Transplanted cells from biotech company detoxify poisoned brains, at least for awhile
Some brains literally poison themselves. In the disease known as infantile neuronal ceroid lipofuscinosis, or Batten disease, brain cells lack the enzyme necessary to clear away their by-products. Clinical symptoms of congenital forms of the disease include seizures, cognitive and motor decline, blindness and early death. The Palo Alto, California–based company StemCells Inc. is conducting clinical trials to see whether cell therapy can ameliorate the disease. The rationale is that the functioning enzyme made by transplanted cells can help patients' defective ones. Work in Cell Stem Cell shows that the transplanted cells do indeed make and secrete the enzyme and that the transplantation delays the loss of motor coordination for a week or so in a mouse model of the disease1.
Previous, unrelated research had indicated that the transplantation strategy could delay onset of a similar malady called Sandhoff disease for a month and prolong lifespan by six weeks2. However, this had not been demonstrated for lipofuscinosis or for the human neural stem cell product the company has developed. In the Cell Stem Cell paper, a team of scientists led by Nobuko Uchida of StemCells showed that these cells secreted a functioning lysosomal enzyme called palmitoyl protein thioesterase — the enzyme that patients with Batten disease lack. Then they transplanted these cells into the brains of immunocompromised mice that were also unable to make this enzyme.
Next, the researchers looked at the amount of lipofuscin, the toxin that builds up in patients with Batten disease, in the brains of three mice that received transplants and four that did not. Overall, mice that received transplants had significantly less lipofuscin than the untreated mice — 37% less in the cortex and more than 50% less in the hippocampus. The procedure also seemed to delay certain disease symptoms. Compared with 8 mice that did not receive transplants, the 14 mice that did performed better, on average, on a test measuring motor coordination at 17 and 18 weeks of age. “What's exciting to us is showing that the transplantation had an effect on neurological function, albeit in an animal model,” says StemCells CFO Rodney Young.
Thus, the current work shows encouraging proof of principle that transplanted cells can support endogenous ones. According to the paper, evidence from 3,000 mice has not identified any instances of the transplanted cells causing a tumour. The next steps will be to see whether the cells survive and secrete enzyme long enough to have a clinically meaningful effect.
Tamaki, S. J. et al. Neuroprotection of host cells by human central nervous system stem cells in a mouse model of infantile neuronal ceroid lipofuscinosis. Cell Stem Cell 5, 310–319 (2009).
Lee, J. P. et al. Stem cells act through multiple mechanisms to benefit mice with neurodegenerative metabolic disease. Nature Med. 13, 439–447 (2007).
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Baker, M. Stem cells delay disease onset in mice with neurodegenerative disease. Nat Rep Stem Cells (2009). https://doi.org/10.1038/stemcells.2009.119