Dopaminergic neurons generated from monkey embryonic stem cells function in a Parkinson primate model.

Parkinson disease (PD) is a neurodegenerative disorder characterized by loss of midbrain dopaminergic (DA) neurons. ES cells are currently the most promising donor cell source for cell-replacement therapy in PD. We previously described a strong neuralizing activity present on the surface of stromal cells, named stromal cell-derived inducing activity (SDIA). In this study, we generated neurospheres composed of neural progenitors from monkey ES cells, which are capable of producing large numbers of DA neurons. We demonstrated that FGF20, preferentially expressed in the substantia nigra, acts synergistically with FGF2 to increase the number of DA neurons in ES cell-derived neurospheres. We also analyzed the effect of transplantation of DA neurons generated from monkey ES cells into 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated (MPTP-treated) monkeys, a primate model for PD. Behavioral studies and functional imaging revealed that the transplanted cells functioned as DA neurons and attenuated MPTP-induced neurological symptoms.

Estrogen promotes differentiation and survival of dopaminergic neurons derived from human neural stem cells.

To investigate the effect of estrogen on neuronal differentiation, especially on dopaminergic (DA) neurons, human neural stem cells (NSCs) were differentiated in the presence of 17beta-estradiol. NSCs gave rise to tyrosine hydroxylase (TH)-positive neurons in vitro, the proportion of which was increased by 17beta-estradiol. Increase in TH-positive neurons was abrogated by an estrogen receptor (ER) antagonist, ICI182780, suggesting ERs play a role in differentiation of DA neurons. The observation that ERs were expressed in both proliferating NSCs and postmitotic DA neurons suggested that increase in TH-positive neurons was due to induction and support of DA neurons. 17beta-Estradiol also increased the number of DA neurons derived from human NSCs in vivo when the cells were grafted into mouse brains. These results support a possible role for estrogen in the transplantation of NSCs for Parkinson's disease.

Neural precursor cells derived from human embryonic brain retain regional specificity.

Recent studies have revealed that neural precursor cells can be expanded not only from the subventricular zone and hippocampus but also from other regions of the human embryonic brain. To determine the regional differences of these precursor cells, we divided the brain of a 9-week-old human embryo into four parts, i.e., telencephalon, diencephalon, mesencephalon, and rhombencephalon. All cultures of the tissues yielded neurospheres, and these spheres gave rise to neurons, astrocytes, and oligodendrocytes. An analysis of clonal populations revealed that these precursor cells were multipotent, and two region-specific differences in neural precursor cells were revealed: 1) The precursor cells from the rostral part of the brain tended to proliferate faster than those from the caudal part, and 2) the precursor cells from the diencephalon and mesencephalon gave rise to more tyrosine hydoxylase (TH)-positive neurons than those from the telencephalon and rhombencephalon. When 50-day-cultured spheres were caused to differentiate, the percentage of TH-positive cells per total cell population was 1.2% for diencephalic and mesencephalic precursors, whereas it was 0.4% for telencephalic and rhombencephalic ones. Furthermore, the TH-positive cells from diencephalic and mesencephalic precursors were large, multipolar, and gamma-aminobutyric acid (GABA)-negative, which suggested that these cells were midbrain dopaminergic neurons. In contrast, TH-positive cells from telencephalic and rhombencephalic precursors were small, bipolar, and GABA-positive. These results suggest that human neural precursor cells might have the potential to differentiate into a variety of cells but retain regional specificity.