An Interdisciplinary Approach and Characterization of Neuronal Cells Transdifferentiated from Human Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are mesoderm-derived cells, primarily resident in adult bone marrow (BM). MSCs exhibit lineage differentiation to generate cells such as BM stroma, fat, and cartilage. Recent studies have reported the transdifferentiation of MSCs to cells of ectodermal and endodermal origin. Previously, we have reported transdifferentiation of human (h) MSCs into neuronal cells using retinoic acid (RA) as a differentiating agent. This study presents a more efficient induction method and rigorously characterizes the development using molecular, cellular, and functional approaches. A cocktail of induction agents containing basic fibroblast growth factor (bFGF) and RA generated cells that expressed glial and neuronal progenitor markers (GFAP) at day 2 post-induction. By day 12, 90% of hMSCs differentiated into cells that expressed markers consistent for neurons, including transcription factors linked to the development of differentiated neurons. Furthermore, cell proliferation studies and western blots for cell cycle-specific proteins demonstrated day-12 induced cells to be post-mitotic cells with no evidence of cell death. The cells exhibited spontaneous post-synaptic currents and were capable of neurotransmitter synthesis, packaging, and release. Together, the improved induction protocol, combined with an interdisciplinary approach to verify that hMSCs can differentiate into neuronal cells, provides a step toward translational application with models of regenerative medicine.