Isolation and intracerebral grafting of nontransformed multipotential embryonic human CNS stem cells

In this work, we show that the embryonic human brain contains multipotent c entral nervous system (CNS) stem cells, which may provide a continuous, sta ndardized source of human neurons that could virtually eliminate the use of primary human fetal brain tissue for intracerebral transplantation. Multip otential stem cells can be isolated from the developing human CNS in a repr oducible fashion and can be exponentially expanded for longer than 2 years. This allows for the establishment of continuous, nontransformed neural cel l lines, which can be frozen and banked. By clonal analysis, reverse transc ription polymerase chain reaction, and electrophysiological assay, we found that over such long-term culturing these cells retain both multipotentiali ty and an unchanged capacity for the generation of neuronal cells, and that they can be induced to differentiate into catechlaminergic neurons. Finall y, when transplanted into the brain of adult rodents immunosuppressed by cy closporin A, human CNS stem cells migrate away from the site of injection a nd differentiate into neurons and astrocytes. No tumor formation was ever o bserved. Aside from depending on scarce human neural fetal tissue, the use of human embryonic CNS stem cells for clinical neural transplantation shoul d provide a reliable solution to some of the major problems that pertain to this field, and should allow determination of the safety characteristics o f the donor cells in terms of tumorigenicity, viability, sterility, and ant igenic compatibility far in advance of the scheduled day of surgery.