Current Gene Therapy - Volume 9, Issue 4, 2009

Interleukin-12 (IL-12) is known for several years to have an essential role in inflammatory responses and innate resistance to infection and cancer. This has been largely attributed to its ability to initiate the differentiation of T-helper-1 (Th1) cells producing interferon-gamma. Recently, two new cytokines, IL-23 and IL-27, with homology to IL-12 were discovered and assigned to the IL-12 family of cytokines. Growing evidence supports a role for IL-23 as key mediator of autoimmune disease regulating the new Th17 subset of CD4+ T cells. IL-27 can have pro- and anti-inflammatory effects, which increase Th1 differentiation, suppress Th2 proliferation, or stimulate cytotoxic T cell activity. Several strategies have been pursued to apply the immunological effects of IL-12 family members to the treatment of human disease. Whereas the inhibition of IL-12 and IL-23 signal transduction has shown promising results for the treatment of autoimmune disease, the administration of IL-12 during infection and cancer can increase the host immune reaction. The increasing knowledge about the new IL-12 family members, IL-23 and IL-27, has revealed new therapeutic options for the use of these cytokines. In this review, we discuss therapeutic strategies using IL-12 family members in infection, autoimmunity, and cancer with special focus on gene administration.

The cellular and molecular events of periodontal healing are coordinated and regulated by an elaborate system of signaling molecules, pointing to a primary strategy for functional periodontal compartment regeneration to replicate components of the natural cellular microenvironment by providing an artificial extracellular matrix (ECM) and by delivering growth factors. However, even with optimal carriers, the localized delivery of growth factors often requires a large amount of protein to stimulate significant effects in vivo, which increases the risk and unwanted side effects. A simple and relatively new approach to bypassing this dilemma involves converting cells into protein producing factories. This is done by a so-called gene delivery method, where therapeutic agents to be delivered are DNA plasmids that include the gene encoding desired growth factors instead of recombinant proteins. As localized depots of genes, novel gene delivery systems have the potential to release their cargo in a sustained and controlled manner and finally provide time- and spacedependent levels of encoded proteins during all stages of tissue regrowth, offering great versatility in their application and prompting new tissue engineering strategy in periodontal regenerative medicine. However, gene therapy in Periodontology is clearly in its infancy. Significant efforts still need to be made in developing safe and effective delivery platforms and clarifying how gene delivery, in combination with tissue engineering, may mimic the critical aspects of natural biological processes occurring in periodontal development and repair. The aim of this review is to trace an outline of the state-of-the-art in the application of gene delivery and tissue engineering strategies for periodontal healing and regeneration.

To achieve therapeutic effects, gene transportation or gene transfection becomes the key technique of gene therapy. Since viral vectors for gene therapy have shown serious problems, including immunogenicity and other adverse effects, non-viral carriers have attracted a great deal of attention, despite the fact that the transfection efficiencies are lower than those by viral carriers. Therefore, the major challenge of gene delivery is to improve the transfection efficiencies of the non-viral carriers, and first of all, the cell penetration efficiencies. This review focuses on recent approaches in the development of new non-viral gene delivery vectors, with great respect to those constructed based on cell penetration pathways of intracellular process considering transfection efficiency and cell penetration efficiency. Further development of sophisticated delivery systems is prospected for the non-viral vectors application in gene therapy.

Primary immunodeficiencies (PID) are caused by mutations in genes that impair the development or activity of the immune system. Although bone marrow transplants achieve long time restoration in up to 90% of treated patients, morbidity and mortality are still high for some PID and adequate donors are not always available. Gene Therapy (GT) was envisioned as an alternative treatment for PID by inserting the correct gene into the patient's haematopoietic stem cells (HSCs). Up to date, GT for PID has succeeded in 40 of 44 patients treated in four clinical trials. However, five children enrolled in the SCID-X1 clinical trial developed leukaemia-like disease produced by aberrant expression of oncogenes. This phenomenon resulted fatal in one patient and represented a severe setback for gene therapy. Since then, vector development has been a priority in the GT field, by refining existing Murine laeukemia virus (MLV)-based vectors or by developing new ones. This review summarizes existing methodologies for PID GT highlighting the importance of animal models in the PID GT success and focusing on new gene transfer vectors to achieve safe, efficient and stable gene modification.

Interleukin (IL)-10 is a well known anti-inflammatory and immunoregulatory cytokine, mainly released by, and acting on cells of the immune system such as monocytes, macrophages, T cells, NK cells, and B cells. IL-10 is also produced by a few connective tissue cell types including chondrocytes and is involved in processes such as connective tissue extracellular matrix remodelling, although it's exact function in articular cartilage remains unclear. This review article summarizes after a short insight into functions of IL-10 in the immune system most of the published literature on the role of IL-10 in articular cartilage homeostasis and disorders. A critical analysis of the present literature was undertaken leading to a survey of the significance of IL-10 in rheumatoid arthritis (RA), osteoarthritis (OA) and blood induced cartilage damage with particular focus on the direct impact of IL-10 on chondrocyte biology. IL-10 is up-regulated in RA and OA and therapeutic effects of IL-10 in experimental arthritis using several gene therapeutic approaches were reported, mainly through an immune cell mediated immunosuppression mechanism. Recently, a direct anti-inflammatory, -catabolic and -apoptotic potential of IL-10 in cartilage was described, suggesting a chondroprotective effect of IL-10, not only in RA and OA, but also in non-RA and non-systemic cartilage disorders. Chondroprotection by IL-10 may be a promising tool in arthritis therapy, as IL-10 plays a role in joint and cartilage immunoregulation and homeostasis. However, a crucial problem remains to be the optimisation of local and continuous therapeutic effective levels of IL-10 administration in the joint.

In vivo electroporation-mediated gene therapy in large animals is gaining ground as one of the most important means for non-viral gene therapy. This review focuses on the novel aspects of reversible electroporation as applied to large animals, improvement of electroporation delivery technique, and development of electroporation-based vaccines. In regard to large animals, we have summarized the initial use of electroporation-mediated antineoplastic gene therapy in humans, vaccination in monkeys, reversing and preventing cachexia in dogs, and increasing growth rate and piglet survival in pigs. Novel techniques incorporating electroporation, including ex vivo manipulations, electron avalanche transfection, and electrosonoporation illustrate evolving modifications. Specific alterations of electroporation parameters and DNA formulations along with ideas of enhancing gene transfection efficiency are provided in addition to a discussion of some of the current limitations of electroporation-mediated gene therapy.