Direct adenovirus-mediated IGF-I gene transduction of synovium induces persisting synovial fluid IGF-I ligand elevations

Locally Directed Recombinant Adeno- Associated Virus-Mediated IGF-1 Gene Therapy Enhances Osteochondral Repair and Counteracts Early Osteoarthritis In Vivo

BACKGROUND

Restoration of osteochondral defects is critical, because osteoarthritis (OA) can arise.

HYPOTHESIS

Overexpression of insulin-like growth factor 1 (IGF-1) via recombinant adeno-associated viral (rAAV) vectors (rAAV-IGF-1) would improve osteochondral repair and reduce parameters of early perifocal OA in sheep after 6 months in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Osteochondral defects were created in the femoral trochlea of adult sheep and treated with rAAV-IGF-1 or rAAV-lacZ (control) (24 defects in 6 knees per group). After 6 months in vivo, osteochondral repair and perifocal OA were assessed by well-established macroscopic, histological, and immunohistochemical scoring systems as well as biochemical and micro-computed tomography evaluations.

RESULTS

Application of rAAV-IGF-1 led to prolonged (6 months) IGF-1 overexpression without adverse effects, maintaining a significantly superior overall cartilage repair, together with significantly improved defect filling, extracellular matrix staining, cellular morphology, and surface architecture compared with rAAV-lacZ. Expression of type II collagen significantly increased and that of type I collagen significantly decreased. Subchondral bone repair and tidemark formation were significantly improved, and subchondral bone plate thickness and subarticular spongiosa mineral density returned to normal. The OA parameters of perifocal structure, cell cloning, and matrix staining were significantly better preserved upon rAAV-IGF-1 compared with rAAV-lacZ. Novel mechanistic associations between parameters of osteochondral repair and OA were identified.

CONCLUSION

Local rAAV-mediated IGF-1 overexpression enhanced osteochondral repair and ameliorated parameters of perifocal early OA.

CLINICAL RELEVANCE

IGF-1 gene therapy may be beneficial in repair of focal osteochondral defects and prevention of perifocal OA.

A pilot study to determine the optimal dose of scAAVIL-1ra in a large animal model of post-traumatic osteoarthritis

Gene therapy approaches using adeno-associated viral vectors have been successfully tested in the equine post-traumatic osteoarthritis (PTOA) model. Owing to differences in the levels of transgene expression and adverse tissue reactions observed in published studies, we sought to identify a safe therapeutic dose of scAAVIL-1ra in an inflamed and injured joint that would result in improved functional outcomes without any adverse events. scAAVIL-1ra was delivered intra-articularly over a 100-fold range, and horses were evaluated throughout and at the end of the 10-week study. A dose-related increase in IL-1ra levels with a decrease in PGE2 levels was observed, with the peak IL-1ra concentration being observed 7 days post-treatment in all groups. Perivascular infiltration with mononuclear cells was observed within the synovial membrane of the joint treated with the highest viral dose of 5 × 1012 vg, but this was absent in the lower-dosed joints. The second-highest dose of scAAVeqIL-1ra 5 × 1011 vg demonstrated elevated IL-1ra levels without any cellular response in the synovium. Taken together, the data suggest that the 10-fold lower dose of 5 × 1011vg scAAVIL-1ra would be a safe therapeutic dose in an equine model of PTOA.

Administration and detection of gene therapy in horses: A systematic review

Gene therapy uses genetic modification of cells to produce a therapeutic effect. Defective or missing genes can be repaired or replaced, or gene expression can be modified using a variety of technologies. Repair of defective genes can be achieved using specialized gene editing tools. Gene addition promotes gene expression by introducing synthetic copies of genes of interest (transgenes) into cells where they are transcribed and translated into therapeutic proteins. Protein production can also be modified using therapies that regulate gene expression. Gene therapy is currently prohibited in both human and equine athletes because of the potential to induce production of performance-enhancing proteins in the athlete's body, also referred to as "gene doping." Detection of gene doping is challenging and necessitates development of creative, novel analytical methods for doping control. Methods for detection of gene doping must be specific to and will vary depending on the type of gene therapy. The purpose of this paper is to present the results of a systematic review of gene editing, gene therapy, and detection of gene doping in horses. Based on the published literature, gene therapy has been administered to horses in a large number of experimental studies and a smaller number of clinical cases. Detection of gene therapy is possible using a combination of PCR and sequencing technologies. This summary can provide a basis for discussion of appropriate and inappropriate uses for gene therapy in horses by the veterinary community and guide expansion of methods to detect inappropriate uses by the regulatory community.

Gene therapy approaches for equine osteoarthritis

With an intrinsically low ability for self-repair, articular cartilage injuries often progress to cartilage loss and joint degeneration resulting in osteoarthritis (OA). Osteoarthritis and the associated articular cartilage changes can be debilitating, resulting in lameness and functional disability both in human and equine patients. While articular cartilage damage plays a central role in the pathogenesis of OA, the contribution of other joint tissues to the pathogenesis of OA has increasingly been recognized thus prompting a whole organ approach for therapeutic strategies. Gene therapy methods have generated significant interest in OA therapy in recent years. These utilize viral or non-viral vectors to deliver therapeutic molecules directly into the joint space with the goal of reprogramming the cells' machinery to secrete high levels of the target protein at the site of injection. Several viral vector-based approaches have demonstrated successful gene transfer with persistent therapeutic levels of transgene expression in the equine joint. As an experimental model, horses represent the pathology of human OA more accurately compared to other animal models. The anatomical and biomechanical similarities between equine and human joints also allow for the use of similar imaging and diagnostic methods as used in humans. In addition, horses experience naturally occurring OA and undergo similar therapies as human patients and, therefore, are a clinically relevant patient population. Thus, further studies utilizing this equine model would not only help advance the field of human OA therapy but also benefit the clinical equine patients with naturally occurring joint disease. In this review, we discuss the advancements in gene therapeutic approaches for the treatment of OA with the horse as a relevant patient population as well as an effective and commonly utilized species as a translational model.

Hydrogel-Guided, rAAV-Mediated IGF-I Overexpression Enables Long-Term Cartilage Repair and Protection against Perifocal Osteoarthritis in a Large-Animal Full-Thickness Chondral Defect Model at One Year In Vivo

The regeneration of focal articular cartilage defects is complicated by the reduced quality of the repair tissue and the potential development of perifocal osteoarthritis (OA). Biomaterial-guided gene therapy may enhance cartilage repair by controlling the release of therapeutic sequences in a spatiotemporal manner. Here, the benefits of delivering a recombinant adeno-associated virus (rAAV) vector coding for the human insulin-like growth factor I (IGF-I) via an alginate hydrogel (IGF-I/AlgPH155) to enhance repair of full-thickness chondral defects following microfracture surgery after one year in minipigs versus control (lacZ/AlgPH155) treatment are reported. Sustained IGF-I overexpression is significantly achieved in the repair tissue of defects treated with IGF-I/AlgPH155 versus those receiving lacZ/AlgPH155 for one year and in the cartilage surrounding the defects. Administration of IGF-I/AlgPH155 significantly improves parameters of cartilage repair at one year relative to lacZ/AlgPH155 (semiquantitative total histological score, cell densities, matrix deposition) without deleterious or immune reactions. Remarkably, delivery of IGF-I/AlgPH155 also significantly reduces perifocal OA and inflammation after one year versus lacZ/AlgPH155 treatment. Biomaterial-guided rAAV gene transfer represents a valuable clinical approach to promote cartilage repair and to protect against OA.

Scaffold-Mediated Gene Delivery for Osteochondral Repair

Osteochondral defects involve both the articular cartilage and the underlying subchondral bone. If left untreated, they may lead to osteoarthritis. Advanced biomaterial-guided delivery of gene vectors has recently emerged as an attractive therapeutic concept for osteochondral repair. The goal of this review is to provide an overview of the variety of biomaterials employed as nonviral or viral gene carriers for osteochondral repair approaches both in vitro and in vivo, including hydrogels, solid scaffolds, and hybrid materials. The data show that a site-specific delivery of therapeutic gene vectors in the context of acellular or cellular strategies allows for a spatial and temporal control of osteochondral neotissue composition in vitro. In vivo, implantation of acellular hydrogels loaded with nonviral or viral vectors has been reported to significantly improve osteochondral repair in translational defect models. These advances support the concept of scaffold-mediated gene delivery for osteochondral repair.

Gene therapy for chondral and osteochondral regeneration: is the future now?

Gene therapy might represent a promising strategy for chondral and osteochondral defects repair by balancing the management of temporary joint mechanical incompetence with altered metabolic and inflammatory homeostasis. This review analysed preclinical and clinical studies on gene therapy for the repair of articular cartilage defects performed over the last 10 years, focussing on expression vectors (non-viral and viral), type of genes delivered and gene therapy procedures (direct or indirect). Plasmids (non-viral expression vectors) and adenovirus (viral vectors) were the most employed vectors in preclinical studies. Genes delivered encoded mainly for growth factors, followed by transcription factors, anti-inflammatory cytokines and, less frequently, by cell signalling proteins, matrix proteins and receptors. Direct injection of the expression vector was used less than indirect injection of cells, with or without scaffolds, transduced with genes of interest and then implanted into the lesion site. Clinical trials (phases I, II or III) on safety, biological activity, efficacy, toxicity or bio-distribution employed adenovirus viral vectors to deliver growth factors or anti-inflammatory cytokines, for the treatment of osteoarthritis or degenerative arthritis, and tumour necrosis factor receptor or interferon for the treatment of inflammatory arthritis.

Targeted gene delivery to the synovial pannus in antigen-induced arthritis by ultrasound-targeted microbubble destruction in vivo

The purpose of this study was to optimize an ultrasound-targeted microbubble destruction (UTMD) technique to improve the in vivo transfection efficiency of the gene encoding enhanced green fluorescent protein (EGFP) in the synovial pannus in an antigen-induced arthritis rabbit model. A mixture of microbubbles and plasmids was locally injected into the knee joints of an antigen-induced arthritis (AIA) rabbits. The plasmid concentrations and ultrasound conditions were varied in the experiments. We also tested local articular and intravenous injections. The rabbits were divided into five groups: (1) ultrasound+microbubbles+plasmid; (2) ultrasound+plasmid; (3) microbubble+plasmid; (4) plasmid only; (5) untreated controls. EGFP expression was observed by fluorescent microscope and immunohistochemical staining in the synovial pannus of each group. The optimal plasmid dosage and ultrasound parameter were determined based on the results of EGFP expression and the present and absent of tissue damage under light microscopy. The irradiation procedure was performed to observe the duration of the EGFP expression in the synovial pannus and other tissues and organs, as well as the damage to the normal cells. The optimal condition was determined to be a 1-MHz ultrasound pulse applied for 5 min with a power output of 2 W/cm(2) and a 20% duty cycle along with 300 μg of plasmid. Under these conditions, the synovial pannus showed significant EGFP expression without significant damage to the surrounding normal tissue. The EGFP expression induced by the local intra-articular injection was significantly more increased than that induced by the intravenous injection. The EGFP expression in the synovial pannus of the ultrasound+microbubbles+plasmid group was significantly higher than that of the other four groups (P<0.05). The expression peaked on day 5, remained detectable on day 40 and disappeared on day 60. No EGFP expression was detected in the other tissues and organs. The UTMD technique can significantly enhance the in vivo gene transfection efficiency without significant tissue damage in the synovial pannus of an AIA model. Thus, this could become a safe and effective non-viral gene transfection procedure for arthritis therapy.

Mechanical properties and structure-function relationships in articular cartilage repaired using IGF-I gene-enhanced chondrocytes

Several studies have demonstrated the benefits of IGF-I gene therapy in enhancing the histologic and biochemical content of cartilage repaired by chondrocyte transplantation. However, there is little to no data on the mechanical performance of IGF-I augmented cartilage grafts. This study evaluated the compressive properties of full-thickness chondral defects in the equine femur repaired with and without IGF-I gene therapy. Animals were randomly assigned to one of three study cohorts based on chondrocyte treatment provided in each defect: (i) IGF-I gene delivered by recombinant adeno-associated virus (rAAV)-5; (ii) AAV-5 delivering GFP as a reporter; (iii) naïve cells without virus. In each case, the opposite limb was implanted with a fibrin carrier without cells. Samples were prepared for confined compression testing to measure the aggregate modulus and hydraulic permeability. All treatment groups, regardless of cell content or transduction, had mechanical properties inferior to native cartilage. Overexpression of IGF-I increased modulus and lowered permeability relative to other treatments. Investigation of structure-property relationships revealed that Ha and k were linearly correlated with GAG content but logarithmically correlated with collagen content. This provides evidence that IGF-I gene therapy can improve healing of articular cartilage and can greatly increase the mechanical properties of repaired grafts.

Humoral and cell-mediated immune response, and growth factor synthesis after direct intraarticular injection of rAAV2-IGF-I and rAAV5-IGF-I in the equine middle carpal joint

Intraarticular (IA) administration of viral vectors expressing a therapeutic transgene is an attractive treatment modality for osteoarthritis (OA) as the joint can be treated as a contained unit. Humoral and cell-mediated immune responses in vivo can limit vector effectiveness. Transduction of articular tissues has been investigated; however, the immune response to IA vectors remains largely unknown. We hypothesized that IA rAAV2 and rAAV5 overexpressing insulin-like growth factor-I (IGF-I) would result in long-term IGF-I formation but would also induce neutralizing antibodies (NAb) and anti-capsid effector T cells. Twelve healthy horses were assigned to treatment (rAAV2 or rAAV5) or control (saline) groups. Middle carpal joints were injected with 5×10(11) vector genomes/joint. Synovial fluid was analyzed for changes in composition, NAb titers, immunoglobulin isotypes, proinflammatory cytokines, and IGF-I. Serum was analyzed for antibody titers and cytokines. A T cell restimulation assay was used to assess T cell responses. Injection of rAAV2- or rAAV5-IGF-I did not induce greater inflammation compared with saline. Synovial fluid IGF-I was significantly increased in both rAAV2- and rAAV5-IGF-I joints by day 14 and remained elevated until day 56; however, rAAV5 achieved the highest concentrations. A capsid-specific T cell response was not noted although all virus-treated horses had increased NAbs in serum and synovial fluid after treatment. Taken together, our data show that IA injection of rAAV2- or rAAV5-IGF-I does not incite a clinically detectable inflammatory or cell-mediated immune response and that IA gene therapy using minimally immunogenic vectors represents a clinically relevant tool for treating articular disorders including OA.

Gene therapy for human osteoarthritis: principles and clinical translation

INTRODUCTION

Osteoarthritis (OA) is the most prevalent chronic joint disease. Its key feature is a progressive articular cartilage loss. Gene therapy for OA aims at delivering gene-based therapeutic agents to the osteoarthritic cartilage, resulting in a controlled, site-specific, long-term presence to rebuild the damaged cartilage.

AREAS COVERED

An overview is provided of the principles of gene therapy for OA based on a PubMed literature search. Gene transfer to normal and osteoarthritic cartilage in vitro and in animal models in vivo is reviewed. Results from recent clinical gene therapy trials for OA are discussed and placed into perspective.

EXPERT OPINION

Recombinant adeno-associated viral (rAAV) vectors enable to directly transfer candidate sequences in human articular chondrocytes in situ, providing a potent tool to modulate the structure of osteoarthritic cartilage. However, few preclinical animal studies in OA models have been performed thus far. Noteworthy, several gene therapy clinical trials have been carried out in patients with end-stage knee OA based on the intraarticular injection of human juvenile allogeneic chondrocytes overexpressing a cDNA encoding transforming growth factor-beta-1 via retroviral vectors. In a recent placebo-controlled randomized trial, clinical scores were improved compared with placebo. These translational results provide sufficient reason to proceed with further clinical testing of gene transfer protocols for the treatment of OA.

Adeno-associated viral vectors show serotype specific transduction of equine joint tissue explants and cultured monolayers

Adeno-associated virus (AAV) receptors range from heparan sulfate proteoglycan to sialic acid moieties present on cell surfaces. Abundance of the glycan profiles is greatly influenced by animal species, cell type, and culture conditions. The objective of this study was to determine whether AAV serotypes' transduction efficiencies specifically in the equine monolayer culture model are an accurate representation of transduction efficiencies in tissue explants, a model more closely related to in vivo transduction. It was found that AAV 2 and 2.5 transduced cells more efficiently in explants than in monolayers. Through experiments involving assessing enzyme degradation of cell surface proteoglycans, this change could not be attributed to differences in the extra cellular matrix (ECM), but a similar change in AAV 5 transduction efficiency could be readily explained by differences in cell surface sialylated glycan. Unexpectedly it was found that in a small but diverse sample of horses evidence for serum neutralizing antibodies was only found to AAV 5. This suggests a unique relationship between this capsid and the equine host or an unresolved relationship between similar bovine AAV and the AAV 5 capsid immune response.

Optimization of scAAVIL-1ra In Vitro and In Vivo to Deliver High Levels of Therapeutic Protein for Treatment of Osteoarthritis

Osteoarthritis (OA) affects over 40 million people annually. We evaluated interleukin-1 receptor antagonist (IL-1ra) gene transfer in an equine model based on IL-1ra protein therapy which inhibits inflammation through blocking IL-1. Using the self-complementary adeno-associated virus (scAAV)IL-1ra equine gene as a starting construct, we optimized the transgene cassette by analyzing promoters (cytomegalovirus (CMV) versus chicken β-actin hybrid (CBh)), coding sequences (optimized versus unoptimized), vector capsid (serotype 2 versus chimeric capsid), and biological activity in vitro. AAV serotypes 2 and 2.5 CMV scAAVoptIL-1ra were tested in equine joints. We evaluated two doses of scAAVIL-1ra, scAAVGFP, and saline. We developed a novel endoscopy procedure and confirmed vector-derived transgene expression (GFP) in chondrocytes 6 months post-injection. AAVIL-1ra therapeutic protein levels were 200-800 ng/ml of synovial fluid over 23 and 186 days, respectively. No evidence of intra-articular toxicity was detected and no vector genomes were found in contralateral joints based on GFP fluorescence microscopy and quantitative PCR. Finally, we assayed vector-derived IL-1ra activity based on functional assays which supported anti-inflammatory activity of our protein. These studies represent the first large animal intra-articular gene transfer approach with a therapeutic gene using scAAV and demonstrate high levels of protein production over extended time supporting further clinical investigation using scAAV gene therapy for OA.Molecular Therapy - Nucleic Acids (2013) 2, e70; doi:10.1038/mtna.2012.61; published online 5 February 2013.

IGF-1 alters the human parietal pleural electrochemical profile by inhibiting ion trans-cellular transportation after interaction with its receptor

OBJECTIVE

The effect of IGF-1 in the human pleural permeability and the underlying mechanisms involved were investigated.

DESIGN

Specimens from thoracic surgical patients were mounted in Ussing chambers. Solutions containing IGF-1 (1 nM-100 nM) and IGF-1 Receptor Inhibitor (1 μΜ), amiloride 10 μM (Na(+) channel blocker) and ouabain 1 mM (Na(+)-K(+) pump inhibitor) were used in order to investigate receptor and ion transporter involvement respectively. Trans-mesothelial Resistance (R(TM)) across the pleural membrane was determined as a permeability indicator. Immunohistochemistry for IGF-1 receptors was performed.

RESULTS

IGF-1 increased R(TM) when added on the interstitial surface for all concentrations (p=.008, 1 nM-100 nM) and decreased it on the mesothelial surface for higher concentrations (p=.046, 100 nM). Amiloride and ouabain inhibited this effect. The IGF-1 Receptor Inhibitor also totally inhibited this effect. Immonuhistochemistry demonstrated the presence of IGF-1 receptors in the pleura.

CONCLUSIONS

It is concluded that IGF-1 changes the electrophysiology of the human parietal pleura by hindering the normal ion transportation and therefore the pleural fluid recycling process. This event is achieved after IGF-1 interaction with its receptor which is present in the human pleura.

Mesenchymal stem cells and osteoarthritis: remedy or accomplice?

Multipotent mesenchymal stromal or stem cells (MSCs) are likely to be agents of connective tissue homeostasis and repair. Because the hallmark of osteoarthritis (OA) is degeneration and failure to repair connective tissues it is compelling to think that these cells have a role to play in OA. Indeed, MSCs have been implicated in the pathogenesis of OA and, in turn, progression of the disease has been shown to be therapeutically modulated by MSCs. This review discusses current knowledge on the potential of both marrow- and local joint-derived MSCs in OA, the mode of action of the cells, and possible effects of the osteoarthritic niche on the function of MSCs. The use of stem cells for repair of isolated cartilage lesions and strategies for modulation of OA using local cell delivery are discussed as well as therapeutic options for the future to recruit and appropriately activate endogenous progenitors and/or locally systemically administered MSCs in the early stages of the disease. The use of gene therapy protocols, particularly as they pertain to modulation of inflammation associated with the osteoarthritic niche, offer an additional option in the treatment of this chronic disease. In summary, elucidation of the etiology of OA and development of technologies to detect early disease, allied to an increased understanding of the role MSCs in aging and OA, should lead to more targeted and efficacious treatments for this debilitating chronic disease in the future.

Ex vivo serotype-specific transduction of equine joint tissue by self-complementary adeno-associated viral vectors

Cell transplantation for the treatment of joint disease is an important clinical tool. Genetic modification of cells before transplantation has shown enhanced healing. Ex vivo genetic modification of joint tissue cells with various adeno-associated virus (AAV) serotypes has not been investigated. The transduction efficiencies of self-complementary AAV serotypes (1-6 and 8) were determined in joint tissue containing chondrocytes and synoviocytes isolated from equine models. When comparing scAAV serotypes for efficient transduction ex vivo, in chondrocytes versus synoviocytes, serotypes 6 and 2, and serotypes 3 and 2, respectively, appeared superior for gene expression. Unlike adenoviral vectors, no upregulation of inflammatory markers, such as matrix metalloproteinases and aggrecanase, was seen on treatment of joint tissue with AAV vectors ex vivo. Our findings also corroborate that ex vivo transduction of joint tissue can result in high transgene protein levels over time, and transplantation modalities might be feasible using AAV vectors in the treatment of joint-related diseases.

Potential Use of Gene Transfer in Athletic Performance Enhancement

After only a short history of three decades from concept to practice, gene therapy has recently been shown to have potential to treat serious human diseases. Despite this success, gene therapy remains in the realm of experimental medicine, and much additional preclinical and clinical study will be necessary for proving the efficacy and safety of this approach in the treatment of diseases in humans. However, a potential complicating factor is that advances in gene transfer technology could be misused to enhance athletic performance in sports, in a practice termed "gene doping". Moreover, gene doping could be a precursor to a broader controversial agenda of human "genetic enhancement" with the potential for a significant long-term impact on society. This review addresses the possible ways in which knowledge and experience gained in gene therapy in animals and humans may be abused for enhancing sporting prowess. We provide an overview of recent progress in gene therapy, with potential application to gene doping and with the major focus on candidate performance-enhancement genes. We also discuss the current status of preclinical studies and of clinical trials that use these genes for therapeutic purposes. Current knowledge about the association between the natural "genetic make-up" of humans and their physical characteristics and performance potential is also presented. We address issues associated with the safety of gene transfer technologies in humans, especially when used outside a strictly controlled clinical setting, and the obstacles to translating gene transfer strategies from animal studies to humans. We also address the need for development and implementation of measures to prevent abuse of gene transfer technologies, and to pursue research on strategies for its detection in order to discourage this malpractice among athletes.