Here's the reference:
Functional engraftment of human ES cell–derived dopaminergic neurons enriched by coculture with telomerase-immortalized midbrain astrocytes
Neeta S Roy, Carine Cleren, Shashi K Singh, Lichuan Yang, M Flint Beal & Steven A Goldman. Nature Medicine. Published online: 22 October 2006 (
http://www.nature.com/nm/journal/vaop/ncurrent/full/nm1... but like I said ... you won't get more than the abstract).
But here's the abstract:
To direct human embryonic stem (HES) cells to a dopaminergic neuronal fate, we cocultured HES cells that were exposed to both sonic hedgehog and fibroblast growth factor 8 with telomerase-immortalized human fetal midbrain astrocytes. These astrocytes substantially potentiated dopaminergic neurogenesis by both WA09 and WA01 HES cells, biasing them to the A9 nigrostriatal phenotype. When transplanted into the neostriata of 6-hydroxydopamine–lesioned parkinsonian rats, the dopaminergic implants yielded a significant, substantial and long-lasting restitution of motor function. However, although rich in donor-derived tyrosine hydroxylase–expressing neurons, the grafts exhibited expanding cores of undifferentiated mitotic neuroepithelial cells, which can be tumorigenic. These results show the utility of recreating the cellular environment of the developing human midbrain while driving dopaminergic neurogenesis from HES cells, and they demonstrate the potential of the resultant cells to mediate substantial functional recovery in a model of Parkinson disease. Yet these data also mandate caution in the clinical application of HES cell–derived grafts, given their potential for phenotypic instability and undifferentiated expansion.
Relevant sentences (from a couple of different places, completely stripped of context):
... Although we noted no evidence of either histological anaplasia or persistent antigenically defined undifferentiated ES cells in these grafts, and even though their mitotic indices appeared relatively low as defined both by histone-H3 and BrdU immunolabeling, their persistent, uncontrolled and grossly homogeneous expansion over a 10-week span before the animals were killed nonetheless suggested graft-associated tumorigenesis....
... The expansion of undifferentiated neural precursors after host engraftment, despite otherwise compelling therapeutic benefit, poses a strong cautionary note for the use of unpurified neural derivatives in clinical transplantation. At present, we have no data to indicate whether those undifferentiated cells persisting beyond our 10-week survival point would eventually differentiate and exit the cell cycle, or whether they would instead continue to divide either autonomously or with minimal restraint, ultimately leading to tumor formation....
Key word: Caution. They're suspicious that things might go wrong, but they didn't give the critters time to show conclusively one way or the other. Note that Cornell and U. Rochester usually do good work.
On edit: Not my field, so I don't know if the cell lines identified are old (the *-approved cell lines) or not; they've been criticized by some for being unstable, without evidence cited (to my knowledge) that they were unique in this regard. Funding in one lab (Rochester) was ultimately from NIH and the Michael J. Fox Foundation; in the other, the DoD and MJF Foundation. A corporation provided one of the cell lines, used solely in the DoD/MJF-supported lab (did *'s limitation include the DoD?).
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