Background: We have previously shown that intramuscular injection of plasmid DNA formulated with a non-ionic amphiphile synthetic vector [poly(ethylene oxide)(13)-poly(propylene oxide)(30)-poly(ethylene oxide)(13) block copolymer; PE6400] increases reporter gene expression compared with naked DNA. We have now investigated this simple non-viral formulation for production of secreted proteins from the mouse skeletal muscle.
Methods: Plasmids encoding either constitutive human secreted alkaline phosphatase or murine erythropoietin inducible via a Tet-on system were formulated with PE6400 and intramuscularly injected into the mouse tibial anterior muscle.
Results: PE6400/DNA formulation led to an increased amount of recombinant alkaline phosphatase secreted from skeletal muscle as compared with naked DNA. In the presence of doxycycline, a single injection of 10 microg plasmid encoding inducible murine erythropoietin formulated with PE6400 significantly increased the hematocrit, whereas the same amount of DNA in the absence of PE6400 had no effect. The increase in the hematocrit was stable for 42 days. The tetracycline-inducible promoter permitted pharmacological control of hematocrit level after DNA intramuscular injection. However, 4 months post-injection the hematocrit returned to its pre-injection value, even in the presence of doxycycline. This phenomenon was likely caused by an immune response against the tetracycline-activated transcription factor.
Conclusions: Intramuscular injection of plasmid DNA formulated with PE6400 provides an efficient and simple method for secretion and production of non-muscle proteins.