Development of engineered cells for implantation in gene therapy

Gene therapy in pancreatic cancer

Pancreatic cancer (PC) is a highly lethal disease and notoriously difficult to treat. Only a small proportion of PC patients are eligible for surgical resection, whilst conventional chemoradiotherapy only has a modest effect with substantial toxicity. Gene therapy has become a new widely investigated therapeutic approach for PC. This article reviews the basic rationale, gene delivery methods, therapeutic targets and developments of laboratory research and clinical trials in gene therapy of PC by searching the literature published in English using the PubMed database and analyzing clinical trials registered on the Gene Therapy Clinical Trials Worldwide website (http://www. wiley.co.uk/genmed/ clinical). Viral vectors are main gene delivery tools in gene therapy of cancer, and especially, oncolytic virus shows brighter prospect due to its tumor-targeting property. Efficient therapeutic targets for gene therapy include tumor suppressor gene p53, mutant oncogene K-ras, anti-angiogenesis gene VEGFR, suicide gene HSK-TK, cytosine deaminase and cytochrome p450, multiple cytokine genes and so on. Combining different targets or combination strategies with traditional chemoradiotherapy may be a more effective approach to improve the efficacy of cancer gene therapy. Cancer gene therapy is not yet applied in clinical practice, but basic and clinical studies have demonstrated its safety and clinical benefits. Gene therapy will be a new and promising field for the treatment of PC.

Recent advances in the use of encapsulated cells for effective delivery of therapeutics

Cell encapsulation can be defined as a living cell approach for the long-term delivery of therapeutic products. It consists of the immobilization of therapeutically active cells within a general polymer matrix that permits the ingress of nutrients and oxygen and the egress of therapeutic protein products but impedes the immune contact of the enclosed cells. In recent decades many attempts have evaluated the potential of this technology to release therapeutic agents for the treatment of different pathologies and disorders. At present, cell encapsulation may be used as a technological platform to improve knowledge and clinical use of stem cells. This review describes the main issues related to this cell-based approach and summarizes some of the most interesting therapeutic applications.

Design and fabrication of 3D porous scaffolds to facilitate cell-based gene therapy

Biomaterials capable of efficient gene delivery by embedded cells provide a fundamental tool for the treatment of acquired or hereditary diseases. A major obstacle is maintaining adequate nutrient and oxygen diffusion to cells within the biomaterial. In this study, we combined the solid free-form fabrication and porogen leaching techniques to fabricate three-dimensional scaffolds, with bimodal pore size distribution, for cell-based gene delivery. The objective of this study was to design micro-/macroporous scaffolds to improve cell viability and drug delivery. Murine bone marrow-derived mesenchymal stromal cells (MSCs) genetically engineered to secrete erythropoietin (EPO) were seeded onto poly-L-lactide (PLLA) scaffolds with different microporosities. Over a period of 2 weeks in culture, an increase in cell proliferation and metabolic activity was observed with increasing scaffold microporosity. The concentration of EPO detected in supernatants also increased with increasing microporosity level. Our study shows that these constructs can promote cell viability and release of therapeutic proteins, and clearly demonstrates their capacity for a dual role as scaffolds for tissue regeneration and as delivery systems for soluble gene products.

Challenges and emerging technologies in the immunoisolation of cells and tissues

Protection of transplanted cells from the host immune system using immunoisolation technology will be important in realizing the full potential of cell-based therapeutics. Microencapsulation of cells and cell aggregates has been the most widely explored immunoisolation strategy, but widespread clinical application of this technology has been limited, in part, by inadequate transport of nutrients, deleterious innate inflammatory responses, and immune recognition of encapsulated cells via indirect antigen presentation pathways. To reduce mass transport limitations and decrease void volume, recent efforts have focused on developing conformal coatings of micron and submicron scale on individual cells or cell aggregates. Additionally, anti-inflammatory and immunomodulatory capabilities are being integrated into immunoisolation devices to generate bioactive barriers that locally modulate host responses to encapsulated cells. Continued exploration of emerging paradigms governed by the inherent challenges associated with immunoisolation will be critical to actualizing the clinical potential of cell-based therapeutics.

Comparing reagents for efficient transfection of human primary myoblasts: FuGENE 6, Effectene and ExGen 500

This study compared three different synthetic reagents (FuGENE 6, Effectene and ExGen 500) for the transfection of human primary myoblasts. We examined the efficiency, cytotoxicity and size of the complexes formed in the presence of different amounts of vector and DNA and with variable amounts of serum. Transfection rates were relatively high for primary cells, especially with FuGENE 6 (20%), which appeared to be the best transfection reagent for these cells, even in the presence of 10% serum. Cultured human myoblasts are an interesting tool for studying neuromuscular diseases and are potentially useful for myoblast transfer therapy studies. Moreover, the efficiency of these transfection reagents in a medium containing 10% serum is promising for possible gene therapy protocols for muscle diseases.

Cellular vehicles for cancer gene therapy: current status and future potential

Cancer is a difficult target for any therapeutic strategy; therefore, there is a continuous search for new therapeutic modalities, for application either alone or in combination. In this regard, gene-based therapy is a new approach that offers hope of improved control of tumors. Intensive research to apply gene therapy for cancer treatment has led to identification of the most important technical and theoretical barriers that need to be overcome for clinical success. One of the central unresolved challenges remains the issue of specific and efficient delivery of genes to target cells or tissues, emphasizing the importance of the gene carrier. Along with different viral and non-viral vector systems, mammalian cells have also been considered as vehicles for delivery of anti-cancer therapeutics. The cell-based delivery approach was introduced as the first attempt to apply gene therapy to cancer treatment, and in general, has followed most of the ups and downs of gene therapy applications, progressing alongside new knowledge gained in this field. As a result, significant progress has been made in some aspects of the cell-based approach, while the development of other essential issues is only just gaining speed. It appears that the initial phase of development of cell-based protocols - the achievement of efficient ex vivo cell loading with therapeutics - has largely been fulfilled. However, the desired efficacy of cell-based strategies in general has not yet been reached, and specificity of tumor homing needs to be improved considerably. There is hope that advances in related scientific fields will promote the utilization of cells as powerful and versatile vehicles for cancer gene therapy.

Biocompatible oligochitosans as cationic modifiers of alginate/Ca microcapsules

In the past, it has been proven that by properly adjusting the molecular mass of the oligochitosan samples, it is possible to optimize the formation of rigid, biocompatible capsules with semipermeable membranes under physiological conditions. In this study, the feasibility of four oligochitosan samples, with varying molar masses (M(n) in range 3-5 kDa), as biocompatible coatings of alginate/Ca capsules was investigated. By selection of appropriate depolymerization and purification methods we obtained oligochitosan samples that appeared to be noncytotoxic for C(2)C(12) myoblasts and did not influence the mammalian cell metabolism especially in relative short time during the process of capsule formation. Furthermore, oligochitosans can be used as a tool to reduce the membrane cut-off of the alginate capsules. However, such reduction, as well as mechanical resistance of formed microcapsules, depend on MM of the cationic polysaccharide and the chemical composition of the alginate (mannuronic/guluronic acid ratio). Here, we address that the use of low molar mass chitosan (< 5000 g/mol) permits the formation of mechanical stable capsules at physiological pH, which represents a strong advantage over other chitosan-based chemistries.

History, challenges and perspectives of cell microencapsulation

Cell microencapsulation continues to hold significant promise for biotechnology and medicine. The controlled, and continuous, delivery of therapeutic products to the host by immunoisolated cells is a potentially cost-effective method to treat a wide range of diseases. Although there are several issues that need to be addressed, including capsule manufacture, properties and performance, in the past few years, a stepwise analysis on the essential obstacles and limitations has brought the whole technology closer to a realistic proposal for clinical application. This paper summarizes the current situation in the cell encapsulation field and discusses the main events that have occurred along the way.

Cell microencapsulation technology for biomedical purposes: novel insights and challenges

The aim of cell microencapsulation technology is to treat multiple diseases in the absence of immunosuppression. Using this technique, cells are immobilized within carefully designed capsules that allow the long-term function of the graft. Although the potential impact of this field is likely to be wide-ranging, the past few years have seen several 'firsts' that have brought the whole technology much closer to a realistic clinical application.

Three-dimensional cell-scaffold constructs promote efficient gene transfection: implications for cell-based gene therapy

To date, introduction of gene-modified cells in vivo is still a critical limitation for cell-based gene therapy. In this study, based on tissue engineering techniques, we developed a three-dimensional (3-D) transfection system to be cell-based gene delivery vehicle. Human trophoblast-like ED(27) and fibroblastic NIH3T3 cells were used as model cell lines. Cells were seeded onto PET fibrous matrices and plated on polyethylene terephathalate (PET) films as 2-D transfection control. The cell-matrices and cell-films were transfected with pCMV-betagal and pEGFP (green fluorescent protein) reporter gene vectors using LipofectAmine reagent. Gene expression on 3-D versus 2-D growth surface were investigated. The effects of seeding method, seeding density, porosity of the PET matrix, and culturing time of the cell-matrix complex on cDNA transfection and expression in the 3-D cell-matrix complex were also investigated. The beta-gal assay and GFP detection showed that 3-D transfection promoted a higher gene expression level and longer expression time as compared to 2-D transfection. There existed an optimal initial cell seeding density for gene transfection of 3-D cell-matrix complex. Cells seeded on PET matrices with a lower porosity ( approximately 87%) had higher gene expression activities than cells in the matrices with a higher porosity ( approximately 90%). Also, Higher gene expression levels of beta-gal were obtained for the more uniformly seeded matrices that were seeded with a depth-filtration method. The results from this study demonstrate the potential utility of cells seeded onto 3-D fibrous matrices as cell-based gene delivery vehicle for in vitro study of gene expression or in vivo gene therapy.