Specification of a Dopaminergic Phenotype from Adult Human Mesenchymal Stem Cells

¹ Graduate School of Biomedical Sciences, Department of Medicine Hematology/Oncology, University of Medicine and Dentistry of New Jersey – New Jersey Medical School, 185 South Orange Avenue, Newark, New Jersey, USA.
² Department of Pharmacology Physiology
³ Department of Medicine Hematology/Oncology, University of Medicine and Dentistry of New Jersey – New Jersey Medical School, 185 South Orange Avenue, Newark, New Jersey, USA.

^* To whom correspondence should be addressed. E-mail: rameshwa{at}umdnj.edu.

	Abstract

Dopamine (DA) neurons derived from stem cells are a valuable source for cell replacement therapy in Parkinson's disease (PD), to study the molecular mechanisms of DA neuron development, and for screening pharmaceutical compounds that target DA disorders. Compared to other stem cells, mesenchymal stem cells (MSCs) derived from the adult human bone marrow (BM) have significant advantages and greater potential for immediate clinical application. We report the identification of in vitro conditions for inducing adult human MSCs into DA cells. Using a cocktail that includes sonic hedgehog (SHH) and fibroblast growth factors (FGF8 and bFGF), human BM-derived MSCs were induced in vitro to become DA cells in 12 days. Based on tyrosine hydroxylase (TH) expression, the efficiency of induction was determined to be 67%. The cells develop a neuronal morphology expressing the neuronal markers NeuN and III tubulin, but not glial markers, GFAP and Olig2. As the cells acquire a post-mitotic neuronal fate, they down-regulate cell cycle activator proteins cyclin B, cdk2 and PCNA. Molecular characterization revealed the expression of DA specific genes such as TH, Pitx3, Nurr1, DAT and VMAT2. The induced MSCs also synthesize and secrete DA in a depolarization-independent manner. The latter observation is consistent with the low expression of voltage gated Na⁺ and Ca²⁺ channels in the induced MSCs and suggests that the cells are at an immature stage of development likely representing DA neuronal progenitors. Taken together, the results demonstrate the ability of adult human BM-derived MSCs to form DA cells in vitro.