In vivo gene delivery to articular chondrocytes mediated by an adeno-associated virus vector

Candidates for Intra-Articular Administration Therapeutics and Therapies of Osteoarthritis

Osteoarthritis (OA) of the knee is a disease that significantly decreases the quality of life due to joint deformation and pain caused by degeneration of articular cartilage. Since the degeneration of cartilage is irreversible, intervention from an early stage and control throughout life is important for OA treatment. For the treatment of early OA, the development of a disease-modifying osteoarthritis drug (DMOAD) for intra-articular (IA) injection, which is attracting attention as a point-of-care therapy, is desired. In recent years, the molecular mechanisms involved in OA progression have been clarified while new types of drug development methods based on gene sequences have been established. In addition to conventional chemical compounds and protein therapeutics, the development of DMOAD from the new modalities such as gene therapy and oligonucleotide therapeutics is accelerating. In this review, we have summarized the current status and challenges of DMOAD for IA injection, especially for protein therapeutics, gene therapy, and oligonucleotide therapeutics.

Ultraviolet light (365 nm) transmission properties of articular cartilage as a function of depth, extracellular matrix, and swelling

Current tissue engineering approaches for treatment of injured or diseased articular cartilage use ultraviolet light (UV) for in situ photopolymerization of biomaterials to fill chondral and osteochondral defects as well as resurfacing, stiffening and bonding the extracellular matrix and tissue interfaces. The most commonly used UV light wavelength is UVA 365 nm, the least cytotoxic and deepest penetrating. However, little information is available on the transmission of UVA 365 nm light through the cartilage matrix. In the present study, 365 nm UV light transmission was measured as a function of depth through 100 μm thick slices of healthy articular cartilage removed from mature bovine knees. Transmission properties were measured in normal (Native) cartilage and after swelling equilibration in phosphate-buffered saline (Swollen). Single-factor and multiple linear regression analyses were performed to determine depth-dependencies between the effective attenuation coefficients and proteoglycan, collagen and water contents. For both cartilages, a significant depth-dependency was found for the effective attenuation coefficients, being highest at the articular surface (superficial zone) and decreasing with depth. The effective attenuation coefficients for full-thickness cartilages were approximately a third lower than the total attenuation coefficients calculated from the individual slices. Analysis of absorption and scattering effects due to the ECM and chondrocytes found that UV light scatter coefficients were ∼10 times greater than absorption coefficients. The greater transmittance of UV light through the thicker cartilage was attributed to the collagen within the ECM causing significant backscatter forward reflectance.

Gene Delivery to Joints by Intra-Articular Injection

Most forms of arthritis are incurable, difficult to treat, and a major cause of disability in Western countries. Better local treatment of arthritis is impaired by the pharmacokinetics of the joint that make it very difficult to deliver drugs to joints at sustained, therapeutic concentrations. This is especially true of biologic drugs, such as proteins and RNA, many of which show great promise in preclinical studies. Gene transfer provides a strategy for overcoming this limitation. The basic concept is to deliver cDNAs encoding therapeutic products by direct intra-articular injection, leading to sustained, endogenous synthesis of the gene products within the joint. Proof of concept has been achieved for both in vivo and ex vivo gene delivery using a variety of vectors, genes, and cells in several different animal models. There have been a small number of clinical trials for rheumatoid arthritis (RA) and osteoarthritis (OA) using retrovirus vectors for ex vivo gene delivery and adeno-associated virus (AAV) for in vivo delivery. AAV is of particular interest because, unlike other viral vectors, it is able to penetrate deep within articular cartilage and transduce chondrocytes in situ. This property is of particular importance in OA, where changes in chondrocyte metabolism are thought to be fundamental to the pathophysiology of the disease. Authorities in Korea have recently approved the world's first arthritis gene therapy. This targets OA by the injection of allogeneic chondrocytes that have been transduced with a retrovirus carrying transforming growth factor-β₁ cDNA. Phase III studies are scheduled to start in the United States soon. Meanwhile, two additional Phase I trials are listed on Clinicaltrials.gov , both using AAV. One targets RA by transferring interferon-β, and the other targets OA by transferring interleukin-1 receptor antagonist. The field is thus gaining momentum and promises to improve the treatment of these common and debilitating diseases.

Safety and biodistribution assessment of sc-rAAV2.5IL-1Ra administered via intra-articular injection in a mono-iodoacetate-induced osteoarthritis rat model

Interleukin-1 (IL-1) plays an important role in the pathophysiology of osteoarthritis (OA), and gene transfer of IL-1 receptor antagonist (IL-1Ra) holds promise for OA treatment. A preclinical safety and biodistribution study evaluated a self-complementary adeno-associated viral vector carrying rat IL-1Ra transgene (sc-rAAV2.5rIL-1Ra) at 5 × 10⁸, 5 × 10⁹, or 5 × 10¹⁰ vg/knee, or human IL-1Ra transgene (sc-rAAV2.5hIL-1Ra) at 5 × 10¹⁰ vg/knee, in Wistar rats with mono-iodoacetate (MIA)–induced OA at days 7, 26, 91, 180, and 364 following intra-articular injection. The MIA-induced OA lesions were consistent with the published data on this model. The vector genomes persisted in the injected knees for up to a year with only limited vector leakage to systemic circulation and uptake in tissues outside the knee. Low levels of IL-1Ra expression and mitigation of OA lesions were observed in the vector-injected knees, albeit inconsistently. Neutralizing antibodies against the vector capsid developed in a dose-dependent manner, but only the human vector induced a small splenic T-cell immune response to the vector capsid. No local or systemic toxicity attributable to vector administration was identified in the rats as indicated by clinical signs, body weight, feed consumption, clinical pathology, and gross and microscopic pathology through day 364. Taken together, the gene therapy vector demonstrated a favorable safety profile.

Controlled release strategies for rAAV-mediated gene delivery

The development of efficient and safe gene transfer vectors capable of achieving appropriate levels of therapeutic gene expression in a target is one of the most challenging issues in clinical gene therapy. Diverse nonviral and viral gene vehicles have been developed to modify human cells and tissues that may be affected in a variety of diseases, among which the nonpathogenic, effective, and relatively safe recombinant adeno-associated viral (rAAV) vectors that make them a preferred gene delivery system to treat human disorders. Yet, their adapted clinical application is still limited by several hurdles including the presence of immune responses in the host organism and the existence of rate-limiting steps associated with physiological barriers. The use of controlled release strategies to deliver gene vectors such as rAAV may provide powerful tools to enhance the temporal and spatial presentation of therapeutic agents in a defined target and to overcome such obstacles in vivo. The goal of this review is to provide an overview of the most recent advances in gene therapy with a focus on rAAV vectors for clinical translation based on the controlled release from adapted biomaterials as a means to improve the performance of the gene transfer procedure. We also discuss the challenges that remain to be addressed for a safe and efficient adaptation and use of such approaches in the patient.

STATEMENT OF SIGNIFICANCE

The development of effective gene vectors to achieve suitable levels of a therapeutic agent in a target is a critical issue in clinical gene therapy and regenerative medicine. Diverse vehicles are currently available among which the nonpathogenic recombinant adeno-associated virus (rAAV) vectors, a preferred system to effectively treat human disorders. Yet, the clinical use of rAAV is impaired by the host immune responses and by rate-limiting steps of transgene expression. Controlled rAAV delivery systems may provide workable approaches to overcome such obstacles. Here, we give an overview of the most recent advances on the controlled release of vectors with a focus on rAAV using adapted biomaterials and discuss the key challenges for a safe translation in patients.

scAAVIL-1ra dosing trial in a large animal model and validation of long-term expression with repeat administration for osteoarthritis therapy

A gene therapeutic approach to treat osteoarthritis (OA) appears to be on the horizon for millions of people who suffer from this disease. Previously we described optimization of a scAAVIL-1ra gene therapeutic vector and initially tested this in an equine model verifying long-term intrasynovial IL-1ra protein at therapeutic levels. Using this vector, we carried out a dosing trial in six horses to verify protein levels and establish a dose that would express relevant levels of therapeutic protein for extended periods of time (8 months). A novel arthroscopic procedure used to detect green fluorescence protein (GFP) fluorescence intrasynovially confirmed successful transduction of the scAAVGFP vector in both the synovial and cartilage tissues. No evidence of intra-articular toxicity was detected. Immune responses to vector revealed development of neutralizing antibodies (Nabs) within 2 weeks of administration, which persisted for the duration of the study but did not lower protein expression intra-articularly. Re-dosing with a different serotype to attain therapeutic levels of protein confirmed establishment of successful transduction. This is the first study in an equine model to establish a dosing/redosing protocol, as well as examine the Nab response to capsid and supports further clinical investigation to determine the clinical efficacy of scAAVIL-1ra to treat OA.

Gene modification of mesenchymal stem cells and articular chondrocytes to enhance chondrogenesis

Current cell based treatment for articular cartilage and osteochondral defects are hampered by issues such as cellular dedifferentiation and hypertrophy of the resident or transplanted cells. The reduced expression of chondrogenic signalling molecules and transcription factors is a major contributing factor to changes in cell phenotype. Gene modification of chondrocytes may be one approach to redirect cells to their primary phenotype and recent advances in nonviral and viral gene delivery technologies have enabled the expression of these lost factors at high efficiency and specificity to regain chondrocyte function. This review focuses on the various candidate genes that encode signalling molecules and transcription factors that are specific for the enhancement of the chondrogenic phenotype and also how epigenetic regulators of chondrogenesis in the form of microRNA may also play an important role.

Local gene delivery of heme oxygenase-1 by adeno-associated virus into osteoarthritic mouse joints exhibiting synovial oxidative stress

OBJECTIVE

To evaluate the role of synovial oxidative stress on joint pathology in a spontaneous mouse model of osteoarthritis (OA) by intra-articular (IA) delivery of recombinant adeno-associated virus (rAAV) expressing anti-oxidant protein heme oxygenase-1 (HO-1).

METHODS

Joint transduction by rAAV vectors was evaluated with serotype 1, 2, 5 and 8 capsids carrying LacZ gene administered by IA injections into STR/ort mice. Transduced cell types were identified by β-galactosidase staining in sectioned joints. Effect of oxidative stress on AAV transduction of primary synoviocytes in vitro was quantitated by fluorescence-activated cell sorting (FACS) analysis. In vivo, the efficacy of rAAV1/HO-1 was tested by IA administration into STR/ort mice followed by histopathological scoring of cartilage. Levels of 3-nitrotyrosine (3-NT) and HO-1 were assessed by immunohistochemistry (IHC) of joint sections.

RESULTS

Administration of a rAAV1 based vector into OA mouse joints resulted in transduction of the synovium, joint capsule, adipocytes and skeletal muscle while none of the serotypes showed significant cartilage transduction. All OA joints exhibited significantly elevated levels of oxidative stress marker, 3-NT, in the synovium compared to OA-resistant CBA-strain of mice. In vitro studies demonstrated that AAV transgene expression in primary synoviocytes was augmented by oxidative stress induced by H(2)O(2) and that a rAAV expressing HO-1 reduced the levels of oxidative stress. In vivo, HO-1 was increased in the synovium of STR/ort mice. However, delivery of rAAV1/HO-1 into OA joints did not reduce cartilage degradation.

CONCLUSIONS

AAV-mediated HO-1 delivery into OA joints during active disease was not sufficient to improve cartilage pathology in this model.

Intraarticular gene delivery of CTLA4-FasL suppresses experimental arthritis

T lymphocytes are key inflammatory cells contributing significantly to the pathogenesis of Rheumatoid arthritis (RA). Biological treatments targeting T lymphocytes may provide an efficient approach for treatment of RA. CTLA4-FasL, a fusion product of extracellular domains of CTLA4 and FasL, integrating two inhibitory elements against T cells into one molecule, might be a desirable derivative of engineered soluble FasL or CTLA4 and have therapeutic potential in RA. The aim of this study was to investigate whether simultaneous induction of Fas-mediated apoptosis and blockade of co-stimulation signal by CTLA4-FasL gene delivery has a suppressive effect on adjuvant-induced arthritis (AIA) in Lewis rats. Recombinant adeno-associated virus (rAAV) vectors encoding rat CTLA4-FasL fusion gene (rAAV.CTLA4-FasL) or enhanced green fluorescent protein (rAAV.EGFP) were injected intraarticularly into both ankle joints after immunization. The ankles were monitored by measures of clinical, histological and inflammatory cytokines' changes. Treatment using rAAV.CTLA4-FasL resulted in a significant suppression of AIA compared with rAAV.EGFP control, as reflected in the mainly clinical signs including articular index, ankle joint thickness and paw swelling and typically histological characters of arthritic joints including synovial hyperplasia, inflammatory cells infiltration and cartilage degradation. Treatment with rAAV.CTLA4-FasL also significantly decreased the levels of key proinflammatory cytokines in AIA joints. Moreover, local productions of transgene mRNA and protein of CTLA4-FasL were found in injected joints without systemic distribution. Our results indicate that rAAV.CTLA4-FasL profoundly suppressed experimental model of RA, implicating the potential therapeutic applications for suppression of RA by local joint delivery of CTLA4-FasL.

Inflammation and immune response of intra-articular serotype 2 adeno-associated virus or adenovirus vectors in a large animal model

Intra-articular gene therapy has potential for the treatment of osteoarthritis and rheumatoid arthritis. To quantify in vitro relative gene transduction, equine chondrocytes and synovial cells were treated with adenovirus vectors (Ad), serotype 2 adeno-associated virus vectors (rAAV2), or self-complementary (sc) AAV2 vectors carrying green fluorescent protein (GFP). Using 6 horses, bilateral metacarpophalangeal joints were injected with Ad, rAAV2, or scAAV2 vectors carrying GFP genes to assess the in vivo joint inflammation and neutralizing antibody (NAb) titer in serum and joint fluid. In vitro, the greater transduction efficiency and sustained gene expression were achieved by scAAV2 compared to rAAV2 in equine chondrocytes and synovial cells. In vivo, AAV2 demonstrated less joint inflammation than Ad, but similar NAb titer. The scAAV2 vectors can induce superior gene transduction than rAAV2 in articular cells, and both rAAV2 and scAAV2 vectors were showed to be safer for intra-articular use than Ad vectors.

Exploiting natural diversity of AAV for the design of vectors with novel properties

Twelve AAV serotypes have been described so far in human and nonhuman primate (NHP) populations while surprisingly high diversity of AAV sequences is detected in tissue biopsies. The analysis of these novel AAV sequences has indicated a rapid evolution of the viral genome both by accumulation of mutations and recombination. This chapter describes how this rich resource of naturally evolved sequences is used to derive gene transfer vectors with a wide array of activities depending on the nature of the cap gene used in the packaging system. AAV2-based recombinant genomes have been packaged in dozens of different capsid types, resulting in a wide array of "pseudotyped vectors" that constitute a rich resource for the development of gene therapy clinical trials. We describe a polymerase chain reaction-based molecular rescue method for novel AAV isolation that uses primers designed to recognize the highly conserved regions in known AAV isolates and generate amplicons across the hypervariable regions of novel AAV genomes present in the analyzed sample.

Intra-articular gene delivery and expression of interleukin-1Ra mediated by self-complementary adeno-associated virus

BACKGROUND

The adeno-associated virus (AAV) has many safety features that favor its use in the treatment of arthritic conditions; however, the conventional, single-stranded vector is inefficient for gene delivery to fibroblastic cells that primarily populate articular tissues. This has been attributed to the inability of these cells to convert the vector to a double-stranded form. To overcome this, we evaluated double-stranded self-complementary (sc) AAV as a vehicle for intra-articular gene delivery.

METHODS

Conventional and scAAV vectors were used to infect lapine articular fibroblasts in culture to determine transduction efficiency, transgene expression levels, and nuclear trafficking. scAAV containing the cDNA for interleukin (IL)-1 receptor antagonist (Ra) was delivered to the joints of naïve rabbits and those with IL-1beta-induced arthritis. From lavage of the joint space, levels of transgenic expression and persistence were measured by enzyme-linked immunosorbent assay. Infiltrating leukocytes were quantified using a hemocytometer.

RESULTS

Transgene expression from scAAV had an earlier onset and was approximately 25-fold greater than conventional AAV despite the presence of similar numbers of viral genomes in the nuclei of infected cells. Fibroblasts transduced with scAAV produced amounts of IL1-Ra comparable to those transduced with adenoviral and lentiviral vectors. IL1-Ra was present in lavage fluid of most animals for 2 weeks in sufficient quantities to inhibit inflammation of the IL-1beta-driven model. Once lost, neither subsequent inflammatory events, nor re-administration of the virus could re-establish transgene expression.

CONCLUSIONS

scAAV-mediated intra-articular gene transfer is robust and similarly efficient in both normal and inflamed joints; the resulting transgenic expression is sufficient to achieve biological relevance in joints of human proportion.

Orthopedic gene therapy in 2008

Orthopedic disorders, although rarely fatal, are the leading cause of morbidity and impose a huge socioeconomic burden. Their prevalence will increase dramatically as populations age and gain weight. Many orthopedic conditions are difficult to treat by conventional means; however, they are good candidates for gene therapy. Clinical trials have already been initiated for arthritis and the aseptic loosening of prosthetic joints, and the development of bone-healing applications is at an advanced, preclinical stage. Other potential uses include the treatment of Mendelian diseases and orthopedic tumors, as well as the repair and regeneration of cartilage, ligaments, and tendons. Many of these goals should be achievable with existing technologies. The main barriers to clinical application are funding and regulatory issues, which in turn reflect major safety concerns and the opinion, in some quarters, that gene therapy should not be applied to nonlethal, nongenetic diseases. For some indications, advances in nongenetic treatments have also diminished enthusiasm. Nevertheless, the preclinical and early clinical data are impressive and provide considerable optimism that gene therapy will provide straightforward, effective solutions to the clinical management of several common debilitating disorders that are otherwise difficult and expensive to treat.

Gene therapy of the rheumatic diseases: 1998 to 2008

During the decade since the launch of Arthritis Research, the application of gene therapy to the rheumatic diseases has experienced the same vicissitudes as the field of gene therapy as a whole. There have been conceptual and technological advances and an increase in the number of clinical trials. However, funding has been unreliable and a small number of high-profile deaths in human trials, including one in an arthritis gene therapy trial, have provided ammunition to skeptics. Nevertheless, steady progress has been made in a number of applications, including rheumatoid arthritis and osteoarthritis, Sjögren syndrome, and lupus. Clinical trials in rheumatoid arthritis have progressed to phase II and have provided the first glimpses of possible efficacy. Two phase I protocols for osteoarthritis are under way. Proof of principle has been demonstrated in animal models of Sjögren syndrome and lupus. For certain indications, the major technological barriers to the development of genetic therapies seem to have been largely overcome. The translational research necessary to turn these advances into effective genetic medicines requires sustained funding and continuity of effort.

Perspectives on the use of gene therapy for chronic joint diseases

Advances in molecular and cellular biology have identified a wide variety of proteins including targeted cytokine inhibitors, immunomodulatory proteins, cytotoxic mediators, angiogenesis inhibitors, and intracellular signalling molecules that could be of great benefit in the treatment of chronic joint diseases, such as osteo- and rheumatoid arthritis. Unfortunately, protein-based drugs are difficult to administer effectively. They have a high rate of turnover, requiring frequent readministration, and exposure in non-diseased tissue can lead to serious side effects. Gene transfer technologies offer methods to enhance the efficacy of protein-based therapies, enabling the body to produce these molecules locally at elevated levels for extended periods. The proof of concept of gene therapies for arthritis has been exhaustively demonstrated in multiple laboratories and in numerous animal models. This review attempts to condense these studies and to discuss the relative benefits and limitations of the methods proposed and to discuss the challenges toward translating these technologies into clinical realities.

IGF-1 gene therapy to protect articular cartilage in a rat model of joint damage

INTRODUCTION

An adeno-associated virus (AAV) derived vector in gene transfer model that induces IGF-1 expression could repair articular cartilage.

MATERIALS AND METHODS

Male Wistar rats, 150 and 200 g, and 7 weeks old, were used. Effectiveness of constructed vectors was assayed inoculating them in rat knees of control and damaged animals either mechanically or by collagen-induced arthritis. Inoculation was intra-articular with 50 microL of recombinant AAV-Luciferase (1.25 x 10(8) particles). The rats were killed after 1, 2, 4 and 8 weeks. IGF-I activity was analyzed by injecting 50 microL of recombinant AAV (1.25 x 10(8) particles) in animals with damaged knees. Final analysis was performed after 8 weeks.

RESULTS

The activity of AAV vectors in vitro shows the presence of mRNA coding to IGF-I in cells infected with AAV-IGF and not in control cells without viral vectors and an increase in secreted IGF-I protein in culture medium. In vivo, AAV derived vectors induced protein expression in cartilage 2 months after inoculation. In the animals killed after 1 and 2 weeks, no significant increase in the reaction of luciferase was observed (P > 0.05). In the group of animals with no injury an increase was observed at 4 weeks, which was more marked and significant after 8 weeks (P = 0.029). The same behavior occurred in the animals with induced arthritis and in the mechanical injury group. In the levels of expression after 8 weeks, no significant differences were found between the two groups of injured animals and the group of healthy animals infected with the virus. The joints of the animals that were subjected to injuries in the cartilage and inoculated with AAV-IGF-I presented a similar appearance to those animals inoculated with saline solution.

CONCLUSION

Autoimmune and mechanical lesions did not show improvement in the state of its cartilage after the treatment. The use of AAV vectors capable of inducing the expression of IGF-I in vitro is therefore not sufficient to protect the cartilage from the serious damage.

Gene therapy for articular cartilage repair

Articular cartilage serves as the gliding surface of joints. It is susceptible to damage from trauma and from degenerative diseases. Restoration of damaged articular cartilage may be achievable through the use of cell-regulatory molecules that augment the reparative activities of the cells, inhibit the cells' degradative activities, or both. A variety of such molecules have been identified. These include insulin-like growth factor I, fibroblast growth factor 2, bone morphogenetic proteins 2, 4, and 7, and interleukin-1 receptor antagonist. It is now possible to transfer the genes encoding such molecules into articular cartilage and synovial lining cells. Although preliminary, data from in-vitro and in-vivo studies suggest that gene therapy can deliver such potentially therapeutic agents to protect existing cartilage and to build new cartilage.

Adeno-associated viral gene transfer of transforming growth factor-beta1 to human mesenchymal stem cells improves cartilage repair

Bone marrow cells are routinely accessed clinically for cartilage repair. This study was performed to determine whether adeno-associated virus (AAV) effectively transduces human bone marrow-derived mesenchymal stem cells (hMSC) in vitro, whether AAV infection interferes with hMSC chondrogenesis and whether AAV-transforming growth factor-beta-1 (TGF-beta1)-transduced hMSC can improve cartilage repair in vivo. Adult hMSC were transduced with AAV-green fluorescent protein (GFP) or AAV-transforming growth factor beta1 (TGF beta1) and studied in pellet cultures. For in vivo studies, AAV-GFP and AAV-TGF-beta1-transduced hMSCs were implanted into osteochondral defects of 21 athymic rats. GFP was detected using fluorescent microscopy. Cartilage repair was assessed using gross and histological analysis at 4, 8 and 12 weeks. In pellet culture, GFP expression was visualized in situ through 21 days in vitro. In vivo GFP transgene expression was observed by in situ fluorescent surface imaging in 100% of GFP implanted defects at 2 , 67% at 8 and 17% at 12 weeks. Improved cartilage repair was observed in osteochondral defects implanted with AAV-TGF-beta1-transduced hMSC at 12 weeks (P=0.0047). These results show that AAV is a suitable vector for gene delivery to improve the cartilage repair potential of human mesenchymal stem cells.

Tissue-Engineering zur Knorpelreparatur verbessert durch Gentransfer

Cartilage tissue engineering is the creation of functional substitutes of native articular cartilage in bioreactors by attaching chondrogenic cells to polymer scaffolds. One limitation of tissue engineering is the delivery of regulatory signals to cells according to specific temporal and spatial patterns. Using gene transfer techniques, polypeptide growth factor genes such as the human insulin-like growth factor I (IGF-I) gene can be transferred into chondrocytes. When these modified cells are used for cartilage tissue engineering, the resulting cartilaginous constructs have improved structural and functional characteristics compared to constructs based on nonmodified cells. The combination of cartilage tissue engineering with overexpression of potential therapeutic genes using gene transfer technologies provides a basis for the development of novel molecular therapies for the repair of cartilage defects.

The use of recombinant adeno-associated virus for skeletal gene therapy

OBJECTIVES

To provide a comprehensive literature review describing recent developments of the recombinant adeno-associated virus (rAAV) vector and exploring the therapeutic application of rAAV for bone defects, cartilage lesions and rheumatoid arthritis.

DESIGN

Narrative review.

RESULT

The review outlines the serotypes and genome of AAV, integration and life cycle of the rAAV vectors, the immune response and regulating system for AAV gene therapy. Furthermore, the advancements of rAAV gene therapy for bone growth together with cartilage repair are summarized.

CONCLUSION

Recombinant adeno-associated virus vector is perceived to be one of the most promising vector systems for bone and cartilage gene therapy approaches and further investigations need to be carried out for craniofacial research.

Tendon Healing In Vitro: Adeno-Associated Virus-2 Effectively Transduces Intrasynovial Tenocytes with Persistent Expression of the Transgene, but Other Serotypes Do Not

BACKGROUND

Transfer of exogenous growth factor genes to injured tendons offers a promising method for strengthening tendon repairs. Adeno-associated virus vectors have advantages of being both nonpathogenic and nontoxic. The authors explored the efficiency of transduction of intrasynovial tenocytes with different serotypes of adeno-associated virus (AAV) and the persistency of its expression of a growth factor transgene.

METHODS

Tenocytes were obtained from cultures of rat intrasynovial tendons and distributed to 82 wells in eight culture plates and to 30 culture dishes. The tenocytes in the wells were treated with AAV1, AAV2, AAV3, AAV4, AAV5, AAV7, and AAV8 vectors containing the lacZ gene, and plasmid vectors (pCMVbeta-lacZ). The tenocytes were stained with in situ beta-galactosidase 5 days later. The basic fibroblast growth factor (bFGF) gene was cloned to the AAV2 vector to construct the AAV2-bFGF vector, which transduced tenocytes in culture dishes. Expression of the transgene was measured over 3 weeks and analyzed statistically.

RESULTS

AAV2 effectively delivered exogenous genes to proliferating intrasynovial tenocytes. In contrast, other tested adeno-associated viruses transduced tenocytes minimally or not at all. The efficiency of gene transfer by AAV2, indicated by the percentage of cells with positive beta-galactosidase staining, was significantly greater than that by a plasmid vector (p = 0.001). Expression of the bFGF gene in tenocytes transduced with the AAV2-bFGF was significantly higher than that in the control over the 3-week period (p < 0.01).

CONCLUSIONS

Gene transfer to tenocytes by AAV2 is more efficient than that by a plasmid vector. However, other adeno-associated virus serotypes cannot effectively transduce tenocytes. The bFGF gene can be delivered to intrasynovial tenocytes by the AAV2 vector effectively, and the gene transfer significantly increases expression of bFGF gene over 3 weeks.

Gene therapy works in animal models of rheumatoid arthritis...so what!

Rheumatoid arthritis (RA) is a systemic disease with polyarticular manifestation of chronic inflammation in the knees and small joints of hand and feet. The current systemic anti-tumor necrosis factor (TNF)-alpha therapies with biologics ameliorate disease in 60% to 70% of RA patients. However, biologics must be given systemically in relatively high dosages to achieve constant therapeutic levels in the joints, and side effects have been reported. To this end, local gene delivery can provide an alternative approach to achieve high, long-term expression of biologics, optimizing the therapeutic efficacy and minimizing systemic exposure. Evidence from animal models convincingly supports the application of local gene therapy in rheumatoid arthritis, but preclinical studies remain necessary to evaluate the merge of cell-specific targeting, viral vector development, and disease-regulated transgene expression to optimize efficacy and safety.

Evaluation of permissiveness and cytotoxic effects in equine chondrocytes, synovial cells, and stem cells in response to infection with adenovirus 5 vectors for gene delivery

OBJECTIVE

To evaluate host cell permissiveness and cytotoxic effects of recombinant and modified adenoviral vectors in equine chondrocytes, synovial cells, and bone marrow-derived mesenchymal stem cells (BMD-MSCs).

SAMPLE POPULATION

Articular cartilage, synovium, and bone marrow from 15 adult horses.

PROCEDURES

Equine chondrocytes, synovial cells, and BMD-MSCs and human carcinoma (HeLa) cells were cultured and infected with an E-1-deficient adenovirus vector encoding the beta-galactosidase gene or the green fluorescent protein gene (Ad-GFP) and with a modified E-1-deficient vector with the arg-gly-asp capsid peptide insertion and containing the GFP gene (Ad-RGD-GFP). Percentages of transduced cells, total and transduced cell counts, and cell viability were assessed 2 and 7 days after infection.

RESULTS

-Permissiveness to adenoviral vector infection was significantly different among cell types and was ranked in decreasing order as follows: HeLa cells > BMD-MSCs > chondrocytes > synovial cells. Morphologic signs of cytotoxicity were evident in HeLa cells but not in equine cells. Numbers of transduced cells decreased by day 7 in all cell types except equine BMD-MSCs. Transduction efficiency was not significantly different between the Ad-GFP and Ad-RGD-GFP vectors.

CONCLUSION AND CLINICAL RELEVANCE

Sufficient gene transfer may be achieved by use of an adenovirus vector in equine cells. High vector doses can be used in equine cells because of relative resistance to cytotoxic effects in those cells. Greater permissiveness and sustained expression of transgenes in BMD-MSCs make them a preferential cell target for gene therapy in horses.

Gene therapy for cartilage defects

Focal defects of articular cartilage are an unsolved problem in clinical orthopaedics. These lesions do not heal spontaneously and no treatment leads to complete and durable cartilage regeneration. Although the concept of gene therapy for cartilage damage appears elegant and straightforward, current research indicates that an adaptation of gene transfer techniques to the problem of a circumscribed cartilage defect is required in order to successfully implement this approach. In particular, the localised delivery into the defect of therapeutic gene constructs is desirable. Current strategies aim at inducing chondrogenic pathways in the repair tissue that fills such defects. These include the stimulation of chondrocyte proliferation, maturation, and matrix synthesis via direct or cell transplantation-mediated approaches. Among the most studied candidates, polypeptide growth factors have shown promise to enhance the structural quality of the repair tissue. A better understanding of the basic scientific aspects of cartilage defect repair, together with the identification of additional molecular targets and the development of improved gene-delivery techniques, may allow a clinical translation of gene therapy for cartilage defects. The first experimental steps provide reason for cautious optimism.

Gene therapy as a therapeutic approach for the treatment of rheumatoid arthritis: innovative vectors and therapeutic genes

In recent years, significant progress has been made in the treatment of rheumatoid arthritis (RA). In addition to conventional therapy, novel biologicals targeting tumour necrosis factor-alpha have successfully entered the clinic. However, the majority of the patients still has some actively inflamed joints and some patients suffer from side-effects associated with the high systemic dosages needed to achieve therapeutic levels in the joints. In addition, due to of the short half-life of these proteins there is a need for continuous, multiple injections of the recombinant protein. An alternative approach might be the use of gene transfer to deliver therapeutic genes locally at the site of inflammation. Several viral and non-viral vectors are being used in animal models of RA. The first gene therapy trials for RA have already entered the clinic. New vectors inducing long-term and regulated gene expression in specific tissue are under development, resulting in more efficient gene transfer, for example by using distinct serotypes of viral vectors such as adeno-associated virus. This review gives an overview of some promising vectors used in RA research. Furthermore, several therapeutic genes are discussed that could be used for gene therapy in RA patients.

Improved tissue repair in articular cartilage defects in vivo by rAAV-mediated overexpression of human fibroblast growth factor 2

Therapeutic gene transfer into articular cartilage is a potential means to stimulate reparative activities in tissue lesions. We previously demonstrated that direct application of recombinant adeno-associated virus (rAAV) vectors to articular chondrocytes in their native matrix in situ as well as sites of tissue damage allowed for efficient and sustained reporter gene expression. Here we test the hypothesis that rAAV-mediated overexpression of fibroblast growth factor 2 (FGF-2), one candidate for enhancing the repair of cartilage lesions, would lead to the production of a biologically active factor that would facilitate the healing of articular cartilage defects. In vitro, FGF-2 production from an rAAV-delivered transgene was sufficient to stimulate chondrocyte proliferation over a prolonged period of time. In vivo, application of the therapeutic vector significantly improved the overall repair, filling, architecture, and cell morphology of osteochondral defects in rabbit knee joints. Differences in matrix synthesis were also observed, although not to the point of statistical significance. This process may further benefit from cosupplementation with other factors. These results provide a basis for rAAV application to sites of articular cartilage damage to deliver agents that promote tissue repair.

Future treatment of osteoarthritis

Osteoarthritis represents an advanced stage of disease progression caused in part by injury, loss of cartilage structure and function, and an imbalance in inflammatory and noninflammatory pathways. The burden of this disease will increase in direct proportion to the increase in the older adult population. Research on current and experimental treatment protocols are reviewed, including the effect of hyaluronic acid in both in vitro and in vivo studies, autologous chondrocyte and osteochondral plug implantation, and gene therapy. Disease-modifying osteoarthritis drugs and in vivo studies of glucosamine and chondroitin sulfate are reviewed.