Precise let-7 expression levels balance organ regeneration against tumor suppression

Cell-specific Extracellular Vesicles and Their miRNA Cargo Released Into the Organ Preservation Solution During Cold Ischemia Storage as Biomarkers for Liver Transplant Outcomes

BACKGROUND

Liver transplantation (LT) is crucial for end-stage liver disease patients, but organ shortages persist. Donation after circulatory death (DCD) aims to broaden the donor pool but presents challenges. Complications like acute rejection, hepatic artery thrombosis, and biliary issues still impact posttransplant prognosis. Biomarkers, including extracellular vesicles (EVs) and microRNAs (miRNAs), show promise in understanding and monitoring posttransplant events. This study explores the role of EVs and their miRNA cargo in LT, including their potential as diagnostic tools.

METHODS

EVs from intrahepatic end-ischemic organ preservation solution (eiOPS) in 79 donated livers were detected using different techniques (nanosight tracking analysis, transmission electron microscopy, and flow cytometry). EV-derived miRNAs were identified by quantitative real time-polymerase chain reaction. Bioinformatics analysis was performed using the R platform.

RESULTS

Different-sized and origin-specific EVs were found in eiOPS, with significantly higher concentrations in DCD compared with donation after brain death organs. Additionally, several EV-associated miRNAs, including let-7d-5p , miR-28-5p , miR-200a-3p , miR-200b-3p , miR-200c-3p , and miR-429 , were overexpressed in DCD-derived eiOPS. These miRNAs also exhibited differential expression patterns in liver tissue biopsies. Pathway analysis revealed enrichment in signaling pathways involved in extracellular matrix organization and various cellular processes. Moreover, specific EVs and miRNAs correlated with clinical outcomes, including survival and early allograft dysfunction. A predictive model combining biomarkers and clinical variables showed promise in acute rejection detection after LT.

CONCLUSIONS

These findings provide new insights into the use of EVs and miRNAs as biomarkers and their possible influence on posttransplantation outcomes, potentially contributing to improved diagnostic approaches and personalized treatment strategies in LT.

A Novel Role for the Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Delta Isoform in Hepatocellular Proliferation

The phosphatidylinositol-4,5-bisphosphate 3-kinase delta isoform (Pik3cd), usually considered immune-specific, was unexpectedly identified as a gene potentially related to either regeneration and/or differentiation in animals lacking hepatocellular Integrin Linked Kinase (ILK). Since a specific inhibitor (Idelalisib, or CAL101) for the catalytic subunit encoded by Pik3cd (p110δ) has reported hepatotoxicity when used for treating chronic lymphocytic leukemia and other lymphomas, the authors aimed to elucidate whether there is a role for p110δ in normal liver function. To determine the effect on normal liver regeneration, partial hepatectomy (PHx) was performed using mice in which p110δ was first inhibited using CAL101. Inhibition led to over a 50% decrease in proliferating hepatocytes in the first 2 days after PHx. This difference correlated with phosphorylation changes in the HGF and EGF receptors (MET and EGFR, respectively) and NF-κB signaling. Ingenuity Pathway Analyses implicated C/EBPβ, HGF, and the EGFR heterodimeric partner, ERBB2, as three of the top 20 regulators downstream of p110δ signaling because their pathways were suppressed in the presence of CAL101 at 1 day post-PHx. A regulatory role for p110δ signaling in mouse and rat hepatocytes through MET and EGFR was further verified using hepatocyte primary cultures, in the presence or absence of CAL101. Combined, these data support a role for p110δ as a downstream regulator of normal hepatocytes when stimulated to proliferate.

Engineered extracellular vesicles carrying let-7a-5p for alleviating inflammation in acute lung injury

BACKGROUND

Acute lung injury (ALI) is a life-threatening respiratory condition characterized by severe inflammation and lung tissue damage, frequently causing rapid respiratory failure and long-term complications. The microRNA let-7a-5p is involved in the progression of lung injury, inflammation, and fibrosis by regulating immune cell activation and cytokine production. This study aims to use an innovative cellular electroporation platform to generate extracellular vesicles (EVs) carring let-7a-5p (EV-let-7a-5p) derived from transfected Wharton's jelly-mesenchymal stem cells (WJ-MSCs) as a potential gene therapy for ALI.

METHODS

A cellular nanoporation (CNP) method was used to induce the production and release of EV-let-7a-5p from WJ-MSCs transfected with the relevant plasmid DNA. EV-let-7a-5p in the conditioned medium were isolated using a tangential flow filtration (TFF) system. EV characterization followed the minimal consensus guidelines outlined by the International Society for Extracellular Vesicles. We conducted a thorough set of therapeutic assessments, including the antifibrotic effects using a transforming growth factor beta (TGF-β)-induced cell model, the modulation effects on macrophage polarization, and the influence of EV-let-7a-5p in a rat model of hyperoxia-induced ALI.

RESULTS

The CNP platform significantly increased EV secretion from transfected WJ-MSCs, and the encapsulated let-7a-5p in engineered EVs was markedly higher than that in untreated WJ-MSCs. These EV-let-7a-5p did not influence cell proliferation and effectively mitigated the TGF-β-induced fibrotic phenotype by downregulating SMAD2/3 phosphorylation in LL29 cells. Furthermore, EV-let-7a-5p regulated M2-like macrophage activation in an inflammatory microenvironment and significantly induced interleukin (IL)-10 secretion, demonstrating their modulatory effect on inflammation. Administering EVs from untreated WJ-MSCs slightly improved lung function and increased let-7a-5p expression in plasma in the hyperoxia-induced ALI rat model. In comparison, EV-let-7a-5p significantly reduced macrophage infiltration and collagen deposition while increasing IL-10 expression, causing a substantial improvement in lung function.

CONCLUSION

This study reveals that the use of the CNP platform to stimulate and transfect WJ-MSCs could generate an abundance of let-7a-5p-enriched EVs, which underscores the therapeutic potential in countering inflammatory responses, fibrotic activation, and hyperoxia-induced lung injury. These results provide potential avenues for developing innovative therapeutic approaches for more effective interventions in ALI.

A glimpse into let-7e roles in human disorders; friend or foe?

MicroRNAs (miRNAs) have been linked to abnormal expression and regulation in a number of diseases, including cancer. Recent studies have concentrated on miRNA Let-7e's significance in precision medicine for cancer screening and diagnosis as well as its prognostic and therapeutic potential. Differential let-7e levels in bodily fluids have the possibility to enable early detection of cancer utilizing less-invasive techniques, reducing biopsy-related risks. Although Let-7e miRNAs have been described as tumor suppressors, it is crucial to note that there exists proof to support their oncogenic activity in vitro and in in vivo. Let-7e's significance in chemo- and radiation treatment decisions has also been demonstrated. Let-7e can also prevent the synthesis of proinflammatory cytokines in a number of degenerative disorders, including musculoskeletal and neurological conditions. For the first time, an overview of the significance of let-7e in the prevention, detection, and therapy of cancer and other conditions has been given in the current review. Additionally, we focused on the specific molecular processes that underlie the actions of let-7e, more particularly, on malignant cells.

Pharmacological inhibition of Lin28 promotes ketogenesis and restores lipid homeostasis in models of non-alcoholic fatty liver disease

Lin28 RNA-binding proteins are stem-cell factors that play key roles in development. Lin28 suppresses the biogenesis of let-7 microRNAs and regulates mRNA translation. Notably, let-7 inhibits Lin28, establishing a double-negative feedback loop. The Lin28/let-7 axis resides at the interface of metabolic reprogramming and oncogenesis and is therefore a potential target for several diseases. In this study, we use compound-C1632, a drug-like Lin28 inhibitor, and show that the Lin28/let-7 axis regulates the balance between ketogenesis and lipogenesis in liver cells. Hence, Lin28 inhibition activates synthesis and secretion of ketone bodies whilst suppressing lipogenesis. This occurs at least partly via let-7-mediated inhibition of nuclear receptor co-repressor 1, which releases ketogenesis gene expression mediated by peroxisome proliferator-activated receptor-alpha. In this way, small-molecule Lin28 inhibition protects against lipid accumulation in multiple cellular and male mouse models of hepatic steatosis. Overall, this study highlights Lin28 inhibitors as candidates for the treatment of hepatic disorders of abnormal lipid deposition.

Lipid Nanoparticle (LNP) Chemistry Can Endow Unique In Vivo RNA Delivery Fates within the Liver That Alter Therapeutic Outcomes in a Cancer Model

Within the field of lipid nanoparticles (LNPs) for RNA delivery, the focus has been mainly placed on organ level delivery, which can mask cellular level effects consequential to therapeutic applications. Here, we studied a pair of LNPs with similar physical properties and discovered how the chemistry of the ionizable amino lipid can control the endogenous LNP identity, affecting cellular uptake in the liver and altering therapeutic outcomes in a model of liver cancer. Although most LNPs accumulate in the liver after intravenous administration (suggesting that liver delivery is straightforward), we observed an unexpected behavior when comparing two similar LNP formulations (5A2-SC8 and 3A5-SC14 LNPs) that resulted in distinct RNA delivery within the organ. Despite both LNPs possessing similar physical properties, ability to silence gene expression in vitro, strong accumulation within the liver, and a shared pKa of 6.5, only 5A2-SC8 LNPs were able to functionally deliver RNA to hepatocytes. Factor VII (FVII) activity was reduced by 87%, with 5A2-SC8 LNPs carrying FVII siRNA (siFVII), while 3A5-SC14 LNPs carrying siFVII produced baseline FVII activity levels comparable to the nontreatment control at a dosage of 0.5 mg/kg. Protein corona analysis indicated that 5A2-SC8 LNPs bind apolipoprotein E (ApoE), which can drive LDL-R receptor-mediated endocytosis in hepatocytes. In contrast, the surface of 3A5-SC14 LNPs was enriched in albumin but depleted in ApoE, which likely led to Kupffer cell delivery and detargeting of hepatocytes. In an aggressive MYC-driven liver cancer model relevant to hepatocytes, 5A2-SC8 LNPs carrying let-7g miRNA were able to significantly extend survival up to 121 days. Since disease targets exist in an organ- and cell-specific manner, the clinical development of RNA LNP therapeutics will require an improved understanding of LNP cellular tropism within organs. The results from our work illustrate the importance of understanding the cellular localization of RNA delivery and incorporating further checkpoints when choosing nanoparticles beyond biochemical and physical characterization, as small changes in the chemical composition of LNPs can have an impact on both the biofate of LNPs and therapeutic outcomes.

Let-7 as a Promising Target in Aging and Aging-Related Diseases: A Promise or a Pledge

The abnormal regulation and expression of microRNA (miRNA) are closely related to the aging process and the occurrence and development of aging-related diseases. Lethal-7 (let-7) was discovered in Caenorhabditis elegans (C. elegans) and plays an important role in development by regulating cell fate regulators. Accumulating evidence has shown that let-7 is elevated in aging tissues and participates in multiple pathways that regulate the aging process, including affecting tissue stem cell function, body metabolism, and various aging-related diseases (ARDs). Moreover, recent studies have found that let-7 plays an important role in the senescence of B cells, suggesting that let-7 may also participate in the aging process by regulating immune function. Therefore, these studies show the diversity and complexity of let-7 expression and regulatory functions during aging. In this review, we provide a detailed overview of let-7 expression regulation as well as its role in different tissue aging and aging-related diseases, which may provide new ideas for enriching the complex expression regulation mechanism and pathobiological function of let-7 in aging and related diseases and ultimately provide help for the development of new therapeutic strategies.

Tumor-targeted miRNA nanomedicine for overcoming challenges in immunity and therapeutic resistance

miRNA are critical messengers in the tumor microenvironment (TME) that influence various processes leading to immune suppression, tumor progression, metastasis and resistance. Strategies to modulate miRNAs in the TME have important implications in overcoming these challenges. However, miR delivery to specific cells in the TME has been challenging. This review discusses nanomedicine strategies to achieve cell-specific delivery of miRNAs. The key goal of delivery is to activate the tumor immune landscape as well as to prevent chemotherapy resistance. Specifically, the use of hyaluronic acid-based nanoparticle miRNA delivery to the TME is discussed. The discussion is focused on miRNA-125b for reprogramming tumor-associated macrophages to overcome immunosuppression and miRNA-let-7b to overcome resistance to anticancer chemotherapeutics because both these miRNAs have been extensively evaluated for delivery with hyaluronic acid-based delivery systems.

Let-7 underlies metformin-induced inhibition of hepatic glucose production

SignificanceA clear mechanistic understanding of metformin's antidiabetic effects is lacking. This is because suprapharmacological concentrations of metformin have been used in most studies. Using mouse models and human primary hepatocytes, we show that metformin, at clinically relevant doses, suppresses hepatic glucose production by activating a conserved regulatory pathway encompassing let-7, TET3, and a fetal isoform of hepatocyte nuclear factor 4 alpha (HNF4α). We demonstrate that metformin no longer has potent antidiabetic actions in a liver-specific let-7 loss-of-function mouse model and that hepatic delivery of let-7 ameliorates hyperglycemia and improves glucose homeostasis. Our results thus reveal an important role of the hepatic let-7/TET3/HNF4α axis in mediating the therapeutic effects of metformin and suggest that targeting this axis may be a potential therapeutic for diabetes.

Non-microRNA binding competitively inhibits LIN28 regulation

RNA binding protein (RBP) expression is finite. For RBPs that are vastly outnumbered by their potential target sites, a simple competition for binding can set the magnitude of post-transcriptional control. Here, we show that LIN28, best known for its direct regulation of let-7 miRNA biogenesis, is also indirectly regulated by its widespread binding of non-miRNA transcripts. Approximately 99% of LIN28 binding sites are found on non-miRNA transcripts, like protein coding and ribosomal RNAs. These sites are bound specifically and strongly, but they do not appear to mediate direct post-transcriptional regulation. Instead, non-miRNA sites act to sequester LIN28 protein and effectively change its functional availability, thus impeding the regulation of let-7 in cells. Together, these data show that the binding properties of the transcriptome broadly influence the ability of an RBP to mediate changes in RNA metabolism and gene expression.

MicroRNA Let-7 targets AMPK and impairs hepatic lipid metabolism in offspring of maternal obese pregnancies

Nutritional status during gestation may lead to a phenomenon known as metabolic programming, which can be triggered by epigenetic mechanisms. The Let-7 family of microRNAs were one of the first to be discovered, and are closely related to metabolic processes. Bioinformatic analysis revealed that Prkaa2, the gene that encodes AMPK α2, is a predicted target of Let-7. Here we aimed to investigate whether Let-7 has a role in AMPKα2 levels in the NAFLD development in the offspring programmed by maternal obesity. Let-7 levels were upregulated in the liver of newborn mice from obese dams, while the levels of Prkaa2 were downregulated. Let-7 levels strongly correlated with serum glucose, insulin and NEFA, and in vitro treatment of AML12 with glucose and NEFA lead to higher Let-7 expression. Transfection of Let-7a mimic lead to downregulation of AMPKα2 levels, while the transfection with Let-7a inhibitor impaired both NEFA-mediated reduction of Prkaa2 levels and the fat accumulation driven by NEFA. The transfection of Let-7a inhibitor in ex-vivo liver slices from the offspring of obese dams restored phospho-AMPKα2 levels. In summary, Let-7a appears to regulate hepatic AMPKα2 protein levels and lead to the early hepatic metabolic disturbances in the offspring of obese dams.

Functional Characterization of the Lin28/let-7 Circuit During Forelimb Regeneration in Ambystoma mexicanum and Its Influence on Metabolic Reprogramming

The axolotl (Ambystoma mexicanum) is a caudate amphibian, which has an extraordinary ability to restore a wide variety of damaged structures by a process denominated epimorphosis. While the origin and potentiality of progenitor cells that take part during epimorphic regeneration are known to some extent, the metabolic changes experienced and their associated implications, remain unexplored. However, a circuit with a potential role as a modulator of cellular metabolism along regeneration is that formed by Lin28/let-7. In this study, we report two Lin28 paralogs and eight mature let-7 microRNAs encoded in the axolotl genome. Particularly, in the proliferative blastema stage amxLin28B is more abundant in the nuclei of blastemal cells, while the microRNAs amx-let-7c and amx-let-7a are most downregulated. Functional inhibition of Lin28 factors increase the levels of most mature let-7 microRNAs, consistent with an increment of intermediary metabolites of the Krebs cycle, and phenotypic alterations in the outgrowth of the blastema. In summary, we describe the primary components of the Lin28/let-7 circuit and their function during axolotl regeneration, acting upstream of metabolic reprogramming events.

Targeting miRNAs by natural products: A new way for cancer therapy

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression through mRNA degradation or translation inhibition. MiRNAs play important roles in a variety of biological processes, and dysregulation of miRNA expression is highly associated with cancer development. Individual miRNA regulates multiple gene expressions, enabling them to regulate multiple cellular signaling pathways simultaneously. Hence, miRNAs could be served as cancer biomarkers for diagnosis and prognosis, and also therapeutic targets. Recently, more and more evidences showed that natural products such as paclitaxel, curcumin, resveratrol, genistein or epigallocatechin-3-gallate exert their anti-proliferative and/or pro-apoptotic effects through regulating one or more miRNAs, leading to the inhibition of cancer cell growth, induction of apoptosis or enhancement of conventional cancer therapeutic efficacy. Herein, we outlined the recent advances in the regulation of miRNAs expression by the natural products and highlight the importance of these natural drugs as a potential strategy in cancer treatment. This review will help us better understand how natural products modulate miRNAs and contribute to the development of effective and safe natural drugs for therapeutic purposes.

MicroRNAs and long non-coding RNAs in liver surgery: Diagnostic and therapeutic merits

BACKGROUND

Hepatectomy and liver transplantation (LT) are the two most commonly performed surgical procedures for various hepatic lesions. microRNA (miRNA) and long non-coding RNA (lncRNA) have been gradually unveiled their roles as either biomarkers for early diagnosis or potentially therapeutic tools to manipulate gene expression in many disease entities. This review aimed to discuss the effects of miRNA or lncRNA in the hepatectomy and LT fields.

DATA SOURCES

We did a literature search from 1990 through January 2018 to summarize the currently available evidence with respect to the effects of miRNA and lncRNA in liver regeneration after partial hepatectomy, as well as their involvement in several key issues related to LT, including ischemia-reperfusion injury, allograft rejection, tolerance, recurrence of original hepatic malignancies, etc. RESULTS: Certain miRNAs and lncRNAs are actively involved in the regulation of various aspects of liver resection and transplantation. During the process of liver regeneration after hepatectomy, the expression of miRNAs and lncRNAs shows dynamic changes.

CONCLUSIONS

It is now clear that miRNAs and lncRNAs orchestrate in various aspects of the pathophysiological process of LT and hepatectomy. Better understanding of the underlying mechanism and future clinical trials may strengthen their positions as either biomarkers or potential therapeutic targets in the management of complications after liver surgery.

Let-7 miRNA's Expression Profile and Its Potential Prognostic Role in Uterine Leiomyosarcoma

The lethal-7 (let-7) family is an important microRNA (miRNA) group that usually exerts functions as a tumor suppressor. We aimed to evaluate the expression profile of let-7a, let-7b, let-7c, let-7d, let-7e, let-7f, let-7g, and let-7i and to assess their value as prognostic markers in uterine leiomyosarcoma (LMS) patients. The miRNAs expression profile was assessed in 34 LMS and 13 normal myometrium (MM) paraffin-embedded samples. All let-7 family members showed downregulation in LMS. Our findings showed that patients with let-7e downregulation had worse overall survival (OS) and is an independent prognostic factor (hazard ratio [HR] = 2.24). In addition, almost half the patients had distant metastasis. LMS patients with downregulated let-7b and let-7d had worse disease-free survival (DFS); they are not independent prognostic factors (HR = 2.65). Patients’ ages were associated with let-7d, let-7e and let-7f (p = 0.0160) downregulation. In conclusion, all the let-7 family members were downregulated in LMS patients, and the greater the loss of expression of these molecules, the greater their relationship with worse prognosis of patients. Let-7e expression might influence the OS, while let-7b and le-7d might influence the DFS. The lowest expression levels of let-7d, let-7e, and let-7f were associated with the oldest patients. Our findings indicate strong evidence of let-7’s role as a potential prognostic biomarker in LMS.

Non-Coding RNAs in Pediatric Solid Tumors

Pediatric solid tumors are a diverse group of extracranial solid tumors representing approximately 40% of childhood cancers. Pediatric solid tumors are believed to arise as a result of disruptions in the developmental process of precursor cells which lead them to accumulate cancerous phenotypes. In contrast to many adult tumors, pediatric tumors typically feature a low number of genetic mutations in protein-coding genes which could explain the emergence of these phenotypes. It is likely that oncogenesis occurs after a failure at many different levels of regulation. Non-coding RNAs (ncRNAs) comprise a group of functional RNA molecules that lack protein coding potential but are essential in the regulation and maintenance of many epigenetic and post-translational mechanisms. Indeed, research has accumulated a large body of evidence implicating many ncRNAs in the regulation of well-established oncogenic networks. In this review we cover a range of extracranial solid tumors which represent some of the rarer and enigmatic childhood cancers known. We focus on two major classes of ncRNAs, microRNAs and long non-coding RNAs, which are likely to play a key role in the development of these cancers and emphasize their functional contributions and molecular interactions during tumor formation.

Roles of mTOR Signaling in Tissue Regeneration

The mammalian target of rapamycin (mTOR), is a serine/threonine protein kinase and belongs to the phosphatidylinositol 3-kinase (PI3K)-related kinase (PIKK) family. mTOR interacts with other subunits to form two distinct complexes, mTORC1 and mTORC2. mTORC1 coordinates cell growth and metabolism in response to environmental input, including growth factors, amino acid, energy and stress. mTORC2 mainly controls cell survival and migration through phosphorylating glucocorticoid-regulated kinase (SGK), protein kinase B (Akt), and protein kinase C (PKC) kinase families. The dysregulation of mTOR is involved in human diseases including cancer, cardiovascular diseases, neurodegenerative diseases, and epilepsy. Tissue damage caused by trauma, diseases or aging disrupt the tissue functions. Tissue regeneration after injuries is of significance for recovering the tissue homeostasis and functions. Mammals have very limited regenerative capacity in multiple tissues and organs, such as the heart and central nervous system (CNS). Thereby, understanding the mechanisms underlying tissue regeneration is crucial for tissue repair and regenerative medicine. mTOR is activated in multiple tissue injuries. In this review, we summarize the roles of mTOR signaling in tissue regeneration such as neurons, muscles, the liver and the intestine.

Let-7 as biomarker, prognostic indicator, and therapy for precision medicine in cancer

Abnormal regulation and expression of microRNAs (miRNAs) has been documented in various diseases including cancer. The miRNA let-7 (MIRLET7) family controls developmental timing and differentiation. Let-7 loss contributes to carcinogenesis via an increase in its target oncogenes and stemness factors. Let-7 targets include genes regulating the cell cycle, cell signaling, and maintenance of differentiation. It is categorized as a tumor suppressor because it reduces cancer aggressiveness, chemoresistance, and radioresistance. However, in rare situations let-7 acts as an oncogene, increasing cancer migration, invasion, chemoresistance, and expression of genes associated with progression and metastasis. Here, we review let-7 function as tumor suppressor and oncogene, considering let-7 as a potential diagnostic and prognostic marker, and a therapeutic target for cancer treatment. We explain the complex regulation and function of different let-7 family members, pointing to abnormal processes involved in carcinogenesis. Let-7 is a promising option to complement conventional cancer therapy, but requires a tumor specific delivery method to avoid toxicity. While let-7 therapy is not yet established, we make the case that assessing its tumor presence is crucial when choosing therapy. Clinical data demonstrate that let-7 can be used as a biomarker for rational precision medicine decisions, resulting in improved patient survival.

Dynamics and predicted drug response of a gene network linking dedifferentiation with beta-catenin dysfunction in hepatocellular carcinoma

BACKGROUND & AIMS

Alterations of individual genes variably affect the development of hepatocellular carcinoma (HCC). Thus, we aimed to characterize the function of tumor-promoting genes in the context of gene regulatory networks (GRNs).

METHODS

Using data from The Cancer Genome Atlas, from the LIRI-JP (Liver Cancer - RIKEN, JP project), and from our transcriptomic, transfection and mouse transgenic experiments, we identify a GRN which functionally links LIN28B-dependent dedifferentiation with dysfunction of β-catenin (CTNNB1). We further generated and validated a quantitative mathematical model of the GRN using human cell lines and in vivo expression data.

RESULTS

We found that LIN28B and CTNNB1 form a GRN with SMARCA4, Let-7b (MIRLET7B), SOX9, TP53 and MYC. GRN functionality is detected in HCC and gastrointestinal cancers, but not in other cancer types. GRN status negatively correlates with HCC prognosis, and positively correlates with hyperproliferation, dedifferentiation and HGF/MET pathway activation, suggesting that it contributes to a transcriptomic profile typical of the proliferative class of HCC. The mathematical model predicts how the expression of GRN components changes when the expression of another GRN member varies or is inhibited by a pharmacological drug. The dynamics of GRN component expression reveal distinct cell states that can switch reversibly in normal conditions, and irreversibly in HCC. The mathematical model is available via a web-based tool which can evaluate the GRN status of HCC samples and predict the impact of therapeutic agents on the GRN.

CONCLUSIONS

We conclude that identification and modelling of the GRN provide insights into the prognosis of HCC and the mechanisms by which tumor-promoting genes impact on HCC development.

LAY SUMMARY

Hepatocellular carcinoma (HCC) is a heterogeneous disease driven by the concomitant deregulation of several genes functionally organized as networks. Here, we identified a gene regulatory network involved in a subset of HCCs. This subset is characterized by increased proliferation and poor prognosis. We developed a mathematical model which uncovers the dynamics of the network and allows us to predict the impact of a therapeutic agent, not only on its specific target but on all the genes belonging to the network.

C/EBPβ-LIP induces cancer-type metabolic reprogramming by regulating the let-7/LIN28B circuit in mice

The transcription factors LAP1, LAP2 and LIP are derived from the Cebpb-mRNA through the use of alternative start codons. High LIP expression has been associated with human cancer and increased cancer incidence in mice. However, how LIP contributes to cellular transformation is poorly understood. Here we present that LIP induces aerobic glycolysis and mitochondrial respiration reminiscent of cancer metabolism. We show that LIP-induced metabolic programming is dependent on the RNA-binding protein LIN28B, a translational regulator of glycolytic and mitochondrial enzymes with known oncogenic function. LIP activates LIN28B through repression of the let-7 microRNA family that targets the Lin28b-mRNA. Transgenic mice overexpressing LIP have reduced levels of let-7 and increased LIN28B expression, which is associated with metabolic reprogramming as shown in primary bone marrow cells, and with hyperplasia in the skin. This study establishes LIP as an inducer of cancer-type metabolic reprogramming and as a regulator of the let-7/LIN28B regulatory circuit.

Dual mechanisms of posttranscriptional regulation of Tet2 by Let-7 microRNA in macrophages

Tet methylcytosine dioxygenase 2 (Tet2) is an epigenetic regulator that removes methyl groups from deoxycytosine residues in DNA. Tet2-deficient murine macrophages show increased lipopolysaccharide (LPS)-induced and spontaneous inflammation at least partially because Tet2 acts to restrain interleukin (IL)-1β and IL-6 expression in induced cells. MicroRNAs have emerged as critical regulatory noncoding RNAs that tune immune cell responses to physiological perturbations and play roles in pathological conditions in macrophages. To determine if a microRNA played any role in Tet2 activity, we examined the interrelationship of Tet2 action and the let-7 microRNA family, utilizing several let-7 microRNA engineered murine models. We first showed that Tet2, but not Tet3, is a direct target of the let-7a-1/let-7d/let-7f-1 (let-7adf) microRNAs in macrophages. We found that overexpression or deletion of the let-7adf gene cluster causes altered IL-6 induction both in tissue culture cells induced by LPS treatment in vitro as well as in a Salmonella infection mouse model in vivo. Mechanistically, let-7adf promotes IL-6 by directly repressing Tet2 levels and indirectly by enhancing a Tet2 suppressor, the key TCA cycle metabolite, succinate. We found that Let-7adf promotes succinate accumulation by regulating the Lin28a/Sdha axis. We thereby identify two pathways of let-7 control of Tet2 and, in turn, of the key inflammatory cytokine, IL-6, thus characterizing a regulatory pathway in which a microRNA acts as a feedback inhibitor of inflammatory processes.

Modulation of TNFα Activity by the microRNA Let-7 Coordinates Zebrafish Heart Regeneration

The adult zebrafish is capable of regenerating heart muscle, resolving collagen tissue, and fully restoring heart function throughout its life. In this study, we show that the highly upregulated, epicardium-enriched microRNA let-7i functions in wound closure and cardiomyocyte proliferation. RNA sequencing experiments identified upregulated expression of members of the tumor necrosis factor (TNF) signaling pathway in the absence of let-7. Importantly, co-suppression of TNF and let-7 activity rescued epicardium migration and cardiomyocyte proliferation defects induced by depletion of let-7 alone. Sensitizing animals to low levels of TNF activity before injury culminated in repressed cardiomyocyte proliferation and wound closure defects, suggesting that levels of inflammation at the onset of injury are critical for heart regeneration. Our studies indicate that injury-induced reduction in TNF signaling by let-7 in the epicardium creates a pro-regenerative environment for cardiomyocyte proliferation during adult heart regeneration.

Targeting LIN28B reprograms tumor glucose metabolism and acidic microenvironment to suppress cancer stemness and metastasis

The altered metabolism and acidic microenvironment plays an important role in promoting tumor malignant characteristics. A small population of cancer stem cells (CSCs) were considered as a therapy target to reserve tumor relapse, resistance, and metastasis. However, the molecular mechanism that regulates CSCs metabolism remains poorly understood. In this study, we demonstrate a fundamental role of stemness gene LIN28B in maintaining CSCs glycolysis metabolism. Using LIN28B-expressing cancer cell lines, we found that the rate of extracellular acidification, glucose uptake, and lactate secretion are all suppressed by LIN28B knockdown in vitro and in vivo. Importantly, metabolic analyses reveal that CSCs have enhanced aerobic glycolysis metabolic characteristics and the glycolytic product lactate further promotes cancer associated stemness properties. LIN28B silencing suppresses MYC expression that further increases miR-34a-5p level. Furthermore, the glycolysis metabolism of human breast cancer cell line MDA-MB-231 is suppressed by either MYC siRNA or miR-34a-5p mimic. Clinically, high MYC and low miR-34a-5p level are correlated with high LIN28B expression and poor prognosis in human breast cancer patients. Notably, blocking LIN28B/MYC/miR-34a-5p signaling pathway by LIN28B-specific inhibitor causes dramatic inhibition of tumor growth and metastasis in immunodeficient orthotopic mouse models of human breast cancer cell MDA-MB-231. Taken together, our findings offer a preclinical investigation of targeting LIN28B to suppress CSCs glycolysis metabolism and tumor progression that may improve the therapeutic benefit for cancer patients.

Dendrimer-Based Lipid Nanoparticles Deliver Therapeutic FAH mRNA to Normalize Liver Function and Extend Survival in a Mouse Model of Hepatorenal Tyrosinemia Type I

mRNA-mediated protein replacement represents a promising concept for the treatment of liver disorders. Children born with fumarylacetoacetate hydrolase (FAH) mutations suffer from Hepatorenal Tyrosinemia Type 1 (HT-1) resulting in renal dysfunction, liver failure, neurological impairments, and cancer. Protein replacement therapy using FAH mRNA offers tremendous potential to cure HT-1, but is currently hindered by the development of effective mRNA carriers that can function in diseased livers. Structure-guided, rational optimization of 5A2-SC8 mRNA-loaded dendrimer lipid nanoparticles (mDLNPs) increases delivery potency of FAH mRNA, resulting in functional FAH protein and sustained normalization of body weight and liver function in FAH^-/- knockout mice. Optimization using luciferase mRNA produces DLNP carriers that are efficacious at mRNA doses as low as 0.05 mg kg^-1 in vivo. mDLNPs transfect > 44% of all hepatocytes in the liver, yield high FAH protein levels (0.5 mg kg^-1 mRNA), and are well tolerated in a knockout mouse model with compromised liver function. Genetically engineered FAH^-/- mice treated with FAH mRNA mDLNPs have statistically equivalent levels of TBIL, ALT, and AST compared to wild type C57BL/6 mice and maintain normal weight throughout the month-long course of treatment. This study provides a framework for the rational optimization of LNPs to improve delivery of mRNA broadly and introduces a specific and viable DLNP carrier with translational potential to treat genetic diseases of the liver.

Exportin-T promotes tumor proliferation and invasion in hepatocellular carcinoma

Exportin-T (XPOT) belongs to the RAN-GTPase exportin family that mediates export of tRNA from the nucleus to the cytoplasm. Up-regulation of XPOT indicates poor prognosis in breast cancer patients. However, the correlation between XPOT and hepatocellular carcinoma (HCC) remains unclear. Here, we found that high expression of XPOT in HCC indicated worse prognosis via bioinformatics analysis. Consistently, immunohistochemical staining of 95 pairs of tumors and adjacent normal liver tissues (ANLT) also showed up-regulation of XPOT. Small interfering (si) RNA transfection was used to down-regulate XPOT in HepG2 and 7721 cell lines. Cell Counting Kit-8 (CCK8) assays were performed to analyze cell proliferation. Cell migration and invasion were measured by scratch wound healing assays and migration assays. Subcutaneous xenograft models were using to explore the role of XPOT in tumor formation in vivo. Down-regulation of XPOT significantly inhibited tumor proliferation and invasion in vitro and vivo. Gene set enrichment analysis (GSEA) results indicated that XPOT may affect tumor progression through cell cycle and ubiquitin-mediated proteolysis. Furthermore, knockdown of XPOT caused a block in G0/G1 phase as evidenced by down-regulation of cyclin-dependent kinase 1 (CDK1), cyclin-dependent kinase 2 (CDK2), cyclin-dependent kinase 4 (CDK4), CyclinA1 (CCNA1), CyclinB1 (CCNB1), CyclinB2 (CCNB2), and CyclinE2 (CCNE2) in HCC cells. In conclusion, our findings indicate that XPOT could serve as a novel biomarker for prognoses and a potential therapeutic target for patients with HCC.

IGF1/IGF1R and microRNA let-7e down-regulate each other and modulate proliferation and migration of colorectal cancer cells

MicroRNA let-7 has been reported to be down-regulated in several human cancers and is now characterized as a tumor suppressor. IGF1R is over-expressed in many cancers and IGF1/IGF1R pathway is attractive target for anticancer therapy. However, the crosstalk between let-7 and IGF1/IGF1R are largely unknown. The present study showed IGF1R were significantly over-expressed in colorectal cancer tissues compared with adjacent normal tissues through immunohistochemical analysis. qRT-PCR results showed that let-7a, let-7b and let-7e were down-regulated in colorectal cancer tissues. Bioinformatics analysis revealed that both IGF1 and IGF1R mRNA are potential targets for let-7 miRNA family. Ectopic transfection of let-7e led to a significant reduction in IGF1R at protein level and their downstream Akt inhibition, as well as a reduction in cell proliferation, migration and invasion in colorectal cancer cells, while inhibition of let-7e enhanced the expression of IGF1R. On the other hand, IGF1 stimulation can significantly down-regulate the expression of let-7e in colorectal cancer cells. Taken together, our findings identify a negative feedback regulation between let-7e and IGF1/IGF1R, and suggest that let-7e could be used in IGF1R-targeted therapeutics in anticancer therapy.

ABBREVIATIONS

IGF1: insulin-like growth factor 1; IGF1R: IGF1 receptor; miRNA: microRNA; CRC: colorectal cancer; EGFR: epidermal growth factor receptor; HRP: horseradish peroxidase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide; p-Akt: phospho-Akt; PI3K: phosphoinositide 3-kinase; qRT-PCR: quantitative reverse transcription-PCR; IHC: immunohistochemical; siRNA: small interfering RNA; 3'-UTR: 3'-untranslated region.

Profiling the circulating miRnome reveals a temporal regulation of the bone injury response

Bone injury healing is an orchestrated process that starts with an inflammatory phase followed by repair and remodelling of the bone defect. The initial inflammation is characterized by local changes in immune cell populations and molecular mediators, including microRNAs (miRNAs). However, the systemic response to bone injury remains largely uncharacterized. Thus, this study aimed to profile the changes in the plasma miRnome after bone injury and determine its biological implications. Methods: A rat model of femoral bone defect was used, and animals were evaluated at days 3 and 14 after injury. Non-operated (NO) and sham operated animals were used as controls. Blood and spleen were collected and peripheral blood mononuclear cells (PBMC) and plasma were separated. Plasma miRnome was determined by RT-qPCR array and bioinformatics Ingenuity pathway analysis (IPA) was performed. Proliferation of bone marrow mesenchymal stem/stromal cells (MSC) was evaluated by Ki67 staining and high-throughput cell imaging. Candidate miRNAs were evaluated in splenocytes by RT-qPCR, and proteins found in the IPA analysis were analysed in splenocytes and PBMC by Western blot. Results: Bone injury resulted in timely controlled changes to the miRNA expression profile in plasma. At day 3 there was a major down-regulation of miRNA levels, which was partially recovered by day 14 post-injury. Interestingly, bone injury led to a significant up-regulation of let-7a, let-7d and miR-21 in plasma and splenocytes at day 14 relative to day 3 after bone injury, but not in sham operated animals. IPA predicted that most miRNAs temporally affected were involved in cellular development, proliferation and movement. MSC proliferation was analysed and found significantly increased in response to plasma of animals days 3 and 14 post-injury, but not from NO animals. Moreover, IPA predicted that miRNA processing proteins Ago2 and Dicer were specifically inhibited at day 3 post-injury, with Ago2 becoming activated at day 14. Protein levels of Ago2 and Dicer in splenocytes were increased at day 14 relative to day 3 post-bone injury and NO animals, while in PBMC, levels were reduced at day 3 (albeit Dicer was not significant) and remained low at day 14. Ephrin receptor B6 followed the same tendency as Ago2 and Dicer, while Smad2/3 was significantly decreased in splenocytes from day 14 relative to NO and day 3 post-bone injury animals. Conclusion: Results show a systemic miRNA response to bone injury that is regulated in time and is related to inflammation resolution and the start of bone repair/regeneration, unravelling candidate miRNAs to be used as biomarkers in the monitoring of healthy bone healing and as therapeutic targets for the development of improved bone regeneration therapies.

Exosome-related lncRNAs as predictors of HCC patient survival: a prognostic model

OBJECTIVES

Accumulating evidence suggests that long non-coding RNA (lncRNA) may affect hepatocellular carcinoma (HCC) progression. However, the mechanism remains unclear. Previous studies have shown that exosomes may promote tumor progression by transporting proteins. Our study aimed to determine the prognostic value of lncRNAs in HCC and the underlying mechanism.

METHODS

A dataset comprising a HCC cohort of 364 patients from The Cancer Genome Atlas (TCGA) was analyzed to identify lncRNAs with prognostic value. Co-expression and competing endogenous RNA (ceRNA) networks were constructed to investigate the mechanism of exosome-related lncRNAs. To confirm the bioinformatics analysis results, 95 pairs of clinical samples were evaluated by digoxigenin-labeled chromogenic in situ hybridization (CISH).

RESULTS

Five lncRNAs (CTD-2116N20.1, AC012074.2, RP11-538D16.2, LINC00501 and RP11-136I14.5) with significant differences were identified (P<0.001). A prognostic nomogram was constructed with a C-index of 0.701. The co-expression and ceRNA networks showed possible mechanisms for CTD-2116N20.1 and RP11-538D16.2. The CISH results confirmed that CTD-2116N20.1 and RP11-538D16.2 were correlated with a poor prognosis for HCC patients.

CONCLUSION

Our findings provide an independent and effective prognostic model to predict the survival rate of HCC patients. RP11-538D16.2 and CTD-2116N20.1 are highlighted as important exosome-related lncRNAs.

Metazoan MicroRNAs

MicroRNAs (miRNAs) are ∼22 nt RNAs that direct posttranscriptional repression of mRNA targets in diverse eukaryotic lineages. In humans and other mammals, these small RNAs help sculpt the expression of most mRNAs. This article reviews advances in our understanding of the defining features of metazoan miRNAs and their biogenesis, genomics, and evolution. It then reviews how metazoan miRNAs are regulated, how they recognize and cause repression of their targets, and the biological functions of this repression, with a compilation of knockout phenotypes that shows that important biological functions have been identified for most of the broadly conserved miRNAs of mammals.

Let-7 Suppresses B Cell Activation through Restricting the Availability of Necessary Nutrients

The control of uptake and utilization of necessary extracellular nutrients-glucose and glutamine-is an important aspect of B cell activation. Let-7 is a family of microRNAs known to be involved in metabolic control. Here, we employed several engineered mouse models, including B cell-specific overexpression of Lin28a or the let-7a-1/let-7d/let-7f-1 cluster (let-7adf) and knockout of individual let-7 clusters to show that let-7adf specifically inhibits T cell-independent (TI) antigen-induced immunoglobulin (Ig)M antibody production. Both overexpression and deletion of let-7 in this cluster leads to altered TI-IgM production. Mechanistically, let-7adf suppresses the acquisition and utilization of key nutrients, including glucose and glutamine, through directly targeting hexokinase 2 (Hk2) and by repressing a glutamine transporter Slc1a5 and a key degradation enzyme, glutaminase (Gls), a mechanism mediated by regulation of c-Myc. Our results suggest a novel role of let-7adf as a "metabolic brake" on B cell antibody production.

Microfluidic Production and Application of Lipid Nanoparticles for Nucleic Acid Transfection

Lipid nanoparticles (LNPs) are established in the biopharmaceutical industry for efficient encapsulation and cytosolic delivery of nucleic acids for potential therapeutics, with several formulations in clinical trials. The advantages of LNPs can also be applied in basic research and discovery with a microfluidic method of preparation now commercially available that allows preparations to be scaled down to quantities appropriate for cell culture. These preparations conserve expensive nucleic acids while maintaining the particle characteristics that have made LNPs successful in later stages of genetic medicine development. Additionally, this method and the resulting LNPs are seamlessly scalable to quantities appropriate for in vivo models and development of nucleic acid therapeutics.The present work describes the methodology for preparing LNPs loaded with siRNA, mRNA or plasmids using a commercially available microfluidic instrument and an accompanying transfection kit. Guidelines for application to cultured cells in a well-plate format are also provided.

MicroRNA-146b-5p Identified in Porcine Liver Donation Model is Associated with Early Allograft Dysfunction in Human Liver Transplantation

BACKGROUND Poor transplant outcome was observed in donation after brain death followed by circulatory death (DBCD), since the donor organs suffered both cytokine storm of brain death and warm ischemia injury. MicroRNAs (miRNAs) have emerged as promising disease biomarkers, so we sought to establish a miRNA signature of porcine DBCD and verify the findings in human liver transplantation. MATERIAL AND METHODS MiRNA expression was determined with miRNA sequencing in 3 types of the porcine model of organ donation, including donation after brain death (DBD) group, donation after circulatory death (DCD) group, and DBCD group. Bioinformatics analysis was performed to reveal the potential regulatory behavior of target miRNA. Human liver graft biopsy samples after reperfusion detected by fluorescence in situ hybridization were used to verify the expression of target miRNA. RESULTS We compared miRNA expression profiles of the 3 donation types. The porcine liver graft miR-146b was significantly increased and selected in the DBCD group versus in the DBD and DCD groups. The donor liver expression of human miR-146b-5p, which is homologous to porcine miR-146b, was further examined in 42 cases of human liver transplantations. High expression of miR-146b-5p successfully predicted the post-transplant early allograft dysfunction (EAD) with the area under the ROC curve (AUC) 0.759 (P=0.004). CONCLUSIONS Our results revealed the miRNA signature of DBCD liver grafts for the first time. The miR-146b-5p may have important clinical implications for monitoring liver graft function and predicating transplant outcomes.

A small molecule screen to identify regulators of let-7 targets

The let-7 family of miRNAs has been shown to be crucial in many aspects of biology, from the regulation of developmental timing to cancer. The available methods to regulate this family of miRNAs have so far been mostly genetic and therefore not easily performed experimentally. Here, we describe a small molecule screen designed to identify regulators of let-7 targets in human cells. In particular, we focused our efforts on the identification of small molecules that could suppress let-7 targets, as these could serve to potentially intercede in tumors driven by loss of let-7 activity. After screening through roughly 36,000 compounds, we identified a class of phosphodiesterase inhibitors that suppress let-7 targets. These compounds stimulate cAMP levels and raise mature let-7 levels to suppress let-7 target genes in multiple cancer cell lines such as HMGA2 and MYC. As a result, these compounds also show growth inhibitory activity on cancer cells.

MYC is downregulated by a mitochondrial checkpoint mechanism

The MYC proto-oncogene serves as a rheostat coupling mitogenic signaling with the activation of genes regulating growth, metabolism and mitochondrial biogenesis. Here we describe a novel link between mitochondria and MYC levels. Perturbation of mitochondrial function using a number of conventional and novel inhibitors resulted in the decreased expression of MYC mRNA. This decrease in MYC mRNA occurred concomitantly with an increase in the levels of tumor-suppressive miRNAs such as members of the let-7 family and miR-34a-5p. Knockdown of let-7 family or miR-34a-5p could partially restore MYC levels following mitochondria damage. We also identified let-7-dependent downregulation of the MYC mRNA chaperone, CRD-BP (coding region determinant-binding protein) as an additional control following mitochondria damage. Our data demonstrates the existence of a homeostasis mechanism whereby mitochondrial function controls MYC expression.

Animal Models to Study MicroRNA Function

The discovery of the microRNAs, lin-4 and let-7 as critical mediators of normal development in Caenorhabditis elegans and their conservation throughout evolution has spearheaded research toward identifying novel roles of microRNAs in other cellular processes. To accurately elucidate these fundamental functions, especially in the context of an intact organism, various microRNA transgenic models have been generated and evaluated. Transgenic C. elegans (worms), Drosophila melanogaster (flies), Danio rerio (zebrafish), and Mus musculus (mouse) have contributed immensely toward uncovering the roles of multiple microRNAs in cellular processes such as proliferation, differentiation, and apoptosis, pathways that are severely altered in human diseases such as cancer. The simple model organisms, C. elegans, D. melanogaster, and D. rerio, do not develop cancers but have proved to be convenient systesm in microRNA research, especially in characterizing the microRNA biogenesis machinery which is often dysregulated during human tumorigenesis. The microRNA-dependent events delineated via these simple in vivo systems have been further verified in vitro, and in more complex models of cancers, such as M. musculus. The focus of this review is to provide an overview of the important contributions made in the microRNA field using model organisms. The simple model systems provided the basis for the importance of microRNAs in normal cellular physiology, while the more complex animal systems provided evidence for the role of microRNAs dysregulation in cancers. Highlights include an overview of the various strategies used to generate transgenic organisms and a review of the use of transgenic mice for evaluating preclinical efficacy of microRNA-based cancer therapeutics.

Redox regulation of microRNAs in endometriosis-associated pain

Endometriosis is a chronic, painful condition with unknown etiology. A differential expression of microRNAs in the endometriotic tissues from women with endometriosis with pain compared to those without suggested a plausible role for miRNA or epigenetic mechanisms in the etiology of endometriotic pain. The peritoneal milieu is involved in maintenance of endometriotic lesion and nociception. We recently showed the mechanistic role for oxidized-lipoproteins (ox-LDLs) present in peritoneal fluid (PF) in endometriosis and pain. We explored the possibility of ox-LDLs modulating the expression of miRNAs in a manner similar to PF from women with endometriosis. Expression levels of miRNAs and their predicted nociceptive and inflammatory targets were determined in PF and ox-LDL treated human endometrial cell-lines. Samples from IRB-approved and consented patients with and without endometriosis or pain were used. These were compared to endometrial cell-lines treated with various forms of oxidized-lipoproteins. RNA (including miRNAs) were isolated from treated endometrial cells and expression levels were determined using commercial miRNome arrays. Cell lysates were used in immunoblotting for inflammatory proteins using a protein array. Twenty miRNAs including isoforms of miR-29, miR-181 and let-7 were mutually differentially expressed in cells treated with PF from endometriosis patients with pain and those treated with ox-LDL components. The ox-LDLs and endo-PF treatment also produced significant overexpression of microRNA predicted target genes nerve growth factor, interleukin-6 and prostaglandin E synthase and overexpression of their downstream protein targets Mip1α and MCP1. This study showed similarities between miRNA regulation in PF from endometriotic women and ox-LDLs present in abundance in the PF of these women. Key miRNAs responsible for targeting nociceptive and inflammatory molecules were downregulated in the presence of ox-LDLs and endo-PF, thus playing a role in the etiology of endometriotic pain. These redox-sensitive miRNAs can be of potential use as targets in the treatment of endometriosis-associated pain.

Overexpression of microRNA let-7 correlates with disease progression and poor prognosis in hepatocellular carcinoma

The aim of the study was to explore the clinical significance of let-7 expression in hepatocellular carcinoma (HCC).A PCR array was conducted to screen for let-7 expression in early-stage HCC. Next, the deregulation of let-7 was confirmed by quantitative real-time RT-PCR (qRT-PCR) in another set of liver tissues, including normal control (NC), chronic hepatitis (CH), liver cirrhosis (LC), HCC, and adjacent nontumor (NT) tissues. In addition, as the potential target mRNA of let-7, alpha 2(I) collagen (COL1A2) mRNA was also quantified in the above liver tissues. Finally, an association study comparing let-7 and COL1A2 and their clinical significance in HCC was conducted.PCR array analysis revealed that the expression levels of let-7a/7b/7c were significantly downregulated in early-stage HCC compared to those in NT tissues. As compared to NC samples, qRT-PCR further confirmed that let-7a/7b/7c/7e were significantly upregulated in CH, LC, and NT tissues, while there were no significant differences in expression between the HCC and NC groups. Although COL1A2 may be the target mRNA of let-7, only let-7c expression was inversely correlated with COL1A2 mRNA expression in CH tissues. In HCC tissues, levels of let-7a/7b/7c/7e were positively correlated with that of COL1A2 mRNA. The clinical significance study revealed that elevated let-7a expression was significantly correlated with serosal and vein invasion, while elevated let-7c expression was significantly correlated with vein invasion and advanced TNM stage. Elevated let-7e expression was significantly correlated with vein invasion in HCC. Significantly shorter postoperative overall survival was observed in HCC patients with high let-7c expression.The results suggest that aberrant expression of let-7a/7b/7c/7e occurs in benign liver diseases and HCC. The upregulation of let-7 expression is associated with the progression and poor prognosis of HCC, and further mechanistic studies are warranted.

Polyurethane acrylates as effective substrates for sustained in vitro culture of human myotubes

Muscular disease has debilitating effects with severe damage leading to death. Our knowledge of muscle biology, disease and treatment is largely derived from non-human cell models, even though non-human cells are known to differ from human cells in their biochemical responses. Attempts to develop highly sought after in vitro human cell models have been plagued by early cell delamination and difficulties in achieving human myotube culture in vitro. In this work, we developed polyurethane acrylate (PUA) materials to support long-term in vitro culture of human skeletal muscle tissue. Using a constant base with modulated crosslink density we were able to vary the material modulus while keeping surface chemistry and roughness constant. While previous studies have focused on materials that mimic soft muscle tissue with stiffness ca. 12kPa, we investigated materials with tendon-like surface moduli in the higher 150MPa to 2.4GPa range, which has remained unexplored. We found that PUA of an optimal modulus within this range can support human myoblast proliferation, terminal differentiation and sustenance beyond 35days, without use of any extracellular protein coating. Results show that PUA materials can serve as effective substrates for successful development of human skeletal muscle cell models and are suitable for long-term in vitro studies.

STATEMENT OF SIGNIFICANCE

We developed polyurethane acrylates (PUA) to modulate the human skeletal muscle cell growth and maturation in vitro by controlling surface chemistry, morphology and tuning material's stiffness. PUA was able to maintain muscle cell viability for over a month without any detectable signs of material degradation. The best performing PUA prevented premature cell detachment from the substrate which often hampered long-term muscle cell studies. It also supported muscle cell maturation up to the late stages of differentiation. The significance of these findings lies in the possibility to advance studies on muscle cell biology, disease and therapy by using human muscle cells instead of relying on the widely used animal-based in vitro models.

Different levels of let-7d expression modulate response of FaDu cells to irradiation and chemotherapeutics

The implication of the let-7 family in cancer development is multifaceted. The family acts as tumor suppressor miRNA although overexpression of let-7 has also been described in many types of cancer, including head and neck squamous cell carcinoma (HNSCC). The aim of this study includes whether different expression levels of let-7d has an influence on chemo- and radiosensitivity. FaDu cell line models with a gradually increased level of let-7d (models from A to E) were generated with the lentiviral system. Expression levels of pluripotency, chemo-radioresistance/apoptosis, and targets of mRNAs were analyzed by real-time reverse transcription-PCR (qRT-PCR). Radiosensitivity was analyzed using a clonogenic assay after irradiation. Response to cisplatin, 5-FU, doxorubicin, and paclitaxel was done with MTT assay. Statistically significant decrease of K-RAS (p = 0.0369) and CASPASE3 (p = 0.0342) were observed with the growing expression level of let-7d. Cisplatin, 5-FU and doxorubicin caused similar decreased of cell survival with the increase of let-7d level (p = 0.004, post-trend p = 0.046; p = 0.004, post trend p = 0.0005 and p<0.0001, post trend p = 0.0001, respectively). All models were resistant to paclitaxel, irrespective of let-7d expression levels. Only two of the generated models (A and C) were radiosensitive (p = 0.0002). Conclusion: the above results indicated that the level of let-7d expression is an important factor for cell response to irradiation and chemotherapeutics.

Emerging Role of MicroRNAs in mTOR Signaling

Mechanistic target of rapamycin (mTOR) is a conserved serine/threonine kinase that plays a critical role in the control of cellular growth and metabolism. Hyperactivation of mTOR pathway is common in human cancers, driving uncontrolled proliferation. MicroRNA (miRNA) is a class of short noncoding RNAs that regulate the expression of a wide variety of genes. Deregulation of miRNAs is a hallmark of cancer. Recent studies have revealed interplays between miRNAs and the mTOR pathway during cancer development. Such interactions appear to provide a fine-tuning of various cellular functions and contribute qualitatively to the behavior of cancer. Here we provide an overview of current knowledge regarding the reciprocal relationship between miRNAs and mTOR pathway: regulation of mTOR signaling by miRNAs and control of miRNA biogenesis by mTOR. Further research in this area may prove important for the diagnosis and therapy of human cancer.

Developmental regulation of myeloerythroid progenitor function by the Lin28b-let-7-Hmga2 axis

Daley and collaborators show that endogenous Lin28b drives erythroid-dominant fetal hematopoiesis and that decreases in Lin28b activate adult granulocyte-predominant hematopoiesis.

For appropriate development, tissue and organ system morphogenesis and maturation must occur in synchrony with the overall developmental requirements of the host. Mistiming of such developmental events often results in disease. The hematopoietic system matures from the fetal state, characterized by robust erythrocytic output that supports prenatal growth in the hypoxic intrauterine environment, to the postnatal state wherein granulocytes predominate to provide innate immunity. Regulation of the developmental timing of these myeloerythroid states is not well understood. In this study, we find that expression of the heterochronic factor Lin28b decreases in common myeloid progenitors during hematopoietic maturation to adulthood in mice. This decrease in Lin28b coincides with accumulation of mature let-7 microRNAs, whose biogenesis is regulated by Lin28 proteins. We find that inhibition of let-7 in the adult hematopoietic system recapitulates fetal erythroid-dominant hematopoiesis. Conversely, deletion of Lin28b or ectopic activation of let-7 microRNAs in the fetal state induces a shift toward adult-like myeloid-dominant output. Furthermore, we identify Hmga2 as an effector of this genetic switch. These studies provide the first detailed analysis of the roles of endogenous Lin28b and let-7 in the timing of hematopoietic states during development.

Lin28 and let-7 in the Metabolic Physiology of Aging

The Lin28/let-7 molecular switch has emerged as a central regulator of growth signaling pathways and metabolic enzymes. Initially discovered to regulate developmental timing in the nematode, the Lin28/let-7 pathway of RNA regulation has gained prominence for its role in mammalian stem cells, cancer cells, tissue development, and aging. By regulating RNAs, the pathway coordinates cellular growth and cellular metabolism to influence metabolic physiology. Here, we review this regulatory mechanism and its impact on cancers, which reactivate Lin28, cardiovascular diseases, which implicate let-7, human genome-wide association studies (GWAS) of growth, and metabolic diseases, which implicate the Lin28/let-7 pathway. We also highlight questions relating to Barker's Hypothesis and the potential actions of the Lin28/let-7 pathway on programming long-lasting epigenetic effects.

Stem cell mitochondria during aging

Mitochondria are the central hubs of cellular metabolism, equipped with their own mitochondrial DNA (mtDNA) blueprints to direct part of the programming of mitochondrial oxidative metabolism and thus reactive oxygen species (ROS) levels. In stem cells, many stem cell factors governing the intricate balance between self-renewal and differentiation have been found to directly regulate mitochondrial processes to control stem cell behaviors during tissue regeneration and aging. Moreover, numerous nutrient-sensitive signaling pathways controlling organismal longevity in an evolutionarily conserved fashion also influence stem cell-mediated tissue homeostasis during aging via regulation of stem cell mitochondria. At the genomic level, it has been demonstrated that heritable mtDNA mutations and variants affect mammalian stem cell homeostasis and influence the risk for human degenerative diseases during aging. Because such a multitude of stem cell factors and signaling pathways ultimately converge on the mitochondria as the primary mechanism to modulate cellular and organismal longevity, it would be most efficacious to develop technologies to therapeutically target and direct mitochondrial repair in stem cells, as a unified strategy to combat aging-related degenerative diseases in the future.

Comparison of Magnetic Resonance Imaging and Serum Biomarkers for Detection of Human Pluripotent Stem Cell-Derived Teratomas

The use of cells derived from pluripotent stem cells (PSCs) for regenerative therapies confers a considerable risk for neoplastic growth and teratoma formation. Preclinical and clinical assessment of such therapies will require suitable monitoring strategies to understand and mitigate these risks. Here we generated human-induced pluripotent stem cells (iPSCs), selected clones that continued to express reprogramming factors after differentiation into cardiomyocytes, and transplanted these cardiomyocytes into immunocompromised rat hearts post-myocardial infarction. We compared magnetic resonance imaging (MRI), cardiac ultrasound, and serum biomarkers for their ability to delineate teratoma formation and growth. MRI enabled the detection of teratomas with a volume >8 mm³. A combination of three plasma biomarkers (CEA, AFP, and HCG) was able to detect teratomas with a volume >17 mm³ and with a sensitivity of more than 87%. Based on our findings, a combination of serum biomarkers with MRI screening may offer the highest sensitivity for teratoma detection and tracking.

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A combination of three serum biomarkers can detect teratomas >17 mm³

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MRI can detect teratomas >8 mm³

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Immature teratomas not detectable by serum biomarkers can be detected with MRI

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Combining MRI and serum biomarkers enables sensitive detection of neoplastic growth

Let-7a suppresses glioma cell proliferation and invasion through TGF-β/Smad3 signaling pathway by targeting HMGA2

It has been shown that let-7a was associated with the tumorigenesis of glioma. Our study was designed to infer how let-7a targets high-mobility AT-hook 2 (HMGA2) and suppresses glioma cell proliferation, invasion, and migration. Glioma tissues from 60 glioma patients and 10 normal brain tissues were collected in this study. Real-time quantitative reverse transcription-PCR (qRT-PCR) and in situ hybridization were used to detect the expression levels of let-7a in tissues and cells. The HMGA2 and the proteins related to transforming growth factor-beta (TGF-β)/Smad3 signaling pathway were measured by immunohistochemistry and western blot. Glioma U87 cells were transfected with either let-7a mimics, HMGA2 small interfering RNA (siRNA), let-7a mimics + HMGA2, HMGA2, or scramble. A cell counting kit-8 (CCK-8) assay was used to detect and compare the difference among various transfection groups. Glioma tumor xenograft models on mice were built to evaluate the effects of let-7a and HMGA2 siRNA on glioma tumors in vivo. The expression level of let-7a significantly downregulated in glioma tissues, while the HMGA2 positive expression rate notably increased compared with those in normal brain tissues (all P < 0.05). Moreover, the expression levels of let-7a and HMGA2 were correlated with glioma grades (all P < 0.05). The proliferation of U87 cells transfected with let-7a mimics or HMGA2 siRNA was significantly inhibited in comparison to the blank control group and the apoptosis rates of U87 cells transfected with let-7a mimics or HMGA2 siRNA were significantly higher than those in the blank control group (all P < 0.05). Let-7a or HMGA2 siRNA could remarkably attenuate the invasion and migration ability of glioma cells (all P < 0.05). Apart from that, over-expressed exogenous HMGA2 could reverse the inhibition of glioma cell metastasis and proliferation induced by let-7a. As suggested by immunohistochemistry and western blot, the expression levels of TGF-β1 and p-Smad3 significantly decreased compared with the blank or scramble group (all P < 0.05). Thus, let-7a and HMGA2 siRNA could effectively suppress the growth of tumors in glioma xenograft models. Let-7a may suppress the proliferation and invasion of glioma cells through mediating TGF-β/Smad3 signaling pathway by targeting HMGA2.