Selection of aptamers for mature white adipocytes by cell SELEX using flow cytometry

Regulation of adipogenesis by exosomal milk miRNA

Milk is a rich source of miRNA packaged in exosomes. Evidence for the systemic uptake and tissue distribution of milk exosomes was reported in newborn and adult humans and animals. Breastfeeding in infants was associated with a reduced risk of obesity. Numerous adipogenesis-related miRNAs have been detected in human milk exosomes. It has been demonstrated that ingested exosomal milk miRNAs may alter gene expression in offspring to regulate their metabolism and growth. In humans, consumption of other species' milk, such as cows and goats, is continued through adulthood. Since miRNAs are conserved, the concern of cross-species transfer of adipogenic miRNA has been raised in recent years, and the increase in obesity worldwide was attributed partially to dairy milk consumption by humans. However, evidence is still weak. Research emphasizes the need for an adequate number of exosomal milk's miRNAs to reach the target cell for biological action to be achieved. It was reported that obese women's milk had less miRNA-148a and miRNA-30b, which may affect the fat acquisition of their babies. Some exosomal milk miRNAs, such as miRNA-29, miRNA-148, miRNA-30b and miRNA-125b, may have epigenetic effects on milk recipients. Moreover, the ability of milk exosomes to cross the gastrointestinal barrier makes them a promising oral drug delivery tool. Yet, exosomes may also be tagged with specific ligands which target certain tissues. Thus, milk exosomes can be engineered and loaded with certain miRNAs responsible for adipocyte differentiation, conversion, or browning. Modifications in the miRNA cargo of exosomes can benefit human health and be an alternative to traditional drugs.

Research progress of whole-cell-SELEX selection and the application of cell-targeting aptamer

BACKGROUND

Aptamers refer to the artificially synthesized nucleic acid sequences (DNA/RNA) that can bind to a wide range of targets with high affinity and specificity, which are generally generated from systematic evolution of ligands by exponential enrichment (SELEX). As a novel method of aptamers screening, whole-cell-SELEX (WC-SELEX) has gained more and more attention in many fields such as biomedicine, analytical chemistry, and molecular diagnostics due to its ability to screen multiple potential aptamers without knowing the detailed structural information of target molecules.

METHODS AND RESULTS

In recent years, with the deepening of research on application of aptamers, the traditional WC-SELEX cannot meet the practical application because of long experimental period, complicated operation process and low specificity, etc. Therefore, the development of more efficient methods for screening aptamer is always on the road. This paper summarizes the current research status of WC-SELEX for bacteria, parasites and animal cells, and reviews the latest advances of WC-SELEX techniques that are dependent on novel instruments, materials and microelectronics, including fluorescence-activated cell sorting-assisted SELEX, three-dimensional assisted WC-SELEX, and microfluidic chip system-assisted WC-SELEX. In addition, the application of aptamers targeting cells was discussed.

CONCLUSION

Taken together, this review is aimed at providing a reference for WC-SELEX selection and application of aptamer targeting cells.

Delivery of miRNAs to the adipose organ for metabolic health

Despite the increasing prevalence of obesity and diabetes, there is no efficient treatment to combat these epidemics. The adipose organ is the main site for energy storage and plays a pivotal role in whole body lipid metabolism and energy homeostasis, including remodeling and dysfunction of adipocytes and adipose tissues in obesity and diabetes. Thus, restoring and balancing metabolic functions in the adipose organ is in demand. MiRNAs represent a novel class of drugs and drug targets, as they are heavily involved in the regulation of many cellular and metabolic processes and diseases, likewise in adipocytes. In this review, we summarize key regulatory activities of miRNAs in the adipose organ, discuss various miRNA replacement and inhibition strategies, promising delivery systems for miRNAs and reflect the future of novel miRNA-based therapeutics to target adipose tissues with the ultimate goal to combat metabolic disorders.

Browning of white adipocytes by gold nanocluster mediated electromagnetic induction heating hyperthermia

Browning of white adipose tissue (WAT) is becoming an attractive therapeutic target for obesity. Great efforts have been made to develop effective approaches to induce browning. Unfortunately, the current methods suffer from a series of disadvantages, such as low efficiency, unsatisfactory stability, and side effects. Herein, we report a new approach to induce browning of 3T3-L1 white adipocytes based on electromagnetic induction heating (EIH) hyperthermia. In particular, adipocyte-targeting aptamer modified gold nanoclusters (Apt-AuNCs) were employed as the mediators of EIH. Apt-AuNCs had good biocompatibility and excellent targeting performance with white adipocytes. After Apt-AuNCs/EIH treatment, adipocytes with characteristic multilocular and small lipid droplets increased, and the content of triglycerides reduced effectively. Apt-AuNCs/EIH treatment also significantly increased the mitochondrial activity in adipocytes. Meanwhile, the mRNA levels of key genes that are involved in browning, for example UCP1, PRDM16, PPARγ, and PGC-1α, were upregulated. Finally, the induction mechanism of Apt-AuNCs/EIH on browning of white adipocytes was explained by the synergistic effects of EIH hyperthermia and pharmacological action of AuNCs. To the best of our knowledge, this is the first attempt on induction of browning by metal nanocluster-mediated EIH hyperthermia, thus providing an interesting and efficient channel for obesity treatment.

Decoding the Complex Free Radical Cascade by Using a DNA Framework-Based Artificial DNA Encoder

DNA-based molecular communications (DMC) are critical for regulating biological networks to maintain stable organismic functions. However, the complicated, time-consuming information transmission process involved in genome-coded DMC and the limited, vulnerable decoding activity generally lead to communication impairment or failure, in response to external stimuli. Herein, we present a conceptually innovative DMC strategy mediated by the DNA framework-based artificial DNA encoder. With the free-radical cascade as a proof-of-concept study, the artificial DNA encoder shows active sensing and real-time actuation, in situ and broad free radical-decoding efficacy, as well as robust resistance to environmental noise. It can also block undesirable short-to-medium-range communications between free radicals and inflammatory networks, leading to a synergistic anti-obesity effect. The artificial DNA encoder-based DMC may be generalized to other communication systems for a variety of applications.

Identification and characterization of adipose surface epitopes

Adipose tissue is a central regulator of metabolism and an important pharmacological target to treat the metabolic consequences of obesity, such as insulin resistance and dyslipidemia. Among the various cellular compartments, the adipocyte cell surface is especially appealing as a drug target as it contains various proteins that when activated or inhibited promote adipocyte health, change its endocrine function and eventually maintain or restore whole-body insulin sensitivity. In addition, cell surface proteins are readily accessible by various drug classes. However, targeting individual cell surface proteins in adipocytes has been difficult due to important functions of these proteins outside adipose tissue, raising various safety concerns. Thus, one of the biggest challenges is the lack of adipose selective surface proteins and/or targeting reagents. Here, we discuss several receptor families with an important function in adipogenesis and mature adipocytes to highlight the complexity at the cell surface and illustrate the problems with identifying adipose selective proteins. We then discuss that, while no unique adipocyte surface protein might exist, how splicing, posttranslational modifications as well as protein/protein interactions can create enormous diversity at the cell surface that vastly expands the space of potentially unique epitopes and how these selective epitopes can be identified and targeted.

Live and Let Dye: Visualizing the Cellular Compartments of the Malaria Parasite Plasmodium falciparum

Malaria remains one of the deadliest diseases worldwide and it is caused by the protozoan parasite Plasmodium spp. Parasite visualization is an important tool for the correct detection of malarial cases but also to understand its biology. Advances in visualization techniques promote new insights into the complex life cycle and biology of Plasmodium parasites. Live cell imaging by fluorescence microscopy or flow cytometry are the foundation of the visualization technique for malaria research. In this review, we present an overview of possibilities in live cell imaging of the malaria parasite. We discuss some of the state-of-the-art techniques to visualize organelles and processes of the parasite and discuss limitation and advantages of each technique. © 2019 International Society for Advancement of Cytometry.

Selection of aptamers against Lactoferrin based on silver enhanced and fluorescence-activated cell sorting

We report a novel method for efficiently screening aptamers from a complex ssDNA library based on silver decahedral nanoparticles (AgNP) and fluorescence activated cell sorting (FACS). In this method, target protein (lactoferrin) and negative proteins (α-lactalbumin, β-lactoglobulin, bovine serum albumin, casein) were respectively immobilized on polystyrene microspheres (PS) to form PS^Lac, PS^α-Lac, PS^β-Lac, PS^BSA and PS^Cas. PS^Lac was firstly interacted with Cy5 labeled library (Lib), then hybridized with Cy5 modified silver decahedral nanoparticles (AgNP^Cy5) to form PS^Lac/Lib/AgNP^Cy5 conjugates. FACS was used to separate and collect PS^Lac/Lib/AgNP^Cy5 conjugates from complicated complex. AgNP was used to increase the fluorescence intensity in the selecting process and choose non-self-hybridization of Lib. Six aptamers (Ylac1, Ylac4, Ylac5, Ylac6, Ylac8 and Ylac9) were obtained after five-round of selection. These aptamers showed good specificity towards lactoferrin in the presence of negative proteins. The equilibrium dissociation constants (K_d) of six aptamers were calculated and all were in the nanomolar range. In a word, AgNP-FACS SELEX (AgFACS-SELEX) is a rapid, sensitive and highly efficient method for screening aptamers.

Selection and Characterization of Single-Stranded DNA Aptamers Binding Human B-Cell Surface Protein CD20 by Cell-SELEX

The B-lymphocyte antigen (CD20) is a suitable target for single-stranded (ss) nucleic acid oligomer (aptamers). The aim of study was selection and characterization of a ssDNA aptamer against CD20 using Cell-Systematic Evolution of Ligands by Exponential Enrichment (Cell-SELEX). The cDNA clone of CD20 (pcDNA-CD20) was transfected to human embryonic kidney (HEK293T) cells. Ten rounds of Cell-SELEX was performed on recombinant HEK-CD20 cells. The final eluted ssDNA pool was amplified and ligated in T/A vector for cloning. The plasmids of positive clones were extracted, sequenced and the secondary structures of the aptamers predicted using DNAMAN^® software. The sequencing results revealed 10 different types; three of them had the highest thermodynamic stability, named AP-1, AP-2 and AP-3. The AP-1 aptamer was the most thermodynamically stable one (ΔGAP-1 = −10.87 kcal/mol) with the highest binding affinity to CD20 (96.91 ± 4.5 nM). Since, the CD20 is a suitable target for recognition of B-Cell. The selected aptamers could be comparable to antibodies with many advantages. The AP-1, AP-2 and AP-3 could be candidate instead of antibodies for diagnostic and therapeutic applications in immune deficiency, autoimmune diseases, leukemia and lymphoma.

Development of Cell-Specific Aptamers: Recent Advances and Insight into the Selection Procedures

Systematic evolution of ligands by exponential enrichment (SELEX) is an established procedure for developing short single-stranded nucleic acid ligands called aptamers against a target of choice. This approach has also been used for developing aptamers specific to whole cells named Cell-SELEX. Aptamers selected by Cell-SELEX have the potential to act as cell specific therapeutics, cell specific markers or cell specific drug delivery and imaging agents. However, aptamer development is a laborious and time-consuming process which is often challenging due to the requirement of frequent optimization of various steps involved in Cell-SELEX procedures. This review provides an insight into various procedures for selection, aptamer enrichment, regeneration and aptamer-binding analysis, in addition to a very recent update on all aptamers selected by Cell-SELEX procedures.

Aptamer selection and applications for breast cancer diagnostics and therapy

Aptamers are short non-coding, single-stranded oligonucleotides (RNA or DNA) developed through Systematic Evolution of Ligands by Exponential enrichment (SELEX) in vitro. Similar to antibodies, aptamers can bind to specific targets with high affinity, and are considered promising therapeutic agents as they have several advantages over antibodies, including high specificity, stability, and non-immunogenicity. Furthermore, aptamers can be produced at a low cost and easily modified, and are, therefore, called "chemical antibodies". In the past years, a variety of aptamers specifically bound to both breast cancer biomarkers and cells had been selected. Besides, taking advantage of nanomaterials, there were a number of aptamer-nanomaterial conjugates been developed and widely investigated for diagnostics and targeted therapy of breast cancer. In this short review, we first present a systematical review of various aptamer selection methods. Then, various aptamer-based diagnostic and therapeutic strategies of breast cancer were provided. Finally, the current problems, challenges, and future perspectives in the field were thoroughly discussed.

Methyltransferase and demethylase profiling studies during brown adipocyte differentiation

Although brown adipose tissue is important with regard to energy balance, the molecular mechanism of brown adipocyte differentiation has not been extensively studied. Specifically, regulation factors at the level of protein modification are largely unknown. In this study, we examine the changes in the expression level of enzymes which are involved in protein lysine methylation during brown adipocyte differentiation. Several enzymes, in this case SUV420H2, PRDM9, MLL3 and JHDM1D, were found to be up-regulated. On the other hand, Set7/9 was significantly down-regulated. In the case of SUV420H2, the expression level increased sharply during brown adipocyte differentiation, whereas the expression of SUV420H2 was marginally enhanced during the white adipocyte differentiation. The knock-down of SUV420H2 caused the suppression of brown adipocyte differentiation, as compared to a scrambled control. These results suggest that SUV420H2, a methyltransferase, is involved in brown adipocyte differentiation, and that the methylation of protein lysine is important in brown adipocyte differentiation. [BMB Reports 2016; 49(7): 388-393]

Aptamers: novel diagnostic and therapeutic tools for diabetes mellitus and metabolic diseases

Diabetes mellitus is one of the most common chronic diseases that threatens human health in worldwide populations. Despite enormous efforts invested in the study of diabetes mellitus, the development of precise diagnoses and treatments for this disease remains difficult due to the limitations of current techniques. Therefore, new methods are currently being developed. Aptamers are oligonucleotides that bind to specific target molecules and have been widely applied as diagnostic and therapeutic tools. In recent years, aptamers have been utilized in the study of diabetes mellitus and metabolic diseases. In this review, we highlight recent developments and new perspectives on aptamers in the field of diabetes mellitus and other metabolic diseases. Aptamers could potentially provide the means for efficient diagnoses and therapies against diabetes mellitus.

c-Jun regulates adipocyte differentiation via the KLF15-mediated mode

Abnormal adipocyte differentiation is implicated in the development of metabolic disorders such as obesity and type II diabetes. Thus, an in-depth understanding of the molecular mechanisms associated with adipocyte differentiation is the first step in overcoming obesity and its related metabolic diseases. Here, we examined the role of c-Jun as a transcription factor in adipocyte differentiation. c-Jun overexpression in murine 3T3-L1 preadipocytes significantly inhibited adipocyte differentiation. In addition, the expression level of KLF15, an upstream effector of the key adipogenic factors C/EBPα and PPARγ, was decreased upon the ectopic expression of c-Jun. We found that c-Jun inhibited basal and glucocorticoid receptor (GR)-induced promoter activities of KLF15. c-Jun directly bound near the glucocorticoid response element (GRE) sites in the KLF15 promoter and inhibited adjacent promoter occupancies of GR. Furthermore, the restoration of KLF15 expression in 3T3-L1 cells with the stable ectopic expression of c-Jun partially rescued adipocyte differentiation. Our results demonstrate that c-Jun can suppress adipocyte differentiation through the down-regulation of KLF15 at the transcriptional level. This study proposes a novel mechanism by which c-Jun regulates adipocyte differentiation.

Identification of DNA aptamers toward epithelial cell adhesion molecule via cell-SELEX

The epithelial cell adhesion molecule (EpCAM, also known as CD326) is a transmembrane glycoprotein that is specifically detected in most adenocarcinomas and cancer stem cells. In this study, we performed a Cell systematic evolution of ligands by exponential enrichment (SELEX) experiment to isolate the aptamers against EpCAM. After seven round of Cell SELEX, we identified several aptamer candidates. Among the selected aptamers, EP166 specifically binds to cells expressing EpCAM with an equilibrium dissociation constant (Kd) in a micromolar range. On the other hand, it did not bind to negative control cells. Moreover, EP166 binds to J1ES cells, a mouse embryonic stem cell line. Therefore, the isolated aptamers against EpCAM could be used as a stem cell marker or in other applications in both stem cell and cancer studies.