Formulation of siRNA nanoparticles, transfection and enhanced adhesion -penetration in nasal mucosal tissue

This study investigates the efficacy of trimethyl chitosan (TMC) nanoparticles (NPs) for the delivery of small interfering RNA (siRNA) targeting the EGFR gene, with a focus on optimizing complexation efficiency, release profiles, and transfection efficiency, as well as investigating mucoadhesion and mucopenetration properties. TMC nanoparticles were formulated at various siRNA:TMC weight-to-weight (w:w) ratios and assessed for binding efficiency, release in the presence of heparin, physical properties, cytotoxicity, and EGFR knockdown efficiency in HeLa cells. The integration of additives such as dextran sulfate (DS), tripolyphosphate (TPP), and hyaluronic acid (HA) was explored to enhance nanoparticle performance. Results demonstrated that higher TMC ratios improved siRNA binding and reduced release rates, with additives further stabilizing the nanoparticles. The optimized formulations showed high cell viability and significant EGFR silencing, indicating effective transfection. Mucoadhesion and mucopenetration two-photon microscopy studies on rabbit nasal mucosa confirmed the superior performance of TMC nanoparticles over free siRNA, highlighting their potential for non-invasive gene therapy applications.

The Potential Role of Connexins in the Pathogenesis of Atherosclerosis

Connexins (Cx) are members of a protein family which enable extracellular and intercellular communication through hemichannels and gap junctions (GJ), respectively. Cx take part in transporting important cell-cell messengers such as 3',5'-cyclic adenosine monophosphate (cAMP), adenosine triphosphate (ATP), and inositol 1,4,5-trisphosphate (IP3), among others. Therefore, they play a significant role in regulating cell homeostasis, proliferation, and differentiation. Alterations in Cx distribution, degradation, and post-translational modifications have been correlated with cancers, as well as cardiovascular and neurological diseases. Depending on the isoform, Cx have been shown either to promote or suppress the development of atherosclerosis, a progressive inflammatory disease affecting large and medium-sized arteries. Cx might contribute to the progression of the disease by enhancing endothelial dysfunction, monocyte recruitment, vascular smooth muscle cell (VSMC) activation, or by inhibiting VSMC autophagy. Inhibition or modulation of the expression of specific isoforms could suppress atherosclerotic plaque formation and diminish pro-inflammatory conditions. A better understanding of the complexity of atherosclerosis pathophysiology linked with Cx could result in developing novel therapeutic strategies. This review aims to present the role of Cx in the pathogenesis of atherosclerosis and discusses whether they can become novel therapeutic targets.

Functional genomic tools for emerging model species

Most studies in the field of ecology and evolution aiming to connect genotype to phenotype rarely validate identified loci using functional tools. Recent developments in RNA interference (RNAi) and clustered regularly interspaced palindromic repeats (CRISPR)-Cas genome editing have dramatically increased the feasibility of functional validation. However, these methods come with specific challenges when applied to emerging model organisms, including limited spatial control of gene silencing, low knock-in efficiencies, and low throughput of functional validation. Moreover, many functional studies to date do not recapitulate ecologically relevant variation, and this limits their scope for deeper insights into evolutionary processes. We therefore argue that increased use of gene editing by allelic replacement through homology-directed repair (HDR) would greatly benefit the field of ecology and evolution.

Targeted Manipulation of Brain Serotonin: RNAi-Mediated Knockdown of Tryptophan Hydroxylase 2 in Rats

Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in the biosynthesis of the biogenic monoamine serotonin (5-hydroxytryptamine, 5-HT). Two existing TPH isoforms are responsible for the generation of two distinct serotonergic systems in vertebrates. TPH1, predominantly expressed in the gastrointestinal tract and pineal gland, mediates 5-HT biosynthesis in non-neuronal tissues, while TPH2, mainly found in the raphe nuclei of the brain stem, is accountable for the production of 5-HT in the brain. Neuronal 5-HT is a key regulator of mood and behavior and its deficiency has been implicated in a variety of neuropsychiatric disorders, e.g., depression and anxiety. To gain further insights into the complexity of central 5-HT modulations of physiological and pathophysiological processes, a new transgenic rat model, allowing an inducible gene knockdown of Tph2, was established based on doxycycline-inducible shRNA-expression. Biochemical phenotyping revealed a functional knockdown of Tph2 mRNA expression following oral doxycycline administration, with subsequent reductions in the corresponding levels of TPH2 enzyme expression and activity. Transgenic rats showed also significantly decreased tissue levels of 5-HT and its degradation product 5-Hydroxyindoleacetic acid (5-HIAA) in the raphe nuclei, hippocampus, hypothalamus, and cortex, while peripheral 5-HT concentrations in the blood remained unchanged. In summary, this novel transgenic rat model allows inducible manipulation of 5-HT biosynthesis specifically in the brain and may help to elucidate the role of 5-HT in the pathophysiology of affective disorders.

Transcription factors: Time to deliver

Transcription factors (TFs) are at the center of the broad regulatory network orchestrating gene expression programs that elicit different biological responses. For a long time, TFs have been considered as potent drug targets due to their implications in the pathogenesis of a variety of diseases. At the same time, TFs, located at convergence points of cellular regulatory pathways, are powerful tools providing opportunities both for cell type change and for managing the state of cells. This task formulation requires the TF modulation problem to come to the fore. We review several ways to manage TF activity (small molecules, transfection, nanocarriers, protein-based approaches), analyzing their limitations and the possibilities to overcome them. Delivery of TFs could revolutionize the biomedical field. Whether this forecast comes true will depend on the ability to develop convenient technologies for targeted delivery of TFs.

RNAi-mediated knockdown of mouse melanocortin-4 receptor in vitro and in vivo, using an siRNA expression construct based on the mir-187 precursor

RNA interference (RNAi) is a powerful tool for the study of gene function in mammalian systems, including transgenic mice. Here, we report a gene knockdown system based on the human mir-187 precursor. We introduced small interfering RNA (siRNA) sequences against the mouse melanocortin-4 receptor (mMc4r) to alter the targeting of miR-187. The siRNA-expressing cassette was placed under the control of the cytomegalovirus (CMV) early enhancer/chicken β-actin promoter. In vitro, the construct efficiently knocked down the gene expression of a co-transfected mMc4r-expression vector in cultured mammalian cells. Using this construct, we generated a transgenic mouse line which exhibited partial but significant knockdown of mMc4r mRNA in various brain regions. Northern blot analysis detected transgenic expression of mMc4r siRNA in these regions. Furthermore, the transgenic mice fed a normal diet ate 9% more and were 30% heavier than wild-type sibs. They also developed hyperinsulinemia and fatty liver as do mMc4r knockout mice. We determined that this siRNA expression construct based on mir-187 is a practical and useful tool for gene functional studies in vitro as well as in vivo.

Assessment of Artificial MiRNA Architectures for Higher Knockdown Efficiencies without the Undesired Effects in Mice

RNAi-based strategies have been used for hypomorphic analyses. However, there are technical challenges to achieve robust, reproducible knockdown effect. Here we examined the artificial microRNA (amiRNA) architectures that could provide higher knockdown efficiencies. Using transient and stable transfection assays in cells, we found that simple amiRNA-expression cassettes, that did not contain a marker gene (−MG), displayed higher amiRNA expression and more efficient knockdown than those that contained a marker gene (+MG). Further, we tested this phenomenon in vivo, by analyzing amiRNA-expressing mice that were produced by the pronuclear injection-based targeted transgenesis (PITT) method. While we observed significant silencing of the target gene (eGFP) in +MG hemizygous mice, obtaining −MG amiRNA expression mice, even hemizygotes, was difficult and the animals died perinatally. We obtained only mosaic mice having both “−MG amiRNA” cells and “amiRNA low-expression” cells but they exhibited growth retardation and cataracts, and they could not transmit the –MG amiRNA allele to the next generation. Furthermore, +MG amiRNA homozygotes could not be obtained. These results suggested that excessive amiRNAs transcribed by −MG expression cassettes cause deleterious effects in mice, and the amiRNA expression level in hemizygous +MG amiRNA mice is near the upper limit, where mice can develop normally. In conclusion, the PITT-(+MG amiRNA) system demonstrated here can generate knockdown mouse models that reliably express highest and tolerable levels of amiRNAs.

CRISPR/Cas9-based generation of knockdown mice by intronic insertion of artificial microRNA using longer single-stranded DNA

Knockdown mouse models, where gene dosages can be modulated, provide valuable insights into gene function. Typically, such models are generated by embryonic stem (ES) cell-based targeted insertion, or pronuclear injection, of the knockdown expression cassette. However, these methods are associated with laborious and time-consuming steps, such as the generation of large constructs with elements needed for expression of a functional RNAi-cassette, ES-cell handling, or screening for mice with the desired knockdown effect. Here, we demonstrate that reliable knockdown models can be generated by targeted insertion of artificial microRNA (amiRNA) sequences into a specific locus in the genome [such as intronic regions of endogenous eukaryotic translation elongation factor 2 (eEF-2) gene] using the Clustered Regularly Interspaced Short Palindromic Repeats/Crispr associated 9 (CRISPR/Cas9) system. We used in vitro synthesized single-stranded DNAs (about 0.5-kb long) that code for amiRNA sequences as repair templates in CRISPR/Cas9 mutagenesis. Using this approach we demonstrate that amiRNA cassettes against exogenous (eGFP) or endogenous [orthodenticle homeobox 2 (Otx2)] genes can be efficiently targeted to a predetermined locus in the genome and result in knockdown of gene expression. We also provide a strategy to establish conditional knockdown models with this method.

RNAi-mediated knockdown of inhibin α subunit increased apoptosis in granulosa cells and decreased fertility in mice

Inhibin α (INHα), a member of TGFβ superfamily, is an important modulator of reproductive function that plays a vital role in follicular changes, cell differentiation, oocyte development, and ultimately in mammalian reproduction. However, the role of inhibin α in female fertility and ovarian function remains largely unknown. To define its role in reproduction, transgenic mice of RNAi-INHα that knock down the INHα expression by shRNAi were used. Inhibin α subunit gene was knocked down successfully at both transcriptional and translational levels by RNAi PiggyBac transposon (Pbi) mediated recombinant pshRNA vectors and purified DNA fragments were microinjected into mouse zygotes. Results showed that transgenic female mice were sub-fertile and exhibited 35.28% reduction in litter size in F1 generation relative to wild type. The decreased litter size associated with the reduction in the number of oocytes ovulated after puberty. Serum INHα level was significantly decreased in both 3 and 6 weeks; whereas, FSH was significantly increased in 3 weeks but not in 6 weeks. Furthermore, suppression of INHα expression significantly promoted apoptosis by up-regulating Caspase-3, bcl2, INHβB and GDF9 and down regulated Kitl and TGFβRIII genes both at transcriptional and translational levels. Moreover, it also dramatically reduced the progression of G1 phase of cell cycle and the number of cells in S phase as determined by flow cytometer. These results indicate that suppression of INHα expression in RNAi-transgenic mice leads to disruption of normal ovarian regulatory mechanism and causes reproductive deficiencies by promoting cellular apoptosis, arresting cellular progression and altering hormonal signaling.

RNAi-mediated knockdown of IKK1 in transgenic mice using a transgenic construct containing the human H1 promoter

Inhibition of gene expression through siRNAs is a tool increasingly used for the study of gene function in model systems, including transgenic mice. To achieve perdurable effects, the stable expression of siRNAs by an integrated transgenic construct is necessary. For transgenic siRNA expression, promoters transcribed by either RNApol II or III (such as U6 or H1 promoters) can be used. Relatively large amounts of small RNAs synthesis are achieved when using RNApol III promoters, which can be advantageous in knockdown experiments. To study the feasibility of H1 promoter-driven RNAi-expressing constructs for protein knockdown in transgenic mice, we chose IKK1 as the target gene. Our results indicate that constructs containing the H1 promoter are sensitive to the presence of prokaryotic sequences and to transgene position effects, similar to RNApol II promoters-driven constructs. We observed variable expression levels of transgenic siRNA among different tissues and animals and a reduction of up to 80% in IKK1 expression. Furthermore, IKK1 knockdown led to hair follicle alterations. In summary, we show that constructs directed by the H1 promoter can be used for knockdown of genes of interest in different organs and for the generation of animal models complementary to knockout and overexpression models.

In vivo testing of microRNA-mediated gene knockdown in zebrafish

The zebrafish (Danio rerio) has become an attractive model for human disease modeling as there are a large number of orthologous genes that encode similar proteins to those found in humans. The number of tools available to manipulate the zebrafish genome is limited and many currently used techniques are only effective during early development (such as morpholino-based antisense technology) or it is phenotypically driven and does not offer targeted gene knockdown (such as chemical mutagenesis). The use of RNA interference has been met with controversy as off-target effects can make interpreting phenotypic outcomes difficult; however, this has been resolved by creating zebrafish lines that contain stably integrated miRNA constructs that target the desired gene of interest. In this study, we show that a commercially available miRNA vector system with a mouse-derived miRNA backbone is functional in zebrafish and is effective in causing eGFP knockdown in a transient in vivo eGFP sensor assay system. We chose to apply this system to the knockdown of transcripts that are implicated in the human cardiac disorder, Long QT syndrome.