Gene therapy has a history of controversy. Encouraging results are starting to emerge from the clinic, but questions are still being asked about the safety of this new molecular medicine. With the development of a leukaemia-like syndrome in two of the small number of patients that have been cured of a disease by gene therapy, it is timely to contemplate how far this technology has come, and how far it still has to go.

Progress and problems with the use of viral vectors for gene therapy

Background Total hip or knee replacement is highly successful when judged by prosthesis-related outcomes. However, some people experience long-term pain. Objectives To review published studies in representative populations with total hip or knee replacement for the treatment of osteoarthritis reporting proportions of people by pain intensity. Data sources MEDLINE and EMBASE databases searched to January 2011 with no language restrictions. Citations of key articles in ISI Web of Science and reference lists were checked. Study eligibility criteria, participants and interventions Prospective studies of consecutive, unselected osteoarthritis patients representative of the primary total hip or knee replacement population, with intensities of patient-centred pain measured after 3 months to 5-year follow-up. Study appraisal and synthesis methods Two authors screened titles and abstracts. Data extracted by one author were checked independently against original articles by a second. For each study, the authors summarised the proportions of people with different severities of pain in the operated joint. Results Searches identified 1308 articles of which 115 reported patient-centred pain outcomes. Fourteen articles describing 17 cohorts (6 with hip and 11 with knee replacement) presented appropriate data on pain intensity. The proportion of people with an unfavourable long-term pain outcome in studies ranged from about 7% to 23% after hip and 10% to 34% after knee replacement. In the best quality studies, an unfavourable pain outcome was reported in 9% or more of patients after hip and about 20% of patients after knee replacement. Limitations Other studies reported mean values of pain outcomes. These and routine clinical studies are potential sources of relevant data. Conclusions and implications of key findings After hip and knee replacement, a significant proportion of people have painful joints. There is an urgent need to improve general awareness of this possibility and to address determinants of good and bad outcomes.

https://bmjopen.bmj.com/content/bmjopen/2/1/e000435.full.pdf

What proportion of patients report long-term pain after total hip or knee replacement for osteoarthritis? A systematic review of prospective studies in unselected patients

Biomaterials for bone tissue engineering

Mechanobiology of tendon

The knee meniscus: structure-function, pathophysiology, current repair techniques, and prospects for regeneration.

Our study evaluated tendon-to-bone healing in a dog model. Twenty adult mongrel dogs had a transplantation of the long digital extensor tendon into a 4.8-millimeter drill-hole in the proximal tibial metaphysis. Four dogs were killed at each of five time-periods (two, four, eight, twelve, and twenty-six weeks after the transplantation), and the histological and biomechanical characteristics of the tendon-bone interface were evaluated. Serial histological analysis revealed progressive reestablishment of collagen-fiber continuity between the bone and the tendon. A layer of cellular, fibrous tissue was noted between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey fibers. High-resolution radiographs showed remodeling of the trabecular bone that surrounded the tendon. At the two, four, and eight-week time-periods, all specimens had failed by pull-out of the tendon from the bone tunnel. The strength of the interface was noted to have significantly and progressively increased between the second and the twelfth week after the transplantation. At the twelve and twenty-six-week time-periods, all specimens had failed by pull-out of the tendon from the clamp or by mid-substance rupture of the tendon. The progressive increase in strength was correlated with the degree of bone ingrowth, mineralization, and maturation of the healing tissue, noted histologically.

Tendon-healing in a bone tunnel: a biomechanical and histological study in the dog.

Primary fibroblasts are not efficiently transduced by subgroup C adenovirus (Ad) vectors because they express low levels of the high-affinity Coxsackie virus and adenovirus receptor (CAR). In the present study, we have used primary human dermal fibroblasts as a model to explore strategies by which Ad vectors can be designed to enter cells deficient in CAR. Using an Ad vector expressing the human CAR cDNA (AdCAR) at high multiplicity of infection, primary fibroblasts were converted from being CAR deficient to CAR sufficient. Efficiency of subsequent gene transfer by standard Ad5-based vectors and Ad5-based vectors with alterations in penton and fiber was evaluated. Marked enhancement of binding and transgene expression by standard Ad5 vectors was achieved in CAR-sufficient fibroblasts. Expression by AdDeltaRGDbetagal, an Ad5-based vector lacking the arginine-glycine-aspartate (RGD) alphaV integrin recognition site from its penton base, was achieved in CAR-sufficient, but not CAR-deficient, cells. Fiber-altered Ad5-based vectors, including (a) AdF(pK7)betagal (bearing seven lysines on the end of fiber) (b) AdF(RGD)betagal (bearing a high-affinity RGD sequence on the end of fiber), and (c) AdF9sK betagal (bearing a short fiber and Ad9 knob), demonstrated enhanced gene transfer in CAR-deficient fibroblasts, with no further enhancement in CAR-sufficient fibroblasts. Together, these observations demonstrate that CAR deficiency on Ad targets can be circumvented either by supplying CAR or by modifying the Ad fiber to bind to other cell-surface receptors.

/pdf/car-dependent-and-car-independent-pathways-of-adenovirus-1o35imkk5a.pdf

CAR-dependent and CAR-independent pathways of adenovirus vector–mediated gene transfer and expression in human fibroblasts

Acceleration of cartilage repair by genetically modified chondrocytes over expressing bone morphogenetic protein-7.

Use of modular components in either primary or revision total knee arthroplasty allows the surgeon to achieve intraoperative customization, optimum kinematics, and improved fixation1-8,11,13,15. Modularity in total knee arthroplasty includes augmentation of the femoral component with distal or posterior metallic blocks, or both, and augmentation of the tibial component with metallic wedges or blocks. In addition, fixation of the intramedullary stems is possible, and this allows stress relief and load-sharing with the host bone1,6-8,11,12. Although such elaborate configurations are unnecessary for most primary total knee arthroplasties, many surgeons routinely use intraoperative customization in revision procedures and frequently this customization involves the stem1,2,4-8,12,14.

Concerns with respect to modularity in total knee arthroplasty have arisen because of the many junctions of modular components. Issues relating to metallic wear, fretting, and corrosion between the body of the prosthesis and the various modular components require the surgeon to understand the potential long-term problems2 and to proceed with caution. In addition, loosening of screws used to secure blocks, wedges, or the intramedullary stems can be a problem. Dissociation of modular components after implantation is quite rare; however, surgeons must be aware of the complication and be prepared to correct it2.

We present the cases of three patients who had disengagement of a locking screw from a modular stem that had been implanted in a revision total knee arthroplasty. In each instance, a screw had been used to reinforce the Morse taper junction between an intramedullary stem and the femoral component, as recommended by the manufacturer. Months after implantation, the screw disengaged from the femoral component and became an intra-articular loose …

Disengagement of a Locking Screw from a Modular Stem in Revision Total Knee Arthroplasty. A Report of Three Cases

To enhance the osteogenic activity of BMP, combination BMP2 and BMP7 gene transfer was performed. This approach led to a significant increase in osteoblastic differentiation of mesenchymal precursors compared with single BMP gene transfer in vitro. When tested in 78 rats, combination gene transfer enhanced mechanically stable spine fusion and bone formation rate versus single BMP gene transfer.



Introduction: Although clinical bone morphogenetic protein (BMP) therapy is effective, required doses are very high. Previous studies have suggested that the co-expression of two different BMP genes can result in the production of heterodimeric BMPs that may be more potent than homodimers. In this study, combined BMP2 and BMP7 gene transfer was performed to test whether this approach improves osteoblastic differentiation and bone formation compared with single BMP gene transfer.



Materials and Methods: A producer cell (A549) was co-transfected with adenovirus vectors encoding BMP2 (AdBMP2) and BMP7 (AdBMP7) or, as controls, each vector alone, AdNull (with no transgene) or no virus. Supernatants were compared for their ability to stimulate osteoblastic differentiation of C2C12 myoblasts and MC3T3-E1 pre-osteoblasts. In a rat posterolateral spine fusion model, co-administration of AdBMP2 and AdBMP7 was compared with treatment with each vector alone, AdNull or no virus in 78 rats. The spines were assessed 8 weeks after surgery for radiographic and mechanical fusion, bone formation, and mineralization.



Results: BMP2 and BMP7 were co-precipitated from supernatants of cells co-transfected with AdBMP2 and AdBMP7, indicating the presence of BMP2/7 heterodimer. Supernatants of co-transfected cells containing relatively low doses (7–140 ng/ml) of BMPs induced osteocalcin expression and alkaline phosphatase activity in both C2C12 and MC3T3-E1 cells, that were up to 6- and 40-fold higher, respectively, than levels induced by maximal doses (200–1000 ng/ml) of either BMP2 or BMP7 alone. In the spine fusion model, co-administration of AdBMP2 and AdBMP7 resulted in a significantly greater number of mechanically stable fusions and also 2-fold higher mineralization rate and bone volume in the fusion mass versus single BMP gene transfer (p < 0.02, all comparisons).



Conclusion: Combined BMP2 and BMP7 gene transfer is significantly more effective in inducing osteoblastic differentiation and spine fusion than individual BMP gene transfer.

Chisa Hidaka

Papers

Tendon-healing in a bone tunnel: a biomechanical and histological study in the dog.

CAR-dependent and CAR-independent pathways of adenovirus vector–mediated gene transfer and expression in human fibroblasts

Acceleration of cartilage repair by genetically modified chondrocytes over expressing bone morphogenetic protein-7.

Disengagement of a Locking Screw from a Modular Stem in Revision Total Knee Arthroplasty. A Report of Three Cases

Combined bone morphogenetic protein-2 and -7 gene transfer enhances osteoblastic differentiation and spine fusion in a rodent model.