Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo

Background Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF-2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo. Methods Lapine articular chondrocytes overexpressing a lacZ or a human FGF-2 gene sequence were encapsulated in alginate and further characterized. The resulting lacZ or FGF-2 spheres were applied to cartilage defects in the knee joints of rabbits. In vivo, cartilage repair was assessed qualitatively and quantitatively at 3 and 14 weeks after implantation. Results In vitro, bioactive FGF-2 was secreted, leading to a significant increase in the cell numbers in FGF-2 spheres. In vivo, FGF-2 continued to be expressed for at least 3 weeks without leading to differences in FGF-2 concentrations in the synovial fluid between treatment groups. Histological analysis revealed no adverse pathologic effects on the synovial membrane at any time point. FGF-2 gene transfer enhanced type II collagen expression and individual parameters of chondrogenesis, such as the cell morphology and architecture of the new tissue. Overall articular cartilage repair was significantly improved at both time points in vivo. Conclusions The data suggest that localized overexpression of FGF-2 enhances the repair of cartilage defects via stimulation of chondrogenesis, without adverse effects on the synovial membrane. These results may lead to the development of safe gene-based therapies for human articular cartilage defects

Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo

Background Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF-2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo. Methods Lapine articular chondrocytes overexpressing a lacZ or a human FGF-2 gene sequence were encapsulated in alginate and further characterized. The resulting lacZ or FGF-2 spheres were applied to cartilage defects in the knee joints of rabbits. In vivo, cartilage repair was assessed qualitatively and quantitatively at 3 and 14 weeks after implantation. Results In vitro, bioactive FGF-2 was secreted, leading to a significant increase in the cell numbers in FGF-2 spheres. In vivo, FGF-2 continued to be expressed for at least 3 weeks without leading to differences in FGF-2 concentrations in the synovial fluid between treatment groups. Histological analysis revealed no adverse pathologic effects on the synovial membrane at any time point. FGF-2 gene transfer enhanced type II collagen expression and individual parameters of chondrogenesis, such as the cell morphology and architecture of the new tissue. Overall articular cartilage repair was significantly improved at both time points in vivo. Conclusions The data suggest that localized overexpression of FGF-2 enhances the repair of cartilage defects via stimulation of chondrogenesis, without adverse effects on the synovial membrane. These results may lead to the development of safe gene-based therapies for human articular cartilage defects

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

Practical guidelines for rigor and reproducibility in preclinical and clinical studies on cardioprotection

The potential for ischemic preconditioning to reduce infarct size was first recognized more than 30 years ago. Despite extension of the concept to ischemic postconditioning and remote ischemic conditioning and literally thousands of experimental studies in various species and models which identified a multitude of signaling steps, so far there is only a single and very recent study, which has unequivocally translated cardioprotection to improved clinical outcome as the primary endpoint in patients. Many potential reasons for this disappointing lack of clinical translation of cardioprotection have been proposed, including lack of rigor and reproducibility in preclinical studies, and poor design and conduct of clinical trials. There is, however, universal agreement that robust preclinical data are a mandatory prerequisite to initiate a meaningful clinical trial. In this context, it is disconcerting that the CAESAR consortium (Consortium for preclinicAl assESsment of cARdioprotective therapies) in a highly standardized multi-center approach of preclinical studies identified only ischemic preconditioning, but not nitrite or sildenafil, when given as adjunct to reperfusion, to reduce infarct size. However, ischemic preconditioning—due to its very nature—can only be used in elective interventions, and not in acute myocardial infarction. Therefore, better strategies to identify robust and reproducible strategies of cardioprotection, which can subsequently be tested in clinical trials must be developed. We refer to the recent guidelines for experimental models of myocardial ischemia and infarction, and aim to provide now practical guidelines to ensure rigor and reproducibility in preclinical and clinical studies on cardioprotection. In line with the above guideline, we define rigor as standardized state-of-the-art design, conduct and reporting of a study, which is then a prerequisite for reproducibility, i.e. replication of results by another laboratory when performing exactly the same experiment

Flexibilisation in the German system of wage bargaining: extent, determinants, impacts

Given the recent financial crisis, the German labour market performs relatively well. This has not been the case until recent years: collective bargaining and the rigid system of wage setting have been often cited as one of the reasons for Germany's high structural unemployment. Contrary, a reform process has started at least since the mid-1990s, introducing measures of flexibility and decentralization to the formally rigid system of wage setting. This article summarises the developments of possible and actual flexibilisation of collective bargaining contracts via so called hardship or opening clauses. A literature review sums up the scientific progress that had been made at the beginning of the research project and shows which gaps were to fill. Lacking data, the first parts of the project investigate on the actual existence and shape of opening clauses and create a new data set to measure the incidence of opening clauses in collective bargaining agreements in West German manufacturing sector for the years 1995 to 2007, the IAW data set on opening clauses. Using this, we analyse the determinants of the introduction of opening clauses on the industry level and of their actual implementation on the firm level. The latter parts of the project focus on the relation between opening clauses and measures of firm performance, especially considering wages and job growth. The results show that opening clauses are more and more common and that a more diversified wage structure and higher job growth is observed

Dysregulation of Rho GTPases in the αPix/Arhgef6 mouse model of X-linked intellectual disability is paralleled by impaired structural and synaptic plasticity and cognitive deficits

Mutations in the ARHGEF6 gene, encoding the guanine nucleotide exchange factor αPIX/Cool-2 for the Rho GTPases Rac1 and Cdc42, cause X-linked intellectual disability (ID) in humans. We show here that αPix/Arhgef6 is primarily expressed in neuropil regions of the hippocampus. To study the role of αPix/Arhgef6 in neuronal development and plasticity and gain insight into the pathogenic mechanisms underlying ID, we generated αPix/Arhgef6-deficient mice. Gross brain structure in these mice appeared to be normal; however, analysis of Golgi-Cox-stained pyramidal neurons revealed an increase in both dendritic length and spine density in the hippocampus, accompanied by an overall loss in spine synapses. Early-phase long-term potentiation was reduced and long-term depression was increased in the CA1 hippocampal area of αPix/Arhgef6-deficient animals. Knockout animals exhibited impaired spatial and complex learning and less behavioral control in mildly stressful situations, suggesting that this model mimics the human ID phenotype. The structural and electrophysiological alterations in the hippocampus were accompanied by a significant reduction in active Rac1 and Cdc42, but not RhoA. In conclusion, we suggest that imbalance in activity of different Rho GTPases may underlie altered neuronal connectivity and impaired synaptic function and cognition in αPix/Arhgef6 knockout mice