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Research Technology / RNA Interference

Current siRNA Targets in Atherosclerosis and Aortic Aneurysm

Abstract: Atherosclerosis (ATH) and aortic aneurysms (AA) remain challenging chronic diseases that confer high morbidity and mortality despite advances in medical, interventional, and surgical care. RNA interference represents a promising technology that may be utilized to silence genes contributing to ATH and AA. Despite positive results in preclinical and some clinical feasibility studies, challenges such as target/sequence validation, tissue specificity, transfection efficiency, and mitigation of unwanted off-target effects remain to be addressed. In this review the most current targets and some novel approaches in siRNA delivery are being discussed. Due to the plethora of investigated targets, only studies published between 2010 and 2014 were included. ... Read more

Effects of AFP Gene Silencing on Apoptosis and Proliferation of a Hepatocellular Carcinoma Cell Line

Abstract: Alpha fetoprotein (AFP) is an oncoembryonal protein that is highly expressed in the majority of hepatocellular carcinomas. Previous studies have shown that AFP may be involved in multiple cell growth regulating, differentiating, and immunosuppressive activities. We investigated the effects of AFP gene silencing by siRNA on apoptosis and proliferation of hepatocellular carcinoma cell line EGHC-9901, which highly expresses AFP and may serve as an ideal model for investigation of AFP functions. siRNA expressing plasmid targeting the AFP gene was first established and subsequently transfected into hepatocellular carcinoma cell line EGHC-9901; cells were then divided into three groups: siRNA-afp, transfected with AFP-siRNA; siRNA-beta-actin, transfected with siRNA-beta-actin as the positive group; and vector control, transfected with empty vector as the blank control group. After G418 positive clone selection for a couple of weeks, Western blot and RT (reverse transcription)-PCR assay demonstrated that AFP expression was almost completely inhibited by siRNA-afp, which indicates that siRNA expressing plasmid targeting the AFP gene has been successfully established. Furthermore, MTT (methyl thiazolyl tetrazelium) assay showed that cells transfected with siRNA-afp proliferated at a significantly lower speed than the other two groups and flat plate clone formation assay also witnessed less clones with diameters of more than 75 μm in siRNA-afp immunofluorescence indicating that the apoptosis rate of cells transfected with siRNA-afp was significantly higher than the other two groups. Furthermore, flow cytometry manifested approximately 20% more cells of siRNA-afp within G1 phase than those of the negative group, indicating that inhibition of AFP expression may cause G1 phase arrest. Finally, Western blot and RT-PCR assay demonstrated that siRNA-afp induced a higher expression of caspase-3 than the other two groups whereas there was no difference in expression of caspase-8, caspase-9, and Bcl-2 between the three groups. ... Read more

Optimizing siRNA Delivery to the Genital Mucosa

Abstract: RNA interference (RNAi) describes a highly conserved pathway, present in eukaryotic cells, for regulating gene expression. Small stretches of double-stranded RNA, termed small interfering RNAs (siRNAs), utilize this pathway to bind homologous mRNA, resulting in site-specific mRNA cleavage and subsequent protein degradation. The ubiquitous presence of the RNAi machinery, combined with its specificity and efficacy, makes it an attractive mechanism for reducing aberrant gene expression in therapeutic settings. However, a major obstacle to utilizing RNAi in the clinic is siRNA delivery. Administered siRNAs must make contact with the appropriate cell types and, following internalization, gain access to the cytosol where the RNAi machinery resides. This must be achieved so that silencing is maximized, whilst minimizing any undesirable off-target effects. Recently, the utility of siRNAs as a microbicide, usually applied to the genital mucosa for preventing transmission of sexually transmitted diseases including HIV-1 and HSV-2, has been investigated. In this review we will describe these studies and discuss potential strategies for improving gene silencing. ... Read more

Gene Therapy for Vision Loss -- Recent Developments

Abstract: Retinal gene therapy mediated by adeno-associated virus (AAV) based gene transfer was recently proven to improve photoreceptor function in one form of inherited retinal blinding disorder associated with mutations in the RPE65 gene. Several clinical trials are currently ongoing, and more than 30 patients have been treated to date. Even though only a very limited number of patients will greatly benefit from this still experimental treatment protocol, the technique itself has been shown to be safe and will likely be used in other retinal disorders in the near future. A canine model for achromatopsia has been treated successfully as well as mouse models for different forms of Leber congenital amaurosis (LCA). For patients with autosomal dominant retinitis pigmentosa (adRP), a combined gene knockdown and gene addition therapy is being developed using RNA interference to block mRNA of the mutant allele. For those patients suffering from RP with unknown mutations, an AAV based transfer of bacterial forms of rhodopsin in the central retina might be an option to reactivate residual cones in the future. ... Read more

The Therapeutic Potential of microRNA Modulation

Abstract: microRNAs are endogenous small non-coding RNAs that regulate gene expression by interfering with translation or stability of target transcripts. The importance and varied functions of microRNAs are illustrated by the diverse phenotypes, including disease, that arise when microRNAs are mutated or improperly expressed. The association of microRNA dysfunction with disease phenotypes has given rise to the idea that selective modulation of microRNAs could alter the course of disease. With the recent demonstration that inhibition of miR-122 reduces viral load in HCV-infected chimpanzees, microRNA modulators are no longer merely theoretical, but have become strong candidate therapeutics. Here we review the evidence for microRNA dysfunction in human disease, as well as recent examples of microRNA modulation that provided therapeutic benefit. ... Read more

HIV-1 Latency and Eradication of Long-term Viral Reservoirs

Abstract: HIV-1 infection is characterized by a continuous viral replication throughout the illness that can be controlled to some extent by effective treatment. Early during primary infection, latent reservoirs where the virus remains hidden in metabolically inert cells are established. These reservoirs are responsible for a low-rate viral replication that can be observed even during effective treatment and are a major obstacle for the complete eradication of the infection. This low-rate viral replication also comes from anatomical sites where drug penetration is limited and only a suboptimal drug concentration can be achieved. Further understanding of the mechanisms underlying HIV-1 latency is of primary importance to develop new strategies that ensure the complete destruction of reservoirs and, therefore, the eradication of the infection. ... Read more

The Road to Therapeutic RNA Interference (RNAi): Tackling the 800 Pound siRNA Delivery Gorilla

Abstract: If those of us privileged enough to have the opportunity to work towards curing human diseases had the power to design the ideal therapeutic molecule, the question would be what selection criteria would we choose? Arguably, at the top of the list would be four mandatory properties: specificity, potency, tolerability, and universality. So it should come as no surprise the momentum associated with the field of small interfering RNA (siRNA)-induced RNA Interference (RNAi) therapeutics has gained strength, as these molecules have shown exceptional promise in fulfilling all of these requirements. Unfortunately, siRNAs are too large, too charged, and too rigid to passively diffuse across the cellular membrane and thereby require a delivery system to enter cells. Thus, since its conception of working in human cells, siRNA delivery remains THE 800 Pound Gorilla in the room. The main complication yet to overcome is engineering delivery systems that are safe and efficient in systemically delivering siRNA molecules to the diseased tissue and across the cellular membrane of target cells. Currently, encapsulating the siRNA in nanoparticle and liposomal systems has risen to become the standard of delivery approaches. While generally speaking these delivery platforms offer significant advancements, our laboratory is committed to generating alternative siRNA delivery technologies that avoid nanoparticle packaging and allow siRNA molecules to be delivered as single, soluble entities. This brief review discusses the first of these technologies, a Peptide Transduction Domain-dsRNA Binding Domain (PTD-DRBD) fusion protein that avidly binds to the siRNA backbone to mask the negative charge and uses the PTD for macromolecular cellular delivery. ... Read more

MicroManipulating Viral-based Therapeutics

Abstract: Despite the social stigma and manufacturing hurdles that come with using viruses as therapeutic tools, the molecular specificity offered by these bugs makes them too attractive to ignore. Still largely based on vaccines, viral vectors offer exciting tools to treat cancer or deliver specific genetic payloads to a desired tissue. Unfortunately, early clinical trials utilizing such vectors have been plagued with poor performance or even clinical toxicity most commonly associated with spurious genetic regulation and/or replication of the vector. Past efforts to control for unwanted toxicity have focused on modification of the receptor or use of tissue-specific genetic elements that added specificity to the transcriptional induction of the gene(s) of interest. While this has had some success, engineering receptors to control viral tropism often fails or results in a loss of replicative fitness. In addition, the use of tissue-specific promoter elements not only restricts the vector that can be used, bona fide small promoter elements are often not available for the desired target. With the caveats of viral vector-based therapeutics largely centered on a lack of in vivo control, the recent success of exploiting microRNA expression to limit viral tropism may breathe new life into the field. ... Read more

Magnetic Nanoparticles: Prospects in Cancer Imaging and Therapy

Abstract: Nanotechnology based on the use of submicronic particles of inorganic and/or organic origin has the potential to revolutionalize the clinical management of cancer; the possibility of real time monitoring of disease progression and effects of therapy is now real. Especially, iron oxide super paramagnetic nanoparticles have shown clinical utility in cancer imaging and drug delivery and some formulations are now FDA-approved for use in the clinic. The prospects of magnetic nanoparticles in cancer imaging and treatment are reviewed. ... Read more

Role of Nanotechnology in HIV/AIDS Treatment: Potential to Overcome the Viral Reservoir Challenge

Abstract: Insufficient concentrations and very short residence time of the anti-retroviral agents at the cellular and anatomical sites are among major factors that contribute to the failure of eradicating HIV from reservoirs and the development of multidrug resistance against antiretroviral agents. In recent years, nanotechnology-based drug delivery systems have shown remarkable ability to overcome many of the same anatomical and physiological barriers and deliver the therapeutic agents locally at the site of systemic diseases such as cancer. ... Read more

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