Topical matrix-based siRNA silences local gene expression in a murine wound model

Hydrogels for RNA delivery

RNA-based therapeutics have shown tremendous promise in disease intervention at the genetic level, and some have been approved for clinical use, including the recent COVID-19 messenger RNA vaccines. The clinical success of RNA therapy is largely dependent on the use of chemical modification, ligand conjugation or non-viral nanoparticles to improve RNA stability and facilitate intracellular delivery. Unlike molecular-level or nanoscale approaches, macroscopic hydrogels are soft, water-swollen three-dimensional structures that possess remarkable features such as biodegradability, tunable physiochemical properties and injectability, and recently they have attracted enormous attention for use in RNA therapy. Specifically, hydrogels can be engineered to exert precise spatiotemporal control over the release of RNA therapeutics, potentially minimizing systemic toxicity and enhancing in vivo efficacy. This Review provides a comprehensive overview of hydrogel loading of RNAs and hydrogel design for controlled release, highlights their biomedical applications and offers our perspectives on the opportunities and challenges in this exciting field of RNA delivery.

The remarkable effect of menstrual blood stem cells seeded on bilayer scaffold composed of amniotic membrane and silk fibroin aiming to promote wound healing in diabetic mice

INTRODUCTION

Impaired chronic wound healing frequently occurs in diabetic patients. We hypothesized that menstrual blood-derived mesenchymal stem cells (MenSCs) in combination with bilayer scaffold consisted of human amniotic membrane (AM) and electrospun silk fibroin nanofibers could potentially promote wound healing in diabetic mice.

METHODS & METHODS

Two bilateral full-thickness wounds were created on dorsal skin of type-1 diabetic mice model and animals were equally divided in four groups including: no-treatment group (NT), amniotic membrane treated group (AM), bilayer scaffold treated group (bSC), and MenSCs-seeded bilayer scaffold treated group (bSC + MenSCs). Wound healing evaluations were performed at 3, 7, and 14 days after their treatment. The wound healing was analyzed by macroscopic and microscopic evaluations, and immunofluorescence staining of involucrin (IVL), type III collagen, CD31/ von Willebrand factor (vWF), and PGP9.5 were performed. Furthermore, number of neutrophils and macrophages and subpopulation of macrophages were assessed. In addition, the expression of Egr2, Mmp9, CXCL12, IDO1, Ptgs2 and VEGFA transcripts involved in wound repair were also analyzed.

RESULTS

After 14 days, the best epidermal and dermal regeneration belonged to the cases received bSC + MenSCs as wound dressing. Moreover, the wound healing was typically faster in this group compared to other groups. Immunofluorescence evaluation represented higher levels of CD31 and VWF, higher ratio of M2/M1 macrophages, greater expression of IVL, and higher levels of the PGP9.5 in the bSC + MenSCs group in comparison with other groups. Expression analysis of assessed genes also supported assumption of more regeneration and healing in the bSC + MenSCs group versus other groups.

CONCLUSION

These results indicate that enhanced immunomodulatory and reparative properties of MenSCs in conjunction with bilayer scaffold specified this cellular skin substitute for modulating wound chronicity and contribution to resolution of wound healing process in diabetic ulcer.

Novel drug delivery strategies and gene therapy regimen as a promising perspective for management of psoriasis

Psoriasis is an autoimmune disorder; however, an exact underlying mechanism responsible for psoriasis is yet not known. A hypothesis put forward is an abnormal proliferation of keratinocytes due to faulty signals brought about by T-cells. Due to the lack of evidence of the exact cause, a variety of treatments have been used of which topical therapy is usually the first option in most patients. Topical therapy has several shortcomings and barriers of drug delivary which may be effectively overcome using novel drug carrier systems which exhibit maximum penetration, controlled release, reduced irritancy and, overall, a better efficacy. Thus, novel treatment strategies based on gene therapy such as antisensing nucleotide, silencing RNA complex, stem cell therapy and antibody-based therapy are being envisaged. This review article discusses the concepts and background of current novel delivery systems and gene therapy tools for effective management of psoriasis.

Treatment of psoriasis with NFKBIZ siRNA using topical ionic liquid formulations

Systemic antibodies targeting tumor necrosis factor-α (TNF-α) and interleukin-17A (IL-17A) are effective in plaque psoriasis. Despite their popularity, safety concerns pose a challenge for systemic biologics. While anti-TNF-α and anti-IL-17A antibodies effectively inhibit respective proteins, we hypothesize that an approach based on local silencing of an upstream target such as NFKBIZ can be advantageous for treating psoriasis. However, effective delivery of small interfering RNA (siRNA) into the skin is a substantial hurdle due to skin's barrier function and poor stability of siRNA. Using ionic liquids as an enabling technology, we report on the effective delivery of NFKBIZ siRNA into the skin and its therapeutic efficacy in a psoriasis model. Treatment with IL-siRNA suppressed aberrant gene expression and resulted in down-regulation of psoriasis-related signals including TNF-α and IL-17A. These results provide a framework for a topical delivery platform for siRNA.

Sustained delivery of siRNA/mesoporous silica nanoparticle complexes from nanofiber scaffolds for long-term gene silencing

A low toxicity and efficient delivery system is needed to deliver small interfering RNAs (siRNA) in vitro and in vivo. The use of mesoporous silica nanoparticles (MSN) is becoming increasingly common due to its biocompatibility, tunable pore size and customizable properties. However, bolus delivery of siRNA/MSN complexes remains suboptimal, especially when a sustained and long-term administration is required. Here, we utilized electrospun scaffolds for sustained delivery of siRNA/MSN-PEI through surface adsorption and nanofiber encapsulation. As a proof-of-concept, we targeted collagen type I expression to modulate fibrous capsule formation. Surface adsorption of siRNA/MSN-PEI provided sustained availability of siRNA for at least 30 days in vitro. As compared to conventional bolus delivery, such scaffold-mediated transfection provided more effective gene silencing (p < 0.05). On the contrary, a longer sustained release was attained (at least 5 months) when siRNA/MSN-PEI complexes were encapsulated within the electrospun fibers. In vivo subcutaneous implantation and biodistribution analysis of these scaffolds revealed that siRNA remained localized up to ∼290 μm from the implants. Finally, a fibrous capsule reduction of ∼45.8% was observed after 4 weeks in vivo as compared to negative scrambled siRNA treatment. Taken together, these results demonstrate the efficacy of scaffold-mediated sustained delivery of siRNA/MSN-PEI for long-term non-viral gene silencing applications.

STATEMENT OF SIGNIFICANCE

The bolus delivery of siRNA/mesoporous silica nanoparticles (MSN) complexes shows high efficiency to silence protein agonists of tumoral processes as cancer treatments. However, in tissue engineering area, scaffold mediated delivery is desired to achieve a local and sustained release of therapeutics. We showed the feasibility and the efficacy of siRNA/MSN delivered from electrospun scaffolds through surface adsorption and nanofiber encapsulation. We showed that this method enhances siRNA transfection efficiency and sustained targeted proteins silencing in vitro and in vivo. As a proof of concept, in this study, we targeted collagen type I expression to modulate fibrous capsule formation. However this platform can be applied to the release and transfection of siRNA or miRNA in cancer and tissue engineering applications.

Novel lipoproteoplex delivers Keap1 siRNA based gene therapy to accelerate diabetic wound healing

Therapeutics utilizing siRNA are currently limited by the availability of safe and effective delivery systems. Cutaneous diseases, specifically ones with significant genetic components are ideal candidates for topical siRNA based therapy but the anatomical structure of skin presents a considerable hurdle. Here, we optimized a novel liposome and protein hybrid nanoparticle delivery system for the topical treatment of diabetic wounds with severe oxidative stress. We utilized a cationic lipid nanoparticle (CLN) composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and the edge activator sodium cholate (NaChol), in a 6:1 ratio of DOTAP:NaChol (DNC). Addition of a cationic engineered supercharged coiled-coil protein (CSP) in a 10:1:1 ratio of DNC:CSP:siRNA produced a stable lipoproteoplex (LPP) nanoparticle, with optimal siRNA complexation, minimal cytotoxicity, and increased transfection efficacy. In a humanized murine diabetic wound healing model, our optimized LPP formulation successfully delivered siRNA targeted against Keap1, key repressor of Nrf2 which is a central regulator of redox mechanisms. Application of LPP complexing siKeap1 restored Nrf2 antioxidant function, accelerated diabetic tissue regeneration, and augmented reduction-oxidation homeostasis in the wound environment. Our topical LPP delivery system can readily be translated into clinical use for the treatment of diabetic wounds and can be extended to other cutaneous diseases with genetic components.

Engineering approaches in siRNA delivery

siRNAs are very potent drug molecules, able to silence genes involved in pathologies development. siRNAs have virtually an unlimited therapeutic potential, particularly for the treatment of inflammatory diseases. However, their use in clinical practice is limited because of their unfavorable properties to interact and not to degrade in physiological environments. In particular they are large macromolecules, negatively charged, which undergo rapid degradation by plasmatic enzymes, are subject to fast renal clearance/hepatic sequestration, and can hardly cross cellular membranes. These aspects seriously impair siRNAs as therapeutics. As in all the other fields of science, siRNAs management can be advantaged by physical-mathematical descriptions (modeling) in order to clarify the involved phenomena from the preparative step of dosage systems to the description of drug-body interactions, which allows improving the design of delivery systems/processes/therapies. This review analyzes a few mathematical modeling approaches currently adopted to describe the siRNAs delivery, the main procedures in siRNAs vectors' production processes and siRNAs vectors' release from hydrogels, and the modeling of pharmacokinetics of siRNAs vectors. Furthermore, the use of physical models to study the siRNAs vectors' fate in blood stream and in the tissues is presented. The general view depicts a framework maybe not yet usable in therapeutics, but with promising possibilities for forthcoming applications.

RNAi mediated IL-6 in vitro knockdown in psoriasis skin model with topical siRNA delivery system based on liquid crystalline phase

Gene therapy by RNA interference (RNAi) is a post-transcriptional silencing process that can suppress the expression of a particular gene and it is a promising therapeutic approach for the treatment of many severe diseases, including cutaneous disorders. However, difficulties related to administration and body distribution limit the clinical use of small interfering RNA (siRNA) molecules. In this study, we proposed to use nanocarriers to enable siRNA application in the topical treatment of skin disorders. A siRNA nanodispersion based on liquid crystalline phase and composed of monoolein (MO), oleic acid (OA) and polyethylenimine (PEI) was developed and its physicochemical properties, efficiency of complexation and carrier/siRNA stability were assessed. Subsequently, cell viability, cellular uptake, in vitro skin irritation test using reconstructed human epidermis (RHE) and in vitro IL-6 knockdown in psoriasis skin model were evaluated. The results showed that the liquid crystalline nanodispersion is a promising topical delivery system for administration of siRNA, being able to overcome the limitations of the route of administration, as well those resulting from the characteristics of siRNA molecules. The formulation was effective at complexing the siRNA, presented high rate of cell uptake (∼90%), increased the skin penetration of siRNA in vitro, and did not cause skin irritation compared with Triton-X (a moderate irritant), resulting in a 4-fold higher viability of reconstructed human epidermis and a 15.6-fold lower release of IL-1α. A single treatment with the liquid crystalline nanodispersion carrying IL-6 siRNA for 6h was able to reduce the extracellular IL-6 levels by 3.3-fold compared with control treatment in psoriasis skin model. Therefore, liquid crystalline nanodispersion is a suitable nanocarrier for siRNA with therapeutic potential to suppress skin disease-specific genes. This study also highlights the applicability of reconstructed skin models in pharmaceutical field to evaluate the performance of delivery systems without the use of animal models.

Restoration of Nrf2 Signaling Normalizes the Regenerative Niche

Chronic hyperglycemia impairs intracellular redox homeostasis and contributes to impaired diabetic tissue regeneration. The Keap1/Nrf2 pathway is a critical regulator of the endogenous antioxidant response system, and its dysfunction has been implicated in numerous pathologies. Here we characterize the effect of chronic hyperglycemia on Nrf2 signaling within a diabetic cutaneous regeneration model. We characterized the effects of chronic hyperglycemia on the Keap1/Nrf2 pathway within models of diabetic cutaneous wound regeneration. We assessed reactive oxygen species (ROS) production and antioxidant gene expression following alterations in the Nrf2 suppressor Keap1 and the subsequent changes in Nrf2 signaling. We also developed a topical small interfering RNA (siRNA)-based therapy to restore redox homeostasis within diabetic wounds. Western blotting demonstrated that chronic hyperglycemia-associated oxidative stress inhibits nuclear translocation of Nrf2 and impairs activation of antioxidant genes, thus contributing to ROS accumulation. Keap1 inhibition increased Nrf2 nuclear translocation, increased antioxidant gene expression, and reduced ROS production to normoglycemic levels, both in vitro and in vivo. Topical siKeap1 therapy resulted in improved regenerative capacity of diabetic wounds and accelerated closure. We report that chronic hyperglycemia weakens the endogenous antioxidant response, and the consequences of this defect are manifested by intracellular redox dysregulation, which can be restored by Keap1 inhibition. Targeted siRNA-based therapy represents a novel, efficacious strategy to reestablish redox homeostasis and accelerate diabetic cutaneous tissue regeneration.

Technologies for controlled, local delivery of siRNA

The discovery of RNAi in the late 1990s unlocked a new realm of therapeutic possibilities by enabling potent and specific silencing of theoretically any desired genetic target. Better elucidation of the mechanism of action, the impact of chemical modifications that stabilize and reduce nonspecific effects of siRNA molecules, and the key design considerations for effective delivery systems has spurred progress toward developing clinically-successful siRNA therapies. A logical aim for initial siRNA translation is local therapies, as delivering siRNA directly to its site of action helps to ensure that a sufficient dose reaches the target tissue, lessens the potential for off-target side effects, and circumvents the substantial systemic delivery barriers. While locally injected or topically applied siRNA has progressed into numerous clinical trials, an enormous opportunity exists to develop sustained-release, local delivery systems that enable both spatial and temporal control of gene silencing. This review focuses on material platforms that establish both localized and controlled gene silencing, with emphasis on the systems that show most promise for clinical translation.

Sirtuin-6 deficiency exacerbates diabetes-induced impairment of wound healing

Delayed wound healing is one of the major complications in diabetes and is characterized by chronic proinflammatory response, and abnormalities in angiogenesis and collagen deposition. Sirtuin family proteins regulate numerous pathophysiological processes, including those involved in promotion of longevity, DNA repair, glycolysis and inflammation. However, the role of sirtuin 6 (SIRT6), a NAD+-dependent nuclear deacetylase, in wound healing specifically under diabetic condition remains unclear. To analyse the role of SIRT6 in cutaneous wound healing, paired 6-mm stented wound was created in diabetic db/db mice and injected siRNA against SIRT6 in the wound margins (transfection agent alone and nonsense siRNA served as controls). Wound time to closure was assessed by digital planimetry, and wounds were harvested for histology, immunohistochemistry and Western blotting. SIRT6-siRNA-treated diabetic wound showed impaired healing, which was associated with reduced capillary density (CD31-staining vessels) when compared to control treatment. Interestingly, SIRT6 deficiency decreased vascular endothelial growth factor expression and proliferation markers in the wounds. Furthermore, SIRT6 ablation in diabetic wound promotes nuclear factor-κB (NF-κB) activation resulting in increased expression of proinflammatory markers (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, tumor necrosis factor-α and interleukin-1β) and increased oxidative stress. Collectively, our findings demonstrate that loss of SIRT6 in cutaneous wound aggravates proinflammatory response by increasing NF-κB activation, oxidative stress and decrease in angiogenesis in the diabetic mice. Based on these findings, we speculate that the activation of SIRT6 signalling might be a potential therapeutic approach for promoting wound healing in diabetics.

Immunological and hematological toxicities challenging clinical translation of nucleic acid-based therapeutics

INTRODUCTION

Nucleic acid-based therapeutics (NATs) are proven agents in correcting disorders caused by gene mutations, as treatments against cancer, microbes and viruses, and as vaccine adjuvants. Although many traditional small molecule NATs have been approved for clinical use, commercialization of macromolecular NATs has been considerably slower, and only a few have successfully reached the market. Preclinical and clinical evaluation of macromolecular NATs has revealed many assorted challenges in immunotoxicity, hematotoxicity, pharmacokinetics (PKs), toxicology and formulation. Extensive review has been given to the PK and toxicological concerns of NATs including approaches designed to overcome these issues. Immunological and hematological issues are a commonly reported side effect of NAT treatment; however, literature exploring the mechanistic background of these effects is sparse.

AREAS COVERED

This review focuses on the immunomodulatory properties of various types of therapeutic nucleic acid concepts. The most commonly observed immunological and hematological toxicities are described for various NAT classes, with citations of how to circumvent these toxicities.

EXPERT OPINION

Although some success with overcoming immunological and hematological toxicities of NATs has been achieved in recent years, immunostimulation remains the main dose-limiting factor challenging clinical translation of these promising therapies. Novel delivery vehicles should be considered to overcome this challenge.

Normalizing dysfunctional purine metabolism accelerates diabetic wound healing

Diabetic patients exhibit dysfunction of the normal wound healing process, leading to local ischemia by vascular occlusive disease as well as sustained increases in the proinflammatory cytokines and overproduction of reactive oxygen species (ROS). Of the many sources of ROS, the enzyme xanthine oxidase (XO) has been linked to overproduction of ROS in diabetic environment, and studies have shown that treatment with XO inhibitors decreases XO overactivity and XO-generated ROS. This study evaluates the role of XO in the diabetic wound and the impact of specifically inhibiting its activity on wound healing. Treatment of diabetic wounds with siXDH (xanthine dehydrogenase siRNA) decreased XDH mRNA expression by 51.6%, XO activity by 35.9%, ROS levels by 78.1%, pathologic wound burden by 31.5%, and accelerated wound healing by 7 days (23.3%). Polymerase chain reaction analysis showed that increased XO activity in wild-type wound may be due to XDH to XO conversion and/or XO phosphorylation, but not to gene transcription, whereas increased XO activity in diabetic wounds may also be from gene transcription. These results suggest that XO may be responsible for large proportion of elevated oxidative stress in the diabetic wound environment and that normalizing the metabolic activity of XO using targeted delivery of siXDH may decrease overproduction of ROS and accelerate wound healing in diabetic patients.

Acellular dermal matrix-based gene therapy augments graft incorporation

BACKGROUND

Acellular dermal matrix (ADM) is widely used for structural or dermal replacement purposes. Given its innate biocompatibility and its potential to vascularize, we explored the possibility of ADM to function as a small interfering RNA (siRNA) delivery system. Specifically, we sought to improve ADM vascularization by siRNA-mediated inhibition of prolyl hydroxylase domain-2 (PHD2), a cytoplasmic protein that regulates hypoxia inducible factor-1α, and improve neovascularization.

MATERIALS AND METHODS

Fluorescently labeled siRNA was used to rehydrate thin implantable ADM. Pharmacokinetic release of siRNA was determined. Twelve millimeter sections of ADM reconstituted with PHD2 siRNA (nonsense siRNA as control) and applied to dorsal wounds of 40 FVB mice. Grafts were sewn in, bolstered, and covered with occlusive dressings. Photographs were taken at 0, 7, and 14 d. Wounds were harvested at 7 and 14 d and analyzed (messenger RNA, protein, histology, and immunohistochemistry).

RESULTS

Release kinetics was first-order with 80% release by 12 h. By day 14, PHD2-containing ADM appeared viable and adherent, whereas controls appeared nonviable and nonadherent. Real-time reverse transcription-polymerase chain reaction demonstrated near-complete knockdown of PHD2, whereas vascular endothelial growth factor and FGF-2 were increased 2.3- and 4.7-fold. On enzyme-linked immunosorbent assay, vascular endothelial growth factor was increased more than fourfold and stromal cell-derived factor doubled. Histology demonstrated improved graft incorporation in treated groups. Immunohistochemical demonstrated increased vascularity measured by CD31 staining and increased new cell proliferation by denser proliferating cell nuclear antigen staining in treated versus controls.

CONCLUSIONS

We concluded that ADM is an effective matrix for local delivery of siRNA. Strategies to improve the matrix and/or genetically alter the local tissue environment can be envisioned.

Noninvasive delivery of siRNA and plasmid DNA into skin by fractional ablation: erbium:YAG laser versus CO₂ laser

The present study was conducted to evaluate the impacts of fractional erbium (Er):YAG and CO2 lasers on skin permeation of small interfering (si)RNA and plasmid (p)DNA vectors. In vitro skin delivery was determined with a Franz diffusion cell. In vivo absorption was investigated by observing fluorescence and confocal microscopic imaging. Fractional laser-mediated ablation of the skin resulted in significant enhancement of dextran and siRNA penetration. Respective fluxes of dextran (10 kDa) and siRNA, which had similar molecular size, with Er:YAG laser irradiation at 5 J/cm(2) were 56- and 11-fold superior to that of intact skin. The respective permeation extents of dextran and siRNA by the CO2 laser at 4 mJ/400 spots were 42- and 12-fold greater than that of untreated skin. Fluorescence and confocal images showed increased fluorescence intensities and penetration depths of siRNA and pDNA delivery. According to an examination of the follicular permeant amount and fluorescence microscopy, hair follicles were important deposition areas for fractional laser-assisted delivery, with the Er:YAG modality revealing higher follicular siRNA selectivity than the CO2 modality. This is the first report of siRNA and pDNA penetrating the skin with a sufficient amount and depth with the assistance of fractional lasers.

Splinting Strategies to Overcome Confounding Wound Contraction in Experimental Animal Models

SIGNIFICANCE

Clinical healing by secondary intention frequently occurs in skin that is firmly anchored to underlying (human) connective tissue. Small animals (rodents) are extensively utilized to model human cutaneous wound healing, but they heal by wound contraction, a process that is limited in the human and confounds quantitative and qualitative evaluation of experimental wound repair.

RECENT ADVANCES

To alleviate wound contraction in loose-skinned species, practical solutions include choosing anatomical sites with firmly attached dermis and subcutis (e.g., rabbit ear) or performing mechanical fixation of the skin by using one of a number of devices or splints. In each case, the wound volume remains relatively constant, allowing the histomorphometric or biomolecular quantification of the cellular response under well-controlled, experimental conditions. In addition, the defined aperture of the splinted wound allows the placement of a variety of materials, including scaffolds, cells, and biologically active formulations into the wound site in an effort to potentiate the healing response and abrogate scarring. In contrast, production of larger experimental wounds or the deliberate distraction of wound margins can be used to model a hypertrophic response.

CRITICAL ISSUES

Device design parameters should consider ease of application, durability, and lack of interference with the normal influx of local and circulating cells to the wound site.

FUTURE DIRECTIONS

Improved methods of securing flexible splints would provide a more efficient experimental platform. These devices could also incorporate optical or electronic sensors that report both the mechanical and physiological status of the healing.

miR-21 regulates skin wound healing by targeting multiple aspects of the healing process

With the clarification of the important roles of microRNAs (miRNAs) in diverse physiologic and pathologic processes, the effects of miRNAs in wound healing have attracted more attention recently. However, the global pattern of miRNA expression in wound tissue is still unknown. In the present study, we depicted the miRNA profile and identified at least 54 miRNAs, including miR-21, changed for more than twofold at the stage of granulation formation during wound healing. These miRNAs were closely related to the major events of wound healing, including cell migration and proliferation, angiogenesis, and matrix remolding. Furthermore, we found that miR-21 was up-regulated after skin injury, mainly in activated and migrating epithelial cells of epidermis and mesenchymal cells of dermis. Locally antagonizing miR-21 by directly injecting antagomir to wound edge caused significant delay of wound closure with impaired collagen deposition. Unexpectedly, we found wounds treated with miR-21 antagomir had an obvious defect in wound contraction at an early stage of wound healing. The significant role of miR-21 in wound contraction was further confirmed by in vivo gain-of-function and in vitro loss-of-function experiments. In conclusion, the present study has for the first time depicted miRNA profiling of wound healing and demonstrated the involvement of miR-21 in regulating the wound contraction and collagen deposition. These results suggest that miR-21 may be a new medical target in skin wound manipulation.

Percutaneous gene therapy heals cranial defects

Nonhealing bone defects are difficult to treat. As the bone morphogenic protein and transforming growth factor beta pathways have been implicated in bone healing, we hypothesized that percutaneous Smad7 silencing would enhance signaling through both pathways and improve bone formation. Critical sized parietal trephine defects were created and animals received percutaneous injection of: agarose alone or agarose containing nonsense or Smad7 small interfering RNA (siRNA). At 12 weeks, SMADs1, 2, 3, 5, 7 and 8 levels were assessed. Smad1/5/8 osteogenic target, Dlx5, and SMAD2/3 angiogenic target, plasminogen activator inhibitor-1 (Pai1), transcription levels were measured. Noncanonical signaling through TGFβ activated kinase-1 (Tak1) and target, runt-related transcription factor 2 (Runx2) and collagen1α1 (Col1α1), transcription were also measured. Micro-computed tomography and Gomori trichome staining were used to assess healing. Percutaneous injection of Smad7 siRNA significantly knocked down Smad7 mRNA (86.3 ± 2.5%) and protein levels (46.3 ± 3.1%). The SMAD7 knockdown resulted in a significant increase in receptor-regulated SMADs (R-SMAD) (Smad 1/5/8 and Smad2/3) nuclear translocation. R-SMAD nuclear translocation increased Dlx5 and Pai1 transcription. Additionally, noncanonical signaling through Tak1 increased Runx2 and Col1α1 target transcription. Compared with animals treated with agarose alone (33.9 ± 2.8% healing) and nonsense siRNA (31.5 ± 11.8% healing), animals treated Smad7 siRNA had significantly great (91.2 ± 3.8%) healing. Percutaneous Smad7 silencing increases signal transduction through canonical and noncanonical pathways resulting in significant bone formation. Minimally invasive gene therapies may prove effective in the treatment of nonhealing bone defects.

Nanofibrous scaffold-mediated REST knockdown to enhance neuronal differentiation of stem cells

At present, the recovery prospect for patients with chronic neurodegenerative diseases or acute trauma in the central nervous system is sub-optimal. The controlled differentiation of neural stem/progenitor cells (NPCs) to functional neurons is a possible treatment strategy. In contrast to the classical approach of biochemicals supplementation for guided stem cell commitment, this study explores the feasibility of directing neuronal differentiation through synergistic integration of three-dimensional nanofibrous topographical cues and scaffold-mediated knockdown of RE-1 silencing transcription factor (REST) in mouse NPCs. Taking advantage of the strong adhesive property and latent reactivity of mussel-inspired polydopamine (PD) coating, electrospun polycaprolactone (PCL) nanofibers were successfully functionalized with REST siRNAs (denoted as siREST PD-fiber). Sustained REST knockdown in NPCs was achieved for up to five days in vitro and the silencing efficiency was significantly higher than that mediated through siRNA adsorption onto non-PD coated sample controls. The silencing of REST, together with nanofiber topographical effect, significantly enhanced NPC neuronal commitment (57.5% Map2(+) cells in siREST PD-fiber vs. 43.5% in siREST PD-film vs. 50% in PD-fiber controls, p < 0.05) while reducing astrocytic and oligodendrocytic differentiation (10.7% O4(+) cells vs. ∼30% in siREST PD-film, p < 0.01). Taken together, the synergistic effects of scaffold-mediated REST knockdown and topographical cues from PD-modified nanofibers may be a useful strategy for generating functional neurons for therapeutic purposes.

Delivery systems and local administration routes for therapeutic siRNA

With the increasing number of studies proposing new and optimal delivery strategies for the efficacious silencing of gene-related diseases by the local administration of siRNAs, the present review aims to provide a broad overview of the most important and latest developments of non-viral siRNA delivery systems for local administration. Moreover, the main disease targets for the local delivery of siRNA to specific tissues or organs, including the skin, the lung, the eye, the nervous system, the digestive system and the vagina, were explored.

RNAi functionalized collagen-chitosan/silicone membrane bilayer dermal equivalent for full-thickness skin regeneration with inhibited scarring

Scar inhibition of dermal equivalent is one of the key issues for treatment of full thickness skin defects. To yield a bioactive RNAi functionalized matrix for skin regeneration with inhibited scarring, collagen-chitosan/silicone membrane bilayer dermal equivalent (BDE) was combined with trimetylchitosan (TMC)/siRNA complexes which could induce suppression of transforming growth factor-β1 (TGF-β1) pathway. The RNAi-BDE functioned as a reservoir for the incorporated TMC/siRNA complexes, enabling a prolonged siRNA release. The seeded fibroblasts in the RNAi-BDE showed good viability, internalized the TMC/siRNA complexes effectively and suppressed TGF-β1 expression constantly until 14 d. Application of the RNAi-BDE on the full-thickness skin defects of pig backs confirmed the in vivo inhibition of TGF-β1 expression by immunohistochemistry, real-time quantitative PCR and western blotting during 30 d post surgery. The levels of other scar-related factors such as collagen type I, collagen type III and α-smooth muscle actin (α-SMA) were also down-regulated. In combination with the ultra-thin skin graft transplantation for 73 d, the regenerated skin by RNAi-BDE had an extremely similar structure to that of the normal one. Our study reflects the latest paradigm of tissue engineering by incorporating the emerging biomolecule siRNA. The 3-D scaffolding materials for siRNA delivery may have general implications in generation of bioactive matrix as well.

Improving Wound Healing with Topical Gene Therapy

BACKGROUND

Impaired wound healing remains a major clinical problem with many etiologies. Altering gene expression to enhance healing is an innovative therapeutic approach. In recent years, we have developed a means to topically silence genes at the post-transcriptional level to locally alter wounds and improve the healing process.

THE PROBLEM

Many types of chronic wounds have been associated with alterations in the expression of genes that mediate healing. Targeting the expression of these genes in a way that can improve healing while limiting systemic side effects has been very challenging.

BASIC/CLINICAL SCIENCE ADVANCES

Our laboratory's recent work has focused on the use of topically applied small interfering ribonucleic acid (siRNA) to inhibit messenger RNA expression of certain mediators involved in healing in two different types of cutaneous injury-radiation-induced cutaneous injury and the diabetic excisional wound. By successfully inhibiting specific gene mediators with topical siRNA, we reversed downstream signaling pathways, which led to expedited wound healing in diabetic wounds and restoration to a more normal phenotype in radiation-induced skin injuries.

CLINICAL CARE RELEVANCE

The signaling pathways and gene mediators that we targeted and inhibited in murine models are present in humans. Applying parallel treatment strategies in humans may provide novel means of treating these burdensome and costly conditions.

CONCLUSION

Our novel method for local gene silencing is effective in treating various types of cutaneous murine wounds. Topical gene silencing with siRNA obviates the side effects of systemic medication and has the potential to be effective in healing or preventing a wide array of cutaneous human conditions.

Topical prolyl hydroxylase domain-2 silencing improves diabetic murine wound closure

Prolyl hydroxylase domain 2 (PHD2) has been implicated in several pathways of cell signaling, most notably in its regulation of hypoxia-inducible factor (HIF)-1α stability. In normoxia, PHD2 hydroxylates proline residues on HIF-1α, rendering it inactive. However, in hypoxia, PHD2 is inactive, HIF-1α is stabilized and downstream effectors such as vascular endothelial growth factor and fibroblast growth factor-2 are produced to promote angiogenesis. In the present study we utilize RNA interference to PHD2 to promote therapeutic angiogenesis in a diabetic wound model, presumably by the stabilization of HIF-1α. Stented wounds were created on the dorsum of diabetic Lepr db/db mice. Mice were treated with PHD2 small interfering RNA (siRNA) or nonsense siRNA. Wounds were measured photometrically on days 0-28. Wounds were harvested for histology, protein, and RNA analysis. Diabetic wounds treated with siRNA closed within 21±1.2 days; sham-treated closed in 28±1.5 days. By day 7, Western blot revealed near complete suppression of PHD protein and corresponding increased HIF-1α. Angiogenic mediators vascular endothelial growth factor and fibroblast growth factor-2 were elevated, corresponding to increased CD31 staining in the treated groups. siRNA-mediated silencing of PHD2 increases HIF-1α and several mediators of angiogenesis. This corresponded to improved time to closure in diabetic wounds compared with sham-treated wounds. These findings suggest that impaired wound healing in diabetes can be ameliorated with therapeutic angiogenesis.

RNA interference therapy via functionalized scaffolds

Tissue engineering aims to provide structural and biomolecular cues to compromised tissues through scaffolds. An emerging biomolecular cue is that of RNA interference by which the expression of genes can be silenced through a potent endogenous pathway. Recombinant viral-based approaches in RNAi delivery exist; however non-viral strategies offer many opportunities to exploit this mechanism of regulation in a safer way. Current RNAi therapies in clinical trials are without a vector (naked) or have slightly modified structures. Modification of these molecules with efficient backbone moieties for improved stability and potency, protecting and buffering them with delivery vehicles, and using scaffolds as reservoirs of delivery is at the frontier of current research. However, to enable an efficient sustained therapeutic effect scaffolds have a potentially significant role to play. This review presents non-viral delivery of RNAi that have been attempted via tissue engineered scaffolds. For RNAi to have a clinical impact, it is imperative to evaluate optimal delivery systems to ensure that the efficacy of this promising technology can be maximized.

Improved diabetic wound healing through topical silencing of p53 is associated with augmented vasculogenic mediators

Diabetes is characterized by several poorly understood phenomena including dysfunctional wound healing and impaired vasculogenesis. p53, a master cell cycle regulator, is upregulated in diabetic wounds and has recently been shown to play a regulatory roles in vasculogenic pathways. We have previously described a novel method to topically silence target genes in a wound bed with small interfering (si)RNA. We hypothesized that silencing p53 results in improved diabetic wound healing and augmentation of vasculogenic mediators. Paired 4-mm stented wounds were created on diabetic db/db mice. Topically applied p53 siRNA, evenly distributed in an agarose matrix, was applied to wounds at postwound day 1 and 7 (matrix alone and nonsense siRNA served as controls). Animals were sacrificed at postwound days 10 and 24. Wound time to closure was photometrically assessed, and wounds were harvested for histology, immunohistochemistry, and immunofluorescence. Vasculogenic cytokine expression was evaluated via Western blot, reverse transcription-polymerase chain reaction, and enzyme-linked immunosorbent assay. The ANOVA/t-test was used to determine significance (p≤ 0.05). Local p53 silencing resulted in faster wound healing with wound closure at 18±1.3 d in the treated group vs. 28±1.0 d in controls. The treated group demonstrated improved wound architecture at each time point while demonstrating near-complete local p53 knockdown. Moreover, treated wounds showed a 1.92-fold increase in CD31 endothelial cell staining over controls. Western blot analysis confirmed near-complete p53 knockdown in treated wounds. At day 10, VEGF secretion (enzyme-linked immunosorbent assay) was significantly increased in treated wounds (109.3±13.9 pg/mL) vs. controls (33.0±3.8 pg/mL) while reverse transcription-polymerase chain reaction demonstrated a 1.86-fold increase in SDF-1 expression in treated wounds vs. controls. This profile was reversed after the treated wounds healed and before closure of controls (day 24). Augmented vasculogenic cytokine profile and endothelial cell markers are associated with improved diabetic wound healing in topical gene therapy with p53 siRNA.

Cutaneous short-interfering RNA therapy

Since the 1990s, RNA interference (RNAi) has become a major subject of interest, not only as a tool for biological research, but also, more importantly, as a therapeutic approach for gene-related diseases. The use of short-interfering RNAs (siRNAs) for the sequence-specific knockdown of disease-causing genes has led to numerous preclinical and even a few clinical studies. Applications for cutaneous delivery of therapeutic siRNA are now emerging owing to a strong demand for effective treatments of various cutaneous disorders. Although successful studies have been performed using several different delivery techniques, most of these techniques encounter limitations for translation to the clinic with regards to patient compliance. This review describes the principal findings and applications in cutaneous RNAi therapy and focuses on the promises and pitfalls of the delivery systems.

Lipidic systems for in vivo siRNA delivery

The ability of small-interfering RNA (siRNA) to silence specific target genes not only offers a tool to study gene function but also represents a novel approach for the treatment of various human diseases. Its clinical use, however, has been severely hampered by the lack of delivery of these molecules to target cell populations in vivo due to their instability, inefficient cell entry, and poor pharmacokinetic profile. Various delivery vectors including liposomes, polymers, and nanoparticles have thus been developed in order to circumvent these problems. This review presents a comprehensive overview of the barriers and recent progress for both local and systemic delivery of therapeutic siRNA using lipidic vectors. Different strategies for formulating these siRNA-loaded lipid particles as well as the general concern about their safe use in vivo will also be discussed. Finally, current advances in the targeted delivery of siRNA and their impacts on the field of RNA interference (RNAi)-based therapy will be presented.

Specific Inhibition of Orthopoxvirus Replication by a Small Interfering RNA Targeting the D5R Gene

Background

Concerns about the potential use of smallpox in bioterrorism have stimulated interest in the development of novel antiviral treatments. Currently, there are no effective therapies against smallpox and new treatment strategies are greatly needed.

Methods

In this study, specifically designed small interfering RNAs (siRNAs), targeting five proteins essential for orthopoxvirus replication, were investigated for their ability to inhibit vaccinia virus strain Western Reserve (VACVWR) replication.

Results

Among these siRNAs, 100 nM siD5R-2, an siRNA targeting the D5 protein, decreased VACVWR replication up to 90% when used either prophylactically or therapeutically in human lung carcinoma A549 cells. This siRNA induced a striking concentration-dependent inhibition of VACVWR replication and a prolonged prophylactic antiviral effect that lasted for 72 h, at a concentration of 100 nM. Confocal microscopy of Alexa–siD5R-2-treated VACVWR-infected cells confirmed a decrease in viral replication. Furthermore, siD5R-2 was shown to specifically reduce the D5R mRNA and protein expression using real-time reverse tran-scriptase-PCR and western blotting analysis, without inducing interferon-β in A549 cells. We also demonstrated the antiviral potency of siD5R-2 against different pathogenic orthopoxviruses, such as cowpox and monkeypox viruses, which were inhibited up to 70% at the lowest concentration (1 nM) tested. Finally, siD5R-2 showed antiviral effects in VACVWR-infected human keratinocyte and fibroblast cell cultures.

Conclusions

These results suggest that siD5R-2 could be a potential candidate to treat poxvirus infections.

Not miR-ly small RNAs: big potential for microRNAs in therapy

RNA interference (RNAi) describes a set of natural processes in which genes are silenced by small RNAs. RNAi has been widely used as an experimental tool that has recently become the focus of drug development efforts to treat a variety of diseases and disorders. Like all molecular therapies, in vivo delivery is the major hurdle to realizing therapeutic RNAi. Several strategies have been developed that increase small RNA half-life in the blood, facilitate transduction across biological membranes, and mediate cell-specific delivery. Importantly, these strategies permit targeting of mRNAs as well as microRNAs (miRNAs), a class of small RNAs encoded in the genome. miRNAs are required for multiple developmental and cellular processes. Dysfunction of miRNAs can result in a host of pathologies, suggesting that miRNAs are potential targets of therapy. Recent studies of miRNA function in immune-specific pathways indicate that specific miRNAs might be exploited as therapeutic targets to treat immune disorders, including autoimmunity, allergy, and hematopoietic cancers.