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Gene therapy makes islets from liver, treats diabetes

State-Of-The-Art Human Gene Therapy: Part I. Gene Delivery Technologies

Abstract: Safe and effective gene delivery is a prerequisite for successful gene therapy. In the early age of human gene therapy, setbacks due to problematic gene delivery vehicles plagued the exciting therapeutic outcome. However, gene delivery technologies rapidly evolved ever since. With the advancement of gene delivery techniques, gene therapy clinical trials surged during the past decade. As the first gene therapy product (Glybera) has obtained regulatory approval and reached clinic, human gene therapy finally realized the promise that genes can be medicines. The diverse gene delivery techniques available today have laid the foundation for gene therapy applications in treating a wide range of human diseases. Some of the most urgent unmet medical needs, such as cancer and pandemic infectious diseases, have been tackled by gene therapy strategies with promising results. Furthermore, combining gene transfer with other breakthroughs in biomedical research and novel biotechnologies opened new avenues for gene therapy. Such innovative therapeutic strategies are unthinkable until now, and are expected to be revolutionary. In part I of this review, we introduced recent development of non-viral and viral gene delivery technology platforms. As cell-based gene therapy blossomed, we also summarized the diverse types of cells and vectors employed in ex vivo gene transfer. Finally, challenges in current gene delivery technologies for human use were discussed. ... Read more

Development of Gene Therapy for Neurological Disorders

Abstract: Given improvements in viral vector design, production and efficiency of transduction in the central nervous system (CNS), as well as increased knowledge of neuropathological mechanisms in neurological disorders, success in treating a CNS disorder with gene transfer seems inevitable. Several different vector systems have been studied extensively and the adeno-associated viral vector system has been utilized in most early stage clinical trials in neurological disorders. Other vector systems, such as lentivirus, adenovirus, and herpes simplex virus are also viable vector platforms that should fill significant clinical niches based on their specific characteristics. In addition to the choice of the appropriate vector, the proper choice of transgene for the appropriate strategy to treat a neurological disorder is also critical. The example of glial cell line-derived neurotrophic factor ligands to treat Parkinson's disease is used to illustrate the importance of the interface between interpretation of pre-clinical data and consideration of the natural history of the disorder. This interface dictates the proper design of clinical trials that are capable of testing whether the treatment is actually successful. ... Read more

Viral delivery vectors for small interfering RNA

Since it was reported last year that double stranded RNA (dsRNA) could silence the expression of a specific gene by digesting the mRNA (1), it has been further revealed that small interfering RNA (siRNA) mediated RNA interference (RNAi) is a process conserved among plants, invertebrates, and vertebrates. RNAi has become a powerful tool for genetic analysis and gene silencing. In order to apply RNAi to mammalian systems, transfection of either synthetic oligonucleotides or plasmids has been a popular methodology. However, the technique is limited to specific cell lines and is nearly impossible in primary cells. Due to their small size ... Read more

Adenoviral vector and tumor specific replication

The application of adenoviral (Ad) vectors for cancer gene therapy moved one step forward in lieu of recent advances in related fields. These include the observation that several human tumor cell lines support the DNA replication in AdE1-, a deficient adenovirus with E1A and E1B deletions (1), and the development of an Ad E1-based vector that employs homologous recombination between inverted repeats to activate target genes (2).

Based on the above observation and development, Dr. Lieber and colleagues developed a new Ad vector. In this vector, the alkaline phosphatase (Ap) and E1A genes were cloned downstream of RSV (Rous sarcoma virus) ... Read more

Islet-derived progenitor cell transplantation helps diabetes patients

A team led by Dr. Edmond A. Ryan of the University of Alberta, Admonton, Alberta, Canada reported in Diabetes this month (51:2148-2157, Jul. 2002) the results of a small clinical trial of treatment of autoimmune type 1 diabetes by islet cell transplantation.

Seventeen patients who received the transplantation were followed up for an average of 20 months. Of the 15 patients who have been followed for at least one year, 9 (60%) no longer need to take insulin. Of the 6 patients who have been followed for at least 2 years, 4 (67%) are off insulin. The transplantations are of an ... Read more

Viral Expression Cassette Elements to Enhance Transgene Target Specificity and Expression in Gene Therapy

Abstract: Over the last five years, the number of clinical trials involving AAV (adeno-associated virus) and lentiviral vectors continue to increase by about 150 trials each year. For continued success, AAV and lentiviral expression cassettes need to be designed to meet each disease's specific needs. This review discusses how viral vector expression cassettes can be engineered with elements to enhance target specificity and increase transgene expression. The key differences relating to target specificity between ubiquitous and tissue-specific promoters are discussed, as well as how endogenous miRNAs and their target sequences have been used to restrict transgene expression. Specifically, relevant studies indicating how cis-acting elements such as introns, WPRE, polyadenylation signals, and the CMV enhancer are highlighted to show their utility for enhancing transgene expression in gene therapy applications. All discussion bears in mind that expression cassettes have space constraints. In conclusion, this review can serve as a menu of vector genome design elements and their cost in terms of space to thoughtfully engineer viral vectors for gene therapy. ... Read more

Enterovirus Persistence as a Mechanism in the Pathogenesis of Type 1 Diabetes

Abstract: Beyond acute clinical conditions, the role of enteroviruses (EVs) in chronic human diseases has been described. Although they are considered as highly cytolytic viruses, EVs can persist in various tissues. The persistence is believed to play a major role in the pathogenesis of EV related chronic diseases such as type 1 diabetes (T1D). T1D is characterized by an autoimmune destruction of pancreatic beta cells, and results from interplay between a genetic predisposition, the immune system, and environmental factors. EVs and especially group B coxsackieviruses (CVB) have been the most incriminated as exogenous agents involved in the development of T1D. Enteroviral persistence is the result of a virus-host coevolution combining a cell resistance to lysis through mutations or down-regulation of viral receptor, and a decrease of the viral replication by genomic modifications or the production of a stable double-stranded RNA form. CVB can persist in pancreatic cells and therefore could trigger, in genetically predisposed individuals, the autoimmune destruction of beta cells mainly through an activation of inflammation. The persistence of the virus in other tissues such as intestine, blood cells, and thymus has been described, and could also contribute to some extent to the enteroviral pathogenesis of T1D. The molecular and cellular mechanisms of CVB persistence and the link with the development of T1D should be investigated further. ... Read more

Novel Methods of Type 1 Diabetes Treatment

Abstract: Type 1 diabetes is an autoimmune disease characterized by the cell-mediated destruction of insulin-producing β-cells, leading to impaired glucose homeostasis, insulin insufficiency, and other complications. Although classic genetic studies have linked numerous genes to the susceptibility of developing diabetes, the mechanisms by which they influence the disease course remain poorly understood. Epigenetics, inheritable changes in gene expression that occur without accompanying genetic mutation, can both serve as a link between the environment and genetic causes of disease and help explain some of the observed vagaries of diabetes. Elucidation of the epigenetic landscape as it relates to putative treatment modalities is highly warranted. Drugs with histone deacetylase activity are in clinical trials for cancer and certain inflammatory diseases with high safety profiles and they hold similar promise for amelioration of type 1 diabetes with diminished secondary complications. Full-fledged studies on the epigenetics of type 1 diabetes are highly likely to provide novel tools for the manipulation of the disease in the years to come. In this review, epigenetic regulation mediated by small molecular inhibitors of histone deacetylases and their potential for preventing diabetes are discussed. Insights into the nature of the genetic mechanisms unraveled by these studies are also highlighted. ... Read more

Mesenchymal Stem Cell-Based Therapy for Type 1 Diabetes

Abstract: Diabetes has increasingly become a worldwide health problem, causing huge burden on healthcare system and economy. Type 1 diabetes (T1D), traditionally termed "juvenile diabetes" because of an early onset age, is affecting 5~10% of total diabetic population. Insulin injection, the predominant treatment for T1D, is effective to ameliorate the hyperglycemia but incompetent to relieve the autoimmunity and to regenerate lost islets. Islet transplantation, an experimental treatment for T1D, also suffers from limited supply of human islets and poor immunosuppression. The recent progress in regenerative medicine, especially stem cell therapy, has suggested several novel and potential cures for T1D. Mesenchymal stem cell (MSC) based cell therapy is among one of them. MSCs are a type of adult stem cells residing in bone marrow, adipose tissue, umbilical cord blood, and many other tissues. MSCs, with self-renewal potential and transdifferentiation capability, can be expanded in vitro and directed to various cell lineages with relatively less efforts. MSCs have well-characterized hypoimmunogenicity and immunomodulatory effect. All these features make MSCs attractive for treating T1D. Here, we review the properties of MSCs and some of the recent progress using MSCs as a new therapeutic in the treatment of T1D. We also discuss the strength and limitations of using MSC therapy in human trials. ... Read more

Innovative Approaches for Enhancing Cancer Gene Therapy

Abstract: Gene therapy provides a novel platform for therapeutic intervention of several genetic and non-genetic disorders. With the recent developments in the field, a wide variety of viral and non-viral vectors have emerged that can deliver genetic payloads to target cells. However, non-targeted delivery of transgenes often results in undesirable effects, low tumor transduction, and reduced therapeutic index. In this review, we focus on some of the novel approaches that can be used to meet the present challenges in the field and translate the potential of cancer gene therapy from 'bench to bedside' in the near future. ... Read more

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