Patients afflicted with severe laminin 5-deficient junctional epidermolysis bullosa (JEB) often die in infancy with massive cutaneous blistering. Prior approaches to genetically correct this disorder have relied on stable integration of wild-type LAMB3 sequences, using retroviral vectors. To develop a nonviral approach to JEB gene therapy, we used the phiC31 integrase, which mediates unidirectional genomic integration of plasmids containing a specific attB site. An attB-containing laminin 5 beta3 expression plasmid was integrated into the genomes of primary keratinocytes from four unrelated, genetically characterized JEB patients. phiC31 integrase supported genomic integration into epidermal progenitor cells. Regeneration of human skin on immunedeficient mice, using these cells, produced human skin tissue with restored laminin 5 expression. Furthermore, corrected JEB tissue restored hemidesmosome formation and abolished histologic evidence of subepidermal blistering. These findings provide an approach to durable nonviral correction of JEB.
"PhiC31 integrase has also been shown to promote a safer, site-specific integration in mammalian cells using pseudo attP sites endogenous to the mammalian genome  . Recent studies have shown that the phiC31 integrase can be successfully included in gene therapy strategies promoting integration and prolonged expression in vivo in mouse lungs , mouse liver , rat retina  and human skin  . "
[Show abstract][Hide abstract] ABSTRACT: Gene transfer efficiency and expression stability are key factors to a successful gene therapy approach. In the present work we have developed a combined system for gene transfer that integrates well established non-viral polymeric vectors based on chitosan particles with the properties of phiC31-integrase that promotes a relatively non-immunogenic, site-specific integration, with sustained gene expression. Simultaneously, to overcome one of the major limitations in adeno-associated virus mediated gene transfer – the delivery of large genes – we have tested the capacity of our non-viral vectors to incorporate a large (8 Kb) transgene. Polyplexes were extensively characterized for their size, surface charge, morphology, pDNA complexation, transfection efficiency and transgene expression in vitro using HEK293 cells. Co-transfection with integrase was done by complexation in a single polyplex preparation or the use of two separate polyplex preparations. Transgene expression, GFP and CEP290 (1 Kb and 8 Kb, respectively), was evaluated by fluorescence microscopy, flow cytometry and Western blot analysis. DNA complexation efficiency, particle size and morphology were consistent with gene delivery for all formulations. In contrast, transfection efficiency and transgene expression varied with polymer and polyplex size. Following delivery by chitosan polyplexes, high levels of GFP expression were still visible 16 weeks post-transfection and over-expression of the large transgene was detected at least 6 weeks post-transfection. Polyplexes incorporating phiC1 integrase demonstrate prolonged gene expression of both small (GFP, 1 Kb) and large genes (CEP290, 8 Kb). This approach, using a combined strategy of polymers and integrase may overcome the size limitation found in commonly used adeno-associated virus mediated gene transfer techniques, while maintaining a high safety profile and prolonged, sustained gene expression, thus constituting an alternative for gene delivery.
"The frequency of PhiC31-mediated integration is about 10-to 100-fold higher when compared to the reversible recombinases (Cre and FLP) both of which require that the target recognition sequence be preinserted into the genome . The utility of the φC31 system for mediating stable gene expression has been demonstrated in various cultured mammalian cell lines , and in primary cells, including mouse liver  , human skin cells , and muscle-derived stem cells  as well as for site-specific genomic insertion in mouse  and human ES cells . Here, we directly tested these two non-viral integrating vector systems for the capacity to mediate stable gene transfer into primitive adult stem cells. "
[Show abstract][Hide abstract] ABSTRACT: Non-viral integrating systems, PhiC31 phage integrase (ϕC31), and Sleeping Beauty transposase (SB), provide an effective method for ex vivo gene delivery into cells. Here, we used a plasmid-encoding GFP and neomycin phosphotransferase along with recognition sequences for both ϕC31 and SB integrating systems to demonstrate that both systems effectively mediated integration in cultured human fibroblasts and in rat multipotent adult progenitor cells (rMAPC). Southern blot analysis of G418-resistant rMAPC clones showed a 2-fold higher number of SB-mediated insertions per clone compared to ϕC31. Sequence identification of chromosomal junction sites indicated a random profile for SB-mediated integrants and a more restricted profile for ϕC31 integrants. Transgenic rMAPC generated with both systems maintained their ability to differentiate into liver and endothelium albeit with marked attenuation of GFP expression. We conclude that both SB and ϕC31 are effective non-viral integrating systems for genetic engineering of MAPC in basic studies of stem cell biology.
[Show abstract][Hide abstract] ABSTRACT: To master tissue and organ morphogenesis necessitates a thorough understanding of the cellular and molecular events involved in development, renewal, repair and regeneration. Skin reconstruction is the paradigm of tissue engineering. The transplantation of autologous adult epidermal stem cells is a life-saving procedure as it regenerates the indispensable barrier function of the skin, but the reconstruction of fully functional skin has been hampered by the complexity of the process. The recent identification of multipotent epithelial stem cells in adult hair follicles and of multipotent stem cells in dermis raises new hopes.
Current Opinion in Biotechnology 11/2003; 14(5):520-5. DOI:10.1016/j.copbio.2003.09.005 · 7.12 Impact Factor
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