Nanoparticles that deliver triplex-forming peptide nucleic acid molecules correct F508del CFTR in airway epithelium

A new era of targeting cystic fibrosis with non-viral delivery of genomic medicines

Cystic fibrosis (CF) is a complex genetic respiratory disorder that necessitates innovative gene delivery strategies to address the mutations in the gene. This review delves into the promises and challenges of non-viral gene delivery for CF therapy and explores strategies to overcome these hurdles. Several emerging technologies and nucleic acid cargos for CF gene therapy are discussed. Novel formulation approaches including lipid and polymeric nanoparticles promise enhanced delivery through the CF mucus barrier, augmenting the potential of non-viral strategies. Additionally, safety considerations and regulatory perspectives play a crucial role in navigating the path toward clinical translation of gene therapy.

AAV mediated genome engineering with a bypass coagulation factor alleviates the bleeding phenotype in a murine model of hemophilia B

It is crucial to develop a long-term therapy that targets hemophilia A and B, including inhibitor-positive patients. We have developed an Adeno-associated virus (AAV) based strategy to integrate the bypass coagulation factor, activated FVII (murine, mFVIIa) gene into the Rosa26 locus using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 mediated gene-editing. AAV vectors designed for expression of guide RNA (AAV8-gRNA), Cas9 (AAV2 neddylation mutant-Cas9), and mFVIIa (AAV8-mFVIIa) flanked by homology arms of the target locus were validated in vitro. Hemophilia B mice were administered with AAV carrying gRNA, Cas9 (1 × 1011 vgs/mouse), and mFVIIa with homology arms (2 × 1011 vgs/mouse) with appropriate controls. Functional rescue was documented with suitable coagulation assays at various time points. The data from the T7 endonuclease assay revealed a cleavage efficiency of 20-42 %. Further, DNA sequencing confirmed the targeted integration of mFVIIa into the safe-harbor Rosa26 locus. The prothrombin time (PT) assay revealed a significant reduction in PT in mice that received the gene-editing vectors (22 %), and a 13 % decline in mice that received only the AAV-FVIIa when compared to mock treated mice, 8 weeks after vector administration. Furthermore, FVIIa activity in mice that received triple gene-editing vectors was higher (122.5mIU/mL vs 28.8mIU/mL) than the mock group up to 15 weeks post vector administration. A hemostatic challenge by tail clip assay revealed that hemophilia B mice injected with only FVIIa or the gene-editing vectors had significant reduction in blood loss. In conclusion, AAV based gene-editing facilitates sustained expression of coagulation FVIIa and phenotypic rescue in hemophilia B mice.

Harnessing Peptide Nucleic Acids and the Eukaryotic Resolvase MOC1 for Programmable, Precise Generation of Double-Strand DNA Breaks

Programmable site-specific nucleases (SSNs) hold extraordinary promise to unlock myriad gene editing applications in medicine and agriculture. However, developing small and specific SSNs is needed to overcome the delivery and specificity translational challenges of current genome engineering technologies. Structure-guided nucleases have been harnessed to generate double-strand DNA breaks but with limited success and translational potential. Here, we harnessed the power of peptide nucleic acids (PNAs) for site-specific DNA invasion and the generation of localized DNA structures that are recognized and cleaved by the eukaryotic resolvase AtMOC1 from Arabidopsis thaliana. We named this technology PNA-assisted Resolvase-mediated (PNR) editing. We tested the PNR editing concept in vitro and demonstrated its precise target specificity, examined the nucleotide requirement around the PNA invasion for the AtMOC1-mediated cleavage, mapped the AtMOC1-mediated cleavage sites, tested the role of different types and lengths of PNA molecules invasion into dsDNA for the AtMOC1-mediated cleavage, optimized the in vitro PNA invasion and AtMOC1 cleavage conditions such as temperature, buffer conditions, and cleavage time points, and demonstrated the multiplex cleavage for precise fragment release. We discuss the best design parameters for efficient, site-specific in vitro cleavage using PNR editors.

Nanoparticle-based platforms for targeted drug delivery to the pulmonary system as therapeutics to curb cystic fibrosis: A review

Cystic fibrosis (CF) is a genetic disorder of the respiratory system caused by mutation of the Cystic Fibrosis Trans-Membrane Conductance Regulator (CFTR) gene that affects a huge number of people worldwide. It results in difficulty breathing due to a large accumulation of mucus in the respiratory tract, resulting in serious bacterial infections, and subsequent death. Traditional drug-based treatments face hindered penetration at the site of action due to the thick mucus layer. Nanotechnology offers possibilities for developing advanced and effective treatment platforms by focusing on drugs that can penetrate the dense mucus layer, fighting against the underlying bacterial infections, and targeting the genetic cause of the disease. In this review, current nanoparticle-mediated drug delivery platforms for CF, challenges in therapeutics, and future prospects have been highlighted. The effectiveness of the different types of nano-based systems conjugated with various drugs to combat the symptoms and the challenges of treating CF are brought into focus. The toxic effects of these nano-medicines and the various factors that are responsible for their effectiveness are also highlighted.

Antitumor efficacy of a sequence-specific DNA-targeted γPNA-based c-Myc inhibitor

Targeting oncogenes at the genomic DNA level can open new avenues for precision medicine. Significant efforts are ongoing to target oncogenes using RNA-targeted and protein-targeted platforms, but no progress has been made to target genomic DNA for cancer therapy. Here, we introduce a gamma peptide nucleic acid (γPNA)-based genomic DNA-targeted platform to silence oncogenes in vivo. γPNAs efficiently invade the mixed sequences of genomic DNA with high affinity and specificity. As a proof of concept, we establish that γPNA can inhibit c-Myc transcription in multiple cell lines. We evaluate the in vivo efficacy and safety of genomic DNA targeting in three pre-clinical models. We also establish that anti-transcription γPNA in combination with histone deacetylase inhibitors and chemotherapeutic drugs results in robust antitumor activity in cell-line- and patient-derived xenografts. Overall, this strategy offers a unique therapeutic platform to target genomic DNA to inhibit oncogenes for cancer therapy.

The Development of Non-natural Type Nucleoside to Stabilize Triplex DNA Formation against CG and TA Inversion Site

Based on the sequence-specific recognition of target duplex DNA by triplexforming oligonucleotides (TFOs) at the major groove side, the antigene strategy has been exploited as a gene-targeting tool with considerable attention. Triplex DNA is formed via the specific base triplets by the Hoogsteen or reverse Hoogsteen hydrogen bond interaction between TFOs and the homo-purine strand from the target duplex DNA, leading to the established sequence-specificity. However, the presence of inversion sites, which are known as non-natural nucleosides that can form satisfactory interactions with 2'- deoxythymidine (dT) and 2'-deoxycytidine (dC) in TA and CG base pairs in the target homo-purine DNA sequences, drastically restricts the formation of classically stable base triplets and even the triplex DNA. Therefore, the design of non-natural type nucleosides, which can effectively recognize CG or/and TA inversion sites with satisfactory selectivity, should be of great significance to expanding the triplex-forming sequence. Here, this review mainly provides a comprehensive review of the current development of novel nonnatural nucleosides to recognize CG or/and TA inversion sites in triplex DNA formation against double-strand DNA (dsDNA).

Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems. Along with the rapid advancement in RNA biology, including the description of noncoding RNAs as major products of the genome, this success presents an opportunity to highlight the potential of RNA as a therapeutic modality. Here, we review the expanding compendium of RNA-based therapies, their mechanisms of action and examples of application in the lung. The airways provide a convenient conduit for drug delivery to the lungs with decreased systemic exposure. This review will also describe other delivery methods, including local delivery to the pleura and delivery vehicles that can target the lung after systemic administration, each providing access options that are advantageous for a specific application. We present clinical trials of RNA-based therapy in lung disease and potential areas for future directions. This review aims to provide an overview that will bring together researchers and clinicians to advance this burgeoning field.

DNA recognition and induced genome modification by a hydroxymethyl-γ tail-clamp peptide nucleic acid

Peptide nucleic acids (PNAs) can target and stimulate recombination reactions in genomic DNA. We have reported that γPNA oligomers possessing the diethylene glycol γ-substituent show improved efficacy over unmodified PNAs in stimulating recombination-induced gene modification. However, this structural modification poses a challenge because of the inherent racemization risk in O-alkylation of the precursory serine side chain. To circumvent this risk and improve γPNA accessibility, we explore the utility of γPNA oligomers possessing the hydroxymethyl-γ moiety for gene-editing applications. We demonstrate that a γPNA oligomer possessing the hydroxymethyl modification, despite weaker preorganization, retains the ability to form a hybrid with the double-stranded DNA target of comparable stability and with higher affinity than that of the diethylene glycol-γPNA. When formulated into poly(lactic-co-glycolic acid) nanoparticles, the hydroxymethyl-γPNA stimulates higher frequencies (≥ 1.5-fold) of gene modification than the diethylene glycol γPNA in mouse bone marrow cells.

Programmable site-specific DNA double-strand breaks via PNA-assisted prokaryotic Argonautes

Programmable site-specific nucleases promise to unlock myriad applications in basic biology research, biotechnology and gene therapy. Gene-editing systems have revolutionized our ability to engineer genomes across diverse eukaryotic species. However, key challenges, including delivery, specificity and targeting organellar genomes, pose barriers to translational applications. Here, we use peptide nucleic acids (PNAs) to facilitate precise DNA strand invasion and unwinding, enabling prokaryotic Argonaute (pAgo) proteins to specifically bind displaced single-stranded DNA and introduce site-specific double-strand breaks (DSBs) independent of the target sequence. We named this technology PNA-assisted pAgo editing (PNP editing) and determined key parameters for designing PNP editors to efficiently generate programable site-specific DSBs. Our design allows the simultaneous use of multiple PNP editors to generate multiple site-specific DSBs, thereby informing design considerations for potential in vitro and in vivo applications, including genome editing.

Advances in the Cystic Fibrosis Drug Development Pipeline

Cystic fibrosis is a genetic disease that results in progressive multi-organ manifestations with predominance in the respiratory and gastrointestinal systems. The significant morbidity and mortality seen in the CF population has been the driving force urging the CF research community to further advance treatments to slow disease progression and, in turn, prolong life expectancy. Enormous strides in medical advancements have translated to improvement in quality of life, symptom burden, and survival; however, there is still no cure. This review discusses the most current mainstay treatments and anticipated therapeutics in the CF drug development pipeline within the mechanisms of mucociliary clearance, anti-inflammatory and anti-infective therapies, restoration of the cystic fibrosis transmembrane conductance regulator (CFTR) protein (also known as highly effective modulator therapy (HEMT)), and genetic therapies. Ribonucleic acid (RNA) therapy, gene transfer, and gene editing are being explored in the hopes of developing a treatment and potential cure for people with CF, particularly for those not responsive to HEMT.

Cationic Calix[4]arene Vectors to Efficiently Deliver AntimiRNA Peptide Nucleic Acids (PNAs) and miRNA Mimics

One of the most appealing approaches for regulating gene expression, named the "microRNA therapeutic" method, is based on the regulation of the activity of microRNAs (miRNAs), the intracellular levels of which are dysregulated in many diseases, including cancer. This can be achieved by miRNA inhibition with antimiRNA molecules in the case of overexpressed microRNAs, or by using miRNA-mimics to restore downregulated microRNAs that are associated with the target disease. The development of new efficient, low-toxic, and targeted vectors of such molecules represents a key topic in the field of the pharmacological modulation of microRNAs. We compared the delivery efficiency of a small library of cationic calix[4]arene vectors complexed with fluorescent antimiRNA molecules (Peptide Nucleic Acids, PNAs), pre-miRNA (microRNA precursors), and mature microRNAs, in glioma- and colon-cancer cellular models. The transfection was assayed by cytofluorimetry, cell imaging assays, and RT-qPCR. The calix[4]arene-based vectors were shown to be powerful tools to facilitate the uptake of both neutral (PNAs) and negatively charged (pre-miRNAs and mature microRNAs) molecules showing low toxicity in transfected cells and ability to compete with commercially available vectors in terms of delivery efficiency. These results could be of great interest to validate microRNA therapeutics approaches for future application in personalized treatment and precision medicine.

Genome Editing for Cystic Fibrosis

Cystic fibrosis (CF) is a monogenic recessive genetic disorder caused by mutations in the CF Transmembrane-conductance Regulator gene (CFTR). Remarkable progress in basic research has led to the discovery of highly effective CFTR modulators. Now ~90% of CF patients are treatable. However, these modulator therapies are not curative and do not cover the full spectrum of CFTR mutations. Thus, there is a continued need to develop a complete and durable therapy that can treat all CF patients once and for all. As CF is a genetic disease, the ultimate therapy would be in-situ repair of the genetic lesions in the genome. Within the past few years, new technologies, such as CRISPR/Cas gene editing, have emerged as an appealing platform to revise the genome, ushering in a new era of genetic therapy. This review provided an update on this rapidly evolving field and the status of adapting the technology for CF therapy.

A red light-triggered chemical tool for sequence-specific alkylation of G-quadruplex and I-motif DNA

The importance of non-canonical DNA structures such as G-quadruplexes (G4) and intercalating-motifs (iMs) in the fine regulation of a variety of cellular processes has been recently demonstrated. As the crucial roles of these structures are being unravelled, it is becoming more and more important to develop tools that allow targeting these structures with the highest possible specificity. While targeting methodologies have been reported for G4s, this is not the case for iMs, as evidenced by the limited number of specific ligands able to bind the latter and the total absence of selective alkylating agents for their covalent targeting. Furthermore, strategies for the sequence-specific covalent targeting of G4s and iMs have not been reported thus far. Herein, we describe a simple methodology to achieve sequence-specific covalent targeting of G4 and iM DNA structures based on the combination of (i) a peptide nucleic acid (PNA) recognizing a specific sequence of interest, (ii) a pro-reactive moiety enabling a controlled alkylation reaction, and (iii) a G4 or iM ligand orienting the alkylating warhead to the reactive residues. This multi-component system allows for the targeting of specific G4 or iM sequences of interest in the presence of competing DNA sequences and under biologically relevant conditions.

Gene Therapy for Cystic Fibrosis: Recent Advances and Future Prospects

Gene replacement therapies are novel therapeutic approaches that seek to tackle hereditary diseases caused by a congenital deficiency in a particular gene, when a functional copy of a gene can be delivered to the cells and tissues using various delivery systems. To do this, viral particles carrying a functional copy of the gene of interest and various nonviral gene delivery systems, including liposomes, nanoparticles, etc., can be used. In this review, we discuss the state of current knowledge regarding the molecular mechanisms and types of genetic mutations that lead to cystic fibrosis and highlight recent developments in gene therapy that can be leveraged to correct these mutations and to restore the physiological function of the carrier protein transporting sodium and chlorine ions in the airway epithelial cells. Restoration of carrier protein expression could lead to the normalization of ion and water transport across the membrane and induce a decrease in the viscosity of airway surface fluid, which is one of the pathological manifestations of this disease. This review also summarizes recently published preclinical and clinical data for various gene therapies to allow one to make some conclusions about future prospects for gene therapy in cystic fibrosis treatment.

Features of CFTR mRNA and implications for therapeutics development

Cystic fibrosis (CF) is an autosomal recessive disease impacting ∼100,000 people worldwide. This lethal disorder is caused by mutation of the CF transmembrane conductance regulator (CFTR) gene, which encodes an ATP-binding cassette-class C protein. More than 2,100 variants have been identified throughout the length of CFTR. These defects confer differing levels of severity in mRNA and/or protein synthesis, folding, gating, and turnover. Drug discovery efforts have resulted in recent development of modulator therapies that improve clinical outcomes for people living with CF. However, a significant portion of the CF population has demonstrated either no response and/or adverse reactions to small molecules. Additional therapeutic options are needed to restore underlying genetic defects for all patients, particularly individuals carrying rare or refractory CFTR variants. Concerted focus has been placed on rescuing variants that encode truncated CFTR protein, which also harbor abnormalities in mRNA synthesis and stability. The current mini-review provides an overview of CFTR mRNA features known to elicit functional consequences on final protein conformation and function, including considerations for RNA-directed therapies under investigation. Alternative exon usage in the 5'-untranslated region, polypyrimidine tracts, and other sequence elements that influence splicing are discussed. Additionally, we describe mechanisms of CFTR mRNA decay and post-transcriptional regulation mediated through interactions with the 3'-untranslated region (e.g. poly-uracil sequences, microRNAs). Contributions of synonymous single nucleotide polymorphisms to CFTR transcript utilization are also examined. Comprehensive understanding of CFTR RNA biology will be imperative for optimizing future therapeutic endeavors intended to address presently untreatable forms of CF.

Genetics of Cystic Fibrosis: Clinical Implications

Cystic fibrosis (CF) is a multiorgan disease caused by a wide variety of mutations in the cystic fibrosis transmembrane conductance regulator gene. As treatment has progressed from symptom mitigation to targeting of specific molecular defects, genetics has played an important role in identifying the proper precision therapies for each individual. Novel therapeutic approaches are focused on expanding treatment to a greater number of individuals as well as working toward a cure. This review discusses the role of genetics in our understanding of CF with a particular emphasis on how genetics informs the exciting landscape of current and novel CF therapies.

Non-Modulator Therapies: Developing a Therapy for Every Cystic Fibrosis Patient

Cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy brings hope to most patients with cystic fibrosis (CF), but not all. For approximately 12% of CF patients with premature termination codon mutations, large deletions, insertions, and frameshifts, the CFTR modulator therapy is not effective. Many believe that genetic-based therapies such as RNA therapies, DNA therapies, and gene editing technologies will be needed to treat mutations that are not responsive to modulator therapy. Delivery of these therapeutic agents to affected cells is the major challenge that will need to be overcome if we are to harness the power of these emerging therapies for the treatment of CF.

Thyclotides, tetrahydrofuran-modified peptide nucleic acids that efficiently penetrate cells and inhibit microRNA-21

Peptide nucleic acids (PNAs) are promising therapeutic molecules for gene modulation; however, they suffer from poor cell uptake. Delivery of PNAs into cells requires conjugation of the PNA to another large molecule, typically a cell-penetrating peptide or nanoparticle. In this study, we describe a new PNA-based molecule with cyclic tetrahydrofuran (THF) backbone modifications that in some cases considerably improve cell uptake. We refer to these THF-PNA oligomers as thyclotides. With THF groups at every position of the oligomer, the cell uptake of thyclotides targeted to miR-21 is enhanced compared with the corresponding unmodified PNA based on an aminoethylglycine backbone. An optimized thyclotide can efficiently enter cells without the use of cell-penetrating peptides, bind miR-21, its designated microRNA target, decrease expression of miR-21 and increase expression of three downstream targets (PTEN, Cdc25a and KRIT1). Using a plasmid with the PTEN-3'UTR coupled with luciferase, we further confirmed that a miR-21-targeted thyclotide prevents miR-21 from binding to its target RNA. Additionally, the thyclotide shows no cytotoxicity when administered at 200 times its active concentration. We propose that thyclotides be further explored as therapeutic candidates to modulate miRNA levels.

In vivo correction of cystic fibrosis mediated by PNA nanoparticles

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We sought to correct the multiple organ dysfunction of the F508del CF-causing mutation using systemic delivery of peptide nucleic acid gene editing technology mediated by biocompatible polymeric nanoparticles. We confirmed phenotypic and genotypic modification in vitro in primary nasal epithelial cells from F508del mice grown at air-liquid interface and in vivo in F508del mice following intravenous delivery. In vivo treatment resulted in a partial gain of CFTR function in epithelia as measured by in situ potential differences and Ussing chamber assays and correction of CFTR in both airway and GI tissues with no off-target effects above background. Our studies demonstrate that systemic gene editing is possible, and more specifically that intravenous delivery of PNA NPs designed to correct CF-causing mutations is a viable option to ameliorate CF in multiple affected organs.

Prenatal Somatic Cell Gene Therapies: Charting a Path Toward Clinical Applications (Proceedings of the CERSI-FDA Meeting)

We are living in a golden age of medicine in which the availability of prenatal diagnosis, fetal therapy, and gene therapy/editing make it theoretically possible to repair almost any defect in the genetic code. Furthermore, the ability to diagnose genetic disorders before birth and the presence of established surgical techniques enable these therapies to be delivered safely to the fetus. Prenatal therapies are generally used in the second or early third trimester for severe, life-threatening disorders for which there is a clear rationale for intervening before birth. While there has been promising work for prenatal gene therapy in preclinical models, the path to a clinical prenatal gene therapy approach is complex. We recently held a conference with the University of California, San Francisco-Stanford Center of Excellence in Regulatory Science and Innovation, researchers, patient advocates, regulatory (members of the Food and Drug Administration), and other stakeholders to review the scientific background and rationale for prenatal somatic cell gene therapy for severe monogenic diseases and initiate a dialogue toward a safe regulatory path for phase 1 clinical trials. This review represents a summary of the considerations and discussions from these conversations.

CFTR RNA- and DNA-based therapies

This review provides an update on recent developments of RNA- and DNA-based methodologies and their intracellular targets in the context of cystic fibrosis (CF) lung disease. Ultimately, clinical success will require a suitable delivery system, but since the cargo for all these strategies is nucleic acid, it should hopefully be possible to exploit delivery breakthroughs from one study and apply these innovations to other experiments in order to identify the best strategy for everyone with CF. Ultimately, it may be the same approach for everyone, or possibly a number of different strategies tailored to particular mutations or classes/groups of mutations. And whilst the current focus is on CF lung disease, in the longer term the goal is to treat all affected organs in people with CF such as the pancreas, gut, and liver.

Surface conjugation of antibodies improves nanoparticle uptake in bronchial epithelial cells

BACKGROUND

Advances in Molecular Therapy have made gene editing through systemic or topical administration of reagents a feasible strategy to treat genetic diseases in a rational manner. Encapsulation of therapeutic agents in nanoparticles can improve intracellular delivery of therapeutic agents, provided that the nanoparticles are efficiently taken up within the target cells. In prior work we had established proof-of-principle that nanoparticles carrying gene editing reagents can mediate site-specific gene editing in fetal and adult animals in vivo that results in functional disease improvement in rodent models of β-thalassemia and cystic fibrosis. Modification of the surface of nanoparticles to include targeting molecules (e.g. antibodies) holds the promise of improving cellular uptake and specific cellular binding.

METHODS AND FINDINGS

To improve particle uptake for diseases of the airway, like cystic fibrosis, our group tested the impact of nanoparticle surface modification with cell surface marker antibodies on uptake in human bronchial epithelial cells in vitro. Binding kinetics of antibodies (Podoplanin, Muc 1, Surfactant Protein C, and Intracellular Adhesion Molecule-1 (ICAM)) were determined to select appropriate antibodies for cellular targeting. The best target-specific antibody among those screened was ICAM antibody. Surface conjugation of nanoparticles with antibodies against ICAM improved cellular uptake in bronchial epithelial cells up to 24-fold.

CONCLUSIONS

This is a first demonstration of improved nanoparticle uptake in epithelial cells using conjugation of target specific antibodies. Improved binding, uptake or specificity of particles delivered systemically or to the luminal surface of the airway would potentially improve efficacy, reduce the necessary dose and thus safety of administered therapeutic agents. Incremental improvement in the efficacy and safety of particle-based therapeutic strategies may allow genetic diseases such as cystic fibrosis to be cured on a fundamental genetic level before birth or shortly after birth.

γ Peptide Nucleic Acid-Based miR-122 Inhibition Rescues Vascular Endothelial Dysfunction in Mice Fed a High-Fat Diet

The blood levels of microRNA-122 (miR-122) is associated with the severity of cardiovascular disorders, and targeting it with efficient and safer miR inhibitors could be a promising approach. Here, we report the generation of a γ-peptide nucleic acid (γPNA)-based miR-122 inhibitor (γP-122-I) that rescues vascular endothelial dysfunction in mice fed a high-fat diet. We synthesized diethylene glycol-containing γP-122-I and found that its systemic administration counteracted high-fat diet (HFD)-feeding-associated increase in blood and aortic miR-122 levels, impaired endothelial function, and reduced glycemic control. A comprehensive safety analysis established that γP-122-I affects neither the complete blood count nor biochemical tests of liver and kidney functions during acute exposure. In addition, long-term exposure to γP-122-I did not change the overall adiposity, or histology of the kidney, liver, and heart. Thus, γP-122-I rescues endothelial dysfunction without any evidence of toxicity in vivo and demonstrates the suitability of γPNA technology in generating efficient and safer miR inhibitors.

Bone Marrow Transplantation Rescues Monocyte Recruitment Defect and Improves Cystic Fibrosis in Mice

Cystic fibrosis (CF) is an inherited life-threatening disease accompanied by repeated lung infections and multiorgan inflammation that affects tens of thousands of people worldwide. The causative gene, cystic fibrosis transmembrane conductance regulator (CFTR), is mutated in CF patients. CFTR functions in epithelial cells have traditionally been thought to cause the disease symptoms. Recent work has shown an additional defect: monocytes from CF patients show a deficiency in integrin activation and adhesion. Because monocytes play critical roles in controlling infections, defective monocyte function may contribute to CF progression. In this study, we demonstrate that monocytes from CFTR^ΔF508 mice (CF mice) show defective adhesion under flow. Transplanting CF mice with wild-type (WT) bone marrow after sublethal irradiation replaced most (60-80%) CF monocytes with WT monocytes, significantly improved survival, and reduced inflammation. WT/CF mixed bone marrow chimeras directly demonstrated defective CF monocyte recruitment to the bronchoalveolar lavage and the intestinal lamina propria in vivo. WT mice reconstituted with CF bone marrow also show lethality, suggesting that the CF defect in monocytes is not only necessary but also sufficient to cause disease. We also show that monocyte-specific knockout of CFTR retards weight gains and exacerbates dextran sulfate sodium-induced colitis. Our findings show that providing WT monocytes by bone marrow transfer rescues mortality in CF mice, suggesting that similar approaches may mitigate disease in CF patients.

Therapeutic Potential of Chemically Modified, Synthetic, Triplex Peptide Nucleic Acid-Based Oncomir Inhibitors for Cancer Therapy

miRNA-155 (miR-155) is overexpressed in various types of lymphomas and leukemias, suggesting that targeting miR-155 could be a potential platform for the development of precision medicine. Here, we tested the anticancer activity of novel, chemically modified, triplex peptide nucleic acid (PNA)-based antimiRs compared with the current state-of-the-art conventional full-length antimiRs. Next-generation modified PNAs that bound miR-155 by Watson-Crick and Hoogsteen domains possessed superior therapeutic efficacy in vivo and ex vivo compared with conventional full-length anti-miR-155. The efficacy of anti-miR-155 targeting in multiple lymphoma cell lines was comprehensively corroborated by gene expression, Western blot analysis, and cell viability-based functional studies. Finally, preclinical testing in vivo in xenograft mouse models containing lymphoma cell lines demonstrated that treatment with the miR-155-targeting next-generation antimiR resulted in a significant decrease in miR-155 expression, followed by reduced tumor growth. These findings support the effective therapeutic application of chemically modified triplex PNAs to target miR-155 to treat lymphoma. Overall, the present proof-of-concept study further implicates the potential for next-generation triplex gamma PNAs to target other miRNAs for treating cancer. SIGNIFICANCE: This study demonstrates the utility of novel oncomiR inhibitors as cancer therapeutics, providing a new approach for targeting miRNAs and other noncoding RNAs.

The Challenges and Opportunities in the Development of MicroRNA Therapeutics: A Multidisciplinary Viewpoint

microRNAs (miRs) are emerging as attractive therapeutic targets because of their small size, specific targetability, and critical role in disease pathogenesis. However, <20 miR targeting molecules have entered clinical trials, and none progressed to phase III. The difficulties in miR target identification, the moderate efficacy of miR inhibitors, cell type-specific delivery, and adverse outcomes have impeded the development of miR therapeutics. These hurdles are rooted in the functional complexity of miR's role in disease and sequence complementarity-dependent/-independent effects in nontarget tissues. The advances in understanding miR's role in disease, the development of efficient miR inhibitors, and innovative delivery approaches have helped resolve some of these hurdles. In this review, we provide a multidisciplinary viewpoint on the challenges and opportunities in the development of miR therapeutics.

Peptide nucleic acid-dependent artifact can lead to false-positive triplex gene editing signals

Triplex gene editing relies on binding a stable peptide nucleic acid (PNA) sequence to a chromosomal target, which alters the helical structure of DNA to stimulate site-specific recombination with a single-strand DNA (ssDNA) donor template and elicits gene correction. Here, we assessed whether the codelivery of PNA and donor template encapsulated in Poly Lactic-co-Glycolic Acid (PLGA)-based nanoparticles can correct sickle cell disease and x-linked severe combined immunodeficiency. However, through this process we have identified a false-positive PCR artifact due to the intrinsic capability of PNAs to aggregate with ssDNA donor templates. Here, we show that the combination of PNA and donor templates but not either agent alone results in different degrees of aggregation that result in varying but highly reproducible levels of false-positive signal. We have identified this phenomenon in vitro and confirmed that the PNA sequences producing the highest supposed correction in vitro are not active in vivo in both disease models, which highlights the importance of interrogating and eliminating carryover of ssDNA donor templates in assessing various gene editing technologies such as PNA-mediated gene editing.

Functional correction of CFTR mutations in human airway epithelial cells using adenine base editors

Mutations in the CFTR gene that lead to premature stop codons or splicing defects cause cystic fibrosis (CF) and are not amenable to treatment by small-molecule modulators. Here, we investigate the use of adenine base editor (ABE) ribonucleoproteins (RNPs) that convert A•T to G•C base pairs as a therapeutic strategy for three CF-causing mutations. Using ABE RNPs, we corrected in human airway epithelial cells premature stop codon mutations (R553X and W1282X) and a splice-site mutation (3849 + 10 kb C > T). Following ABE delivery, DNA sequencing revealed correction of these pathogenic mutations at efficiencies that reached 38-82% with minimal bystander edits or indels. This range of editing was sufficient to attain functional correction of CFTR-dependent anion channel activity in primary epithelial cells from CF patients and in a CF patient-derived cell line. These results demonstrate the utility of base editor RNPs to repair CFTR mutations that are not currently treatable with approved therapeutics.

Dual-Modality Poly-l-histidine Nanoparticles to Deliver Peptide Nucleic Acids and Paclitaxel for In Vivo Cancer Therapy

Cationic polymeric nanoformulations have been explored to increase the transfection efficiency of small molecules and nucleic acid-based drugs. However, an excessive positive charge density often leads to severe cell and tissue-based toxicity that restricts the clinical translation of cationic polymeric nanoformulations. Herein, we investigate a series of cationic poly(lactic-co-glycolic acid) (PLGA)-histidine-based nanoformulations for enhanced cytoplasmic delivery with minimal toxicity. PLGA/poly-l-histidine nanoparticles show promising physico-biochemical features and transfection efficiency in a series of in vitro and cell culture-based studies. Further, the use of acetone/dichloromethane as a solvent mixture during the formulation process significantly improves the morphology and size distribution of PLGA/poly-l-histidine nanoparticles. PLGA/poly-l-histidine nanoformulations undergo clathrin-mediated endocytosis. A contrast-matched small-angle neutron scattering experiment confirmed poly-l-histidine's distribution on the PLGA nanoformulations. PLGA/poly-l-histidine formulations containing paclitaxel as a small molecule-based drug and peptide nucleic acids targeting microRNA-155 as nucleic acid analog are efficacious in in vitro and in vivo studies. PLGA/poly-l-histidine NPs significantly decrease tumor growth in PNA-155 (∼6 fold) and paclitaxel (∼6.5 fold) treatment groups in a lymphoma cell line derived xenograft mice model without inducing any toxicity. Hence, PLGA/poly-l-histidine nanoformulations exhibit substantial transfection efficiency and are safe to deliver reagents ranging from small molecules to synthetic nucleic acid analogs and can serve as a novel platform for drug delivery.

Peptide nucleic acids and their role in gene regulation and editing

The unique properties of peptide nucleic acid (PNA) makes it a desirable candidate to be used in therapeutic and biotechnological interventions. It has been broadly utilized for numerous applications, with a major focus in regulation of gene expression, and more recently in gene editing. While the classic PNA design has mainly been employed to date, chemical modifications of the PNA backbone and nucleobases provide an avenue to advance the technology further. This review aims to discuss the recent developments in PNA based gene manipulation techniques and the use of novel chemical modifications to improve the current state of PNA mediated gene targeting.

The 2-Aminopyridine Nucleobase Improves Triple-Helical Recognition of RNA and DNA When Used Instead of Pseudoisocytosine in Peptide Nucleic Acids

Pseudoisocytosine (J), a neutral analogue of protonated cytosine, is currently the gold standard modified nucleobase in peptide nucleic acids (PNAs) for the formation of J·G-C triplets that are stable at physiological pH. This study shows that triple-helical recognition of RNA and DNA is significantly improved by using 2-aminopyridine (M) instead of J. The positively charged M forms 3-fold stronger M+·G-C triplets than J with uncompromised sequence selectivity. Replacement of six Js with Ms in a PNA 9-mer increased its binding affinity by ∼2 orders of magnitude. M-modified PNAs prefer binding double-stranded RNA over DNA and disfavor off-target binding to single-stranded nucleic acids. Taken together, the results show that M is a promising modified nucleobase that significantly improves triplex-forming PNAs and may provide breakthrough developments for therapeutic and biotechnology applications.

On the Corner of Models and Cure: Gene Editing in Cystic Fibrosis

Cystic fibrosis (CF) is a severe genetic disease for which curative treatment is still lacking. Next generation biotechnologies and more efficient cell-based and in vivo disease models are accelerating the development of novel therapies for CF. Gene editing tools, like CRISPR-based systems, can be used to make targeted modifications in the genome, allowing to correct mutations directly in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Alternatively, with these tools more relevant disease models can be generated, which in turn will be invaluable to evaluate novel gene editing-based therapies for CF. This critical review offers a comprehensive description of currently available tools for genome editing, and the cell and animal models which are available to evaluate them. Next, we will give an extensive overview of proof-of-concept applications of gene editing in the field of CF. Finally, we will touch upon the challenges that need to be addressed before these proof-of-concept studies can be translated towards a therapy for people with CF.

The NIH Somatic Cell Genome Editing program

The move from reading to writing the human genome offers new opportunities to improve human health. The United States National Institutes of Health (NIH) Somatic Cell Genome Editing (SCGE) Consortium aims to accelerate the development of safer and more-effective methods to edit the genomes of disease-relevant somatic cells in patients, even in tissues that are difficult to reach. Here we discuss the consortium's plans to develop and benchmark approaches to induce and measure genome modifications, and to define downstream functional consequences of genome editing within human cells. Central to this effort is a rigorous and innovative approach that requires validation of the technology through third-party testing in small and large animals. New genome editors, delivery technologies and methods for tracking edited cells in vivo, as well as newly developed animal models and human biological systems, will be assembled-along with validated datasets-into an SCGE Toolkit, which will be disseminated widely to the biomedical research community. We visualize this toolkit-and the knowledge generated by its applications-as a means to accelerate the clinical development of new therapies for a wide range of conditions.

On the Origins of Homology Directed Repair in Mammalian Cells

Over the course of the last five years, expectations surrounding our capacity to selectively modify the human genome have never been higher. The reduction to practice site-specific nucleases designed to cleave at a unique site within the DNA is now centerstage in the development of effective molecular therapies. Once viewed as being impossible, this technology now has great potential and, while cellular and molecular barriers persist to clinical implementations, there is little doubt that these barriers will be crossed, and human beings will soon be treated with gene editing tools. The most ambitious of these desires is the correction of genetic mutations resident within the human genome that are responsible for oncogenesis and a wide range of inherited diseases. The process by which gene editing activity could act to reverse these mutations to wild-type and restore normal protein function has been generally categorized as homology directed repair. This is a catch-all basket term that includes the insertion of short fragments of DNA, the replacement of long fragments of DNA, and the surgical exchange of single bases in the correction of point mutations. The foundation of homology directed repair lies in pioneering work that unravel the mystery surrounding genetic exchange using single-stranded DNA oligonucleotides as the sole gene editing agent. Single agent gene editing has provided guidance on how to build combinatorial approaches to human gene editing using the remarkable programmable nuclease complexes known as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and their closely associated (Cas) nucleases. In this manuscript, we outline the historical pathway that has helped evolve the current molecular toolbox being utilized for the genetic re-engineering of the human genome.

Assisting PNA transport through cystic fibrosis human airway epithelia with biodegradable hybrid lipid-polymer nanoparticles

Cystic fibrosis (CF) is characterized by an airway obstruction caused by a thick mucus due to a malfunctioning Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein. The sticky mucus restricts drugs in reaching target cells limiting the efficiency of treatments. The development of new approaches to enhance drug delivery to the lungs represents CF treatment's main challenge. In this work, we report the production and characterization of hybrid core–shell nanoparticles (hNPs) comprising a PLGA core and a dipalmitoylphosphatidylcholine (DPPC) shell engineered for inhalation. We loaded hNPs with a 7-mer peptide nucleic acid (PNA) previously considered for its ability to modulate the post-transcriptional regulation of the CFTR gene. We also investigated the in vitro release kinetics of hNPs and their efficacy in PNA delivery across the human epithelial airway barrier using an ex vivo model based on human primary nasal epithelial cells (HNEC) from CF patients. Confocal analyses and hNPs transport assay demonstrated the ability of hNPs to overcome the mucus barrier and release their PNA cargo within the cytoplasm, where it can exert its biological function.

Nanoparticles for delivery of agents to fetal lungs

Fetal treatment of congenital lung disease, such as cystic fibrosis, surfactant protein syndromes, and congenital diaphragmatic hernia, has been made possible by improvements in prenatal diagnostic and interventional technology. Delivery of therapeutic agents to fetal lungs in nanoparticles improves cellular uptake. The efficacy and safety of nanoparticle-based fetal lung therapy depends on targeting of necessary cell populations. This study aimed to determine the relative distribution of nanoparticles of a variety of compositions and sizes in the lungs of fetal mice delivered through intravenous and intra-amniotic routes. Intravenous delivery of particles was more effective than intra-amniotic delivery for epithelial, endothelial and hematopoietic cells in the fetal lung. The most effective targeting of lung tissue was with 250nm Poly-Amine-co-Ester (PACE) particles accumulating in 50% and 44% of epithelial and endothelial cells. This study demonstrated that route of delivery and particle composition impacts relative cellular uptake in fetal lung, which will inform future studies in particle-based fetal therapy.

Submonomeric Strategy with Minimal Protection for the Synthesis of C(2)-Modified Peptide Nucleic Acids

A novel synthesis of C(2)-modified peptide nucleic acids (PNAs) is proposed, using a submonomeric strategy with minimally protected building blocks, which allowed a reduction in the required synthetic steps. N(3)-unprotected, d-Lys- and d-Arg-based backbones were used to obtain positively charged PNAs with high optical purity, as inferred from chiral GC measurements. "Chiral-box" PNAs targeting the G12D point mutation of the KRAS gene were produced using this method, showing improved sequence selectivity for the mutated- vs wild-type DNA strand with respect to unmodified PNAs.

Emerging technologies for cystic fibrosis transmembrane conductance regulator restoration in all people with CF

Although effective cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy has the potential to change the lives of many patients with cystic fibrosis (CF), it is unlikely that these drugs will be a game changing therapy for all. There are about 10% of patients with CF who don't produce a mutant protein tomodulate, potentiate, or optimize and for these patients such therapies are unlikely to be of significant benefit. There is a need to develop new therapeutic approaches that can work for this patient population and can advance CF therapies. These new therapies will be genetic-based therapies and each approach will result in functional CFTR protein inpreviously affected CF cells. In this review we will examine the potential of RNA therapies, gene transfer therapies, and gene editing therapies for the treatment of CF as well as the challenges that will need to be facedas we harness the power of these emerging therapies towards a one-time cure.

Rewriting CFTR to cure cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive monogenic disease caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. Although F508del is the most frequent mutation, there are in total 360 confirmed disease-causing CFTR mutations, impairing CFTR production, function and stability. Currently, the only causal treatments available are CFTR correctors and potentiators that directly target the mutant protein. While these pharmacological advances and better symptomatic care have improved life expectancy of people with CF, none of these treatments provides a cure. The discovery and development of programmable nucleases, in particular CRISPR nucleases and derived systems, rekindled the field of CF gene therapy, offering the possibility of a permanent correction of the CFTR gene. In this review we will discuss different strategies to restore CFTR function via gene editing correction of CFTR mutations or enhanced CFTR expression, and address how best to deliver these treatments to target cells.

Therapeutic peptides for the treatment of cystic fibrosis: Challenges and perspectives

Cystic fibrosis (CF) is the most common amongst rare genetic diseases, affecting more than 70.000 people worldwide. CF is characterized by a dysfunctional chloride channel, termed cystic fibrosis conductance regulator (CFTR), which leads to the production of a thick and viscous mucus layer that clogs the lungs of CF patients and traps pathogens, leading to chronic infections and inflammation and, ultimately, lung damage. In recent years, the use of peptides for the treatment of respiratory diseases, including CF, has gained growing interest. Therapeutic peptides for CF include antimicrobial peptides, inhibitors of proteases, and modulators of ion channels, among others. Peptides display unique features that make them appealing candidates for clinical translation, like specificity of action, high efficacy, and low toxicity. Nevertheless, the intrinsic properties of peptides, together with the need of delivering these compounds locally, e.g. by inhalation, raise a number of concerns in the development of peptide therapeutics for CF lung disease. In this review, we discuss the challenges related to the use of peptides for the treatment of CF lung disease through inhalation, which include retention within mucus, proteolysis, immunogenicity and aggregation. Strategies for overcoming major shortcomings of peptide therapeutics will be presented, together with recent developments in peptide design and optimization, including computational analysis and high-throughput screening.

Multifunctional Delivery Systems for Peptide Nucleic Acids

The number of applications of peptide nucleic acids (PNAs)-oligonucleotide analogs with a polyamide backbone-is continuously increasing in both in vitro and cellular systems and, parallel to this, delivery systems able to bring PNAs to their targets have been developed. This review is intended to give to the readers an overview on the available carriers for these oligonucleotide mimics, with a particular emphasis on newly developed multi-component- and multifunctional vehicles which boosted PNA research in recent years. The following approaches will be discussed: (a) conjugation with carrier molecules and peptides; (b) liposome formulations; (c) polymer nanoparticles; (d) inorganic porous nanoparticles; (e) carbon based nanocarriers; and (f) self-assembled and supramolecular systems. New therapeutic strategies enabled by the combination of PNA and proper delivery systems are discussed.

Gene Correction of Point Mutations Using PolyPurine Reverse Hoogsteen Hairpins Technology

Monogenic disorders are often the result of single point mutations in specific genes, leading to the production of non-functional proteins. Different blood disorders such as ß-thalassemia, sickle cell disease, hereditary spherocytosis, Fanconi anemia, and Hemophilia A and B are usually caused by point mutations. Gene editing tools including TALENs, ZFNs, or CRISPR/Cas platforms have been developed to correct mutations responsible for different diseases. However, alternative molecular tools such as triplex-forming oligonucleotides and their derivatives (e.g., peptide nucleic acids), not relying on nuclease activity, have also demonstrated their ability to correct mutations in the DNA. Here, we review the Repair-PolyPurine Reverse Hoogsteen hairpins (PPRHs) technology, which can represent an alternative gene editing tool within this field. Repair-PPRHs are non-modified single-stranded DNA molecules formed by two polypurine mirror repeat sequences linked by a five-thymidine bridge, followed by an extended sequence at one end of the molecule which is homologous to the DNA sequence to be repaired but containing the corrected nucleotide. The two polypurine arms of the PPRH are bound by intramolecular reverse-Hoogsteen bonds between the purines, thus forming a hairpin structure. This hairpin core binds to polypyrimidine tracts located relatively near the target mutation in the dsDNA in a sequence-specific manner by Watson-Crick bonds, thus producing a triplex structure which stimulates recombination. This technology has been successfully employed to repair a collection of mutants of the dhfr and aprt genes within their endogenous loci in mammalian cells and could be suitable for the correction of mutations responsible for blood disorders.

Formulation of PLGA nanoparticles containing short cationic peptide nucleic acids

Peptide nucleic acids (PNAs) have emerged as one of the most versatile tools with a wide range of biomedical applications including antisense, antimiR, antigene, as well as site-specific gene editing. The application and potential of PNAs has been limited due to low solubility and poor cellular uptake. Several strategies have been employed to overcome the aforementioned challenges like conjugation to cationic peptides or nanotechnology to achieve superior transfection efficiency ex vivo and in vivo. Here, we report a detailed procedure optimized in our lab for synthesis of short cationic PNA probes, which exhibit high purity and yield in comparison to full-length PNA oligomers. We also provide step-by-step details of encapsulating short cationic PNA probes in poly (lactic-co-glycolic acid) nanoparticles by double emulsion solvent evaporation technique. 1.Detailed procedure for synthesis of short cationic PNAs with or without fluorophore (dye) conjugation while ensuring high yield and purity.2.Step-by-step details for encapsulation of short cationic PNAs in PLGA nanoparticles via double emulsion solvent evaporation technique.

Walking through the wonder years of artificial DNA: peptide nucleic acid

Peptide Nucleic Acid (PNA) serves as an artificial functional analog of DNA. Being immune to enzymatic degradation and possessing strong affinity towards DNA and RNA, it is an ideal candidate for many medical and biotechnological applications that are of antisense and antigene in nature. PNAs are anticipated to have its application in DNA and RNA detection as well as quantification, to serve as antibacterial and antiviral agents, and silencing gene for developing anticancer strategies. Although, their restricted entry in both eukaryotic and prokaryotic cells limit their applications. In addition, aggregation of PNA in storage containers reduces the quality and quantity of functional PNA that makes it inadequate for their mass production and storage. To overcome these limitations, researchers have modified PNA either by the addition of diverse functional groups at various loci on its backbone, or by synthesizing chimeras with other moieties associated with various delivery agents that aids their entry into the cell. Here, this review article summarizes few of the structural modifications that are performed with PNA, methods used to improve their cellular uptake and shedding light on the applications of PNA in various prospects in biological sciences.

Correction of Airway Stem Cells: Genome Editing Approaches for the Treatment of Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease caused by variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Although CF affects multiple organs, the primary cause of mortality is respiratory failure resulting from poor clearance of hyperviscous secretions and subsequent airway infection. Recently developed CFTR modulators provide significant therapeutic benefit to the majority of CF individuals. However, treatments directed at the underlying cause are needed for the ∼7% of CF patients who are not expected to be responsive to these modulators. Genome editing can restore the native CFTR genetic sequence and function to mutant cells, representing an approach to establish durable physiologic CFTR correction. Although editing the CFTR gene in various airway cell types may transiently restore CFTR activity, effort is focused on editing airway basal stem/progenitor cells, since their correction would allow appropriate and durable expression of CFTR in stem cell-derived epithelial cell types. Substantial progress has been made to directly correct airway basal cells in vitro, theoretically enabling transplantation of autologous corrected cells to regenerate an airway with CFTR functional cells. Another approach to create autologous, gene-edited airway basal cells is derivation of CF donor-specific induced pluripotent stem cells, correction of the CFTR gene, and subsequent directed differentiation to airway basal cells. Further work is needed to translate these advances by developing effective transplantation methods. Alternatively, gene editing in vivo may enable CFTR correction. However, this approach will require robust delivery methods ensuring that basal cells are efficiently targeted and corrected. Recent advances in gene editing-based therapies provide hope that the genetic underpinning of CF can be durably corrected in airway epithelial stem cells, thereby preventing or treating lung disease in all people with CF.

New Directions in Pulmonary Gene Therapy

The lung has long been a target for gene therapy, yet efficient delivery and phenotypic disease correction has remained challenging. Although there have been significant advancements in gene therapies of other organs, including the development of several ex vivo therapies, in vivo therapeutics of the lung have been slower to transition to the clinic. Within the past few years, the field has witnessed an explosion in the development of new gene addition and gene editing strategies for the treatment of monogenic disorders. In this review, we will summarize current developments in gene therapy for cystic fibrosis, alpha-1 antitrypsin deficiency, and surfactant protein deficiencies. We will explore the different gene addition and gene editing strategies under investigation and review the challenges of delivery to the lung.

Next generation miRNA inhibition using short anti-seed PNAs encapsulated in PLGA nanoparticles

Selective inhibition of microRNAs (miRNAs) offers a new avenue for cancer therapeutics. While most of the current anti-miRNA (antimiR) reagents target full length miRNAs, here we investigate novel nanoparticle-delivered short PNA probes containing cationic domains targeting the seed region of the miRNA for effective antimiR therapy. For proof of concept, we tested PNAs targeting miRNA-155 and employed poly(lactic-co-glycolic acid) (PLGA)-based nanoparticle formulation for delivery. A comprehensive evaluation of PLGA nanoparticles (NPs) containing short PNA probes showed significantly superior loading, release profile, and uniform size distribution, compared to conventional non-cationic PNA probes. Confocal microscopy and flow cytometry analyses showed efficient transfection efficiency and uniform distribution of PLGA NPs containing short PNA probes in the cytoplasm. Functional analysis also confirmed efficient miRNA-155 inhibition including an effect on its downstream target proteins. Further, reduced tumor growth was observed after systemic delivery of PLGA nanoparticles containing short PNA probes in vivo in a xenograft mouse model following inhibition of miR-155. There was no evidence of acute or chronic toxicity associated with systemic delivery of PLGA NPs containing short PNA probes in the mice. Overall, in this paper we present a novel antimiR strategy based on PLGA nanoparticle delivered short PNA probes for potential cancer therapy.

Allele-Specific Prevention of Nonsense-Mediated Decay in Cystic Fibrosis Using Homology-Independent Genome Editing

Nonsense-mediated decay (NMD) is a major pathogenic mechanism underlying a diversity of genetic disorders. Nonsense variants tend to lead to more severe disease phenotypes and are often difficult targets for small molecule therapeutic development as a result of insufficient protein production. The treatment of cystic fibrosis (CF), an autosomal recessive disease caused by mutations in the CFTR gene, exemplifies the challenge of therapeutically addressing nonsense mutations in human disease. Therapeutic development in CF has led to multiple, highly successful protein modulatory interventions, yet no targeted therapies have been approved for nonsense mutations. Here, we have designed a CRISPR-Cas9-based strategy for the targeted prevention of NMD of CFTR transcripts containing the second most common nonsense variant listed in CFTR2, W1282X. By introducing a deletion of the downstream genic region following the premature stop codon, we demonstrate significantly increased protein expression of this mutant variant. Notably, in combination with protein modulators, genome editing significantly increases the potentiated channel activity of W1282X-CFTR in human bronchial epithelial cells. Furthermore, we show how the outlined approach can be modified to permit allele-specific editing. The described approach can be extended to other late-occurring nonsense mutations in the CFTR gene or applied as a generalized approach for gene-specific prevention of NMD in disorders where a truncated protein product retains full or partial functionality.