Stem-cell therapies for brain more complicated than thought

Nov 27, 2007

An MIT research team’s latest finding suggests that stem cell therapies for the brain could be much more complicated than previously thought.

In a study published in the Public Library of Science (PloS) Biology on Nov. 13, MIT scientists report that adult stem cells produced in the brain are pre-programmed to make only certain kinds of connections—making it impossible for a neural stem cell originating in the brain to be transplanted to the spinal cord, for instance, to take over functions for damaged cells.

Some researchers hope to use adult stem cells produced in the brain to replace neurons lost to damage and diseases such as Alzheimer’s. The new study calls this into question.

“It is wishful thinking to hope that adult stem cells will be able to modify themselves so that they can become other types of neurons lost to injury or disease,“ said Carlos E. Lois, assistant professor of neuroscience in MIT’s Picower Institute for Leaning and Memory.

In developing embryos, stem cells give rise to all the different types of cells that make up the body--skin, muscle, nerve, brain, blood and more. Some of these stem cells persist in adults and give rise to new skin cells, stomach lining cells, etc. The idea behind stem-cell therapy is to use these cells to repair tissue or organs ravaged by disease.

To realize this potential, the stem cells have to be “instructed” to become liver cells, heart cells or neurons. The MIT study, which looked only at adult neural stem cells, suggests it will be necessary to learn how to program any kind of stem cell—embryonic, adult or those derived through other means—to produce specific types of functioning neurons. Without this special set of instructions, a young neuron will only connect with the partners for which it was pre-programmed.

The adult brain harbors its own population of stem cells that spawn new neurons for life. The MIT study shows that a neural stem cell is irreversibly committed to produce only one type of neuron with a pre-set pattern of connections. This means that a given neuronal stem cell can have only limited use in replacement therapy.

“A stem cell that produces neurons that could be useful to replace neurons in the cerebral cortex (the type of neurons lost in Alzheimer's disease) will be most likely useless to replace neurons lost in the spinal cord,” said Lois, who also holds an appointment in MIT’s Department of Brain and Cognitive Sciences. “Moreover, because there are many different types of neurons in the cerebral cortex, it is likely that we will have to figure out how to program stem cells to become many different types of neurons, each of them with a different set of pre-specified connections.”

“In the stem cell field, it is generally thought that the main limitation to achieve brain repair is simply for the new neurons to reach a given brain region and to ensure their survival. Once there, it has been assumed that stem cells will ‘know what to do’ and will become the type of neuron that is missing. It seems that is not the case at all. Our experiments indicate that things are much more complicated,” Lois said.

Lois and colleagues from MIT’s departments of Brain and Cognitive Sciences and Biology found that the stem cells give rise to neurons that become a very specific neuronal type that is already pre-specified to make a very defined set of connections and not others.

Even if the stem cells are transplanted to other parts of the brain, they do not change the type of connections they are programmed to make.

“This suggests that we will have to know much more about the different types of neuronal stem cells, and to identify the characteristic features of their progeny,” Lois said. “We may need to have access to many different types of ‘tailored’ stem cells that give rise to many different types of neurons with specific connections. In addition, we may need a combination of several of these tailored stem cells to eventually be able to replace the different types of neurons lost in a given brain region.

Source: Massachusetts Institute of Technology

Explore further: Rare albino sparrow spotted in Australia

Related Stories

Printing 3-D graphene structures for tissue engineering

May 19, 2015

Ever since single-layer graphene burst onto the science scene in 2004, the possibilities for the promising material have seemed nearly endless. With its high electrical conductivity, ability to store energy, ...

Training pig skin cells for neural development

May 01, 2015

A pig's skin cells may hold the key to new treatments and cures for devastating human neurological diseases. Researchers from the University of Georgia's Regenerative Bioscience Center have discovered a process ...

Recommended for you

11 new species come to light in Madagascar

1 hour ago

Madagascar is home to extraordinary biodiversity, but in the past few decades, the island's forests and associated biodiversity have been under greater attack than ever. Rapid deforestation is affecting the ...

Birds 'weigh' peanuts and choose heavier ones

May 23, 2015

Many animals feed on seeds, acorns or nuts. The common feature of these are that they have shells and there is no direct way to know what's inside. How do the animals know how much and what quality of food ...

Q&A: Why are antibiotics used in livestock?

May 22, 2015

Wal-Mart, the world's biggest retailer, is the latest company to ask its suppliers to curb the use of antibiotics in farm animals. Here's a rundown of what's driving the decision: ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.