cAMP induces neuronal differentiation of mesenchymal stem cells via activation of extracellular signal-regulated kinase/MAPK.

Mesenchymal stem cells are able to trans-differentiate into nonmesodermal lineage cells. Here, we identified downstream signaling molecules required for acquisition of neuron-like traits by mesenchymal stem cells following the elevation of intracellular cAMP levels. We found that forskolin induced neuron-like morphology and expression of neuron-specific enolase and neurofilament-200 in mesenchymal stem cells. Forskolin sequentially activated protein kinase A and B-regulation of alpha-fetoprotein (Raf), which led to phosphorylation of extracellular signal-regulated kinase. Importantly, blockade of extracellular signal-regulated kinase phosphorylation with a mitogen-activated protein kinase (MAPK) kinase inhibitor abrogated the forskolin-induced morphological changes and induction of neuronal proteins. These results indicate that extracellular signal-regulated kinase/MAPK mediates both cAMP-induced early cytoskeletal rearrangement and the later induction of neuronal markers in mesenchymal stem cells.