Background aims. TissueGene-C (TG-C) represents a cell-mediated gene therapy for localized delivery of allogeneic chondrocytes expressing transforming growth factor (TGF)-β1 directly to the damaged knee joint. Untransduced human chondrocytes (hChonJ cells) have also been incorporated into the TG-C product at a 3:1 ratio with TGF-β1-expressing chondrocytes (hChonJb#7) in order to help fill in the defect and as target cells for the actions of the expressed TGF-β1.Methods.A phase I dose-escalating clinical trial was performed to evaluate the safety and biologic activity of TG-C in patients with advanced osteoarthritis of the knee joint (full thickness cartilage defect) that was refractory to existing non-operative therapies. Following a single intra-articular injection into the joint space of the damaged knee, patients were monitored for safety, and an evaluation was performed to assess the pharmacokinetics and biologic activity of TG-C.Results.There were no treatment-related serious adverse events. Swelling, effusion and minor localized reactions such as warming sensation or itching were observed in a dose-dependent manner at the injection site. Knee evaluation scores seemed to indicate a dose-dependent trend toward efficacy; however, patient numbers were not sufficient to determine statistical significance.Conclusions.Overall, there were no significant safety issues related to the administration of TG-C, with only some minor injection site reactions observed. Additionally, knee scoring analyzes indicated a possibility that TG-C may contribute to improvement of arthritic symptoms. More study is warranted to evaluate further the safety and determine the potential efficacy of TG-C.

There have been major changes since the incidents of leukemia development in X-SCID patients after the treatments using retroviral gene therapy. Due to the risk of oncogenesis caused by retroviral insertional activation of host genes, most of the efforts focused on the lentiviral therapies. However, a relative clonal dominance was detected in a patient with β-thalassemia Major, two years after the subject received genetically modified hematopoietic stem cells using lentiviral vectors. This disappointing result of the recent clinical trial using lentiviral vector tells us that the current and most advanced vector systems does not have enough safety. In this review, various safety features that have been tried for the retroviral gene therapy are introduced and the possible new ways of improvements are discussed. Additional feature of chromatin insulators, co-transduction of a suicidal gene under the control of an inducible promoter, conditional expression of the transgene only in appropriate target cells, targeted transduction, cell type-specific expression, targeted local administration, splitting of the viral genome, and site specific insertion of retroviral vector are discussed here.

Carbon monoxide (CO) is one of the most-studied molecules among the many modern industrial chemical reactions available. Following the Langmuir-Hinshelwood mechanism, CO conversion starts with adsorption on a catalyst surface, which is a crucially important stage in the kinetics of the catalytic reaction. Stepped surfaces show enhanced catalytic activity because they, by nature, have dense active sites. Recently, it was found that surface-sensitive adsorption of CO is strongly related to surface restructuring via roughening of a stepped surface. In this scanning tunneling microscopy study, we observed the thermal evolution of surface restructuring on a representative stepped platinum catalyst, Pt(557). CO adsorption at 1.4 mbar CO causes the formation of a broken-step morphology, as well as CO-induced triangular Pt clusters that exhibit a reversible disordered-ordered transition. Thermal instability of the CO-induced platinum clusters on the stepped surface was observed, which is associated with the reorganization of the repulsive CO-CO interactions at elevated temperature.

The purpose of this study was to investigate the efficacy of cartilage regeneration when using a mixture of transforming growth factor-beta1 (TGF-beta1)-producing human chondrocytes (hChon-TGF-beta1) and primary human chondrocytes (hChon) ("mixed cells"), compared with either hChon-TGF-beta1 or hChon cells alone. Specifically, mixed cells or hChon cells were first injected intradermally into the backs of immune-deficient nude mice to test the feasibility of cartilage formation in vivo. Both the mixed cells and the hChon-TGF-beta1 cells alone induced cartilage formation in nude mice, whereas hChon cells alone did not. To further test the efficacy of the cells in generating cartilage, an artificially induced partial thickness defect of the femoral condyle of a rabbit knee joint was loaded with hChon-TGF-beta1 cells with or without mixing additional untransduced hChon cells, and hyaline cartilage regeneration was observed at 4 or 6 weeks. The efficiency of complete filling of the defect and the quality of tissue generated after implanting were evaluated on the basis of a histological grading system modified from O'Driscoll et al. (J. Bone Joint Surg. 70A, 595, 1988). Significantly, mixed cells (14.2 +/- 0.9) produced significantly better results than hChon-TGF-beta1 (9.0 +/- 1.7) or hChon (8.0 +/- 1.8) cells alone. Histological and immunohistochemical staining of the newly repaired tissues produced after treatment with either mixed cells or hChon-TGF-beta1 cells alone showed hyaline cartilage- like characteristics. These results suggest that the implantation of mixed cells may be a clinically efficient method of regenerating hyaline articular cartilage.

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One of the most important factors in the production of cartilage is transforming growth factor beta1 (TGF-beta1). To obtain sustained release of TGF-beta1, a cell-mediated gene therapy technique was introduced. We infected chondrocytes with a retroviral vector carrying the TGF-beta1 gene. The single clone derivative showed sustained TGF-beta1 secretion. It also showed constitutive type II collagen expression. Whereas the TGF-beta1 protein itself is unable to induce formation of cartilage in vivo, human chondrocytes engineered to express a retroviral vector encoding TGF-beta1 showed cartilage formation in vivo when cells were injected into nude mice intradermally. These data suggest that cell-mediated gene therapy using TGF-beta1 as a transgene would be a promising treatment for osteoarthritis.

Genetically engineered chondrocytes virally transduced with a transforming growth factor (TGF)-β1 (TG-C [TissueGene-C]) expression vector have been shown to have potential benefits in the nonoperative management of knee osteoarthritis. Previous literature has reported on safe dosages of TG-C. Therefore, the purpose of this study was to evaluate the Phase II results and a 24-month efficacy of this injectable mixture compared with placebo in patients with Kellgren–Lawrence (K–L) grade III knee osteoarthritis. Specifically, we assessed (1) functional outcomes, (2) pain scores, (3) adverse events (AEs), and (4) magnetic resonance imaging (MRIs) findings. We performed a multicenter, double-blinded, placebo-controlled, and randomized study of adults who had K–L grade III knee osteoarthritis. A total of 102 patients were 2:1 randomized to TG-C at a dose of 3.0 × 107 cells, or placebo injections between May 1, 2011 and October 31, 2012. Outcomes analyzed were knee joint function, pain, quality of life, adverse events, and MRI findings using the whole-organ magnetic resonance imaging score (WORMS) system. There were significant improvements in the International Knee Documentation Committee (IKDC) and visual analogue scale (VAS) scores in the TG-C cohort, when compared with the placebo cohort at weeks 12, 52, 72, and 104 (p < 0.05). No severe AEs were observed. Common AEs were arthralgia, joint inflammation, and joint effusion which were similar between both cohorts. Whole-knee MRIs at 12 months showed less progression of cartilage damage, infrapatellar fat pad-synovitis, and effusion-synovitis in the TG-C cohort. Patients who received TG-C had significant improvements in IKDC and VAS scores. These patients also reported less severe and frequent pain. Additionally, fewer patients treated with TG-C showed progression of cartilage damage, as well as less progression of infrapatellar fat pad synovitis and effusion-synovitis. Furthermore, treatment with TG-C was generally well tolerated with minor AEs. Therefore, based on these results, TG-C appears to be a safe and effective modality for the management of K–L grade III osteoarthritis.

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