Abstract: The neuronal differentiation of mesenchymal stem cells offers a new strategy for the treatment of neurological disorders. Thus, there is a need to identify a noninvasive and sensitive in vivo imaging approach for real-time monitoring of transplanted stem cells. Our previous study confirmed that magnetic resonance imaging, with a focus on the ferritin heavy chain 1 reporter gene, could track the proliferation and differentiation of bone marrow mesenchymal stem cells that had been transduced with lentivirus carrying the ferritin heavy chain 1 reporter gene. However, we could not determine whether or when bone marrow mesenchymal stem cells had undergone neuronal differentiation based on changes in the magnetic resonance imaging signal. To solve this problem, we identified a neuron-specific enolase that can be differentially expressed before and after neuronal differentiation in stem cells. In this study, we successfully constructed a lentivirus carrying the neuron-specific enolase promoter and expressing the ferritin heavy chain 1 reporter gene; we used this lentivirus to transduce bone marrow mesenchymal stem cells. Cellular and animal studies showed that the neuron-specific enolase promoter effectively drove the expression of ferritin heavy chain 1 after neuronal differentiation of bone marrow mesenchymal stem cells; this led to intracellular accumulation of iron and corresponding changes in the magnetic resonance imaging signal. In summary, we established an innovative magnetic resonance imaging approach focused on the induction of reporter gene expression by a neuron-specific promoter. This imaging method can be used to noninvasively and sensitively detect neuronal differentiation in stem cells, which may be useful in stem cell-based therapies.

Key words: ferric ammonium citrate, ferritin heavy chain 1 gene, magnetic resonance imaging, mesenchymal stem cells, molecular imaging, neuronal differentiation, neuron-like cells, neurons, neuron-specific enolase, promoter