Mesenchymal miR-21 regulates branching morphogenesis in murine submandibular gland in vitro

The role of miR-21 as a biomarker and therapeutic target in cardiovascular disease

Cardiovascular diseases (CVDs) are the leading causes of death worldwide, accounting for a significant burden on global health systems. The complexity of CVDs arises from their multifactorial etiology, including genetic, environmental, and lifestyle factors. Early diagnosis and effective treatment remain critical for reducing mortality and improving patient outcomes, yet conventional methods often fall short in providing precise, timely information for disease management. MicroRNAs are small non-coding RNAs that regulate gene expression and play pivotal roles in various biological processes, including cardiovascular health. Among them, miR-21 has garnered significant attention due to its involvement in cardiac remodeling, fibrosis, inflammation, and hypertrophy. Elevated levels of miR-21 are frequently observed in conditions such as myocardial infarction, heart failure, and coronary artery disease, positioning it as a potential biomarker for early detection and disease progression. Furthermore, therapeutic strategies targeting miR-21, such as antagomirs and innovative delivery systems, have shown promise in preclinical studies, though challenges like off-target effects and delivery inefficiencies persist. This review aims to provide a comprehensive understanding of miR-21's role in CVDs, addressing its potential as a diagnostic biomarker and therapeutic target. We discuss recent advancements, limitations, and future prospects in miR-21 research, emphasizing the importance of integrating this knowledge into clinical practice to improve CVD management.

A microRNA Cluster-Lefty Pathway is Required for Cellulose Synthesis During Ascidian Larval Metamorphosis

Synthesis of cellulose and formation of tunic structure are unique traits in the tunicate animal group. However, the regulatory mechanism of tunic formation remains obscure. Here, we identified a novel microRNA cluster of three microRNAs, including miR4018a, miR4000f, and miR4018b in Ciona savignyi. In situ hybridization and promoter assays showed that miR4018a/4000f/4018b cluster was expressed in the mesenchymal cells in the larval trunk, and the expression levels were downregulated during the later tailbud stage and larval metamorphosis. Importantly, overexpression of miR4018a/4000f/4018b cluster in mesenchymal cells abolished the cellulose synthesis in Ciona larvae and caused the loss of tunic cells in metamorphic larvae, indicating the regulatory roles of miR4018a/4000f/4018b cluster in cellulose synthesis and mesenchymal cell differentiation into tunic cells. To elucidate the molecular mechanism, we further identified the target genes of miR4018a/4000f/4018b cluster using the combination approaches of TargetScan prediction and RNA-seq data. Left-right determination factor (Lefty) was confirmed as one of the target genes after narrow-down screening and an experimental luciferase assay. Furthermore, we showed that Lefty was expressed in the mesenchymal and tunic cells, indicating its potentially regulatory roles in mesenchymal cell differentiation and tunic formation. Notably, the defects in tunic formation and loss of tunic cells caused by overexpression of miR4018a/4000f/4018b cluster could be restored when Lefty was overexpressed in Ciona larvae, suggesting that miR4018a/4000f/4018b regulated the differentiation of mesenchymal cells into tunic cells through the Lefty signaling pathway during ascidian metamorphosis. Our findings, thus, reveal a novel microRNA-Lefty molecular pathway that regulates mesenchymal cells differentiating into tunic cells required for the tunic formation in tunicate species.

Growth factor dependence of the proliferation and survival of cultured lacrimal gland epithelial cells isolated from late-embryonic mice

Epidermal growth factor (EGF) and hepatocyte growth factor (HGF) regulate the growth and morphogenesis of various exocrine glands with branched morphologies. Their roles in lacrimal gland (LG) development remain unknown, but fibroblast growth factor (FGF) 10 is crucial for early LG organogenesis. To clarify the roles of EGF, HGF, and FGF10 in LG development, LG epithelial cells were isolated from late-embryonic and neonatal mice; cultured; and treated with EGF, HGF, or FGF10 and their respective receptor tyrosine kinase (RTK) inhibitors AG1478, PHA665752, or SU5402. EGF and HGF increased the number of viable cells by enhancing DNA synthesis, FGF10 and SU5402 showed no such effect, and RTK inhibitors exhibited the opposite effect. EGF and HGF receptors were immunostained in cultured late-embryonic LG epithelial cells and terminal LG acini from late embryos and adult mice. HGF was detected in neonatal LG epithelial cell culture supernatants by western blotting. In the absence of EGF and HGF RTK inhibitors, growth factor addition increased the number of viable cells and suppressed cell death. However, when one RTK was inhibited and a growth factor targeting an intact RTK was added, the number of dead cells increased as the number of viable cells increased. No cells survived when both RTKs were inhibited. In explant cultures of LGs from embryos, AG1478 or PHA665752 decreased the number of Ki67-positive proliferating epithelial cells in terminal acini. Thus, EGF and HGF may function in a cooperative autocrine manner, supporting cell proliferation and survival during LG development in late-embryonic and neonatal mice.

MicroRNAs as Theranostics Targets in Oral Carcinoma Stem Cells

Oral cancer belongs to head and neck squamous cell carcinoma and has been recognized as one of the most prevalent malignancies worldwide. Recent studies have suggested that cancer stem cells (CSCs) may participate in tumor initiation, metastasis and even recurrence, so the regulation of CSCs has drawn significant attention over the past decade. Among various molecules that are associated with CSCs, non-coding RNAs (ncRNAs) have been indicated as key players in the acquisition and maintenance of cancer stemness. In addition, accumulating studies have shown that the aberrant expression of these ncRNAs may serve as surrogate diagnostic markers or even therapeutic targets for cancer treatment. The current study reviews the previous work by us and others to summarize how these ncRNAs affect oral cancer stemness and their potential theranostic applications. A better understanding of the implication of these ncRNAs in oral tumorigenesis will facilitate the translation of basic ncRNA research into clinical application in the future.

Aberrant MicroRNAomics in Pulmonary Complications: Implications in Lung Health and Diseases

Over the last few decades, evolutionarily conserved molecular networks have emerged as important regulators in the expression and function of eukaryotic genomes. Recently, miRNAs (miRNAs), a large family of small, non-coding regulatory RNAs were identified in these networks as regulators of endogenous genes by exerting post-transcriptional gene regulation activity in a broad range of eukaryotic species. Dysregulation of miRNA expression correlates with aberrant gene expression and can play an essential role in human health and disease. In the context of the lung, miRNAs have been implicated in organogenesis programming, such as proliferation, differentiation, and morphogenesis. Gain- or loss-of-function studies revealed their pivotal roles as regulators of disease development, potential therapeutic candidates/targets, and clinical biomarkers. An altered microRNAome has been attributed to several pulmonary diseases, such as asthma, chronic pulmonary obstructive disease, cystic fibrosis, lung cancer, and idiopathic pulmonary fibrosis. Considering the relevant roles and functions of miRNAs under physiological and pathological conditions, they may lead to the invention of new diagnostic and therapeutic tools. This review will focus on recent advances in understanding the role of miRNAs in lung development, lung health, and diseases, while also exploring the progress and prospects of their application as therapeutic leads or as biomarkers.

A microRNA signature for the differential diagnosis of salivary gland tumors

Salivary gland tumors (SGTs) are rare tumors of the head and neck with different clinical behavior. Preoperative diagnosis, based on instrumental and cytologic examinations, is crucial for their correct management. The identification of molecular markers might improve the accuracy of pre-surgical diagnosis helping to plan the proper treatment especially when a definitive diagnosis based only on cytomorphology cannot be achieved. miRNAs appear to be new promising biomarkers in the diagnosis and prognosis of cancer. Studies concerning the useful of miRNA expression in clinical decision-making regarding SGTs remain limited and controversial.The expression of a panel of 798 miRNAs was investigated using Nanostring technology in 14 patients with malignant SGTs (6 mucoepidermoid carcinomas, 4 adenoid cystic carcinomas, 1 acinic cell carcinoma, 1 ductal carcinoma, 1 cystadenocarcinoma and 1 adenocarcinoma) and in 10 patients with benign SGTs (pleomorphic adenomas). The DNA Intelligent Analysis (DIANA)-miRPath v3.0 software was used to determinate the miRNA regulatory roles and to identify the controlled significant Kyoto Encyclopedia of Genes and Genomes (KEGG) molecular pathways. Forty six miRNAs were differentially expressed (False Discovery Rate—FDR<0.05) between malignant and benign SGTs. DIANA miRPath software revealed enriched pathways involved in cancer processes as well as tumorigenesis, cell proliferation, cell growth and survival, tumor suppressor expression, angiogenesis and tumor progression. Interestingly, clustering analysis showed that this signature of 46 miRNAs is able to differentiate the two analyzed groups. We found a correlation between histological diagnosis (benign or malignant) and miRNA expression profile.The molecular signature identified in this study might become an important preoperative diagnostic tool.

Regulatory mechanisms of branching morphogenesis in mouse submandibular gland rudiments

Branching morphogenesis is an important developmental process for many organs, including the salivary glands. Whereas epithelial–mesenchymal interactions, which are cell-to-cell communications, are known to drive branching morphogenesis, the molecular mechanisms responsible for those inductive interactions are still largely unknown. Cell growth factors and integrins are known to be regulators of branching morphogenesis of salivary glands. In addition, functional microRNAs (miRNAs) have recently been reported to be present in the developing submandibular gland. In this review, the authors describe the roles of various cell growth factors, integrins and miRNAs in branching morphogenesis of developmental mouse submandibular glands.

Exosomal microRNA communication between tissues during organogenesis

Epithelial-mesenchymal interactions are required to coordinate cell proliferation, patterning, and functional differentiation of multiple cell types in a developing organ. This exquisite coordination is dependent on various secreted molecules that provide developmental signals to mediate these tissue interactions. Recently, it was reported that mature mesenchymal-derived microRNAs (miRNAs) in the fetal mouse salivary gland are loaded into exosomes, and transported to the epithelium where they influence progenitor cell proliferation. The exosomal miRNAs regulated epithelial expression of genes involved in DNA methylation in progenitor cells to influence morphogenesis. Thus, exosomal miRNAs are mobile genetic signals that cross tissue boundaries within an organ. These findings raise many questions about how miRNA signals are initiated to coordinate organogenesis and whether they are master regulators of epithelial-mesenchymal interactions. The development of therapeutic applications using exosomal miRNAs for the regeneration of damaged adult organs is a promising area of research.

miR-205 is a critical regulator of lacrimal gland development

The tear film protects the terrestrial animal's ocular surface and the lacrimal gland provides important aqueous secretions necessary for its maintenance. Despite the importance of the lacrimal gland in ocular health, molecular aspects of its development remain poorly understood. We have identified a noncoding RNA (miR-205) as an important gene for lacrimal gland development. Mice lacking miR-205 fail to properly develop lacrimal glands, establishing this noncoding RNA as a key regulator of lacrimal gland development. Specifically, more than half of knockout lacrimal glands never initiated, suggesting a critical role of miR-205 at the earliest stages of lacrimal gland development. RNA-seq analysis uncovered several up-regulated miR-205 targets that may interfere with signaling to impair lacrimal gland initiation. Supporting this data, combinatorial epistatic deletion of Fgf10, the driver of lacrimal gland initiation, and miR-205 in mice exacerbates the lacrimal gland phenotype. We develop a molecular rheostat model where miR-205 modulates signaling pathways related to Fgf10 in order to regulate glandular development. These data show that a single microRNA is a key regulator for early lacrimal gland development in mice and highlights the important role of microRNAs during organogenesis.

Comparison of microRNA profiles between benign and malignant salivary gland tumors in tissue, blood and saliva samples: a prospective, case-control study

INTRODUCTION

Salivary gland tumors (SGTs) are rare head and neck malignancies consisting of a spectrum of tumors with different biological behaviors.

OBJECTIVE

In this study we aimed to find out differential expression of microRNA profiles between benign and malignant SGTs.

METHODS

We investigated the possible role of 95 microRNAs in the 20 patients with salivary gland tumors with comparison of 17 patients without malignancy or salivary gland diseases. Sixteen of the tumors were benign (seven pleomorphic adenomas, nine Warthin tumors), four of them were malignant (two squamous cell carcinomas, one high grade mucoepidermoid carcinoma, one adenocarcinoma). Serum and saliva samples were collected from both patients and control group. Tissue samples of tumor masses were also collected from patient group.

RESULTS

Among studied microRNAs miR-21, miR-23a, miR-27a, miR-223, miR-125b, miR-126, miR-146a, miR-30e were down regulated in the benign group compared to control group in the serum samples (p-values are 0.04, 0.00005, 0.00005, 0.0022, 0.031, 0.00008, 0.044, and 0.0007, respectively). When tissue samples were studied miR-21, miR-31, miR-199a-5p, miR-146b, miR-345 were up-regulated in the malignant group compared to benign group (p values are 0.006, 0.02, 0.013, 0.013, 0.041, respectively). miR-30e showed statistically significant up-regulation in malignant tumor group's plasma samples compared to benign group (p=0.034). There was no statistically significant difference in saliva samples between groups.

CONCLUSION

Our results showed that different microRNAs may play role in salivary tumor pathogenesis according to biological behavior. Although there was no difference in saliva samples between groups, according to tissue and serum samples miR-21 and 30e may have an important role; since they were down-regulated in benign tumors whereas up-regulated in malignant ones.

Exosomal MicroRNA Transport from Salivary Mesenchyme Regulates Epithelial Progenitor Expansion during Organogenesis

Epithelial-mesenchymal interactions involve fundamental communication between tissues during organogenesis and are primarily regulated by growth factors and extracellular matrix. It is unclear whether RNA-containing exosomes are mobile genetic signals regulating epithelial-mesenchymal interactions. Here we identify that exosomes loaded with mesenchyme-specific mature microRNA contribute mobile genetic signals from mesenchyme to epithelium. The mature mesenchymal miR-133b-3p, loaded into exosomes, was transported from mesenchyme to the salivary epithelium, which did not express primary miR-133b-3p. Knockdown of miR-133b-3p in culture decreased endbud morphogenesis, reduced proliferation of epithelial KIT⁺ progenitors, and increased expression of a target gene, Disco-interacting protein 2 homolog B (Dip2b). DIP2B, which is involved in DNA methylation, was localized with 5-methylcytosine in the prophase nucleus of a subset of KIT⁺ progenitors during mitosis. In summary, exosomal transport of miR-133b-3p from mesenchyme to epithelium decreases DIP2B, which may function as an epigenetic regulator of genes responsible for KIT⁺ progenitor expansion during organogenesis.

Shh/Ptch and EGF/ErbB cooperatively regulate branching morphogenesis of fetal mouse submandibular glands

The hedgehog family includes Sonic hedgehog (Shh), Desert hedgehog, and Indian hedgehog, which are well known as a morphogens that play many important roles during development of numerous organs such as the tongue, pancreas, kidney, cartilage, teeth and salivary glands (SMG). In Shh null mice, abnormal development of the salivary gland is seen after embryonic day 14 (E14). Shh also induced lobule formation and lumen formation in acini-like structures in cultured E14 SMG. In this study, we investigated the relationship between Shh and epidermal growth factor (EGF)/ErbB signaling in developing fetal mouse SMG. Administration of Shh to cultured E13 SMG stimulated branching morphogenesis (BrM) and induced synthesis of mRNAs for EGF ligands and receptors of the ErbB family. Shh also stimulated activation of ErbB signaling system such as ERK1/2. AG1478, a specific inhibitor of ErbB receptors, completely suppressed BrM and activation of EGF/ErbB/ERK1/2 cascade in E13 SMGs cultured with Shh. The expressions of mRNA for Egf in mesenchyme and mRNA for Erbb1, Erbb2 and Erbb3 in epithelium of E13 SMG were specifically induced by administration of Shh. These results show that Shh stimulates BrM of fetal mouse SMG, at least in part, through activation of the EGF/ErbB/ERK1/2 signaling system.

Regulatory Mechanisms Driving Salivary Gland Organogenesis

Salivary glands develop as highly branched structures designed to produce and secrete saliva. Advances in mouse genetics, stem cell biology, and regenerative medicine are having a tremendous impact on our understanding of salivary gland organogenesis. Understanding how submandibular gland (SMG) initiation, branching morphogenesis, and cell differentiation occur, as well as defining the progenitor/stem cells and cell and tissue interactions that drive SMG development will help guide regenerative approaches for patients suffering from loss of salivary gland function. This review focuses on recent literature from the past 5 years investigating the regulatory mechanisms driving SMG organogenesis.

Regulating Craniofacial Development at the 3' End: MicroRNAs and Their Function in Facial Morphogenesis

Defects in craniofacial development represent a majority of observed human birth defects, occurring at a rate as high as 1:800 live births. These defects often occur due to changes in neural crest cell (NCC) patterning and development and can affect non-NCC-derived structures due to interactions between NCCs and the surrounding cell types. Proper craniofacial development requires an intricate array of gene expression networks that are tightly controlled spatiotemporally by a number of regulatory mechanisms. One of these mechanisms involves the action of microRNAs (miRNAs), a class of noncoding RNAs that repress gene expression by binding to miRNA recognition sequences typically located in the 3' UTR of target mRNAs. Recent evidence illustrates that miRNAs are crucial for vertebrate facial morphogenesis, with changes in miRNA expression leading to facial birth defects, including some in complex human syndromes such as 22q11 (DiGeorge Syndrome). In this review, we highlight the current understanding of miRNA biogenesis, the roles of miRNAs in overall craniofacial development, the impact that loss of miRNAs has on normal development and the requirement for miRNAs in the development of specific craniofacial structures, including teeth. From these studies, it is clear that miRNAs are essential for normal facial development and morphogenesis, and a potential key in establishing new paradigms for repair and regeneration of facial defects.

Association of aging with gene expression profiling in mouse submandibular glands

Aging, also called senescence, is thought to be a physiological phenomenon that commonly occurs in various organs and tissues (Enoki et al., 2007 [1]). Many older adults experience dysfunction in their salivary glands, for example xerostomia, which is defined as dry mouth resulting from reduced or absent saliva flow (Nagler et al., 2004 [2]). In the present study, we investigated gene expression in submandibular glands of young (8 weeks old) and adult (50 weeks old) mice to analyze association of aging with gene expression profiling in mouse submandibular glands. Whole-genome gene expression profiles were analyzed using an Illumina Sentrix system with Mouse-WG-6 v.2 Expression BeadChips (Illumina). Of the genes screened, 284 showed detection values at a significance level of P < 0.01. Among those, the expression of 94 genes (33%) showed a greater decrease in adult mice as compared to young mice. On the other hand, that of 190 genes (77%) was increased in the adults more than in young mice. The data obtained in this study are publicly available in the Gene Expression Omnibus (GEO) database (accession number GSE66857).

MicroRNA-21 Regulates PI3K/Akt/mTOR Signaling by Targeting TGFβI during Skeletal Muscle Development in Pigs

MicroRNAs (miRNAs), which are short (22–24 base pairs), non-coding RNAs, play critical roles in myogenesis. Using Solexa deep sequencing, we detected the expression levels of 229 and 209 miRNAs in swine skeletal muscle at 90 days post-coitus (E90) and 100 days postnatal (D100), respectively. A total of 138 miRNAs were up-regulated on E90, and 31 were up-regulated on D100. Of these, 9 miRNAs were selected for the validation of the small RNA libraries by quantitative RT-PCR (RT-qPCR). We found that miRNA-21 was down-regulated by 17-fold on D100 (P<0.001). Bioinformatics analysis suggested that the transforming growth factor beta-induced (TGFβI) gene was a potential target of miRNA-21. Both dual luciferase reporter assays and western blotting demonstrated that the TGFβI gene was regulated by miRNA-21. Co-expression analysis revealed that the mRNA expression levels of miRNA-21 and TGFβI were negatively correlated (r = -0.421, P = 0.026) in skeletal muscle during the 28 developmental stages. Our results revealed that more miRNAs are expressed in prenatal than in postnatal skeletal muscle. The miRNA-21 is a novel myogenic miRNA that is involved in skeletal muscle development and regulates PI3K/Akt/mTOR signaling by targeting the TGFβI gene.

miR-21 promotes the differentiation of hair follicle-derived neural crest stem cells into Schwann cells

Hair follicle-derived neural crest stem cells can be induced to differentiate into Schwann cells in vivo and in vitro. However, the underlying regulatory mechanism during cell differentiation remains poorly understood. This study isolated neural crest stem cells from human hair follicles and induced them to differentiate into Schwann cells. Quantitative RT-PCR showed that microRNA (miR)-21 expression was gradually increased during the differentiation of neural crest stem cells into Schwann cells. After transfection with the miR-21 agonist (agomir-21), the differentiation capacity of neural crest stem cells was enhanced. By contrast, after transfection with the miR-21 antagonist (antagomir-21), the differentiation capacity was attenuated. Further study results showed that SOX-2 was an effective target of miR-21. Without compromising SOX2 mRNA expression, miR-21 can down-regulate SOX protein expression by binding to the 3′-UTR of miR-21 mRNA. Knocking out the SOX2 gene from the neural crest stem cells significantly reversed the antagomir-21 inhibition of neural crest stem cells differentiating into Schwann cells. The results suggest that miR-21 expression was increased during the differentiation of neural crest stem cells into Schwann cells and miR-21 promoted the differentiation through down-regulating SOX protein expression by binding to the 3′-UTR of SOX2 mRNA.

Cellular and physical mechanisms of branching morphogenesis

Branching morphogenesis is the developmental program that builds the ramified epithelial trees of various organs, including the airways of the lung, the collecting ducts of the kidney, and the ducts of the mammary and salivary glands. Even though the final geometries of epithelial trees are distinct, the molecular signaling pathways that control branching morphogenesis appear to be conserved across organs and species. However, despite this molecular homology, recent advances in cell lineage analysis and real-time imaging have uncovered surprising differences in the mechanisms that build these diverse tissues. Here, we review these studies and discuss the cellular and physical mechanisms that can contribute to branching morphogenesis.

MicroRNA profiles discriminate among colon cancer metastasis

MicroRNAs are being exploited for diagnosis, prognosis and monitoring of cancer and other diseases. Their high tissue specificity and critical role in oncogenesis provide new biomarkers for the diagnosis and classification of cancer as well as predicting patients' outcomes. MicroRNAs signatures have been identified for many human tumors, including colorectal cancer (CRC). In most cases, metastatic disease is difficult to predict and to prevent with adequate therapies. The aim of our study was to identify a microRNA signature for metastatic CRC that could predict and differentiate metastatic target organ localization. Normal and cancer tissues of three different groups of CRC patients were analyzed. RNA microarray and TaqMan Array analysis were performed on 66 Italian patients with or without lymph nodes and/or liver recurrences. Data obtained with the two assays were analyzed separately and then intersected to identify a primary CRC metastatic signature. Five differentially expressed microRNAs (hsa-miR-21, -103, -93, -31 and -566) were validated by qRT-PCR on a second group of 16 American metastatic patients. In situ hybridization was performed on the 16 American patients as well as on three distinct commercial tissues microarray (TMA) containing normal adjacent colon, the primary adenocarcinoma, normal and metastatic lymph nodes and liver. Hsa-miRNA-21, -93, and -103 upregulation together with hsa-miR-566 downregulation defined the CRC metastatic signature, while in situ hybridization data identified a lymphonodal invasion profile. We provided the first microRNAs signature that could discriminate between colorectal recurrences to lymph nodes and liver and between colorectal liver metastasis and primary hepatic tumor.

MicroRNA expression patterns associated with hyperfunctioning and non-hyperfunctioning phenotypes in adrenocortical adenomas

BACKGROUND

The adrenocortical adenoma (ACA) entity includes aldosterone-producing adenoma (APA), cortisol-producing adenoma (CPA), and non-hyperfunctioning adenoma (NHFA) phenotypes. While gene mutations and mRNA expression profiles have been partly characterized, less is known about the alterations involving microRNA (miRNA) expression.

AIM

To characterize miRNA expression profile in relation to the subtypes of ACAs.

SUBJECTS AND METHODS

miRNA expression profiles were determined in 26 ACAs (nine APAs, ten CPAs, and seven NHFAs) and four adrenal references using microarray-based screening. Significance analysis of microarrays (SAM) was carried out to identify differentially expressed miRNAs between ACA and adrenal cortices or between tumor subtypes. Selected differentially expressed miRNAs were validated in an extended series of 43 ACAs and ten adrenal references by quantitative RT-PCR.

RESULTS

An hierarchical clustering revealed separate clusters for APAs and CPAs, while the NHFAs were found spread out within the APA/CPA clusters. When NHFA was excluded, the clustering analysis showed a better separation between APA and CPA. SAM analysis identified 40 over-expressed and three under-expressed miRNAs in the adenomas as compared with adrenal references. Fourteen miRNAs were common among the three ACA subtypes. Furthermore, we found specific miRNAs associated with different tumor phenotypes.

CONCLUSION

The results suggest that miRNA expression profiles can distinguish different subtypes of ACA, which may contribute to a deeper understanding of ACA development and potential therapeutics.

Salivary gland development: a template for regeneration

The mammalian salivary gland develops as a highly branched structure designed to produce and secrete saliva. This review will focus on research on mouse submandibular gland development and the translation of this basic research toward therapy for patients suffering from salivary hypofunction. Here we review the most recent literature that has enabled a better understanding of the mechanisms of salivary gland development. Additionally, we discuss approaches proposed to restore salivary function using gene and cell-based therapy. Increasing our understanding of the developmental mechanisms involved during development is critical to design effective therapies for regeneration and repair of damaged glands.

miR-21 promotes fibrogenic epithelial-to-mesenchymal transition of epicardial mesothelial cells involving Programmed Cell Death 4 and Sprouty-1

The lining of the adult heart contains epicardial mesothelial cells (EMCs) that have the potential to undergo fibrogenic Epithelial-to-Mesenchymal Transition (EMT) during cardiac injury. EMT of EMCs has therefore been suggested to contribute to the heterogeneous fibroblast pool that mediates cardiac fibrosis. However, the molecular basis of this process is poorly understood. Recently, microRNAs (miRNAs) have been shown to regulate a number of sub-cellular events in cardiac disease. Hence, we hypothesized that miRNAs regulate fibrogenic EMT in the adult heart. Indeed pro-fibrogenic stimuli, especially TGF-β, promoted EMT progression in EMC cultures, which resulted in differential expression of numerous miRNAs, especially the pleiotropic miR-21. Accordingly, ectopic expression of miR-21 substantially promoted the fibroblast-like phenotype arising from fibrogenic EMT, whereas an antagonist that targeted miR-21 blocked this effect, as assessed on the E-cadherin/α-smooth muscle actin balance, cell viability, matrix activity, and cell motility, thus making miR-21 a relevant target of EMC-derived fibrosis. Several mRNA targets of miR-21 was differentially regulated during fibrogenic EMT of EMCs and miR-21-dependent targeting of Programmed Cell Death 4 (PDCD4) and Sprouty Homolog 1 (SPRY1) significantly contributed to the development of a fibroblastoid phenotype. However, PDCD4- and SPRY1-targeting was not entirely ascribable to all phenotypic effects from miR-21, underscoring the pleiotropic biological role of miR-21 and the increasing number of recognized miR-21 targets.

High expression of microRNA‑127 is involved in cell cycle arrest in MC‑3 mucoepidermoid carcinoma cells

microRNAs (miRs) are small endogenous non‑coding RNAs and are associated with the pathogenesis of a number of types of human cancer. However, miR‑127‑3p in mucoepidermoid carcinoma (MEC) has not been studied. The present study aimed to analyze the importance of miR‑127‑3p in MC‑3 human MEC cells. Analyses of the growth inhibitory effect and the associated mechanism of miR‑127‑3p were performed using 3‑(4,5‑dimethylthiazol‑20yl)‑(3‑carboxymethoxyphenyl)‑2‑(4‑sulphophenyl)‑2H‑tetrazolium assay, flow cytometry, 4'‑6‑diamidino‑2‑phenylindole staining, anchorage‑independent cell transformation assay and western blot analysis. Transfection of exogenous miR‑127‑3p into MC‑3 cells inhibited cell viability and led to G1/S cell cycle arrest. In addition, miR‑127‑3p also decreased neoplastic cell transformation in TPA‑induced JB6 mouse epidermal and MC‑3 cells. In addition, miR‑127‑3p decreased specificity protein 1 (Sp1) expression and increased p21 and p27 expression which are Sp1‑dependent cell cycle‑related proteins. However, miR‑127‑3p did not induce apoptosis or affect expression levels of myeloid cell leukemia‑1 or survivin. miR‑127‑3p induced G1/S cell cycle arrest and increased p21 and p27 expression via modulation of Sp1. Therefore, miR‑127‑3p may be a therapeutic target for human MEC.

OxymiRs in cutaneous development, wound repair and regeneration

The state of tissue oxygenation is widely recognized as a major microenvironmental cue that is known to regulate the expression of coding genes. Recent works have extended that knowledge to demonstrate that the state of tissue oxygenation may potently regulate the expression of microRNAs (miRs). Collectively, such miRs that are implicated in defining biological outcomes in response to a change in the state of tissue oxygenation may be referred to as oxymiRs. Broadly, oxymiRs may be categorized into three groups: (A) the existence (expression and/or turnover) of which is directly influenced by changes in the state of tissue oxygenation; (B) the existence of which is indirectly (e.g. oxygen-sensitive proteins, metabolites, pH, etc.) influenced by changes in the state of tissue oxygenation; and (C) those that modify biological outcomes to changes in the state of tissue oxygenation by targeting oxygen sensing pathways. This work represents the first review of how oxymiRs may regulate development, repair and regeneration. Currently known oxymiRs may affect the functioning of a large number of coding genes which have hitherto fore never been linked to oxygen sensing. Many of such target genes have been validated and that number is steadily growing. Taken together, our understanding of oxymiRs has vastly expanded the implications of changes in the state of tissue oxygenation. This emerging paradigm has major implications in untangling the complexities underlying diseases associated with ischemia and related hypoxic insult such as chronic wounds.

Transcriptional regulation of the protocadherin β cluster during Her-2 protein-induced mammary tumorigenesis results from altered N-glycan branching

Changes in the levels of N-acetylglucosaminyltransferase V (GnT-V) can alter the function of several types of cell surface receptors and adhesion molecules by causing altered N-linked glycan branching. Using a her-2 mammary tumor mouse model, her-2 receptor signaling was down-regulated by GnT-V knock-out, resulting in a significant delay in the onset of her-2-induced mammary tumors. To identify the genes that contributed to this GnT-V regulation of early events in tumorigenesis, microarray analysis was performed using her-2 induced mammary tumors from wild-type and GnT-V-null mice. We found that 142 genes were aberrantly expressed (>2.0-fold) with 64 genes up-regulated and 78 genes down-regulated after deletion of GnT-V. Among differentially expressed genes, the expression of a subgroup of the cadherin superfamily, the protocadherin β (Pcdhβ) cluster, was up-regulated in GnT-V-null tumors. Altered expression of the Pcdhβ cluster in GnT-V-null tumors was not due to changes in promoter methylation; instead, impaired her-2-mediated signaling pathways were implicated at least in part resulting from reduced microRNA-21 expression. Overexpression of Pcdhβ genes inhibited tumor cell growth, decreased the proportion of tumor-initiating cells, and decreased tumor formation in vivo, demonstrating that expression of the Pcdhβ gene cluster can serve as an inhibitor of the transformed phenotype. Our results suggest the up-regulation of the Pcdhβ gene cluster as a mechanism for reduced her-2-mediated tumorigenesis resulting from GnT-V deletion.

miR-200c regulates FGFR-dependent epithelial proliferation via Vldlr during submandibular gland branching morphogenesis

The regulation of epithelial proliferation during organ morphogenesis is crucial for normal development, as dysregulation is associated with tumor formation. Non-coding microRNAs (miRNAs), such as miR-200c, are post-transcriptional regulators of genes involved in cancer. However, the role of miR-200c during normal development is unknown. We screened miRNAs expressed in the mouse developing submandibular gland (SMG) and found that miR-200c accumulates in the epithelial end buds. Using both loss- and gain-of-function, we demonstrated that miR-200c reduces epithelial proliferation during SMG morphogenesis. To identify the mechanism, we predicted miR-200c target genes and confirmed their expression during SMG development. We discovered that miR-200c targets the very low density lipoprotein receptor (Vldlr) and its ligand reelin, which unexpectedly regulate FGFR-dependent epithelial proliferation. Thus, we demonstrate that miR-200c influences FGFR-mediated epithelial proliferation during branching morphogenesis via a Vldlr-dependent mechanism. miR-200c and Vldlr may be novel targets for controlling epithelial morphogenesis during glandular repair or regeneration.

Salivary gland organogenesis

Our understanding of vertebrate salivary gland organogenesis has been largely informed by the study of the developing mouse submandibular gland (SMG), which will be the major focus of this review. The mouse SMG has been historically used as a model system to study epithelial-mesenchymal interactions, growth factor-extracellular matrix (ECM) interactions, and branching morphogenesis. SMG organogenesis involves interactions between a variety of cell types and their stem/progenitor cells, including the epithelial, neuronal, and mesenchymal cells, and their ECM microenvironment, or niche. Here, we will review recent literature that provides conceptual advances in understanding the molecular mechanisms of salivary gland development. We will describe SMG organogenesis, introduce the model systems used to study development, and outline the key signaling pathways and cellular processes involved. We will also review recent research focusing on the identification of stem/progenitor cells in the SMG and how they are directed along a series of cell fate decisions to form a functional gland. The mechanisms that drive SMG organogenesis provide a template to regenerate functional salivary glands in patients who suffer from salivary hypofunction due to irreversible glandular damage after irradiation or removal of tumors. Additionally, these mechanisms may also control growth and development of other organ systems.

Regulation and function of miRNA-21 in health and disease

The small regulatory RNA microRNA-21 (miR-21) plays a crucial role in a plethora of biological functions and diseases including development, cancer, cardiovascular diseases and inflammation. The gene coding for pri-miR-21 (primary transcript containing miR-21) is located within the intronic region of the TMEM49 gene. Despite pri-miR-21 and TMEM49 are overlapping genes in the same direction of transcription, pri-miR-21 is independently transcribed by its own promoter regions and terminated with its own poly(A) tail. After transcription, primiR- 21 is finally processed into mature miR-21. Expression of miR-21 has been found to be deregulated in almost all types of cancers and therefore was classified as an oncomiR. During recent years, additional roles of miR-21 in cardiovascular and pulmonary diseases, including cardiac and pulmonary fibrosis as well as myocardial infarction have been described. MiR-21 additionally regulates various immunological and developmental processes. Due to the critical functions of its target proteins in various signaling pathways, miR-21 has become an attractive target for genetic and pharmacological modulation in various disease conditions.