Currently, the most efficient and promising approach for generating large numbers of engraftable human skeletal myogenic progenitors from pluripotent stem cells requires the conditional in vitro overexpression of PAX7 using lentiviral vectors. Because a non-integrating approach would be preferable to eliminate or minimize the risk associated with random genomic integration, here we investigate whether transient expression of PAX7 using minicircle DNA would enable the generation of functional pluripotent stem cell-derived myogenic progenitors, equivalent to those generated by lentivirus. Our results demonstrate that upon multiple transfections, the minicircle approach allows for the scalable generation of myogenic progenitors and these undergo efficient terminal differentiation in vitro. However, transplantation of minicircle-generated myogenic progenitors resulted in limited engraftment. This is probably due to less efficient delivery and more transient PAX7 expression in these cultures since PAX7 downregulation is accompanied by high level of spontaneous differentiation. Thus, although the in vitro data shows that the minicircle approach could potentially replace the use of lentivirus, improvements in the transfection/expression system will be necessary before it will be a feasible strategy for the generation of myogenic progenitors for cell replacement therapy.
Bibliographical noteFunding Information:
This project was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Number R01 AR055299, the Parent Project Muscular Dystrophy (PPMD) (#00613), ADVault Inc., and MyDirectives.com (R.C.R.P.). The monoclonal antibody to MHC was obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the University of Iowa. We thank Cynthia Dekay for assistance in graphic design.
- Non-viral minicircle
- Skeletal myogenic progenitors