Immunogenicity of intrathecal plasmid gene delivery: cytokine release and effects on transgene expression

Highly efficient CRISPR-mediated genome editing through microfluidic droplet cell mechanoporation

Clustered regularly interspaced short palindromic repeats (CRISPR)-based editing tools have transformed the landscape of genome editing. However, the absence of a robust and safe CRISPR delivery method continues to limit its potential for therapeutic applications. Despite the emergence of various methodologies aimed at addressing this challenge, issues regarding efficiency and editing operations persist. We introduce a microfluidic gene delivery system, called droplet cell pincher (DCP), designed for highly efficient and safe genome editing. This approach combines droplet microfluidics with cell mechanoporation, enabling encapsulation and controlled passage of cells and CRISPR systems through a microscale constriction. Discontinuities created in cell and nuclear membranes upon passage facilitate the rapid CRISPR-system internalization into the nucleus. We demonstrate the successful delivery of various macromolecules, including mRNAs (~98%) and plasmid DNAs (~91%), using this platform, underscoring the versatility of the DCP and leveraging it to achieve successful genome engineering through CRISPR-Cas9 delivery. Our platform outperforms electroporation, the current state-of-the-art method, in three key areas: single knockouts (~6.5-fold), double knockouts (~3.8-fold), and knock-ins (~3.8-fold). These results highlight the potential of our platform as a next-generation tool for CRISPR engineering, with implications for clinical and biological cell-based research.

Navigating the prime editing strategy to treat cardiovascular genetic disorders in transforming heart health

INTRODUCTION

After understanding the genetic basis of cardiovascular disorders, the discovery of prime editing (PE), has opened new horizons for finding their cures. PE strategy is the most versatile editing tool to change cardiac genetic background for therapeutic interventions. The optimization of elements, prediction of efficiency, and discovery of the involved genes regulating the process have not been completed. The large size of the cargo and multi-elementary structure makes the in vivo heart delivery challenging.

AREAS COVERED

Updated from recent published studies, the fundamentals of the PEs, their application in cardiology, potentials, shortcomings, and the future perspectives for the treatment of cardiac-related genetic disorders will be discussed.

EXPERT OPINION

The ideal PE for the heart should be tissue-specific, regulatable, less immunogenic, high transducing, and safe. However, low efficiency, sup-optimal PE architecture, the large size of required elements, the unclear role of transcriptomics on the process, unpredictable off-target effects, and its context-dependency are subjects that need to be considered. It is also of great importance to see how beneficial or detrimental cell cycle or epigenomic modifier is to bring changes into cardiac cells. The PE delivery is challenging due to the size, multi-component properties of the editors and liver sink.

Host Cell Restriction Factors Blocking Efficient Vector Transduction: Challenges in Lentiviral and Adeno-Associated Vector Based Gene Therapies

Gene therapy relies on the delivery of genetic material to the patient's cells in order to provide a therapeutic treatment. Two of the currently most used and efficient delivery systems are the lentiviral (LV) and adeno-associated virus (AAV) vectors. Gene therapy vectors must successfully attach, enter uncoated, and escape host restriction factors (RFs), before reaching the nucleus and effectively deliver the therapeutic genetic instructions to the cell. Some of these RFs are ubiquitously expressed in mammalian cells, while others are cell-specific, and others still are expressed only upon induction by danger signals as type I interferons. Cell restriction factors have evolved to protect the organism against infectious diseases and tissue damage. These restriction factors can be intrinsic, directly acting on the vector, or related with the innate immune response system, acting indirectly through the induction of interferons, but both are intertwined. The innate immunity is the first line of defense against pathogens and, as such cells derived from myeloid progenitors (but not only), are well equipped with RFs to detect pathogen-associated molecular patterns (PAMPs). In addition, some non-professional cells, such as epithelial cells, endothelial cells, and fibroblasts, play major roles in pathogen recognition. Unsurprisingly, foreign DNA and RNA molecules are among the most detected PAMPs. Here, we review and discuss identified RFs that block LV and AAV vector transduction, hindering their therapeutic efficacy.

The CRISPR-Cas12a Platform for Accurate Genome Editing, Gene Disruption, and Efficient Transgene Integration in Human Immune Cells

CRISPR-Cas12a nucleases have expanded the toolbox for targeted genome engineering in a broad range of organisms. Here, using a high-throughput engineering approach, we explored the potential of a novel CRISPR-MAD7 system for genome editing in human cells. We evaluated several thousand optimization conditions and demonstrated accurate genome reprogramming with modified MAD7. We identified crRNAs that allow for ≤95% non-homologous end joining (NHEJ) and 66% frameshift mutations in various genes and observed the high-cleavage fidelity of MAD7 resulting in undetectable off-target activity. We explored the dsDNA delivery efficiency of CRISPR-MAD7, and by using our optimized transfection protocol, we obtained ≤85% chimeric antigen receptor (CAR) insertions in primary T cells, thus exceeding the baseline integration efficiencies of therapeutically relevant transgenes using currently available virus-free technologies. Finally, we evaluated multiplex editing efficiency with CRISPR-MAD7 and demonstrated simultaneous ≤35% CAR transgene insertions and ≤80% gene disruption efficiencies. Both the platform and our transfection procedure are easily adaptable for further preclinical studies and could potentially be used for clinical manufacturing of CAR T cells.

Latest progress in the study of nanoparticle-based delivery of the CRISPR/Cas9 system

The CRISPR/Cas9 system has been harnessed to cleave a targeted DNA fragment via its Cas nuclease activity under the direction of guide RNA for rendering gene insertions, deletions, and point mutations in basic research and clinical applications. There are a number of vehicles, including lipofectamine, viruses, and nanoparticles, that can deliver the CRISPR/Cas9 system, but all these methods face numerous challenges during their application in life science contexts. Here, we focus on the delivery of CRISPR/Cas9 via nanoparticles because this method has shown great advantages in terms of safety, simplicity and flexibility.

Synthetic multi-layer nanoparticles for CRISPR-Cas9 genome editing

The clustered regularly interspaced short palindromic repeat (CRISPR) has great potential to revolutionize biomedical research and disease therapy. The specific and efficient genome editing strongly depends on high efficiency of delivery of the CRISPR payloads. However, optimization of CRISPR delivery vehicles still remains a major obstacle. Recently, various non-viral vectors have been utilized to deliver CRISPR tools. Many of these vectors have multi-layer structures assembled. In this review, we will introduce the development of CRISPR-Cas9 systems and their general therapeutic applications by summarizing current CRISPR-Cas9 based clinical trials. We will highlight the multi-layer nanoparticles (NPs) that have been developed to deliver CRISPR cargos in vitro and in vivo for various purposes, as well the potential building blocks of multi-layer NPs. We will also discuss the challenges in making the CRISPR tools into viable pharmaceutical products and provide potential solutions on efficiency and biosafety issues.

Nonviral Nanoparticles for CRISPR-Based Genome Editing: Is It Just a Simple Adaption of What Have Been Developed for Nucleic Acid Delivery?

Genome-editing technologies hold tremendous potential for treating genetic diseases. However, the efficient and safe delivery of genome-editing elements to the location of interest, and the achievement of specific targeted gene correction without off-target side effect remains a big challenge. In this Perspective, we highlight recent developments and discuss the challenges of nonviral nanoparticles for the delivery of genome-editing tools. Finally, we will propose promising strategies to improve the delivery efficacy and advance the clinical translation of gene-editing technology.

Delivery of CRISPR/Cas9 by Novel Strategies for Gene Therapy

Precise editing of the genome of a living body is a goal pursued by scientists in many fields. In recent years, CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) genome-editing systems have become a revolutionary toolbox for gene editing across various species. However, the low transfection efficiency of the CRISPR/Cas9 system to mammalian cells in vitro and in vivo is a big obstacle hindering wide and deep application. In this review, recently developed delivery strategies for various CRISPR/Cas9 formulations and their applications in treating gene-related diseases are briefly summarized. This review should inspire others to explore more efficient strategies for CRISPR system delivery and gene therapy.

Non-viral delivery systems for CRISPR/Cas9-based genome editing: Challenges and opportunities

In recent years, CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) genome editing systems have become one of the most robust platforms in basic biomedical research and therapeutic applications. To date, efficient in vivo delivery of the CRISPR/Cas9 system to the targeted cells remains a challenge. Although viral vectors have been widely used in the delivery of the CRISPR/Cas9 system in vitro and in vivo, their fundamental shortcomings, such as the risk of carcinogenesis, limited insertion size, immune responses and difficulty in large-scale production, severely limit their further applications. Alternative non-viral delivery systems for CRISPR/Cas9 are urgently needed. With the rapid development of non-viral vectors, lipid- or polymer-based nanocarriers have shown great potential for CRISPR/Cas9 delivery. In this review, we analyze the pros and cons of delivering CRISPR/Cas9 systems in the form of plasmid, mRNA, or protein and then discuss the limitations and challenges of CRISPR/Cas9-based genome editing. Furthermore, current non-viral vectors that have been applied for CRISPR/Cas9 delivery in vitro and in vivo are outlined in details. Finally, critical obstacles for non-viral delivery of CRISPR/Cas9 system are highlighted and promising strategies to overcome these barriers are proposed.

Engineering the Delivery System for CRISPR-Based Genome Editing

Clustered regularly interspaced short palindromic repeat-CRISPR-associated protein (CRISPR-Cas) systems, found in nature as microbial adaptive immune systems, have been repurposed into an important tool in biological engineering and genome editing, providing a programmable platform for precision gene targeting. These tools have immense promise as therapeutics that could potentially correct disease-causing mutations. However, CRISPR-Cas gene editing components must be transported directly to the nucleus of targeted cells to exert a therapeutic effect. Thus, efficient methods of delivery will be critical to the success of therapeutic genome editing applications. Here, we review current strategies available for in vivo delivery of CRISPR-Cas gene editing components and outline challenges that need to be addressed before this powerful tool can be deployed in the clinic.

Ex vivo nonviral gene delivery of μ-opioid receptor to attenuate cancer-induced pain

Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. The vector has high transfection efficiency with little cytotoxicity in cancer cell lines including HSC-3 (human tongue squamous cell carcinoma) and exhibits differential expression in HSC-3 (∼45-fold) relative to HGF-1 (human gingival fibroblasts) cells. We used the nonviral vector to transfect cancer with OPRM1, the μ-opioid receptor gene, as a novel method for treating cancer-induced pain. After HSC-3 cells were transfected with OPRM1, a cancer mouse model was created by inoculating the transfected HSC-3 cells into the hind paw or tongue of athymic mice to determine the analgesic potential of OPRM1 transfection. Mice with HSC-3 tumors expressing OPRM1 demonstrated significant antinociception compared with control mice. The effect was reversible with local naloxone administration. We quantified β-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more β-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.

Interleukin-1 receptor type 1 is overexpressed in neurons but not in glial cells within the rat superficial spinal dorsal horn in complete Freund adjuvant-induced inflammatory pain

Background

All known biological functions of the pro-inflammatory cytokine interleukin-1β (IL-1β) are mediated by type 1 interleukin receptor (IL-1R1). IL-1β–IL-1R1 signaling modulates various neuronal functions including spinal pain processing. Although the role of IL-1β in pain processing is generally accepted, there is a discussion in the literature whether IL-1β exerts its effect on spinal pain processing by activating neuronal or glial IL-1R1. To contribute to this debate, here we investigated the expression and cellular distribution of IL-1R1 in the superficial spinal dorsal horn in control animals and also in inflammatory pain.

Methods

Experiments were performed on rats and wild type as well as IL-1R1-deficient mice. Inflammatory pain was evoked by unilateral intraplantar injection of complete Freund adjuvant (CFA). The nociceptive responsiveness of control and CFA-treated animals were tested daily for withdrawal responses to mechanical and thermal stimuli before and after CFA injection. Changes in the expression of 48 selected genes/mRNAs and in the quantity of IL-1R1 protein during the first 3 days after CFA injection were measured with the TaqMan low-density array method and Western blot analysis, respectively. The cellular localization of IL-1R1 protein was investigated with single and double staining immunocytochemical methods.

Results

We found a six times and two times increase in IL-1R1 mRNA and protein levels, respectively, in the dorsal horn of CFA-injected animals 3 days after CFA injection, at the time of the summit of mechanical and thermal allodynia. Studying the cellular distribution of IL-1R1, we found an abundant expression of IL-1R1 on the somatodendritic compartment of neurons and an enrichment of the receptor in the postsynaptic membranes of some excitatory synapses. In contrast to the robust neuronal localization, we observed only a moderate expression of IL-1R1 on astrocytes and a negligible one on microglial cells. CFA injection into the hind paw caused a remarkable increase in the expression of IL-1R1 in neurons, but did not alter the glial expression of the receptor.

Conclusion

The results suggest that IL-1β exerts its effect on spinal pain processing primarily through neuronal IL-1R1, but it can also interact in some extent with IL-1R1 expressed by astrocytes.

Improvement of spinal non-viral IL-10 gene delivery by D-mannose as a transgene adjuvant to control chronic neuropathic pain

BACKGROUND

Peri-spinal subarachnoid (intrathecal; i.t.) injection of non-viral naked plasmid DNA encoding the anti-inflammatory cytokine, IL-10 (pDNA-IL-10) suppresses chronic neuropathic pain in animal models. However, two sequential i.t. pDNA injections are required within a discrete 5 to 72-hour period for prolonged efficacy. Previous reports identified phagocytic immune cells present in the peri-spinal milieu surrounding the i.t injection site that may play a role in transgene uptake resulting in subsequent IL-10 transgene expression.

METHODS

In the present study, we aimed to examine whether factors known to induce pro-phagocytic anti-inflammatory properties of immune cells improve i.t. IL-10 transgene uptake using reduced naked pDNA-IL-10 doses previously determined ineffective. Both the synthetic glucocorticoid, dexamethasone, and the hexose sugar, D-mannose, were factors examined that could optimize i.t. pDNA-IL-10 uptake leading to enduring suppression of neuropathic pain as assessed by light touch sensitivity of the rat hindpaw (allodynia).

RESULTS

Compared to dexamethasone, i.t. mannose pretreatment significantly and dose-dependently prolonged pDNA-IL-10 pain suppressive effects, reduced spinal IL-1β and enhanced spinal and dorsal root ganglia IL-10 immunoreactivity. Macrophages exposed to D-mannose revealed reduced proinflammatory TNF-α, IL-1β, and nitric oxide, and increased IL-10 protein release, while IL-4 revealed no improvement in transgene uptake. Separately, D-mannose dramatically increased pDNA-derived IL-10 protein release in culture supernatants. Lastly, a single i.t. co-injection of mannose with a 25-fold lower pDNA-IL-10 dose produced prolonged pain suppression in neuropathic rats.

CONCLUSIONS

Peri-spinal treatment with D-mannose may optimize naked pDNA-IL-10 transgene uptake for suppression of allodynia, and is a novel approach to tune spinal immune cells toward pro-phagocytic phenotype for improved non-viral gene therapy.

Spinal interleukin-10 therapy to treat peripheral neuropathic pain

INTRODUCTION

  Current research indicates that chronic peripheral neuropathic pain includes a role for glia and the actions of proinflammatory factors. This review briefly discusses the glial and cytokine responses that occur following peripheral nerve damage in support of utilizing anti-inflammatory cytokine interleukin-10 (IL-10) therapy to suppress chronic peripheral neuropathic pain. SPINAL NONVIRAL INTERLEUKIN-10 GENE THERAPY:  IL-10 is one of the most powerful endogenous counter-regulators of proinflammatory cytokine function that acts in the nervous system. Subarachnoid (intrathecal) spinal injection of the gene encoding IL-10 delivered by nonviral vectors has several advantages over virally mediated gene transfer methods and leads to profound pain relief in several animal models. NONVIRAL GENE DELIVERY:  Lastly, data are reviewed that nonviral deoxyribonucleic acid (DNA) encapsulated by a biologically safe copolymer, poly(lactic-co-glycolic) acid (PLGA), thought to protect DNA, leads to significantly improved therapeutic gene transfer in animal models, which additionally and significantly extends pain relief.

CONCLUSIONS

  The impact of these early studies exploring anti-inflammatory genes emphasizes the exceptional therapeutic potential of new biocompatible intrathecal nonviral gene delivery approaches such as PLGA microparticles. Ultimately, ongoing expression of therapeutic genes is a viable option to treat chronic neuropathic pain in the clinic.

TLR9 ligand CpG-ODN applied to the injured mouse cornea elicits retinal inflammation

During bacterial and viral infections, unmethylated CpG-DNA released by proliferating and dying microbes is recognized by toll-like receptor (TLR) 9 in host cells, initiating innate immune responses. Many corneal infections occur secondary to epithelial breaches and represent a major cause of vision impairment and blindness globally. To mimic this clinical situation, we investigated mechanisms of TLR9 ligand-induced corneal inflammation in mice after epithelial debridement. Application of CpG oligodeoxynucleotides (ODNs) resulted in neutrophil and macrophage infiltration to the cornea and loss of transparency. By 6 hours after CpG-ODN administration, TLR9 mRNA was increased in the cornea and retina. In vivo clinical examination at 24 hours revealed inflammatory infiltrates in the vitreous and retina, which were confirmed ex vivo to be neutrophils and macrophages, along with activated resident microglia. CpG-ODN-induced intraocular inflammation was abrogated in TLR9(-/-) and macrophage-depleted mice. Bone marrow reconstitution of irradiated TLR9(-/-) mice with TLR9(+/+) bone marrow led to restored corneal inflammatory responses to CpG-ODN. Fluorescein isothiocyanate-CpG-ODN rapidly penetrated the cornea and ocular media to reach the retina, where it was present within CD68(+) retinal macrophages and microglia. These data show that topically applied CpG-ODN induces intraocular inflammation owing to TLR9 activation of monocyte-lineage cells. These novel findings indicate that microbial CpG-DNA released during bacterial and/or viral keratitis can cause widespread inflammation within the eye, including the retina.