Delivery systems for the direct application of siRNAs to induce RNA interference (RNAi) in vivo

Nucleic acids based integrated macromolecular complexes for SiRNA delivery: Recent advancements

The therapeutic potential of small interfering RNA (siRNA) is monumental, offering a pathway to silence disease-causing genes with precision. However, the delivery of siRNA to target cells in-vivo remains a formidable challenge, owing to degradation by nucleases, poor cellular uptake and immunogenicity. This overview examines recent advancements in the design and application of nucleic acid-based integrated macromolecular complexes for the efficient delivery of siRNA. We dissect the innovative delivery vectors developed in recent years, including lipid-based nanoparticles, polymeric carriers, dendrimer complexes and hybrid systems that incorporate stimuli-responsive elements for targeted and controlled release. Advancements in bioconjugation techniques, active targeting strategies and nanotechnology-enabled delivery platforms are evaluated for their contribution to enhancing siRNA delivery. It also addresses the complex interplay between delivery system design and biological barriers, highlighting the dynamic progress and remaining hurdles in translating siRNA therapies from bench to bedside. By offering a comprehensive overview of current strategies and emerging technologies, we underscore the future directions and potential impact of siRNA delivery systems in personalized medicine.

Plant-Derived Biomaterials and Their Potential in Cardiac Tissue Repair

Cardiovascular disease remains the leading cause of mortality worldwide. The inability of cardiac tissue to regenerate after an infarction results in scar tissue formation, leading to cardiac dysfunction. Therefore, cardiac repair has always been a popular research topic. Recent advances in tissue engineering and regenerative medicine offer promising solutions combining stem cells and biomaterials to construct tissue substitutes that could have functions similar to healthy cardiac tissue. Among these biomaterials, plant-derived biomaterials show great promise in supporting cell growth due to their inherent biocompatibility, biodegradability, and mechanical stability. More importantly, plant-derived materials have reduced immunogenic properties compared to popular animal-derived materials (e.g., collagen and gelatin). In addition, they also offer improved wettability compared to synthetic materials. To date, limited literature is available to systemically summarize the progression of plant-derived biomaterials in cardiac tissue repair. Herein, this paper highlights the most common plant-derived biomaterials from both land and marine plants. The beneficial properties of these materials for tissue repair are further discussed. More importantly, the applications of plant-derived biomaterials in cardiac tissue engineering, including tissue-engineered scaffolds, bioink in 3D biofabrication, delivery vehicles, and bioactive molecules, are also summarized using the latest preclinical and clinical examples.

Biofunctionalized Decellularized Tissue-Engineered Heart Valve with Mesoporous Silica Nanoparticles for Controlled Release of VEGF and RunX2-siRNA against Calcification

The goal of tissue-engineered heart valves (TEHV) is to replace normal heart valves and overcome the shortcomings of heart valve replacement commonly used in clinical practice. However, calcification of TEHV is the major bottleneck to break for both clinical workers and researchers. Endothelialization of TEHV plays a crucial role in delaying valve calcification by reducing platelet adhesion and covering the calcified spots. In the present study, we loaded RunX2-siRNA and VEGF into mesoporous silica nanoparticles and investigated the properties of anti-calcification and endothelialization in vitro. Then, the mesoporous silica nanoparticle was immobilized on the decellularized porcine aortic valve (DPAV) by layer self-assembly and investigated the anti-calcification and endothelialization. Our results demonstrated that the mesoporous silica nanoparticles delivery vehicle demonstrated good biocompatibility, and a stable release of RunX2-siRNA and VEGF. The hybrid decellularized valve exhibited a low hemolysis rate and promoted endothelial cell proliferation and adhesion while silencing RunX2 gene expression in valve interstitial cells, and the hybrid decellularized valve showed good mechanical properties. Finally, the in vivo experiment showed that the mesoporous silica nanoparticles delivery vehicle could enhance the endothelialization of the hybrid valve. In summary, we constructed a delivery system based on mesoporous silica to biofunctionalized TEHV scaffold for endothelialization and anti-calcification.

Research Advances of Injectable Functional Hydrogel Materials in the Treatment of Myocardial Infarction

Myocardial infarction (MI) has become one of the serious diseases threatening human life and health. However, traditional treatment methods for MI have some limitations, such as irreversible myocardial necrosis and cardiac dysfunction. Fortunately, recent endeavors have shown that hydrogel materials can effectively prevent negative remodeling of the heart and improve the heart function and long-term prognosis of patients with MI due to their good biocompatibility, mechanical properties, and electrical conductivity. Therefore, this review aims to summarize the research progress of injectable hydrogel in the treatment of MI in recent years and to introduce the rational design of injectable hydrogels in myocardial repair. Finally, the potential challenges and perspectives of injectable hydrogel in this field will be discussed, in order to provide theoretical guidance for the development of new and effective treatment strategies for MI.

Tetraspanin 5 (TSPAN5), a Novel Gatekeeper of the Tumor Suppressor DLC1 and Myocardin-Related Transcription Factors (MRTFs), Controls HCC Growth and Senescence

Simple Summary

Hepatocellular carcinoma (HCC) ranks second among the leading causes of cancer-related death. Since current therapeutic options are very limited, a deeper understanding of the molecular mechanisms underlying the tumor onset and progression of HCC holds great potential for improved therapeutic options. Although it has been shown that deleted in liver cancer 1 (DLC1) acts as a tumor suppressor whose allele is lost in 50% of liver cancers, alterations in gene expression initiated by DLC1 loss have not yet been the primary focus of liver cancer research. To identify novel gene targets that allow for a personalized medicine approach for HCC therapy, we performed gene expression profiling for HepG2 cells stably expressing DLC1shRNA. We provide evidence that TSPAN5 is required for HCC growth, migration and invasion, and dissected the underlying molecular mechanisms involving myocardin-related transcription factors. Thus, TSPAN5 represents a novel therapeutic target for the treatment of HCC characterized by DLC1 loss.

Abstract

Human hepatocellular carcinoma (HCC) is among the most lethal and common cancers in the human population, and new molecular targets for therapeutic intervention are urgently needed. Deleted in liver cancer 1 (DLC1) was originally identified as a tumor suppressor gene in human HCC. DLC1 is a Rho-GTPase-activating protein (RhoGAP) which accelerates the return of RhoGTPases to an inactive state. We recently described that the restoration of DLC1 expression induces cellular senescence. However, this principle is not amenable to direct therapeutic targeting. We therefore performed gene expression profiling for HepG2 cells depleted of DLC1 to identify druggable gene targets mediating the effects of DLC1 on senescence induction. This approach revealed that versican (VCAN), tetraspanin 5 (TSPAN5) and N-cadherin (CDH2) were strongly upregulated upon DLC1 depletion in HCC cells, but only TSPAN5 affected the proliferation of HCC cells and human HCC. The depletion of TSPAN5 induced oncogene-induced senescence (OIS), mediated by the p16^INK4a/pRb pathways. Mechanistically, silencing TSPAN5 reduced actin polymerization and thereby myocardin-related transcription factor A- filamin A (MRTF-A-FLNA) complex formation, resulting in decreased expression of MRTF/SRF-dependent target genes and senescence induction in vitro and in vivo. Our results identify TSPAN5 as a novel druggable target for HCC.

Complex fibroblast response to glucocorticoids may underlie variability of clinical efficacy in the vocal folds

Similar to the hypertrophic scar and keloids, the efficacy of glucorticoids (GC) for vocal fold injury is highly variable. We previously reported dexamethasone enhanced the pro-fibrotic effects of transforming growth factor (TGF)-β as a potential mechanism for inconsistent clinical outcomes. In the current study, we sought to determine the mechanism(s) whereby GCs influence the fibrotic response and mechanisms underlying these effects with an emphasis on TGF-β and nuclear receptor subfamily 4 group A member 1 (NR4A1) signaling. Human VF fibroblasts (HVOX) were treated with three commonly-employed GCs+ /-TGF-β1. Phosphorylation of the glucocorticoid receptor (GR:NR3C1) and activation of NR4A1 was analyzed by western blotting. Genes involved in the fibrotic response, including ACTA2, TGFBR1, and TGFBR2 were analyzed by qPCR. RNA-seq was performed to identify global changes in gene expression induced by dexamethasone. GCs enhanced phosphorylation of GR at Ser211 and TGF-β-induced ACTA2 expression. Dexamethasone upregulated TGFBR1, and TGFBR2 in the presence of TGF-β1 and increased active NR4A1. RNA-seq results confirmed numerous pathways, including TGF-β signaling, affected by dexamethasone. Synergistic pro-fibrotic effects of TGF-β were observed across GCs and appeared to be mediated, at least partially, via upregulation of TGF-β receptors. Dexamethasone exhibited diverse regulation of gene expression including NR4A1 upregulation consistent with the anti-fibrotic potential of GCs.

Skin Delivery of siRNA Using Sponge Spicules in Combination with Cationic Flexible Liposomes

We report the topical administration of sponge Haliclona sp. Spicules (SHS) combined with cationic flexible liposomes (CFL) to increase the delivery of small interfering RNA (siRNA) into viable skin cells in vitro and in vivo. SHS can be applied topically as novel microneedles to overcome skin barrier by creating plenty of new microchannels in stratum corneum. Subsequently, well-designed CFL can be also utilized topically as nanocarriers to overcome skin cells membrane by delivering siRNA to skin deep layers through these microchannels and thereby facilitating their cell internalization. The topical application of SHS in combination with CFL (0.05% of lipids, w/v), referred to as CFL(0.05%), enhanced siRNA skin penetration in vitro by 72.95 ± 2.97-fold compared to control group (p < 0.001). Further, the topical application of SHS in combination with CFL(0.05%) on female BALB/c mice skin resulted in 29.21% ± 1.41% of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) knockdown at all application area in vivo, which was not significantly different from the GAPDH protein knockdown rate in the subcutaneous injection center. However, the high knockdown rate only appears in the vicinity (<0.5 cm) of the injection center. In sum, this study provides a promising strategy of topical delivery of siRNA by the combined used of SHS and well-designed CFL.

Osteoblasts mineralization and collagen matrix are conserved upon specific Col1a2 silencing

Classical osteogenesis imperfecta (OI) is an inherited rare brittle bone disease caused by dominant mutations in the COL1A1 or COL1A2 genes, encoding for the α chains of collagen type I. The definitive cure for the disease will require a gene therapy approach, aimed to correct or suppress the mutant allele. Interestingly, individuals lacking α2(I) chain and synthetizing collagen α1(I)₃ homotrimers do not show bone phenotype, making appealing a bone specific COL1A2 silencing approach for OI therapy. To this aim, three different Col1a2-silencing RNAs (siRNAs), −3554, −3825 and −4125, selected at the 3′-end of the murine Col1a2 transcript were tested in vitro and in vivo. In murine embryonic fibroblasts Col1a2-siRNA-3554 was able to efficiently and specifically target the Col1a2 mRNA and to strongly reduce α2(I) chain expression. Its efficiency and specificity were also demonstrated in primary murine osteoblasts, whose mineralization was preserved. The efficiency of Col1a2-siRNA-3554 was proved also in vivo. Biphasic calcium phosphate implants loaded with murine mesenchymal stem cells were intramuscularly transplanted in nude mice and injected with Col1a2-siRNA-3554 three times a week for three weeks. Collagen α2 silencing was demonstrated both at mRNA and protein level and Masson's Trichrome staining confirmed the presence of newly formed collagen matrix. Our data pave the way for further investigation of Col1a2 silencing and siRNA delivery to the bone tissue as a possible strategy for OI therapy.

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Identification of a specific and efficient Col1a2 siRNA

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Silencing of Col1a2 allows osteoblasts mineralization.

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Col1a2 silencing is not impairing matrix deposition in vivo.

Small interfering RNAs (siRNAs) in cancer therapy: a nano-based approach

Cancer is one of the most complex diseases that has resulted in multiple genetic disorders and cellular abnormalities. Globally, cancer is the most common health concern disease that is affecting human beings. Great efforts have been made over the past decades in biology with the aim of searching novel and more efficient tools in therapy. Thus, small interfering RNAs (siRNAs) have been considered one of the most noteworthy developments which are able to regulate gene expression following a process known as RNA interference (RNAi). RNAi is a post-transcriptional mechanism that involves the inhibition of gene expression through promoting cleavage on a specific area of a target messenger RNA (mRNA). This technology has shown promising therapeutic results for a good number of diseases, especially in cancer. However, siRNA therapeutics have to face important drawbacks in therapy including stability and successful siRNA delivery in vivo. In this regard, the development of effective siRNA delivery systems has helped addressing these issues by opening novel therapeutic windows which have allowed to build up important advances in Nanomedicine. In this review, we discuss the progress of siRNA therapy as well as its medical application via nanoparticle-mediated delivery for cancer treatment.

Silencing of spinal Trpv1 attenuates neuropathic pain in rats by inhibiting CAMKII expression and ERK2 phosphorylation

Accumulating evidence suggests a potential role of transient receptor potential vanilloid 1 (TRPV1) channels in inflammatory and cancer-related pain. However, the role of TRPV1 in the maintenance of neuropathic pain remains elusive. The current study investigated the effects of transient Trpv1 gene silencing using a small interference RNA (siRNA) on neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rats. Seven days after CCI, the TRPV1 siRNA was intrathecally administered (5 µg/15 µl, once daily for 2 days). TRPV1 and Ca²⁺/calmodulin-dependent protein kinase II (CAMKII) expression and extracellular signal-regulated kinase (ERK) phosphorylation in the spinal cord were detected using western blotting. The thresholds to mechanical and thermal stimuli were determined before and after intrathecal TRPV1 siRNA administration. TRPV1 and CAMKII expression and ERK2 phosphorylation in the spinal cord were upregulated after CCI. Intrathecal administration of the TRPV1 siRNA not only attenuated behavioural hyperalgesia but also reduced the expression of TRPV1 and CAMKII, as well as ERK2 phosphorylation. Based on these results, silencing of the TRPV1 gene in the spinal cord attenuates the maintenance of neuropathic pain by inhibiting CAMKII/ERK2 activation and suggests that TRPV1 represents a potential target in pain therapy.

AKT2 siRNA delivery with amphiphilic-based polymeric micelles show efficacy against cancer stem cells

Development of RNA interference-based therapies with appropriate therapeutic window remains a challenge for advanced cancers. Because cancer stem cells (CSC) are responsible of sustaining the metastatic spread of the disease to distal organs and the progressive gain of resistance of advanced cancers, new anticancer therapies should be validated specifically for this subpopulation of cells. A new amphihilic-based gene delivery system that combines Pluronic^® F127 micelles with polyplexes spontaneously formed by electrostatic interaction between anionic siRNA and cationic polyethylenimine (PEI) 10K, was designed (PM). Resultant PM gather the requirements for an efficient and safe transport of siRNA in terms of its physicochemical characteristics, internalization capacity, toxicity profile and silencing efficacy. PM were loaded with a siRNA against AKT2, an important oncogene involved in breast cancer tumorigenesis, with a special role in CSC malignancy. Efficacy of siAKT2-PM was validated in CSC isolated from two breast cancer cell lines: MCF-7 and Triple Negative MDA-MB-231 corresponding to an aggressive subtype of breast cancer. In both cases, we observed significant reduction on cell invasion capacity and strong inhibition of mammosphere formation after treatment. These results prompt AKT2 inhibition as a powerful therapeutic target against CSC and pave the way to the appearance of more effective nanomedicine-based gene therapies aimed to prevent CSC-related tumor recurrence.

Activation of cyclin D1 affects mitochondrial mass following traumatic brain injury

Cell cycle activation has been associated with varying types of neurological disorders including brain injury. Cyclin D1 is a critical modulator of cell cycle activation and upregulation of Cyclin D1 in neurons contributes to the pathology associated with traumatic brain injury (TBI). Mitochondrial mass is a critical factor to maintain the mitochondrial function, and it can be regulated by different signaling cascades and transcription factors including NRF1. However, the underlying mechanism of how TBI leads to impairment of mitochondrial mass following TBI remains obscure. Our results indicate that augmentation of CyclinD1 attenuates mitochondrial mass formation following TBI. To elucidate the molecular mechanism, we found that Cyclin D1 interacts with a transcription factor NRF1 in the nucleus and prevents NRF1's interaction with p300 in the pericontusional cortex following TBI. As a result, the acetylation level of NRF1 was decreased, and its transcriptional activity was attenuated. This event leads to a loss of mitochondrial mass in the pericontusional cortex following TBI. Intranasal delivery of Cyclin D1 RNAi immediately after TBI rescues transcriptional activation of NRF1 and recovers mitochondrial mass after TBI.

Role of MicroRNAs in Renal Parenchymal Diseases-A New Dimension

Since their discovery in 1993, numerous microRNAs (miRNAs) have been identified in humans and other eukaryotic organisms, and their role as key regulators of gene expression is still being elucidated. It is now known that miRNAs not only play a central role in the processes that ensure normal development and physiology, but they are often dysregulated in various diseases. In this review, we present an overview of the role of miRNAs in normal renal development and physiology, in maladaptive renal repair after injury, and in the pathogenesis of renal parenchymal diseases. In addition, we describe methods used for their detection and their potential as therapeutic targets. Continued research on renal miRNAs will undoubtedly improve our understanding of diseases affecting the kidneys and may also lead to new therapeutic agents.

hTERT gene knockdown enhances response to radio- and chemotherapy in head and neck cancer cell lines through a DNA damage pathway modification

The aim of the study was to analyze the effect of hTERT gene knockdown in HNSCC cells by using novel in vitro models of head and neck cancer (HNSCC), as well as improving its personalized therapy. To obtain the most efficient knockdown siRNA, shRNA-bearing lentiviral vectors were used. The efficiency of hTERT silencing was verified with qPCR, Western blot, and immunofluorescence staining. Subsequently, the type of cell death and DNA repair mechanism induction after hTERT knockdown was assessed with the same methods, followed by flow cytometry. The effect of a combined treatment with hTERT gene knockdown on Double-Strand Breaks levels was also evaluated by flow cytometry. Results showed that the designed siRNAs and shRNAs were effective in hTERT knockdown in HNSCC cells. Depending on a cell line, hTERT knockdown led to a cell cycle arrest either in phase G1 or phase S/G2. Induction of apoptosis after hTERT downregulation with siRNA was observed. Additionally, hTERT targeting with lentiviruses, followed by cytostatics administration, led to induction of apoptosis. Interestingly, an increase in Double-Strand Breaks accompanied by activation of the main DNA repair mechanism, NER, was also observed. Altogether, we conclude that hTERT knockdown significantly contributes to the efficacy of HNSCC treatment.

MicroRNAs-103/107 Regulate Autophagy in the Epidermis

We have shown that microRNAs-103 and -107 (miRs-103/107) positively regulate end-stage autophagy by ensuring dynamin activity in cultured keratinocytes. Most work in end-stage autophagy has been conducted using in vitro model systems. In vivo regulation of end-stage autophagy in epidermis remains unknown. Here, we used antagomirs to subcutaneously knock down miR-107 in the skin; conversely, we delivered miR-107 mimic subcutaneously via in vivo transfection to increase this miR. We found that antagomir-107 treatment in epidermis: (i) depleted endogenous miR-107; (ii) increased GFP-LC3 puncta in epidermal basal layers of GFP-LC3 transgenic mice, indicative of an accumulation of autophagosomes; (iii) inhibited LC3 turnover and increased p62, suggesting an inhibition of autophagy flux; and (iv) increased phosphorylated dynamin (p-dynamin, an inactive form), a key enzyme in end-stage autophagy. Conversely, miR-107 mimic treatment in mouse epidermis: decreased GFP-LC3 puncta in basal layer, as well as p62 protein levels; and diminished p-dynamin, indicative of activation of this enzyme. In human epidermal keratinocytes, antagos-103/107 cause the formation of large vacuoles and an increase in p-dynamin, which can be rescued by inhibition of protein kinase C pathway. Collectively, these results suggest that the miR-103/107 family has a critical role in regulating end-stage autophagy in mouse epidermis via PLD1/2-protein kinase C-dynamin pathway.

Nanoparticle delivery of RNA-based therapeutics to alter the vocal fold tissue response to injury

OBJECTIVES/HYPOTHESIS

Our laboratory and others hypothesized that Smad3 is a principle mediator of the fibrotic phenotype in the vocal folds (VFs), and we further posited that alteration of Smad3 expression through short interfering (si)RNA holds therapeutic promise, yet delivery remains challenging. To address this issue, we employed a novel synthetic oligomer, lipitoid, complexed with siRNA to improve stability and cellular uptake with the goal of increased efficiency of RNA-based therapeutics.

STUDY DESIGN

In vitro study and in vivo animal model.

METHODS

In vitro, lipitoid cytotoxicity was quantified via colorimetric and LIVE/DEAD assays in immortalized human VF fibroblasts and primary rabbit VF fibroblasts. In addition, optimal incubation interval and solution for binding siRNA to lipitoid for intracellular delivery were determined. In vivo, a rabbit model of VF injury was employed to evaluate Smad3 knockdown following locally injected lipitoid-complexed siRNA.

RESULTS

In vitro, lipitoid did not confer additional toxicity compared to commercially available reagents. In addition, 20-minute incubation in 1× phosphate-buffered saline resulted in maximal Smad3 knockdown. In vivo, Smad3 expression increased following VF injury. This response was significantly reduced in injured VFs at 4 and 24 hours following injection (P = .035 and .034, respectively).

CONCLUSIONS

The current study is the first to demonstrate targeted gene manipulation in the VFs as well as the potential utility of lipitoid for localized delivery of genetic material in vivo. Ideally, these data will serve as a platform for future investigation regarding the functional implications of therapeutic gene manipulation in the VFs.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E178-E183, 2018.

Oral delivery of curcumin via porous polymeric nanoparticles for effective ulcerative colitis therapy

Oral drug delivery has been considered as a promising strategy for ulcerative colitis (UC) therapy. Here, an emulsion solvent evaporation technique was employed to prepare non-porous curcumin (CUR)-loaded polymeric nanoparticles (NPs) and porous CUR-loaded polymeric NPs in the absence or presence of ammonium bicarbonate. The resultant CUR-loaded NPs (non-porous NPs and porous NPs) had a desirable mean particle size of around 260 nm with a narrow size distribution, a uniform pore size distribution, slightly negative-charged surface, high encapsulation efficiency and controlled drug release capacity. In vitro experiments indicated that Raw 264.7 macrophages exhibited time-dependent accumulation profiles of NPs during the initial 2 h of co-incubation. Furthermore, we found that porous NPs inhibited the secretion of the main pro-inflammatory cytokines (TNF-α, IL-6 and IL-12) and the production of reactive oxygen species much more efficiently than non-porous NPs. Most importantly, in vivo studies demonstrated that oral administered porous NPs had a superior therapeutic efficiency in alleviating UC compared with non-porous NPs. The results collectively suggest that porous polymeric NPs can be exploited as efficient oral drug carriers for UC treatment.

Preliminary study of a novel transfection modality for in vivo siRNA delivery to vocal fold fibroblasts

OBJECTIVE

An obstacle to clinical use of RNA-based gene suppression is instability and inefficiency of current delivery modalities. Nanoparticle delivery likely holds great promise, but the kinetics and transfection conditions must be optimized prior to in vivo utility. We investigated a RNA nanoparticle complex incorporating a lipitoid transfection reagent in comparison to a commercially available reagent.

STUDY DESIGN

In vitro.

METHODS

We investigated which variables influence transfection efficiency of lipitoid oligomers and a commercially available reagent across species, in vitro. These variables included duration, dose, and number of administrations, as well as serum and media conditions. The target gene was Smad3, a signaling protein in the transforming growth factor-β cascade implicated in fibroplasia in the vocal folds and other tissues.

RESULTS

The two reagents suppressed Smad3 mRNA for up to 96 hours; lipitoid performed favorably and comparably. Both compounds yielded 60% to 80% mRNA knockdown in rat, rabbit, and human vocal fold fibroblasts (P < 0.05 relative to control). Dose and number of administrations played a significant role in gene suppression (P < 0.05). Suppression was more dose-sensitive with lipitoid. At a constant siRNA concentration, a 50% decrease in gene expression was observed in response to a five-fold increase in lipitoid concentration. Increased number of administrations enhanced gene suppression, ∼45% decrease between one and four administrations. Neither serum nor media type altered efficiency.

CONCLUSION

Lipitoid effectively knocked down Smad3 expression across multiple transfection conditions. These preliminary data are encouraging, and lipitoid warrants further investigation with the goal of clinical utility.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E231-E237, 2017.

Short interfering RNAs targeting a vampire-bat related rabies virus phosphoprotein mRNA

The aim of this study was to assess the in vitro and in vivo effects of short-interfering RNAs (siRNAs) against rabies virus phosphoprotein (P) mRNA in a post-infection treatment for rabies as an extension of a previous report (Braz J Microbiol. 2013 Nov 15;44(3):879-82). To this end, rabies virus strain RABV-4005 (related to the Desmodus rotundus vampire bat) were used to inoculate BHK-21 cells and mice, and the transfection with each of the siRNAs was made with Lipofectamine-2000™. In vitro results showed that siRNA 360 was able to inhibit the replication of strain RABV-4005 with a 1log decrease in virus titter and 5.16-fold reduction in P mRNA, 24h post-inoculation when compared to non-treated cells. In vivo, siRNA 360 was able to induce partial protection, but with no significant difference when compared to non-treated mice. These results indicate that, despite the need for improvement for in vivo applications, P mRNA might be a target for an RNAi-based treatment for rabies.

Sustained delivery of siRNA/PEI complex from in situ forming hydrogels potently inhibits the proliferation of gastric cancer

Background

Gastric cancer remains a major cause of mortality and morbidity worldwide. In recent years, gene-based therapeutic strategies were confirmed promising in cancer inhibition and attracted great attention. RNA interference (RNAi) is a powerful tool for gene therapy and has been widely employed to aid in treatment for various diseases, especially cancers. However, effective delivery of small interfering RNA (siRNA) to target cells in vivo remains a challenge for that it is prone to degradation and only lasts a few days in rapidly dividing cells.

Methods

Due to its biocompatibility and well-established safety profile, collagen represents a favourable matrix for in-site drug delivery. In the study, collagen hydrogel was used as carriers to test the feasibility of localized and sustained delivery of Id1-targeted siRNA for in vivo gastric cancer inhibition. To enhance the siRNA delivery, cationic polyethylenimine (PEI) was further emplored for scallold modification. The efficacy of siRNA delivery and cancer inhibition were evaluated with multimodality of mehods in vitro and in vivo.

Results

Our results showed that addition of polyethylenimine (PEI) to collagen can facilitate entry of Id1-siRNA into target cells, prolong the silencing effect, and further inhibit tumor growth both in vitro and in vivo.

Conclusion

This collagen-based delivery system may facilitate the pathogenesis elucidation and design of effective therapies against gastric cancer.

Suppression of tumor growth in lung cancer xenograft model mice by poly(sorbitol-co-PEI)-mediated delivery of osteopontin siRNA

Small interfering RNA (siRNA)-mediated gene silencing represents a promising strategy for treating diseases such as cancer; however, specific gene silencing requires an effective delivery system to overcome the instability and low transfection efficiency of siRNAs. To address this issue, a polysorbitol-based transporter (PSOT) was prepared by low molecular weight branched polyethylenimine (bPEI) crosslinked with sorbitol diacrylate (SDA). Osteopontin (OPN) gene, which is highly associated with non-small cell lung cancer (NSCLC) was targeted by siRNA therapy using siRNA targeting OPN (siOPN). Characterization study confirmed that PSOT formed compact complexes with siOPN and protected siOPN against degradation by RNase. PSOT/siOPN complexes demonstrated low cytotoxicity and enhanced transfection efficiency in vitro, suggesting that this carrier may be suitable for gene silencing. In the A549 and H460 lung cancer cell lines, PSOT/siOPN complexes demonstrated significant silencing efficiency at both RNA and protein levels. To study in vivo tumor growth suppression, two lung cancer cell-xenograft mouse models were prepared and PSOT/siOPN complexes were delivered into the mice through intravenous injection. The siOPN-treated groups demonstrated significantly reduced OPN expression at both the RNA and protein levels as well as suppression of tumor volume and weight. Taken together, siOPN delivery using PSOT may present an effective and novel therapeutic system for lung cancer treatment.

Nucleic acid-based approaches to STAT inhibition

Silencing of abnormally activated genes can be accomplished in a highly specific manner using nucleic acid based approaches. The focus of this review includes the different nucleic acid based inhibition strategies such as antisense oligodeoxynucleotides, small interfering RNA (siRNA), dominant-negative constructs, G-quartet oligonucleotides and decoy oligonucleotides, their mechanism of action and the effectiveness of these approaches to targeting the STAT (signal transducer and activator of transcription) proteins in cancer. Among the STAT proteins, especially STAT3, followed by STAT5, are the most frequently activated oncogenic STATs, which have emerged as plausible therapeutic cancer targets. Both STAT3 and STAT5 have been shown to regulate numerous oncogenic signaling pathways including proliferation, survival, angiogenesis and migration/invasion.

Vertically integrated translational studies of PDX1 as a therapeutic target for pancreatic cancer via a novel bifunctional RNAi platform

RNA interference (RNAi) represents a powerful, new tool for scientific investigation as well as a promising new form of targeted gene therapy, with applications currently in clinical trials. Bifunctional short hairpin RNA (shRNA) are synthetic RNAi molecules, engineered to utilize multiple endogenous RNAi pathways to specifically silence target genes. Pancreatic and duodenal homeobox 1 (PDX1) is a key regulator of pancreatic development, β-cell differentiation, normal β-cell function and pancreatic cancer. Our aim is to review the process of identifying PDX1 as a specific, potential RNAi target in pancreatic cancer, as well as the underlying mechanisms and various forms of RNAi, with subsequent testing and development of PDX1-targeted bifunctional shRNA therapy.

Assessment of drug delivery and anticancer potentials of nanoparticles-loaded siRNA targeting STAT3 in lung cancer, in vitro and in vivo

Activation of signal transducer and activator of transcription3 (STAT3) is a hallmark of several types of cancer. Failure to inhibit STAT3 expression by injection of siRNA for STAT3 directly to Balb/c mice led us to adopt alternative means. We formulated nanoparticle-based encapsulation of siRNA (NsiRNA) with polyethylenimine (PEI) and poly(lactide-co-glycolide) (PLGA) and characterized them. The siRNA treated and NsiRNA-treated cells were subjected separately to different assay systems. We also checked if NsiRNA could cross the blood brain barrier (BBB). Cell viability reduced dramatically in A549 cells after NsiRNA administration (23.89% at 24 h), thereby implicating considerable silencing of STAT3 by NsiRNA, but not after siRNA administration. Compared to controls, a significant decrease in expression of IL-6 and the angiogenic factor (VEGF) and increase in Caspase 3 activity was observed with corresponding regression in tumor growth in mice treated with NsiRNA. NsiRNA induced apoptosis of cells and arrested cells at G1/G0 stage, both in vitro and in vivo. Apoptosis was also verified by Annexin-V-FITC/Propidium-iodide staining. NsiRNA could cross blood brain barrier. Overall results revealed PEI-PLGA to be a promising carrier for delivery of siRNA targeting STAT3 expression, which can be utilized as an effective strategy for cancer therapy.

Topical delivery of siRNA into skin using SPACE-peptide carriers

Short-interfering RNAs (siRNAs) offer a potential tool for the treatment of skin disorders. However, applications of siRNA for dermatological conditions are limited by their poor permeation across the stratum corneum of the skin and low penetration into the skin's viable cells. In this study, we report the use of SPACE-peptide in combination with a DOTAP-based ethosomal carrier system to enhance skin delivery of siRNA. A DOTAP-based SPACE Ethosomal System significantly enhanced siRNA penetration into porcine skin in vitro by 6.3±1.7-fold (p<0.01) with an approximately 10-fold (p<0.01) increase in epidermis accumulation of siRNA compared to that from an aqueous solution. Penetration of siRNA was also enhanced at the cellular level. Internalization of SPACE-peptide occurred in a concentration dependent manner marked by a shift in intracellular distribution from punctate spots to diffused cytoplasmic staining at a peptide concentration of 10mg/mL. In vitro delivery of GAPDH siRNA by SPACE peptide led to 83.3±3.0% knockdown relative to the control. In vivo experiments performed using female BALB/C mice also confirmed the efficacy of DOTAP-SES in delivering GAPDH-siRNA into skin. Topical application of DOTAP-SES on mice skin resulted in 63.2%±7.7% of GAPDH knockdown, which was significantly higher than that from GAPDH-siRNA PBS (p<0.05). DOTAP-SES formulation reported here may open new opportunities for cutaneous siRNA delivery.

Preclinical development of siRNA therapeutics: towards the match between fundamental science and engineered systems

The evolution of synthetic RNAi faces the paradox of interfering with the human biological environment. Due to the fact that all cell physiological processes can be target candidates, silencing a precise biological pathway could be challenging if target selectivity is not properly addressed. Molecular biology has provided scientific tools to suppress some of the most critical issues in gene therapy, while setting the standards for siRNA clinical application. However, the protein down-regulation through the mRNA silencing is intimately related to the sequence-specific siRNA ability to interact accurately with the potential target. Moreover, its in vivo biological fate is highly dependent on the successful design of a vehicle able to overcome both extracellular and intracellular barriers. Anticipating a great deal of innovation, crucial to meet the challenges involved in the RNAi therapeutics, the present review intends to build up a synopsis on the delivery strategies currently developed.

FROM THE CLINICAL EDITOR

This review discusses recent progress and pertinent limiting factors related to the use of siRNA-s as efficient protein-specific "silencing" agents, focusing on targeted delivery not only to cells of interest, but to the proper intracellular destination.

Ammonium and guanidinium dendron-carbon nanotubes by amidation and click chemistry and their use for siRNA delivery

A series of multi-walled carbon nanotube (MWCNT) conjugates is described, functionalized with different dendrons bearing positive charges at their termini (i.e. ammonium or guanidinium groups). The dendrimeric units are anchored to the nanotube scaffolds using two orthogonal synthetic approaches, amidation and click reactions. The final nanohybrids are characterized by complementary analytical techniques, while their ability to interact with siRNA is investigated by means of agarose gel electrophoresis. The demonstration of the cell uptake capacity, the low cytotoxicity, and the ability of these cationic conjugates to silence cytotoxic genes suggests them to be promising carriers for genetic material.

Gene silencing in crustaceans: from basic research to biotechnologies

Gene silencing through RNA interference (RNAi) is gaining momentum for crustaceans, both in basic research and for commercial development. RNAi has proven instrumental in a growing number of crustacean species, revealing the functionality of novel crustacean genes essential among others to development, growth, metabolism and reproduction. Extensive studies have also been done on silencing of viral transcripts in crustaceans, contributing to the understanding of the defense mechanisms of crustaceans and strategies employed by viruses to overcome these. The first practical use of gene silencing in aquaculture industry has been recently achieved, through manipulation of a crustacean insulin-like androgenic gland hormone. This review summarizes the advancements in the use of RNAi in crustaceans, and assesses the advantages of this method, as well as the current hurdles that hinder its large-scale practice.

Systemic siRNA Delivery via Peptide-Tagged Polymeric Nanoparticles, Targeting PLK1 Gene in a Mouse Xenograft Model of Colorectal Cancer

Polymeric nanoparticles were developed from a series of chemical reactions using chitosan, polyethylene glycol, and a cell-targeting peptide (CP15). The nanoparticles were complexed with PLK1-siRNA. The optimal siRNA loading was achieved at an N : P ratio of 129.2 yielding a nanoparticle size of >200 nm. These nanoparticles were delivered intraperitoneally and tested for efficient delivery, cytotoxicity, and biodistribution in a mouse xenograft model of colorectal cancer. Both unmodified and modified chitosan nanoparticles showed enhanced accumulation at the tumor site. However, the modified chitosan nanoparticles showed considerably, less distribution in other organs. The relative gene expression as evaluated showed efficient delivery of PLK1-siRNA (0.5 mg/kg) with 50.7 ± 19.5% knockdown (P = 0.031) of PLK1 gene. The in vivo data reveals no systemic toxicity in the animals, when tested for systemic inflammation and liver toxicity. These results indicate a potential of using peptide-tagged nanoparticles for systemic delivery of siRNA at the targeted tumor site.

Mannosylated bioreducible nanoparticle-mediated macrophage-specific TNF-α RNA interference for IBD therapy

The application of RNA interference (RNAi) for inflammatory bowel disease (IBD) therapy has been limited by the lack of non-cytotoxic, efficient and targetable small interfering RNA (siRNA) carriers. TNF-α is the major pro-inflammatory cytokine mainly secreted by macrophages during IBD. Here, a mannosylated bioreducible cationic polymer (PPM) was synthesized and further spontaneously assembled nanoparticles (NPs) assisted by sodium triphosphate (TPP). The TPP-PPM/siRNA NPs exhibited high uniformity (polydispersity index = 0.004), a small particle size (211-275 nm), excellent bioreducibility, and enhanced cellular uptake. Additionally, the generated NPs had negative cytotoxicity compared to control NPs fabricated by branched polyethylenimine (bPEI, 25 kDa) or Oligofectamine (OF) and siRNA. In vitro gene silencing experiments revealed that TPP-PPM/TNF-α siRNA NPs with a weight ratio of 40:1 showed the most efficient inhibition of the expression and secretion of TNF-α (approximately 69.9%, which was comparable to the 71.4% obtained using OF/siRNA NPs), and its RNAi efficiency was highly inhibited in the presence of mannose (20 mm). Finally, TPP-PPM/siRNA NPs showed potential therapeutic effects on colitis tissues, remarkably reducing TNF-α level. Collectively, these results suggest that non-toxic TPP-PPM/siRNA NPs can be exploited as efficient, macrophage-targeted carriers for IBD therapy.

Polyethylenimines for siRNA and miRNA delivery in vivo

The discovery of RNA interference (RNAi) as a naturally occurring mechanism for gene knockdown has attracted considerable attention toward the use of small interfering RNAs (siRNAs) for therapeutic purposes. Likewise, microRNAs (miRNAs) have emerged as important cellular regulators of gene expression, and their pathological underexpression allows for novel therapeutic strategies ('miRNA replacement therapy'). To address issues related to the instability, charge, and molecular weight of small RNA molecules, nanoparticle formulations have been explored for their in vivo application. Polyethylenimines (PEIs) are positively charged, linear, or branched polymers that are able to form nanoscale complexes with small RNAs, leading to RNA protection, cellular delivery, and intracellular release. This review highlights the important properties of various PEIs with regard to their use for in vivo RNA delivery. PEI modifications for increased efficacy, altered pharmacokinetic properties, improved biocompatibility and, upon covalent coupling of ligands, targeted delivery are described. An overview of various modified PEIs and a comprehensive list of representative studies using PEI-based siRNA or miRNA delivery in vivo are given.

MMP-2 mediates local degradation and remodeling of collagen by annulus fibrosus cells of the intervertebral disc

INTRODUCTION

Degeneration of the intervertebral disc (IVD) is characterized by marked degradation and restructuring of the annulus fibrosus (AF). Although several matrix metalloproteinases (MMPs) have been found to be more prevalent in degenerate discs, their coordination and function within the context of the disease process are still not well understood. In this study, we sought to determine whether MMP-2 is associated with degenerative changes in the AF and to identify the manner by which AF cells use MMP-2.

METHODS

Two established animal models of disc degeneration, static compression and transannular needle puncture of rodent caudal discs, were examined for MMP-2 immunopositivity. With lentiviral transduction of an shRNA expression cassette, we screened and identified an effective shRNA sequence for generating stable RNA interference to silence MMP-2 expression in primary rat AF cells. Gelatin films were used to compare gelatinase activity and spatial patterns of degradation between transduced cells, and both noninfected and nonsense shRNA controls. The functional significance of MMP-2 was determined by assessing the ability for cells to remodel collagen gels.

RESULTS

Both static compression and 18-g annular puncture of rodent caudal discs stimulated an increase in MMP-2 activity with concurrent lamellar disorganization in the AF, whereas 22-g and 26-g needle injuries did not. To investigate the functional role of MMP-2, we established lentivirus-mediated RNAi to induce stable knockdown of transcript levels by as much as 88%, and protein levels by as much as 95% over a 10-day period. Culturing transduced cells on gelatin films confirmed that MMP-2 is the primary functional gelatinase in AF cells, and that MMP-2 is used locally in regions immediately around AF cells. In collagen gels, transduced cells demonstrated an inability to remodel collagen matrices.

CONCLUSIONS

Our study indicates that increases in MMP-2 observed in human degenerate discs are mirrored in experimentally induced degenerative changes in rodent animal models. AF cells appear to use MMP-2 in a very directed fashion for local matrix degradation and collagen remodeling. This suggests that MMP-2 may have a functionally significant role in the etiology of degenerative disc disease and could be a potential therapeutic target.

MEMS-enabled implantable drug infusion pumps for laboratory animal research, preclinical, and clinical applications

Innovation in implantable drug delivery devices is needed for novel pharmaceutical compounds such as certain biologics, gene therapy, and other small molecules that are not suitable for administration by oral, topical, or intravenous routes. This invasive dosing scheme seeks to directly bypass physiological barriers presented by the human body, release the appropriate drug amount at the site of treatment, and maintain the drug bioavailability for the required duration of administration to achieve drug efficacy. Advances in microtechnologies have led to novel MEMS-enabled implantable drug infusion pumps with unique performance and feature sets. In vivo demonstration of micropumps for laboratory animal research and preclinical studies include acute rapid radiolabeling, short-term delivery of nanomedicine for cancer treatment, and chronic ocular drug dosing. Investigation of MEMS actuators, valves, and other microstructures for on-demand dosing control may enable next generation implantable pumps with high performance within a miniaturized form factor for clinical applications.

Anti-HIV-1 nanotherapeutics: promises and challenges for the future

The advent of highly active antiretroviral therapy (HAART) has significantly improved the prognosis for human immunodeficiency virus (HIV)-infected patients, however the adverse side effects associated with prolonged HAART therapy use continue. Although systemic viral load can be undetectable, the virus remains sequestered in anatomically privileged sites within the body. Nanotechnology-based delivery systems are being developed to target the virus within different tissue compartments and are being evaluated for their safety and efficacy. The current review outlines the various nanomaterials that are becoming increasingly used in biomedical applications by virtue of their robustness, safety, multimodality, and multifunctionality. Nanotechnology can revolutionize the field of HIV medicine by not only improving diagnosis, but also by improving delivery of antiretrovirals to targeted regions in the body and by significantly enhancing the efficacy of the currently available antiretroviral medications.

Evaluation of asymmetric immunoliposomal nanoparticles for cellular uptake

Effective and targeted in vivo delivery of polynucleotide therapeutics is the key for the treatment of many diseases. Asymmetric immunoliposomes can be used as vehicles to deliver polynucleotides effectively because the two leaflets of the bilayer can have different compositions, which enhance the delivery capacity. The formation and in vitro cellular uptake of asymmetric immunoliposomes containing polynucleotide cargoes were studied here. Maleimide-functionalised DSPE-PEG (2000) were incorporated into the outer leaflet to produce asymmetric liposomes capable of covalently attaching antibodies. Thiolated antibodies from both human and rabbit origin were conjugated to produce asymmetric pendant-type immunoliposomes that retain their specificity towards detection antibodies through the formation process. Human IgG-conjugated asymmetric immunoliposomes were readily internalised (>20 per cell) by macrophage, HEPG2, and CV-1 monkey kidney cells. The cells internalised the liposomal nanoparticles by the endocytic pathway. The immunoliposome-encapsulated endosomes were intact for at least 5 days and sequestered the plasmid from expression by the cell.

Grand challenges in modulating the immune response with RNAi nanomedicines

RNAi is a ubiquitous and highly specific, endogenous, evolutionarily conserved mechanism of gene silencing. RNAi holds great promise as a novel therapeutic modality. Despite the rapid progress in the understanding and utilization of RNAi in vitro, the application of RNAi in vivo has been met with great difficulties, mainly in the delivery of these molecules into specific cell types. Here, we describe the major systemic nanomedicine platforms that have been developed. Focus is given to the development of new strategies to target subsets of leukocytes, which are among the most difficult cells to transduce with RNAi. Finally, we discuss the hurdles and potential opportunities for in vivo manipulation of the immune response utilizing RNAi nanomedicines.

Facial amphipathic deoxycholic acid-modified polyethyleneimine for efficient MMP-2 siRNA delivery in vascular smooth muscle cells

Clinical applications of RNA interference-based therapeutics such as small interfering RNAs (siRNAs) have been limited mainly due to low intracellular delivery efficiency in vitro and in vivo. In this study, facially amphipathic deoxycholic acid (DA)-modified polyethyleneimine (PEI(1.8)) (DA-PEI(1.8)) was synthesized and used as a potent carrier system for siRNA targeted against matrix metalloproteinase-2 (MMP-2) to inhibit the migration of vascular smooth muscle cells (SMCs), which is the major pathomechanism in the development of atherosclerosis and restenosis after arterial injury. A representative facial amphipathic bile acid DA having a high membrane permeability was conjugated to the terminal amine groups of the low molecular weight PEI(1.8) via amide bonds. The DA-PEI(1.8) conjugates formed self-assembled nanoparticles with siRNA molecules in an aqueous phase and the DA-PEI(1.8)/siRNA polyplexes became stabilized and condensed as particle incubation time increased from 0 to 4h. Both cellular internalization and target gene silencing were enhanced as the DA-PEI(1.8)/siRNA polyplexes stabilized. When vascular SMCs were transfected with MMP-2 siRNA, the DA-PEI(1.8)/siRNA polyplex formulation led to a significant decrease in MMP-2 gene expression, resulting in the suppression of cell migration. These results suggest that the DA-PEI(1.8)/MMP-2 siRNA delivery system may be useful in anti-restenotic treatment for various vasculoproliferative disorders such as atherosclerosis, in-stent restenosis, and vein graft failure.

Delivery of intracellular-acting biologics in pro-apoptotic therapies

The recent elucidation of molecular regulators of apoptosis and their roles in cellular oncogenesis has motivated the development of biomacromolecular anticancer therapeutics that can activate intracellular apoptotic signaling pathways. Pharmaceutical scientists have employed a variety of classes of biologics toward this goal, including antisense oligodeoxynucleotides, small interfering RNA, proteins, antibodies, and peptides. However, stability in the in vivo environment, tumor-specific biodistribution, cell internalization, and localization to the intracellular microenvironment where the targeted molecule is localized pose significant challenges that limit the ability to directly apply intracellular-acting, pro-apoptotic biologics for therapeutic use. Thus, approaches to improve the pharmaceutical properties of therapeutic biomacromolecules are of great significance and have included chemically modifying the bioactive molecule itself or formulation with auxiliary compounds. Recently, promising advances in delivery of pro-apoptotic biomacromolecular agents have been made using tools such as peptide "stapling", cell penetrating peptides, fusogenic peptides, liposomes, nanoparticles, smart polymers, and synergistic combinations of these components. This review will discuss the molecular mediators of cellular apoptosis, the respective mechanisms by which these mediators are dysregulated in cellular oncogenesis, the history and development of both nucleic-acid and amino-acid based drugs, and techniques to achieve intracellular delivery of these biologics. Finally, recent applications where pro-apoptotic functionality has been achieved through delivery of intracellular-acting biomacromolecular drugs will be highlighted.

RNA interference targeting survivin exerts antitumoral effects in vitro and in established glioma xenografts in vivo

Malignant glioma represents the most common primary adult brain tumor in Western industrialized countries. Despite aggressive treatment modalities, the median survival duration for patients with glioblastoma multiforme (GBM), the highest grade malignant glioma, has not improved significantly over past decades. One promising approach to deal with GBM is the inactivation of proteins essential for survival or progression of glioma cells by means of RNA interference (RNAi) techniques. A likely candidate for an RNAi therapy of gliomas is the inhibitor of apoptosis protein survivin. Survivin is involved in 2 main cellular processes-cell division and inhibition of apoptosis. We show here that stable RNAi of survivin induced polyploidy, apoptosis, and impaired proliferation of human U343-MG, U373-MG, H4, and U87-MG cells and of primary glioblastoma cells. Proteome profiler arrays using U373-MG cells identified a novel set of differentially expressed genes upon RNAi-mediated survivin knockdown. In particular, the death receptor TRAIL R2/DR5 was strongly upregulated in survivin-depleted glioma cells, inducing an enhanced cytotoxic response of allogeneic human NK cells. Moreover, an experimental in vivo therapy using polyethylenimine (PEI)/siRNA complexes for survivin knockdown efficiently blocked tumor growth of established subcutaneous U373-MG tumors and enhanced survival of NMRI(nu/nu) mice orthopically transplanted with U87-MG cells. We conclude that survivin is functionally relevant in gliomas and that PEI-mediated exogenous delivery of siRNA targeting survivin is a promising strategy for glioblastoma therapy.

Evaluation of the ability of two transfection reagents to deliver small interfering RNA molecules to equine and guinea pig cartilage in vitro

OBJECTIVE

To evaluate 2 commercially available transfection reagents for transfection efficiency and distribution of small interfering RNA (siRNA) molecules to chondrocytes in monolayer cultures and full-thickness cartilage explants from guinea pigs and horses.

SAMPLE

Cartilage explants from 5 one-month-old and 3 adult guinea pigs and 5 adult clinically normal horses.

PROCEDURES

Monolayer chondrocytes and uniform cartilage explants were exposed to 1 of 2 siRNA transfection complexes according to manufacturers' protocols (1μM [1×]). Additionally, monolayer chondrocytes were exposed to 2× the suggested amount of a proprietary siRNA molecule. Full-thickness cartilage explants were treated with 1× (1μM), 2× (2μM), and 4× (4μM) or 1× (0.13μM), 4× (0.52μM), and 8× (1.04μM) the recommended concentrations of the proprietary siRNA and the cationic liposome siRNA, respectively, in equivalent media volumes. Use of fluorescent siRNA duplexes allowed quantification of transfected cells via flow cytometry and direct visualization of the depth and distribution of in situ transfection via fluorescent microscopy.

RESULTS

With both transfection reagents, > 90% of monolayer chondrocytes were transfected. In explants, only use of the proprietary molecule achieved > 50% transfection efficiency, whereas use of the cationic liposome achieved < 20%. Only the proprietary molecule-treated cartilage consistently contained fluorescent cells throughout all zones; the cationic liposome-transfected chondrocytes were restricted to explant surfaces.

CONCLUSIONS AND CLINICAL RELEVANCE

Robust transfection of chondrocytes in monolayer was achieved with both reagents, but only use of the proprietary molecule attained effective full-thickness transfection of explants that may allow relevant transcript reduction via RNAi.