Neurons damaged by Parkinson's disease
What's the News: Scientists have reversed Parkinson's disease-like brain damage and motor problems in mice and rats using neurons grown from human embryonic stem cells. The new technique, described online in Nature
earlier this week, brings scientists closer to similar treatments for people with Parkinson's. How the Heck:
The treatment started with stem cells from human embryos, cells with the ability to develop into any type of tissue in the body. By bathing these cells in a chemical mix that mimics what neurons experience during normal development, the research team turned the stem cells into the particular type of cell that Parkinson's slowly kills off: neurons that produce the neurotransmitter dopamine.
The researchers then injected over 100,000 of these newly grown neurons into the brains of mice that had a rodent equivalent of Parkinson's disease: damaged dopamine-producing cells and the resulting difficulties controlling muscle movement. Over the course of three to five months, the transplanted neurons thrived, connecting with surrounding brain cells, and the mice's motor function greatly improved. When the team repeated the experiment in rats, the result was the same: A few months later, the stem cell-derived neurons had integrated into the brain and the rats were moving around just fine.
This technique produced enough neurons that the researchers were able to inject two rhesus monkeys with Parkinson's-like damage with 7 million new dopamine-producing brain cells each, far closer to the number a human patient would need. A month later, the transplanted neurons were alive and well in the monkeys' brains---though it was too early to tell whether the new neurons would restore normal movement.
What's the Context:
Current treatments for Parkinson's disease---dopamine-boosting drugs and, in some hard to treat cases, electrodes implanted deep in the brain---often don't fully treat the movement problems that come with the disease, and tend to become less effective over time. What's more, medication doesn't do anything to address the neurological root of the disease by replacing or repairing dopamine-producing neurons.
Scientists have previously turned embryonic stem cells into dopamine-making neurons using other techniques, but those cells didn't treat Parkinson's symptoms in animals---and sometimes caused tumor-like growths in the animals' brains. This study shows that even tiny tweaks to the method of turning stem cells into particular tissues can have a huge impact on how well those cells function in the body.
The Future Holds:
Since the ultimate goal is, of course, to develop treatments for human patients, the researchers are now working to produce the neurons in a clinical-caliber, large-scale facility, and to conduct further safety and efficacy studies in animals. The treatment could be ready for clinical trials in three or four years, if all goes well.
Reference: Sonja Kriks et al. "Dopamine neurons derived from human ES cells efficiently engraft in animal models of Parkinson’s disease." Nature, published online November 6, 2011. DOI:10.1038/nature10648
Image courtesy of Jenflorian / Wikimedia Commons