Skeletal muscle than the CMV promoter [20]. Therefore, in our studies, accumulation of hPLAP to toxic levels would occur more slowly in muscles transduced with CK6-hPLAP constructs, compared with in muscles receiving CMV-hPLAP constructs. To determine whether an alternative choice of reporter gene might achieve more practical transduction of mammalianmusculature without inflammation, we administered rAAV6:CMV-GFP vectors to the muscles of mice. In contrast to results obtained following administration of rAAV6:CMV-hPLAP, we observed that transduction of muscles with an equivalent 16109 vg dose of rAAV6:CMV-GFP elicited widespread transgene expression without evidence of cellular purchase Hypericin degeneration or inflammatory response. However increasing the dose of rAAV6:CMV-GFP injected to 161010 vg subsequently resulted in muscle damage, macrophage recruitment and inflammatory signaling Asiaticoside A web pathway activation. Our data indicate that GFP should be preferred over hPLAP as a reporter gene to express in murine skeletal muscle, but consideration should still be given to the dose of vector employed and the ensuing level of transgene expression caused. In some instances where administration of higher vector doses is warranted, we suggest that it is preferable to employ a gene-deleted vector as an experimental control, as this configuration does not appear to cause the cellular degeneration and inflammation observed following transduction of limb muscles with higher doses of vectors carrying the aforementioned reporter genes. In summary, our studies highlight the potential deleterious effects of commonly used reporter genes when expressed in mammalian skeletal muscle. Both hPLAP and GFP have the ability to induce robust macrophage recruitment and inflammatory pathway activation in murine muscles, and the effects appear to be related to the level of transgene expression, rather than the vector particle load. Importantly, the potential to cause degeneration and inflammation of transduced muscles also appears to vary between reporter genes. Therefore, it is conceivable that other reporter genes (for instance alkaline phosphatase variants [36,37], other fluorescent proteins, and luciferase constructs) may have the capacity to cause similar deleterious effects in skeletal muscles if expressed at sufficiently high levels. These findings provide important insight into the potential adverse effects of expressing commonly used reporter genes in mammalian skeletal muscle, and highlight the importance of defining their potential impact upon transduced tissues before being used as experimental controls for in vivo studies.AcknowledgmentsThe authors wish to thank Dr. S.D. Hauschka, for the CK6 promoter construct and feedback on manuscript preparation, Dr. J.S. Chamberlain for the pAAV:CMV-hPLAP pAAV:CMV-GFP constructs, HEK293 cells and feedback on manuscript preparation, Dr D.W. Russell for the pDGM6 construct, Dr. J.M. Allen for advice with vector production (all investigators from The University of Washington). The authors also thank Dr. G.I. Lancaster and Professor M.A. Febbraio (Div. Metabolism, Baker IDI Heart and Diabetes Institute) for providing access to their supply of FAM labeled probes/primers for EMR1, ITGAX, TNFa and IL-1b.Author ContributionsConceived and designed the experiments: CEW PG. Performed the experiments: CEW CB HQ. Analyzed the data: CEW CB HQ PG. Wrote the paper: CEW PG. Obtained permission for use of plasmids and cell lines and other reagents: PG.
Pr.Skeletal muscle than the CMV promoter [20]. Therefore, in our studies, accumulation of hPLAP to toxic levels would occur more slowly in muscles transduced with CK6-hPLAP constructs, compared with in muscles receiving CMV-hPLAP constructs. To determine whether an alternative choice of reporter gene might achieve more practical transduction of mammalianmusculature without inflammation, we administered rAAV6:CMV-GFP vectors to the muscles of mice. In contrast to results obtained following administration of rAAV6:CMV-hPLAP, we observed that transduction of muscles with an equivalent 16109 vg dose of rAAV6:CMV-GFP elicited widespread transgene expression without evidence of cellular degeneration or inflammatory response. However increasing the dose of rAAV6:CMV-GFP injected to 161010 vg subsequently resulted in muscle damage, macrophage recruitment and inflammatory signaling pathway activation. Our data indicate that GFP should be preferred over hPLAP as a reporter gene to express in murine skeletal muscle, but consideration should still be given to the dose of vector employed and the ensuing level of transgene expression caused. In some instances where administration of higher vector doses is warranted, we suggest that it is preferable to employ a gene-deleted vector as an experimental control, as this configuration does not appear to cause the cellular degeneration and inflammation observed following transduction of limb muscles with higher doses of vectors carrying the aforementioned reporter genes. In summary, our studies highlight the potential deleterious effects of commonly used reporter genes when expressed in mammalian skeletal muscle. Both hPLAP and GFP have the ability to induce robust macrophage recruitment and inflammatory pathway activation in murine muscles, and the effects appear to be related to the level of transgene expression, rather than the vector particle load. Importantly, the potential to cause degeneration and inflammation of transduced muscles also appears to vary between reporter genes. Therefore, it is conceivable that other reporter genes (for instance alkaline phosphatase variants [36,37], other fluorescent proteins, and luciferase constructs) may have the capacity to cause similar deleterious effects in skeletal muscles if expressed at sufficiently high levels. These findings provide important insight into the potential adverse effects of expressing commonly used reporter genes in mammalian skeletal muscle, and highlight the importance of defining their potential impact upon transduced tissues before being used as experimental controls for in vivo studies.AcknowledgmentsThe authors wish to thank Dr. S.D. Hauschka, for the CK6 promoter construct and feedback on manuscript preparation, Dr. J.S. Chamberlain for the pAAV:CMV-hPLAP pAAV:CMV-GFP constructs, HEK293 cells and feedback on manuscript preparation, Dr D.W. Russell for the pDGM6 construct, Dr. J.M. Allen for advice with vector production (all investigators from The University of Washington). The authors also thank Dr. G.I. Lancaster and Professor M.A. Febbraio (Div. Metabolism, Baker IDI Heart and Diabetes Institute) for providing access to their supply of FAM labeled probes/primers for EMR1, ITGAX, TNFa and IL-1b.Author ContributionsConceived and designed the experiments: CEW PG. Performed the experiments: CEW CB HQ. Analyzed the data: CEW CB HQ PG. Wrote the paper: CEW PG. Obtained permission for use of plasmids and cell lines and other reagents: PG.
Pr.
