, respectively. Bioinformatic analyses of microRNAs (miRNAs) and predicted miRNA targets indicated a greater abundance of tumor suppressor miRNAs in VEX compared to TEX. Conversely, oncomiRs originating from cellular (miRs 106a-363) and MDV miRNA clusters were more abundant in TEX compared to VEX. Most notably, mRNAs mapping to the entire MDV genome were identified in VEX, while mRNAs mapping to the repeats flanking the unique long (IRL/TRL) were identified in TEX. These data suggest that long-term systemic vaccine-induced immune responses may be mediated at the level of VEX which transfer viral mRNAs to antigen presenting cells systemically. Proteomic analyses of these exosomes suggested potential biomarkers for VEX and TEX. These data provide important putative insight into MDV-mediated immune suppression and vaccine responses, as well as potential serum biomarkers for MD protection and susceptibility.

MicroRNA Profile in Peripheral Blood Mononuclear Cells from Hepatitis B Virus Infected Patients

INTRODUCTION AND AIM

The pathogenesis of hepatitis B virus (HBV)-related liver diseases remains not fully understood. Here, we aim to explore the potential roles of dysregulated miRNAs in chronic hepatitis B (CHB) and HBV-related acute-on-chronic liver failure (ACLF).

MATERIAL AND METHODS

MiRNA microarray was conducted in peripheral blood mononuclear cells (PBMCs) obtained from healthy donors or patients with CHB or ACLF. Altered expression of miRNAs was further confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Finally, the differentially expressed miRNAs and their target genes were subjected to bioinformatics analysis.

RESULTS

The miRNA microarray identified 45 up-regulated and 62 down-regulated miRNAs with a fold change ≥ 1.5. Expression of eight miRNAs was validated using qRT-PCR analysis, which was consistent with miRNA microarray analysis. Bioinformatics analysis indicated that multiple biological processes and signaling pathways were affected by these miRNAs and a miRNA-gene regulatory network was generated with Cytoscape.

CONCLUSION

The current study provided a global view of miRNA expression in PBMCs from CHB and ACLF patients. Functional analysis showed that multiple biological processes and signaling pathways were modulated by these miRNAs. These data provide intriguing insights into the molecular pathogenesis of HBVrelated liver diseases, which deserve further investigation.

miR-26a suppresses autophagy in swine Sertoli cells by targeting ULK2

A large number of microRNAs (miRNAs) have been detected from porcine testicular tissues thanks to the development of high-throughput sequencing technology. However, the regulatory roles of most identified miRNAs in swine testicular development or spermatogenesis are poorly understood. In our previous study, ULK2 (uncoordinated-51-like kinase 2) was predicted as a target gene of miR-26a. In this study, we aimed to investigate the role of miR-26a in swine Sertoli cell autophagy. The relative expression of miR-26a and ULK2 levels has a significant negative correlation (R²  = .5964, p ≤ .01) in nine developmental stages of swine testicular tissue. Dual-luciferase reporter assay results show that miR-26a directly targets the 3'UTR of the ULK2 gene (position 618-624). In addition, both the mRNA and protein expression of ULK2 were downregulated by miR-26a in swine Sertoli cells. These results indicate that miR-26a targets the ULK2 gene and downregulates its expression in swine Sertoli cells. Based on the expression of marker genes (LC3, p62 and Beclin-1), overexpression of miR-26a or knock-down of ULK2 inhibits swine Sertoli cell autophagy. Taken together, these findings demonstrate that miR-26a suppresses autophagy in swine Sertoli cells by targeting ULK2.

miR-26a promoted endometrial epithelium cells (EECs) proliferation and induced stromal cells (ESCs) apoptosis via the PTEN-PI3K/AKT pathway in dairy goats

Changes in endometrial cell morphology and function are absolutely necessary for successful embryo implantation. In this study, miR-26a was widely expressed in dairy goats, and was found to be regulated by β-estradiol (E2) and progesterone (P4) in endometrial epithelium cells (EECs) as well as stromal cells (ESCs). Furthermore, miR-26a played a role in the regulation of cells proliferation and apoptosis by directly regulating PTEN and indirectly regulating the PI3K/AKT pathway in EECs but not in ESCs of dairy goats in vitro. In addition, miR-26a regulated the expression of osteopontin (OPN), vascular endothelial growth factor (VEGF), Cyclooxygenase-2 (COX-2), and prolactin (PRL) in endometrial cells. Therefore, we could get a conclusion that miR-26a had very complex and diverse functions in the endometrial cells during the development of endometrial receptivity in dairy goats. This study provided an efficient platform for studying the regulatory effect of miR-26a on endometrial cells during the development of endometrial receptivity in dairy goats.

CircRNA-9119 regulates the expression of prostaglandin-endoperoxide synthase 2 (PTGS2) by sponging miR-26a in the endometrial epithelial cells of dairy goat

Circular RNAs (circRNAs) have been found to play important functional roles in epigenetic regulation under certain physiological and pathological conditions. However, knowledge of circRNAs during the development of receptive endometrium (RE) from pre-RE is limited. In the RE of dairy goats, higher circRNA-9119 levels, with lower miR-26a and higher prostaglandin-endoperoxide synthase 2 (PTGS2) levels, were detected. Further study showed that circRNA-9119 decreased levels of miR-26a by acting as a microRNA sponge, and that miR-26a downregulated the expression of PTGS2 via the predicted target site in endometrial epithelial cells (EECs) of dairy goats in vitro. In this way, circRNA-9119 functioned as a competing endogenous RNAs (ceRNA) that sequestered miR-26a, thereby protecting PTGS2 transcripts from miR-26a-mediated suppression in dairy goat EECs in vitro. Furthermore, PTGS2 participated in the regulation of some protein markers for endometrial receptivity in dairy goat EECs in vitro. Thus, a circRNA-9119–miR-26a–PTGS2 pathway in the endometrium was identified, and modulation of circRNA-9119–miR-26a–PTGS2 expression in EECs may emerge as a potential target to regulate the development of RE.

Characterization of Lgr5+ Progenitor Cell Transcriptomes after Neomycin Injury in the Neonatal Mouse Cochlea

Lgr5+ supporting cells (SCs) are enriched hair cell (HC) progenitors in the cochlea. Both in vitro and in vivo studies have shown that HC injury can spontaneously activate Lgr5+ progenitors to regenerate HCs in the neonatal mouse cochlea. Promoting HC regeneration requires the understanding of the mechanism of HC regeneration, and this requires knowledge of the key genes involved in HC injury-induced self-repair responses that promote the proliferation and differentiation of Lgr5+ progenitors. Here, as expected, we found that neomycin-treated Lgr5+ progenitors (NLPs) had significantly greater HC regeneration ability, and greater but not significant proliferation ability compared to untreated Lgr5+ progenitors (ULPs) in response to neomycin exposure. Next, we used RNA-seq analysis to determine the differences in the gene-expression profiles between the transcriptomes of NLPs and ULPs from the neonatal mouse cochlea. We first analyzed the genes that were enriched and differentially expressed in NLPs and ULPs and then analyzed the cell cycle genes, the transcription factors, and the signaling pathway genes that might regulate the proliferation and differentiation of Lgr5+ progenitors. We found 9 cell cycle genes, 88 transcription factors, 8 microRNAs, and 16 cell-signaling pathway genes that were significantly upregulated or downregulated after neomycin injury in NLPs. Lastly, we constructed a protein-protein interaction network to show the interaction and connections of genes that are differentially expressed in NLPs and ULPs. This study has identified the genes that might regulate the proliferation and HC regeneration of Lgr5+ progenitors after neomycin injury, and investigations into the roles and mechanisms of these genes in the cochlea should be performed in the future to identify potential therapeutic targets for HC regeneration.

Differential miRNA Expression in the Liver of Balb/c Mice Protected by Vaccination during Crisis of Plasmodium chabaudi Blood-Stage Malaria

MicroRNAs are increasingly recognized as epigenetic regulators for outcome of diverse infectious diseases and vaccination efficacy, but little information referring to this exists for malaria. This study investigates possible effects of both protective vaccination and P. chabaudi malaria on the miRNome of the liver as an effector against blood-stage malaria using miRNA microarrays and quantitative PCR. Plasmodium chabaudi blood-stage malaria takes a lethal outcome in female Balb/c mice, but a self-healing course after immunization with a non-infectious blood-stage vaccine. The liver robustly expresses 71 miRNA species at varying levels, among which 65 miRNA species respond to malaria evidenced as steadily increasing or decreasing expressions reaching highest or lowest levels toward the end of the crisis phase on day 11 p.i. in lethal malaria. Protective vaccination does not affect constitutive miRNA expression, but leads to significant (p < 0.05) changes in the expression of 41 miRNA species, however evidenced only during crisis. In vaccination-induced self-healing infections, 18 miRNA-species are up- and 14 miRNA-species are down-regulated by more than 50% during crisis in relation to non-vaccinated mice. Vaccination-induced self-healing and survival of otherwise lethal infections of P. chabaudi activate epigenetic miRNA-regulated remodeling processes in the liver manifesting themselves during crisis. Especially, liver regeneration is accelerated as suggested by upregulation of let-7a-5p, let-7b-5p, let-7c-5p, let-7d-5p, let-7f-5p, let-7g-5p, let-7i-5p, miR-26a, miR-122-5p, miR30a, miR27a, and mir-29a, whereas the up-regulated expression of miR-142-3p by more than 100% is compatible with the view of enhanced hepatic erythropoiesis, possibly at expense of megakaryopoiesis, during crisis of P. chabaudi blood-stage malaria.