Control and Augmentation of Long-Term Plasmid Transgene ExpressionIn Vivoin Murine Muscle Tissue andEx Vivoin Patient Mesenchymal Tissue

Abstract

Purpose. In vivogene therapy directed at tissues of mesenchymal origin could potentially augment healing. We aimed to assess the duration and magnitude of transene expressionin vivoin mice andex vivoin human tissues.Methods.Using bioluminescence imaging, plasmid and adenoviral vector-based transgene expression in murine quadricepsin vivowas examined. Temporal control was assessed using a doxycycline-inducible system. Anex vivomodel was developed and optimised using murine tissue, and applied inex vivohuman tissue.Results. In vivoplasmid-based transgene expression did not silence in murine muscle, unlike in liver. Although maximum luciferase expression was higher in muscle with adenoviral delivery compared with plasmid, expression reduced over time. The inducible promoter cassette successfully regulated gene expression with maximum levels a factor of 11 greater than baseline. Expression was re-induced to a similar level on a temporal basis. Luciferase expression was readily detectedex vivoin human muscle and tendon.Conclusions.Plasmid constructs resulted in long-termin vivogene expression in skeletal muscle, in a controllable fashion utilising an inducible promoter in combination with oral agents. Successful plasmid gene transfection in humanex vivomesenchymal tissue was demonstrated for the first time.