Astrocyte-like cells differentiated from a novel population of CD45-positive cells in adult human peripheral blood.

We have previously reported a novel CD45-positive cell population called peripheral blood insulin-producing cells (PB-IPCs) and its unique potential for releasing insulin in vitro. Despite the CD45-positive phenotype and self-renewal ability, PB-IPCs are distinguished from hemopoietic and endothelial progenitor cells (EPCs) by some characteristics, such as a CD34-negative phenotype and different culture conditions. We have further identified the gene profiles of the embryonic and neural stem cells, and these profiles include Sox2, Nanog, c-Myc, Klf4, Notch1 and Mash1. After treatment with all-trans retinoic acid (ATRA) in vitro, most PB-IPCs exhibited morphological changes that included the development of elongated and branched cell processes. In the process of induction, the mRNA expression of Hes1 was robustly upregulated, and a majority of cells acquired some astrocyte-associated specific phenotypes including anti-glial fibrillary acidic protein (GFAP), CD44, Glutamate-aspartate transporter (GLAST) and S100ß. In spite of the deficiency of glutamate uptaking, the differentiated cells significantly relaxed the regulation of the expression of brain-derived neurotrophic factor (BDNF) mRNA. This finding demonstrates that PB-IPCs could be induced into a population of astrocyte-like cells and enhanced the neurotrophic potential when the state of proliferation was limited by ATRA, which implies that this unique CD45+ cell pool may have a protective role in some degenerative diseases of the central nervous system (CNS).

Human cord blood-derived multipotent stem cells (CB-SCs) treated with all-trans-retinoic acid (ATRA) give rise to dopamine neurons.

Parkinson's disease (PD) results from the chronic degeneration of dopaminergic neurons. A replacement for these neurons has the potential to provide a clinical cure and/or lasting treatment for symptoms of the disease. Human cord blood-derived multipotent stem cells (CB-SCs) display embryonic stem cell characteristics, including multi-potential differentiation. To explore their therapeutic potential in PD, we examined whether CB-SCs could be induced to differentiate into dopamine neurons in the presence of all-trans retinoic acid (ATRA). Prior to treatment, CB-SCs expressed mRNA and protein for the key dopaminergic transcription factors Nurr1, Wnt1, and En1. Following treatment with 10 µM ATRA for 12 days, CB-SCs displayed elongated neuronal-like morphologies. Immunocytochemistry revealed that 48 ± 11% of ATRA-treated cells were positive for tyrosine hydroxylase (TH), and 36 ± 9% of cells were positive for dopamine transporter (DAT). In contrast, control CB-SCs (culture medium only) expressed only background levels of TH and DAT. Finally, ATRA-treated CB-SCs challenged with potassium released increased levels of dopamine compared to control. These data demonstrate that ATRA induces differentiation of CB-SCs into dopaminergic neurons. This finding may lead to the development of an alternative approach to stem cell therapy for Parkinson's disease.