MicroRNA-181a-5p enhances cell proliferation in medullary thymic epithelial cells via regulating TGF-β signaling

Thymus in Cardiometabolic Impairments and Atherosclerosis: Not a Silent Player?

The thymus represents a primary organ of the immune system, harboring the generation and maturation of T lymphocytes. Starting from childhood, the thymus undergoes involution, being replaced with adipose tissue, and by an advanced age nearly all the thymus parenchyma is represented by adipocytes. This decline of thymic function is associated with compromised maturation and selection of T lymphocytes, which may directly impact the development of inflammation and induce various autoinflammatory disorders, including atherosclerosis. For a long time, thymus health in adults has been ignored. The process of adipogenesis in thymus and impact of thymic fat on cardiometabolism remains a mysterious process, with many issues being still unresolved. Meanwhile, thymus functional activity has a potential to be regulated, since islets of thymopoeisis remain in adults even at an advanced age. The present review describes the intricate process of thymic adipose involution, focusing on the issues of the thymus' role in the development of atherosclerosis and metabolic health, tightly interconnected with the state of vessels. We also review the recent information on the key molecular pathways and biologically active substances that may be targeted to manipulate both thymic function and atherosclerosis.

Natural killer cells immunosenescence and the impact of lifestyle management

Natural killer cells (NKs) are lymphocytes of the innate immune system that quickly respond to viruses, infections, and tumors during their short cell life cycle. However, it was recently found that NKs undergo quantitative, distributional, structural, and functional phenotypic changes during aging that suppress immune responses, which is known as immunosenescence. The aging host environment, cytokine regulation, cytomegalovirus status, and hypothalamic‒pituitary‒adrenal axis have significant effects on NK function. Different lifestyle management interventions modulate the number and cytotoxic activity of NKs, which are essential for rebuilding the immune barrier against pathogens in elderly individuals. Based on recent studies, we review the phenotypic changes of and potential threats of NKs during aging and explore the underlying mechanisms. By summarizing the effects of lifestyle management on NKs and their application prospects, we aim to provide evidence for enhancing immune system function against immune diseases in elderly individuals.

Epithelial-mesenchymal transition in age-associated thymic involution: Mechanisms and therapeutic implications

The thymus is a critical immune organ with endocrine and immune functions that plays important roles in the physiological and pathological processes of the body. However, with aging, the thymus undergoes degenerative changes leading to decreased production and output of naive T cells and the secretion of thymic hormones and related cytokines, thereby promoting the occurrence and development of various age-associated diseases. Therefore, identifying essential processes that regulate age-associated thymic involution is crucial for long-term control of thymic involution and age-associated disease progression. Epithelial-mesenchymal transition (EMT) is a well-established process involved in organ aging and functional impairment through tissue fibrosis in several organs, such as the heart and kidney. In the thymus, EMT promotes fibrosis and potentially adipogenesis, leading to thymic involution. This review focuses on the factors involved in thymic involution, including oxidative stress, inflammation, and hormones, from the perspective of EMT. Furthermore, current interventions for reversing age-associated thymic involution by targeting EMT-associated processes are summarized. Understanding the key mechanisms of thymic involution through EMT as an entry point may promote the development of new therapies and clinical agents to reverse thymic involution and age-associated disease.

Thymus aging and immune reconstitution, progresses and challenges

Thymus is a primary lymphoid organ essential for the development of T lymphocytes. Age-related thymic involution is a prominent feature of immune senescence. The thymus undergoes rapid growth during fetal and neonatal development, peaks in size before puberty and then begins to undergo a decrease in cellularity with age. Dramatic changes occur with age-associated thymic involution. The most prominent features of thymic involution include: (i) epithelial structure disruption, (ii) adipogenesis, and (iii) thymocyte development arrest. There is a sex disparity in thymus aging. It is a multifactorial process controlled and regulated by a series of molecules, including the transcription factor FOXN1, fibroblast and keratinocyte growth factors (FGF and KGF, respectively), sex steroids, Notch signaling, WNT signaling, and microRNAs. Nevertheless, there is still no satisfactory evolutionary or physiological explanation for age-associated thymic involution, and understanding the precise mechanism(s) for thymus aging remains challenging. Sustained thymic regeneration has yet to be achieved by sex steroid ablation. Recent preclinical studies indicate that long-term thymic reconstitution can be achieved via adoptive transfer of in vitro-generated progenitor T (proT) cells, and improvements in the methods for the generation of human proT cells make this an attractive approach. Future clinical applications may rely on new applications integrating proT cells, cytokine support and sex-steroid inhibition treatments.

An integrated analysis of dysregulated SCD1 in human cancers and functional verification of miR-181a-5p/SCD1 axis in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC), one of the most lethal cancers, has become a global health issue. Stearoyl-coA desaturase 1 (SCD1) has been demonstrated to play a crucial role in human cancers. However, pan-cancer analysis has revealed little evidence to date. In the current study, we systematically inspected the expression patterns and potential clinical outcomes of SCD1 in multiple human cancers. SCD1 was dysregulated in several types of cancers, and its aberrant expression acted as a diagnostic biomarker, indicating that SCD1 may play a role in tumorigenesis. We used ESCC as an example to demonstrate that SCD1 was dramatically upregulated in tumor tissues of ESCC and was associated with clinicopathological characteristics in ESCC patients. Furthermore, Kaplan-Meier analysis showed that high SCD1 expression was correlated with poor progression-free survival (PFS) and disease-free survival (DFS) in ESCC patients. The protein-protein interaction (PPI) network and module analysis by PINA database and Gephi were performed to identify the hub targets. Meanwhile, the functional annotation analysis of these hubs was constructed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Functionally, the gain-of-function of SCD1 in ESCC cells promoted cell proliferation, migration, and invasion; in contrast, loss-of-function of SCD1 in ESCC cells had opposite effects. Bioinformatic, QPCR, Western blotting and luciferase assays indicated that SCD1 was a direct target of miR-181a-5p in ESCC cells. In addition, gain-of-function of miR-181a-5p in ESCC cells reduced the cell growth, migratory, and invasive abilities. Conversely, inhibition of miR-181a-5p expression by its inhibitor in ESCC cells had opposite biological effects. Importantly, reinforced SCD1 in miR-181a-5p mimic ESCC transfectants reversed miR-181a-5p mimic-prevented malignant phenotypes of ESCC cells. Taken together, these results indicate that SCD1 expression influences tumor progression in a variety of cancers, and the miR-181a-5p/SCD1 axis may be a potential therapeutic target for ESCC treatment.

miRNA in Parkinson's disease: From pathogenesis to theranostic approaches

Parkinson's disease (PD) is an age associated neurological disorder which is specified by cardinal motor symptoms such as tremor, stiffness, bradykinesia, postural instability, and non-motor symptoms. Dopaminergic neurons degradation in substantia nigra region and aggregation of αSyn are the classic signs of molecular defects noticed in PD pathogenesis. The discovery of microRNAs (miRNA) predicted to have a pivotal part in various processes regarding regularizing the cellular functions. Studies on dysregulation of miRNA in PD pathogenesis has recently gained the concern where our review unravels the role of miRNA expression in PD and its necessity in clinical validation for therapeutic development in PD. Here, we discussed how miRNA associated with ageing process in PD through molecular mechanistic approach of miRNAs on sirtuins, tumor necrosis factor-alpha and interleukin-6, dopamine loss, oxidative stress and autophagic dysregulation. Further we have also conferred the expression of miRNAs affected by SNCA gene expression, neuronal differentiation and its therapeutic potential with PD. In conclusion, we suggest more rigorous studies should be conducted on understanding the mechanisms and functions of miRNA in PD which will eventually lead to discovery of novel and promising therapeutics for PD.

Effects of PAMK on lncRNA, miRNA, and mRNA expression profiles of thymic epithelial cells

Polysaccharides from Atractylodes macrocephala Koidz (PAMK) can promote the proliferation of thymocytes and improve the body's immunity. However, the effect of PAMK on thymic epithelial cells has not been reported. Studies have shown that miRNAs and lncRNAs are key factors in regulating cell proliferation. In this study, we found that PAMK could promote the proliferation of mouse medullary thymic epithelial cell line 1 (MTEC1) cells through CCK-8 and EdU experiments. To further explore its mechanism, we detected the effect of PAMK on the expression profiles of lncRNAs, miRNAs, and mRNAs in MTEC1 cells. The results showed that PAMK significantly affected the expression of 225 lncRNAs, 29 miRNAs, and 800 mRNAs. Functional analysis showed that these differentially expressed genes were significantly enriched in cell cycle, cell division, NF-kappaB signaling, apoptotic process, and MAPK signaling pathway. Finally, we used Cytoscape to visualize lncRNA-miRNA-mRNA(14 lncRNAs, 17 miRNAs, 171 mRNAs) networks based on ceRNA theory. These results suggest that lncRNAs and miRNAs may be involved in the effect of PAMK on the proliferation of MTEC1 cells, providing a new research direction for exploring the molecular mechanism of PAMK promoting the proliferation of thymic epithelial cells.

Age-related thymic involution: Mechanisms and functional impact

The thymus is the primary immune organ responsible for generating self‐tolerant and immunocompetent T cells. However, the thymus gradually involutes during early life resulting in declined naïve T‐cell production, a process known as age‐related thymic involution. Thymic involution has many negative impacts on immune function including reduced pathogen resistance, high autoimmunity incidence, and attenuated tumor immunosurveillance. Age‐related thymic involution leads to a gradual reduction in thymic cellularity and thymic stromal microenvironment disruption, including loss of definite cortical‐medullary junctions, reduction of cortical thymic epithelial cells and medullary thymic epithelial cells, fibroblast expansion, and an increase in perivascular space. The compromised thymic microenvironment in aged individuals substantially disturbs thymocyte development and differentiation. Age‐related thymic involution is regulated by many transcription factors, micro RNAs, growth factors, cytokines, and other factors. In this review, we summarize the current understanding of age‐related thymic involution mechanisms and effects.

Circ_0058792 regulates osteogenic differentiation through miR-181a-5p/Smad7 axis in steroid-induced osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) caused by steroids is a severe orthopedic disorder resulting from the use of high-dose steroid drugs, characterized by structural changes in the bone, joint dysfunction, and femoral head collapse. CircRNAs and miRNAs have increasingly been suggested to play pivotal roles in osteogenic differentiation and osteogenesis. Significant upregulation of circ_0058792 was observed in patients with steroid-induced ONFH. Bioinformatic analysis showed that circ_0058792 might act as a sponge for miR-181a-5p. This study further investigated the mechanisms underlying the role of circ_0058792 and miR-181a-5p in osteogenic differentiation in methylprednisolone-induced ONFH rats and MC3T3-E1 cells. The results showed a notable decrease in the serum of miR-181a-5p in methylprednisolone-induced ONFH rats. Silencing of circ_0058792 using siRNAs and overexpression of miR-181a-5p significantly increased alkaline phosphatase activity and matrix mineralization capacity. Additionally, markers for osteogenic differentiation were significantly upregulated in miR-181a-5p-transfected cells. However, overexpression of circ_0058792 and the addition of the miR-181a-5p inhibitor reversed this increase. Smad7 was identified to be miR-181a-5p's direct target and circ_0058792 was confirmed to be miR-181a-5p's competing endogenous RNA (ceRNA). Upregulation of miR-181a-5p promotes phosphorylation of Smad2 and Smad3. Furthermore, circ_0058792 and miR-181a-5p had opposing effects on Smad7 expression. Collectively, these findings indicate that circ_0058792 regulates osteogenic differentiation by sponging miR-181a-5p via the TGF-β/Smad7 pathway. These findings elucidated the functions of circ_0058792 and miR-181a-5p in the regulation of steroid-induced ONFH. Our findings also indicated that circ_0058792 and miR-181a-5p are possible diagnostic markers and therapeutic targets for treating steroid-induced ONFH.

miR-152-3p Represses the Proliferation of the Thymic Epithelial Cells by Targeting Smad2

MicroRNAs (miRNAs) control the proliferation of thymic epithelial cells (TECs) for thymic involution. Previous studies have shown that expression levels of miR-152-3p were significantly increased in the thymus and TECs during the involution of the mouse thymus. However, the possible function and potential molecular mechanism of miR-152-3p remains unclear. This study identified that the overexpression of miR-152-3p can inhibit, while the inhibition of miR-152-3p can promote, the proliferation of murine medullary thymic epithelial cell line 1 (MTEC1) cells. Moreover, miR-152-3p expression was quantitatively analyzed to negatively regulate Smad2, and the Smad2 gene was found to be a direct target of miR-152-3p, using the luciferase reporter assay. Importantly, silencing Smad2 was found to block the G1 phase of cells and inhibit the cell cycle, which was consistent with the overexpression of miR-152-3p. Furthermore, co-transfection studies of siRNA–Smad2 (siSmad2) and the miR-152-3p mimic further established that miR-152-3p inhibited the proliferation of MTEC1 cells by targeting Smad2 and reducing the expression of Smad2. Taken together, this study proved miR-152-3p to be an important molecule that regulates the proliferation of TECs and therefore provides a new reference for delaying thymus involution and thymus regeneration.

Fibrogenic signals persist in DAA-treated HCV patients after sustained virological response

BACKGROUND & AIMS

Patients with HCV who achieve a sustained virological response (SVR) on direct-acting antiviral (DAA) therapy still need to be monitored for signs of liver disease progression. To this end, the identification of both disease biomarkers and therapeutic targets is necessary.

METHODS

Extracellular vesicles (EVs) purified from plasma of 15 healthy donors (HDs), and 16 HCV-infected patients before (T0) and after (T6) DAA treatment were utilized for functional and miRNA cargo analysis. EVs purified from plasma of 17 HDs and 23 HCV-infected patients (T0 and T6) were employed for proteomic and western blot analyses. Functional analysis in LX2 cells measured fibrotic markers (mRNAs and proteins) in response to EVs. Structural analysis was performed by qPCR, label-free liquid chromatography-mass spectrometry and western blot.

RESULTS

On the basis of observations indicating functional differences (i.e. modulation of FN-1, ACTA2, Smad2/3 phosphorylation, collagen deposition) of plasma-derived EVs from HDs, T0 and T6, we performed structural analysis of EVs. We found consistent differences in terms of both miRNA and protein cargos: (i) antifibrogenic miR204-5p, miR181a-5p, miR143-3p, miR93-5p and miR122-5p were statistically underrepresented in T0 EVs compared to HD EVs, while miR204-5p and miR143-3p were statistically underrepresented in T6 EVs compared to HD EVs (p <0.05); (ii) proteomic analysis highlighted, in both T0 and T6, the modulation of several proteins with respect to HDs; among them, the fibrogenic protein DIAPH1 was upregulated (Log₂ fold change of 4.4).

CONCLUSIONS

Taken together, these results highlight structural EV modifications that are conceivably causal for long-term liver disease progression in patients with HCV despite DAA-mediated SVR.

LAY SUMMARY

Direct-acting antivirals lead to virological cure in the majority of patients with chronic hepatitis C virus infection. However, the risk of liver disease progression or complications in patients with fibrosis and cirrhosis remains in some patients even after virological cure. Herein, we show that extracellular vesicle modifications could be linked to long-term liver disease progression in patients who have achieved virological cure; these modifications could potentially be used as biomarkers or treatment targets in such patients.

Epigenetic modifications in thymic epithelial cells: an evolutionary perspective for thymus atrophy

Background

The thymic microenvironment is mainly comprised of thymic epithelial cells, the cytokines, exosomes, surface molecules, and hormones from the cells, and plays a vital role in the development, differentiation, maturation and homeostasis of T lymphocytes. However, the thymus begins to degenerate as early as the second year of life and continues through aging in human beings, leading to a decreased output of naïve T cells, the limited TCR diversity and an expansion of monoclonal memory T cells in the periphery organs. These alternations will reduce the adaptive immune response to tumors and emerging infectious diseases, such as COVID-19, also it is easier to suffer from autoimmune diseases in older people. In the context of global aging, it is important to investigate and clarify the causes and mechanisms of thymus involution.

Main body

Epigenetics include histone modification, DNA methylation, non-coding RNA effects, and chromatin remodeling. In this review, we discuss how senescent thymic epithelial cells determine and control age-related thymic atrophy, how this process is altered by epigenetic modification. How the thymus adipose influences the dysfunctions of the thymic epithelial cells, and the prospects of targeting thymic epithelial cells for the treatment of thymus atrophy.

Conclusion

Epigenetic modifications are emerging as key regulators in governing the development and senescence of thymic epithelial cells. It is beneficial to re-establish effective thymopoiesis, identify the potential therapeutic strategy and rejuvenate the immune function in the elderly.

Proteomic analysis of zearalenone toxicity on mouse thymic epithelial cells

Zearalenone (ZEA) is one of the most major food contaminants in cereal crops worldwide, risking health of both livestock and humans. This study aimed to assess the cytotoxicity and the underlying mechanism of ZEA on thymic epithelial cells. By using proteomics analysis, we identified 596 differentially expressed proteins in MTEC1 cells upon zearalenone exposure, of which 245 were upregulated and 351 were downregulated. Gene ontology (GO) analysis suggested that differentially expressed proteins were participated in protein synthesis, oxidative phosphorylation, and ATP binding. KEGG pathway enrichment analysis showed that differentially expressed proteins were mainly related to mitochndrial metabolism, such as citrate cycle (TCA cycle) and oxidative phosphorylation. We demonstrated that ZEA treatment was able to increase the intracellular reactive oxygen species (ROS) level, to decrease ΔΨm, ATP level, and the copy number of mtDNA, leading to necrotic cell death. Moreover, we showed that ZEA treatment inhibited cell proliferation and induced G2/M phase arrest by downregulation of proliferation-associated proteins ERK, p-ERK, CDK1, and p-CHK1. Taken together, we found that the toxicity of ZEA on thymic epithelial cells is mainly caused by the inhibition of mitochondrial dysfunction and cell proliferation. Our study might open new avenues for treatment strategies.

miR-199b-5p enhances the proliferation of medullary thymic epithelial cells via regulating Wnt signaling by targeting Fzd6

Thymic epithelial cells (TECs) are essential regulators of T-cell development and selection. miRNAs play critical roles in regulating TEC proliferation during the process of thymic aging. Our previous studies revealed that miR-199b-5p was upregulated in TECs from 1- to 3-month-old mice. But its function and potential mechanism are not clear. We hypothesized that miR-199b-5p may play an important role in age-related thymus involution via targeting some genes. To confirm it, the murine thymic epithelial cell line 1 (MTEC1) cells were used. Our results showed that overexpression of miR-199b-5p can enhance MTEC1 cell proliferation. On the contrary, repression of miR-199b-5p can inhibit MTEC1 cell proliferation. Meanwhile, it was confirmed that frizzled receptor 6 (Fzd6) is the direct target gene of miR-199b-5p. Furthermore, overexpression of miR-199b-5p can upregulate the expressions of β-catenin, Tcf7, Wnt4, and C-myc to activate Wnt signaling and cell cycle signaling. Silence of Fzd6 and co-transfection with siFzd6 and miR-199b-5p mimic/inhibitor confirmed that the biological function of miR-199b-5p is indeed by targeting Fzd6 in medullary TECs. Overall, miR-199b-5p is an important regulator in medullary TEC proliferation through targeting Fzd6 to activate Wnt signaling and cell cycle signaling. Our data indicate that miR-199b-5p may block the process of thymic aging and be a potential therapeutic target for thymus involution.

Comprehensive analysis of lncRNAs, miRNAs and mRNAs related to thymic development and involution in goose

Thymic involution is a sign of immunosenescence, but little is known about it in goose. miRNAs and lncRNAs are critical factors regulating organ growth and development. In this study, we comprehensively analyzed the profiles of lncRNAs, miRNAs and mRNAs during the development and involution of the thymus in Magang goose. The results showed that 2436 genes, 16 miRNAs and 417 lncRNAs were differentially co-expressed between the developmental (20-embryo age, 3-day post-hatch and 3-month age) and degenerative (6-month age) stages. The functional analysis showed that these differentially expressed genes were significantly enriched in cell proliferation, cell adhesion, apoptotic signaling pathway, and Notch signaling pathway. In addition, we established a gene-gene network through the STRING database and identified 50 key genes. Finally, we constructed a miRNA-mRNA network followed by a lncRNA-miRNA-mRNA network. These results suggest that lncRNAs and miRNAs may be involved in the regulation of thymic development and involution in goose.

miR-4286 is Involved in Connections Between IGF-1 and TGF-β Signaling for the Mesenchymal Transition and Invasion by Glioblastomas

The insulin-like growth factor (IGF)-1 and transforming growth factor (TGF)-β signal pathways are both recognized as important in regulating cancer prognosis, such as the epithelial-to-mesenchymal transition (EMT) and cell invasion. However, cross-talk between these two signal pathways in glioblastoma multiforme (GBM) is still unclear. In the present study, by analyzing data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GSE) 4412, GBM patients with higher IGF-1 levels exhibited poorer survival. Genes positively correlated with IGF-1 were enriched in EMT and TGF-β signal pathways. IGF-1 treatment enhanced mesenchymal marker expressions and GBM cell invasion. A significant positive correlation was observed for IGF-1 with TGF-β1 (TGFB1) or TGF-β receptor 2 (TGFBR2), both of which participate in TGF-β signaling and are risk genes in the GBM process. IGF-1 stimulation promoted both TGFB1 and TGFBR2 expressions. LY2157299, a TGF-β signaling inhibitor, attenuated IGF-1-enhanced GBM cell invasion and mesenchymal transition. By analyzing IGF-1-regulated microRNA (miR) profiles, miR-4286 was found to be significantly downregulated in IGF-1-treated cells and could be targeted to both TGFB1 and TGFBR2. Overexpression of miR-4286 significantly attenuated expressions of the IGF-1-mediated mesenchymal markers, TGFB1 and TGFBR2. Using kinase inhibitors, only U0126 treatment showed an inhibitory effect on IGF-1-reduced miR-4286 and IGF-1-induced TGFB1/TGFBR2 expressions, suggesting that MEK/ERK signaling is involved in the IGF-1/miR-4286/TGF-β signaling axis. Finally, our results suggested that miR-4286 might act as a tumor suppressive microRNA in inhibiting IGF-1-enhanced GBM cell invasion. In conclusion, IGF-1 is connected to TGF-β signaling in regulating the mesenchymal transition and cell invasion of GBM through inhibition of miR-4286. Our findings provide new directions and mechanisms for exploring GBM progression.

Role of miRNAs in Normal and Myasthenia Gravis Thymus

The thymus, a primary lymphoid organ, provides a complex environment essential for the generation of the T-cell repertoire. Thymic alterations occur during life either in the context of thymic involution upon aging or the pathophysiological context of Myasthenia Gravis (MG). These changes involve complicated regulatory networks, in which microRNAs (miRNAs) are key players. Here, we analyzed the role of miRNAs in thymocyte maturation and differentiation sustained by thymic epithelial cells. We compared data from the literature regarding the role of mouse thymic miRNAs and original data obtained from a human thymic miRnome study. We identified a set of highly expressed miRNAs defined as ThymiRs and investigated miRNA expression in infants as compared to adults to determine those associated with human thymic involution. Thymic changes are also frequently observed in MG, an autoimmune disease which results in the production of anti-acetylcholine receptor (AChR) antibodies that lead to muscle weaknesses. Alterations such as thymoma in late-onset MG patients and hyperplasia with ectopic germinal centers (GCs) in early-onset (EOMG) patients are found. Thymic miRNA expression has been studied in AChR-MG patients both in thymoma-associated MG (TAMG) and EOMG, and their function through their mRNA targets investigated. Most of the dysregulated thymic miRNAs in EOMG are associated with GC development, such as miR-7, miR-24, miR-139, miR-143, miR-145, miR-146, miR-150, miR-452, miR-548 or thymic inflammation, such as miR-125b, miR-146, or miR-29. Understanding these pathways may provide therapeutic targets or biomarkers of disease manifestations.

miR-205-5p inhibits thymic epithelial cell proliferation via FA2H-TFAP2A feedback regulation in age-associated thymus involution

Thymic epithelial cells (TECs) are essential regulators of T cell development and selection. microRNAs (miRNAs) play critical roles in regulating TECs proliferation during thymus involution. miR-205-5p is highly expressed in TECs and increases with age. However, the function and potential mechanism of miR-205-5p in TECs are not clear. miRNA expression was profiled using TECs from male and female mice at 1 and 3 months old. A total of 325 differentially expressed miRNAs (DEMs) were detected at different ages in two sexes. 24 of the DEMs had the same trend between males and females. Among them, miR-205-5p had the highest fold change. Our results showed that the expression of miR-205-5p was dramatically increased in TECs from 1 to 9 months old mice. miR-205-5p mimic inhibited TECs proliferation. Moreover, we confirmed that Fa2h was the direct target gene of miR-205-5p and FA2H was significantly decreased in TECs with increased expression of miR-205-5p. Silencing of Fa2h inhibited TECs proliferation. Furthermore, we found that the expression of Tfap2a could be promoted by FA2H and that TFAP2A could interact with miR-205-5p in TECs. Overall, miR-205-5p is an important regulator of TECs proliferation and regulates age-associated thymus involution via the miR-205-5p-FA2H-TFAP2A feedback regulatory circuit. miR-205-5p might act as a potential biomarker in TECs for age-related thymus involution.

Age-related transcriptional modules and TF-miRNA-mRNA interactions in neonatal and infant human thymus

The human thymus suffers a transient neonatal involution, recovers and then starts a process of decline between the 1^st and 2^nd years of life. Age-related morphological changes in thymus were extensively investigated, but the genomic mechanisms underlying this process remain largely unknown. Through Weighted Gene Co-expression Network Analysis (WGCNA) and TF-miRNA-mRNA integrative analysis we studied the transcriptome of neonate and infant thymic tissues grouped by age: 0–30 days (A); 31days-6 months (B); 7–12 months (C); 13–18 months (D); 19-31months (E). Age-related transcriptional modules, hubs and high gene significance (HGS) genes were identified, as well as TF-miRNA-hub/HGS co-expression correlations. Three transcriptional modules were correlated with A and/or E groups. Hubs were mostly related to cellular/metabolic processes; few were differentially expressed (DE) or related to T-cell development. Inversely, HGS genes in groups A and E were mostly DE. In A (neonate) one third of the hyper-expressed HGS genes were related to T-cell development, against one-twentieth in E, what may correlate with the early neonatal depletion and recovery of thymic T-cell populations. This genomic mechanism is tightly regulated by TF-miRNA-hub/HGS interactions that differentially govern cellular and molecular processes involved in the functioning of the neonate thymus and in the beginning of thymic decline.

Effects of Castration on miRNA, lncRNA, and mRNA Profiles in Mice Thymus

Thymic degeneration and regeneration are regulated by estrogen and androgen. Recent studies have found that long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are involved in organ development. In this study, RNA sequencing (RNA-seq) results showed that ovariectomy significantly affected 333 lncRNAs, 51 miRNAs, and 144 mRNAs levels (p < 0.05 and |log2fold change| > 1), and orchiectomy significantly affected 165 lncRNAs, 165 miRNAs, and 208 mRNA levels in the thymus. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differentially expressed genes (DEGs) were closely related to cell development and immunity. Next, we constructed two lncRNA–miRNA–mRNA networks using Cytoscape based on the targeting relationship between differentially expressed miRNAs (DEMs) and DEGs and differentially expressed lncRNAs (DELs) analyzed by TargetScan and miRanda. Besides, we screened DEGs that were significantly enriched in GO and in ceRNA networks to verify their expression in thymocytes and thymic epithelial cells (TECs). In addition, we analyzed the promoter sequences of DEGs, and identified 25 causal transcription factors. Finally, we constructed transcription factor-miRNA-joint target gene networks. In conclusion, this study reveals the effects of estrogen and androgen on the expression of miRNAs, lncRNAs, and mRNAs in mice thymus, providing new insights into the regulation of thymic development by gonadal hormones and non-coding RNAs.

miR-181a promotes porcine granulosa cell apoptosis by targeting TGFBR1 via the activin signaling pathway

Activin/Smad3 signaling plays a pivotal role in follicle development and atresia. However, the precise mechanisms underlying this process are not yet fully understood. Herein, we identified miR-181a as a central component of activin/Smad3-mediated follicle atresia. miR-181a was strikingly upregulated in porcine atretic follicles, which induced the apoptosis of porcine granulosa cells (GCs) in vitro. Furthermore, the transforming growth factor-β type 1 receptor (TGFBR1) was confirmed as a direct target of miR-181a by bioinformatics analysis and luciferase assays. Transfection with an miR-181a agomir repressed the TGFBR1 mRNA and protein levels. In addition, TGFBR1 overexpression repressed GC apoptosis, whereas TGFBR1 inhibition promoted GC apoptosis. miR-181a overexpression downregulated the phosphorylation of Smad3 and blocked the activation of TGF-β signaling. Moreover, activin A downregulated miR-181a expression and upregulated the TGFBR1 and p-Smad3 protein levels. Collectively, these data suggest that miR-181a regulates porcine GC apoptosis by targeting TGFBR1 via the activin signaling pathway.

Suppression of transforming growth factor-beta signaling enhances spermatogonial proliferation and spermatogenesis recovery following chemotherapy

STUDY QUESTION

Could small molecules (SM) which target (or modify) signaling pathways lead to increased proliferation of undifferentiated spermatogonia following chemotherapy?

SUMMARY ANSWER

Inhibition of transforming growth factor-beta (TGFb) signaling by SM can enhance the proliferation of undifferentiated spermatogonia and spermatogenesis recovery following chemotherapy.

WHAT IS KNOWN ALREADY

Spermatogonial stem cells (SSCs) hold great promise for fertility preservation in prepubertal boys diagnosed with cancer. However, the low number of SSCs limits their clinical applications. SM are chemically synthesized molecules that diffuse across the cell membrane to specifically target proteins involved in signaling pathways, and studies have reported their ability to increase the proliferation or differentiation of germ cells.

STUDY DESIGN, SIZE, DURATION

In our experimental study, spermatogonia were collected from four brain-dead individuals and used for SM screening in vitro. For in vivo assessments, busulfan-treated mice were treated with the selected SM (or vehicle, the control) and assayed after 2 (three mice per group) and 5 weeks (two mice per group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

We investigated the effect of six SM on the proliferation of human undifferentiated spermatogonia in vitro using a top–bottom approach for screening. We used histological, hormonal and gene-expression analyses to assess the effect of selected SM on mouse spermatogenesis. All experiments were performed at least in triplicate and were statistically evaluated by Student’s t-test and/or one-way ANOVA followed by Scheffe’s or Tukey’s post-hoc.

MAIN RESULTS AND THE ROLE OF CHANCE

We found that administration of SB431542, as a specific inhibitor of the TGFb1 receptor (TGFbR1), leads to a two-fold increase in mouse and human undifferentiated spermatogonia proliferation. Furthermore, injection of SB to busulfan-treated mice accelerated spermatogenesis recovery as revealed by increased testicular size, weight and serum level of inhibin B. Moreover, SB administration accelerated both the onset and completion of spermatogenesis. We demonstrated that SB promotes proliferation in testicular tissue by regulating the cyclin-dependent kinase (CDK) inhibitors 4Ebp1 and P57 (proliferation inhibitor genes) and up-regulating Cdc25a and Cdk4 (cell cycle promoting genes).

LIMITATIONS, REASONS FOR CAUTION

The availability of human testis was the main limitation in this study.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to report acceleration of spermatogenesis recovery following chemotherapy by administration of a single SM. Our findings suggest that SB is a promising SM and should be assessed in future clinical trials for preservation of fertility in men diagnosed with cancer or in certain infertility cases (e.g. oligospermia).

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Royan Institute and National Institute for Medical Research Development (NIMAD, grant no 963337) granted to H.B. The authors have no conflict of interest to report.

Adhesion between medullary thymic epithelial cells and thymocytes is regulated by miR-181b-5p and miR-30b

In this work, we demonstrate that adhesion between medullary thymic epithelial cells (mTECs) and thymocytes is controlled by miRNAs. Adhesion between mTECs and developing thymocytes is essential for triggering negative selection (NS) of autoreactive thymocytes that occurs in the thymus. Immune recognition is mediated by the MHC / TCR receptor, whereas adhesion molecules hold cell-cell interaction stability. Indeed, these processes must be finely controlled, if it is not, it may lead to aggressive autoimmunity. Conversely, the precise molecular genetic control of mTEC-thymocyte adhesion is largely unclear. Here, we asked whether miRNAs would be controlling this process through the posttranscriptional regulation of mRNAs that encode adhesion molecules. For this, we used small interfering RNA to knockdown (KD) Dicer mRNA in vitro in a murine mTEC line. A functional assay with fresh murine thymocytes co-cultured with mTECs showed that single-positive (SP) CD4 and CD8 thymocyte adhesion was increased after Dicer KD and most adherent subtype was CD8 SP cells. Analysis of broad mTEC transcriptional expression showed that Dicer KD led to the modulation of 114 miRNAs and 422 mRNAs, including those encoding cell adhesion or extracellular matrix proteins, such as Lgals9, Lgals3pb, Tnc and Cd47. Analysis of miRNA-mRNA networks followed by miRNA mimic transfection showed that these mRNAs are under the control of miR-181b-5p and miR-30b*, which may ultimately control mTEC-thymocyte adhesion. The expression of CD80 surface marker in mTECs was increased after Dicer KD following thymocyte adhesion. This indicates the existence of new mechanisms in mTECs that involve the synergistic action of thymocyte adhesion and regulatory miRNAs.

TGF-β induces liver fibrosis via miRNA-181a-mediated down regulation of augmenter of liver regeneration in hepatic stellate cells

OBJECTIVE

To study the role of miRNA-181a and augmenter of liver regeneration in TGF-β-induced fibrosis in hepatic stellate cells.

METHODS

LX2 cells were treated with 20 ng/ml TGF-β for 24 h. miRNA-181a, ALR plasmid and empty vectors were transfected using siPORT NeoFx reagent. Cells were harvested after 48 h or 72 h of transfection for protein or RNA analysis. Western blotting was performed for ALR, TGF-β receptor II (TGFβ-RII), collagen 1A1 (COLL1A1), alpha-smooth muscle cell actin (α-SMA), rac1, E-cadherin and β-actin. Quantitative RT-PCR was performed for ALR, GAPDH, miRNA-181a or 5S rRNA.

RESULTS

TGF-β induced the expression of miRNA-181a, which in turn down-regulated ALR thereby induced the fibrosis markers, such as COLL1A1, α-SMA and rac1 in hepatic stellate cells. Over-expression of miRNA-181a down-regulated expression of ALR and up-regulated expression of fibrosis markers. On the other hand, ALR over-expression resulted in a decrease in miRNA-181a expression and fibrosis markers. Over-expression of ALR also inhibited the expression of TGFβ-RII and increased expression E-cadherin.

CONCLUSION

TGF-β induced miRNA-181a, which in turn induced fibrosis, at least in part, by inhibiting ALR. ALR inhibited TGF-β action by decreasing the expression of TGFβ-RII, thereby inhibiting miRNA-181a expression and fibrosis markers. ALR could serve as a potential molecule to inhibit liver fibrosis.

Interplay between microRNAs and Wnt, transforming growth factor-β, and bone morphogenic protein signaling pathways promote osteoblastic differentiation of mesenchymal stem cells

Osteoblasts are terminally differentiated cells with mesenchymal origins, known to possess pivotal roles in sustaining bone microstructure and homeostasis. These cells are implicated in the pathophysiology of various bone disorders, especially osteoporosis. Over the last few decades, strategies to impede bone resorption, principally by bisphosphonates, have been mainstay of treatment of osteoporosis; however, in recent years more attention has been drawn on bone-forming approaches for managing osteoporosis. MicroRNAs (miRNAs) are a broad category of noncoding short sequence RNA fragments that posttranscriptionally regulate the expression of diverse functional and structural genes in a negative manner. An accumulating body of evidence signifies that miRNAs direct mesenchymal stem cells toward osteoblast differentiation and bone formation through bone morphogenic protein, transforming growth factor-β, and Wnt signaling pathways. MiRNAs are regarded as excellent future therapeutic candidates because of their small size and ease of delivery into the cells. Considering their novel therapeutic significance, this review discusses the main miRNAs contributing to the anabolic aspects of bone formation and illustrates their interactions with corresponding signaling pathways involved in osteoblastic differentiation.

MicroRNA Functions in Thymic Biology: Thymic Development and Involution

During the entire processes of thymus organogenesis, maturation, and involution, gene regulation occurs post-transcriptionally via recently discovered microRNA (miRNA) transcripts. Numerous reports indicate that miRNAs may be involved in the construction of a normal thymic microenvironment, which constitutes a critical component to support T lymphocyte development. MiRNAs are also expressed in thymic stromal cells including thymic epithelial cells (TECs) during maturation and senescence. This review focuses on the function of miRNAs in thymic development and involution. A better understanding of these processes will provide new insights into the regulatory network of TECs and further comprehension of how genes control TECs to maintain the thymic microenvironment during thymus development and aging, thus supporting a normal cellular immune system.

Minipuberty and Sexual Dimorphism in the Infant Human Thymus

AIRE expression in thymus is downregulated by estrogen after puberty, what probably renders women more susceptible to autoimmune disorders. Here we investigated the effects of minipuberty on male and female infant human thymic tissue in order to verify if this initial transient increase in sex hormones - along the first six months of life - could affect thymic transcriptional network regulation and AIRE expression. Gene co-expression network analysis for differentially expressed genes and miRNA-target analysis revealed sex differences in thymic tissue during minipuberty, but such differences were not detected in the thymic tissue of infants aged 7-18 months, i.e. the non-puberty group. AIRE expression was essentially the same in both sexes in minipuberty and in non-puberty groups, as assessed by genomic and immunohistochemical assays. However, AIRE-interactors networks showed several differences in all groups regarding gene-gene expression correlation. Therefore, minipuberty and genomic mechanisms interact in shaping thymic sexual dimorphism along the first six months of life.

Profiling analysis of 17β-estradiol-regulated lncRNAs in mouse thymic epithelial cells

Thymus is the primary organ for T cell differentiation and maturation. Many studies have demonstrated that estrogen plays a crucial role in thymic epithelial cell (TEC) proliferation during thymic involution. LncRNAs are involved in various biological processes; however, estrogen-mediated lncRNA expression in TECs has not been yet reported. To address this question, the mouse medullary thymic epithelial cell line 1 (MTEC1) was treated with 17β-estradiol (E2). By using CCK8 assay and flow cytometry, we found that E2 was able to inhibit viability and proliferation of MTEC1 cells. The expression profiles of lncRNAs in MTEC1 cells with or without E2 treatment were then measured by RNA-Seq, and a total of 962 lncRNAs and 2,469 mRNAs were shown to be differentially expressed. The reliability of RNA-Seq was confirmed by quantitative RT-PCR. Correlation analysis was conducted to investigate the potential function of lncRNAs. According to gene ontology (GO) analysis, differentially expressed lncRNAs were mainly related to cell proliferation, cell cycle and cell apoptosis. KEGG pathway analysis indicated that these lncRNAs were associated with several pathways, namely immunological activity, metabolism and cytokine-cytokine receptor interaction. In conclusion, our study provided a novel direction for studying the relationship between lncRNAs and E2 in the thymus.

Despite high levels of expression in thymic epithelial cells, miR-181a1 and miR-181b1 are not required for thymic development

MicroRNAs (miRNAs) have been shown to be key modulators of post-transcriptional gene silencing in many cellular processes. In previous studies designed to understand the role of miRNAs in thymic development, we globally deleted miRNA exclusively in thymic epithelial cells (TECs), which are critical in thymic selection. This resulted in the loss of stromal cells that instruct T cell lineage commitment and affect thymocyte positive selection, required for mature T cell development. Since murine miR-181 is expressed in the thymus and miR-181 deficiency disrupts thymocyte development, we first quantified and thereby demonstrated that miR181a1 and miR181b1 are expressed in purified TECs. By generating mice with TEC targeted loss of miR-181a1 and miR-181b1 expression, we observed that neither TEC cellularity nor thymocyte number nor differentiation was adversely affected. Thus, disrupted thymopoiesis in miR-181 deficient mice was not due to miR-181 loss of expression in TECs. Importantly, in mice with restricted TEC deficiency of miR-181a1 and miR-181b1, there were similar numbers of mature T cells in the periphery in regards to frequencies, differentiation, and function as compared to controls. Moreover miR-181a1 and miR-181b1 were not required for maintenance of thymus integrity over time, as thymic involution was not accelerated in gene-targeted mice. Taken together our data indicate that miR-181a1 and miR-181b1 are dispensable for TEC differentiation, their control of thymocyte development and mature T cell export to and homeostasis within the periphery.

MicroRNAs Regulate Thymic Epithelium in Age-Related Thymic Involution via Down- or Upregulation of Transcription Factors

Age-related thymic involution is primarily induced by defects in nonhematopoietic thymic epithelial cells (TECs). It is characterized by dysfunction of multiple transcription factors (TFs), such as p63 and FoxN1, and also involves other TEC-associated regulators, such as Aire. These TFs and regulators are controlled by complicated regulatory networks, in which microRNAs (miRNAs) act as a key player. miRNAs can either directly target the 3'-UTRs (untranslated regions) of the TFs to suppress TF expression or target TF inhibitors to reduce or increase TF inhibitor expression and thereby indirectly enhance or inhibit TF expression. Here, we review the current understanding and recent studies about how miRNAs are involved in age-related thymic involution via regulation of TEC-autonomous TFs. We also discuss potential strategies for targeting miRNAs to rejuvenate age-related declined thymic function.

Age and sex differences in microRNAs expression during the process of thymus aging

The gender-biased thymus involution and the importance of microRNAs (miRNAs, miRs) expression in modulating the thymus development have been reported in many studies. However, how males and females differ in so many ways in thymus involution remains unclear. To address this question, we investigated the miRNA expression profiles in both untreated 3- and 12-month-old female and male mice thymuses. The results showed that 7 and 18 miRNAs were defined as the sex- and age-specific miRNAs, respectively. The expression of miR-181c-5p, miR-20b-5p, miR-98b-5p, miR-329-3p, miR-341-5p, and miR-2137 showed significant age-difference in mice thymus by quantitative polymerase chain reaction. High expression levels of miR-2137 were detected in mice thymic epithelial cells and gradually increased during the process of thymus aging. MiR-27b-3p and miR-378a-3p of the female-biased miRNAs were confirmed as the sex- and estrogen-responsive miRNAs in mice thymus in vivo. Their potential target genes and the pathway were identified by the online software. Possible regulation roles of sex- and age-specific miRNA expression during the process of thymus aging were discussed. Our results suggested that these miRNAs may be potential biomarkers for the study of sex- and age-specific thymus aging and involution.