Cellular uptake of chemically modified mRNA occurs via caveolae-mediated endocytosis, yielding high levels of protein expression in slow-dividing cells

Cellular internalization of the complexes was assessed by using chemical inhibitors of endocytic pathways. Correlative light and electron microscopy were also used for this purpose. While lipoplexes utilized several entry routes, uptake via caveolae served as the main route for gene delivery. pDNA yielded higher expression levels in fast-dividing fibroblasts, whereas, in slow-dividing osteoblasts, cmRNA was responsible for high protein production.

In the case of mesenchymal stem cells, which presented an intermediate doubling time, the combination vector/nucleic acid seemed more relevant than the nucleic acid per se. In all cases, protein expression was higher when the cells were seeded on 3D scaffolds.