Project description:Abstract Background: Gene transfer by electroporation (electro gene transfer) to muscle results in high level long term transgenic expression, showing great promise for treatment of e.g. protein deficiency syndromes. However little is known about the effects of electro gene transfer on muscle fibres. We have therefore investigated transcriptional changes through gene expression profile analyses, as well as morphological changes evaluated by histological analysis. Electro gene transfer was obtained using a combination of a short high voltage pulse (HV, 1000 V/cm, 100 @s) followed by a long low voltage pulse (LV, 100 V/cm, 400 ms); a pulse combination optimised for efficient and safe gene transfer. Muscles were transfected with green fluorescent protein (GFP) and excised at 4 hours, 48 hours or 3 weeks after treatment. Results: Differentially expressed genes were investigated by microarray analysis, and descriptive statistics were performed to evaluate the effects of 1) electroporation, 2) DNA injection, and 3) time after treatment. The biological significance of the results was assessed by gene annotation and supervised cluster analysis. Generally, electroporation caused down-regulation of structural proteins e.g. sarcospan and catalytic en-zymes such as phosphoenolpuryvate carboxykinase. Injection of DNA induced down-regulation of intracellular transport proteins e.g. sentrin. The effects on muscle fibres were transient as the expression profiles 3 weeks after treatment were closely related with the control muscles. Most interestingly, no changes in the expression of proteins involved in inflammatory responses or muscle regeneration was detected, indicating limited muscle damage and regeneration. Histological analysis revealed structural changes with loss of cell integrity and striation pattern in some fibres after DNA+HV+LV treatment, while electroporation alone caused minor loss of striation pattern but preservation of cell integrity. Conclusion: The small and transient changes found in the gene expression profiles are of great importance, as this demonstrates that electro gene transfer is safe with minor effects on the muscle host cells. These findings are essential for introducing the electro gene transfer to muscle for clinical use. Indeed the HV+LV pulse combination used have been optimised to ensure highly efficient and safe electro gene transfer. Keywords: Electro gene transfer, microarray, affymetrix, gene therapy, skeletal muscle, mouse, time course

Project description:Abstract; Background: Gene transfer by electroporation (electro gene transfer) to muscle results in high level long term transgenic expression, showing great promise for treatment of e.g. protein deficiency syndromes. However little is known about the effects of electro gene transfer on muscle fibres. We have therefore investigated transcriptional changes through gene expression profile analyses, as well as morphological changes evaluated by histological analysis. Electro gene transfer was obtained using a combination of a short high voltage pulse (HV, 1000 V/cm, 100 @s) followed by a long low voltage pulse (LV, 100 V/cm, 400 ms); a pulse combination optimised for efficient and safe gene transfer. Muscles were transfected with green fluorescent protein (GFP) and excised at 4 hours, 48 hours or 3 weeks after treatment. Results: Differentially expressed genes were investigated by microarray analysis, and descriptive statistics were performed to evaluate the effects of 1) electroporation, 2) DNA injection, and 3) time after treatment. The biological significance of the results was assessed by gene annotation and supervised cluster analysis. Generally, electroporation caused down-regulation of structural proteins e.g. sarcospan and catalytic en-zymes such as phosphoenolpuryvate carboxykinase. Injection of DNA induced down-regulation of intracellular transport proteins e.g. sentrin. The effects on muscle fibres were transient as the expression profiles 3 weeks after treatment were closely related with the control muscles. Most interestingly, no changes in the expression of proteins involved in inflammatory responses or muscle regeneration was detected, indicating limited muscle damage and regeneration. Histological analysis revealed structural changes with loss of cell integrity and striation pattern in some fibres after DNA+HV+LV treatment, while electroporation alone caused minor loss of striation pattern but preservation of cell integrity. Conclusion: The small and transient changes found in the gene expression profiles are of great importance, as this demonstrates that electro gene transfer is safe with minor effects on the muscle host cells. These findings are essential for introducing the electro gene transfer to muscle for clinical use. Indeed the HV+LV pulse combination used have been optimised to ensure highly efficient and safe electro gene transfer. Experiment Overall Design: The mice did recieve to their tibialis cranialis muscle either No tretment/control (CTRL), Electroporation only (EP), Plasmid injection only (DNA) or Plasmid DNA and in vivo Electro gene transfer (EP+DNA). Experiment Overall Design: Four hrs, 48 hrs and 3 weeks after treatment the mice were euthanized and the expression profile of the treated muscles were analysed. Experiment Overall Design: The following number of mice were included: Experiment Overall Design: CTRL, 3 mice, Experiment Overall Design: EP at 4 hrs, 1 mouse, Experiment Overall Design: EP at 48 hrs, 1 mouse, Experiment Overall Design: EP at 3 weeks, 1 mouse, Experiment Overall Design: DNA at 4 hrs, 1 mouse, Experiment Overall Design: DNA at 48 hrs, 1 mouse, Experiment Overall Design: DNA at 3 weeks, 1 mouse, Experiment Overall Design: EP+DNA at 4 hrs, 2 mice, Experiment Overall Design: EP+DNA at 48 hrs, 1 mouse, Experiment Overall Design: EP+DNA at 3 weeks, 1 mouse. Experiment Overall Design: A total number of mice 13.

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