Gene therapy methods in bone and joint disorders

Promoter considerations in the design of lentiviral vectors for use in treating lysosomal storage diseases

More than 50 lysosomal storage diseases (LSDs) are associated with lysosomal dysfunctions with the frequency of 1:5,000 live births. As a result of missing enzyme activity, the lysosome dysfunction accumulates undegraded or partially degraded molecules, affecting the entire body. Most of them are life-threatening diseases where patients could die within the first or second decade of life. Approximately 20 LSDs have the approved treatments, which do not provide the cure for the disorder. Therefore, the delivery of missing genes through gene therapy is a promising approach for LSDs. Over the years, ex vivo lentiviral-mediated gene therapy for LSDs has been approached using different strategies. Several clinical trials for LSDs are under investigation.Ex vivo lentiviral-mediated gene therapy needs optimization in dose, time of delivery, and promoter-driven expression. Choosing suitable promoters seems to be one of the important factors for the effective expression of the dysfunctional enzyme. This review summarizes the research on therapy for LSDs that has used different lentiviral vectors, emphasizing gene promoters.

Pharmacological Targeting of Heme Oxygenase-1 in Osteoarthritis

Osteoarthritis (OA) is a common aging-associated disease that clinically manifests as joint pain, mobility limitations, and compromised quality of life. Today, OA treatment is limited to pain management and joint arthroplasty at the later stages of disease progression. OA pathogenesis is predominantly mediated by oxidative damage to joint cartilage extracellular matrix and local cells such as chondrocytes, osteoclasts, osteoblasts, and synovial fibroblasts. Under normal conditions, cells prevent the accumulation of reactive oxygen species (ROS) under oxidatively stressful conditions through their adaptive cytoprotective mechanisms. Heme oxygenase-1 (HO-1) is an iron-dependent cytoprotective enzyme that functions as the inducible form of HO. HO-1 and its metabolites carbon monoxide and biliverdin contribute towards the maintenance of redox homeostasis. HO-1 expression is primarily regulated at the transcriptional level through transcriptional factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), specificity protein 1 (Sp1), transcriptional repressor BTB-and-CNC homology 1 (Bach1), and epigenetic regulation. Several studies report that HO-1 expression can be regulated using various antioxidative factors and chemical compounds, suggesting therapeutic implications in OA pathogenesis as well as in the wider context of joint disease. Here, we review the protective role of HO-1 in OA with a focus on the regulatory mechanisms that mediate HO-1 activity.

Comparative intra-articular gene transfer of seven adeno-associated virus serotypes reveals that AAV2 mediates the most efficient transduction to mouse arthritic chondrocytes

Osteoarthritis (OA) is the most common arthropathy, characterized by progressive degeneration of the articular cartilage. Currently, there are no disease-modifying approaches for OA treatment. Adeno-associated virus (AAV)-mediated gene therapy has recently become a potential treatment for OA due to its exceptional characteristics; however, the tropism and transduction efficiency of different AAV serotypes to articular joints and the safety profile of AAV applications are still unknown. The present study aims to screen an ideal AAV serotype to efficiently transfer genes to arthritic cartilage. AAV vectors of different serotypes expressing eGFP protein were injected into the knee joint cavities of mice, with all joint tissues collected 30 days after AAV injection. The transduction efficiency of AAVs was quantified by assessing the fluorescent intensities of eGFP in the cartilage of knee joints. Structural and morphological changes were analyzed by toluidine blue staining. Changes to ECM metabolism and pyroptosis of chondrocytes were determined by immunohistochemical staining. Fluorescence analysis of eGFP showed that eGFP was expressed in the cartilage of knee joints injected with each AAV vector. Quantification of eGFP intensity indicated that AAV2, 7 and 8 had the highest transduction efficiencies. Both toluidine blue staining and Mankin score showed that AAV6 aggravated cartilage degeneration. The analysis of key molecules in ECM metabolism suggested that AAV5 and 7 significantly reduced collagen type II, while AAV9 increased ADAMTS-4 but decreased MMP-19. In addition, transduction with AAV2, 5, 7 and 8 had no obvious effect on pyroptosis of chondrocytes. Comprehensive score analysis also showed that AAV2 had the highest score in intra-articular gene transfer. Collectively, our findings point to AAV2 as the best AAV serotype candidate for gene transfer on arthritic cartilage, resulting in minimal impact to ECM metabolism and pyroptosis of chondrocytes.

Bone-targeting AAV-mediated silencing of Schnurri-3 prevents bone loss in osteoporosis

RNAi-based bone anabolic gene therapy has demonstrated initial success, but many practical challenges are still unmet. Here, we demonstrate that a recombinant adeno-associated virus 9 (rAAV9) is highly effective for transducing osteoblast lineage cells in the bone. The adaptor protein Schnurri-3 (SHN3) is a promising therapeutic target for osteoporosis, as deletion of shn3 prevents bone loss in osteoporotic mice and short-term inhibition of shn3 in adult mice increases bone mass. Accordingly, systemic and direct joint administration of an rAAV9 vector carrying an artificial-microRNA that targets shn3 (rAAV9-amiR-shn3) in mice markedly enhanced bone formation via augmented osteoblast activity. Additionally, systemic delivery of rAAV9-amiR-shn3 in osteoporotic mice counteracted bone loss and enhanced bone mechanical properties. Finally, we rationally designed a capsid that exhibits improved specificity to bone by grafting the bone-targeting peptide motif (AspSerSer)6 onto the AAV9-VP2 capsid protein. Collectively, our results identify a bone-targeting rAAV-mediated gene therapy for osteoporosis.

Codon-Optimization of Wild-Type Adeno-Associated Virus Capsid Sequences Enhances DNA Family Shuffling while Conserving Functionality

Adeno-associated virus (AAV) vectors have become one of the most widely used gene transfer tools in human gene therapy. Considerable effort is currently being focused on AAV capsid engineering strategies with the aim of developing novel variants with enhanced tropism for specific human cell types, decreased human seroreactivity, and increased manufacturability. Selection strategies based on directed evolution rely on the generation of highly variable AAV capsid libraries using methods such as DNA-family shuffling, a technique reliant on stretches of high DNA sequence identity between input parental capsid sequences. This identity dependence for reassembly of shuffled capsids is inherently limiting and results in decreased shuffling efficiency as the phylogenetic distance between parental AAV capsids increases. To overcome this limitation, we have developed a novel codon-optimization algorithm that exploits evolutionarily defined codon usage at each amino acid residue in the parental sequences. This method increases average sequence identity between capsids, while enhancing the probability of retaining capsid functionality, and facilitates incorporation of phylogenetically distant serotypes into the DNA-shuffled libraries. This technology will help accelerate the discovery of an increasingly powerful repertoire of AAV capsid variants for cell-type and disease-specific applications.

Tailoring the AAV2 capsid vector for bone-targeting

BACKGROUND

Targeting specific tissues remains a major challenge to the promise of gene therapy. For example, several strategies have failed to target adeno-associated virus 2 (AAV2) vectors, to bone. We have evaluated in vitro and in vivo the affinity of an AAV2 vector to bone matrix, hydroxyapatite (HA) to treat Mucopolysacccharidosis IVA.

METHODS

To increase vector affinity to HA, an aspartic acid octapeptide (D8) was inserted immediately after the N-terminal region of the VP2 capsid protein. The modified vector had physical titers and transduction efficiencies comparable to the unmodified vector.

RESULTS

The bone-targeting vector had significantly higher HA affinity and vector genome copies in bone than the unmodified vector. The modified vector was also released from HA, and its enzyme activity in bone, 3 months post infusion, was 4.7-fold higher than the unmodified vector.

CONCLUSION

Inserting a bone-targeting peptide into the vector capsid increases gene delivery and expression in the bone without decreasing enzyme expression. This approach could be a novel strategy to treat systemic bone diseases.

Gene Therapy with Tetracycline-Regulated Human Recombinant COLIA1 cDNA Direct Adenoviral Delivery Enhances Fracture Healing in Osteoporotic Rats

A number of previous studies have indicated that the genetic variation at the collage type I alpha 1 (COLIA1) gene locus influences susceptibility to osteoporosis. However, seldom have studies reported the effect of gene delivery using an adenovirus vector carrying human recombinant COLIA1 cDNA on stimulating osteogenic activity of osteoblasts and enhancing fracture healing of ovariectomized rats. The current study was performed to demonstrate whether direct gene delivery using an adenovirus vector carrying human recombinant COLIA1 cDNA could stimulate osteogenic activity of osteoblast in vitro and enhance fracture healing of ovariectomized rats in vivo. In vitro, the tet-on system regulated COLIA1 gene adenovirus was constructed and transfected to osteoblasts. COLIA1 mRNA and collagen type I levels were assessed by reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay to determine whether adenovirus transfected successfully. Osteogenic activity of the osteoblasts was assessed by alkaline phosphatase activity, immunohistochemical staining, immunofluorescent staining, mineralized matrix formation, and extracellular calcium levels. In vivo, adenovirus-delivered COLIA1 gene was injected into the fracture site of the tibia in an ovariectomized rat model of osteoporosis, and bone callus condition was assessed to determine whether the COLIA1 gene could accelerate osteoporotic fracture healing. In vitro, the results showed that COLIA1 gene adenovirus transfection could increase osteoblast COLIA1 gene expression and collagen type I protein synthesis, increase alkaline phosphatase activity, and stimulate calcium nodules formation, which exhibited a direct osteogenic effect on the osteoblasts. In vivo, local injection of COLIA1 gene adenovirus increased collagen type I expression, restored bone mineral density, and accelerated fracture healing in ovariectomized rats, without increasing serum collagen type I and liver COLIA1 mRNA levels. This study suggests direct gene delivery using an adenovirus carrying human COLIA1 cDNA can stimulate the osteogenic activity of osteoblasts in vitro and enhance bone fracture healing in vivo. The tet-on system is an ideal gene regulatory system for effective and safe regulation of the therapeutic gene.

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.

RNAi-mediated silencing of Atp6i and Atp6i haploinsufficiency prevents both bone loss and inflammation in a mouse model of periodontal disease

Periodontal disease affects about 80% of adults in America, and is characterized by oral bacterial infection-induced gingival inflammation, oral bone resorption, and tooth loss. Periodontitis is also associated with other diseases such as rheumatoid arthritis, diabetes, and heart disease. Although many efforts have been made to develop effective therapies for this disease, none have been very effective and there is still an urgent need for better treatments and preventative strategies. Herein we explored for the first time the possibility that adeno-associated virus (AAV)-mediated RNAi knockdown could be used to treat periodontal disease with improved efficacy. For this purpose, we used AAV-mediated RNAi knockdown of Atp6i/TIRC7 gene expression to target bone resorption and gingival inflammation simultaneously. Mice were infected with the oral pathogen Porphyromonas gingivalis W50 (P. gingivalis) in the maxillary periodontium to induce periodontitis. We found that Atp6i depletion impaired extracellular acidification and osteoclast-mediated bone resorption. Furthermore, local injection of AAV-shRNA-Atp6i/TIRC7 into the periodontal tissues in vivo protected mice from P. gingivalis infection-stimulated bone resorption by >85% and decreased the T-cell number in periodontal tissues. Notably, AAV-mediated Atp6i/TIRC7 knockdown also reduced the expression of osteoclast marker genes and inflammation-induced cytokine genes. Atp6i(+/-) mice with haploinsufficiency were similarly protected from P. gingivalis infection-stimulated bone loss and gingival inflammation. This suggests that AAV-shRNA-Atp6i/TIRC7 therapeutic treatment may significantly improve the health of millions who suffer from P. gingivalis-mediated periodontal disease.

Persistence, localization, and external control of transgene expression after single injection of adeno-associated virus into injured joints

A single intra-articular injection of adeno-associated virus (AAV) results in stable and controllable transgene expression in normal rat knees. Because undamaged joints are unlikely to require treatment, the study of AAV delivery in joint injury models is crucial to potential therapeutic applications. This study tests the hypotheses that persistent and controllable AAV-transgene expression are (1) highly localized to the cartilage when AAV is injected postinjury and (2) localized to the intra-articular soft tissues when AAV is injected preinjury. Two AAV injection time points, postinjury and preinjury, were investigated in osteochondral defect and anterior cruciate ligament transection models of joint injury. Rats injected with AAV tetracycline response element (TRE)-luciferase received oral doxycycline for 7 days. Luciferase expression was evaluated longitudinally for 6 months. Transgene expression was persistent and controllable with oral doxycycline for 6 months in all groups. However, the location of transgene expression was different: postinjury AAV-injected knees had luciferase expression highly localized to the cartilage, while preinjury AAV-injected knees had more widespread signal from intra-articular soft tissues. The differential transgene localization between preinjury and postinjury injection can be used to optimize treatment strategies. Highly localized postinjury injection appears advantageous for treatments targeting repair cells. The more generalized and controllable reservoir of transgene expression following AAV injection before anterior cruciate ligament transection (ACLT) suggests an intriguing concept for prophylactic delivery of joint protective factors to individuals at high risk for early osteoarthritis (OA). Successful external control of intra-articular transgene expression provides an added margin of safety for these potential clinical applications.

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.

Inhibiting periapical lesions through AAV-RNAi silencing of cathepsin K

Dental caries, one of the most prevalent infectious diseases worldwide, affects approximately 80% of children and the majority of adults. Dental caries may result in endodontic disease, leading to dental pulp necrosis, periapical inflammation and bone resorption, severe pain, and tooth loss. Periapical inflammation may also increase inflammation in other parts of the body. Although many studies have attempted to develop therapies for this disease, there is still an urgent need for effective treatments. In this study, we applied a novel gene therapeutic approach using recombinant adeno-associated virus (AAV)-mediated RNAi knockdown of Cathepsin K (Ctsk) gene expression, to target osteoclasts and periapical bone resorption in a mouse model. We found that AAV-sh-Cathepsin K (AAV-sh-Ctsk) impaired osteoclast function in vivo and furthermore reduced bacterial infection-stimulated bone resorption by 88%. Reduced periapical lesion size was accompanied by decreases in mononuclear leukocyte infiltration and inflammatory cytokine expression. Our study shows that AAV-RNAi silencing of Cathepsin K in periapical tissues can significantly reduce endodontic disease development, bone destruction, and inflammation in the periapical lesion. This is the first demonstration that AAV-mediated RNAi knockdown gene therapy may significantly reduce the severity of endodontic disease.

Growth factors and craniofacial surgery

The specialty of craniofacial surgery is broad and includes trauma, aesthetics, reconstruction of congenital deformities, and regeneration of tissues. Moreover, craniofacial surgery deals with a diverse range of tissues including both "soft" and "hard" tissues. Technological advances in materials and biological sciences and improved surgical techniques have remarkably improved clinical outcomes. The quest to raise the bar for patient care continues to inspire advances for predictable biological regeneration of soft and hard tissues. As a consequence of this quest for advancement, a wide spectrum of biologicals is becoming available to surgeons. Is the use of recombinant DNA engineered biologicals daring? Sensible? Logical? Timely? Safe? It is crucial for the practicing craniofacial surgeon to take a step back periodically and carefully review the biological factors that have the potential for dramatically altering the discipline of craniofacial surgery. With this emphasis, the coauthors of this article will focus on growth factor technology underscoring bone tissue regeneration. As the 21st-century matures, recombinant human biologicals will have an overwhelming impact on the practice of craniofacial surgery.

Gene therapy: implications for craniofacial regeneration

Gene therapy in the craniofacial region provides a unique tool for delivery of DNA to coordinate protein production in both time and space. The drive to bring this technology to the clinic is derived from the fact that more than 85% of the global population may at one time require repair or replacement of a craniofacial structure. This need ranges from mild tooth decay and tooth loss to temporomandibular joint disorders and large-scale reconstructive surgery. Our ability to insert foreign DNA into a host cell has been developing since the early uses of gene therapy to alter bacterial properties for waste cleanup in the 1980s followed by successful human clinical trials in the 1990s to treat severe combined immunodeficiency. In the past 20 years, the emerging field of craniofacial tissue engineering has adopted these techniques to enhance regeneration of mineralized tissues, salivary gland, and periodontium and to reduce tumor burden of head and neck squamous cell carcinoma. Studies are currently pursuing research on both biomaterial-mediated gene delivery and more clinically efficacious, although potentially more hazardous, viral methods. Although hundreds of gene therapy clinical trials have taken place in the past 20 years, we must still work to ensure an ideal safety profile for each gene and delivery method combination. With adequate genotoxicity testing, we can expect gene therapy to augment protein delivery strategies and potentially allow for tissue-specific targeting, delivery of multiple signals, and increased spatial and temporal control with the goal of natural tissue replacement in the craniofacial complex.

Investigation of the peak action wavelength of light-activated gene transduction

Light-activated gene transduction (LAGT) is an approach to localize gene therapy via preactivation of cells with UV light, which facilitates transduction by recombinant adeno-associated virus vectors. Prior studies demonstrated that UVC induces LAGT secondary to pyrimidine dimer formation, while UVA induces LAGT secondary to reactive oxygen species (ROS) generation. However, the empirical UVB boundary of these UV effects is unknown. Thus, we aimed to define the action spectra for UV-induced LAGT independent of DNA damage, and determine an optimal wavelength to maximize safety and efficacy. Results: UV at 288, 311 and 320nm produced significant dose-dependent LAGT effects, of which the maximum (800-fold) was observed with 4kJ/m² at 311nm. Consistent with its robust cytotoxicity, 288nm produced significantly high levels of DNA damage at all doses tested, while 311, 320 and 330nm did not generate pyrimidine dimers and produced low levels of DNA damage detected by comet assay. While 288nm failed to induce ROS, the other wavelengths were effective, with the maximum (10-fold) effect observed with 30 kJ/m² at 311nm. An in vivo pilot study assessing 311nm-induced LAGT of rabbit articular chondrocytes demonstrated a significant 6.6-fold (p<0.05) increase in transduction with insignificant cytotoxicity. Conclusion: 311nm was found to be the optimal wavelength for LAGT based on its superior efficacy at the peak dose, and its broad safety range that is remarkably wider than the other UV wavelengths tested.

Bioengineering strategies for regeneration of craniofacial bone: a review of emerging technologies

Although advances in surgical techniques and bone grafting have significantly improved the functional and cosmetic restoration of craniofacial structures lost because of trauma or disease, there are still significant limitations in our ability to regenerate these tissues. The regeneration of oral and craniofacial tissues presents a formidable challenge that requires synthesis of basic science, clinical science, and engineering technology. Tissue engineering is an interdisciplinary field of study that addresses this challenge by applying the principles of engineering to biology and medicine toward the development of biological substitutes that restore, maintain, and improve normal function. This review will explore the impact of biomaterials design, stem cell biology and gene therapy on craniofacial tissue engineering.

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.

Biological activation of bone-related biomaterials by recombinant adeno-associated virus vector

Gene therapy is a promising clinical tool that is no longer limited as a method to supplement genetic deficits, but rather is considered reliable for delivering proteins to specific tissues or cells. Recombinant adeno-associated virus (rAAV) vector is one of the most potent gene transfer vehicles. Many biomaterials have been used in reconstructive surgery, but their biological inactivity has limited their use. To overcome shortcomings of available bone-related biomaterials, we investigated the combination of rAAV with biomaterials. Taking advantage of the method of lyophilizing rAAV onto biomaterials, we showed that an rAAV coating successfully induced beta-galactosidase protein expression by rat fibroblasts on hydroxyapatite, beta-tricalcium phosphate, and titanium alloy in vitro. beta-Galactosidase expression was detected for 8 weeks after implantation of rAAV-coated hydroxyapatite into rat back muscles in vivo. A coating of bone morphogenetic protein-2-expressing rAAV induced significant de novo bone formation on hydroxyapatite in rat back muscles. Our study demonstrates that the combination of lyophilized rAAV and biomaterials presents a promising strategy for bone regenerative medicine.

Localized delivery of growth factors for periodontal tissue regeneration: role, strategies, and perspectives

Difficulties associated with achieving predictable periodontal regeneration, means that novel techniques need to be developed in order to regenerate the extensive soft and hard tissue destruction that results from periodontitis. Localized delivery of growth factors to the periodontium is an emerging and versatile therapeutic approach, with the potential to become a powerful tool in future regenerative periodontal therapy. Optimized delivery regimes and well-defined release kinetics appear to be logical prerequisites for safe and efficacious clinical application of growth factors and to avoid unwanted side effects and toxicity. While adequate concentrations of growth factor(s) need to be appropriately localized, delivery vehicles are also expected to possess properties such as protein protection, precision in controlled release, biocompatibility and biodegradability, self-regulated therapeutic activity, potential for multiple delivery, and good cell/tissue penetration. Here, current knowledge, recent advances, and future possibilities of growth factor delivery strategies are outlined for periodontal regeneration. First, the role of those growth factors that have been implicated in the periodontal healing/regeneration process, general requirements for their delivery, and the different material types available are described. A detailed discussion follows of current strategies for the selection of devices for localized growth factor delivery, with particular emphasis placed upon their advantages and disadvantages and future prospects for ongoing studies in reconstructing the tooth supporting apparatus.

Joint capsule treatment with enkephalin-encoding HSV-1 recombinant vector reduces inflammatory damage and behavioural sequelae in rat CFA monoarthritis

This study assessed enkephalin expression induced by intra-articular application of recombinant, enkephalin-encoding herpes virus (HSV-1) and the impact of expression on nociceptive behaviours and synovial lining inflammation in arthritic rats. Replication-conditional HSV-1 recombinant vectors with cDNA encoding preproenkephalin (HSV-ENK), or control transgene beta-galactosidase cDNA (HSV-beta-gal; control) were injected into knee joints with complete Freund's adjuvant (CFA). Joint temperatures, circumferences and nociceptive behaviours were monitored on days 0, 7, 14 and 21 post CFA and vector treatments. Lumbar (L4-6) dorsal root ganglia (DRG) and spinal cords were immunostained for met-enkephalin (met-ENK), beta-gal, HSV-1 proteins and Fos. Joint tissues were immunostained for met-ENK, HSV-1 proteins, and inflammatory mediators Regulated on Activation, Normal T-cell Expressed and Secreted (RANTES) and cyclo-oxygenase-2, or stained with haematoxylin and eosin for histopathology. Compared to exuberant synovial hypertrophy and inflammatory cell infiltration seen in arthritic rats treated with CFA only or CFA and HSV-beta-gal, the CFA- and HSV-ENK-treated arthritic rats had: (i) striking preservation of synovial membrane cytoarchitecture with minimal inflammatory cell infiltrates; (ii) significantly improved nociceptive behavioural responses to mechanical and thermal stimuli; (iii) normalized Fos staining in lumbar dorsal horn; and (iv) significantly increased met-ENK staining in ipsilateral synovial tissue, lumbar DRG and spinal cord. The HSV-1 and transgene product expression were confined to ipsilateral lumbar DRG (HSV-1, met-ENK, beta-gal). Only transgene product (met-ENK and beta-gal) was seen in lumbar spinal cord sections. Targeted delivery of enkephalin-encoding HSV-1 vector generated safe, sustained opioid-induced analgesia with protective anti-inflammatory blunting in rat inflammatory arthritis.

Influence of short-term adenoviral vector and prolonged lentiviral vector mediated bone morphogenetic protein-2 expression on the quality of bone repair in a rat femoral defect model

The objective of this study was to compare the efficacy of adenoviral and lentiviral regional gene therapy in a rat critical sized femoral defect model. The healing rates and quality of bone repair of femoral defects treated with syngeneic rat bone marrow cells (RBMCs) transduced with either lentiviral vector (Group I) or adenoviral vector (Group II) expressing bone morphogenetic protein-2 (BMP-2) gene were assessed. RBMCs transduced with the adenoviral vectors produced more than 3 times greater (p<0.001) BMP-2 when compared to RBMCs transduced with lentiviral vectors in an in vitro evaluation. Serial bioluminescent imaging demonstrated short duration luciferase expression (less than 3 weeks) in defects treated with RBMCs co-transduced with two adenoviral vectors (Group IV; adenovirus expressing BMP-2 and luciferase [Ad-BMP-2+Ad-Luc]). In contrast, the luciferase signal was present for 8 weeks in defects treated with RBMCs co-transduced with two lentiviral vectors (Group III; lentivirus expressing BMP-2 and luciferase gene [LV-BMP-2+LV-Luc]). There were no significant differences with respect to the radiological healing rates (p=0.12) in defects treated with lentiviral versus adenoviral mediated BMP-2 gene transfer. Biomechanical testing of healed Group I femoral specimens demonstrated significantly higher energy to failure (p<0.05) when compared to Group II defects. Micro CT analysis revealed higher bone volume/tissue volume fraction (p=0.04) in Group I defects when compared to Group II defects. In conclusion, prolonged BMP-2 expression associated with lentiviral mediated gene transfer demonstrated a trend towards superior quality of bone repair when compared to adenoviral mediated transfer of BMP-2. These results suggest that the bone repair associated with regional gene therapy is influenced not just by the amount of protein expression but also by duration of protein production. This observation needs validation in a more biologically challenging environment where differences in healing rates and quality of bone repair are more likely to be significantly different.