Abstract
Protein delivery from genetically modified skeletal muscle has been reported previously. However, a stable and prolonged secretion was obtained in immunocompromised or newborn animals only. To evaluate the clinical relevance of this approach, we have transduced myoblasts from an adult β-glucuronidase-deficient (MPS VII) mouse with retroviral vectors carrying either the human β-glucuronidase cDNA or the murine erythropoietin (Epo) cDNA. The cells were then grafted into the tibialis anterior muscle of adult immunocompetent MPS VII recipients. Protein expression was controlled either by ubiquitous or muscle-specific transcriptional regulatory elements. Animals were analyzed over an 8-month period. The in situ detection of β-glucuronidase activity revealed up to 60% of genetically modified myofibers in the recipient muscles. The human desmin promoter and enhancer showed the highest in vivo expression. Secretion of β-glucuronidase induced a disappearance of lysosomal storage lesions in the liver and spleen of recipient animals. Delivery of Epo led to a permanent increase of hematocrit values over 3 months. These results showed that the transplantation of genetically modified myoblasts allowed a sustained secretion of recombinant proteins at therapeutic levels in immunocompetent adult mice. They suggest that the approach may be considered for human applications.
Overview summary
The goal of this study was to document the therapeutic relevance of protein delivery from genetically modified muscle in immunocompetent animals. We have introduced the human β-glucuronidase cDNA or the murine Epo cDNA into primary myoblasts from an adult β-glucuronidase-deficient (MPS VII) mouse. Following transplantation in non-immunosuppressed adult MPS VII recipients, we achieved a prolonged secretion of the recombinant proteins at therapeutic levels. These results suggest that the approach may be relevant for the treatment of patients.
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